1 /*
2 * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/universe.hpp"
29
30 #include "gc/shared/classUnloadingContext.hpp"
31 #include "gc/shared/gcArguments.hpp"
32 #include "gc/shared/gcTimer.hpp"
33 #include "gc/shared/gcTraceTime.inline.hpp"
34 #include "gc/shared/locationPrinter.inline.hpp"
35 #include "gc/shared/memAllocator.hpp"
36 #include "gc/shared/plab.hpp"
37 #include "gc/shared/tlab_globals.hpp"
38
39 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
40 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
41 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
42 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
43 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
44 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
45 #include "gc/shenandoah/shenandoahControlThread.hpp"
46 #include "gc/shenandoah/shenandoahFreeSet.hpp"
47 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
48 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
49 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
50 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
51 #include "gc/shenandoah/shenandoahInitLogger.hpp"
52 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
53 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
54 #include "gc/shenandoah/shenandoahMetrics.hpp"
55 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
56 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
57 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
58 #include "gc/shenandoah/shenandoahPadding.hpp"
59 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
60 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
61 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
62 #include "gc/shenandoah/shenandoahSTWMark.hpp"
63 #include "gc/shenandoah/shenandoahUtils.hpp"
64 #include "gc/shenandoah/shenandoahVerifier.hpp"
65 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
66 #include "gc/shenandoah/shenandoahVMOperations.hpp"
67 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
68 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
69 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
70 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
71 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
72 #if INCLUDE_JFR
73 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
74 #endif
75
76 #include "classfile/systemDictionary.hpp"
77 #include "code/codeCache.hpp"
78 #include "memory/classLoaderMetaspace.hpp"
79 #include "memory/metaspaceUtils.hpp"
80 #include "oops/compressedOops.inline.hpp"
81 #include "prims/jvmtiTagMap.hpp"
82 #include "runtime/atomic.hpp"
83 #include "runtime/globals.hpp"
84 #include "runtime/interfaceSupport.inline.hpp"
85 #include "runtime/java.hpp"
86 #include "runtime/orderAccess.hpp"
87 #include "runtime/safepointMechanism.hpp"
88 #include "runtime/vmThread.hpp"
89 #include "services/mallocTracker.hpp"
90 #include "services/memTracker.hpp"
91 #include "utilities/events.hpp"
92 #include "utilities/powerOfTwo.hpp"
93
94 class ShenandoahPretouchHeapTask : public WorkerTask {
95 private:
96 ShenandoahRegionIterator _regions;
97 const size_t _page_size;
98 public:
99 ShenandoahPretouchHeapTask(size_t page_size) :
100 WorkerTask("Shenandoah Pretouch Heap"),
101 _page_size(page_size) {}
102
103 virtual void work(uint worker_id) {
104 ShenandoahHeapRegion* r = _regions.next();
105 while (r != nullptr) {
106 if (r->is_committed()) {
107 os::pretouch_memory(r->bottom(), r->end(), _page_size);
108 }
109 r = _regions.next();
110 }
111 }
112 };
113
114 class ShenandoahPretouchBitmapTask : public WorkerTask {
115 private:
116 ShenandoahRegionIterator _regions;
117 char* _bitmap_base;
118 const size_t _bitmap_size;
119 const size_t _page_size;
120 public:
121 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
122 WorkerTask("Shenandoah Pretouch Bitmap"),
123 _bitmap_base(bitmap_base),
124 _bitmap_size(bitmap_size),
125 _page_size(page_size) {}
126
127 virtual void work(uint worker_id) {
128 ShenandoahHeapRegion* r = _regions.next();
129 while (r != nullptr) {
130 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
131 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
132 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
133
134 if (r->is_committed()) {
135 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
136 }
137
138 r = _regions.next();
139 }
140 }
141 };
142
143 jint ShenandoahHeap::initialize() {
144 //
145 // Figure out heap sizing
146 //
147
148 size_t init_byte_size = InitialHeapSize;
149 size_t min_byte_size = MinHeapSize;
150 size_t max_byte_size = MaxHeapSize;
151 size_t heap_alignment = HeapAlignment;
152
153 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
154
155 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
156 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
157
158 _num_regions = ShenandoahHeapRegion::region_count();
159 assert(_num_regions == (max_byte_size / reg_size_bytes),
160 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
161 _num_regions, max_byte_size, reg_size_bytes);
162
163 // Now we know the number of regions, initialize the heuristics.
164 initialize_heuristics();
165
166 size_t num_committed_regions = init_byte_size / reg_size_bytes;
167 num_committed_regions = MIN2(num_committed_regions, _num_regions);
168 assert(num_committed_regions <= _num_regions, "sanity");
169 _initial_size = num_committed_regions * reg_size_bytes;
170
171 size_t num_min_regions = min_byte_size / reg_size_bytes;
172 num_min_regions = MIN2(num_min_regions, _num_regions);
173 assert(num_min_regions <= _num_regions, "sanity");
174 _minimum_size = num_min_regions * reg_size_bytes;
175
176 // Default to max heap size.
177 _soft_max_size = _num_regions * reg_size_bytes;
178
179 _committed = _initial_size;
180
181 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
182 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
183 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
184
185 //
186 // Reserve and commit memory for heap
187 //
188
189 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
190 initialize_reserved_region(heap_rs);
191 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
192 _heap_region_special = heap_rs.special();
193
194 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
195 "Misaligned heap: " PTR_FORMAT, p2i(base()));
196
197 #if SHENANDOAH_OPTIMIZED_MARKTASK
198 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
199 // Fail if we ever attempt to address more than we can.
