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->finish_rebuild(young_cset_regions, old_cset_regions, num_old);
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 // ...and clear or zap just allocated TLAB, if needed.
926 if (ZeroTLAB) {
927 Copy::zero_to_words(gclab_buf, actual_size);
928 } else if (ZapTLAB) {
929 // Skip mangling the space corresponding to the object header to
930 // ensure that the returned space is not considered parsable by
931 // any concurrent GC thread.
932 size_t hdr_size = oopDesc::header_size();
933 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
934 }
935 gclab->set_buf(gclab_buf, actual_size);
936 return gclab->allocate(size);
937 }
938
939 // Called from stubs in JIT code or interpreter
940 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
941 size_t requested_size,
942 size_t* actual_size) {
943 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
944 HeapWord* res = allocate_memory(req);
945 if (res != nullptr) {
946 *actual_size = req.actual_size();
947 } else {
948 *actual_size = 0;
949 }
950 return res;
951 }
952
953 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
954 size_t word_size,
955 size_t* actual_size) {
956 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
957 HeapWord* res = allocate_memory(req);
958 if (res != nullptr) {
959 *actual_size = req.actual_size();
960 } else {
961 *actual_size = 0;
962 }
963 return res;
964 }
965
966 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
967 intptr_t pacer_epoch = 0;
968 bool in_new_region = false;
969 HeapWord* result = nullptr;
970
971 if (req.is_mutator_alloc()) {
972 if (ShenandoahPacing) {
973 pacer()->pace_for_alloc(req.size());
974 pacer_epoch = pacer()->epoch();
975 }
976
977 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
978 result = allocate_memory_under_lock(req, in_new_region);
979 }
980
981 // Check that gc overhead is not exceeded.
982 //
983 // Shenandoah will grind along for quite a while allocating one
984 // object at a time using shared (non-tlab) allocations. This check
985 // is testing that the GC overhead limit has not been exceeded.
986 // This will notify the collector to start a cycle, but will raise
987 // an OOME to the mutator if the last Full GCs have not made progress.
988 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
989 if ((result == nullptr) && !req.is_lab_alloc() && (get_gc_no_progress_count() > ShenandoahNoProgressThreshold)) {
990 control_thread()->handle_alloc_failure(req, false);
991 req.set_actual_size(0);
992 return nullptr;
993 }
994
995 if (result == nullptr) {
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, until at least one full GC has completed.
1002 //
1003 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
1004 // a) We experienced a GC that had good progress, or
1005 // b) We experienced at least one Full GC (whether or not it had good progress)
1006 //
1007 // TODO: Consider GLOBAL GC rather than Full GC to remediate OOM condition: https://bugs.openjdk.org/browse/JDK-8335910
1008
1009 size_t original_count = shenandoah_policy()->full_gc_count();
1010 while ((result == nullptr) && (original_count == shenandoah_policy()->full_gc_count())) {
1011 control_thread()->handle_alloc_failure(req, true);
1012 result = allocate_memory_under_lock(req, in_new_region);
1013 }
1014 if (result != nullptr) {
1015 // If our allocation request has been satisifed after it initially failed, we count this as good gc progress
1016 notify_gc_progress();
1017 }
1018 if (log_is_enabled(Debug, gc, alloc)) {
1019 ResourceMark rm;
1020 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: " SIZE_FORMAT
1021 ", Original: " SIZE_FORMAT ", Latest: " SIZE_FORMAT,
1022 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
1023 original_count, get_gc_no_progress_count());
1024 }
1025 }
1026 } else {
1027 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
1028 result = allocate_memory_under_lock(req, in_new_region);
1029 // Do not call handle_alloc_failure() here, because we cannot block.
1030 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1031 }
1032
1033 if (in_new_region) {
1034 notify_heap_changed();
1035 }
1036
1037 if (result == nullptr) {
1038 req.set_actual_size(0);
1039 }
1040
1041 // This is called regardless of the outcome of the allocation to account
1042 // for any waste created by retiring regions with this request.
1043 increase_used(req);
1044
1045 if (result != nullptr) {
1046 size_t requested = req.size();
1047 size_t actual = req.actual_size();
1048
1049 assert (req.is_lab_alloc() || (requested == actual),
1050 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
1051 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
1052
1053 if (req.is_mutator_alloc()) {
1054 // If we requested more than we were granted, give the rest back to pacer.
1055 // This only matters if we are in the same pacing epoch: do not try to unpace
1056 // over the budget for the other phase.
1057 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
1058 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
1059 }
1060 }
1061 }
1062
1063 return result;
1064 }
1065
1066 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1067 // If we are dealing with mutator allocation, then we may need to block for safepoint.
1068 // We cannot block for safepoint for GC allocations, because there is a high chance
1069 // we are already running at safepoint or from stack watermark machinery, and we cannot
1070 // block again.
1071 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1072
1073 // Make sure the old generation has room for either evacuations or promotions before trying to allocate.
1074 if (req.is_old() && !old_generation()->can_allocate(req)) {
1075 return nullptr;
1076 }
1077
1078 // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available
1079 // memory.
1080 HeapWord* result = _free_set->allocate(req, in_new_region);
1081
1082 // Record the plab configuration for this result and register the object.
1083 if (result != nullptr && req.is_old()) {
1084 old_generation()->configure_plab_for_current_thread(req);
1085 if (req.type() == ShenandoahAllocRequest::_alloc_shared_gc) {
1086 // Register the newly allocated object while we're holding the global lock since there's no synchronization
1087 // built in to the implementation of register_object(). There are potential races when multiple independent
1088 // threads are allocating objects, some of which might span the same card region. For example, consider
1089 // a card table's memory region within which three objects are being allocated by three different threads:
1090 //
1091 // objects being "concurrently" allocated:
1092 // [-----a------][-----b-----][--------------c------------------]
1093 // [---- card table memory range --------------]
1094 //
1095 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a
1096 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region.
1097 // Allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region.
1098 // Allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this
1099 // card region.
1100 //
1101 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as
1102 // last-start representing object b while first-start represents object c. This is why we need to require all
1103 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range.
