1 /*
2 * Copyright (c) 2023, 2024, 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/classUnloadingContext.hpp"
32 #include "gc/shared/gcArguments.hpp"
33 #include "gc/shared/gcTimer.hpp"
34 #include "gc/shared/gcTraceTime.inline.hpp"
35 #include "gc/shared/locationPrinter.inline.hpp"
36 #include "gc/shared/memAllocator.hpp"
37 #include "gc/shared/plab.hpp"
38 #include "gc/shared/tlab_globals.hpp"
39
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/shenandoahClosures.inline.hpp"
45 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
46 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
47 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
48 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
49 #include "gc/shenandoah/shenandoahControlThread.hpp"
50 #include "gc/shenandoah/shenandoahFreeSet.hpp"
51 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp"
52 #include "gc/shenandoah/shenandoahGenerationalHeap.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/shenandoahMonitoringSupport.hpp"
62 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
63 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
64 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
65 #include "gc/shenandoah/shenandoahPadding.hpp"
66 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
67 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
68 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
69 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
70 #include "gc/shenandoah/shenandoahSTWMark.hpp"
71 #include "gc/shenandoah/shenandoahUtils.hpp"
72 #include "gc/shenandoah/shenandoahVerifier.hpp"
73 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
74 #include "gc/shenandoah/shenandoahVMOperations.hpp"
75 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
76 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
77 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
78 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
79 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
80 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
81 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
82 #include "utilities/globalDefinitions.hpp"
83
84 #if INCLUDE_JFR
85 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
86 #endif
87
88 #include "classfile/systemDictionary.hpp"
89 #include "code/codeCache.hpp"
90 #include "memory/classLoaderMetaspace.hpp"
91 #include "memory/metaspaceUtils.hpp"
92 #include "oops/compressedOops.inline.hpp"
93 #include "prims/jvmtiTagMap.hpp"
94 #include "runtime/atomic.hpp"
95 #include "runtime/globals.hpp"
96 #include "runtime/interfaceSupport.inline.hpp"
97 #include "runtime/java.hpp"
98 #include "runtime/orderAccess.hpp"
99 #include "runtime/safepointMechanism.hpp"
100 #include "runtime/vmThread.hpp"
101 #include "services/mallocTracker.hpp"
102 #include "services/memTracker.hpp"
103 #include "utilities/events.hpp"
104 #include "utilities/powerOfTwo.hpp"
105
106 class ShenandoahPretouchHeapTask : public WorkerTask {
107 private:
108 ShenandoahRegionIterator _regions;
109 const size_t _page_size;
110 public:
111 ShenandoahPretouchHeapTask(size_t page_size) :
112 WorkerTask("Shenandoah Pretouch Heap"),
113 _page_size(page_size) {}
114
115 virtual void work(uint worker_id) {
116 ShenandoahHeapRegion* r = _regions.next();
117 while (r != nullptr) {
118 if (r->is_committed()) {
119 os::pretouch_memory(r->bottom(), r->end(), _page_size);
120 }
121 r = _regions.next();
122 }
123 }
124 };
125
126 class ShenandoahPretouchBitmapTask : public WorkerTask {
127 private:
128 ShenandoahRegionIterator _regions;
129 char* _bitmap_base;
130 const size_t _bitmap_size;
131 const size_t _page_size;
132 public:
133 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
134 WorkerTask("Shenandoah Pretouch Bitmap"),
135 _bitmap_base(bitmap_base),
136 _bitmap_size(bitmap_size),
137 _page_size(page_size) {}
138
139 virtual void work(uint worker_id) {
140 ShenandoahHeapRegion* r = _regions.next();
141 while (r != nullptr) {
142 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
143 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
144 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
145
146 if (r->is_committed()) {
147 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
148 }
149
150 r = _regions.next();
151 }
152 }
153 };
154
155 jint ShenandoahHeap::initialize() {
156 //
157 // Figure out heap sizing
158 //
159
160 size_t init_byte_size = InitialHeapSize;
161 size_t min_byte_size = MinHeapSize;
162 size_t max_byte_size = MaxHeapSize;
163 size_t heap_alignment = HeapAlignment;
164
165 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
166
167 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
168 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
169
170 _num_regions = ShenandoahHeapRegion::region_count();
171 assert(_num_regions == (max_byte_size / reg_size_bytes),
172 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
173 _num_regions, max_byte_size, reg_size_bytes);
174
175 size_t num_committed_regions = init_byte_size / reg_size_bytes;
176 num_committed_regions = MIN2(num_committed_regions, _num_regions);
177 assert(num_committed_regions <= _num_regions, "sanity");
178 _initial_size = num_committed_regions * reg_size_bytes;
179
180 size_t num_min_regions = min_byte_size / reg_size_bytes;
181 num_min_regions = MIN2(num_min_regions, _num_regions);
182 assert(num_min_regions <= _num_regions, "sanity");
183 _minimum_size = num_min_regions * reg_size_bytes;
184
185 // Default to max heap size.
186 _soft_max_size = _num_regions * reg_size_bytes;
187
188 _committed = _initial_size;
189
190 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
191 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
192 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
193
194 //
195 // Reserve and commit memory for heap
196 //
197
198 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
199 initialize_reserved_region(heap_rs);
200 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
201 _heap_region_special = heap_rs.special();
202
203 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
204 "Misaligned heap: " PTR_FORMAT, p2i(base()));
205 os::trace_page_sizes_for_requested_size("Heap",
206 max_byte_size, heap_rs.page_size(), heap_alignment,
207 heap_rs.base(), heap_rs.size());
208
209 #if SHENANDOAH_OPTIMIZED_MARKTASK
210 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
211 // Fail if we ever attempt to address more than we can.
212 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
213 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
214 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
215 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
216 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
217 vm_exit_during_initialization("Fatal Error", buf);
218 }
219 #endif
220
221 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
222 if (!_heap_region_special) {
223 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
224 "Cannot commit heap memory");
225 }
226
227 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
228
229 // Now we know the number of regions and heap sizes, initialize the heuristics.
230 initialize_heuristics();
231
232 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
233
234 //
235 // Worker threads must be initialized after the barrier is configured
236 //
237 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
238 if (_workers == nullptr) {
239 vm_exit_during_initialization("Failed necessary allocation.");
240 } else {
241 _workers->initialize_workers();
242 }
243
244 if (ParallelGCThreads > 1) {
245 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
246 _safepoint_workers->initialize_workers();
247 }
248
249 //
250 // Reserve and commit memory for bitmap(s)
251 //
252
253 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
254 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
255
256 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
257
258 guarantee(bitmap_bytes_per_region != 0,
259 "Bitmap bytes per region should not be zero");
260 guarantee(is_power_of_2(bitmap_bytes_per_region),
261 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
262
263 if (bitmap_page_size > bitmap_bytes_per_region) {
264 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
265 _bitmap_bytes_per_slice = bitmap_page_size;
266 } else {
267 _bitmap_regions_per_slice = 1;
268 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
269 }
270
271 guarantee(_bitmap_regions_per_slice >= 1,
272 "Should have at least one region per slice: " SIZE_FORMAT,
273 _bitmap_regions_per_slice);
274
275 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
276 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
277 _bitmap_bytes_per_slice, bitmap_page_size);
278
279 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
280 os::trace_page_sizes_for_requested_size("Mark Bitmap",
281 bitmap_size_orig, bitmap.page_size(), bitmap_page_size,
282 bitmap.base(),
283 bitmap.size());
284 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
285 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
286 _bitmap_region_special = bitmap.special();
287
288 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
289 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
290 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
291 if (!_bitmap_region_special) {
292 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
293 "Cannot commit bitmap memory");
294 }
295
296 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
297
298 if (ShenandoahVerify) {
299 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
300 os::trace_page_sizes_for_requested_size("Verify Bitmap",
301 bitmap_size_orig, verify_bitmap.page_size(), bitmap_page_size,
302 verify_bitmap.base(),
303 verify_bitmap.size());
304 if (!verify_bitmap.special()) {
305 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
306 "Cannot commit verification bitmap memory");
307 }
308 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
309 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
310 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
311 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
312 }
313
314 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
315 size_t aux_bitmap_page_size = bitmap_page_size;
316 #ifdef LINUX
317 // In THP "advise" mode, we refrain from advising the system to use large pages
318 // since we know these commits will be short lived, and there is no reason to trash
319 // the THP area with this bitmap.
320 if (UseTransparentHugePages) {
321 aux_bitmap_page_size = os::vm_page_size();
322 }
323 #endif
324 ReservedSpace aux_bitmap(_bitmap_size, aux_bitmap_page_size);
325 os::trace_page_sizes_for_requested_size("Aux Bitmap",
326 bitmap_size_orig, aux_bitmap.page_size(), aux_bitmap_page_size,
327 aux_bitmap.base(), aux_bitmap.size());
328 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
329 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
330 _aux_bitmap_region_special = aux_bitmap.special();
331 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
332
333 //
334 // Create regions and region sets
335 //
336 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
337 size_t region_storage_size_orig = region_align * _num_regions;
338 size_t region_storage_size = align_up(region_storage_size_orig,
339 MAX2(region_page_size, os::vm_allocation_granularity()));
340
341 ReservedSpace region_storage(region_storage_size, region_page_size);
342 os::trace_page_sizes_for_requested_size("Region Storage",
343 region_storage_size_orig, region_storage.page_size(), region_page_size,
344 region_storage.base(), region_storage.size());
345 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
346 if (!region_storage.special()) {
347 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
348 "Cannot commit region memory");
349 }
350
351 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
352 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
353 // If not successful, bite a bullet and allocate at whatever address.
