1 /*
2 * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
4 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
5 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 *
7 * This code is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 only, as
9 * published by the Free Software Foundation.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27 #include "precompiled.hpp"
28 #include "memory/allocation.hpp"
29 #include "memory/universe.hpp"
30
31 #include "gc/shared/gcArguments.hpp"
32 #include "gc/shared/gcTimer.hpp"
33 #include "gc/shared/gcTraceTime.inline.hpp"
34 #include "gc/shared/locationPrinter.inline.hpp"
35 #include "gc/shared/memAllocator.hpp"
36 #include "gc/shared/plab.hpp"
37 #include "gc/shared/tlab_globals.hpp"
38
39 #include "gc/shenandoah/shenandoahAgeCensus.hpp"
40 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
41 #include "gc/shenandoah/heuristics/shenandoahYoungHeuristics.hpp"
42 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
43 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
44 #include "gc/shenandoah/shenandoahCardTable.hpp"
45 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
46 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
47 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
48 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
49 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
50 #include "gc/shenandoah/shenandoahControlThread.hpp"
51 #include "gc/shenandoah/shenandoahRegulatorThread.hpp"
52 #include "gc/shenandoah/shenandoahFreeSet.hpp"
53 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
54 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
55 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
56 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
57 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
58 #include "gc/shenandoah/shenandoahInitLogger.hpp"
59 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
60 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
61 #include "gc/shenandoah/shenandoahMetrics.hpp"
62 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
63 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
64 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
65 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
66 #include "gc/shenandoah/shenandoahPadding.hpp"
67 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
68 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
69 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
70 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
71 #include "gc/shenandoah/shenandoahSTWMark.hpp"
72 #include "gc/shenandoah/shenandoahUtils.hpp"
73 #include "gc/shenandoah/shenandoahVerifier.hpp"
74 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
75 #include "gc/shenandoah/shenandoahVMOperations.hpp"
76 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
77 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
78 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
79 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
80 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
81 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
82 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
83 #include "utilities/globalDefinitions.hpp"
84
85 #if INCLUDE_JFR
86 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
87 #endif
88
89 #include "classfile/systemDictionary.hpp"
90 #include "code/codeCache.hpp"
91 #include "memory/classLoaderMetaspace.hpp"
92 #include "memory/metaspaceUtils.hpp"
93 #include "oops/compressedOops.inline.hpp"
94 #include "prims/jvmtiTagMap.hpp"
95 #include "runtime/atomic.hpp"
96 #include "runtime/globals.hpp"
97 #include "runtime/interfaceSupport.inline.hpp"
98 #include "runtime/java.hpp"
99 #include "runtime/orderAccess.hpp"
100 #include "runtime/safepointMechanism.hpp"
101 #include "runtime/vmThread.hpp"
102 #include "services/mallocTracker.hpp"
103 #include "services/memTracker.hpp"
104 #include "utilities/events.hpp"
105 #include "utilities/powerOfTwo.hpp"
106
107 class ShenandoahPretouchHeapTask : public WorkerTask {
108 private:
109 ShenandoahRegionIterator _regions;
110 const size_t _page_size;
111 public:
112 ShenandoahPretouchHeapTask(size_t page_size) :
113 WorkerTask("Shenandoah Pretouch Heap"),
114 _page_size(page_size) {}
115
116 virtual void work(uint worker_id) {
117 ShenandoahHeapRegion* r = _regions.next();
118 while (r != nullptr) {
119 if (r->is_committed()) {
120 os::pretouch_memory(r->bottom(), r->end(), _page_size);
121 }
122 r = _regions.next();
123 }
124 }
125 };
126
127 class ShenandoahPretouchBitmapTask : public WorkerTask {
128 private:
129 ShenandoahRegionIterator _regions;
130 char* _bitmap_base;
131 const size_t _bitmap_size;
132 const size_t _page_size;
133 public:
134 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
135 WorkerTask("Shenandoah Pretouch Bitmap"),
136 _bitmap_base(bitmap_base),
137 _bitmap_size(bitmap_size),
138 _page_size(page_size) {}
139
140 virtual void work(uint worker_id) {
141 ShenandoahHeapRegion* r = _regions.next();
142 while (r != nullptr) {
143 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
144 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
145 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
146
147 if (r->is_committed()) {
148 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
149 }
150
151 r = _regions.next();
152 }
153 }
154 };
155
156 jint ShenandoahHeap::initialize() {
157 //
158 // Figure out heap sizing
159 //
160
161 size_t init_byte_size = InitialHeapSize;
162 size_t min_byte_size = MinHeapSize;
163 size_t max_byte_size = MaxHeapSize;
164 size_t heap_alignment = HeapAlignment;
165
166 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
167
168 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
169 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
170
171 _num_regions = ShenandoahHeapRegion::region_count();
172 assert(_num_regions == (max_byte_size / reg_size_bytes),
173 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
174 _num_regions, max_byte_size, reg_size_bytes);
175
176 size_t num_committed_regions = init_byte_size / reg_size_bytes;
177 num_committed_regions = MIN2(num_committed_regions, _num_regions);
178 assert(num_committed_regions <= _num_regions, "sanity");
179 _initial_size = num_committed_regions * reg_size_bytes;
180
181 size_t num_min_regions = min_byte_size / reg_size_bytes;
182 num_min_regions = MIN2(num_min_regions, _num_regions);
183 assert(num_min_regions <= _num_regions, "sanity");
184 _minimum_size = num_min_regions * reg_size_bytes;
185
186 // Default to max heap size.
187 _soft_max_size = _num_regions * reg_size_bytes;
188
189 _committed = _initial_size;
190
191 // Now we know the number of regions and heap sizes, initialize the heuristics.
192 initialize_heuristics_generations();
193
194 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
195 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
196 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
197
198 //
199 // Reserve and commit memory for heap
200 //
201
202 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
203 initialize_reserved_region(heap_rs);
204 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
205 _heap_region_special = heap_rs.special();
206
207 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
208 "Misaligned heap: " PTR_FORMAT, p2i(base()));
209 os::trace_page_sizes_for_requested_size("Heap",
210 max_byte_size, heap_alignment,
211 heap_rs.base(),
212 heap_rs.size(), heap_rs.page_size());
213
214 #if SHENANDOAH_OPTIMIZED_MARKTASK
215 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
216 // Fail if we ever attempt to address more than we can.
217 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
218 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
219 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
220 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
221 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
222 vm_exit_during_initialization("Fatal Error", buf);
223 }
224 #endif
225
226 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
227 if (!_heap_region_special) {
228 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
229 "Cannot commit heap memory");
230 }
231
232 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
233
234 //
235 // After reserving the Java heap, create the card table, barriers, and workers, in dependency order
236 //
237 if (mode()->is_generational()) {
238 ShenandoahDirectCardMarkRememberedSet *rs;
239 ShenandoahCardTable* card_table = ShenandoahBarrierSet::barrier_set()->card_table();
240 size_t card_count = card_table->cards_required(heap_rs.size() / HeapWordSize);
241 rs = new ShenandoahDirectCardMarkRememberedSet(ShenandoahBarrierSet::barrier_set()->card_table(), card_count);
242 _card_scan = new ShenandoahScanRemembered<ShenandoahDirectCardMarkRememberedSet>(rs);
243
244 // Age census structure
245 _age_census = new ShenandoahAgeCensus();
246 }
247
248 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
249 if (_workers == nullptr) {
250 vm_exit_during_initialization("Failed necessary allocation.");
251 } else {
252 _workers->initialize_workers();
253 }
254
255 if (ParallelGCThreads > 1) {
256 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
257 _safepoint_workers->initialize_workers();
258 }
259
260 //
261 // Reserve and commit memory for bitmap(s)
262 //
263
264 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
265 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
266
267 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
268
269 guarantee(bitmap_bytes_per_region != 0,
270 "Bitmap bytes per region should not be zero");
271 guarantee(is_power_of_2(bitmap_bytes_per_region),
272 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
273
274 if (bitmap_page_size > bitmap_bytes_per_region) {
275 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
276 _bitmap_bytes_per_slice = bitmap_page_size;
277 } else {
278 _bitmap_regions_per_slice = 1;
279 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
280 }
281
282 guarantee(_bitmap_regions_per_slice >= 1,
283 "Should have at least one region per slice: " SIZE_FORMAT,
284 _bitmap_regions_per_slice);
285
286 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
287 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
288 _bitmap_bytes_per_slice, bitmap_page_size);
289
290 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
291 os::trace_page_sizes_for_requested_size("Mark Bitmap",
292 bitmap_size_orig, bitmap_page_size,
293 bitmap.base(),
294 bitmap.size(), bitmap.page_size());
295 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
296 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
297 _bitmap_region_special = bitmap.special();
298
299 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
300 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
301 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
302 if (!_bitmap_region_special) {
303 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
304 "Cannot commit bitmap memory");
305 }
306
307 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
308
309 if (ShenandoahVerify) {
310 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
311 os::trace_page_sizes_for_requested_size("Verify Bitmap",
312 bitmap_size_orig, bitmap_page_size,
313 verify_bitmap.base(),
314 verify_bitmap.size(), verify_bitmap.page_size());
315 if (!verify_bitmap.special()) {
316 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
317 "Cannot commit verification bitmap memory");
318 }
319 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
320 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
321 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
322 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
323 }
324
325 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
326 size_t aux_bitmap_page_size = bitmap_page_size;
327 #ifdef LINUX
328 // In THP "advise" mode, we refrain from advising the system to use large pages
329 // since we know these commits will be short lived, and there is no reason to trash
330 // the THP area with this bitmap.
331 if (UseTransparentHugePages) {
332 aux_bitmap_page_size = os::vm_page_size();
333 }
334 #endif
335 ReservedSpace aux_bitmap(_bitmap_size, aux_bitmap_page_size);
336 os::trace_page_sizes_for_requested_size("Aux Bitmap",
337 bitmap_size_orig, aux_bitmap_page_size,
338 aux_bitmap.base(),
339 aux_bitmap.size(), aux_bitmap.page_size());
340 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
341 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
342 _aux_bitmap_region_special = aux_bitmap.special();
343 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
344
345 //
346 // Create regions and region sets
347 //
348 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
349 size_t region_storage_size_orig = region_align * _num_regions;
350 size_t region_storage_size = align_up(region_storage_size_orig,
351 MAX2(region_page_size, os::vm_allocation_granularity()));
352
353 ReservedSpace region_storage(region_storage_size, region_page_size);
354 os::trace_page_sizes_for_requested_size("Region Storage",
355 region_storage_size_orig, region_page_size,
356 region_storage.base(),
357 region_storage.size(), region_storage.page_size());
358 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
359 if (!region_storage.special()) {
360 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
361 "Cannot commit region memory");
362 }
363
364 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
365 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
366 // If not successful, bite a bullet and allocate at whatever address.
367 {
368 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
369 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
370 const size_t cset_page_size = os::vm_page_size();
371
372 uintptr_t min = round_up_power_of_2(cset_align);
373 uintptr_t max = (1u << 30u);
374 ReservedSpace cset_rs;
375
376 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
377 char* req_addr = (char*)addr;
378 assert(is_aligned(req_addr, cset_align), "Should be aligned");
379 cset_rs = ReservedSpace(cset_size, cset_align, cset_page_size, req_addr);
380 if (cset_rs.is_reserved()) {
381 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
382 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
383 break;
384 }
385 }
386
387 if (_collection_set == nullptr) {
388 cset_rs = ReservedSpace(cset_size, cset_align, os::vm_page_size());
389 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
390 }
391 os::trace_page_sizes_for_requested_size("Collection Set",
392 cset_size, cset_page_size,
393 cset_rs.base(),
394 cset_rs.size(), cset_rs.page_size());
395 }
396
397 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
398 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
399 _free_set = new ShenandoahFreeSet(this, _num_regions);
400
401 {
402 ShenandoahHeapLocker locker(lock());
403
404
405 for (size_t i = 0; i < _num_regions; i++) {
406 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
407 bool is_committed = i < num_committed_regions;
408 void* loc = region_storage.base() + i * region_align;
409
410 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
411 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
412
413 _marking_context->initialize_top_at_mark_start(r);
414 _regions[i] = r;
415 assert(!collection_set()->is_in(i), "New region should not be in collection set");
416
417 _affiliations[i] = ShenandoahAffiliation::FREE;
418 }
419
420 // Initialize to complete
421 _marking_context->mark_complete();
422 size_t young_cset_regions, old_cset_regions;
423
424 // We are initializing free set. We ignore cset region tallies.
425 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions);
426 _free_set->rebuild(young_cset_regions, old_cset_regions);
427 }
428
429 if (AlwaysPreTouch) {
430 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
431 // before initialize() below zeroes it with initializing thread. For any given region,
432 // we touch the region and the corresponding bitmaps from the same thread.
433 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
434
435 _pretouch_heap_page_size = heap_page_size;
436 _pretouch_bitmap_page_size = bitmap_page_size;
437
438 #ifdef LINUX
439 // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
440 // pages. But, the kernel needs to know that every small page is used, in order to coalesce
441 // them into huge one. Therefore, we need to pretouch with smaller pages.
442 if (UseTransparentHugePages) {
443 _pretouch_heap_page_size = (size_t)os::vm_page_size();
444 _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
445 }
446 #endif
447
448 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
449 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
450
451 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
452 _workers->run_task(&bcl);
453
454 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
455 _workers->run_task(&hcl);
456 }
457
458 //
459 // Initialize the rest of GC subsystems
460 //
461
462 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
463 for (uint worker = 0; worker < _max_workers; worker++) {
464 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
465 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
466 }
467
468 // There should probably be Shenandoah-specific options for these,
469 // just as there are G1-specific options.
470 {
471 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
472 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
473 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
474 }
475
476 _monitoring_support = new ShenandoahMonitoringSupport(this);
477 _phase_timings = new ShenandoahPhaseTimings(max_workers());
478 ShenandoahCodeRoots::initialize();
479
480 if (ShenandoahPacing) {
481 _pacer = new ShenandoahPacer(this);
482 _pacer->setup_for_idle();
483 } else {
484 _pacer = nullptr;
485 }
486
487 _control_thread = new ShenandoahControlThread();
488 _regulator_thread = new ShenandoahRegulatorThread(_control_thread);
489
490 print_init_logger();
491
492 return JNI_OK;
493 }
494
495 void ShenandoahHeap::print_init_logger() const {
496 ShenandoahInitLogger::print();
497 }
498
499 size_t ShenandoahHeap::max_size_for(ShenandoahGeneration* generation) const {
500 switch (generation->type()) {
501 case YOUNG:
502 return _generation_sizer.max_young_size();
503 case OLD:
504 return max_capacity() - _generation_sizer.min_young_size();
505 case GLOBAL_GEN:
506 case GLOBAL_NON_GEN:
507 return max_capacity();
508 default:
509 ShouldNotReachHere();
510 return 0;
511 }
512 }
513
514 size_t ShenandoahHeap::min_size_for(ShenandoahGeneration* generation) const {
515 switch (generation->type()) {
516 case YOUNG:
517 return _generation_sizer.min_young_size();
518 case OLD:
519 return max_capacity() - _generation_sizer.max_young_size();
520 case GLOBAL_GEN:
521 case GLOBAL_NON_GEN:
522 return min_capacity();
523 default:
524 ShouldNotReachHere();
525 return 0;
526 }
527 }
528
529 void ShenandoahHeap::initialize_heuristics_generations() {
530 if (ShenandoahGCMode != nullptr) {
531 if (strcmp(ShenandoahGCMode, "satb") == 0) {
532 _gc_mode = new ShenandoahSATBMode();
533 } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
534 _gc_mode = new ShenandoahIUMode();
535 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
536 _gc_mode = new ShenandoahPassiveMode();
537 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
538 _gc_mode = new ShenandoahGenerationalMode();
539 } else {
540 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
541 }
542 } else {
543 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
544 }
545 _gc_mode->initialize_flags();
546 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
547 vm_exit_during_initialization(
548 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
549 _gc_mode->name()));
550 }
551 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
552 vm_exit_during_initialization(
553 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
554 _gc_mode->name()));
555 }
556
557 // Max capacity is the maximum _allowed_ capacity. That is, the maximum allowed capacity
558 // for old would be total heap - minimum capacity of young. This means the sum of the maximum
559 // allowed for old and young could exceed the total heap size. It remains the case that the
560 // _actual_ capacity of young + old = total.