1104 old_generation()->card_scan()->register_object(result);
1105 }
1106 }
1107
1108 return result;
1109 }
1110
1111 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1112 bool* gc_overhead_limit_was_exceeded) {
1113 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1114 return allocate_memory(req);
1115 }
1116
1117 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1118 size_t size,
1119 Metaspace::MetadataType mdtype) {
1120 MetaWord* result;
1121
1122 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1123 ShenandoahHeuristics* h = global_generation()->heuristics();
1124 if (h->can_unload_classes()) {
1125 h->record_metaspace_oom();
1126 }
1127
1128 // Expand and retry allocation
1129 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1130 if (result != nullptr) {
1131 return result;
1132 }
1133
1134 // Start full GC
1135 collect(GCCause::_metadata_GC_clear_soft_refs);
1136
1137 // Retry allocation
1138 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1139 if (result != nullptr) {
1140 return result;
1141 }
1142
1143 // Expand and retry allocation
1144 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1145 if (result != nullptr) {
1146 return result;
1147 }
1148
1149 // Out of memory
1150 return nullptr;
1151 }
1152
1153 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1154 private:
1155 ShenandoahHeap* const _heap;
1156 Thread* const _thread;
1157 public:
1158 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1159 _heap(heap), _thread(Thread::current()) {}
1160
1161 void do_object(oop p) {
1162 shenandoah_assert_marked(nullptr, p);
1163 if (!p->is_forwarded()) {
1164 _heap->evacuate_object(p, _thread);
1165 }
1166 }
1167 };
1168
1169 class ShenandoahEvacuationTask : public WorkerTask {
1170 private:
1171 ShenandoahHeap* const _sh;
1172 ShenandoahCollectionSet* const _cs;
1173 bool _concurrent;
1174 public:
1175 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1176 ShenandoahCollectionSet* cs,
1177 bool concurrent) :
1178 WorkerTask("Shenandoah Evacuation"),
1179 _sh(sh),
1180 _cs(cs),
1181 _concurrent(concurrent)
1182 {}
1183
1184 void work(uint worker_id) {
1185 if (_concurrent) {
1186 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1187 ShenandoahSuspendibleThreadSetJoiner stsj;
1188 ShenandoahEvacOOMScope oom_evac_scope;
1189 do_work();
1190 } else {
1191 ShenandoahParallelWorkerSession worker_session(worker_id);
1192 ShenandoahEvacOOMScope oom_evac_scope;
1193 do_work();
1194 }
1195 }
1196
1197 private:
1198 void do_work() {
1199 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1200 ShenandoahHeapRegion* r;
1201 while ((r =_cs->claim_next()) != nullptr) {
1202 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1203 _sh->marked_object_iterate(r, &cl);
1204
1205 if (ShenandoahPacing) {
1206 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1207 }
1208
1209 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1210 break;
1211 }
1212 }
1213 }
1214 };
1215
1216 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1217 if (mode()->is_generational()) {
1218 ShenandoahRegionIterator regions;
1219 ShenandoahGenerationalEvacuationTask task(ShenandoahGenerationalHeap::heap(), ®ions, concurrent);
1220 workers()->run_task(&task);
1221 } else {
1222 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1223 workers()->run_task(&task);
1224 }
1225 }
1226
1227 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1228 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1229 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
1230 // This thread went through the OOM during evac protocol. It is safe to return
1231 // the forward pointer. It must not attempt to evacuate any other objects.
1232 return ShenandoahBarrierSet::resolve_forwarded(p);
1233 }
1234
1235 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1236
1237 ShenandoahHeapRegion* r = heap_region_containing(p);
1238 assert(!r->is_humongous(), "never evacuate humongous objects");
1239
1240 ShenandoahAffiliation target_gen = r->affiliation();
1241 return try_evacuate_object(p, thread, r, target_gen);
1242 }
1243
1244 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1245 ShenandoahAffiliation target_gen) {
1246 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1247 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1248 bool alloc_from_lab = true;
1249 HeapWord* copy = nullptr;
1250 size_t size = p->size();
1251
1252 #ifdef ASSERT
1253 if (ShenandoahOOMDuringEvacALot &&
1254 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1255 copy = nullptr;
1256 } else {
1257 #endif
1258 if (UseTLAB) {
1259 copy = allocate_from_gclab(thread, size);
1260 if ((copy == nullptr) && (size < ShenandoahThreadLocalData::gclab_size(thread))) {
1261 // GCLAB allocation failed because we are bumping up against the limit on young evacuation reserve. Try resetting
1262 // the desired GCLAB size and retry GCLAB allocation to avoid cascading of shared memory allocations.
1263 // TODO: is this right? using PLAB::min_size() here for gc lab size?
1264 ShenandoahThreadLocalData::set_gclab_size(thread, PLAB::min_size());
1265 copy = allocate_from_gclab(thread, size);
1266 // If we still get nullptr, we'll try a shared allocation below.
1267 }
1268 }
1269
1270 if (copy == nullptr) {
1271 // If we failed to allocate in LAB, we'll try a shared allocation.
1272 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1273 copy = allocate_memory(req);
1274 alloc_from_lab = false;
1275 }
1276 #ifdef ASSERT
1277 }
1278 #endif
1279
1280 if (copy == nullptr) {
1281 control_thread()->handle_alloc_failure_evac(size);
1282
1283 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1284
1285 return ShenandoahBarrierSet::resolve_forwarded(p);
1286 }
1287
1288 // Copy the object:
1289 _evac_tracker->begin_evacuation(thread, size * HeapWordSize);
1290 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1291
1292 oop copy_val = cast_to_oop(copy);
1293
1294 // Try to install the new forwarding pointer.
1295 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1296
1297 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1298 if (result == copy_val) {
1299 // Successfully evacuated. Our copy is now the public one!
1300 _evac_tracker->end_evacuation(thread, size * HeapWordSize);
1301 shenandoah_assert_correct(nullptr, copy_val);
1302 return copy_val;
1303 } else {
1304 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1305 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1306 // But if it happens to contain references to evacuated regions, those references would
1307 // not get updated for this stale copy during this cycle, and we will crash while scanning
1308 // it the next cycle.
1309 if (alloc_from_lab) {
1310 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1311 // object will overwrite this stale copy, or the filler object on LAB retirement will
1312 // do this.