354 {
355 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
356 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
357 const size_t cset_page_size = os::vm_page_size();
358
359 uintptr_t min = round_up_power_of_2(cset_align);
360 uintptr_t max = (1u << 30u);
361 ReservedSpace cset_rs;
362
363 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
364 char* req_addr = (char*)addr;
365 assert(is_aligned(req_addr, cset_align), "Should be aligned");
366 cset_rs = ReservedSpace(cset_size, cset_align, cset_page_size, req_addr);
367 if (cset_rs.is_reserved()) {
368 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
369 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
370 break;
371 }
372 }
373
374 if (_collection_set == nullptr) {
375 cset_rs = ReservedSpace(cset_size, cset_align, os::vm_page_size());
376 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
377 }
378 os::trace_page_sizes_for_requested_size("Collection Set",
379 cset_size, cset_rs.page_size(), cset_page_size,
380 cset_rs.base(),
381 cset_rs.size());
382 }
383
384 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
385 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
386 _free_set = new ShenandoahFreeSet(this, _num_regions);
387
388 {
389 ShenandoahHeapLocker locker(lock());
390
391
392 for (size_t i = 0; i < _num_regions; i++) {
393 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
394 bool is_committed = i < num_committed_regions;
395 void* loc = region_storage.base() + i * region_align;
396
397 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
398 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
399
400 _marking_context->initialize_top_at_mark_start(r);
401 _regions[i] = r;
402 assert(!collection_set()->is_in(i), "New region should not be in collection set");
403
404 _affiliations[i] = ShenandoahAffiliation::FREE;
405 }
406
407 // Initialize to complete
408 _marking_context->mark_complete();
409 size_t young_cset_regions, old_cset_regions;
410
411 // We are initializing free set. We ignore cset region tallies.
412 size_t first_old, last_old, num_old;
413 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old, last_old, num_old);
414 _free_set->rebuild(young_cset_regions, old_cset_regions);
415 }
416
417 if (AlwaysPreTouch) {
418 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
419 // before initialize() below zeroes it with initializing thread. For any given region,
420 // we touch the region and the corresponding bitmaps from the same thread.
421 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
422
423 _pretouch_heap_page_size = heap_page_size;
424 _pretouch_bitmap_page_size = bitmap_page_size;
425
426 #ifdef LINUX
427 // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
428 // pages. But, the kernel needs to know that every small page is used, in order to coalesce
429 // them into huge one. Therefore, we need to pretouch with smaller pages.
430 if (UseTransparentHugePages) {
431 _pretouch_heap_page_size = (size_t)os::vm_page_size();
432 _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
433 }
434 #endif
435
436 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
437 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
438
439 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
440 _workers->run_task(&bcl);
441
442 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
443 _workers->run_task(&hcl);
444 }
445
446 //
447 // Initialize the rest of GC subsystems
448 //
449
450 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
451 for (uint worker = 0; worker < _max_workers; worker++) {
452 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
453 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
454 }
455
456 // There should probably be Shenandoah-specific options for these,
457 // just as there are G1-specific options.
458 {
459 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
460 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
461 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
462 }
463
464 _monitoring_support = new ShenandoahMonitoringSupport(this);
465 _phase_timings = new ShenandoahPhaseTimings(max_workers());
466 ShenandoahCodeRoots::initialize();
467
468 if (ShenandoahPacing) {
469 _pacer = new ShenandoahPacer(this);
470 _pacer->setup_for_idle();
471 }
472
473 initialize_controller();
474
475 print_init_logger();
476
477 return JNI_OK;
478 }
479
480 void ShenandoahHeap::initialize_controller() {
481 _control_thread = new ShenandoahControlThread();
482 }
483
484 void ShenandoahHeap::print_init_logger() const {
485 ShenandoahInitLogger::print();
486 }
487
488 void ShenandoahHeap::initialize_mode() {
489 if (ShenandoahGCMode != nullptr) {
490 if (strcmp(ShenandoahGCMode, "satb") == 0) {
491 _gc_mode = new ShenandoahSATBMode();
492 } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
493 _gc_mode = new ShenandoahIUMode();
494 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
495 _gc_mode = new ShenandoahPassiveMode();
496 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
497 _gc_mode = new ShenandoahGenerationalMode();
498 } else {
499 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
500 }
501 } else {
502 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
503 }
504 _gc_mode->initialize_flags();
505 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
506 vm_exit_during_initialization(
507 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
508 _gc_mode->name()));
509 }
510 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
511 vm_exit_during_initialization(
512 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
513 _gc_mode->name()));
514 }
515 }
516
517 void ShenandoahHeap::initialize_heuristics() {
518 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers(), max_capacity(), max_capacity());
519 _global_generation->initialize_heuristics(mode());
520 _evac_tracker = new ShenandoahEvacuationTracker(mode()->is_generational());
521 }
522
523 #ifdef _MSC_VER
524 #pragma warning( push )
525 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
526 #endif
527
528 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
529 CollectedHeap(),
530 _gc_generation(nullptr),
531 _active_generation(nullptr),
532 _initial_size(0),
533 _committed(0),
534 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
535 _workers(nullptr),
536 _safepoint_workers(nullptr),
537 _heap_region_special(false),
538 _num_regions(0),
539 _regions(nullptr),
540 _affiliations(nullptr),
541 _gc_state_changed(false),
542 _gc_no_progress_count(0),
543 _cancel_requested_time(0),
544 _update_refs_iterator(this),
545 _global_generation(nullptr),
546 _control_thread(nullptr),
547 _young_generation(nullptr),
548 _old_generation(nullptr),
549 _shenandoah_policy(policy),
550 _gc_mode(nullptr),
551 _free_set(nullptr),
552 _pacer(nullptr),
553 _verifier(nullptr),
554 _phase_timings(nullptr),
555 _evac_tracker(nullptr),
556 _mmu_tracker(),
557 _monitoring_support(nullptr),
558 _memory_pool(nullptr),
559 _stw_memory_manager("Shenandoah Pauses"),
560 _cycle_memory_manager("Shenandoah Cycles"),
561 _gc_timer(new ConcurrentGCTimer()),
562 _soft_ref_policy(),
563 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
564 _marking_context(nullptr),
565 _bitmap_size(0),
566 _bitmap_regions_per_slice(0),
567 _bitmap_bytes_per_slice(0),
568 _bitmap_region_special(false),
569 _aux_bitmap_region_special(false),
570 _liveness_cache(nullptr),
571 _collection_set(nullptr)
572 {
573 // Initialize GC mode early, many subsequent initialization procedures depend on it
574 initialize_mode();
575 }
576
577 #ifdef _MSC_VER
578 #pragma warning( pop )
579 #endif
580
581 void ShenandoahHeap::print_on(outputStream* st) const {
582 st->print_cr("Shenandoah Heap");
583 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
584 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
585 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
586 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
587 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
588 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
589 num_regions(),
590 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
591 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
592
593 st->print("Status: ");
594 if (has_forwarded_objects()) st->print("has forwarded objects, ");
595 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
596 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
597 if (is_evacuation_in_progress()) st->print("evacuating, ");
598 if (is_update_refs_in_progress()) st->print("updating refs, ");
599 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
600 if (is_full_gc_in_progress()) st->print("full gc, ");
601 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
602 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
603 if (is_concurrent_strong_root_in_progress() &&
604 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
605
606 if (cancelled_gc()) {
607 st->print("cancelled");
608 } else {
609 st->print("not cancelled");
610 }
611 st->cr();
612
613 st->print_cr("Reserved region:");
614 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
615 p2i(reserved_region().start()),
616 p2i(reserved_region().end()));
617
618 ShenandoahCollectionSet* cset = collection_set();
619 st->print_cr("Collection set:");
620 if (cset != nullptr) {
621 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
622 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
623 } else {
624 st->print_cr(" (null)");
625 }
626
627 st->cr();
628 MetaspaceUtils::print_on(st);
629
630 if (Verbose) {
631 st->cr();
632 print_heap_regions_on(st);
633 }
634 }
635
636 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
637 public:
638 void do_thread(Thread* thread) {
639 assert(thread != nullptr, "Sanity");
640 assert(thread->is_Worker_thread(), "Only worker thread expected");
641 ShenandoahThreadLocalData::initialize_gclab(thread);
642 }
643 };
644
645 void ShenandoahHeap::post_initialize() {
646 CollectedHeap::post_initialize();
647 _mmu_tracker.initialize();
648
649 MutexLocker ml(Threads_lock);
650
651 ShenandoahInitWorkerGCLABClosure init_gclabs;
652 _workers->threads_do(&init_gclabs);
653
654 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
655 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
656 _workers->set_initialize_gclab();
657 if (_safepoint_workers != nullptr) {
658 _safepoint_workers->threads_do(&init_gclabs);
659 _safepoint_workers->set_initialize_gclab();
660 }
661
662 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
663 }
664
665 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
666 return _global_generation->heuristics();
667 }
668
669 size_t ShenandoahHeap::used() const {
670 return global_generation()->used();
671 }
672
673 size_t ShenandoahHeap::committed() const {
674 return Atomic::load(&_committed);
675 }
676
677 void ShenandoahHeap::increase_committed(size_t bytes) {
678 shenandoah_assert_heaplocked_or_safepoint();
679 _committed += bytes;
680 }
681
682 void ShenandoahHeap::decrease_committed(size_t bytes) {
683 shenandoah_assert_heaplocked_or_safepoint();
684 _committed -= bytes;
685 }
686
687 // For tracking usage based on allocations, it should be the case that:
688 // * The sum of regions::used == heap::used
689 // * The sum of a generation's regions::used == generation::used
690 // * The sum of a generation's humongous regions::free == generation::humongous_waste
691 // These invariants are checked by the verifier on GC safepoints.
692 //
693 // Additional notes:
694 // * When a mutator's allocation request causes a region to be retired, the
695 // free memory left in that region is considered waste. It does not contribute
696 // to the usage, but it _does_ contribute to allocation rate.
697 // * The bottom of a PLAB must be aligned on card size. In some cases this will
698 // require padding in front of the PLAB (a filler object). Because this padding
699 // is included in the region's used memory we include the padding in the usage
700 // accounting as waste.
701 // * Mutator allocations are used to compute an allocation rate. They are also
702 // sent to the Pacer for those purposes.