561 _generation_sizer.heap_size_changed(max_capacity());
562 size_t initial_capacity_young = _generation_sizer.max_young_size();
563 size_t max_capacity_young = _generation_sizer.max_young_size();
564 size_t initial_capacity_old = max_capacity() - max_capacity_young;
565 size_t max_capacity_old = max_capacity() - initial_capacity_young;
566
567 _young_generation = new ShenandoahYoungGeneration(_max_workers, max_capacity_young, initial_capacity_young);
568 _old_generation = new ShenandoahOldGeneration(_max_workers, max_capacity_old, initial_capacity_old);
569 _global_generation = new ShenandoahGlobalGeneration(_gc_mode->is_generational(), _max_workers, max_capacity(), max_capacity());
570 _global_generation->initialize_heuristics(_gc_mode);
571 if (mode()->is_generational()) {
572 _young_generation->initialize_heuristics(_gc_mode);
573 _old_generation->initialize_heuristics(_gc_mode);
574 }
575 _evac_tracker = new ShenandoahEvacuationTracker(mode()->is_generational());
576 }
577
578 #ifdef _MSC_VER
579 #pragma warning( push )
580 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
581 #endif
582
583 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
584 CollectedHeap(),
585 _gc_generation(nullptr),
586 _prepare_for_old_mark(false),
587 _initial_size(0),
588 _promotion_potential(0),
589 _committed(0),
590 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
591 _workers(nullptr),
592 _safepoint_workers(nullptr),
593 _heap_region_special(false),
594 _num_regions(0),
595 _regions(nullptr),
596 _affiliations(nullptr),
597 _update_refs_iterator(this),
598 _promoted_reserve(0),
599 _old_evac_reserve(0),
600 _old_evac_expended(0),
601 _young_evac_reserve(0),
602 _captured_old_usage(0),
603 _previous_promotion(0),
604 _upgraded_to_full(false),
605 _age_census(nullptr),
606 _has_evacuation_reserve_quantities(false),
607 _cancel_requested_time(0),
608 _young_generation(nullptr),
609 _global_generation(nullptr),
610 _old_generation(nullptr),
611 _control_thread(nullptr),
612 _regulator_thread(nullptr),
613 _shenandoah_policy(policy),
614 _free_set(nullptr),
615 _pacer(nullptr),
616 _verifier(nullptr),
617 _phase_timings(nullptr),
618 _evac_tracker(nullptr),
619 _mmu_tracker(),
620 _generation_sizer(&_mmu_tracker),
621 _monitoring_support(nullptr),
622 _memory_pool(nullptr),
623 _young_gen_memory_pool(nullptr),
624 _old_gen_memory_pool(nullptr),
625 _stw_memory_manager("Shenandoah Pauses"),
626 _cycle_memory_manager("Shenandoah Cycles"),
627 _gc_timer(new ConcurrentGCTimer()),
628 _soft_ref_policy(),
629 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
630 _old_regions_surplus(0),
631 _old_regions_deficit(0),
632 _marking_context(nullptr),
633 _bitmap_size(0),
634 _bitmap_regions_per_slice(0),
635 _bitmap_bytes_per_slice(0),
636 _bitmap_region_special(false),
637 _aux_bitmap_region_special(false),
638 _liveness_cache(nullptr),
639 _collection_set(nullptr),
640 _card_scan(nullptr)
641 {
642 }
643
644 #ifdef _MSC_VER
645 #pragma warning( pop )
646 #endif
647
648 void ShenandoahHeap::print_on(outputStream* st) const {
649 st->print_cr("Shenandoah Heap");
650 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
651 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
652 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
653 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
654 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
655 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
656 num_regions(),
657 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
658 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
659
660 st->print("Status: ");
661 if (has_forwarded_objects()) st->print("has forwarded objects, ");
662 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
663 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
664 if (is_evacuation_in_progress()) st->print("evacuating, ");
665 if (is_update_refs_in_progress()) st->print("updating refs, ");
666 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
667 if (is_full_gc_in_progress()) st->print("full gc, ");
668 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
669 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
670 if (is_concurrent_strong_root_in_progress() &&
671 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
672
673 if (cancelled_gc()) {
674 st->print("cancelled");
675 } else {
676 st->print("not cancelled");
677 }
678 st->cr();
679
680 st->print_cr("Reserved region:");
681 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
682 p2i(reserved_region().start()),
683 p2i(reserved_region().end()));
684
685 ShenandoahCollectionSet* cset = collection_set();
686 st->print_cr("Collection set:");
687 if (cset != nullptr) {
688 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
689 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
690 } else {
691 st->print_cr(" (null)");
692 }
693
694 st->cr();
695 MetaspaceUtils::print_on(st);
696
697 if (Verbose) {
698 st->cr();
699 print_heap_regions_on(st);
700 }
701 }
702
703 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
704 public:
705 void do_thread(Thread* thread) {
706 assert(thread != nullptr, "Sanity");
707 assert(thread->is_Worker_thread(), "Only worker thread expected");
708 ShenandoahThreadLocalData::initialize_gclab(thread);
709 }
710 };
711
712 void ShenandoahHeap::post_initialize() {
713 CollectedHeap::post_initialize();
714 _mmu_tracker.initialize();
715
716 MutexLocker ml(Threads_lock);
717
718 ShenandoahInitWorkerGCLABClosure init_gclabs;
719 _workers->threads_do(&init_gclabs);
720
721 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
722 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
723 _workers->set_initialize_gclab();
724 if (_safepoint_workers != nullptr) {
725 _safepoint_workers->threads_do(&init_gclabs);
726 _safepoint_workers->set_initialize_gclab();
727 }
728
729 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
730 }
731
732 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
733 return _global_generation->heuristics();
734 }
735
736 ShenandoahOldHeuristics* ShenandoahHeap::old_heuristics() {
737 return (ShenandoahOldHeuristics*) _old_generation->heuristics();
738 }
739
740 ShenandoahYoungHeuristics* ShenandoahHeap::young_heuristics() {
741 return (ShenandoahYoungHeuristics*) _young_generation->heuristics();
742 }
743
744 bool ShenandoahHeap::doing_mixed_evacuations() {
745 return _old_generation->state() == ShenandoahOldGeneration::WAITING_FOR_EVAC;
746 }
747
748 bool ShenandoahHeap::is_old_bitmap_stable() const {
749 return _old_generation->is_mark_complete();
750 }
751
752 bool ShenandoahHeap::is_gc_generation_young() const {
753 return _gc_generation != nullptr && _gc_generation->is_young();
754 }
755
756 size_t ShenandoahHeap::used() const {
757 return global_generation()->used();
758 }
759
760 size_t ShenandoahHeap::committed() const {
761 return Atomic::load(&_committed);
762 }
763
764 void ShenandoahHeap::increase_committed(size_t bytes) {
765 shenandoah_assert_heaplocked_or_safepoint();
766 _committed += bytes;
767 }
768
769 void ShenandoahHeap::decrease_committed(size_t bytes) {
770 shenandoah_assert_heaplocked_or_safepoint();
771 _committed -= bytes;
772 }
773
774 // For tracking usage based on allocations, it should be the case that:
775 // * The sum of regions::used == heap::used
776 // * The sum of a generation's regions::used == generation::used
777 // * The sum of a generation's humongous regions::free == generation::humongous_waste
778 // These invariants are checked by the verifier on GC safepoints.
779 //
780 // Additional notes:
781 // * When a mutator's allocation request causes a region to be retired, the
782 // free memory left in that region is considered waste. It does not contribute
783 // to the usage, but it _does_ contribute to allocation rate.
784 // * The bottom of a PLAB must be aligned on card size. In some cases this will
785 // require padding in front of the PLAB (a filler object). Because this padding
786 // is included in the region's used memory we include the padding in the usage
787 // accounting as waste.
788 // * Mutator allocations are used to compute an allocation rate. They are also
789 // sent to the Pacer for those purposes.
790 // * There are three sources of waste:
791 // 1. The padding used to align a PLAB on card size
792 // 2. Region's free is less than minimum TLAB size and is retired
793 // 3. The unused portion of memory in the last region of a humongous object
794 void ShenandoahHeap::increase_used(const ShenandoahAllocRequest& req) {
795 size_t actual_bytes = req.actual_size() * HeapWordSize;
796 size_t wasted_bytes = req.waste() * HeapWordSize;
797 ShenandoahGeneration* generation = generation_for(req.affiliation());
798
799 if (req.is_gc_alloc()) {
800 assert(wasted_bytes == 0 || req.type() == ShenandoahAllocRequest::_alloc_plab, "Only PLABs have waste");
801 increase_used(generation, actual_bytes + wasted_bytes);
802 } else {
803 assert(req.is_mutator_alloc(), "Expected mutator alloc here");
804 // padding and actual size both count towards allocation counter
805 generation->increase_allocated(actual_bytes + wasted_bytes);
806
807 // only actual size counts toward usage for mutator allocations
808 increase_used(generation, actual_bytes);
809
810 // notify pacer of both actual size and waste
811 notify_mutator_alloc_words(req.actual_size(), req.waste());
812
813 if (wasted_bytes > 0 && req.actual_size() > ShenandoahHeapRegion::humongous_threshold_words()) {
814 increase_humongous_waste(generation,wasted_bytes);
815 }
816 }
817 }
818
819 void ShenandoahHeap::increase_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
820 generation->increase_humongous_waste(bytes);
821 if (!generation->is_global()) {
822 global_generation()->increase_humongous_waste(bytes);
823 }
824 }
825
826 void ShenandoahHeap::decrease_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
827 generation->decrease_humongous_waste(bytes);
828 if (!generation->is_global()) {
829 global_generation()->decrease_humongous_waste(bytes);
830 }
831 }
832
833 void ShenandoahHeap::increase_used(ShenandoahGeneration* generation, size_t bytes) {
834 generation->increase_used(bytes);
835 if (!generation->is_global()) {
836 global_generation()->increase_used(bytes);
837 }
838 }
839
840 void ShenandoahHeap::decrease_used(ShenandoahGeneration* generation, size_t bytes) {
841 generation->decrease_used(bytes);
842 if (!generation->is_global()) {
843 global_generation()->decrease_used(bytes);
844 }
845 }
846
847 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, size_t waste) {
848 if (ShenandoahPacing) {
849 control_thread()->pacing_notify_alloc(words);
850 if (waste > 0) {
851 pacer()->claim_for_alloc(waste, true);
852 }
853 }
854 }
855
856 size_t ShenandoahHeap::capacity() const {
857 return committed();
858 }
859
860 size_t ShenandoahHeap::max_capacity() const {
861 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
862 }
863
864 size_t ShenandoahHeap::soft_max_capacity() const {
865 size_t v = Atomic::load(&_soft_max_size);
866 assert(min_capacity() <= v && v <= max_capacity(),
867 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
868 min_capacity(), v, max_capacity());
869 return v;
870 }
871
872 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
873 assert(min_capacity() <= v && v <= max_capacity(),
874 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
875 min_capacity(), v, max_capacity());
876 Atomic::store(&_soft_max_size, v);
877 }
878
879 size_t ShenandoahHeap::min_capacity() const {
880 return _minimum_size;
881 }
882
883 size_t ShenandoahHeap::initial_capacity() const {
884 return _initial_size;
885 }
886
887 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
888 assert (ShenandoahUncommit, "should be enabled");
889
890 // Application allocates from the beginning of the heap, and GC allocates at
891 // the end of it. It is more efficient to uncommit from the end, so that applications
892 // could enjoy the near committed regions. GC allocations are much less frequent,
893 // and therefore can accept the committing costs.
894
895 size_t count = 0;
896 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
897 ShenandoahHeapRegion* r = get_region(i - 1);
898 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
899 ShenandoahHeapLocker locker(lock());
900 if (r->is_empty_committed()) {
901 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
902 break;
903 }
904
905 r->make_uncommitted();
906 count++;
907 }
908 }
909 SpinPause(); // allow allocators to take the lock
910 }
911
912 if (count > 0) {
913 control_thread()->notify_heap_changed();
914 regulator_thread()->notify_heap_changed();
915 }
916 }
917
918 void ShenandoahHeap::handle_old_evacuation(HeapWord* obj, size_t words, bool promotion) {
919 // Only register the copy of the object that won the evacuation race.
920 card_scan()->register_object_without_lock(obj);
921
922 // Mark the entire range of the evacuated object as dirty. At next remembered set scan,
923 // we will clear dirty bits that do not hold interesting pointers. It's more efficient to
924 // do this in batch, in a background GC thread than to try to carefully dirty only cards
925 // that hold interesting pointers right now.
926 card_scan()->mark_range_as_dirty(obj, words);
927
928 if (promotion) {
929 // This evacuation was a promotion, track this as allocation against old gen
930 old_generation()->increase_allocated(words * HeapWordSize);
931 }
932 }
933
934 void ShenandoahHeap::handle_old_evacuation_failure() {
935 if (_old_gen_oom_evac.try_set()) {
936 log_info(gc)("Old gen evac failure.");
937 }
938 }
939
940 void ShenandoahHeap::report_promotion_failure(Thread* thread, size_t size) {
941 // We squelch excessive reports to reduce noise in logs.
942 const size_t MaxReportsPerEpoch = 4;
943 static size_t last_report_epoch = 0;
944 static size_t epoch_report_count = 0;
945
946 size_t promotion_reserve;
947 size_t promotion_expended;
948
949 size_t gc_id = control_thread()->get_gc_id();
950
951 if ((gc_id != last_report_epoch) || (epoch_report_count++ < MaxReportsPerEpoch)) {
952 {
953 // Promotion failures should be very rare. Invest in providing useful diagnostic info.
954 ShenandoahHeapLocker locker(lock());
955 promotion_reserve = get_promoted_reserve();
956 promotion_expended = get_promoted_expended();
957 }
958 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
959 size_t words_remaining = (plab == nullptr)? 0: plab->words_remaining();
960 const char* promote_enabled = ShenandoahThreadLocalData::allow_plab_promotions(thread)? "enabled": "disabled";
961 ShenandoahGeneration* old_gen = old_generation();
962 size_t old_capacity = old_gen->max_capacity();
963 size_t old_usage = old_gen->used();
964 size_t old_free_regions = old_gen->free_unaffiliated_regions();
965
966 log_info(gc, ergo)("Promotion failed, size " SIZE_FORMAT ", has plab? %s, PLAB remaining: " SIZE_FORMAT
967 ", plab promotions %s, promotion reserve: " SIZE_FORMAT ", promotion expended: " SIZE_FORMAT
968 ", old capacity: " SIZE_FORMAT ", old_used: " SIZE_FORMAT ", old unaffiliated regions: " SIZE_FORMAT,
969 size * HeapWordSize, plab == nullptr? "no": "yes",
970 words_remaining * HeapWordSize, promote_enabled, promotion_reserve, promotion_expended,
971 old_capacity, old_usage, old_free_regions);
972
973 if ((gc_id == last_report_epoch) && (epoch_report_count >= MaxReportsPerEpoch)) {
974 log_info(gc, ergo)("Squelching additional promotion failure reports for current epoch");
975 } else if (gc_id != last_report_epoch) {
976 last_report_epoch = gc_id;;
977 epoch_report_count = 1;
978 }
979 }
980 }
981
982 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
983 // New object should fit the GCLAB size
984 size_t min_size = MAX2(size, PLAB::min_size());
985
986 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
987 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
988
989 // Limit growth of GCLABs to ShenandoahMaxEvacLABRatio * the minimum size. This enables more equitable distribution of
990 // available evacuation buidget between the many threads that are coordinating in the evacuation effort.