200 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
201 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
202 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
203 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
204 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
205 vm_exit_during_initialization("Fatal Error", buf);
206 }
207 #endif
208
209 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
210 if (!_heap_region_special) {
211 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
212 "Cannot commit heap memory");
213 }
214
215 //
216 // Reserve and commit memory for bitmap(s)
217 //
218
219 _bitmap_size = ShenandoahMarkBitMap::compute_size(heap_rs.size());
220 _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
221
222 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
223
224 guarantee(bitmap_bytes_per_region != 0,
225 "Bitmap bytes per region should not be zero");
226 guarantee(is_power_of_2(bitmap_bytes_per_region),
227 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
228
229 if (bitmap_page_size > bitmap_bytes_per_region) {
230 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
231 _bitmap_bytes_per_slice = bitmap_page_size;
232 } else {
233 _bitmap_regions_per_slice = 1;
234 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
235 }
236
237 guarantee(_bitmap_regions_per_slice >= 1,
238 "Should have at least one region per slice: " SIZE_FORMAT,
239 _bitmap_regions_per_slice);
240
241 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
242 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
243 _bitmap_bytes_per_slice, bitmap_page_size);
244
245 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
246 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
247 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
248 _bitmap_region_special = bitmap.special();
249
250 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
251 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
252 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
253 if (!_bitmap_region_special) {
254 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
255 "Cannot commit bitmap memory");
256 }
257
258 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions, _max_workers);
259
260 if (ShenandoahVerify) {
261 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
262 if (!verify_bitmap.special()) {
263 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
264 "Cannot commit verification bitmap memory");
265 }
266 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
267 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
268 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
269 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
270 }
271
272 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
273 ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
274 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
275 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
276 _aux_bitmap_region_special = aux_bitmap.special();
277 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
278
279 //
280 // Create regions and region sets
281 //
282 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
283 size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
284 region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
285
286 ReservedSpace region_storage(region_storage_size, region_page_size);
287 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
288 if (!region_storage.special()) {
289 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
290 "Cannot commit region memory");
291 }
292
293 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
294 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
295 // If not successful, bite a bullet and allocate at whatever address.
296 {
297 size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
298 size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
299
300 uintptr_t min = round_up_power_of_2(cset_align);
301 uintptr_t max = (1u << 30u);
302
303 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
304 char* req_addr = (char*)addr;
305 assert(is_aligned(req_addr, cset_align), "Should be aligned");
306 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size(), req_addr);
307 if (cset_rs.is_reserved()) {
308 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
309 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
310 break;
311 }
312 }
313
314 if (_collection_set == nullptr) {
315 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size());
316 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
317 }
318 }
319
320 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
321 _free_set = new ShenandoahFreeSet(this, _num_regions);
322
323 {
324 ShenandoahHeapLocker locker(lock());
325
326 for (size_t i = 0; i < _num_regions; i++) {
327 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
328 bool is_committed = i < num_committed_regions;
329 void* loc = region_storage.base() + i * region_align;
330
331 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
332 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
333
334 _marking_context->initialize_top_at_mark_start(r);
335 _regions[i] = r;
336 assert(!collection_set()->is_in(i), "New region should not be in collection set");
337 }
338
339 // Initialize to complete
340 _marking_context->mark_complete();
341
342 _free_set->rebuild();
343 }
344
345 if (AlwaysPreTouch) {
346 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
347 // before initialize() below zeroes it with initializing thread. For any given region,
348 // we touch the region and the corresponding bitmaps from the same thread.
349 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
350
351 _pretouch_heap_page_size = heap_page_size;
352 _pretouch_bitmap_page_size = bitmap_page_size;
353
354 #ifdef LINUX
355 // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
356 // pages. But, the kernel needs to know that every small page is used, in order to coalesce
357 // them into huge one. Therefore, we need to pretouch with smaller pages.
358 if (UseTransparentHugePages) {
359 _pretouch_heap_page_size = (size_t)os::vm_page_size();
360 _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
361 }
362 #endif
363
364 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
365 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
366
367 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
368 _workers->run_task(&bcl);
369
370 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
371 _workers->run_task(&hcl);
372 }
373
374 //
375 // Initialize the rest of GC subsystems
376 //
377
378 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
379 for (uint worker = 0; worker < _max_workers; worker++) {
380 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
381 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
382 }
383
384 // There should probably be Shenandoah-specific options for these,
385 // just as there are G1-specific options.
386 {
387 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
388 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
389 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
390 }
391
392 _monitoring_support = new ShenandoahMonitoringSupport(this);
393 _phase_timings = new ShenandoahPhaseTimings(max_workers());
394 ShenandoahCodeRoots::initialize();
395
396 if (ShenandoahPacing) {
397 _pacer = new ShenandoahPacer(this);
398 _pacer->setup_for_idle();
399 } else {
400 _pacer = nullptr;
401 }
402
403 _control_thread = new ShenandoahControlThread();
404
405 ShenandoahInitLogger::print();
406
407 return JNI_OK;
408 }
409
410 void ShenandoahHeap::initialize_mode() {
411 if (ShenandoahGCMode != nullptr) {
412 if (strcmp(ShenandoahGCMode, "satb") == 0) {
413 _gc_mode = new ShenandoahSATBMode();
414 } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
415 _gc_mode = new ShenandoahIUMode();
416 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
417 _gc_mode = new ShenandoahPassiveMode();
418 } else {
419 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
420 }
421 } else {
422 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
423 }
424 _gc_mode->initialize_flags();
425 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
426 vm_exit_during_initialization(
427 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
428 _gc_mode->name()));
429 }
430 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
431 vm_exit_during_initialization(
432 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
433 _gc_mode->name()));
434 }
435 }
436
437 void ShenandoahHeap::initialize_heuristics() {
438 assert(_gc_mode != nullptr, "Must be initialized");
439 _heuristics = _gc_mode->initialize_heuristics();
440
441 if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
442 vm_exit_during_initialization(
443 err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