703 // * There are three sources of waste:
704 // 1. The padding used to align a PLAB on card size
705 // 2. Region's free is less than minimum TLAB size and is retired
706 // 3. The unused portion of memory in the last region of a humongous object
707 void ShenandoahHeap::increase_used(const ShenandoahAllocRequest& req) {
708 size_t actual_bytes = req.actual_size() * HeapWordSize;
709 size_t wasted_bytes = req.waste() * HeapWordSize;
710 ShenandoahGeneration* generation = generation_for(req.affiliation());
711
712 if (req.is_gc_alloc()) {
713 assert(wasted_bytes == 0 || req.type() == ShenandoahAllocRequest::_alloc_plab, "Only PLABs have waste");
714 increase_used(generation, actual_bytes + wasted_bytes);
715 } else {
716 assert(req.is_mutator_alloc(), "Expected mutator alloc here");
717 // padding and actual size both count towards allocation counter
718 generation->increase_allocated(actual_bytes + wasted_bytes);
719
720 // only actual size counts toward usage for mutator allocations
721 increase_used(generation, actual_bytes);
722
723 // notify pacer of both actual size and waste
724 notify_mutator_alloc_words(req.actual_size(), req.waste());
725
726 if (wasted_bytes > 0 && req.actual_size() > ShenandoahHeapRegion::humongous_threshold_words()) {
727 increase_humongous_waste(generation,wasted_bytes);
728 }
729 }
730 }
731
732 void ShenandoahHeap::increase_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
733 generation->increase_humongous_waste(bytes);
734 if (!generation->is_global()) {
735 global_generation()->increase_humongous_waste(bytes);
736 }
737 }
738
739 void ShenandoahHeap::decrease_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
740 generation->decrease_humongous_waste(bytes);
741 if (!generation->is_global()) {
742 global_generation()->decrease_humongous_waste(bytes);
743 }
744 }
745
746 void ShenandoahHeap::increase_used(ShenandoahGeneration* generation, size_t bytes) {
747 generation->increase_used(bytes);
748 if (!generation->is_global()) {
749 global_generation()->increase_used(bytes);
750 }
751 }
752
753 void ShenandoahHeap::decrease_used(ShenandoahGeneration* generation, size_t bytes) {
754 generation->decrease_used(bytes);
755 if (!generation->is_global()) {
756 global_generation()->decrease_used(bytes);
757 }
758 }
759
760 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, size_t waste) {
761 if (ShenandoahPacing) {
762 control_thread()->pacing_notify_alloc(words);
763 if (waste > 0) {
764 pacer()->claim_for_alloc(waste, true);
765 }
766 }
767 }
768
769 size_t ShenandoahHeap::capacity() const {
770 return committed();
771 }
772
773 size_t ShenandoahHeap::max_capacity() const {
774 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
775 }
776
777 size_t ShenandoahHeap::soft_max_capacity() const {
778 size_t v = Atomic::load(&_soft_max_size);
779 assert(min_capacity() <= v && v <= max_capacity(),
780 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
781 min_capacity(), v, max_capacity());
782 return v;
783 }
784
785 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
786 assert(min_capacity() <= v && v <= max_capacity(),
787 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
788 min_capacity(), v, max_capacity());
789 Atomic::store(&_soft_max_size, v);
790 }
791
792 size_t ShenandoahHeap::min_capacity() const {
793 return _minimum_size;
794 }
795
796 size_t ShenandoahHeap::initial_capacity() const {
797 return _initial_size;
798 }
799
800 void ShenandoahHeap::maybe_uncommit(double shrink_before, size_t shrink_until) {
801 assert (ShenandoahUncommit, "should be enabled");
802
803 // Determine if there is work to do. This avoids taking heap lock if there is
804 // no work available, avoids spamming logs with superfluous logging messages,
805 // and minimises the amount of work while locks are taken.
806
807 if (committed() <= shrink_until) return;
808
809 bool has_work = false;
810 for (size_t i = 0; i < num_regions(); i++) {
811 ShenandoahHeapRegion* r = get_region(i);
812 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
813 has_work = true;
814 break;
815 }
816 }
817
818 if (has_work) {
819 static const char* msg = "Concurrent uncommit";
820 ShenandoahConcurrentPhase gcPhase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
821 EventMark em("%s", msg);
822
823 op_uncommit(shrink_before, shrink_until);
824 }
825 }
826
827 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
828 assert (ShenandoahUncommit, "should be enabled");
829
830 // Application allocates from the beginning of the heap, and GC allocates at
831 // the end of it. It is more efficient to uncommit from the end, so that applications
832 // could enjoy the near committed regions. GC allocations are much less frequent,
833 // and therefore can accept the committing costs.
834
835 size_t count = 0;
836 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
837 ShenandoahHeapRegion* r = get_region(i - 1);
838 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
839 ShenandoahHeapLocker locker(lock());
840 if (r->is_empty_committed()) {
841 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
842 break;
843 }
844
845 r->make_uncommitted();
846 count++;
847 }
848 }
849 SpinPause(); // allow allocators to take the lock
850 }
851
852 if (count > 0) {
853 notify_heap_changed();
854 }
855 }
856
857 bool ShenandoahHeap::check_soft_max_changed() {
858 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
859 size_t old_soft_max = soft_max_capacity();
860 if (new_soft_max != old_soft_max) {
861 new_soft_max = MAX2(min_capacity(), new_soft_max);
862 new_soft_max = MIN2(max_capacity(), new_soft_max);
863 if (new_soft_max != old_soft_max) {
864 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
865 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
866 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
867 );
868 set_soft_max_capacity(new_soft_max);
869 return true;
870 }
871 }
872 return false;
873 }
874
875 void ShenandoahHeap::notify_heap_changed() {
876 // Update monitoring counters when we took a new region. This amortizes the
877 // update costs on slow path.
878 monitoring_support()->notify_heap_changed();
879 _heap_changed.set();
880 }
881
882 void ShenandoahHeap::set_forced_counters_update(bool value) {
883 monitoring_support()->set_forced_counters_update(value);
884 }
885
886 void ShenandoahHeap::handle_force_counters_update() {
887 monitoring_support()->handle_force_counters_update();
888 }
889
890 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
891 // New object should fit the GCLAB size
892 size_t min_size = MAX2(size, PLAB::min_size());
893
894 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
895 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
896
897 new_size = MIN2(new_size, PLAB::max_size());
898 new_size = MAX2(new_size, PLAB::min_size());
899
900 // Record new heuristic value even if we take any shortcut. This captures
901 // the case when moderately-sized objects always take a shortcut. At some point,
902 // heuristics should catch up with them.
903 log_debug(gc, free)("Set new GCLAB size: " SIZE_FORMAT, new_size);
904 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
905
906 if (new_size < size) {
907 // New size still does not fit the object. Fall back to shared allocation.
908 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
909 log_debug(gc, free)("New gclab size (" SIZE_FORMAT ") is too small for " SIZE_FORMAT, new_size, size);
910 return nullptr;
911 }
912
913 // Retire current GCLAB, and allocate a new one.
914 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
915 gclab->retire();
916
917 size_t actual_size = 0;
918 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
919 if (gclab_buf == nullptr) {
920 return nullptr;
921 }
922
923 assert (size <= actual_size, "allocation should fit");
924
925 if (ZeroTLAB) {
926 // ..and clear it.
927 Copy::zero_to_words(gclab_buf, actual_size);
928 } else {
929 // ...and zap just allocated object.
930 #ifdef ASSERT
931 // Skip mangling the space corresponding to the object header to
932 // ensure that the returned space is not considered parsable by
933 // any concurrent GC thread.
934 size_t hdr_size = oopDesc::header_size();
935 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
936 #endif // ASSERT
937 }
938 gclab->set_buf(gclab_buf, actual_size);
939 return gclab->allocate(size);
940 }
941
942 // Called from stubs in JIT code or interpreter
943 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
944 size_t requested_size,
945 size_t* actual_size) {
946 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
947 HeapWord* res = allocate_memory(req);
948 if (res != nullptr) {
949 *actual_size = req.actual_size();
950 } else {
951 *actual_size = 0;
952 }
953 return res;
954 }
955
956 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
957 size_t word_size,
958 size_t* actual_size) {
959 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
960 HeapWord* res = allocate_memory(req);
961 if (res != nullptr) {
962 *actual_size = req.actual_size();
963 } else {
964 *actual_size = 0;
965 }
966 return res;
967 }
968
969 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
970 intptr_t pacer_epoch = 0;
971 bool in_new_region = false;
972 HeapWord* result = nullptr;
973
974 if (req.is_mutator_alloc()) {
975 if (ShenandoahPacing) {
976 pacer()->pace_for_alloc(req.size());
977 pacer_epoch = pacer()->epoch();
978 }
979
980 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
981 result = allocate_memory_under_lock(req, in_new_region);
982 }
983
984 // Check that gc overhead is not exceeded.
985 //
986 // Shenandoah will grind along for quite a while allocating one
987 // object at a time using shared (non-tlab) allocations. This check
988 // is testing that the GC overhead limit has not been exceeded.
989 // This will notify the collector to start a cycle, but will raise
990 // an OOME to the mutator if the last Full GCs have not made progress.
991 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
992 control_thread()->handle_alloc_failure(req, false);
993 return nullptr;
994 }
995
996 // Block until control thread reacted, then retry allocation.
997 //
998 // It might happen that one of the threads requesting allocation would unblock
999 // way later after GC happened, only to fail the second allocation, because
1000 // other threads have already depleted the free storage. In this case, a better
1001 // strategy is to try again, as long as GC makes progress (or until at least
1002 // one full GC has completed).
1003 size_t original_count = shenandoah_policy()->full_gc_count();
1004 while (result == nullptr
1005 && (get_gc_no_progress_count() == 0 || original_count == shenandoah_policy()->full_gc_count())) {
1006 control_thread()->handle_alloc_failure(req, true);
1007 result = allocate_memory_under_lock(req, in_new_region);
1008 }
1009
1010 if (log_is_enabled(Debug, gc, alloc)) {
1011 ResourceMark rm;
1012 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: " SIZE_FORMAT ", Original: " SIZE_FORMAT ", Latest: " SIZE_FORMAT,
1013 Thread::current()->name(), p2i(result), req.type_string(), req.size(), original_count, get_gc_no_progress_count());
1014 }
1015 } else {
1016 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
1017 result = allocate_memory_under_lock(req, in_new_region);
1018 // Do not call handle_alloc_failure() here, because we cannot block.