991 if (ShenandoahMaxEvacLABRatio > 0) {
992 log_debug(gc, free)("Allocate new gclab: " SIZE_FORMAT ", " SIZE_FORMAT, new_size, PLAB::min_size() * ShenandoahMaxEvacLABRatio);
993 new_size = MIN2(new_size, PLAB::min_size() * ShenandoahMaxEvacLABRatio);
994 }
995
996 new_size = MIN2(new_size, PLAB::max_size());
997 new_size = MAX2(new_size, PLAB::min_size());
998
999 // Record new heuristic value even if we take any shortcut. This captures
1000 // the case when moderately-sized objects always take a shortcut. At some point,
1001 // heuristics should catch up with them.
1002 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
1003
1004 if (new_size < size) {
1005 // New size still does not fit the object. Fall back to shared allocation.
1006 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
1007 log_debug(gc, free)("New gclab size (" SIZE_FORMAT ") is too small for " SIZE_FORMAT, new_size, size);
1008 return nullptr;
1009 }
1010
1011 // Retire current GCLAB, and allocate a new one.
1012 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1013 gclab->retire();
1014
1015 size_t actual_size = 0;
1016 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
1017 if (gclab_buf == nullptr) {
1018 return nullptr;
1019 }
1020
1021 assert (size <= actual_size, "allocation should fit");
1022
1023 if (ZeroTLAB) {
1024 // ..and clear it.
1025 Copy::zero_to_words(gclab_buf, actual_size);
1026 } else {
1027 // ...and zap just allocated object.
1028 #ifdef ASSERT
1029 // Skip mangling the space corresponding to the object header to
1030 // ensure that the returned space is not considered parsable by
1031 // any concurrent GC thread.
1032 size_t hdr_size = oopDesc::header_size();
1033 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
1034 #endif // ASSERT
1035 }
1036 gclab->set_buf(gclab_buf, actual_size);
1037 return gclab->allocate(size);
1038 }
1039
1040 // Establish a new PLAB and allocate size HeapWords within it.
1041 HeapWord* ShenandoahHeap::allocate_from_plab_slow(Thread* thread, size_t size, bool is_promotion) {
1042 // New object should fit the PLAB size
1043 size_t min_size = MAX2(size, PLAB::min_size());
1044
1045 // Figure out size of new PLAB, looking back at heuristics. Expand aggressively.
1046 size_t cur_size = ShenandoahThreadLocalData::plab_size(thread);
1047 if (cur_size == 0) {
1048 cur_size = PLAB::min_size();
1049 }
1050 size_t future_size = cur_size * 2;
1051 // Limit growth of PLABs to ShenandoahMaxEvacLABRatio * the minimum size. This enables more equitable distribution of
1052 // available evacuation buidget between the many threads that are coordinating in the evacuation effort.
1053 if (ShenandoahMaxEvacLABRatio > 0) {
1054 future_size = MIN2(future_size, PLAB::min_size() * ShenandoahMaxEvacLABRatio);
1055 }
1056 future_size = MIN2(future_size, PLAB::max_size());
1057 future_size = MAX2(future_size, PLAB::min_size());
1058
1059 size_t unalignment = future_size % CardTable::card_size_in_words();
1060 if (unalignment != 0) {
1061 future_size = future_size - unalignment + CardTable::card_size_in_words();
1062 }
1063
1064 // Record new heuristic value even if we take any shortcut. This captures
1065 // the case when moderately-sized objects always take a shortcut. At some point,
1066 // heuristics should catch up with them. Note that the requested cur_size may
1067 // not be honored, but we remember that this is the preferred size.
1068 ShenandoahThreadLocalData::set_plab_size(thread, future_size);
1069 if (cur_size < size) {
1070 // The PLAB to be allocated is still not large enough to hold the object. Fall back to shared allocation.
1071 // This avoids retiring perfectly good PLABs in order to represent a single large object allocation.
1072 return nullptr;
1073 }
1074
1075 // Retire current PLAB, and allocate a new one.
1076 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1077 if (plab->words_remaining() < PLAB::min_size()) {
1078 // Retire current PLAB, and allocate a new one.
1079 // CAUTION: retire_plab may register the remnant filler object with the remembered set scanner without a lock. This
1080 // is safe iff it is assured that each PLAB is a whole-number multiple of card-mark memory size and each PLAB is
1081 // aligned with the start of a card's memory range.
1082 retire_plab(plab, thread);
1083
1084 size_t actual_size = 0;
1085 // allocate_new_plab resets plab_evacuated and plab_promoted and disables promotions if old-gen available is
1086 // less than the remaining evacuation need. It also adjusts plab_preallocated and expend_promoted if appropriate.
1087 HeapWord* plab_buf = allocate_new_plab(min_size, cur_size, &actual_size);
1088 if (plab_buf == nullptr) {
1089 if (min_size == PLAB::min_size()) {
1090 // Disable plab promotions for this thread because we cannot even allocate a plab of minimal size. This allows us
1091 // to fail faster on subsequent promotion attempts.
1092 ShenandoahThreadLocalData::disable_plab_promotions(thread);
1093 }
1094 return NULL;
1095 } else {
1096 ShenandoahThreadLocalData::enable_plab_retries(thread);
1097 }
1098 assert (size <= actual_size, "allocation should fit");
1099 if (ZeroTLAB) {
1100 // ..and clear it.
1101 Copy::zero_to_words(plab_buf, actual_size);
1102 } else {
1103 // ...and zap just allocated object.
1104 #ifdef ASSERT
1105 // Skip mangling the space corresponding to the object header to
1106 // ensure that the returned space is not considered parsable by
1107 // any concurrent GC thread.
1108 size_t hdr_size = oopDesc::header_size();
1109 Copy::fill_to_words(plab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
1110 #endif // ASSERT
1111 }
1112 plab->set_buf(plab_buf, actual_size);
1113 if (is_promotion && !ShenandoahThreadLocalData::allow_plab_promotions(thread)) {
1114 return nullptr;
1115 }
1116 return plab->allocate(size);
1117 } else {
1118 // If there's still at least min_size() words available within the current plab, don't retire it. Let's gnaw
1119 // away on this plab as long as we can. Meanwhile, return nullptr to force this particular allocation request
1120 // to be satisfied with a shared allocation. By packing more promotions into the previously allocated PLAB, we
1121 // reduce the likelihood of evacuation failures, and we we reduce the need for downsizing our PLABs.
1122 return nullptr;
1123 }
1124 }
1125
1126 // TODO: It is probably most efficient to register all objects (both promotions and evacuations) that were allocated within
1127 // this plab at the time we retire the plab. A tight registration loop will run within both code and data caches. This change
1128 // would allow smaller and faster in-line implementation of alloc_from_plab(). Since plabs are aligned on card-table boundaries,
1129 // this object registration loop can be performed without acquiring a lock.
1130 void ShenandoahHeap::retire_plab(PLAB* plab, Thread* thread) {
1131 // We don't enforce limits on plab_evacuated. We let it consume all available old-gen memory in order to reduce
1132 // probability of an evacuation failure. We do enforce limits on promotion, to make sure that excessive promotion
1133 // does not result in an old-gen evacuation failure. Note that a failed promotion is relatively harmless. Any
1134 // object that fails to promote in the current cycle will be eligible for promotion in a subsequent cycle.
1135
1136 // When the plab was instantiated, its entirety was treated as if the entire buffer was going to be dedicated to
1137 // promotions. Now that we are retiring the buffer, we adjust for the reality that the plab is not entirely promotions.
1138 // 1. Some of the plab may have been dedicated to evacuations.
1139 // 2. Some of the plab may have been abandoned due to waste (at the end of the plab).
1140 size_t not_promoted =
1141 ShenandoahThreadLocalData::get_plab_preallocated_promoted(thread) - ShenandoahThreadLocalData::get_plab_promoted(thread);
1142 ShenandoahThreadLocalData::reset_plab_promoted(thread);
1143 ShenandoahThreadLocalData::reset_plab_evacuated(thread);
1144 ShenandoahThreadLocalData::set_plab_preallocated_promoted(thread, 0);
1145 if (not_promoted > 0) {
1146 unexpend_promoted(not_promoted);
1147 }
1148 size_t waste = plab->waste();
1149 HeapWord* top = plab->top();
1150 plab->retire();
1151 if (top != nullptr && plab->waste() > waste && is_in_old(top)) {
1152 // If retiring the plab created a filler object, then we
1153 // need to register it with our card scanner so it can
1154 // safely walk the region backing the plab.
1155 log_debug(gc)("retire_plab() is registering remnant of size " SIZE_FORMAT " at " PTR_FORMAT,
1156 plab->waste() - waste, p2i(top));
1157 card_scan()->register_object_without_lock(top);
1158 }
1159 }
1160
1161 void ShenandoahHeap::retire_plab(PLAB* plab) {
1162 Thread* thread = Thread::current();
1163 retire_plab(plab, thread);
1164 }
1165
1166 void ShenandoahHeap::cancel_old_gc() {
1167 shenandoah_assert_safepoint();
1168 assert(_old_generation != nullptr, "Should only have mixed collections in generation mode.");
1169 log_info(gc)("Terminating old gc cycle.");
1170
1171 // Stop marking
1172 old_generation()->cancel_marking();
1173 // Stop coalescing undead objects
1174 set_prepare_for_old_mark_in_progress(false);
1175 // Stop tracking old regions
1176 old_heuristics()->abandon_collection_candidates();
1177 // Remove old generation access to young generation mark queues
1178 young_generation()->set_old_gen_task_queues(nullptr);
1179 // Transition to IDLE now.
1180 _old_generation->transition_to(ShenandoahOldGeneration::IDLE);
1181 }
1182
1183 bool ShenandoahHeap::is_old_gc_active() {
1184 return _old_generation->state() != ShenandoahOldGeneration::IDLE;
1185 }
1186
1187 // xfer_limit is the maximum we're able to transfer from young to old
1188 void ShenandoahHeap::adjust_generation_sizes_for_next_cycle(
1189 size_t xfer_limit, size_t young_cset_regions, size_t old_cset_regions) {
1190
1191 // Make sure old-generation is large enough, but no larger, than is necessary to hold mixed evacuations
1192 // and promotions if we anticipate either.
1193 size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
1194 size_t promo_load = get_promotion_potential();
1195 // The free set will reserve this amount of memory to hold young evacuations
1196 size_t young_reserve = (young_generation()->max_capacity() * ShenandoahEvacReserve) / 100;
1197 size_t old_reserve = 0;
1198 size_t mixed_candidates = old_heuristics()->unprocessed_old_collection_candidates();
1199 bool doing_mixed = (mixed_candidates > 0);
1200 bool doing_promotions = promo_load > 0;
1201
1202 // round down
1203 size_t max_old_region_xfer = xfer_limit / region_size_bytes;
1204
1205 // We can limit the reserve to the size of anticipated promotions
1206 size_t max_old_reserve = young_reserve * ShenandoahOldEvacRatioPercent / (100 - ShenandoahOldEvacRatioPercent);
1207 // Here's the algebra:
1208 // TotalEvacuation = OldEvacuation + YoungEvacuation
1209 // OldEvacuation = TotalEvacuation*(ShenandoahOldEvacRatioPercent/100)
1210 // OldEvacuation = YoungEvacuation * (ShenandoahOldEvacRatioPercent/100)/(1 - ShenandoahOldEvacRatioPercent/100)
1211 // OldEvacuation = YoungEvacuation * ShenandoahOldEvacRatioPercent/(100 - ShenandoahOldEvacRatioPercent)
1212
1213 size_t reserve_for_mixed, reserve_for_promo;
1214 if (doing_mixed) {
1215 assert(old_generation()->available() >= old_generation()->free_unaffiliated_regions() * region_size_bytes,
1216 "Unaffiliated available must be less than total available");
1217
1218 // We want this much memory to be unfragmented in order to reliably evacuate old. This is conservative because we
1219 // may not evacuate the entirety of unprocessed candidates in a single mixed evacuation.
1220 size_t max_evac_need = (size_t)
1221 (old_heuristics()->unprocessed_old_collection_candidates_live_memory() * ShenandoahOldEvacWaste);
1222 size_t old_fragmented_available =
1223 old_generation()->available() - old_generation()->free_unaffiliated_regions() * region_size_bytes;
1224 reserve_for_mixed = max_evac_need + old_fragmented_available;
1225 if (reserve_for_mixed > max_old_reserve) {
1226 reserve_for_mixed = max_old_reserve;
1227 }
1228 } else {
1229 reserve_for_mixed = 0;
1230 }
1231
1232 size_t available_for_promotions = max_old_reserve - reserve_for_mixed;
1233 if (doing_promotions) {
1234 // We're only promoting and we have a maximum bound on the amount to be promoted
1235 reserve_for_promo = (size_t) (promo_load * ShenandoahPromoEvacWaste);
1236 if (reserve_for_promo > available_for_promotions) {
1237 reserve_for_promo = available_for_promotions;
1238 }
1239 } else {
1240 reserve_for_promo = 0;
1241 }
1242 old_reserve = reserve_for_mixed + reserve_for_promo;
1243 assert(old_reserve <= max_old_reserve, "cannot reserve more than max for old evacuations");
1244 size_t old_available = old_generation()->available() + old_cset_regions * region_size_bytes;
1245 size_t young_available = young_generation()->available() + young_cset_regions * region_size_bytes;
1246 size_t old_region_deficit = 0;
1247 size_t old_region_surplus = 0;
1248 if (old_available >= old_reserve) {
1249 size_t old_excess = old_available - old_reserve;
1250 size_t excess_regions = old_excess / region_size_bytes;
1251 size_t unaffiliated_old_regions = old_generation()->free_unaffiliated_regions() + old_cset_regions;
1252 size_t unaffiliated_old = unaffiliated_old_regions * region_size_bytes;
1253 if (unaffiliated_old_regions < excess_regions) {
1254 // We'll give only unaffiliated old to young, which is known to be less than the excess.
1255 old_region_surplus = unaffiliated_old_regions;
1256 } else {
1257 // unaffiliated_old_regions > excess_regions, so we only give away the excess.
1258 old_region_surplus = excess_regions;
1259 }
1260 } else {
1261 // We need to request transfer from YOUNG. Ignore that this will directly impact young_generation()->max_capacity(),
1262 // indirectly impacting young_reserve and old_reserve. These computations are conservative.
1263 size_t old_need = old_reserve - old_available;
1264 // Round up the number of regions needed from YOUNG
1265 old_region_deficit = (old_need + region_size_bytes - 1) / region_size_bytes;
1266 }
1267 if (old_region_deficit > max_old_region_xfer) {
1268 // If we're running short on young-gen memory, limit the xfer. Old-gen collection activities will be curtailed
1269 // if the budget is smaller than desired.