1313 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1314 } else {
1315 // For non-LAB allocations, we have no way to retract the allocation, and
1316 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1317 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1318 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1319 fill_with_object(copy, size);
1320 shenandoah_assert_correct(nullptr, copy_val);
1321 // For non-LAB allocations, the object has already been registered
1322 }
1323 shenandoah_assert_correct(nullptr, result);
1324 return result;
1325 }
1326 }
1327
1328 void ShenandoahHeap::trash_cset_regions() {
1329 ShenandoahHeapLocker locker(lock());
1330
1331 ShenandoahCollectionSet* set = collection_set();
1332 ShenandoahHeapRegion* r;
1333 set->clear_current_index();
1334 while ((r = set->next()) != nullptr) {
1335 r->make_trash();
1336 }
1337 collection_set()->clear();
1338 }
1339
1340 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1341 st->print_cr("Heap Regions:");
1342 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1343 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1344 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1345 st->print_cr("UWM=update watermark, U=used");
1346 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1347 st->print_cr("S=shared allocs, L=live data");
1348 st->print_cr("CP=critical pins");
1349
1350 for (size_t i = 0; i < num_regions(); i++) {
1351 get_region(i)->print_on(st);
1352 }
1353 }
1354
1355 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1356 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1357
1358 oop humongous_obj = cast_to_oop(start->bottom());
1359 size_t size = humongous_obj->size();
1360 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1361 size_t index = start->index() + required_regions - 1;
1362
1363 assert(!start->has_live(), "liveness must be zero");
1364
1365 for(size_t i = 0; i < required_regions; i++) {
1366 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1367 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1368 ShenandoahHeapRegion* region = get_region(index --);
1369
1370 assert(region->is_humongous(), "expect correct humongous start or continuation");
1371 assert(!region->is_cset(), "Humongous region should not be in collection set");
1372
1373 region->make_trash_immediate();
1374 }
1375 return required_regions;
1376 }
1377
1378 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1379 public:
1380 ShenandoahCheckCleanGCLABClosure() {}
1381 void do_thread(Thread* thread) {
1382 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1383 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1384 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1385
1386 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1387 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1388 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1389 assert(plab->words_remaining() == 0, "PLAB should not need retirement");
1390 }
1391 }
1392 };
1393
1394 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1395 private:
1396 bool const _resize;
1397 public:
1398 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1399 void do_thread(Thread* thread) {
1400 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1401 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1402 gclab->retire();
1403 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1404 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1405 }
1406
1407 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1408 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1409 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1410
1411 // There are two reasons to retire all plabs between old-gen evacuation passes.
1412 // 1. We need to make the plab memory parsable by remembered-set scanning.
1413 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1414 ShenandoahGenerationalHeap::heap()->retire_plab(plab, thread);
1415 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) {
1416 ShenandoahThreadLocalData::set_plab_size(thread, 0);
1417 }
1418 }
1419 }
1420 };
1421
1422 void ShenandoahHeap::labs_make_parsable() {
1423 assert(UseTLAB, "Only call with UseTLAB");
1424
1425 ShenandoahRetireGCLABClosure cl(false);
1426
1427 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1428 ThreadLocalAllocBuffer& tlab = t->tlab();
1429 tlab.make_parsable();
1430 cl.do_thread(t);
1431 }
1432
1433 workers()->threads_do(&cl);
1434 }
1435
1436 void ShenandoahHeap::tlabs_retire(bool resize) {
1437 assert(UseTLAB, "Only call with UseTLAB");
1438 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1439
1440 ThreadLocalAllocStats stats;
1441
1442 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1443 ThreadLocalAllocBuffer& tlab = t->tlab();
1444 tlab.retire(&stats);
1445 if (resize) {
1446 tlab.resize();
1447 }
1448 }
1449
1450 stats.publish();
1451
1452 #ifdef ASSERT
1453 ShenandoahCheckCleanGCLABClosure cl;
1454 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1455 cl.do_thread(t);
1456 }
1457 workers()->threads_do(&cl);
1458 #endif
1459 }
1460
1461 void ShenandoahHeap::gclabs_retire(bool resize) {
1462 assert(UseTLAB, "Only call with UseTLAB");
1463 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1464
1465 ShenandoahRetireGCLABClosure cl(resize);
1466 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1467 cl.do_thread(t);
1468 }
1469 workers()->threads_do(&cl);
1470
1471 if (safepoint_workers() != nullptr) {
1472 safepoint_workers()->threads_do(&cl);
1473 }
1474 }
1475
1476 // Returns size in bytes
1477 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1478 // Return the max allowed size, and let the allocation path
1479 // figure out the safe size for current allocation.
1480 return ShenandoahHeapRegion::max_tlab_size_bytes();
1481 }
1482
1483 size_t ShenandoahHeap::max_tlab_size() const {
1484 // Returns size in words
1485 return ShenandoahHeapRegion::max_tlab_size_words();
1486 }
1487
1488 void ShenandoahHeap::collect(GCCause::Cause cause) {
1489 control_thread()->request_gc(cause);
1490 }
1491
1492 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1493 //assert(false, "Shouldn't need to do full collections");
1494 }
1495
1496 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1497 ShenandoahHeapRegion* r = heap_region_containing(addr);
1498 if (r != nullptr) {
1499 return r->block_start(addr);
1500 }
1501 return nullptr;
1502 }
1503
1504 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1505 ShenandoahHeapRegion* r = heap_region_containing(addr);
1506 return r->block_is_obj(addr);
1507 }
1508
1509 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1510 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1511 }
1512
1513 void ShenandoahHeap::prepare_for_verify() {
1514 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1515 labs_make_parsable();
1516 }
1517 }
1518
1519 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1520 if (_shenandoah_policy->is_at_shutdown()) {
1521 return;
1522 }
1523
1524 if (_control_thread != nullptr) {
1525 tcl->do_thread(_control_thread);
1526 }
1527
1528 workers()->threads_do(tcl);
1529 if (_safepoint_workers != nullptr) {
1530 _safepoint_workers->threads_do(tcl);
1531 }
1532 }
1533
1534 void ShenandoahHeap::print_tracing_info() const {
1535 LogTarget(Info, gc, stats) lt;
1536 if (lt.is_enabled()) {
1537 ResourceMark rm;
1538 LogStream ls(lt);
1539
1540 phase_timings()->print_global_on(&ls);
1541
1542 ls.cr();
1543 ls.cr();
1544
1545 shenandoah_policy()->print_gc_stats(&ls);
1546
1547 ls.cr();
1548
1549 evac_tracker()->print_global_on(&ls);
1550
1551 ls.cr();
1552 ls.cr();
1553 }
1554 }
1555
1556 void ShenandoahHeap::set_gc_generation(ShenandoahGeneration* generation) {
1557 shenandoah_assert_control_or_vm_thread_at_safepoint();
1558 _gc_generation = generation;
1559 }
1560
1561 // Active generation may only be set by the VM thread at a safepoint.
1562 void ShenandoahHeap::set_active_generation() {
1563 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1564 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1565 assert(_gc_generation != nullptr, "Will set _active_generation to nullptr");
1566 _active_generation = _gc_generation;
1567 }
1568
1569 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
1570 shenandoah_policy()->record_collection_cause(cause);
1571
1572 assert(gc_cause() == GCCause::_no_gc, "Over-writing cause");
1573 assert(_gc_generation == nullptr, "Over-writing _gc_generation");
1574
1575 set_gc_cause(cause);
1576 set_gc_generation(generation);
1577
1578 generation->heuristics()->record_cycle_start();
1579 }
1580
1581 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1582 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1583 assert(_gc_generation != nullptr, "_gc_generation wasn't set");
1584
1585 generation->heuristics()->record_cycle_end();
1586 if (mode()->is_generational() && generation->is_global()) {
1587 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1588 young_generation()->heuristics()->record_cycle_end();
1589 old_generation()->heuristics()->record_cycle_end();
1590 }
1591
1592 set_gc_generation(nullptr);
1593 set_gc_cause(GCCause::_no_gc);
1594 }
1595
1596 void ShenandoahHeap::verify(VerifyOption vo) {
1597 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1598 if (ShenandoahVerify) {
1599 verifier()->verify_generic(vo);
1600 } else {
1601 // TODO: Consider allocating verification bitmaps on demand,
1602 // and turn this on unconditionally.