444 _heuristics->name()));
445 }
446 if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
447 vm_exit_during_initialization(
448 err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
449 _heuristics->name()));
450 }
451 }
452
453 #ifdef _MSC_VER
454 #pragma warning( push )
455 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
456 #endif
457
458 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
459 CollectedHeap(),
460 _initial_size(0),
461 _used(0),
462 _committed(0),
463 _bytes_allocated_since_gc_start(0),
464 _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
465 _workers(nullptr),
466 _safepoint_workers(nullptr),
467 _heap_region_special(false),
468 _num_regions(0),
469 _regions(nullptr),
470 _update_refs_iterator(this),
471 _gc_state_changed(false),
472 _control_thread(nullptr),
473 _shenandoah_policy(policy),
474 _gc_mode(nullptr),
475 _heuristics(nullptr),
476 _free_set(nullptr),
477 _pacer(nullptr),
478 _verifier(nullptr),
479 _phase_timings(nullptr),
480 _monitoring_support(nullptr),
481 _memory_pool(nullptr),
482 _stw_memory_manager("Shenandoah Pauses"),
483 _cycle_memory_manager("Shenandoah Cycles"),
484 _gc_timer(new ConcurrentGCTimer()),
485 _soft_ref_policy(),
486 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
487 _ref_processor(new ShenandoahReferenceProcessor(MAX2(_max_workers, 1U))),
488 _marking_context(nullptr),
489 _bitmap_size(0),
490 _bitmap_regions_per_slice(0),
491 _bitmap_bytes_per_slice(0),
492 _bitmap_region_special(false),
493 _aux_bitmap_region_special(false),
494 _liveness_cache(nullptr),
495 _collection_set(nullptr)
496 {
497 // Initialize GC mode early, so we can adjust barrier support
498 initialize_mode();
499 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
500
501 _max_workers = MAX2(_max_workers, 1U);
502 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
503 if (_workers == nullptr) {
504 vm_exit_during_initialization("Failed necessary allocation.");
505 } else {
506 _workers->initialize_workers();
507 }
508
509 if (ParallelGCThreads > 1) {
510 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread",
511 ParallelGCThreads);
512 _safepoint_workers->initialize_workers();
513 }
514 }
515
516 #ifdef _MSC_VER
517 #pragma warning( pop )
518 #endif
519
520 class ShenandoahResetBitmapTask : public WorkerTask {
521 private:
522 ShenandoahRegionIterator _regions;
523
524 public:
525 ShenandoahResetBitmapTask() :
526 WorkerTask("Shenandoah Reset Bitmap") {}
527
528 void work(uint worker_id) {
529 ShenandoahHeapRegion* region = _regions.next();
530 ShenandoahHeap* heap = ShenandoahHeap::heap();
531 ShenandoahMarkingContext* const ctx = heap->marking_context();
532 while (region != nullptr) {
533 if (heap->is_bitmap_slice_committed(region)) {
534 ctx->clear_bitmap(region);
535 }
536 region = _regions.next();
537 }
538 }
539 };
540
541 void ShenandoahHeap::reset_mark_bitmap() {
542 assert_gc_workers(_workers->active_workers());
543 mark_incomplete_marking_context();
544
545 ShenandoahResetBitmapTask task;
546 _workers->run_task(&task);
547 }
548
549 void ShenandoahHeap::print_on(outputStream* st) const {
550 st->print_cr("Shenandoah Heap");
551 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
552 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
553 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
554 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
555 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
556 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
557 num_regions(),
558 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
559 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
560
561 st->print("Status: ");
562 if (has_forwarded_objects()) st->print("has forwarded objects, ");
563 if (is_concurrent_mark_in_progress()) st->print("marking, ");
564 if (is_evacuation_in_progress()) st->print("evacuating, ");
565 if (is_update_refs_in_progress()) st->print("updating refs, ");
566 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
567 if (is_full_gc_in_progress()) st->print("full gc, ");
568 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
569 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
570 if (is_concurrent_strong_root_in_progress() &&
571 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
572
573 if (cancelled_gc()) {
574 st->print("cancelled");
575 } else {
576 st->print("not cancelled");
577 }
578 st->cr();
579
580 st->print_cr("Reserved region:");
581 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
582 p2i(reserved_region().start()),
583 p2i(reserved_region().end()));
584
585 ShenandoahCollectionSet* cset = collection_set();
586 st->print_cr("Collection set:");
587 if (cset != nullptr) {
588 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
589 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
590 } else {
591 st->print_cr(" (null)");
592 }
593
594 st->cr();
595 MetaspaceUtils::print_on(st);
596
597 if (Verbose) {
598 st->cr();
599 print_heap_regions_on(st);
600 }
601 }
602
603 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
604 public:
605 void do_thread(Thread* thread) {
606 assert(thread != nullptr, "Sanity");
607 assert(thread->is_Worker_thread(), "Only worker thread expected");
608 ShenandoahThreadLocalData::initialize_gclab(thread);
609 }
610 };
611
612 void ShenandoahHeap::post_initialize() {
613 CollectedHeap::post_initialize();
614 MutexLocker ml(Threads_lock);
615
616 ShenandoahInitWorkerGCLABClosure init_gclabs;
617 _workers->threads_do(&init_gclabs);
618
619 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
620 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
621 _workers->set_initialize_gclab();
622 if (_safepoint_workers != nullptr) {
623 _safepoint_workers->threads_do(&init_gclabs);
624 _safepoint_workers->set_initialize_gclab();
625 }
626
627 _heuristics->initialize();
628
629 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
630 }
631
632 size_t ShenandoahHeap::used() const {
633 return Atomic::load(&_used);
634 }
635
636 size_t ShenandoahHeap::committed() const {
637 return Atomic::load(&_committed);
638 }
639
640 void ShenandoahHeap::increase_committed(size_t bytes) {
641 shenandoah_assert_heaplocked_or_safepoint();
642 _committed += bytes;
643 }
644
645 void ShenandoahHeap::decrease_committed(size_t bytes) {
646 shenandoah_assert_heaplocked_or_safepoint();
647 _committed -= bytes;
648 }
649
650 void ShenandoahHeap::increase_used(size_t bytes) {
651 Atomic::add(&_used, bytes, memory_order_relaxed);
652 }
653
654 void ShenandoahHeap::set_used(size_t bytes) {
655 Atomic::store(&_used, bytes);
656 }
657
658 void ShenandoahHeap::decrease_used(size_t bytes) {
659 assert(used() >= bytes, "never decrease heap size by more than we've left");
660 Atomic::sub(&_used, bytes, memory_order_relaxed);
661 }
662
663 void ShenandoahHeap::increase_allocated(size_t bytes) {
664 Atomic::add(&_bytes_allocated_since_gc_start, bytes, memory_order_relaxed);
665 }
666
667 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
668 size_t bytes = words * HeapWordSize;
669 if (!waste) {
670 increase_used(bytes);
671 }
672 increase_allocated(bytes);
673 if (ShenandoahPacing) {
674 control_thread()->pacing_notify_alloc(words);
675 if (waste) {
676 pacer()->claim_for_alloc(words, true);
677 }
678 }
679 }
680
681 size_t ShenandoahHeap::capacity() const {
682 return committed();
683 }
684
685 size_t ShenandoahHeap::max_capacity() const {
686 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
687 }
688
689 size_t ShenandoahHeap::soft_max_capacity() const {
690 size_t v = Atomic::load(&_soft_max_size);
691 assert(min_capacity() <= v && v <= max_capacity(),
692 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
693 min_capacity(), v, max_capacity());
694 return v;
695 }
696
697 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
698 assert(min_capacity() <= v && v <= max_capacity(),
699 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
700 min_capacity(), v, max_capacity());
701 Atomic::store(&_soft_max_size, v);
702 }
703
704 size_t ShenandoahHeap::min_capacity() const {
705 return _minimum_size;
706 }
707
708 size_t ShenandoahHeap::initial_capacity() const {
709 return _initial_size;
710 }
711
712 bool ShenandoahHeap::is_in(const void* p) const {
713 HeapWord* heap_base = (HeapWord*) base();
714 HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
715 return p >= heap_base && p < last_region_end;
716 }
717
718 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
719 assert (ShenandoahUncommit, "should be enabled");
720
721 // Application allocates from the beginning of the heap, and GC allocates at
722 // the end of it. It is more efficient to uncommit from the end, so that applications
723 // could enjoy the near committed regions. GC allocations are much less frequent,
724 // and therefore can accept the committing costs.