1019 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1020 }
1021
1022 if (in_new_region) {
1023 notify_heap_changed();
1024 }
1025
1026 if (result == nullptr) {
1027 req.set_actual_size(0);
1028 }
1029
1030 // This is called regardless of the outcome of the allocation to account
1031 // for any waste created by retiring regions with this request.
1032 increase_used(req);
1033
1034 if (result != nullptr) {
1035 size_t requested = req.size();
1036 size_t actual = req.actual_size();
1037
1038 assert (req.is_lab_alloc() || (requested == actual),
1039 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
1040 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
1041
1042 if (req.is_mutator_alloc()) {
1043 // If we requested more than we were granted, give the rest back to pacer.
1044 // This only matters if we are in the same pacing epoch: do not try to unpace
1045 // over the budget for the other phase.
1046 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
1047 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
1048 }
1049 }
1050 }
1051
1052 return result;
1053 }
1054
1055 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1056 // If we are dealing with mutator allocation, then we may need to block for safepoint.
1057 // We cannot block for safepoint for GC allocations, because there is a high chance
1058 // we are already running at safepoint or from stack watermark machinery, and we cannot
1059 // block again.
1060 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1061
1062 // Make sure the old generation has room for either evacuations or promotions before trying to allocate.
1063 if (req.is_old() && !old_generation()->can_allocate(req)) {
1064 return nullptr;
1065 }
1066
1067 // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available
1068 // memory.
1069 HeapWord* result = _free_set->allocate(req, in_new_region);
1070
1071 // Record the plab configuration for this result and register the object.
1072 if (result != nullptr && req.is_old()) {
1073 old_generation()->configure_plab_for_current_thread(req);
1074 if (req.type() == ShenandoahAllocRequest::_alloc_shared_gc) {
1075 // Register the newly allocated object while we're holding the global lock since there's no synchronization
1076 // built in to the implementation of register_object(). There are potential races when multiple independent
1077 // threads are allocating objects, some of which might span the same card region. For example, consider
1078 // a card table's memory region within which three objects are being allocated by three different threads:
1079 //
1080 // objects being "concurrently" allocated:
1081 // [-----a------][-----b-----][--------------c------------------]
1082 // [---- card table memory range --------------]
1083 //
1084 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a
1085 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region.
1086 // Allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region.
1087 // Allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this
1088 // card region.
1089 //
1090 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as
1091 // last-start representing object b while first-start represents object c. This is why we need to require all
1092 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range.
1093 old_generation()->card_scan()->register_object(result);
1094 }
1095 }
1096
1097 return result;
1098 }
1099
1100 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1101 bool* gc_overhead_limit_was_exceeded) {
1102 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1103 return allocate_memory(req);
1104 }
1105
1106 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1107 size_t size,
1108 Metaspace::MetadataType mdtype) {
1109 MetaWord* result;
1110
1111 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1112 ShenandoahHeuristics* h = global_generation()->heuristics();
1113 if (h->can_unload_classes()) {
1114 h->record_metaspace_oom();
1115 }
1116
1117 // Expand and retry allocation
1118 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1119 if (result != nullptr) {
1120 return result;
1121 }
1122
1123 // Start full GC
1124 collect(GCCause::_metadata_GC_clear_soft_refs);
1125
1126 // Retry allocation
1127 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1128 if (result != nullptr) {
1129 return result;
1130 }
1131
1132 // Expand and retry allocation
1133 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1134 if (result != nullptr) {
1135 return result;
1136 }
1137
1138 // Out of memory
1139 return nullptr;
1140 }
1141
1142 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1143 private:
1144 ShenandoahHeap* const _heap;
1145 Thread* const _thread;
1146 public:
1147 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1148 _heap(heap), _thread(Thread::current()) {}
1149
1150 void do_object(oop p) {
1151 shenandoah_assert_marked(nullptr, p);
1152 if (!p->is_forwarded()) {
1153 _heap->evacuate_object(p, _thread);
1154 }
1155 }
1156 };
1157
1158 class ShenandoahEvacuationTask : public WorkerTask {
1159 private:
1160 ShenandoahHeap* const _sh;
1161 ShenandoahCollectionSet* const _cs;
1162 bool _concurrent;
1163 public:
1164 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1165 ShenandoahCollectionSet* cs,
1166 bool concurrent) :
1167 WorkerTask("Shenandoah Evacuation"),
1168 _sh(sh),
1169 _cs(cs),
1170 _concurrent(concurrent)
1171 {}
1172
1173 void work(uint worker_id) {
1174 if (_concurrent) {
1175 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1176 ShenandoahSuspendibleThreadSetJoiner stsj;
1177 ShenandoahEvacOOMScope oom_evac_scope;
1178 do_work();
1179 } else {
1180 ShenandoahParallelWorkerSession worker_session(worker_id);
1181 ShenandoahEvacOOMScope oom_evac_scope;
1182 do_work();
1183 }
1184 }
1185
1186 private:
1187 void do_work() {
1188 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1189 ShenandoahHeapRegion* r;
1190 while ((r =_cs->claim_next()) != nullptr) {
1191 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1192 _sh->marked_object_iterate(r, &cl);
1193
1194 if (ShenandoahPacing) {
1195 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1196 }
1197
1198 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1199 break;
1200 }
1201 }
1202 }
1203 };
1204
1205 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1206 if (mode()->is_generational()) {
1207 ShenandoahRegionIterator regions;
1208 ShenandoahGenerationalEvacuationTask task(ShenandoahGenerationalHeap::heap(), ®ions, concurrent);
1209 workers()->run_task(&task);
1210 } else {
1211 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1212 workers()->run_task(&task);
1213 }
1214 }
1215
1216 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1217 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1218 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
1219 // This thread went through the OOM during evac protocol. It is safe to return
1220 // the forward pointer. It must not attempt to evacuate any other objects.
1221 return ShenandoahBarrierSet::resolve_forwarded(p);
1222 }
1223
1224 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1225
1226 ShenandoahHeapRegion* r = heap_region_containing(p);
1227 assert(!r->is_humongous(), "never evacuate humongous objects");
1228
1229 ShenandoahAffiliation target_gen = r->affiliation();
1230 return try_evacuate_object(p, thread, r, target_gen);
1231 }
1232
1233 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1234 ShenandoahAffiliation target_gen) {
1235 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1236 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1237 bool alloc_from_lab = true;
1238 HeapWord* copy = nullptr;
1239 size_t size = p->size();
1240
1241 #ifdef ASSERT
1242 if (ShenandoahOOMDuringEvacALot &&
1243 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1244 copy = nullptr;
1245 } else {
1246 #endif
1247 if (UseTLAB) {
1248 copy = allocate_from_gclab(thread, size);
1249 if ((copy == nullptr) && (size < ShenandoahThreadLocalData::gclab_size(thread))) {
1250 // GCLAB allocation failed because we are bumping up against the limit on young evacuation reserve. Try resetting
1251 // the desired GCLAB size and retry GCLAB allocation to avoid cascading of shared memory allocations.
1252 // TODO: is this right? using PLAB::min_size() here for gc lab size?
1253 ShenandoahThreadLocalData::set_gclab_size(thread, PLAB::min_size());
1254 copy = allocate_from_gclab(thread, size);
1255 // If we still get nullptr, we'll try a shared allocation below.
1256 }
1257 }
1258
1259 if (copy == nullptr) {
1260 // If we failed to allocate in LAB, we'll try a shared allocation.
1261 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1262 copy = allocate_memory(req);
1263 alloc_from_lab = false;
1264 }
1265 #ifdef ASSERT
1266 }
1267 #endif
1268
1269 if (copy == nullptr) {
1270 control_thread()->handle_alloc_failure_evac(size);
1271
1272 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1273
1274 return ShenandoahBarrierSet::resolve_forwarded(p);
1275 }
1276
1277 // Copy the object:
1278 _evac_tracker->begin_evacuation(thread, size * HeapWordSize);
1279 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1280
1281 oop copy_val = cast_to_oop(copy);
1282
1283 // Try to install the new forwarding pointer.
1284 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1285
1286 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1287 if (result == copy_val) {
1288 // Successfully evacuated. Our copy is now the public one!
1289 _evac_tracker->end_evacuation(thread, size * HeapWordSize);
1290 shenandoah_assert_correct(nullptr, copy_val);
1291 return copy_val;
1292 } else {
1293 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1294 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1295 // But if it happens to contain references to evacuated regions, those references would
1296 // not get updated for this stale copy during this cycle, and we will crash while scanning
1297 // it the next cycle.
1298 if (alloc_from_lab) {
1299 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1300 // object will overwrite this stale copy, or the filler object on LAB retirement will
1301 // do this.