1603 }
1604 }
1605 }
1606 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1607 return _free_set->capacity();
1608 }
1609
1610 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1611 private:
1612 MarkBitMap* _bitmap;
1613 ShenandoahScanObjectStack* _oop_stack;
1614 ShenandoahHeap* const _heap;
1615 ShenandoahMarkingContext* const _marking_context;
1616
1617 template <class T>
1618 void do_oop_work(T* p) {
1619 T o = RawAccess<>::oop_load(p);
1620 if (!CompressedOops::is_null(o)) {
1621 oop obj = CompressedOops::decode_not_null(o);
1622 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1623 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1624 return;
1625 }
1626 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1627
1628 assert(oopDesc::is_oop(obj), "must be a valid oop");
1629 if (!_bitmap->is_marked(obj)) {
1630 _bitmap->mark(obj);
1631 _oop_stack->push(obj);
1632 }
1633 }
1634 }
1635 public:
1636 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1637 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1638 _marking_context(_heap->marking_context()) {}
1639 void do_oop(oop* p) { do_oop_work(p); }
1640 void do_oop(narrowOop* p) { do_oop_work(p); }
1641 };
1642
1643 /*
1644 * This is public API, used in preparation of object_iterate().
1645 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1646 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1647 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1648 */
1649 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1650 // No-op.
1651 }
1652
1653 /*
1654 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1655 *
1656 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1657 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1658 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1659 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1660 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1661 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1662 * wiped the bitmap in preparation for next marking).
1663 *
1664 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1665 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1666 * is allowed to report dead objects, but is not required to do so.
1667 */
1668 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1669 // Reset bitmap
1670 if (!prepare_aux_bitmap_for_iteration())
1671 return;
1672
1673 ShenandoahScanObjectStack oop_stack;
1674 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1675 // Seed the stack with root scan
1676 scan_roots_for_iteration(&oop_stack, &oops);
1677
1678 // Work through the oop stack to traverse heap
1679 while (! oop_stack.is_empty()) {
1680 oop obj = oop_stack.pop();
1681 assert(oopDesc::is_oop(obj), "must be a valid oop");
1682 cl->do_object(obj);
1683 obj->oop_iterate(&oops);
1684 }
1685
1686 assert(oop_stack.is_empty(), "should be empty");
1687 // Reclaim bitmap
1688 reclaim_aux_bitmap_for_iteration();
1689 }
1690
1691 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1692 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1693
1694 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1695 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1696 return false;
1697 }
1698 // Reset bitmap
1699 _aux_bit_map.clear();
1700 return true;
1701 }
1702
1703 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1704 // Process GC roots according to current GC cycle
1705 // This populates the work stack with initial objects
1706 // It is important to relinquish the associated locks before diving
1707 // into heap dumper
1708 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1709 ShenandoahHeapIterationRootScanner rp(n_workers);
1710 rp.roots_do(oops);
1711 }
1712
1713 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1714 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1715 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1716 }
1717 }
1718
1719 // Closure for parallelly iterate objects
1720 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1721 private:
1722 MarkBitMap* _bitmap;
1723 ShenandoahObjToScanQueue* _queue;
1724 ShenandoahHeap* const _heap;
1725 ShenandoahMarkingContext* const _marking_context;
1726
1727 template <class T>
1728 void do_oop_work(T* p) {
1729 T o = RawAccess<>::oop_load(p);
1730 if (!CompressedOops::is_null(o)) {
1731 oop obj = CompressedOops::decode_not_null(o);
1732 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1733 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1734 return;
1735 }
1736 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1737
1738 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1739 if (_bitmap->par_mark(obj)) {
1740 _queue->push(ShenandoahMarkTask(obj));
1741 }
1742 }
1743 }
1744 public:
1745 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1746 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1747 _marking_context(_heap->marking_context()) {}
1748 void do_oop(oop* p) { do_oop_work(p); }
1749 void do_oop(narrowOop* p) { do_oop_work(p); }
1750 };
1751
1752 // Object iterator for parallel heap iteraion.
1753 // The root scanning phase happenes in construction as a preparation of
1754 // parallel marking queues.
1755 // Every worker processes it's own marking queue. work-stealing is used
1756 // to balance workload.
1757 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1758 private:
1759 uint _num_workers;
1760 bool _init_ready;
1761 MarkBitMap* _aux_bit_map;
1762 ShenandoahHeap* _heap;
1763 ShenandoahScanObjectStack _roots_stack; // global roots stack
1764 ShenandoahObjToScanQueueSet* _task_queues;
1765 public:
1766 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1767 _num_workers(num_workers),
1768 _init_ready(false),
1769 _aux_bit_map(bitmap),
1770 _heap(ShenandoahHeap::heap()) {
1771 // Initialize bitmap
1772 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1773 if (!_init_ready) {
1774 return;
1775 }
1776
1777 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1778 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1779
1780 _init_ready = prepare_worker_queues();
1781 }
1782
1783 ~ShenandoahParallelObjectIterator() {
1784 // Reclaim bitmap
1785 _heap->reclaim_aux_bitmap_for_iteration();
1786 // Reclaim queue for workers
1787 if (_task_queues!= nullptr) {
1788 for (uint i = 0; i < _num_workers; ++i) {
1789 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1790 if (q != nullptr) {
1791 delete q;
1792 _task_queues->register_queue(i, nullptr);
1793 }
1794 }
1795 delete _task_queues;
1796 _task_queues = nullptr;
1797 }
1798 }
1799
1800 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1801 if (_init_ready) {
1802 object_iterate_parallel(cl, worker_id, _task_queues);
1803 }
1804 }
1805
1806 private:
1807 // Divide global root_stack into worker queues
1808 bool prepare_worker_queues() {
1809 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1810 // Initialize queues for every workers
1811 for (uint i = 0; i < _num_workers; ++i) {
1812 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1813 _task_queues->register_queue(i, task_queue);
1814 }
1815 // Divide roots among the workers. Assume that object referencing distribution
1816 // is related with root kind, use round-robin to make every worker have same chance
1817 // to process every kind of roots
1818 size_t roots_num = _roots_stack.size();
1819 if (roots_num == 0) {
1820 // No work to do
1821 return false;
1822 }
1823
1824 for (uint j = 0; j < roots_num; j++) {
1825 uint stack_id = j % _num_workers;
1826 oop obj = _roots_stack.pop();
1827 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1828 }
1829 return true;
1830 }
1831
1832 void object_iterate_parallel(ObjectClosure* cl,
1833 uint worker_id,
1834 ShenandoahObjToScanQueueSet* queue_set) {
1835 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1836 assert(queue_set != nullptr, "task queue must not be null");
1837
1838 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1839 assert(q != nullptr, "object iterate queue must not be null");
1840
1841 ShenandoahMarkTask t;
1842 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1843
1844 // Work through the queue to traverse heap.