725
726 size_t count = 0;
727 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
728 ShenandoahHeapRegion* r = get_region(i - 1);
729 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
730 ShenandoahHeapLocker locker(lock());
731 if (r->is_empty_committed()) {
732 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
733 break;
734 }
735
736 r->make_uncommitted();
737 count++;
738 }
739 }
740 SpinPause(); // allow allocators to take the lock
741 }
742
743 if (count > 0) {
744 control_thread()->notify_heap_changed();
745 }
746 }
747
748 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
749 // New object should fit the GCLAB size
750 size_t min_size = MAX2(size, PLAB::min_size());
751
752 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
753 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
754 new_size = MIN2(new_size, PLAB::max_size());
755 new_size = MAX2(new_size, PLAB::min_size());
756
757 // Record new heuristic value even if we take any shortcut. This captures
758 // the case when moderately-sized objects always take a shortcut. At some point,
759 // heuristics should catch up with them.
760 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
761
762 if (new_size < size) {
763 // New size still does not fit the object. Fall back to shared allocation.
764 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
765 return nullptr;
766 }
767
768 // Retire current GCLAB, and allocate a new one.
769 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
770 gclab->retire();
771
772 size_t actual_size = 0;
773 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
774 if (gclab_buf == nullptr) {
775 return nullptr;
776 }
777
778 assert (size <= actual_size, "allocation should fit");
779
780 if (ZeroTLAB) {
781 // ..and clear it.
782 Copy::zero_to_words(gclab_buf, actual_size);
783 } else {
784 // ...and zap just allocated object.
785 #ifdef ASSERT
786 // Skip mangling the space corresponding to the object header to
787 // ensure that the returned space is not considered parsable by
788 // any concurrent GC thread.
789 size_t hdr_size = oopDesc::header_size();
790 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
791 #endif // ASSERT
792 }
793 gclab->set_buf(gclab_buf, actual_size);
794 return gclab->allocate(size);
795 }
796
797 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
798 size_t requested_size,
799 size_t* actual_size) {
800 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
801 HeapWord* res = allocate_memory(req);
802 if (res != nullptr) {
803 *actual_size = req.actual_size();
804 } else {
805 *actual_size = 0;
806 }
807 return res;
808 }
809
810 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
811 size_t word_size,
812 size_t* actual_size) {
813 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
814 HeapWord* res = allocate_memory(req);
815 if (res != nullptr) {
816 *actual_size = req.actual_size();
817 } else {
818 *actual_size = 0;
819 }
820 return res;
821 }
822
823 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
824 intptr_t pacer_epoch = 0;
825 bool in_new_region = false;
826 HeapWord* result = nullptr;
827
828 if (req.is_mutator_alloc()) {
829 if (ShenandoahPacing) {
830 pacer()->pace_for_alloc(req.size());
831 pacer_epoch = pacer()->epoch();
832 }
833
834 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
835 result = allocate_memory_under_lock(req, in_new_region);
836 }
837
838 // Allocation failed, block until control thread reacted, then retry allocation.
839 //
840 // It might happen that one of the threads requesting allocation would unblock
841 // way later after GC happened, only to fail the second allocation, because
842 // other threads have already depleted the free storage. In this case, a better
843 // strategy is to try again, as long as GC makes progress (or until at least
844 // one full GC has completed).
845 size_t original_count = shenandoah_policy()->full_gc_count();
846 while (result == nullptr
847 && (_progress_last_gc.is_set() || original_count == shenandoah_policy()->full_gc_count())) {
848 control_thread()->handle_alloc_failure(req);
849 result = allocate_memory_under_lock(req, in_new_region);
850 }
851 } else {
852 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
853 result = allocate_memory_under_lock(req, in_new_region);
854 // Do not call handle_alloc_failure() here, because we cannot block.
855 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
856 }
857
858 if (in_new_region) {
859 control_thread()->notify_heap_changed();
860 }
861
862 if (result != nullptr) {
863 size_t requested = req.size();
864 size_t actual = req.actual_size();
865
866 assert (req.is_lab_alloc() || (requested == actual),
867 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
868 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
869
870 if (req.is_mutator_alloc()) {
871 notify_mutator_alloc_words(actual, false);
872
873 // If we requested more than we were granted, give the rest back to pacer.
874 // This only matters if we are in the same pacing epoch: do not try to unpace
875 // over the budget for the other phase.
876 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
877 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
878 }
879 } else {
880 increase_used(actual*HeapWordSize);
881 }
882 }
883
884 return result;
885 }
886
887 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
888 ShenandoahHeapLocker locker(lock());
889 return _free_set->allocate(req, in_new_region);
890 }
891
892 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
893 bool* gc_overhead_limit_was_exceeded) {
894 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
895 return allocate_memory(req);
896 }
897
898 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
899 size_t size,
900 Metaspace::MetadataType mdtype) {
901 MetaWord* result;
902
903 // Inform metaspace OOM to GC heuristics if class unloading is possible.