1270 old_region_deficit = max_old_region_xfer;
1271 }
1272 set_old_region_surplus(old_region_surplus);
1273 set_old_region_deficit(old_region_deficit);
1274 }
1275
1276 // Called from stubs in JIT code or interpreter
1277 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
1278 size_t requested_size,
1279 size_t* actual_size) {
1280 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
1281 HeapWord* res = allocate_memory(req, false);
1282 if (res != nullptr) {
1283 *actual_size = req.actual_size();
1284 } else {
1285 *actual_size = 0;
1286 }
1287 return res;
1288 }
1289
1290 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
1291 size_t word_size,
1292 size_t* actual_size) {
1293 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
1294 HeapWord* res = allocate_memory(req, false);
1295 if (res != nullptr) {
1296 *actual_size = req.actual_size();
1297 } else {
1298 *actual_size = 0;
1299 }
1300 return res;
1301 }
1302
1303 HeapWord* ShenandoahHeap::allocate_new_plab(size_t min_size,
1304 size_t word_size,
1305 size_t* actual_size) {
1306 // Align requested sizes to card sized multiples
1307 size_t words_in_card = CardTable::card_size_in_words();
1308 size_t align_mask = ~(words_in_card - 1);
1309 min_size = (min_size + words_in_card - 1) & align_mask;
1310 word_size = (word_size + words_in_card - 1) & align_mask;
1311 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_plab(min_size, word_size);
1312 // Note that allocate_memory() sets a thread-local flag to prohibit further promotions by this thread
1313 // if we are at risk of infringing on the old-gen evacuation budget.
1314 HeapWord* res = allocate_memory(req, false);
1315 if (res != nullptr) {
1316 *actual_size = req.actual_size();
1317 } else {
1318 *actual_size = 0;
1319 }
1320 return res;
1321 }
1322
1323 // is_promotion is true iff this allocation is known for sure to hold the result of young-gen evacuation
1324 // to old-gen. plab allocates are not known as such, since they may hold old-gen evacuations.
1325 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req, bool is_promotion) {
1326 intptr_t pacer_epoch = 0;
1327 bool in_new_region = false;
1328 HeapWord* result = nullptr;
1329
1330 if (req.is_mutator_alloc()) {
1331 if (ShenandoahPacing) {
1332 pacer()->pace_for_alloc(req.size());
1333 pacer_epoch = pacer()->epoch();
1334 }
1335
1336 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
1337 result = allocate_memory_under_lock(req, in_new_region, is_promotion);
1338 }
1339
1340 // Allocation failed, block until control thread reacted, then retry allocation.
1341 //
1342 // It might happen that one of the threads requesting allocation would unblock
1343 // way later after GC happened, only to fail the second allocation, because
1344 // other threads have already depleted the free storage. In this case, a better
1345 // strategy is to try again, as long as GC makes progress (or until at least
1346 // one full GC has completed).
1347 size_t original_count = shenandoah_policy()->full_gc_count();
1348 while (result == nullptr
1349 && (_progress_last_gc.is_set() || original_count == shenandoah_policy()->full_gc_count())) {
1350 control_thread()->handle_alloc_failure(req);
1351 result = allocate_memory_under_lock(req, in_new_region, is_promotion);
1352 }
1353
1354 } else {
1355 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
1356 result = allocate_memory_under_lock(req, in_new_region, is_promotion);
1357 // Do not call handle_alloc_failure() here, because we cannot block.
1358 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1359 }
1360
1361 if (in_new_region) {
1362 control_thread()->notify_heap_changed();
1363 regulator_thread()->notify_heap_changed();
1364 }
1365
1366 if (result == nullptr) {
1367 req.set_actual_size(0);
1368 }
1369
1370 // This is called regardless of the outcome of the allocation to account
1371 // for any waste created by retiring regions with this request.
1372 increase_used(req);
1373
1374 if (result != nullptr) {
1375 size_t requested = req.size();
1376 size_t actual = req.actual_size();
1377
1378 assert (req.is_lab_alloc() || (requested == actual),
1379 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
1380 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
1381
1382 if (req.is_mutator_alloc()) {
1383 // If we requested more than we were granted, give the rest back to pacer.
1384 // This only matters if we are in the same pacing epoch: do not try to unpace
1385 // over the budget for the other phase.
1386 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
1387 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
1388 }
1389 }
1390 }
1391
1392 return result;
1393 }
1394
1395 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region, bool is_promotion) {
1396 bool try_smaller_lab_size = false;
1397 size_t smaller_lab_size;
1398 {
1399 // promotion_eligible pertains only to PLAB allocations, denoting that the PLAB is allowed to allocate for promotions.
1400 bool promotion_eligible = false;
1401 bool allow_allocation = true;
1402 bool plab_alloc = false;
1403 size_t requested_bytes = req.size() * HeapWordSize;
1404 HeapWord* result = nullptr;
1405 ShenandoahHeapLocker locker(lock());
1406 Thread* thread = Thread::current();
1407
1408 if (mode()->is_generational()) {
1409 if (req.affiliation() == YOUNG_GENERATION) {
1410 if (req.is_mutator_alloc()) {
1411 size_t young_words_available = young_generation()->available() / HeapWordSize;
1412 if (ShenandoahElasticTLAB && req.is_lab_alloc() && (req.min_size() < young_words_available)) {
1413 // Allow ourselves to try a smaller lab size even if requested_bytes <= young_available. We may need a smaller
1414 // lab size because young memory has become too fragmented.
1415 try_smaller_lab_size = true;
1416 smaller_lab_size = (young_words_available < req.size())? young_words_available: req.size();
1417 } else if (req.size() > young_words_available) {
1418 // Can't allocate because even min_size() is larger than remaining young_available
1419 log_info(gc, ergo)("Unable to shrink %s alloc request of minimum size: " SIZE_FORMAT
1420 ", young words available: " SIZE_FORMAT, req.type_string(),
1421 HeapWordSize * (req.is_lab_alloc()? req.min_size(): req.size()), young_words_available);
1422 return nullptr;
1423 }
1424 }
1425 } else { // reg.affiliation() == OLD_GENERATION
1426 assert(req.type() != ShenandoahAllocRequest::_alloc_gclab, "GCLAB pertains only to young-gen memory");
1427 if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
1428 plab_alloc = true;
1429 size_t promotion_avail = get_promoted_reserve();
1430 size_t promotion_expended = get_promoted_expended();
1431 if (promotion_expended + requested_bytes > promotion_avail) {
1432 promotion_avail = 0;
1433 if (get_old_evac_reserve() == 0) {
1434 // There are no old-gen evacuations in this pass. There's no value in creating a plab that cannot
1435 // be used for promotions.
1436 allow_allocation = false;
1437 }
1438 } else {
1439 promotion_avail = promotion_avail - (promotion_expended + requested_bytes);
1440 promotion_eligible = true;
1441 }
1442 } else if (is_promotion) {
1443 // This is a shared alloc for promotion
1444 size_t promotion_avail = get_promoted_reserve();
1445 size_t promotion_expended = get_promoted_expended();
1446 if (promotion_expended + requested_bytes > promotion_avail) {
1447 promotion_avail = 0;
1448 } else {
1449 promotion_avail = promotion_avail - (promotion_expended + requested_bytes);
1450 }
1451 if (promotion_avail == 0) {
1452 // We need to reserve the remaining memory for evacuation. Reject this allocation. The object will be
1453 // evacuated to young-gen memory and promoted during a future GC pass.
1454 return nullptr;
1455 }
1456 // Else, we'll allow the allocation to proceed. (Since we hold heap lock, the tested condition remains true.)
1457 } else {
1458 // This is a shared allocation for evacuation. Memory has already been reserved for this purpose.
1459 }
1460 }
1461 } // This ends the is_generational() block
1462
1463 // First try the original request. If TLAB request size is greater than available, allocate() will attempt to downsize
1464 // request to fit within available memory.
1465 result = (allow_allocation)? _free_set->allocate(req, in_new_region): nullptr;
1466 if (result != nullptr) {
1467 if (req.is_old()) {
1468 ShenandoahThreadLocalData::reset_plab_promoted(thread);
1469 if (req.is_gc_alloc()) {
1470 bool disable_plab_promotions = false;
1471 if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
1472 if (promotion_eligible) {
1473 size_t actual_size = req.actual_size() * HeapWordSize;
1474 // The actual size of the allocation may be larger than the requested bytes (due to alignment on card boundaries).
1475 // If this puts us over our promotion budget, we need to disable future PLAB promotions for this thread.
1476 if (get_promoted_expended() + actual_size <= get_promoted_reserve()) {
1477 // Assume the entirety of this PLAB will be used for promotion. This prevents promotion from overreach.
1478 // When we retire this plab, we'll unexpend what we don't really use.
1479 ShenandoahThreadLocalData::enable_plab_promotions(thread);
1480 expend_promoted(actual_size);
1481 assert(get_promoted_expended() <= get_promoted_reserve(), "Do not expend more promotion than budgeted");
1482 ShenandoahThreadLocalData::set_plab_preallocated_promoted(thread, actual_size);
1483 } else {
1484 disable_plab_promotions = true;
1485 }
1486 } else {
1487 disable_plab_promotions = true;
1488 }
1489 if (disable_plab_promotions) {
1490 // Disable promotions in this thread because entirety of this PLAB must be available to hold old-gen evacuations.
1491 ShenandoahThreadLocalData::disable_plab_promotions(thread);
1492 ShenandoahThreadLocalData::set_plab_preallocated_promoted(thread, 0);
1493 }
1494 } else if (is_promotion) {
1495 // Shared promotion. Assume size is requested_bytes.
1496 expend_promoted(requested_bytes);
1497 assert(get_promoted_expended() <= get_promoted_reserve(), "Do not expend more promotion than budgeted");
1498 }
1499 }
1500
1501 // Register the newly allocated object while we're holding the global lock since there's no synchronization
1502 // built in to the implementation of register_object(). There are potential races when multiple independent
1503 // threads are allocating objects, some of which might span the same card region. For example, consider
1504 // a card table's memory region within which three objects are being allocated by three different threads:
1505 //
1506 // objects being "concurrently" allocated:
1507 // [-----a------][-----b-----][--------------c------------------]
1508 // [---- card table memory range --------------]
1509 //
1510 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a
1511 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region.
1512 // allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region.
1513 // allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this
1514 // card region.
1515 //
1516 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as
1517 // last-start representing object b while first-start represents object c. This is why we need to require all
1518 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range.
1519 ShenandoahHeap::heap()->card_scan()->register_object(result);
1520 }
1521 } else {
1522 // The allocation failed. If this was a plab allocation, We've already retired it and no longer have a plab.
1523 if (req.is_old() && req.is_gc_alloc() && (req.type() == ShenandoahAllocRequest::_alloc_plab)) {
1524 // We don't need to disable PLAB promotions because there is no PLAB. We leave promotions enabled because
1525 // this allows the surrounding infrastructure to retry alloc_plab_slow() with a smaller PLAB size.
1526 ShenandoahThreadLocalData::set_plab_preallocated_promoted(thread, 0);
1527 }
1528 }
1529 if ((result != nullptr) || !try_smaller_lab_size) {
1530 return result;
1531 }
1532 // else, fall through to try_smaller_lab_size
1533 } // This closes the block that holds the heap lock, releasing the lock.
1534
1535 // We failed to allocate the originally requested lab size. Let's see if we can allocate a smaller lab size.
1536 if (req.size() == smaller_lab_size) {
1537 // If we were already trying to allocate min size, no value in attempting to repeat the same. End the recursion.
1538 return nullptr;
1539 }
1540
1541 // We arrive here if the tlab allocation request can be resized to fit within young_available
1542 assert((req.affiliation() == YOUNG_GENERATION) && req.is_lab_alloc() && req.is_mutator_alloc() &&
1543 (smaller_lab_size < req.size()), "Only shrink allocation request size for TLAB allocations");
1544
1545 // By convention, ShenandoahAllocationRequest is primarily read-only. The only mutable instance data is represented by
1546 // actual_size(), which is overwritten with the size of the allocaion when the allocation request is satisfied. We use a
1547 // recursive call here rather than introducing new methods to mutate the existing ShenandoahAllocationRequest argument.
1548 // Mutation of the existing object might result in astonishing results if calling contexts assume the content of immutable
1549 // fields remain constant. The original TLAB allocation request was for memory that exceeded the current capacity. We'll
1550 // attempt to allocate a smaller TLAB. If this is successful, we'll update actual_size() of our incoming
1551 // ShenandoahAllocRequest. If the recursive request fails, we'll simply return nullptr.
1552
1553 // Note that we've relinquished the HeapLock and some other thread may perform additional allocation before our recursive
1554 // call reacquires the lock. If that happens, we will need another recursive call to further reduce the size of our request
1555 // for each time another thread allocates young memory during the brief intervals that the heap lock is available to
1556 // interfering threads. We expect this interference to be rare. The recursion bottoms out when young_available is
1557 // smaller than req.min_size(). The inner-nested call to allocate_memory_under_lock() uses the same min_size() value
1558 // as this call, but it uses a preferred size() that is smaller than our preferred size, and is no larger than what we most
1559 // recently saw as the memory currently available within the young generation.
1560
1561 // TODO: At the expense of code clarity, we could rewrite this recursive solution to use iteration. We need at most one
1562 // extra instance of the ShenandoahAllocRequest, which we can re-initialize multiple times inside a loop, with one iteration
1563 // of the loop required for each time the existing solution would recurse. An iterative solution would be more efficient
1564 // in CPU time and stack memory utilization. The expectation is that it is very rare that we would recurse more than once
1565 // so making this change is not currently seen as a high priority.
1566
1567 ShenandoahAllocRequest smaller_req = ShenandoahAllocRequest::for_tlab(req.min_size(), smaller_lab_size);
1568
1569 // Note that shrinking the preferred size gets us past the gatekeeper that checks whether there's available memory to
1570 // satisfy the allocation request. The reality is the actual TLAB size is likely to be even smaller, because it will
1571 // depend on how much memory is available within mutator regions that are not yet fully used.
1572 HeapWord* result = allocate_memory_under_lock(smaller_req, in_new_region, is_promotion);
1573 if (result != nullptr) {
1574 req.set_actual_size(smaller_req.actual_size());
1575 }
1576 return result;
1577 }
1578
1579 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1580 bool* gc_overhead_limit_was_exceeded) {
1581 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1582 return allocate_memory(req, false);
1583 }
1584
1585 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1586 size_t size,
1587 Metaspace::MetadataType mdtype) {
1588 MetaWord* result;
1589
1590 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1591 ShenandoahHeuristics* h = global_generation()->heuristics();
1592 if (h->can_unload_classes()) {
1593 h->record_metaspace_oom();
1594 }
1595
1596 // Expand and retry allocation
1597 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1598 if (result != nullptr) {
1599 return result;
1600 }
1601
1602 // Start full GC
1603 collect(GCCause::_metadata_GC_clear_soft_refs);
1604
1605 // Retry allocation
1606 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1607 if (result != nullptr) {
1608 return result;
1609 }
1610
1611 // Expand and retry allocation
1612 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1613 if (result != nullptr) {
1614 return result;
1615 }
1616
1617 // Out of memory
1618 return nullptr;
1619 }
1620
1621 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1622 private:
1623 ShenandoahHeap* const _heap;
1624 Thread* const _thread;
1625 public:
1626 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1627 _heap(heap), _thread(Thread::current()) {}
1628
1629 void do_object(oop p) {
1630 shenandoah_assert_marked(nullptr, p);
1631 if (!p->is_forwarded()) {
1632 _heap->evacuate_object(p, _thread);
1633 }
1634 }
1635 };
1636
1637 class ShenandoahEvacuationTask : public WorkerTask {
1638 private:
1639 ShenandoahHeap* const _sh;
1640 ShenandoahCollectionSet* const _cs;
1641 bool _concurrent;
1642 public:
1643 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1644 ShenandoahCollectionSet* cs,
1645 bool concurrent) :
1646 WorkerTask("Shenandoah Evacuation"),
1647 _sh(sh),
1648 _cs(cs),
1649 _concurrent(concurrent)
1650 {}
1651
1652 void work(uint worker_id) {
1653 if (_concurrent) {
1654 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1655 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
1656 ShenandoahEvacOOMScope oom_evac_scope;
1657 do_work();
1658 } else {
1659 ShenandoahParallelWorkerSession worker_session(worker_id);
1660 ShenandoahEvacOOMScope oom_evac_scope;
1661 do_work();
1662 }
1663 }
1664
1665 private:
1666 void do_work() {
1667 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1668 ShenandoahHeapRegion* r;
1669 while ((r =_cs->claim_next()) != nullptr) {
1670 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1671
1672 _sh->marked_object_iterate(r, &cl);
1673
1674 if (ShenandoahPacing) {
1675 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1676 }
1677 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1678 break;
1679 }
1680 }
1681 }
1682 };
1683
1684 // Unlike ShenandoahEvacuationTask, this iterates over all regions rather than just the collection set.