1845 // Steal when there is no task in queue.
1846 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1847 oop obj = t.obj();
1848 assert(oopDesc::is_oop(obj), "must be a valid oop");
1849 cl->do_object(obj);
1850 obj->oop_iterate(&oops);
1851 }
1852 assert(q->is_empty(), "should be empty");
1853 }
1854 };
1855
1856 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1857 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1858 }
1859
1860 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1861 void ShenandoahHeap::keep_alive(oop obj) {
1862 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1863 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1864 }
1865 }
1866
1867 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1868 for (size_t i = 0; i < num_regions(); i++) {
1869 ShenandoahHeapRegion* current = get_region(i);
1870 blk->heap_region_do(current);
1871 }
1872 }
1873
1874 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1875 private:
1876 ShenandoahHeap* const _heap;
1877 ShenandoahHeapRegionClosure* const _blk;
1878
1879 shenandoah_padding(0);
1880 volatile size_t _index;
1881 shenandoah_padding(1);
1882
1883 public:
1884 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1885 WorkerTask("Shenandoah Parallel Region Operation"),
1886 _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1887
1888 void work(uint worker_id) {
1889 ShenandoahParallelWorkerSession worker_session(worker_id);
1890 size_t stride = ShenandoahParallelRegionStride;
1891
1892 size_t max = _heap->num_regions();
1893 while (Atomic::load(&_index) < max) {
1894 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1895 size_t start = cur;
1896 size_t end = MIN2(cur + stride, max);
1897 if (start >= max) break;
1898
1899 for (size_t i = cur; i < end; i++) {
1900 ShenandoahHeapRegion* current = _heap->get_region(i);
1901 _blk->heap_region_do(current);
1902 }
1903 }
1904 }
1905 };
1906
1907 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1908 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1909 if (num_regions() > ShenandoahParallelRegionStride) {
1910 ShenandoahParallelHeapRegionTask task(blk);
1911 workers()->run_task(&task);
1912 } else {
1913 heap_region_iterate(blk);
1914 }
1915 }
1916
1917 class ShenandoahRendezvousClosure : public HandshakeClosure {
1918 public:
1919 inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
1920 inline void do_thread(Thread* thread) {}
1921 };
1922
1923 void ShenandoahHeap::rendezvous_threads() {
1924 ShenandoahRendezvousClosure cl;
1925 Handshake::execute(&cl);
1926 }
1927
1928 void ShenandoahHeap::recycle_trash() {
1929 free_set()->recycle_trash();
1930 }
1931
1932 void ShenandoahHeap::do_class_unloading() {
1933 _unloader.unload();
1934 if (mode()->is_generational()) {
1935 old_generation()->set_parseable(false);
1936 }
1937 }
1938
1939 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1940 // Weak refs processing
1941 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1942 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1943 ShenandoahTimingsTracker t(phase);
1944 ShenandoahGCWorkerPhase worker_phase(phase);
1945 shenandoah_assert_generations_reconciled();
1946 gc_generation()->ref_processor()->process_references(phase, workers(), false /* concurrent */);
1947 }
1948
1949 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1950 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1951
1952 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1953 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1954 // for future GCLABs here.
1955 if (UseTLAB) {
1956 ShenandoahGCPhase phase(concurrent ?
1957 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1958 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1959 gclabs_retire(ResizeTLAB);
1960 }
1961
1962 _update_refs_iterator.reset();
1963 }
1964
1965 void ShenandoahHeap::propagate_gc_state_to_java_threads() {
1966 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1967 if (_gc_state_changed) {
1968 _gc_state_changed = false;
1969 char state = gc_state();
1970 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1971 ShenandoahThreadLocalData::set_gc_state(t, state);
1972 }
1973 }
1974 }
1975
1976 void ShenandoahHeap::set_gc_state(uint mask, bool value) {
1977 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1978 _gc_state.set_cond(mask, value);
1979 _gc_state_changed = true;
1980 // Check that if concurrent weak root is set then active_gen isn't null
1981 assert(!is_concurrent_weak_root_in_progress() || active_generation() != nullptr, "Error");
1982 shenandoah_assert_generations_reconciled();
1983 }
1984
1985 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
1986 uint mask;
1987 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
1988 if (!in_progress && is_concurrent_old_mark_in_progress()) {
1989 assert(mode()->is_generational(), "Only generational GC has old marking");
1990 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
1991 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
1992 mask = YOUNG_MARKING;
1993 } else {
1994 mask = MARKING | YOUNG_MARKING;
1995 }
1996 set_gc_state(mask, in_progress);
1997 manage_satb_barrier(in_progress);
1998 }
1999
2000 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2001 #ifdef ASSERT
2002 // has_forwarded_objects() iff UPDATEREFS or EVACUATION
2003 bool has_forwarded = has_forwarded_objects();
2004 bool updating_or_evacuating = _gc_state.is_set(UPDATEREFS | EVACUATION);
2005 bool evacuating = _gc_state.is_set(EVACUATION);
2006 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2007 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2008 #endif
2009 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2010 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2011 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2012 set_gc_state(OLD_MARKING, in_progress);
2013 } else {
2014 set_gc_state(MARKING | OLD_MARKING, in_progress);
2015 }
2016 manage_satb_barrier(in_progress);
2017 }
2018
2019 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2020 return old_generation()->is_preparing_for_mark();
2021 }
2022
2023 void ShenandoahHeap::manage_satb_barrier(bool active) {
2024 if (is_concurrent_mark_in_progress()) {
2025 // Ignore request to deactivate barrier while concurrent mark is in progress.
2026 // Do not attempt to re-activate the barrier if it is already active.
2027 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2028 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2029 }
2030 } else {
2031 // No concurrent marking is in progress so honor request to deactivate,
2032 // but only if the barrier is already active.