904 if (heuristics()->can_unload_classes()) {
905 ShenandoahHeuristics* h = heuristics();
906 h->record_metaspace_oom();
907 }
908
909 // Expand and retry allocation
910 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
911 if (result != nullptr) {
912 return result;
913 }
914
915 // Start full GC
916 collect(GCCause::_metadata_GC_clear_soft_refs);
917
918 // Retry allocation
919 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
920 if (result != nullptr) {
921 return result;
922 }
923
924 // Expand and retry allocation
925 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
926 if (result != nullptr) {
927 return result;
928 }
929
930 // Out of memory
931 return nullptr;
932 }
933
934 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
935 private:
936 ShenandoahHeap* const _heap;
937 Thread* const _thread;
938 public:
939 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
940 _heap(heap), _thread(Thread::current()) {}
941
942 void do_object(oop p) {
943 shenandoah_assert_marked(nullptr, p);
944 if (!p->is_forwarded()) {
945 _heap->evacuate_object(p, _thread);
946 }
947 }
948 };
949
950 class ShenandoahEvacuationTask : public WorkerTask {
951 private:
952 ShenandoahHeap* const _sh;
953 ShenandoahCollectionSet* const _cs;
954 bool _concurrent;
955 public:
956 ShenandoahEvacuationTask(ShenandoahHeap* sh,
957 ShenandoahCollectionSet* cs,
958 bool concurrent) :
959 WorkerTask("Shenandoah Evacuation"),
960 _sh(sh),
961 _cs(cs),
962 _concurrent(concurrent)
963 {}
964
965 void work(uint worker_id) {
966 if (_concurrent) {
967 ShenandoahConcurrentWorkerSession worker_session(worker_id);
968 ShenandoahSuspendibleThreadSetJoiner stsj;
969 ShenandoahEvacOOMScope oom_evac_scope;
970 do_work();
971 } else {
972 ShenandoahParallelWorkerSession worker_session(worker_id);
973 ShenandoahEvacOOMScope oom_evac_scope;
974 do_work();
975 }
976 }
977
978 private:
979 void do_work() {
980 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
981 ShenandoahHeapRegion* r;
982 while ((r =_cs->claim_next()) != nullptr) {
983 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
984 _sh->marked_object_iterate(r, &cl);
985
986 if (ShenandoahPacing) {
987 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
988 }
989
990 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
991 break;
992 }
993 }
994 }
995 };
996
997 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
998 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
999 workers()->run_task(&task);
1000 }
1001
1002 void ShenandoahHeap::trash_cset_regions() {
1003 ShenandoahHeapLocker locker(lock());
1004
1005 ShenandoahCollectionSet* set = collection_set();
1006 ShenandoahHeapRegion* r;
1007 set->clear_current_index();
1008 while ((r = set->next()) != nullptr) {
1009 r->make_trash();
1010 }
1011 collection_set()->clear();
1012 }
1013
1014 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1015 st->print_cr("Heap Regions:");
1016 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1017 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1018 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1019 st->print_cr("UWM=update watermark, U=used");
1020 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1021 st->print_cr("S=shared allocs, L=live data");
1022 st->print_cr("CP=critical pins");
1023
1024 for (size_t i = 0; i < num_regions(); i++) {
1025 get_region(i)->print_on(st);
1026 }
1027 }
1028
1029 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1030 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1031
1032 oop humongous_obj = cast_to_oop(start->bottom());
1033 size_t size = humongous_obj->size();
1034 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1035 size_t index = start->index() + required_regions - 1;
1036
1037 assert(!start->has_live(), "liveness must be zero");
1038
1039 for(size_t i = 0; i < required_regions; i++) {
1040 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1041 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1042 ShenandoahHeapRegion* region = get_region(index --);
1043
1044 assert(region->is_humongous(), "expect correct humongous start or continuation");
1045 assert(!region->is_cset(), "Humongous region should not be in collection set");
1046
1047 region->make_trash_immediate();
1048 }
1049 }
1050
1051 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1052 public:
1053 ShenandoahCheckCleanGCLABClosure() {}
1054 void do_thread(Thread* thread) {
1055 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1056 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1057 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1058 }
1059 };
1060
1061 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1062 private:
1063 bool const _resize;
1064 public:
1065 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1066 void do_thread(Thread* thread) {
1067 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1068 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1069 gclab->retire();
1070 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1071 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1072 }
1073 }
1074 };
1075
1076 void ShenandoahHeap::labs_make_parsable() {
1077 assert(UseTLAB, "Only call with UseTLAB");
1078
1079 ShenandoahRetireGCLABClosure cl(false);
1080
1081 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1082 ThreadLocalAllocBuffer& tlab = t->tlab();
1083 tlab.make_parsable();
1084 cl.do_thread(t);
1085 }
1086
1087 workers()->threads_do(&cl);
1088 }
1089
1090 void ShenandoahHeap::tlabs_retire(bool resize) {
1091 assert(UseTLAB, "Only call with UseTLAB");
1092 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1093
1094 ThreadLocalAllocStats stats;
1095
1096 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1097 ThreadLocalAllocBuffer& tlab = t->tlab();
1098 tlab.retire(&stats);
1099 if (resize) {
1100 tlab.resize();
1101 }
1102 }
1103
1104 stats.publish();
1105
1106 #ifdef ASSERT
1107 ShenandoahCheckCleanGCLABClosure cl;
1108 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1109 cl.do_thread(t);
1110 }
1111 workers()->threads_do(&cl);
1112 #endif
1113 }
1114
1115 void ShenandoahHeap::gclabs_retire(bool resize) {
1116 assert(UseTLAB, "Only call with UseTLAB");
1117 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1118
1119 ShenandoahRetireGCLABClosure cl(resize);
1120 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1121 cl.do_thread(t);
1122 }
1123 workers()->threads_do(&cl);
1124
1125 if (safepoint_workers() != nullptr) {
1126 safepoint_workers()->threads_do(&cl);
1127 }
1128 }
1129
1130 // Returns size in bytes
1131 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1132 // Return the max allowed size, and let the allocation path
1133 // figure out the safe size for current allocation.