1302 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1303 } else {
1304 // For non-LAB allocations, we have no way to retract the allocation, and
1305 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1306 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1307 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1308 fill_with_object(copy, size);
1309 shenandoah_assert_correct(nullptr, copy_val);
1310 // For non-LAB allocations, the object has already been registered
1311 }
1312 shenandoah_assert_correct(nullptr, result);
1313 return result;
1314 }
1315 }
1316
1317 void ShenandoahHeap::trash_cset_regions() {
1318 ShenandoahHeapLocker locker(lock());
1319
1320 ShenandoahCollectionSet* set = collection_set();
1321 ShenandoahHeapRegion* r;
1322 set->clear_current_index();
1323 while ((r = set->next()) != nullptr) {
1324 r->make_trash();
1325 }
1326 collection_set()->clear();
1327 }
1328
1329 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1330 st->print_cr("Heap Regions:");
1331 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1332 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1333 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1334 st->print_cr("UWM=update watermark, U=used");
1335 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1336 st->print_cr("S=shared allocs, L=live data");
1337 st->print_cr("CP=critical pins");
1338
1339 for (size_t i = 0; i < num_regions(); i++) {
1340 get_region(i)->print_on(st);
1341 }
1342 }
1343
1344 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1345 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1346
1347 oop humongous_obj = cast_to_oop(start->bottom());
1348 size_t size = humongous_obj->size();
1349 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1350 size_t index = start->index() + required_regions - 1;
1351
1352 assert(!start->has_live(), "liveness must be zero");
1353
1354 for(size_t i = 0; i < required_regions; i++) {
1355 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1356 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1357 ShenandoahHeapRegion* region = get_region(index --);
1358
1359 assert(region->is_humongous(), "expect correct humongous start or continuation");
1360 assert(!region->is_cset(), "Humongous region should not be in collection set");
1361
1362 region->make_trash_immediate();
1363 }
1364 return required_regions;
1365 }
1366
1367 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1368 public:
1369 ShenandoahCheckCleanGCLABClosure() {}
1370 void do_thread(Thread* thread) {
1371 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1372 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1373 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1374
1375 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1376 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1377 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1378 assert(plab->words_remaining() == 0, "PLAB should not need retirement");
1379 }
1380 }
1381 };
1382
1383 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1384 private:
1385 bool const _resize;
1386 public:
1387 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1388 void do_thread(Thread* thread) {
1389 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1390 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1391 gclab->retire();
1392 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1393 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1394 }
1395
1396 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1397 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1398 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1399
1400 // There are two reasons to retire all plabs between old-gen evacuation passes.
1401 // 1. We need to make the plab memory parsable by remembered-set scanning.
1402 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1403 ShenandoahGenerationalHeap::heap()->retire_plab(plab, thread);
1404 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) {
1405 ShenandoahThreadLocalData::set_plab_size(thread, 0);
1406 }
1407 }
1408 }
1409 };
1410
1411 void ShenandoahHeap::labs_make_parsable() {
1412 assert(UseTLAB, "Only call with UseTLAB");
1413
1414 ShenandoahRetireGCLABClosure cl(false);
1415
1416 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1417 ThreadLocalAllocBuffer& tlab = t->tlab();
1418 tlab.make_parsable();
1419 cl.do_thread(t);
1420 }
1421
1422 workers()->threads_do(&cl);
1423 }
1424
1425 void ShenandoahHeap::tlabs_retire(bool resize) {
1426 assert(UseTLAB, "Only call with UseTLAB");
1427 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1428
1429 ThreadLocalAllocStats stats;
1430
1431 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1432 ThreadLocalAllocBuffer& tlab = t->tlab();
1433 tlab.retire(&stats);
1434 if (resize) {
1435 tlab.resize();
1436 }
1437 }
1438
1439 stats.publish();
1440
1441 #ifdef ASSERT
1442 ShenandoahCheckCleanGCLABClosure cl;
1443 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1444 cl.do_thread(t);
1445 }
1446 workers()->threads_do(&cl);
1447 #endif
1448 }
1449
1450 void ShenandoahHeap::gclabs_retire(bool resize) {
1451 assert(UseTLAB, "Only call with UseTLAB");
1452 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1453
1454 ShenandoahRetireGCLABClosure cl(resize);
1455 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1456 cl.do_thread(t);
1457 }
1458 workers()->threads_do(&cl);
1459
1460 if (safepoint_workers() != nullptr) {
1461 safepoint_workers()->threads_do(&cl);
1462 }
1463 }
1464
1465 // Returns size in bytes
1466 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1467 // Return the max allowed size, and let the allocation path
1468 // figure out the safe size for current allocation.
1469 return ShenandoahHeapRegion::max_tlab_size_bytes();
1470 }
1471
1472 size_t ShenandoahHeap::max_tlab_size() const {
1473 // Returns size in words
1474 return ShenandoahHeapRegion::max_tlab_size_words();
1475 }
1476
1477 void ShenandoahHeap::collect(GCCause::Cause cause) {
1478 control_thread()->request_gc(cause);
1479 }
1480
1481 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1482 //assert(false, "Shouldn't need to do full collections");
1483 }
1484
1485 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1486 ShenandoahHeapRegion* r = heap_region_containing(addr);
1487 if (r != nullptr) {
1488 return r->block_start(addr);
1489 }
1490 return nullptr;
1491 }
1492
1493 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1494 ShenandoahHeapRegion* r = heap_region_containing(addr);
1495 return r->block_is_obj(addr);
1496 }
1497
1498 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1499 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1500 }
1501
1502 void ShenandoahHeap::prepare_for_verify() {
1503 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1504 labs_make_parsable();
1505 }
1506 }
1507
1508 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1509 if (_shenandoah_policy->is_at_shutdown()) {
1510 return;
1511 }
1512
1513 if (_control_thread != nullptr) {
1514 tcl->do_thread(_control_thread);
1515 }
1516
1517 workers()->threads_do(tcl);
1518 if (_safepoint_workers != nullptr) {
1519 _safepoint_workers->threads_do(tcl);
1520 }
1521 }
1522
1523 void ShenandoahHeap::print_tracing_info() const {
1524 LogTarget(Info, gc, stats) lt;
1525 if (lt.is_enabled()) {
1526 ResourceMark rm;
1527 LogStream ls(lt);
1528
1529 phase_timings()->print_global_on(&ls);
1530
1531 ls.cr();
1532 ls.cr();
1533
1534 shenandoah_policy()->print_gc_stats(&ls);
1535
1536 ls.cr();
1537
1538 evac_tracker()->print_global_on(&ls);
1539
1540 ls.cr();
1541 ls.cr();
1542 }
1543 }
1544
1545 void ShenandoahHeap::set_gc_generation(ShenandoahGeneration* generation) {
1546 shenandoah_assert_control_or_vm_thread_at_safepoint();
1547 _gc_generation = generation;
1548 }
1549
1550 // Active generation may only be set by the VM thread at a safepoint.
1551 void ShenandoahHeap::set_active_generation() {
1552 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1553 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1554 assert(_gc_generation != nullptr, "Will set _active_generation to nullptr");
1555 _active_generation = _gc_generation;
1556 }
1557
1558 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
1559 shenandoah_policy()->record_collection_cause(cause);
1560
1561 assert(gc_cause() == GCCause::_no_gc, "Over-writing cause");
1562 assert(_gc_generation == nullptr, "Over-writing _gc_generation");
1563
1564 set_gc_cause(cause);
1565 set_gc_generation(generation);
1566
1567 generation->heuristics()->record_cycle_start();
1568 }
1569
1570 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1571 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1572 assert(_gc_generation != nullptr, "_gc_generation wasn't set");
1573
1574 generation->heuristics()->record_cycle_end();
1575 if (mode()->is_generational() && generation->is_global()) {
1576 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1577 young_generation()->heuristics()->record_cycle_end();
1578 old_generation()->heuristics()->record_cycle_end();
1579 }
1580
1581 set_gc_generation(nullptr);
1582 set_gc_cause(GCCause::_no_gc);
1583 }
1584
1585 void ShenandoahHeap::verify(VerifyOption vo) {
1586 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1587 if (ShenandoahVerify) {
1588 verifier()->verify_generic(vo);
1589 } else {
1590 // TODO: Consider allocating verification bitmaps on demand,
1591 // and turn this on unconditionally.
1592 }
1593 }
1594 }
1595 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1596 return _free_set->capacity();
1597 }
1598
1599 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1600 private:
1601 MarkBitMap* _bitmap;
1602 ShenandoahScanObjectStack* _oop_stack;
1603 ShenandoahHeap* const _heap;
1604 ShenandoahMarkingContext* const _marking_context;
1605
1606 template <class T>
1607 void do_oop_work(T* p) {
1608 T o = RawAccess<>::oop_load(p);
1609 if (!CompressedOops::is_null(o)) {
1610 oop obj = CompressedOops::decode_not_null(o);
1611 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1612 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1613 return;
1614 }
1615 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1616
1617 assert(oopDesc::is_oop(obj), "must be a valid oop");
1618 if (!_bitmap->is_marked(obj)) {
1619 _bitmap->mark(obj);
1620 _oop_stack->push(obj);
1621 }
1622 }
1623 }
1624 public:
1625 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1626 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1627 _marking_context(_heap->marking_context()) {}
1628 void do_oop(oop* p) { do_oop_work(p); }
1629 void do_oop(narrowOop* p) { do_oop_work(p); }
1630 };
1631
1632 /*
1633 * This is public API, used in preparation of object_iterate().
1634 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1635 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1636 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1637 */
1638 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1639 // No-op.
1640 }
1641
1642 /*
1643 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1644 *
1645 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1646 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1647 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1648 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1649 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1650 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1651 * wiped the bitmap in preparation for next marking).
1652 *
1653 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1654 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1655 * is allowed to report dead objects, but is not required to do so.