1685 // This is needed in order to promote humongous start regions if age() >= tenure threshold.
1686 class ShenandoahGenerationalEvacuationTask : public WorkerTask {
1687 private:
1688 ShenandoahHeap* const _sh;
1689 ShenandoahRegionIterator *_regions;
1690 bool _concurrent;
1691 uint _tenuring_threshold;
1692
1693 public:
1694 ShenandoahGenerationalEvacuationTask(ShenandoahHeap* sh,
1695 ShenandoahRegionIterator* iterator,
1696 bool concurrent) :
1697 WorkerTask("Shenandoah Evacuation"),
1698 _sh(sh),
1699 _regions(iterator),
1700 _concurrent(concurrent),
1701 _tenuring_threshold(0)
1702 {
1703 if (_sh->mode()->is_generational()) {
1704 _tenuring_threshold = _sh->age_census()->tenuring_threshold();
1705 }
1706 }
1707
1708 void work(uint worker_id) {
1709 if (_concurrent) {
1710 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1711 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
1712 ShenandoahEvacOOMScope oom_evac_scope;
1713 do_work();
1714 } else {
1715 ShenandoahParallelWorkerSession worker_session(worker_id);
1716 ShenandoahEvacOOMScope oom_evac_scope;
1717 do_work();
1718 }
1719 }
1720
1721 private:
1722 void do_work() {
1723 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1724 ShenandoahHeapRegion* r;
1725 ShenandoahMarkingContext* const ctx = ShenandoahHeap::heap()->marking_context();
1726 size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
1727 size_t old_garbage_threshold = (region_size_bytes * ShenandoahOldGarbageThreshold) / 100;
1728 while ((r = _regions->next()) != nullptr) {
1729 log_debug(gc)("GenerationalEvacuationTask do_work(), looking at %s region " SIZE_FORMAT ", (age: %d) [%s, %s, %s]",
1730 r->is_old()? "old": r->is_young()? "young": "free", r->index(), r->age(),
1731 r->is_active()? "active": "inactive",
1732 r->is_humongous()? (r->is_humongous_start()? "humongous_start": "humongous_continuation"): "regular",
1733 r->is_cset()? "cset": "not-cset");
1734
1735 if (r->is_cset()) {
1736 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1737 _sh->marked_object_iterate(r, &cl);
1738 if (ShenandoahPacing) {
1739 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1740 }
1741 } else if (r->is_young() && r->is_active() && (r->age() >= _tenuring_threshold)) {
1742 HeapWord* tams = ctx->top_at_mark_start(r);
1743 if (r->is_humongous_start()) {
1744 // We promote humongous_start regions along with their affiliated continuations during evacuation rather than
1745 // doing this work during a safepoint. We cannot put humongous regions into the collection set because that
1746 // triggers the load-reference barrier (LRB) to copy on reference fetch.
1747 r->promote_humongous();
1748 } else if (r->is_regular() && (r->get_top_before_promote() != nullptr)) {
1749 assert(r->garbage_before_padded_for_promote() < old_garbage_threshold,
1750 "Region " SIZE_FORMAT " has too much garbage for promotion", r->index());
1751 assert(r->get_top_before_promote() == tams,
1752 "Region " SIZE_FORMAT " has been used for allocations before promotion", r->index());
1753 // Likewise, we cannot put promote-in-place regions into the collection set because that would also trigger
1754 // the LRB to copy on reference fetch.
1755 r->promote_in_place();
1756 }
1757 // Aged humongous continuation regions are handled with their start region. If an aged regular region has
1758 // more garbage than ShenandoahOldGarbageTrheshold, we'll promote by evacuation. If there is room for evacuation
1759 // in this cycle, the region will be in the collection set. If there is not room, the region will be promoted
1760 // by evacuation in some future GC cycle.
1761
1762 // If an aged regular region has received allocations during the current cycle, we do not promote because the
1763 // newly allocated objects do not have appropriate age; this region's age will be reset to zero at end of cycle.
1764 }
1765 // else, region is free, or OLD, or not in collection set, or humongous_continuation,
1766 // or is young humongous_start that is too young to be promoted
1767
1768 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1769 break;
1770 }
1771 }
1772 }
1773 };
1774
1775 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1776 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1777 ShenandoahRegionIterator regions;
1778 ShenandoahGenerationalEvacuationTask task(this, ®ions, concurrent);
1779 workers()->run_task(&task);
1780 } else {
1781 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1782 workers()->run_task(&task);
1783 }
1784 }
1785
1786 void ShenandoahHeap::trash_cset_regions() {
1787 ShenandoahHeapLocker locker(lock());
1788
1789 ShenandoahCollectionSet* set = collection_set();
1790 ShenandoahHeapRegion* r;
1791 set->clear_current_index();
1792 while ((r = set->next()) != nullptr) {
1793 r->make_trash();
1794 }
1795 collection_set()->clear();
1796 }
1797
1798 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1799 st->print_cr("Heap Regions:");
1800 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1801 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1802 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1803 st->print_cr("UWM=update watermark, U=used");
1804 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1805 st->print_cr("S=shared allocs, L=live data");
1806 st->print_cr("CP=critical pins");
1807
1808 for (size_t i = 0; i < num_regions(); i++) {
1809 get_region(i)->print_on(st);
1810 }
1811 }
1812
1813 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1814 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1815
1816 oop humongous_obj = cast_to_oop(start->bottom());
1817 size_t size = humongous_obj->size();
1818 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1819 size_t index = start->index() + required_regions - 1;
1820
1821 assert(!start->has_live(), "liveness must be zero");
1822
1823 for(size_t i = 0; i < required_regions; i++) {
1824 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1825 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1826 ShenandoahHeapRegion* region = get_region(index --);
1827
1828 assert(region->is_humongous(), "expect correct humongous start or continuation");
1829 assert(!region->is_cset(), "Humongous region should not be in collection set");
1830
1831 region->make_trash_immediate();
1832 }
1833 return required_regions;
1834 }
1835
1836 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1837 public:
1838 ShenandoahCheckCleanGCLABClosure() {}
1839 void do_thread(Thread* thread) {
1840 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1841 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1842 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1843
1844 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1845 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1846 assert(plab->words_remaining() == 0, "PLAB should not need retirement");
1847 }
1848 };
1849
1850 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1851 private:
1852 bool const _resize;
1853 public:
1854 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1855 void do_thread(Thread* thread) {
1856 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1857 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1858 gclab->retire();
1859 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1860 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1861 }
1862
1863 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1864 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1865
1866 // There are two reasons to retire all plabs between old-gen evacuation passes.
1867 // 1. We need to make the plab memory parseable by remembered-set scanning.
1868 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1869 ShenandoahHeap::heap()->retire_plab(plab, thread);
1870 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) {
1871 ShenandoahThreadLocalData::set_plab_size(thread, 0);
1872 }
1873 }
1874 };
1875
1876 void ShenandoahHeap::labs_make_parsable() {
1877 assert(UseTLAB, "Only call with UseTLAB");
1878
1879 ShenandoahRetireGCLABClosure cl(false);
1880
1881 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1882 ThreadLocalAllocBuffer& tlab = t->tlab();
1883 tlab.make_parsable();
1884 cl.do_thread(t);
1885 }
1886
1887 workers()->threads_do(&cl);
1888 }
1889
1890 void ShenandoahHeap::tlabs_retire(bool resize) {
1891 assert(UseTLAB, "Only call with UseTLAB");
1892 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1893
1894 ThreadLocalAllocStats stats;
1895
1896 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1897 ThreadLocalAllocBuffer& tlab = t->tlab();
1898 tlab.retire(&stats);
1899 if (resize) {
1900 tlab.resize();
1901 }
1902 }
1903
1904 stats.publish();
1905
1906 #ifdef ASSERT
1907 ShenandoahCheckCleanGCLABClosure cl;
1908 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1909 cl.do_thread(t);
1910 }
1911 workers()->threads_do(&cl);
1912 #endif
1913 }
1914
1915 void ShenandoahHeap::gclabs_retire(bool resize) {
1916 assert(UseTLAB, "Only call with UseTLAB");
1917 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1918
1919 ShenandoahRetireGCLABClosure cl(resize);
1920 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1921 cl.do_thread(t);
1922 }
1923 workers()->threads_do(&cl);
1924
1925 if (safepoint_workers() != nullptr) {
1926 safepoint_workers()->threads_do(&cl);
1927 }
1928 }
1929
1930 class ShenandoahTagGCLABClosure : public ThreadClosure {
1931 public:
1932 void do_thread(Thread* thread) {
1933 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1934 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1935 if (gclab->words_remaining() > 0) {
1936 ShenandoahHeapRegion* r = ShenandoahHeap::heap()->heap_region_containing(gclab->allocate(0));
1937 r->set_young_lab_flag();
1938 }
1939 }
1940 };
1941
1942 void ShenandoahHeap::set_young_lab_region_flags() {
1943 if (!UseTLAB) {
1944 return;
1945 }
1946 for (size_t i = 0; i < _num_regions; i++) {
1947 _regions[i]->clear_young_lab_flags();
1948 }
1949 ShenandoahTagGCLABClosure cl;
1950 workers()->threads_do(&cl);
1951 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1952 cl.do_thread(t);
1953 ThreadLocalAllocBuffer& tlab = t->tlab();
1954 if (tlab.end() != nullptr) {
1955 ShenandoahHeapRegion* r = heap_region_containing(tlab.start());
1956 r->set_young_lab_flag();
1957 }
1958 }
1959 }
1960
1961 // Returns size in bytes
1962 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1963 if (ShenandoahElasticTLAB) {
1964 if (mode()->is_generational()) {
1965 return MIN2(ShenandoahHeapRegion::max_tlab_size_bytes(), young_generation()->available());
1966 } else {
1967 // With Elastic TLABs, return the max allowed size, and let the allocation path
1968 // figure out the safe size for current allocation.
1969 return ShenandoahHeapRegion::max_tlab_size_bytes();
1970 }
1971 } else {
1972 return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes());
1973 }
1974 }
1975
1976 size_t ShenandoahHeap::max_tlab_size() const {
1977 // Returns size in words
1978 return ShenandoahHeapRegion::max_tlab_size_words();
1979 }
1980
1981 void ShenandoahHeap::collect(GCCause::Cause cause) {
1982 control_thread()->request_gc(cause);
1983 }
1984
1985 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1986 //assert(false, "Shouldn't need to do full collections");
1987 }
1988
1989 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1990 ShenandoahHeapRegion* r = heap_region_containing(addr);
1991 if (r != nullptr) {
1992 return r->block_start(addr);
1993 }
1994 return nullptr;
1995 }
1996
1997 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1998 ShenandoahHeapRegion* r = heap_region_containing(addr);
1999 return r->block_is_obj(addr);
2000 }
2001
2002 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
2003 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
2004 }
2005
2006 void ShenandoahHeap::prepare_for_verify() {
2007 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
2008 labs_make_parsable();
2009 }
2010 }
2011
2012 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
2013 if (_shenandoah_policy->is_at_shutdown()) {
2014 return;
2015 }
2016
2017 tcl->do_thread(_control_thread);
2018 tcl->do_thread(_regulator_thread);
2019 workers()->threads_do(tcl);
2020 if (_safepoint_workers != nullptr) {
2021 _safepoint_workers->threads_do(tcl);
2022 }
2023 }
2024
2025 void ShenandoahHeap::print_tracing_info() const {
2026 LogTarget(Info, gc, stats) lt;
2027 if (lt.is_enabled()) {
2028 ResourceMark rm;
2029 LogStream ls(lt);
2030
2031 phase_timings()->print_global_on(&ls);
2032
2033 ls.cr();
2034 ls.cr();
2035
2036 shenandoah_policy()->print_gc_stats(&ls);
2037
2038 ls.cr();
2039
2040 evac_tracker()->print_global_on(&ls);
2041
2042 ls.cr();
2043 ls.cr();
2044 }
2045 }
2046
2047 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
2048 set_gc_cause(cause);
2049 set_gc_generation(generation);
2050
2051 shenandoah_policy()->record_cycle_start();
2052 generation->heuristics()->record_cycle_start();
2053 }
2054
2055 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
2056 generation->heuristics()->record_cycle_end();
2057 if (mode()->is_generational() && (generation->is_global() || upgraded_to_full())) {
2058 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
2059 young_generation()->heuristics()->record_cycle_end();
2060 old_generation()->heuristics()->record_cycle_end();
2061 }
2062 set_gc_cause(GCCause::_no_gc);
2063 }
2064
2065 void ShenandoahHeap::verify(VerifyOption vo) {
2066 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2067 if (ShenandoahVerify) {
2068 verifier()->verify_generic(vo);
2069 } else {
2070 // TODO: Consider allocating verification bitmaps on demand,
2071 // and turn this on unconditionally.
2072 }
2073 }
2074 }
2075 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
2076 return _free_set->capacity();
2077 }
2078
2079 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
2080 private:
2081 MarkBitMap* _bitmap;
2082 ShenandoahScanObjectStack* _oop_stack;
2083 ShenandoahHeap* const _heap;
2084 ShenandoahMarkingContext* const _marking_context;
2085
2086 template <class T>
2087 void do_oop_work(T* p) {
2088 T o = RawAccess<>::oop_load(p);
2089 if (!CompressedOops::is_null(o)) {
2090 oop obj = CompressedOops::decode_not_null(o);
2091 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
2092 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
2093 return;
2094 }
2095 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
2096
2097 assert(oopDesc::is_oop(obj), "must be a valid oop");
2098 if (!_bitmap->is_marked(obj)) {
2099 _bitmap->mark(obj);
2100 _oop_stack->push(obj);
2101 }
2102 }
2103 }
2104 public:
2105 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
2106 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
2107 _marking_context(_heap->marking_context()) {}
2108 void do_oop(oop* p) { do_oop_work(p); }
2109 void do_oop(narrowOop* p) { do_oop_work(p); }
2110 };
2111
2112 /*
2113 * This is public API, used in preparation of object_iterate().
2114 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
2115 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
2116 * control, we call SH::tlabs_retire, SH::gclabs_retire.
2117 */
2118 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
2119 // No-op.
2120 }
2121
2122 /*
2123 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
2124 *
2125 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
2126 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
2127 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
2128 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
2129 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
2130 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
2131 * wiped the bitmap in preparation for next marking).
2132 *
2133 * For all those reasons, we implement object iteration as a single marking traversal, reporting
2134 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
2135 * is allowed to report dead objects, but is not required to do so.