1134 return ShenandoahHeapRegion::max_tlab_size_bytes();
1135 }
1136
1137 size_t ShenandoahHeap::max_tlab_size() const {
1138 // Returns size in words
1139 return ShenandoahHeapRegion::max_tlab_size_words();
1140 }
1141
1142 void ShenandoahHeap::collect(GCCause::Cause cause) {
1143 control_thread()->request_gc(cause);
1144 }
1145
1146 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1147 //assert(false, "Shouldn't need to do full collections");
1148 }
1149
1150 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1151 ShenandoahHeapRegion* r = heap_region_containing(addr);
1152 if (r != nullptr) {
1153 return r->block_start(addr);
1154 }
1155 return nullptr;
1156 }
1157
1158 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1159 ShenandoahHeapRegion* r = heap_region_containing(addr);
1160 return r->block_is_obj(addr);
1161 }
1162
1163 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1164 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1165 }
1166
1167 void ShenandoahHeap::prepare_for_verify() {
1168 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1169 labs_make_parsable();
1170 }
1171 }
1172
1173 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1174 tcl->do_thread(_control_thread);
1175 workers()->threads_do(tcl);
1176 if (_safepoint_workers != nullptr) {
1177 _safepoint_workers->threads_do(tcl);
1178 }
1179 }
1180
1181 void ShenandoahHeap::print_tracing_info() const {
1182 LogTarget(Info, gc, stats) lt;
1183 if (lt.is_enabled()) {
1184 ResourceMark rm;
1185 LogStream ls(lt);
1186
1187 phase_timings()->print_global_on(&ls);
1188
1189 ls.cr();
1190 ls.cr();
1191
1192 shenandoah_policy()->print_gc_stats(&ls);
1193
1194 ls.cr();
1195 ls.cr();
1196 }
1197 }
1198
1199 void ShenandoahHeap::verify(VerifyOption vo) {
1200 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1201 if (ShenandoahVerify) {
1202 verifier()->verify_generic(vo);
1203 } else {
1204 // TODO: Consider allocating verification bitmaps on demand,
1205 // and turn this on unconditionally.
1206 }
1207 }
1208 }
1209 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1210 return _free_set->capacity();
1211 }
1212
1213 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1214 private:
1215 MarkBitMap* _bitmap;
1216 ShenandoahScanObjectStack* _oop_stack;
1217 ShenandoahHeap* const _heap;
1218 ShenandoahMarkingContext* const _marking_context;
1219
1220 template <class T>
1221 void do_oop_work(T* p) {
1222 T o = RawAccess<>::oop_load(p);
1223 if (!CompressedOops::is_null(o)) {
1224 oop obj = CompressedOops::decode_not_null(o);
1225 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1226 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1227 return;
1228 }
1229 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1230
1231 assert(oopDesc::is_oop(obj), "must be a valid oop");
1232 if (!_bitmap->is_marked(obj)) {
1233 _bitmap->mark(obj);
1234 _oop_stack->push(obj);
1235 }
1236 }
1237 }
1238 public:
1239 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1240 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1241 _marking_context(_heap->marking_context()) {}
1242 void do_oop(oop* p) { do_oop_work(p); }
1243 void do_oop(narrowOop* p) { do_oop_work(p); }
1244 };
1245
1246 /*
1247 * This is public API, used in preparation of object_iterate().
1248 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1249 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1250 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1251 */
1252 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1253 // No-op.
1254 }
1255
1256 /*
1257 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1258 *
1259 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1260 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1261 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1262 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1263 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1264 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1265 * wiped the bitmap in preparation for next marking).
1266 *
1267 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1268 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1269 * is allowed to report dead objects, but is not required to do so.
1270 */
1271 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1272 // Reset bitmap
1273 if (!prepare_aux_bitmap_for_iteration())
1274 return;
1275
1276 ShenandoahScanObjectStack oop_stack;
1277 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1278 // Seed the stack with root scan
1279 scan_roots_for_iteration(&oop_stack, &oops);
1280
1281 // Work through the oop stack to traverse heap
1282 while (! oop_stack.is_empty()) {
1283 oop obj = oop_stack.pop();
1284 assert(oopDesc::is_oop(obj), "must be a valid oop");
1285 cl->do_object(obj);
1286 obj->oop_iterate(&oops);
1287 }
1288
1289 assert(oop_stack.is_empty(), "should be empty");
1290 // Reclaim bitmap
1291 reclaim_aux_bitmap_for_iteration();
1292 }
1293
1294 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1295 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1296
1297 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1298 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1299 return false;
1300 }
1301 // Reset bitmap
1302 _aux_bit_map.clear();
1303 return true;
1304 }
1305
1306 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1307 // Process GC roots according to current GC cycle
1308 // This populates the work stack with initial objects
1309 // It is important to relinquish the associated locks before diving
1310 // into heap dumper
1311 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1312 ShenandoahHeapIterationRootScanner rp(n_workers);
1313 rp.roots_do(oops);
1314 }
1315
1316 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1317 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1318 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1319 }
1320 }
1321
1322 // Closure for parallelly iterate objects
1323 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1324 private:
1325 MarkBitMap* _bitmap;
1326 ShenandoahObjToScanQueue* _queue;
1327 ShenandoahHeap* const _heap;
1328 ShenandoahMarkingContext* const _marking_context;
1329
1330 template <class T>
1331 void do_oop_work(T* p) {
1332 T o = RawAccess<>::oop_load(p);
1333 if (!CompressedOops::is_null(o)) {
1334 oop obj = CompressedOops::decode_not_null(o);
1335 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1336 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1337 return;
1338 }
1339 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1340
1341 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1342 if (_bitmap->par_mark(obj)) {
1343 _queue->push(ShenandoahMarkTask(obj));
1344 }
1345 }
1346 }
1347 public:
1348 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1349 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1350 _marking_context(_heap->marking_context()) {}
1351 void do_oop(oop* p) { do_oop_work(p); }
1352 void do_oop(narrowOop* p) { do_oop_work(p); }
1353 };
1354
1355 // Object iterator for parallel heap iteraion.