1656 */
1657 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1658 // Reset bitmap
1659 if (!prepare_aux_bitmap_for_iteration())
1660 return;
1661
1662 ShenandoahScanObjectStack oop_stack;
1663 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1664 // Seed the stack with root scan
1665 scan_roots_for_iteration(&oop_stack, &oops);
1666
1667 // Work through the oop stack to traverse heap
1668 while (! oop_stack.is_empty()) {
1669 oop obj = oop_stack.pop();
1670 assert(oopDesc::is_oop(obj), "must be a valid oop");
1671 cl->do_object(obj);
1672 obj->oop_iterate(&oops);
1673 }
1674
1675 assert(oop_stack.is_empty(), "should be empty");
1676 // Reclaim bitmap
1677 reclaim_aux_bitmap_for_iteration();
1678 }
1679
1680 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1681 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1682
1683 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1684 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1685 return false;
1686 }
1687 // Reset bitmap
1688 _aux_bit_map.clear();
1689 return true;
1690 }
1691
1692 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1693 // Process GC roots according to current GC cycle
1694 // This populates the work stack with initial objects
1695 // It is important to relinquish the associated locks before diving
1696 // into heap dumper
1697 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1698 ShenandoahHeapIterationRootScanner rp(n_workers);
1699 rp.roots_do(oops);
1700 }
1701
1702 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1703 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1704 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1705 }
1706 }
1707
1708 // Closure for parallelly iterate objects
1709 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1710 private:
1711 MarkBitMap* _bitmap;
1712 ShenandoahObjToScanQueue* _queue;
1713 ShenandoahHeap* const _heap;
1714 ShenandoahMarkingContext* const _marking_context;
1715
1716 template <class T>
1717 void do_oop_work(T* p) {
1718 T o = RawAccess<>::oop_load(p);
1719 if (!CompressedOops::is_null(o)) {
1720 oop obj = CompressedOops::decode_not_null(o);
1721 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1722 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1723 return;
1724 }
1725 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1726
1727 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1728 if (_bitmap->par_mark(obj)) {
1729 _queue->push(ShenandoahMarkTask(obj));
1730 }
1731 }
1732 }
1733 public:
1734 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1735 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1736 _marking_context(_heap->marking_context()) {}
1737 void do_oop(oop* p) { do_oop_work(p); }
1738 void do_oop(narrowOop* p) { do_oop_work(p); }
1739 };
1740
1741 // Object iterator for parallel heap iteraion.
1742 // The root scanning phase happenes in construction as a preparation of
1743 // parallel marking queues.
1744 // Every worker processes it's own marking queue. work-stealing is used
1745 // to balance workload.
1746 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1747 private:
1748 uint _num_workers;
1749 bool _init_ready;
1750 MarkBitMap* _aux_bit_map;
1751 ShenandoahHeap* _heap;
1752 ShenandoahScanObjectStack _roots_stack; // global roots stack
1753 ShenandoahObjToScanQueueSet* _task_queues;
1754 public:
1755 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1756 _num_workers(num_workers),
1757 _init_ready(false),
1758 _aux_bit_map(bitmap),
1759 _heap(ShenandoahHeap::heap()) {
1760 // Initialize bitmap
1761 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1762 if (!_init_ready) {
1763 return;
1764 }
1765
1766 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1767 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1768
1769 _init_ready = prepare_worker_queues();
1770 }
1771
1772 ~ShenandoahParallelObjectIterator() {
1773 // Reclaim bitmap
1774 _heap->reclaim_aux_bitmap_for_iteration();
1775 // Reclaim queue for workers
1776 if (_task_queues!= nullptr) {
1777 for (uint i = 0; i < _num_workers; ++i) {
1778 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1779 if (q != nullptr) {
1780 delete q;
1781 _task_queues->register_queue(i, nullptr);
1782 }
1783 }
1784 delete _task_queues;
1785 _task_queues = nullptr;
1786 }
1787 }
1788
1789 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1790 if (_init_ready) {
1791 object_iterate_parallel(cl, worker_id, _task_queues);
1792 }
1793 }
1794
1795 private:
1796 // Divide global root_stack into worker queues
1797 bool prepare_worker_queues() {
1798 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1799 // Initialize queues for every workers
1800 for (uint i = 0; i < _num_workers; ++i) {
1801 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1802 _task_queues->register_queue(i, task_queue);
1803 }
1804 // Divide roots among the workers. Assume that object referencing distribution
1805 // is related with root kind, use round-robin to make every worker have same chance
1806 // to process every kind of roots
1807 size_t roots_num = _roots_stack.size();
1808 if (roots_num == 0) {
1809 // No work to do
1810 return false;
1811 }
1812
1813 for (uint j = 0; j < roots_num; j++) {
1814 uint stack_id = j % _num_workers;
1815 oop obj = _roots_stack.pop();
1816 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1817 }
1818 return true;
1819 }
1820
1821 void object_iterate_parallel(ObjectClosure* cl,
1822 uint worker_id,
1823 ShenandoahObjToScanQueueSet* queue_set) {
1824 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1825 assert(queue_set != nullptr, "task queue must not be null");
1826
1827 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1828 assert(q != nullptr, "object iterate queue must not be null");
1829
1830 ShenandoahMarkTask t;
1831 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1832
1833 // Work through the queue to traverse heap.
1834 // Steal when there is no task in queue.
1835 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1836 oop obj = t.obj();
1837 assert(oopDesc::is_oop(obj), "must be a valid oop");
1838 cl->do_object(obj);
1839 obj->oop_iterate(&oops);
1840 }
1841 assert(q->is_empty(), "should be empty");
1842 }
1843 };
1844
1845 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1846 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1847 }
1848
1849 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1850 void ShenandoahHeap::keep_alive(oop obj) {
1851 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1852 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1853 }
1854 }
1855
1856 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1857 for (size_t i = 0; i < num_regions(); i++) {
1858 ShenandoahHeapRegion* current = get_region(i);
1859 blk->heap_region_do(current);
1860 }
1861 }
1862
1863 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1864 private:
1865 ShenandoahHeap* const _heap;
1866 ShenandoahHeapRegionClosure* const _blk;
1867
1868 shenandoah_padding(0);
1869 volatile size_t _index;
1870 shenandoah_padding(1);
1871
1872 public:
1873 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1874 WorkerTask("Shenandoah Parallel Region Operation"),
1875 _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1876
1877 void work(uint worker_id) {
1878 ShenandoahParallelWorkerSession worker_session(worker_id);
1879 size_t stride = ShenandoahParallelRegionStride;
1880
1881 size_t max = _heap->num_regions();
1882 while (Atomic::load(&_index) < max) {
1883 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1884 size_t start = cur;
1885 size_t end = MIN2(cur + stride, max);
1886 if (start >= max) break;
1887
1888 for (size_t i = cur; i < end; i++) {
1889 ShenandoahHeapRegion* current = _heap->get_region(i);
1890 _blk->heap_region_do(current);
1891 }
1892 }
1893 }
1894 };
1895
1896 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1897 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1898 if (num_regions() > ShenandoahParallelRegionStride) {
1899 ShenandoahParallelHeapRegionTask task(blk);
1900 workers()->run_task(&task);
1901 } else {
1902 heap_region_iterate(blk);
1903 }
1904 }
1905
1906 class ShenandoahRendezvousClosure : public HandshakeClosure {
1907 public:
1908 inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
1909 inline void do_thread(Thread* thread) {}
1910 };
1911
1912 void ShenandoahHeap::rendezvous_threads() {
1913 ShenandoahRendezvousClosure cl;
1914 Handshake::execute(&cl);
1915 }
1916
1917 void ShenandoahHeap::recycle_trash() {
1918 free_set()->recycle_trash();
1919 }
1920
1921 void ShenandoahHeap::do_class_unloading() {
1922 _unloader.unload();
1923 if (mode()->is_generational()) {
1924 old_generation()->set_parseable(false);
1925 }
1926 }
1927
1928 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1929 // Weak refs processing
1930 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1931 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1932 ShenandoahTimingsTracker t(phase);
1933 ShenandoahGCWorkerPhase worker_phase(phase);
1934 shenandoah_assert_generations_reconciled();
1935 gc_generation()->ref_processor()->process_references(phase, workers(), false /* concurrent */);
1936 }
1937
1938 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1939 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1940
1941 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1942 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1943 // for future GCLABs here.
1944 if (UseTLAB) {
1945 ShenandoahGCPhase phase(concurrent ?
1946 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1947 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1948 gclabs_retire(ResizeTLAB);
1949 }
1950
1951 _update_refs_iterator.reset();
1952 }
1953
1954 void ShenandoahHeap::propagate_gc_state_to_java_threads() {
1955 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1956 if (_gc_state_changed) {
1957 _gc_state_changed = false;
1958 char state = gc_state();
1959 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1960 ShenandoahThreadLocalData::set_gc_state(t, state);
1961 }
1962 }
1963 }
1964
1965 void ShenandoahHeap::set_gc_state(uint mask, bool value) {
1966 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1967 _gc_state.set_cond(mask, value);
1968 _gc_state_changed = true;
1969 // Check that if concurrent weak root is set then active_gen isn't null
1970 assert(!is_concurrent_weak_root_in_progress() || active_generation() != nullptr, "Error");
1971 shenandoah_assert_generations_reconciled();
1972 }
1973
1974 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
1975 uint mask;
1976 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
1977 if (!in_progress && is_concurrent_old_mark_in_progress()) {
1978 assert(mode()->is_generational(), "Only generational GC has old marking");
1979 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
1980 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
1981 mask = YOUNG_MARKING;
1982 } else {
1983 mask = MARKING | YOUNG_MARKING;
1984 }
1985 set_gc_state(mask, in_progress);
1986 manage_satb_barrier(in_progress);
1987 }
1988
1989 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
1990 #ifdef ASSERT
1991 // has_forwarded_objects() iff UPDATEREFS or EVACUATION
1992 bool has_forwarded = has_forwarded_objects();
1993 bool updating_or_evacuating = _gc_state.is_set(UPDATEREFS | EVACUATION);
1994 bool evacuating = _gc_state.is_set(EVACUATION);
1995 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
1996 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
1997 #endif
1998 if (!in_progress && is_concurrent_young_mark_in_progress()) {
1999 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2000 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2001 set_gc_state(OLD_MARKING, in_progress);
2002 } else {
2003 set_gc_state(MARKING | OLD_MARKING, in_progress);
2004 }
2005 manage_satb_barrier(in_progress);
2006 }
2007
2008 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2009 return old_generation()->is_preparing_for_mark();
2010 }
2011
2012 void ShenandoahHeap::manage_satb_barrier(bool active) {
2013 if (is_concurrent_mark_in_progress()) {
2014 // Ignore request to deactivate barrier while concurrent mark is in progress.
2015 // Do not attempt to re-activate the barrier if it is already active.
2016 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2017 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2018 }
2019 } else {
2020 // No concurrent marking is in progress so honor request to deactivate,
2021 // but only if the barrier is already active.