2136 */
2137 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
2138 // Reset bitmap
2139 if (!prepare_aux_bitmap_for_iteration())
2140 return;
2141
2142 ShenandoahScanObjectStack oop_stack;
2143 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
2144 // Seed the stack with root scan
2145 scan_roots_for_iteration(&oop_stack, &oops);
2146
2147 // Work through the oop stack to traverse heap
2148 while (! oop_stack.is_empty()) {
2149 oop obj = oop_stack.pop();
2150 assert(oopDesc::is_oop(obj), "must be a valid oop");
2151 cl->do_object(obj);
2152 obj->oop_iterate(&oops);
2153 }
2154
2155 assert(oop_stack.is_empty(), "should be empty");
2156 // Reclaim bitmap
2157 reclaim_aux_bitmap_for_iteration();
2158 }
2159
2160 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
2161 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
2162
2163 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
2164 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
2165 return false;
2166 }
2167 // Reset bitmap
2168 _aux_bit_map.clear();
2169 return true;
2170 }
2171
2172 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
2173 // Process GC roots according to current GC cycle
2174 // This populates the work stack with initial objects
2175 // It is important to relinquish the associated locks before diving
2176 // into heap dumper
2177 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
2178 ShenandoahHeapIterationRootScanner rp(n_workers);
2179 rp.roots_do(oops);
2180 }
2181
2182 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
2183 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
2184 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
2185 }
2186 }
2187
2188 // Closure for parallelly iterate objects
2189 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
2190 private:
2191 MarkBitMap* _bitmap;
2192 ShenandoahObjToScanQueue* _queue;
2193 ShenandoahHeap* const _heap;
2194 ShenandoahMarkingContext* const _marking_context;
2195
2196 template <class T>
2197 void do_oop_work(T* p) {
2198 T o = RawAccess<>::oop_load(p);
2199 if (!CompressedOops::is_null(o)) {
2200 oop obj = CompressedOops::decode_not_null(o);
2201 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
2202 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
2203 return;
2204 }
2205 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
2206
2207 assert(oopDesc::is_oop(obj), "Must be a valid oop");
2208 if (_bitmap->par_mark(obj)) {
2209 _queue->push(ShenandoahMarkTask(obj));
2210 }
2211 }
2212 }
2213 public:
2214 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
2215 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
2216 _marking_context(_heap->marking_context()) {}
2217 void do_oop(oop* p) { do_oop_work(p); }
2218 void do_oop(narrowOop* p) { do_oop_work(p); }
2219 };
2220
2221 // Object iterator for parallel heap iteraion.
2222 // The root scanning phase happenes in construction as a preparation of
2223 // parallel marking queues.
2224 // Every worker processes it's own marking queue. work-stealing is used
2225 // to balance workload.
2226 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
2227 private:
2228 uint _num_workers;
2229 bool _init_ready;
2230 MarkBitMap* _aux_bit_map;
2231 ShenandoahHeap* _heap;
2232 ShenandoahScanObjectStack _roots_stack; // global roots stack
2233 ShenandoahObjToScanQueueSet* _task_queues;
2234 public:
2235 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
2236 _num_workers(num_workers),
2237 _init_ready(false),
2238 _aux_bit_map(bitmap),
2239 _heap(ShenandoahHeap::heap()) {
2240 // Initialize bitmap
2241 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
2242 if (!_init_ready) {
2243 return;
2244 }
2245
2246 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
2247 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
2248
2249 _init_ready = prepare_worker_queues();
2250 }
2251
2252 ~ShenandoahParallelObjectIterator() {
2253 // Reclaim bitmap
2254 _heap->reclaim_aux_bitmap_for_iteration();
2255 // Reclaim queue for workers
2256 if (_task_queues!= nullptr) {
2257 for (uint i = 0; i < _num_workers; ++i) {
2258 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
2259 if (q != nullptr) {
2260 delete q;
2261 _task_queues->register_queue(i, nullptr);
2262 }
2263 }
2264 delete _task_queues;
2265 _task_queues = nullptr;
2266 }
2267 }
2268
2269 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
2270 if (_init_ready) {
2271 object_iterate_parallel(cl, worker_id, _task_queues);
2272 }
2273 }
2274
2275 private:
2276 // Divide global root_stack into worker queues
2277 bool prepare_worker_queues() {
2278 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
2279 // Initialize queues for every workers
2280 for (uint i = 0; i < _num_workers; ++i) {
2281 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
2282 _task_queues->register_queue(i, task_queue);
2283 }
2284 // Divide roots among the workers. Assume that object referencing distribution
2285 // is related with root kind, use round-robin to make every worker have same chance
2286 // to process every kind of roots
2287 size_t roots_num = _roots_stack.size();
2288 if (roots_num == 0) {
2289 // No work to do
2290 return false;
2291 }
2292
2293 for (uint j = 0; j < roots_num; j++) {
2294 uint stack_id = j % _num_workers;
2295 oop obj = _roots_stack.pop();
2296 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
2297 }
2298 return true;
2299 }
2300
2301 void object_iterate_parallel(ObjectClosure* cl,
2302 uint worker_id,
2303 ShenandoahObjToScanQueueSet* queue_set) {
2304 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
2305 assert(queue_set != nullptr, "task queue must not be null");
2306
2307 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
2308 assert(q != nullptr, "object iterate queue must not be null");
2309
2310 ShenandoahMarkTask t;
2311 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
2312
2313 // Work through the queue to traverse heap.
2314 // Steal when there is no task in queue.
2315 while (q->pop(t) || queue_set->steal(worker_id, t)) {
2316 oop obj = t.obj();
2317 assert(oopDesc::is_oop(obj), "must be a valid oop");
2318 cl->do_object(obj);
2319 obj->oop_iterate(&oops);
2320 }
2321 assert(q->is_empty(), "should be empty");
2322 }
2323 };
2324
2325 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
2326 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
2327 }
2328
2329 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
2330 void ShenandoahHeap::keep_alive(oop obj) {
2331 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
2332 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
2333 }
2334 }
2335
2336 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2337 for (size_t i = 0; i < num_regions(); i++) {
2338 ShenandoahHeapRegion* current = get_region(i);
2339 blk->heap_region_do(current);
2340 }
2341 }
2342
2343 class ShenandoahParallelHeapRegionTask : public WorkerTask {
2344 private:
2345 ShenandoahHeap* const _heap;
2346 ShenandoahHeapRegionClosure* const _blk;
2347
2348 shenandoah_padding(0);
2349 volatile size_t _index;
2350 shenandoah_padding(1);
2351
2352 public:
2353 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
2354 WorkerTask("Shenandoah Parallel Region Operation"),
2355 _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
2356
2357 void work(uint worker_id) {
2358 ShenandoahParallelWorkerSession worker_session(worker_id);
2359 size_t stride = ShenandoahParallelRegionStride;
2360
2361 size_t max = _heap->num_regions();
2362 while (Atomic::load(&_index) < max) {
2363 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
2364 size_t start = cur;
2365 size_t end = MIN2(cur + stride, max);
2366 if (start >= max) break;
2367
2368 for (size_t i = cur; i < end; i++) {
2369 ShenandoahHeapRegion* current = _heap->get_region(i);
2370 _blk->heap_region_do(current);
2371 }
2372 }
2373 }
2374 };
2375
2376 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2377 assert(blk->is_thread_safe(), "Only thread-safe closures here");
2378 if (num_regions() > ShenandoahParallelRegionStride) {
2379 ShenandoahParallelHeapRegionTask task(blk);
2380 workers()->run_task(&task);
2381 } else {
2382 heap_region_iterate(blk);
2383 }
2384 }
2385
2386 class ShenandoahRendezvousClosure : public HandshakeClosure {
2387 public:
2388 inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
2389 inline void do_thread(Thread* thread) {}
2390 };
2391
2392 void ShenandoahHeap::rendezvous_threads() {
2393 ShenandoahRendezvousClosure cl;
2394 Handshake::execute(&cl);
2395 }
2396
2397 void ShenandoahHeap::recycle_trash() {
2398 free_set()->recycle_trash();
2399 }
2400
2401 void ShenandoahHeap::do_class_unloading() {
2402 _unloader.unload();
2403 }
2404
2405 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
2406 // Weak refs processing
2407 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2408 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2409 ShenandoahTimingsTracker t(phase);
2410 ShenandoahGCWorkerPhase worker_phase(phase);
2411 active_generation()->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2412 }
2413
2414 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
2415 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2416
2417 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2418 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2419 // for future GCLABs here.
2420 if (UseTLAB) {
2421 ShenandoahGCPhase phase(concurrent ?
2422 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
2423 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2424 gclabs_retire(ResizeTLAB);
2425 }
2426
2427 _update_refs_iterator.reset();
2428 }
2429
2430 void ShenandoahHeap::set_gc_state_all_threads(char state) {
2431 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
2432 ShenandoahThreadLocalData::set_gc_state(t, state);
2433 }
2434 }
2435
2436 void ShenandoahHeap::set_gc_state_mask(uint mask, bool value) {
2437 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should really be Shenandoah safepoint");
2438 _gc_state.set_cond(mask, value);
2439 set_gc_state_all_threads(_gc_state.raw_value());
2440 }
2441
2442 void ShenandoahHeap::set_evacuation_reserve_quantities(bool is_valid) {
2443 _has_evacuation_reserve_quantities = is_valid;
2444 }
2445
2446 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2447 uint mask;
2448 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2449 if (!in_progress && is_concurrent_old_mark_in_progress()) {
2450 assert(mode()->is_generational(), "Only generational GC has old marking");
2451 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2452 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2453 mask = YOUNG_MARKING;
2454 } else {
2455 mask = MARKING | YOUNG_MARKING;
2456 }
2457 set_gc_state_mask(mask, in_progress);
2458 manage_satb_barrier(in_progress);
2459 }
2460
2461 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2462 #ifdef ASSERT
2463 // has_forwarded_objects() iff UPDATEREFS or EVACUATION
2464 bool has_forwarded = has_forwarded_objects()? 1: 0;
2465 bool updating_or_evacuating = _gc_state.is_set(UPDATEREFS | EVACUATION)? 1: 0;
2466 assert (has_forwarded == updating_or_evacuating, "Has forwarded objects iff updating or evacuating");
2467 #endif
2468 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2469 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2470 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2471 set_gc_state_mask(OLD_MARKING, in_progress);
2472 } else {
2473 set_gc_state_mask(MARKING | OLD_MARKING, in_progress);
2474 }
2475 manage_satb_barrier(in_progress);
2476 }
2477
2478 void ShenandoahHeap::set_prepare_for_old_mark_in_progress(bool in_progress) {
2479 // Unlike other set-gc-state functions, this may happen outside safepoint.
2480 // Is only set and queried by control thread, so no coherence issues.
2481 _prepare_for_old_mark = in_progress;
2482 }
2483
2484 void ShenandoahHeap::set_aging_cycle(bool in_progress) {
2485 _is_aging_cycle.set_cond(in_progress);
2486 }
2487
2488 void ShenandoahHeap::manage_satb_barrier(bool active) {
2489 if (is_concurrent_mark_in_progress()) {
2490 // Ignore request to deactivate barrier while concurrent mark is in progress.
2491 // Do not attempt to re-activate the barrier if it is already active.
2492 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2493 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2494 }
2495 } else {
2496 // No concurrent marking is in progress so honor request to deactivate,
2497 // but only if the barrier is already active.
2498 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2499 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2500 }
2501 }
2502 }
2503
2504 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2505 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2506 set_gc_state_mask(EVACUATION, in_progress);
2507 }
2508
2509 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2510 if (in_progress) {
2511 _concurrent_strong_root_in_progress.set();
2512 } else {
2513 _concurrent_strong_root_in_progress.unset();
2514 }
2515 }
2516
2517 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2518 set_gc_state_mask(WEAK_ROOTS, cond);
2519 }
2520
2521 GCTracer* ShenandoahHeap::tracer() {
2522 return shenandoah_policy()->tracer();
2523 }
2524
2525 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2526 return _free_set->used();
2527 }
2528
2529 bool ShenandoahHeap::try_cancel_gc() {
2530 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
2531 return prev == CANCELLABLE;
2532 }
2533
2534 void ShenandoahHeap::cancel_concurrent_mark() {
2535 _young_generation->cancel_marking();
2536 _old_generation->cancel_marking();
2537 _global_generation->cancel_marking();
2538
2539 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2540 }
2541
2542 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2543 if (try_cancel_gc()) {
2544 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2545 log_info(gc)("%s", msg.buffer());
2546 Events::log(Thread::current(), "%s", msg.buffer());
2547 _cancel_requested_time = os::elapsedTime();
2548 if (cause == GCCause::_shenandoah_upgrade_to_full_gc) {
2549 _upgraded_to_full = true;
2550 }
2551 }
2552 }
2553
2554 uint ShenandoahHeap::max_workers() {
2555 return _max_workers;
2556 }
2557
2558 void ShenandoahHeap::stop() {
2559 // The shutdown sequence should be able to terminate when GC is running.
2560
2561 // Step 1. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2562 _shenandoah_policy->record_shutdown();
2563
2564 // Step 2. Stop requesting collections.
2565 regulator_thread()->stop();
2566
2567 // Step 3. Notify control thread that we are in shutdown.
2568 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
2569 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
2570 control_thread()->prepare_for_graceful_shutdown();
2571
2572 // Step 4. Notify GC workers that we are cancelling GC.
2573 cancel_gc(GCCause::_shenandoah_stop_vm);
2574
2575 // Step 5. Wait until GC worker exits normally.
2576 control_thread()->stop();
2577 }
2578
2579 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2580 if (!unload_classes()) return;
2581 // Unload classes and purge SystemDictionary.
2582 {
2583 ShenandoahPhaseTimings::Phase phase = full_gc ?
2584 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2585 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2586 ShenandoahIsAliveSelector is_alive;
2587 CodeCache::UnloadingScope scope(is_alive.is_alive_closure());
2588 ShenandoahGCPhase gc_phase(phase);
2589 ShenandoahGCWorkerPhase worker_phase(phase);
2590 bool purged_class = SystemDictionary::do_unloading(gc_timer());
2591
2592 uint num_workers = _workers->active_workers();
2593 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, purged_class);
2594 _workers->run_task(&unlink_task);
2595 }
2596
2597 {
2598 ShenandoahGCPhase phase(full_gc ?
2599 ShenandoahPhaseTimings::full_gc_purge_cldg :
2600 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2601 ClassLoaderDataGraph::purge(/*at_safepoint*/true);
2602 }
2603 // Resize and verify metaspace
2604 MetaspaceGC::compute_new_size();
2605 DEBUG_ONLY(MetaspaceUtils::verify();)
2606 }
2607
2608 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
2609 // so they should not have forwarded oops.
2610 // However, we do need to "null" dead oops in the roots, if can not be done
2611 // in concurrent cycles.
2612 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2613 uint num_workers = _workers->active_workers();
2614 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2615 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2616 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2617 ShenandoahGCPhase phase(timing_phase);
2618 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2619 // Cleanup weak roots
2620 if (has_forwarded_objects()) {
2621 ShenandoahForwardedIsAliveClosure is_alive;
2622 ShenandoahUpdateRefsClosure keep_alive;
2623 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
2624 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2625 _workers->run_task(&cleaning_task);
2626 } else {
2627 ShenandoahIsAliveClosure is_alive;
2628 #ifdef ASSERT
2629 ShenandoahAssertNotForwardedClosure verify_cl;
2630 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2631 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2632 #else
2633 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2634 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2635 #endif
2636 _workers->run_task(&cleaning_task);
2637 }
2638 }
2639
2640 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2641 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2642 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2643 ShenandoahGCPhase phase(full_gc ?