1356 // The root scanning phase happenes in construction as a preparation of
1357 // parallel marking queues.
1358 // Every worker processes it's own marking queue. work-stealing is used
1359 // to balance workload.
1360 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1361 private:
1362 uint _num_workers;
1363 bool _init_ready;
1364 MarkBitMap* _aux_bit_map;
1365 ShenandoahHeap* _heap;
1366 ShenandoahScanObjectStack _roots_stack; // global roots stack
1367 ShenandoahObjToScanQueueSet* _task_queues;
1368 public:
1369 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1370 _num_workers(num_workers),
1371 _init_ready(false),
1372 _aux_bit_map(bitmap),
1373 _heap(ShenandoahHeap::heap()) {
1374 // Initialize bitmap
1375 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1376 if (!_init_ready) {
1377 return;
1378 }
1379
1380 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1381 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1382
1383 _init_ready = prepare_worker_queues();
1384 }
1385
1386 ~ShenandoahParallelObjectIterator() {
1387 // Reclaim bitmap
1388 _heap->reclaim_aux_bitmap_for_iteration();
1389 // Reclaim queue for workers
1390 if (_task_queues!= nullptr) {
1391 for (uint i = 0; i < _num_workers; ++i) {
1392 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1393 if (q != nullptr) {
1394 delete q;
1395 _task_queues->register_queue(i, nullptr);
1396 }
1397 }
1398 delete _task_queues;
1399 _task_queues = nullptr;
1400 }
1401 }
1402
1403 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1404 if (_init_ready) {
1405 object_iterate_parallel(cl, worker_id, _task_queues);
1406 }
1407 }
1408
1409 private:
1410 // Divide global root_stack into worker queues
1411 bool prepare_worker_queues() {
1412 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1413 // Initialize queues for every workers
1414 for (uint i = 0; i < _num_workers; ++i) {
1415 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1416 _task_queues->register_queue(i, task_queue);
1417 }
1418 // Divide roots among the workers. Assume that object referencing distribution
1419 // is related with root kind, use round-robin to make every worker have same chance
1420 // to process every kind of roots
1421 size_t roots_num = _roots_stack.size();
1422 if (roots_num == 0) {
1423 // No work to do
1424 return false;
1425 }
1426
1427 for (uint j = 0; j < roots_num; j++) {
1428 uint stack_id = j % _num_workers;
1429 oop obj = _roots_stack.pop();
1430 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1431 }
1432 return true;
1433 }
1434
1435 void object_iterate_parallel(ObjectClosure* cl,
1436 uint worker_id,
1437 ShenandoahObjToScanQueueSet* queue_set) {
1438 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1439 assert(queue_set != nullptr, "task queue must not be null");
1440
1441 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1442 assert(q != nullptr, "object iterate queue must not be null");
1443
1444 ShenandoahMarkTask t;
1445 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1446
1447 // Work through the queue to traverse heap.
1448 // Steal when there is no task in queue.
1449 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1450 oop obj = t.obj();
1451 assert(oopDesc::is_oop(obj), "must be a valid oop");
1452 cl->do_object(obj);
1453 obj->oop_iterate(&oops);
1454 }
1455 assert(q->is_empty(), "should be empty");
1456 }
1457 };
1458
1459 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1460 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1461 }
1462
1463 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1464 void ShenandoahHeap::keep_alive(oop obj) {
1465 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1466 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1467 }
1468 }
1469
1470 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1471 for (size_t i = 0; i < num_regions(); i++) {
1472 ShenandoahHeapRegion* current = get_region(i);
1473 blk->heap_region_do(current);
1474 }
1475 }
1476
1477 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1478 private:
1479 ShenandoahHeap* const _heap;
1480 ShenandoahHeapRegionClosure* const _blk;
1481
1482 shenandoah_padding(0);
1483 volatile size_t _index;
1484 shenandoah_padding(1);
1485
1486 public:
1487 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1488 WorkerTask("Shenandoah Parallel Region Operation"),
1489 _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1490
1491 void work(uint worker_id) {
1492 ShenandoahParallelWorkerSession worker_session(worker_id);
1493 size_t stride = ShenandoahParallelRegionStride;
1494
1495 size_t max = _heap->num_regions();
1496 while (Atomic::load(&_index) < max) {
1497 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1498 size_t start = cur;
1499 size_t end = MIN2(cur + stride, max);
1500 if (start >= max) break;
1501
1502 for (size_t i = cur; i < end; i++) {
1503 ShenandoahHeapRegion* current = _heap->get_region(i);
1504 _blk->heap_region_do(current);
1505 }
1506 }
1507 }
1508 };
1509
1510 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1511 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1512 if (num_regions() > ShenandoahParallelRegionStride) {
1513 ShenandoahParallelHeapRegionTask task(blk);
1514 workers()->run_task(&task);
1515 } else {
1516 heap_region_iterate(blk);
1517 }
1518 }
1519
1520 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1521 private:
1522 ShenandoahMarkingContext* const _ctx;
1523 public:
1524 ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1525
1526 void heap_region_do(ShenandoahHeapRegion* r) {
1527 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1528 if (r->is_active()) {
1529 // Check if region needs updating its TAMS. We have updated it already during concurrent
1530 // reset, so it is very likely we don't need to do another write here.
1531 if (_ctx->top_at_mark_start(r) != r->top()) {
1532 _ctx->capture_top_at_mark_start(r);
1533 }
1534 } else {
1535 assert(_ctx->top_at_mark_start(r) == r->top(),
1536 "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
1537 }
1538 }
1539
1540 bool is_thread_safe() { return true; }
1541 };
1542
1543 class ShenandoahRendezvousClosure : public HandshakeClosure {
1544 public:
1545 inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
1546 inline void do_thread(Thread* thread) {}
1547 };
1548
1549 void ShenandoahHeap::rendezvous_threads() {
1550 ShenandoahRendezvousClosure cl;
1551 Handshake::execute(&cl);
1552 }
1553
1554 void ShenandoahHeap::recycle_trash() {
1555 free_set()->recycle_trash();
1556 }
1557
1558 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1559 private:
1560 ShenandoahMarkingContext* const _ctx;
1561 public:
1562 ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1563
1564 void heap_region_do(ShenandoahHeapRegion* r) {
1565 if (r->is_active()) {
1566 // Reset live data and set TAMS optimistically. We would recheck these under the pause
1567 // anyway to capture any updates that happened since now.