2022 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2023 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2024 }
2025 }
2026 }
2027
2028 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2029 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2030 set_gc_state(EVACUATION, in_progress);
2031 }
2032
2033 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2034 if (in_progress) {
2035 _concurrent_strong_root_in_progress.set();
2036 } else {
2037 _concurrent_strong_root_in_progress.unset();
2038 }
2039 }
2040
2041 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2042 set_gc_state(WEAK_ROOTS, cond);
2043 }
2044
2045 GCTracer* ShenandoahHeap::tracer() {
2046 return shenandoah_policy()->tracer();
2047 }
2048
2049 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2050 return _free_set->used();
2051 }
2052
2053 bool ShenandoahHeap::try_cancel_gc() {
2054 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
2055 return prev == CANCELLABLE;
2056 }
2057
2058 void ShenandoahHeap::cancel_concurrent_mark() {
2059 if (mode()->is_generational()) {
2060 young_generation()->cancel_marking();
2061 old_generation()->cancel_marking();
2062 }
2063
2064 global_generation()->cancel_marking();
2065
2066 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2067 }
2068
2069 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2070 if (try_cancel_gc()) {
2071 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2072 log_info(gc)("%s", msg.buffer());
2073 Events::log(Thread::current(), "%s", msg.buffer());
2074 _cancel_requested_time = os::elapsedTime();
2075 }
2076 }
2077
2078 uint ShenandoahHeap::max_workers() {
2079 return _max_workers;
2080 }
2081
2082 void ShenandoahHeap::stop() {
2083 // The shutdown sequence should be able to terminate when GC is running.
2084
2085 // Step 0. Notify policy to disable event recording.
2086 _shenandoah_policy->record_shutdown();
2087
2088 // Step 1. Notify control thread that we are in shutdown.
2089 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
2090 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
2091 control_thread()->prepare_for_graceful_shutdown();
2092
2093 // Step 2. Notify GC workers that we are cancelling GC.
2094 cancel_gc(GCCause::_shenandoah_stop_vm);
2095
2096 // Step 3. Wait until GC worker exits normally.
2097 control_thread()->stop();
2098 }
2099
2100 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2101 if (!unload_classes()) return;
2102 ClassUnloadingContext ctx(_workers->active_workers(),
2103 true /* unregister_nmethods_during_purge */,
2104 false /* lock_codeblob_free_separately */);
2105
2106 // Unload classes and purge SystemDictionary.
2107 {
2108 ShenandoahPhaseTimings::Phase phase = full_gc ?
2109 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2110 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2111 ShenandoahIsAliveSelector is_alive;
2112 {
2113 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2114 ShenandoahGCPhase gc_phase(phase);
2115 ShenandoahGCWorkerPhase worker_phase(phase);
2116 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2117
2118 uint num_workers = _workers->active_workers();
2119 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
2120 _workers->run_task(&unlink_task);
2121 }
2122 // Release unloaded nmethods's memory.
2123 ClassUnloadingContext::context()->purge_and_free_nmethods();
2124 }
2125
2126 {
2127 ShenandoahGCPhase phase(full_gc ?
2128 ShenandoahPhaseTimings::full_gc_purge_cldg :
2129 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2130 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2131 }
2132 // Resize and verify metaspace
2133 MetaspaceGC::compute_new_size();
2134 DEBUG_ONLY(MetaspaceUtils::verify();)
2135 }
2136
2137 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
2138 // so they should not have forwarded oops.
2139 // However, we do need to "null" dead oops in the roots, if can not be done
2140 // in concurrent cycles.
2141 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2142 uint num_workers = _workers->active_workers();
2143 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2144 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2145 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2146 ShenandoahGCPhase phase(timing_phase);
2147 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2148 // Cleanup weak roots
2149 if (has_forwarded_objects()) {
2150 ShenandoahForwardedIsAliveClosure is_alive;
2151 ShenandoahUpdateRefsClosure keep_alive;
2152 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
2153 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2154 _workers->run_task(&cleaning_task);
2155 } else {
2156 ShenandoahIsAliveClosure is_alive;
2157 #ifdef ASSERT
2158 ShenandoahAssertNotForwardedClosure verify_cl;
2159 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2160 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2161 #else
2162 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2163 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2164 #endif
2165 _workers->run_task(&cleaning_task);
2166 }
2167 }
2168
2169 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2170 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2171 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2172 ShenandoahGCPhase phase(full_gc ?
2173 ShenandoahPhaseTimings::full_gc_purge :
2174 ShenandoahPhaseTimings::degen_gc_purge);
2175 stw_weak_refs(full_gc);
2176 stw_process_weak_roots(full_gc);
2177 stw_unload_classes(full_gc);
2178 }
2179
2180 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2181 set_gc_state(HAS_FORWARDED, cond);
2182 }
2183
2184 void ShenandoahHeap::set_unload_classes(bool uc) {
2185 _unload_classes.set_cond(uc);
2186 }
2187
2188 bool ShenandoahHeap::unload_classes() const {
2189 return _unload_classes.is_set();
2190 }
2191
2192 address ShenandoahHeap::in_cset_fast_test_addr() {
2193 ShenandoahHeap* heap = ShenandoahHeap::heap();
2194 assert(heap->collection_set() != nullptr, "Sanity");
2195 return (address) heap->collection_set()->biased_map_address();
2196 }
2197
2198 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2199 if (mode()->is_generational()) {
2200 young_generation()->reset_bytes_allocated_since_gc_start();
2201 old_generation()->reset_bytes_allocated_since_gc_start();
2202 }
2203
2204 global_generation()->reset_bytes_allocated_since_gc_start();
2205 }
2206
2207 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2208 _degenerated_gc_in_progress.set_cond(in_progress);
2209 }
2210
2211 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2212 _full_gc_in_progress.set_cond(in_progress);
2213 }
2214
2215 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2216 assert (is_full_gc_in_progress(), "should be");
2217 _full_gc_move_in_progress.set_cond(in_progress);
2218 }
2219
2220 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2221 set_gc_state(UPDATEREFS, in_progress);
2222 }
2223
2224 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2225 ShenandoahCodeRoots::register_nmethod(nm);
2226 }
2227
2228 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2229 ShenandoahCodeRoots::unregister_nmethod(nm);
2230 }
2231
2232 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2233 heap_region_containing(o)->record_pin();
2234 }
2235
2236 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2237 ShenandoahHeapRegion* r = heap_region_containing(o);
2238 assert(r != nullptr, "Sanity");
2239 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
2240 r->record_unpin();
2241 }
2242
2243 void ShenandoahHeap::sync_pinned_region_status() {
2244 ShenandoahHeapLocker locker(lock());
2245
2246 for (size_t i = 0; i < num_regions(); i++) {
2247 ShenandoahHeapRegion *r = get_region(i);
2248 if (r->is_active()) {
2249 if (r->is_pinned()) {
2250 if (r->pin_count() == 0) {
2251 r->make_unpinned();
2252 }
2253 } else {
2254 if (r->pin_count() > 0) {
2255 r->make_pinned();
2256 }
2257 }
2258 }
2259 }
2260
2261 assert_pinned_region_status();
2262 }
2263
2264 #ifdef ASSERT
2265 void ShenandoahHeap::assert_pinned_region_status() {
2266 for (size_t i = 0; i < num_regions(); i++) {
2267 ShenandoahHeapRegion* r = get_region(i);
2268 shenandoah_assert_generations_reconciled();
2269 if (gc_generation()->contains(r)) {
2270 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2271 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2272 }
2273 }
2274 }
2275 #endif
2276
2277 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2278 return _gc_timer;
2279 }
2280
2281 void ShenandoahHeap::prepare_concurrent_roots() {
2282 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2283 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2284 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2285 set_concurrent_weak_root_in_progress(true);
2286 if (unload_classes()) {
2287 _unloader.prepare();
2288 }
2289 }
2290
2291 void ShenandoahHeap::finish_concurrent_roots() {
2292 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2293 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2294 if (unload_classes()) {
2295 _unloader.finish();
2296 }
2297 }
2298
2299 #ifdef ASSERT
2300 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2301 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2302
2303 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2304 // Use ParallelGCThreads inside safepoints
2305 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2306 ParallelGCThreads, nworkers);
2307 } else {
2308 // Use ConcGCThreads outside safepoints
2309 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2310 ConcGCThreads, nworkers);
2311 }
2312 }
2313 #endif
2314
2315 ShenandoahVerifier* ShenandoahHeap::verifier() {
2316 guarantee(ShenandoahVerify, "Should be enabled");
2317 assert (_verifier != nullptr, "sanity");
2318 return _verifier;
2319 }
2320
2321 template<bool CONCURRENT>
2322 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2323 private:
2324 ShenandoahHeap* _heap;
2325 ShenandoahRegionIterator* _regions;
2326 public:
2327 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2328 WorkerTask("Shenandoah Update References"),
2329 _heap(ShenandoahHeap::heap()),
2330 _regions(regions) {
2331 }
2332
2333 void work(uint worker_id) {
2334 if (CONCURRENT) {
2335 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2336 ShenandoahSuspendibleThreadSetJoiner stsj;
2337 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2338 } else {
2339 ShenandoahParallelWorkerSession worker_session(worker_id);
2340 do_work<ShenandoahSTWUpdateRefsClosure>(worker_id);
2341 }
2342 }
2343
2344 private:
2345 template<class T>
2346 void do_work(uint worker_id) {
2347 if (CONCURRENT && (worker_id == 0)) {
2348 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2349 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2350 size_t cset_regions = _heap->collection_set()->count();
2351 // We cannot transfer any more regions than will be reclaimed when the existing collection set is recycled, because
2352 // we need the reclaimed collection set regions to replenish the collector reserves
2353 _heap->free_set()->move_collector_sets_to_mutator(cset_regions);
2354 }
2355 // If !CONCURRENT, there's no value in expanding Mutator free set
2356 T cl;
2357 ShenandoahHeapRegion* r = _regions->next();
2358 while (r != nullptr) {
2359 HeapWord* update_watermark = r->get_update_watermark();
2360 assert (update_watermark >= r->bottom(), "sanity");
2361 if (r->is_active() && !r->is_cset()) {
2362 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2363 if (ShenandoahPacing) {
2364 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2365 }
2366 }
2367 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2368 return;
2369 }
2370 r = _regions->next();
2371 }
2372 }
2373 };
2374
2375 void ShenandoahHeap::update_heap_references(bool concurrent) {
2376 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2377
2378 if (concurrent) {
2379 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2380 workers()->run_task(&task);
2381 } else {
2382 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2383 workers()->run_task(&task);
2384 }
2385 }
2386
2387 ShenandoahSynchronizePinnedRegionStates::ShenandoahSynchronizePinnedRegionStates() : _lock(ShenandoahHeap::heap()->lock()) { }
2388
2389 void ShenandoahSynchronizePinnedRegionStates::heap_region_do(ShenandoahHeapRegion* r) {
2390 // Drop "pinned" state from regions that no longer have a pinned count. Put
2391 // regions with a pinned count into the "pinned" state.