2033 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2034 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2035 }
2036 }
2037 }
2038
2039 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2040 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2041 set_gc_state(EVACUATION, in_progress);
2042 }
2043
2044 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2045 if (in_progress) {
2046 _concurrent_strong_root_in_progress.set();
2047 } else {
2048 _concurrent_strong_root_in_progress.unset();
2049 }
2050 }
2051
2052 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2053 set_gc_state(WEAK_ROOTS, cond);
2054 }
2055
2056 GCTracer* ShenandoahHeap::tracer() {
2057 return shenandoah_policy()->tracer();
2058 }
2059
2060 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2061 return _free_set->used();
2062 }
2063
2064 bool ShenandoahHeap::try_cancel_gc() {
2065 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
2066 return prev == CANCELLABLE;
2067 }
2068
2069 void ShenandoahHeap::cancel_concurrent_mark() {
2070 if (mode()->is_generational()) {
2071 young_generation()->cancel_marking();
2072 old_generation()->cancel_marking();
2073 }
2074
2075 global_generation()->cancel_marking();
2076
2077 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2078 }
2079
2080 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2081 if (try_cancel_gc()) {
2082 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2083 log_info(gc)("%s", msg.buffer());
2084 Events::log(Thread::current(), "%s", msg.buffer());
2085 _cancel_requested_time = os::elapsedTime();
2086 }
2087 }
2088
2089 uint ShenandoahHeap::max_workers() {
2090 return _max_workers;
2091 }
2092
2093 void ShenandoahHeap::stop() {
2094 // The shutdown sequence should be able to terminate when GC is running.
2095
2096 // Step 0. Notify policy to disable event recording.
2097 _shenandoah_policy->record_shutdown();
2098
2099 // Step 1. Notify control thread that we are in shutdown.
2100 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
2101 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
2102 control_thread()->prepare_for_graceful_shutdown();
2103
2104 // Step 2. Notify GC workers that we are cancelling GC.
2105 cancel_gc(GCCause::_shenandoah_stop_vm);
2106
2107 // Step 3. Wait until GC worker exits normally.
2108 control_thread()->stop();
2109 }
2110
2111 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2112 if (!unload_classes()) return;
2113 ClassUnloadingContext ctx(_workers->active_workers(),
2114 true /* unregister_nmethods_during_purge */,
2115 false /* lock_codeblob_free_separately */);
2116
2117 // Unload classes and purge SystemDictionary.
2118 {
2119 ShenandoahPhaseTimings::Phase phase = full_gc ?
2120 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2121 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2122 ShenandoahIsAliveSelector is_alive;
2123 {
2124 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2125 ShenandoahGCPhase gc_phase(phase);
2126 ShenandoahGCWorkerPhase worker_phase(phase);
2127 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2128
2129 uint num_workers = _workers->active_workers();
2130 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
2131 _workers->run_task(&unlink_task);
2132 }
2133 // Release unloaded nmethods's memory.
2134 ClassUnloadingContext::context()->purge_and_free_nmethods();
2135 }
2136
2137 {
2138 ShenandoahGCPhase phase(full_gc ?
2139 ShenandoahPhaseTimings::full_gc_purge_cldg :
2140 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2141 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2142 }
2143 // Resize and verify metaspace
2144 MetaspaceGC::compute_new_size();
2145 DEBUG_ONLY(MetaspaceUtils::verify();)
2146 }
2147
2148 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
2149 // so they should not have forwarded oops.
2150 // However, we do need to "null" dead oops in the roots, if can not be done
2151 // in concurrent cycles.
2152 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2153 uint num_workers = _workers->active_workers();
2154 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2155 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2156 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2157 ShenandoahGCPhase phase(timing_phase);
2158 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2159 // Cleanup weak roots
2160 if (has_forwarded_objects()) {
2161 ShenandoahForwardedIsAliveClosure is_alive;
2162 ShenandoahUpdateRefsClosure keep_alive;
2163 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
2164 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2165 _workers->run_task(&cleaning_task);
2166 } else {
2167 ShenandoahIsAliveClosure is_alive;
2168 #ifdef ASSERT
2169 ShenandoahAssertNotForwardedClosure verify_cl;
2170 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2171 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2172 #else
2173 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2174 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2175 #endif
2176 _workers->run_task(&cleaning_task);
2177 }
2178 }
2179
2180 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2181 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2182 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2183 ShenandoahGCPhase phase(full_gc ?
2184 ShenandoahPhaseTimings::full_gc_purge :
2185 ShenandoahPhaseTimings::degen_gc_purge);
2186 stw_weak_refs(full_gc);
2187 stw_process_weak_roots(full_gc);
2188 stw_unload_classes(full_gc);
2189 }
2190
2191 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2192 set_gc_state(HAS_FORWARDED, cond);
2193 }
2194
2195 void ShenandoahHeap::set_unload_classes(bool uc) {
2196 _unload_classes.set_cond(uc);
2197 }
2198
2199 bool ShenandoahHeap::unload_classes() const {
2200 return _unload_classes.is_set();
2201 }
2202
2203 address ShenandoahHeap::in_cset_fast_test_addr() {
2204 ShenandoahHeap* heap = ShenandoahHeap::heap();
2205 assert(heap->collection_set() != nullptr, "Sanity");
2206 return (address) heap->collection_set()->biased_map_address();
2207 }
2208
2209 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2210 if (mode()->is_generational()) {
2211 young_generation()->reset_bytes_allocated_since_gc_start();
2212 old_generation()->reset_bytes_allocated_since_gc_start();
2213 }
2214
2215 global_generation()->reset_bytes_allocated_since_gc_start();
2216 }
2217
2218 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2219 _degenerated_gc_in_progress.set_cond(in_progress);
2220 }
2221
2222 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2223 _full_gc_in_progress.set_cond(in_progress);
2224 }
2225
2226 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2227 assert (is_full_gc_in_progress(), "should be");
2228 _full_gc_move_in_progress.set_cond(in_progress);
2229 }
2230
2231 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2232 set_gc_state(UPDATEREFS, in_progress);
2233 }
2234
2235 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2236 ShenandoahCodeRoots::register_nmethod(nm);
2237 }
2238
2239 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2240 ShenandoahCodeRoots::unregister_nmethod(nm);
2241 }
2242
2243 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2244 heap_region_containing(o)->record_pin();
2245 }
2246
2247 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2248 ShenandoahHeapRegion* r = heap_region_containing(o);
2249 assert(r != nullptr, "Sanity");
2250 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
2251 r->record_unpin();
2252 }
2253
2254 void ShenandoahHeap::sync_pinned_region_status() {
2255 ShenandoahHeapLocker locker(lock());
2256
2257 for (size_t i = 0; i < num_regions(); i++) {
2258 ShenandoahHeapRegion *r = get_region(i);
2259 if (r->is_active()) {