2644 ShenandoahPhaseTimings::full_gc_purge :
2645 ShenandoahPhaseTimings::degen_gc_purge);
2646 stw_weak_refs(full_gc);
2647 stw_process_weak_roots(full_gc);
2648 stw_unload_classes(full_gc);
2649 }
2650
2651 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2652 set_gc_state_mask(HAS_FORWARDED, cond);
2653 }
2654
2655 void ShenandoahHeap::set_unload_classes(bool uc) {
2656 _unload_classes.set_cond(uc);
2657 }
2658
2659 bool ShenandoahHeap::unload_classes() const {
2660 return _unload_classes.is_set();
2661 }
2662
2663 address ShenandoahHeap::in_cset_fast_test_addr() {
2664 ShenandoahHeap* heap = ShenandoahHeap::heap();
2665 assert(heap->collection_set() != nullptr, "Sanity");
2666 return (address) heap->collection_set()->biased_map_address();
2667 }
2668
2669 address ShenandoahHeap::gc_state_addr() {
2670 return (address) ShenandoahHeap::heap()->_gc_state.addr_of();
2671 }
2672
2673 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2674 if (mode()->is_generational()) {
2675 young_generation()->reset_bytes_allocated_since_gc_start();
2676 old_generation()->reset_bytes_allocated_since_gc_start();
2677 }
2678
2679 global_generation()->reset_bytes_allocated_since_gc_start();
2680 }
2681
2682 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2683 _degenerated_gc_in_progress.set_cond(in_progress);
2684 }
2685
2686 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2687 _full_gc_in_progress.set_cond(in_progress);
2688 }
2689
2690 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2691 assert (is_full_gc_in_progress(), "should be");
2692 _full_gc_move_in_progress.set_cond(in_progress);
2693 }
2694
2695 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2696 set_gc_state_mask(UPDATEREFS, in_progress);
2697 }
2698
2699 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2700 ShenandoahCodeRoots::register_nmethod(nm);
2701 }
2702
2703 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2704 ShenandoahCodeRoots::unregister_nmethod(nm);
2705 }
2706
2707 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2708 heap_region_containing(o)->record_pin();
2709 }
2710
2711 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2712 ShenandoahHeapRegion* r = heap_region_containing(o);
2713 assert(r != nullptr, "Sanity");
2714 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
2715 r->record_unpin();
2716 }
2717
2718 void ShenandoahHeap::sync_pinned_region_status() {
2719 ShenandoahHeapLocker locker(lock());
2720
2721 for (size_t i = 0; i < num_regions(); i++) {
2722 ShenandoahHeapRegion *r = get_region(i);
2723 if (r->is_active()) {
2724 if (r->is_pinned()) {
2725 if (r->pin_count() == 0) {
2726 r->make_unpinned();
2727 }
2728 } else {
2729 if (r->pin_count() > 0) {
2730 r->make_pinned();
2731 }
2732 }
2733 }
2734 }
2735
2736 assert_pinned_region_status();
2737 }
2738
2739 #ifdef ASSERT
2740 void ShenandoahHeap::assert_pinned_region_status() {
2741 for (size_t i = 0; i < num_regions(); i++) {
2742 ShenandoahHeapRegion* r = get_region(i);
2743 if (active_generation()->contains(r)) {
2744 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2745 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2746 }
2747 }
2748 }
2749 #endif
2750
2751 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2752 return _gc_timer;
2753 }
2754
2755 void ShenandoahHeap::prepare_concurrent_roots() {
2756 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2757 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2758 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2759 set_concurrent_weak_root_in_progress(true);
2760 if (unload_classes()) {
2761 _unloader.prepare();
2762 }
2763 }
2764
2765 void ShenandoahHeap::finish_concurrent_roots() {
2766 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2767 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2768 if (unload_classes()) {
2769 _unloader.finish();
2770 }
2771 }
2772
2773 #ifdef ASSERT
2774 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2775 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2776
2777 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2778 if (UseDynamicNumberOfGCThreads) {
2779 assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
2780 } else {
2781 // Use ParallelGCThreads inside safepoints
2782 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
2783 }
2784 } else {
2785 if (UseDynamicNumberOfGCThreads) {
2786 assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
2787 } else {
2788 // Use ConcGCThreads outside safepoints
2789 assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
2790 }
2791 }
2792 }
2793 #endif
2794
2795 ShenandoahVerifier* ShenandoahHeap::verifier() {
2796 guarantee(ShenandoahVerify, "Should be enabled");
2797 assert (_verifier != nullptr, "sanity");
2798 return _verifier;
2799 }
2800
2801 template<bool CONCURRENT>
2802 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2803 private:
2804 ShenandoahHeap* _heap;
2805 ShenandoahRegionIterator* _regions;
2806 ShenandoahRegionChunkIterator* _work_chunks;
2807
2808 public:
2809 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions,
2810 ShenandoahRegionChunkIterator* work_chunks) :
2811 WorkerTask("Shenandoah Update References"),
2812 _heap(ShenandoahHeap::heap()),
2813 _regions(regions),
2814 _work_chunks(work_chunks)
2815 {
2816 }
2817
2818 void work(uint worker_id) {
2819 if (CONCURRENT) {
2820 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2821 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
2822 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2823 } else {
2824 ShenandoahParallelWorkerSession worker_session(worker_id);
2825 do_work<ShenandoahSTWUpdateRefsClosure>(worker_id);
2826 }
2827 }
2828
2829 private:
2830 template<class T>
2831 void do_work(uint worker_id) {
2832 T cl;
2833 if (CONCURRENT && (worker_id == 0)) {
2834 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2835 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2836 size_t cset_regions = _heap->collection_set()->count();
2837 // We cannot transfer any more regions than will be reclaimed when the existing collection set is recycled, because
2838 // we need the reclaimed collection set regions to replenish the collector reserves
2839 _heap->free_set()->move_collector_sets_to_mutator(cset_regions);
2840 }
2841 // If !CONCURRENT, there's no value in expanding Mutator free set
2842
2843 ShenandoahHeapRegion* r = _regions->next();
2844 // We update references for global, old, and young collections.
2845 assert(_heap->active_generation()->is_mark_complete(), "Expected complete marking");
2846 ShenandoahMarkingContext* const ctx = _heap->marking_context();
2847 bool is_mixed = _heap->collection_set()->has_old_regions();
2848 while (r != nullptr) {
2849 HeapWord* update_watermark = r->get_update_watermark();
2850 assert (update_watermark >= r->bottom(), "sanity");
2851
2852 log_debug(gc)("ShenandoahUpdateHeapRefsTask::do_work(%u) looking at region " SIZE_FORMAT, worker_id, r->index());
2853 bool region_progress = false;
2854 if (r->is_active() && !r->is_cset()) {
2855 if (!_heap->mode()->is_generational() || r->is_young()) {
2856 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2857 region_progress = true;
2858 } else if (r->is_old()) {
2859 if (_heap->active_generation()->is_global()) {
2860 // Note that GLOBAL collection is not as effectively balanced as young and mixed cycles. This is because
2861 // concurrent GC threads are parceled out entire heap regions of work at a time and there
2862 // is no "catchup phase" consisting of remembered set scanning, during which parcels of work are smaller
2863 // and more easily distributed more fairly across threads.
2864
2865 // TODO: Consider an improvement to load balance GLOBAL GC.
2866 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2867 region_progress = true;
2868 }
2869 // Otherwise, this is an old region in a young or mixed cycle. Process it during a second phase, below.
2870 // Don't bother to report pacing progress in this case.
2871 } else {
2872 // Because updating of references runs concurrently, it is possible that a FREE inactive region transitions
2873 // to a non-free active region while this loop is executing. Whenever this happens, the changing of a region's
2874 // active status may propagate at a different speed than the changing of the region's affiliation.
2875
2876 // When we reach this control point, it is because a race has allowed a region's is_active() status to be seen
2877 // by this thread before the region's affiliation() is seen by this thread.
2878
2879 // It's ok for this race to occur because the newly transformed region does not have any references to be
2880 // updated.
2881
2882 assert(r->get_update_watermark() == r->bottom(),
2883 "%s Region " SIZE_FORMAT " is_active but not recognized as YOUNG or OLD so must be newly transitioned from FREE",
2884 r->affiliation_name(), r->index());
2885 }
2886 }
2887 if (region_progress && ShenandoahPacing) {
2888 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2889 }
2890 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2891 return;
2892 }
2893 r = _regions->next();
2894 }
2895
2896 if (_heap->mode()->is_generational() && !_heap->active_generation()->is_global()) {
2897 // Since this is generational and not GLOBAL, we have to process the remembered set. There's no remembered
2898 // set processing if not in generational mode or if GLOBAL mode.
2899
2900 // After this thread has exhausted its traditional update-refs work, it continues with updating refs within remembered set.
2901 // The remembered set workload is better balanced between threads, so threads that are "behind" can catch up with other
2902 // threads during this phase, allowing all threads to work more effectively in parallel.
2903 struct ShenandoahRegionChunk assignment;
2904 RememberedScanner* scanner = _heap->card_scan();
2905
2906 while (!_heap->check_cancelled_gc_and_yield(CONCURRENT) && _work_chunks->next(&assignment)) {
2907 // Keep grabbing next work chunk to process until finished, or asked to yield
2908 ShenandoahHeapRegion* r = assignment._r;
2909 if (r->is_active() && !r->is_cset() && r->is_old()) {
2910 HeapWord* start_of_range = r->bottom() + assignment._chunk_offset;
2911 HeapWord* end_of_range = r->get_update_watermark();
2912 if (end_of_range > start_of_range + assignment._chunk_size) {
2913 end_of_range = start_of_range + assignment._chunk_size;
2914 }
2915
2916 // Old region in a young cycle or mixed cycle.
2917 if (is_mixed) {
2918 // TODO: For mixed evac, consider building an old-gen remembered set that allows restricted updating
2919 // within old-gen HeapRegions. This remembered set can be constructed by old-gen concurrent marking
2920 // and augmented by card marking. For example, old-gen concurrent marking can remember for each old-gen
2921 // card which other old-gen regions it refers to: none, one-other specifically, multiple-other non-specific.
2922 // Update-references when _mixed_evac processess each old-gen memory range that has a traditional DIRTY
2923 // card or if the "old-gen remembered set" indicates that this card holds pointers specifically to an
2924 // old-gen region in the most recent collection set, or if this card holds pointers to other non-specific
2925 // old-gen heap regions.
2926
2927 if (r->is_humongous()) {
2928 if (start_of_range < end_of_range) {
2929 // Need to examine both dirty and clean cards during mixed evac.
2930 r->oop_iterate_humongous_slice(&cl, false, start_of_range, assignment._chunk_size, true);
2931 }
2932 } else {
2933 // Since this is mixed evacuation, old regions that are candidates for collection have not been coalesced
2934 // and filled. Use mark bits to find objects that need to be updated.
2935 //
2936 // Future TODO: establish a second remembered set to identify which old-gen regions point to other old-gen
2937 // regions which are in the collection set for a particular mixed evacuation.
2938 if (start_of_range < end_of_range) {
2939 HeapWord* p = nullptr;
2940 size_t card_index = scanner->card_index_for_addr(start_of_range);
2941 // In case last object in my range spans boundary of my chunk, I may need to scan all the way to top()
2942 ShenandoahObjectToOopBoundedClosure<T> objs(&cl, start_of_range, r->top());
2943
2944 // Any object that begins in a previous range is part of a different scanning assignment. Any object that
2945 // starts after end_of_range is also not my responsibility. (Either allocated during evacuation, so does
2946 // not hold pointers to from-space, or is beyond the range of my assigned work chunk.)
2947
2948 // Find the first object that begins in my range, if there is one.
2949 p = start_of_range;
2950 oop obj = cast_to_oop(p);
2951 HeapWord* tams = ctx->top_at_mark_start(r);
2952 if (p >= tams) {
2953 // We cannot use ctx->is_marked(obj) to test whether an object begins at this address. Instead,
2954 // we need to use the remembered set crossing map to advance p to the first object that starts
2955 // within the enclosing card.
2956
2957 while (true) {
2958 HeapWord* first_object = scanner->first_object_in_card(card_index);
2959 if (first_object != nullptr) {
2960 p = first_object;
2961 break;
2962 } else if (scanner->addr_for_card_index(card_index + 1) < end_of_range) {
2963 card_index++;
2964 } else {
2965 // Force the loop that follows to immediately terminate.
2966 p = end_of_range;
2967 break;
2968 }
2969 }
2970 obj = cast_to_oop(p);
2971 // Note: p may be >= end_of_range
2972 } else if (!ctx->is_marked(obj)) {
2973 p = ctx->get_next_marked_addr(p, tams);
2974 obj = cast_to_oop(p);
2975 // If there are no more marked objects before tams, this returns tams.
2976 // Note that tams is either >= end_of_range, or tams is the start of an object that is marked.
2977 }
2978 while (p < end_of_range) {
2979 // p is known to point to the beginning of marked object obj
2980 objs.do_object(obj);
2981 HeapWord* prev_p = p;
2982 p += obj->size();
2983 if (p < tams) {
2984 p = ctx->get_next_marked_addr(p, tams);
2985 // If there are no more marked objects before tams, this returns tams. Note that tams is
2986 // either >= end_of_range, or tams is the start of an object that is marked.
2987 }
2988 assert(p != prev_p, "Lack of forward progress");
2989 obj = cast_to_oop(p);
2990 }
2991 }
2992 }
2993 } else {
2994 // This is a young evac..
2995 if (start_of_range < end_of_range) {
2996 size_t cluster_size =
2997 CardTable::card_size_in_words() * ShenandoahCardCluster<ShenandoahDirectCardMarkRememberedSet>::CardsPerCluster;
2998 size_t clusters = assignment._chunk_size / cluster_size;
2999 assert(clusters * cluster_size == assignment._chunk_size, "Chunk assignment must align on cluster boundaries");
3000 scanner->process_region_slice(r, assignment._chunk_offset, clusters, end_of_range, &cl, true, worker_id);
3001 }
3002 }
3003 if (ShenandoahPacing && (start_of_range < end_of_range)) {
3004 _heap->pacer()->report_updaterefs(pointer_delta(end_of_range, start_of_range));
3005 }
3006 }
3007 }
3008 }
3009 }
3010 };
3011
3012 void ShenandoahHeap::update_heap_references(bool concurrent) {
3013 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
3014 uint nworkers = workers()->active_workers();
3015 ShenandoahRegionChunkIterator work_list(nworkers);
3016
3017 if (concurrent) {
3018 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator, &work_list);
3019 workers()->run_task(&task);
3020 } else {
3021 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator, &work_list);
3022 workers()->run_task(&task);
3023 }
3024 if (ShenandoahEnableCardStats && card_scan()!=nullptr) { // generational check proxy
3025 card_scan()->log_card_stats(nworkers, CARD_STAT_UPDATE_REFS);
3026 }
3027 }
3028
3029 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
3030 private:
3031 ShenandoahMarkingContext* _ctx;
3032 ShenandoahHeapLock* const _lock;
3033 bool _is_generational;
3034
3035 public:
3036 ShenandoahFinalUpdateRefsUpdateRegionStateClosure(
3037 ShenandoahMarkingContext* ctx) : _ctx(ctx), _lock(ShenandoahHeap::heap()->lock()),
3038 _is_generational(ShenandoahHeap::heap()->mode()->is_generational()) { }
3039
3040 void heap_region_do(ShenandoahHeapRegion* r) {
3041
3042 // Maintenance of region age must follow evacuation in order to account for evacuation allocations within survivor
3043 // regions. We consult region age during the subsequent evacuation to determine whether certain objects need to
3044 // be promoted.