2392 if (r->is_active()) {
2393 if (r->is_pinned()) {
2394 if (r->pin_count() == 0) {
2395 ShenandoahHeapLocker locker(_lock);
2396 r->make_unpinned();
2397 }
2398 } else {
2399 if (r->pin_count() > 0) {
2400 ShenandoahHeapLocker locker(_lock);
2401 r->make_pinned();
2402 }
2403 }
2404 }
2405 }
2406
2407 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2408 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2409 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2410
2411 {
2412 ShenandoahGCPhase phase(concurrent ?
2413 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2414 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2415
2416 final_update_refs_update_region_states();
2417
2418 assert_pinned_region_status();
2419 }
2420
2421 {
2422 ShenandoahGCPhase phase(concurrent ?
2423 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2424 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2425 trash_cset_regions();
2426 }
2427 }
2428
2429 void ShenandoahHeap::final_update_refs_update_region_states() {
2430 ShenandoahSynchronizePinnedRegionStates cl;
2431 parallel_heap_region_iterate(&cl);
2432 }
2433
2434 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2435 ShenandoahGCPhase phase(concurrent ?
2436 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2437 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2438 ShenandoahHeapLocker locker(lock());
2439 size_t young_cset_regions, old_cset_regions;
2440 size_t first_old_region, last_old_region, old_region_count;
2441 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count);
2442 // If there are no old regions, first_old_region will be greater than last_old_region
2443 assert((first_old_region > last_old_region) ||
2444 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2445 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2446 "sanity: old_region_count: " SIZE_FORMAT ", first_old_region: " SIZE_FORMAT ", last_old_region: " SIZE_FORMAT,
2447 old_region_count, first_old_region, last_old_region);
2448
2449 if (mode()->is_generational()) {
2450 #ifdef ASSERT
2451 if (ShenandoahVerify) {
2452 verifier()->verify_before_rebuilding_free_set();
2453 }
2454 #endif
2455
2456 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2457 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2458 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2459 size_t allocation_runway = gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions);
2460 gen_heap->compute_old_generation_balance(allocation_runway, old_cset_regions);
2461
2462 // Total old_available may have been expanded to hold anticipated promotions. We trigger if the fragmented available
2463 // memory represents more than 16 regions worth of data. Note that fragmentation may increase when we promote regular
2464 // regions in place when many of these regular regions have an abundant amount of available memory within them. Fragmentation
2465 // will decrease as promote-by-copy consumes the available memory within these partially consumed regions.
2466 //
2467 // We consider old-gen to have excessive fragmentation if more than 12.5% of old-gen is free memory that resides
2468 // within partially consumed regions of memory.
2469 }
2470 // Rebuild free set based on adjusted generation sizes.
2471 _free_set->rebuild(young_cset_regions, old_cset_regions);
2472
2473 if (mode()->is_generational()) {
2474 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2475 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2476 old_gen->heuristics()->trigger_maybe(first_old_region, last_old_region, old_region_count, num_regions());
2477 }
2478 }
2479
2480 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2481 print_on(st);
2482 st->cr();
2483 print_heap_regions_on(st);
2484 }
2485
2486 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2487 size_t slice = r->index() / _bitmap_regions_per_slice;
2488
2489 size_t regions_from = _bitmap_regions_per_slice * slice;
2490 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2491 for (size_t g = regions_from; g < regions_to; g++) {
2492 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2493 if (skip_self && g == r->index()) continue;
2494 if (get_region(g)->is_committed()) {
2495 return true;
2496 }
2497 }
2498 return false;
2499 }
2500
2501 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2502 shenandoah_assert_heaplocked();
2503
2504 // Bitmaps in special regions do not need commits
2505 if (_bitmap_region_special) {
2506 return true;
2507 }
2508
2509 if (is_bitmap_slice_committed(r, true)) {
2510 // Some other region from the group is already committed, meaning the bitmap
2511 // slice is already committed, we exit right away.
2512 return true;
2513 }
2514
2515 // Commit the bitmap slice:
2516 size_t slice = r->index() / _bitmap_regions_per_slice;
2517 size_t off = _bitmap_bytes_per_slice * slice;
2518 size_t len = _bitmap_bytes_per_slice;
2519 char* start = (char*) _bitmap_region.start() + off;
2520
2521 if (!os::commit_memory(start, len, false)) {
2522 return false;
2523 }
2524
2525 if (AlwaysPreTouch) {
2526 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2527 }
2528
2529 return true;
2530 }
2531
2532 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2533 shenandoah_assert_heaplocked();
2534
2535 // Bitmaps in special regions do not need uncommits
2536 if (_bitmap_region_special) {
2537 return true;
2538 }
2539
2540 if (is_bitmap_slice_committed(r, true)) {
2541 // Some other region from the group is still committed, meaning the bitmap
2542 // slice is should stay committed, exit right away.
2543 return true;
2544 }
2545
2546 // Uncommit the bitmap slice:
2547 size_t slice = r->index() / _bitmap_regions_per_slice;
2548 size_t off = _bitmap_bytes_per_slice * slice;
2549 size_t len = _bitmap_bytes_per_slice;
2550 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2551 return false;
2552 }
2553 return true;
2554 }
2555
2556 void ShenandoahHeap::safepoint_synchronize_begin() {
2557 SuspendibleThreadSet::synchronize();
2558 }
2559
2560 void ShenandoahHeap::safepoint_synchronize_end() {
2561 SuspendibleThreadSet::desynchronize();
2562 }
2563
2564 void ShenandoahHeap::try_inject_alloc_failure() {
2565 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2566 _inject_alloc_failure.set();
2567 os::naked_short_sleep(1);
2568 if (cancelled_gc()) {
2569 log_info(gc)("Allocation failure was successfully injected");
2570 }
2571 }
2572 }
2573
2574 bool ShenandoahHeap::should_inject_alloc_failure() {
2575 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2576 }
2577
2578 void ShenandoahHeap::initialize_serviceability() {
2579 _memory_pool = new ShenandoahMemoryPool(this);
2580 _cycle_memory_manager.add_pool(_memory_pool);
2581 _stw_memory_manager.add_pool(_memory_pool);
2582 }
2583
2584 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2585 GrowableArray<GCMemoryManager*> memory_managers(2);
2586 memory_managers.append(&_cycle_memory_manager);
2587 memory_managers.append(&_stw_memory_manager);
2588 return memory_managers;
2589 }
2590
2591 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2592 GrowableArray<MemoryPool*> memory_pools(1);
2593 memory_pools.append(_memory_pool);
2594 return memory_pools;
2595 }
2596
2597 MemoryUsage ShenandoahHeap::memory_usage() {
2598 return MemoryUsage(_initial_size, used(), committed(), max_capacity());
2599 }
2600
2601 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2602 _heap(ShenandoahHeap::heap()),
2603 _index(0) {}
2604
2605 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2606 _heap(heap),
2607 _index(0) {}
2608
2609 void ShenandoahRegionIterator::reset() {
2610 _index = 0;
2611 }
2612
2613 bool ShenandoahRegionIterator::has_next() const {
2614 return _index < _heap->num_regions();
2615 }
2616
2617 char ShenandoahHeap::gc_state() const {
2618 return _gc_state.raw_value();
2619 }
2620
2621 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2622 #ifdef ASSERT
2623 assert(_liveness_cache != nullptr, "sanity");
2624 assert(worker_id < _max_workers, "sanity");
2625 for (uint i = 0; i < num_regions(); i++) {
2626 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2627 }
2628 #endif
2629 return _liveness_cache[worker_id];
2630 }
2631
2632 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2633 assert(worker_id < _max_workers, "sanity");
2634 assert(_liveness_cache != nullptr, "sanity");
2635 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2636 for (uint i = 0; i < num_regions(); i++) {
2637 ShenandoahLiveData live = ld[i];
2638 if (live > 0) {
2639 ShenandoahHeapRegion* r = get_region(i);
2640 r->increase_live_data_gc_words(live);
2641 ld[i] = 0;
2642 }
2643 }
2644 }
2645
2646 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2647 if (is_idle()) return false;
2648
2649 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2650 // marking phase.
2651 if (is_concurrent_mark_in_progress() &&
2652 !marking_context()->allocated_after_mark_start(obj)) {
2653 return true;
2654 }
2655
2656 // Can not guarantee obj is deeply good.
2657 if (has_forwarded_objects()) {
2658 return true;
2659 }
2660
2661 return false;
2662 }
2663
2664 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2665 if (!mode()->is_generational()) {
2666 return global_generation();
2667 } else if (affiliation == YOUNG_GENERATION) {
2668 return young_generation();
2669 } else if (affiliation == OLD_GENERATION) {
2670 return old_generation();
2671 }
2672
2673 ShouldNotReachHere();
2674 return nullptr;
2675 }
2676
2677 void ShenandoahHeap::log_heap_status(const char* msg) const {
2678 if (mode()->is_generational()) {
2679 young_generation()->log_status(msg);
2680 old_generation()->log_status(msg);
2681 } else {
2682 global_generation()->log_status(msg);
2683 }
2684 }