2260 if (r->is_pinned()) {
2261 if (r->pin_count() == 0) {
2262 r->make_unpinned();
2263 }
2264 } else {
2265 if (r->pin_count() > 0) {
2266 r->make_pinned();
2267 }
2268 }
2269 }
2270 }
2271
2272 assert_pinned_region_status();
2273 }
2274
2275 #ifdef ASSERT
2276 void ShenandoahHeap::assert_pinned_region_status() {
2277 for (size_t i = 0; i < num_regions(); i++) {
2278 ShenandoahHeapRegion* r = get_region(i);
2279 shenandoah_assert_generations_reconciled();
2280 if (gc_generation()->contains(r)) {
2281 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2282 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2283 }
2284 }
2285 }
2286 #endif
2287
2288 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2289 return _gc_timer;
2290 }
2291
2292 void ShenandoahHeap::prepare_concurrent_roots() {
2293 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2294 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2295 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2296 set_concurrent_weak_root_in_progress(true);
2297 if (unload_classes()) {
2298 _unloader.prepare();
2299 }
2300 }
2301
2302 void ShenandoahHeap::finish_concurrent_roots() {
2303 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2304 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2305 if (unload_classes()) {
2306 _unloader.finish();
2307 }
2308 }
2309
2310 #ifdef ASSERT
2311 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2312 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2313
2314 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2315 // Use ParallelGCThreads inside safepoints
2316 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2317 ParallelGCThreads, nworkers);
2318 } else {
2319 // Use ConcGCThreads outside safepoints
2320 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2321 ConcGCThreads, nworkers);
2322 }
2323 }
2324 #endif
2325
2326 ShenandoahVerifier* ShenandoahHeap::verifier() {
2327 guarantee(ShenandoahVerify, "Should be enabled");
2328 assert (_verifier != nullptr, "sanity");
2329 return _verifier;
2330 }
2331
2332 template<bool CONCURRENT>
2333 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2334 private:
2335 ShenandoahHeap* _heap;
2336 ShenandoahRegionIterator* _regions;
2337 public:
2338 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2339 WorkerTask("Shenandoah Update References"),
2340 _heap(ShenandoahHeap::heap()),
2341 _regions(regions) {
2342 }
2343
2344 void work(uint worker_id) {
2345 if (CONCURRENT) {
2346 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2347 ShenandoahSuspendibleThreadSetJoiner stsj;
2348 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2349 } else {
2350 ShenandoahParallelWorkerSession worker_session(worker_id);
2351 do_work<ShenandoahSTWUpdateRefsClosure>(worker_id);
2352 }
2353 }
2354
2355 private:
2356 template<class T>
2357 void do_work(uint worker_id) {
2358 if (CONCURRENT && (worker_id == 0)) {
2359 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2360 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2361 size_t cset_regions = _heap->collection_set()->count();
2362
2363 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2364 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2365 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2366 // next GC cycle.
2367 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2368 }
2369 // If !CONCURRENT, there's no value in expanding Mutator free set
2370 T cl;
2371 ShenandoahHeapRegion* r = _regions->next();
2372 while (r != nullptr) {
2373 HeapWord* update_watermark = r->get_update_watermark();
2374 assert (update_watermark >= r->bottom(), "sanity");
2375 if (r->is_active() && !r->is_cset()) {
2376 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2377 if (ShenandoahPacing) {
2378 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2379 }
2380 }
2381 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2382 return;
2383 }
2384 r = _regions->next();
2385 }
2386 }
2387 };
2388
2389 void ShenandoahHeap::update_heap_references(bool concurrent) {
2390 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2391
2392 if (concurrent) {
2393 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2394 workers()->run_task(&task);
2395 } else {
2396 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2397 workers()->run_task(&task);
2398 }
2399 }
2400
2401 ShenandoahSynchronizePinnedRegionStates::ShenandoahSynchronizePinnedRegionStates() : _lock(ShenandoahHeap::heap()->lock()) { }
2402
2403 void ShenandoahSynchronizePinnedRegionStates::heap_region_do(ShenandoahHeapRegion* r) {
2404 // Drop "pinned" state from regions that no longer have a pinned count. Put
2405 // regions with a pinned count into the "pinned" state.
2406 if (r->is_active()) {
2407 if (r->is_pinned()) {
2408 if (r->pin_count() == 0) {
2409 ShenandoahHeapLocker locker(_lock);
2410 r->make_unpinned();
2411 }
2412 } else {
2413 if (r->pin_count() > 0) {
2414 ShenandoahHeapLocker locker(_lock);
2415 r->make_pinned();
2416 }
2417 }
2418 }
2419 }
2420
2421 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2422 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2423 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2424
2425 {
2426 ShenandoahGCPhase phase(concurrent ?
2427 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2428 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2429
2430 final_update_refs_update_region_states();
2431
2432 assert_pinned_region_status();
2433 }
2434
2435 {
2436 ShenandoahGCPhase phase(concurrent ?
2437 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2438 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2439 trash_cset_regions();
2440 }
2441 }
2442
2443 void ShenandoahHeap::final_update_refs_update_region_states() {
2444 ShenandoahSynchronizePinnedRegionStates cl;
2445 parallel_heap_region_iterate(&cl);
2446 }
2447
2448 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2449 ShenandoahGCPhase phase(concurrent ?
2450 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2451 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2452 ShenandoahHeapLocker locker(lock());
2453 size_t young_cset_regions, old_cset_regions;
2454 size_t first_old_region, last_old_region, old_region_count;
2455 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count);
2456 // If there are no old regions, first_old_region will be greater than last_old_region
2457 assert((first_old_region > last_old_region) ||
2458 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2459 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2460 "sanity: old_region_count: " SIZE_FORMAT ", first_old_region: " SIZE_FORMAT ", last_old_region: " SIZE_FORMAT,
2461 old_region_count, first_old_region, last_old_region);
2462
2463 if (mode()->is_generational()) {
2464 #ifdef ASSERT
2465 if (ShenandoahVerify) {
2466 verifier()->verify_before_rebuilding_free_set();
2467 }
2468 #endif
2469
2470 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2471 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2472 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2473 size_t allocation_runway = gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions);
2474 gen_heap->compute_old_generation_balance(allocation_runway, old_cset_regions);
2475
2476 // Total old_available may have been expanded to hold anticipated promotions. We trigger if the fragmented available
2477 // memory represents more than 16 regions worth of data. Note that fragmentation may increase when we promote regular
2478 // regions in place when many of these regular regions have an abundant amount of available memory within them. Fragmentation
2479 // will decrease as promote-by-copy consumes the available memory within these partially consumed regions.