3045 if (_is_generational && r->is_young() && r->is_active()) {
3046 HeapWord *tams = _ctx->top_at_mark_start(r);
3047 HeapWord *top = r->top();
3048
3049 // Allocations move the watermark when top moves. However compacting
3050 // objects will sometimes lower top beneath the watermark, after which,
3051 // attempts to read the watermark will assert out (watermark should not be
3052 // higher than top).
3053 if (top > tams) {
3054 // There have been allocations in this region since the start of the cycle.
3055 // Any objects new to this region must not assimilate elevated age.
3056 r->reset_age();
3057 } else if (ShenandoahHeap::heap()->is_aging_cycle()) {
3058 r->increment_age();
3059 }
3060 }
3061
3062 // Drop unnecessary "pinned" state from regions that does not have CP marks
3063 // anymore, as this would allow trashing them.
3064 if (r->is_active()) {
3065 if (r->is_pinned()) {
3066 if (r->pin_count() == 0) {
3067 ShenandoahHeapLocker locker(_lock);
3068 r->make_unpinned();
3069 }
3070 } else {
3071 if (r->pin_count() > 0) {
3072 ShenandoahHeapLocker locker(_lock);
3073 r->make_pinned();
3074 }
3075 }
3076 }
3077 }
3078
3079 bool is_thread_safe() { return true; }
3080 };
3081
3082 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
3083 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
3084 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
3085
3086 {
3087 ShenandoahGCPhase phase(concurrent ?
3088 ShenandoahPhaseTimings::final_update_refs_update_region_states :
3089 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
3090 ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl (active_generation()->complete_marking_context());
3091 parallel_heap_region_iterate(&cl);
3092
3093 assert_pinned_region_status();
3094 }
3095
3096 {
3097 ShenandoahGCPhase phase(concurrent ?
3098 ShenandoahPhaseTimings::final_update_refs_trash_cset :
3099 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
3100 trash_cset_regions();
3101 }
3102 }
3103
3104 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
3105 ShenandoahGCPhase phase(concurrent ?
3106 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
3107 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
3108 size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
3109 ShenandoahHeapLocker locker(lock());
3110 size_t young_cset_regions, old_cset_regions;
3111 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions);
3112
3113 if (mode()->is_generational()) {
3114 assert(verify_generation_usage(true, old_generation()->used_regions(),
3115 old_generation()->used(), old_generation()->get_humongous_waste(),
3116 true, young_generation()->used_regions(),
3117 young_generation()->used(), young_generation()->get_humongous_waste()),
3118 "Generation accounts are inaccurate");
3119
3120 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
3121 // available for transfer to old. Note that transfer of humongous regions does not impact available.
3122 size_t allocation_runway = young_heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions);
3123 adjust_generation_sizes_for_next_cycle(allocation_runway, young_cset_regions, old_cset_regions);
3124
3125 // Total old_available may have been expanded to hold anticipated promotions. We trigger if the fragmented available
3126 // memory represents more than 16 regions worth of data. Note that fragmentation may increase when we promote regular
3127 // regions in place when many of these regular regions have an abundant amount of available memory within them. Fragmentation
3128 // will decrease as promote-by-copy consumes the available memory within these partially consumed regions.
3129 //
3130 // We consider old-gen to have excessive fragmentation if more than 12.5% of old-gen is free memory that resides
3131 // within partially consumed regions of memory.
3132 }
3133 // Rebuild free set based on adjusted generation sizes.
3134 _free_set->rebuild(young_cset_regions, old_cset_regions);
3135
3136 if (mode()->is_generational()) {
3137 size_t old_available = old_generation()->available();
3138 size_t old_unaffiliated_available = old_generation()->free_unaffiliated_regions() * region_size_bytes;
3139 size_t old_fragmented_available;
3140 assert(old_available >= old_unaffiliated_available, "unaffiliated available is a subset of total available");
3141 old_fragmented_available = old_available - old_unaffiliated_available;
3142
3143 size_t old_capacity = old_generation()->max_capacity();
3144 size_t heap_capacity = capacity();
3145 if ((old_capacity > heap_capacity / 8) && (old_fragmented_available > old_capacity / 8)) {
3146 old_heuristics()->trigger_old_is_fragmented();
3147 }
3148
3149 size_t old_used = old_generation()->used() + old_generation()->get_humongous_waste();
3150 size_t trigger_threshold = old_generation()->usage_trigger_threshold();
3151 // Detects unsigned arithmetic underflow
3152 assert(old_used <= capacity(),
3153 "Old used (" SIZE_FORMAT ", " SIZE_FORMAT") must not be more than heap capacity (" SIZE_FORMAT ")",
3154 old_generation()->used(), old_generation()->get_humongous_waste(), capacity());
3155
3156 if (old_used > trigger_threshold) {
3157 old_heuristics()->trigger_old_has_grown();
3158 }
3159 }
3160 }
3161
3162 void ShenandoahHeap::print_extended_on(outputStream *st) const {
3163 print_on(st);
3164 st->cr();
3165 print_heap_regions_on(st);
3166 }
3167
3168 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
3169 size_t slice = r->index() / _bitmap_regions_per_slice;
3170
3171 size_t regions_from = _bitmap_regions_per_slice * slice;
3172 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
3173 for (size_t g = regions_from; g < regions_to; g++) {
3174 assert (g / _bitmap_regions_per_slice == slice, "same slice");
3175 if (skip_self && g == r->index()) continue;
3176 if (get_region(g)->is_committed()) {
3177 return true;
3178 }
3179 }
3180 return false;
3181 }
3182
3183 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
3184 shenandoah_assert_heaplocked();
3185
3186 // Bitmaps in special regions do not need commits
3187 if (_bitmap_region_special) {
3188 return true;
3189 }
3190
3191 if (is_bitmap_slice_committed(r, true)) {
3192 // Some other region from the group is already committed, meaning the bitmap
3193 // slice is already committed, we exit right away.
3194 return true;
3195 }
3196
3197 // Commit the bitmap slice:
3198 size_t slice = r->index() / _bitmap_regions_per_slice;
3199 size_t off = _bitmap_bytes_per_slice * slice;
3200 size_t len = _bitmap_bytes_per_slice;
3201 char* start = (char*) _bitmap_region.start() + off;
3202
3203 if (!os::commit_memory(start, len, false)) {
3204 return false;
3205 }
3206
3207 if (AlwaysPreTouch) {
3208 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
3209 }
3210
3211 return true;
3212 }
3213
3214 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
3215 shenandoah_assert_heaplocked();
3216
3217 // Bitmaps in special regions do not need uncommits
3218 if (_bitmap_region_special) {
3219 return true;
3220 }
3221
3222 if (is_bitmap_slice_committed(r, true)) {
3223 // Some other region from the group is still committed, meaning the bitmap
3224 // slice is should stay committed, exit right away.
3225 return true;
3226 }
3227
3228 // Uncommit the bitmap slice:
3229 size_t slice = r->index() / _bitmap_regions_per_slice;
3230 size_t off = _bitmap_bytes_per_slice * slice;
3231 size_t len = _bitmap_bytes_per_slice;
3232 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
3233 return false;
3234 }
3235 return true;
3236 }
3237
3238 void ShenandoahHeap::safepoint_synchronize_begin() {
3239 if (ShenandoahSuspendibleWorkers) {
3240 SuspendibleThreadSet::synchronize();
3241 }
3242 }
3243
3244 void ShenandoahHeap::safepoint_synchronize_end() {
3245 if (ShenandoahSuspendibleWorkers) {
3246 SuspendibleThreadSet::desynchronize();
3247 }
3248 }
3249
3250 void ShenandoahHeap::entry_uncommit(double shrink_before, size_t shrink_until) {
3251 static const char *msg = "Concurrent uncommit";
3252 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
3253 EventMark em("%s", msg);
3254
3255 op_uncommit(shrink_before, shrink_until);
3256 }
3257
3258 void ShenandoahHeap::try_inject_alloc_failure() {
3259 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
3260 _inject_alloc_failure.set();
3261 os::naked_short_sleep(1);
3262 if (cancelled_gc()) {
3263 log_info(gc)("Allocation failure was successfully injected");
3264 }
3265 }
3266 }
3267
3268 bool ShenandoahHeap::should_inject_alloc_failure() {
3269 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
3270 }
3271
3272 void ShenandoahHeap::initialize_serviceability() {
3273 if (mode()->is_generational()) {
3274 _young_gen_memory_pool = new ShenandoahYoungGenMemoryPool(this);
3275 _old_gen_memory_pool = new ShenandoahOldGenMemoryPool(this);
3276 _cycle_memory_manager.add_pool(_young_gen_memory_pool);
3277 _cycle_memory_manager.add_pool(_old_gen_memory_pool);
3278 _stw_memory_manager.add_pool(_young_gen_memory_pool);
3279 _stw_memory_manager.add_pool(_old_gen_memory_pool);
3280 } else {
3281 _memory_pool = new ShenandoahMemoryPool(this);
3282 _cycle_memory_manager.add_pool(_memory_pool);
3283 _stw_memory_manager.add_pool(_memory_pool);
3284 }
3285 }
3286
3287 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
3288 GrowableArray<GCMemoryManager*> memory_managers(2);
3289 memory_managers.append(&_cycle_memory_manager);
3290 memory_managers.append(&_stw_memory_manager);
3291 return memory_managers;
3292 }
3293
3294 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
3295 GrowableArray<MemoryPool*> memory_pools(1);
3296 if (mode()->is_generational()) {
3297 memory_pools.append(_young_gen_memory_pool);
3298 memory_pools.append(_old_gen_memory_pool);
3299 } else {
3300 memory_pools.append(_memory_pool);
3301 }
3302 return memory_pools;
3303 }
3304
3305 MemoryUsage ShenandoahHeap::memory_usage() {
3306 return MemoryUsage(_initial_size, used(), committed(), max_capacity());
3307 }
3308
3309 ShenandoahRegionIterator::ShenandoahRegionIterator() :
3310 _heap(ShenandoahHeap::heap()),
3311 _index(0) {}
3312
3313 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
3314 _heap(heap),
3315 _index(0) {}
3316
3317 void ShenandoahRegionIterator::reset() {
3318 _index = 0;
3319 }
3320
3321 bool ShenandoahRegionIterator::has_next() const {
3322 return _index < _heap->num_regions();
3323 }
3324
3325 char ShenandoahHeap::gc_state() const {
3326 return _gc_state.raw_value();
3327 }
3328
3329 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
3330 #ifdef ASSERT
3331 assert(_liveness_cache != nullptr, "sanity");
3332 assert(worker_id < _max_workers, "sanity");
3333 for (uint i = 0; i < num_regions(); i++) {
3334 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
3335 }
3336 #endif
3337 return _liveness_cache[worker_id];
3338 }
3339
3340 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
3341 assert(worker_id < _max_workers, "sanity");
3342 assert(_liveness_cache != nullptr, "sanity");
3343 ShenandoahLiveData* ld = _liveness_cache[worker_id];
3344
3345 for (uint i = 0; i < num_regions(); i++) {
3346 ShenandoahLiveData live = ld[i];
3347 if (live > 0) {
3348 ShenandoahHeapRegion* r = get_region(i);
3349 r->increase_live_data_gc_words(live);
3350 ld[i] = 0;
3351 }
3352 }
3353 }
3354
3355 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
3356 if (is_idle()) return false;
3357
3358 // Objects allocated after marking start are implicitly alive, don't need any barriers during
3359 // marking phase.
3360 if (is_concurrent_mark_in_progress() &&
3361 !marking_context()->allocated_after_mark_start(obj)) {
3362 return true;
3363 }
3364
3365 // Can not guarantee obj is deeply good.
3366 if (has_forwarded_objects()) {
3367 return true;
3368 }
3369
3370 return false;
3371 }
3372
3373 void ShenandoahHeap::transfer_old_pointers_from_satb() {
3374 _old_generation->transfer_pointers_from_satb();
3375 }
3376
3377 template<>
3378 void ShenandoahGenerationRegionClosure<YOUNG>::heap_region_do(ShenandoahHeapRegion* region) {
3379 // Visit young and free regions
3380 if (!region->is_old()) {
3381 _cl->heap_region_do(region);
3382 }
3383 }
3384
3385 template<>
3386 void ShenandoahGenerationRegionClosure<OLD>::heap_region_do(ShenandoahHeapRegion* region) {
3387 // Visit old and free regions
3388 if (!region->is_young()) {
3389 _cl->heap_region_do(region);
3390 }
3391 }
3392
3393 template<>
3394 void ShenandoahGenerationRegionClosure<GLOBAL_GEN>::heap_region_do(ShenandoahHeapRegion* region) {
3395 _cl->heap_region_do(region);
3396 }
3397
3398 template<>
3399 void ShenandoahGenerationRegionClosure<GLOBAL_NON_GEN>::heap_region_do(ShenandoahHeapRegion* region) {
3400 _cl->heap_region_do(region);
3401 }
3402
3403 bool ShenandoahHeap::verify_generation_usage(bool verify_old, size_t old_regions, size_t old_bytes, size_t old_waste,
3404 bool verify_young, size_t young_regions, size_t young_bytes, size_t young_waste) {
3405 size_t tally_old_regions = 0;
3406 size_t tally_old_bytes = 0;
3407 size_t tally_old_waste = 0;
3408 size_t tally_young_regions = 0;
3409 size_t tally_young_bytes = 0;
3410 size_t tally_young_waste = 0;
3411
3412 shenandoah_assert_heaplocked_or_safepoint();
3413 for (size_t i = 0; i < num_regions(); i++) {
3414 ShenandoahHeapRegion* r = get_region(i);
3415 if (r->is_old()) {
3416 tally_old_regions++;
3417 tally_old_bytes += r->used();
3418 if (r->is_humongous()) {
3419 ShenandoahHeapRegion* start = r->humongous_start_region();
3420 HeapWord* obj_addr = start->bottom();
3421 oop obj = cast_to_oop(obj_addr);
3422 size_t word_size = obj->size();
3423 HeapWord* end_addr = obj_addr + word_size;
3424 if (end_addr <= r->end()) {
3425 tally_old_waste += (r->end() - end_addr) * HeapWordSize;
3426 }
3427 }
3428 } else if (r->is_young()) {
3429 tally_young_regions++;
3430 tally_young_bytes += r->used();
3431 if (r->is_humongous()) {
3432 ShenandoahHeapRegion* start = r->humongous_start_region();
3433 HeapWord* obj_addr = start->bottom();
3434 oop obj = cast_to_oop(obj_addr);
3435 size_t word_size = obj->size();
3436 HeapWord* end_addr = obj_addr + word_size;
3437 if (end_addr <= r->end()) {
3438 tally_young_waste += (r->end() - end_addr) * HeapWordSize;
3439 }
3440 }
3441 }
3442 }
3443 if (verify_young &&
3444 ((young_regions != tally_young_regions) || (young_bytes != tally_young_bytes) || (young_waste != tally_young_waste))) {
3445 return false;
3446 } else if (verify_old &&
3447 ((old_regions != tally_old_regions) || (old_bytes != tally_old_bytes) || (old_waste != tally_old_waste))) {
3448 return false;
3449 } else {
3450 return true;
3451 }
3452 }
3453
3454 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
3455 if (!mode()->is_generational()) {
3456 return global_generation();
3457 } else if (affiliation == YOUNG_GENERATION) {
3458 return young_generation();
3459 } else if (affiliation == OLD_GENERATION) {
3460 return old_generation();
3461 }
3462
3463 ShouldNotReachHere();
3464 return nullptr;
3465 }
3466
3467 void ShenandoahHeap::log_heap_status(const char* msg) const {
3468 if (mode()->is_generational()) {
3469 young_generation()->log_status(msg);
3470 old_generation()->log_status(msg);
3471 } else {
3472 global_generation()->log_status(msg);
3473 }
3474 }