2480 //
2481 // We consider old-gen to have excessive fragmentation if more than 12.5% of old-gen is free memory that resides
2482 // within partially consumed regions of memory.
2483 }
2484 // Rebuild free set based on adjusted generation sizes.
2485 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, old_region_count);
2486
2487 if (mode()->is_generational()) {
2488 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2489 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2490 old_gen->heuristics()->trigger_maybe(first_old_region, last_old_region, old_region_count, num_regions());
2491 }
2492 }
2493
2494 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2495 print_on(st);
2496 st->cr();
2497 print_heap_regions_on(st);
2498 }
2499
2500 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2501 size_t slice = r->index() / _bitmap_regions_per_slice;
2502
2503 size_t regions_from = _bitmap_regions_per_slice * slice;
2504 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2505 for (size_t g = regions_from; g < regions_to; g++) {
2506 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2507 if (skip_self && g == r->index()) continue;
2508 if (get_region(g)->is_committed()) {
2509 return true;
2510 }
2511 }
2512 return false;
2513 }
2514
2515 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2516 shenandoah_assert_heaplocked();
2517
2518 // Bitmaps in special regions do not need commits
2519 if (_bitmap_region_special) {
2520 return true;
2521 }
2522
2523 if (is_bitmap_slice_committed(r, true)) {
2524 // Some other region from the group is already committed, meaning the bitmap
2525 // slice is already committed, we exit right away.
2526 return true;
2527 }
2528
2529 // Commit the bitmap slice:
2530 size_t slice = r->index() / _bitmap_regions_per_slice;
2531 size_t off = _bitmap_bytes_per_slice * slice;
2532 size_t len = _bitmap_bytes_per_slice;
2533 char* start = (char*) _bitmap_region.start() + off;
2534
2535 if (!os::commit_memory(start, len, false)) {
2536 return false;
2537 }
2538
2539 if (AlwaysPreTouch) {
2540 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2541 }
2542
2543 return true;
2544 }
2545
2546 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2547 shenandoah_assert_heaplocked();
2548
2549 // Bitmaps in special regions do not need uncommits
2550 if (_bitmap_region_special) {
2551 return true;
2552 }
2553
2554 if (is_bitmap_slice_committed(r, true)) {
2555 // Some other region from the group is still committed, meaning the bitmap
2556 // slice is should stay committed, exit right away.
2557 return true;
2558 }
2559
2560 // Uncommit the bitmap slice:
2561 size_t slice = r->index() / _bitmap_regions_per_slice;
2562 size_t off = _bitmap_bytes_per_slice * slice;
2563 size_t len = _bitmap_bytes_per_slice;
2564 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2565 return false;
2566 }
2567 return true;
2568 }
2569
2570 void ShenandoahHeap::safepoint_synchronize_begin() {
2571 SuspendibleThreadSet::synchronize();
2572 }
2573
2574 void ShenandoahHeap::safepoint_synchronize_end() {
2575 SuspendibleThreadSet::desynchronize();
2576 }
2577
2578 void ShenandoahHeap::try_inject_alloc_failure() {
2579 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2580 _inject_alloc_failure.set();
2581 os::naked_short_sleep(1);
2582 if (cancelled_gc()) {
2583 log_info(gc)("Allocation failure was successfully injected");
2584 }
2585 }
2586 }
2587
2588 bool ShenandoahHeap::should_inject_alloc_failure() {
2589 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2590 }
2591
2592 void ShenandoahHeap::initialize_serviceability() {
2593 _memory_pool = new ShenandoahMemoryPool(this);
2594 _cycle_memory_manager.add_pool(_memory_pool);
2595 _stw_memory_manager.add_pool(_memory_pool);
2596 }
2597
2598 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2599 GrowableArray<GCMemoryManager*> memory_managers(2);
2600 memory_managers.append(&_cycle_memory_manager);
2601 memory_managers.append(&_stw_memory_manager);
2602 return memory_managers;
2603 }
2604
2605 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2606 GrowableArray<MemoryPool*> memory_pools(1);
2607 memory_pools.append(_memory_pool);
2608 return memory_pools;
2609 }
2610
2611 MemoryUsage ShenandoahHeap::memory_usage() {
2612 return MemoryUsage(_initial_size, used(), committed(), max_capacity());
2613 }
2614
2615 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2616 _heap(ShenandoahHeap::heap()),
2617 _index(0) {}
2618
2619 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2620 _heap(heap),
2621 _index(0) {}
2622
2623 void ShenandoahRegionIterator::reset() {
2624 _index = 0;
2625 }
2626
2627 bool ShenandoahRegionIterator::has_next() const {
2628 return _index < _heap->num_regions();
2629 }
2630
2631 char ShenandoahHeap::gc_state() const {
2632 return _gc_state.raw_value();
2633 }
2634
2635 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2636 #ifdef ASSERT
2637 assert(_liveness_cache != nullptr, "sanity");
2638 assert(worker_id < _max_workers, "sanity");
2639 for (uint i = 0; i < num_regions(); i++) {
2640 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2641 }
2642 #endif
2643 return _liveness_cache[worker_id];
2644 }
2645
2646 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2647 assert(worker_id < _max_workers, "sanity");
2648 assert(_liveness_cache != nullptr, "sanity");
2649 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2650 for (uint i = 0; i < num_regions(); i++) {
2651 ShenandoahLiveData live = ld[i];
2652 if (live > 0) {
2653 ShenandoahHeapRegion* r = get_region(i);
2654 r->increase_live_data_gc_words(live);
2655 ld[i] = 0;
2656 }
2657 }
2658 }
2659
2660 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2661 if (is_idle()) return false;
2662
2663 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2664 // marking phase.
2665 if (is_concurrent_mark_in_progress() &&
2666 !marking_context()->allocated_after_mark_start(obj)) {
2667 return true;
2668 }
2669
2670 // Can not guarantee obj is deeply good.
2671 if (has_forwarded_objects()) {
2672 return true;
2673 }
2674
2675 return false;
2676 }
2677
2678 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2679 if (!mode()->is_generational()) {
2680 return global_generation();
2681 } else if (affiliation == YOUNG_GENERATION) {
2682 return young_generation();
2683 } else if (affiliation == OLD_GENERATION) {
2684 return old_generation();
2685 }
2686
2687 ShouldNotReachHere();
2688 return nullptr;
2689 }
2690
2691 void ShenandoahHeap::log_heap_status(const char* msg) const {
2692 if (mode()->is_generational()) {
2693 young_generation()->log_status(msg);
2694 old_generation()->log_status(msg);
2695 } else {
2696 global_generation()->log_status(msg);
2697 }
2698 }