1568 r->clear_live_data();
1569 _ctx->capture_top_at_mark_start(r);
1570 }
1571 }
1572
1573 bool is_thread_safe() { return true; }
1574 };
1575
1576 void ShenandoahHeap::prepare_gc() {
1577 reset_mark_bitmap();
1578
1579 ShenandoahResetUpdateRegionStateClosure cl;
1580 parallel_heap_region_iterate(&cl);
1581 }
1582
1583 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1584 private:
1585 ShenandoahMarkingContext* const _ctx;
1586 ShenandoahHeapLock* const _lock;
1587
1588 public:
1589 ShenandoahFinalMarkUpdateRegionStateClosure() :
1590 _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1591
1592 void heap_region_do(ShenandoahHeapRegion* r) {
1593 if (r->is_active()) {
1594 // All allocations past TAMS are implicitly live, adjust the region data.
1595 // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1596 HeapWord *tams = _ctx->top_at_mark_start(r);
1597 HeapWord *top = r->top();
1598 if (top > tams) {
1599 r->increase_live_data_alloc_words(pointer_delta(top, tams));
1600 }
1601
1602 // We are about to select the collection set, make sure it knows about
1603 // current pinning status. Also, this allows trashing more regions that
1604 // now have their pinning status dropped.
1605 if (r->is_pinned()) {
1606 if (r->pin_count() == 0) {
1607 ShenandoahHeapLocker locker(_lock);
1608 r->make_unpinned();
1609 }
1610 } else {
1611 if (r->pin_count() > 0) {
1612 ShenandoahHeapLocker locker(_lock);
1613 r->make_pinned();
1614 }
1615 }
1616
1617 // Remember limit for updating refs. It's guaranteed that we get no
1618 // from-space-refs written from here on.
1619 r->set_update_watermark_at_safepoint(r->top());
1620 } else {
1621 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1622 assert(_ctx->top_at_mark_start(r) == r->top(),
1623 "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1624 }
1625 }
1626
1627 bool is_thread_safe() { return true; }
1628 };
1629
1630 void ShenandoahHeap::prepare_regions_and_collection_set(bool concurrent) {
1631 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
1632 {
1633 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states :
1634 ShenandoahPhaseTimings::degen_gc_final_update_region_states);
1635 ShenandoahFinalMarkUpdateRegionStateClosure cl;
1636 parallel_heap_region_iterate(&cl);
1637
1638 assert_pinned_region_status();
1639 }
1640
1641 {
1642 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset :
1643 ShenandoahPhaseTimings::degen_gc_choose_cset);
1644 ShenandoahHeapLocker locker(lock());
1645 _collection_set->clear();
1646 heuristics()->choose_collection_set(_collection_set);
1647 }
1648
1649 {
1650 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset :
1651 ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
1652 ShenandoahHeapLocker locker(lock());
1653 _free_set->rebuild();
1654 }
1655 }
1656
1657 void ShenandoahHeap::do_class_unloading() {
1658 _unloader.unload();
1659 }
1660
1661 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1662 // Weak refs processing
1663 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1664 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1665 ShenandoahTimingsTracker t(phase);
1666 ShenandoahGCWorkerPhase worker_phase(phase);
1667 ref_processor()->process_references(phase, workers(), false /* concurrent */);
1668 }
1669
1670 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1671 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1672
1673 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1674 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1675 // for future GCLABs here.
1676 if (UseTLAB) {
1677 ShenandoahGCPhase phase(concurrent ?
1678 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1679 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1680 gclabs_retire(ResizeTLAB);
1681 }
1682
1683 _update_refs_iterator.reset();
1684 }
1685
1686 void ShenandoahHeap::propagate_gc_state_to_java_threads() {
1687 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1688 if (_gc_state_changed) {
1689 _gc_state_changed = false;
1690 char state = gc_state();
1691 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1692 ShenandoahThreadLocalData::set_gc_state(t, state);
1693 }
1694 }
1695 }
1696
1697 void ShenandoahHeap::set_gc_state(uint mask, bool value) {
1698 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1699 _gc_state.set_cond(mask, value);
1700 _gc_state_changed = true;
1701 }
1702
1703 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1704 assert(!has_forwarded_objects(), "Not expected before/after mark phase");
1705 set_gc_state(MARKING, in_progress);
1706 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1707 }
1708
1709 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1710 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1711 set_gc_state(EVACUATION, in_progress);
1712 }
1713
1714 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
1715 if (in_progress) {
1716 _concurrent_strong_root_in_progress.set();
1717 } else {
1718 _concurrent_strong_root_in_progress.unset();
1719 }
1720 }
1721
1722 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
1723 set_gc_state(WEAK_ROOTS, cond);
1724 }
1725
1726 GCTracer* ShenandoahHeap::tracer() {
1727 return shenandoah_policy()->tracer();
1728 }
1729
1730 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1731 return _free_set->used();
1732 }
1733
1734 bool ShenandoahHeap::try_cancel_gc() {
1735 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1736 return prev == CANCELLABLE;
1737 }
1738
1739 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1740 if (try_cancel_gc()) {
1741 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1742 log_info(gc)("%s", msg.buffer());
1743 Events::log(Thread::current(), "%s", msg.buffer());
1744 }
1745 }
1746
1747 uint ShenandoahHeap::max_workers() {
1748 return _max_workers;
1749 }
1750
1751 void ShenandoahHeap::stop() {
1752 // The shutdown sequence should be able to terminate when GC is running.
1753
1754 // Step 0. Notify policy to disable event recording.
1755 _shenandoah_policy->record_shutdown();
1756
1757 // Step 1. Notify control thread that we are in shutdown.
1758 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1759 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1760 control_thread()->prepare_for_graceful_shutdown();
1761
1762 // Step 2. Notify GC workers that we are cancelling GC.
1763 cancel_gc(GCCause::_shenandoah_stop_vm);
1764
1765 // Step 3. Wait until GC worker exits normally.
1766 control_thread()->stop();
1767 }
1768
1769 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1770 if (!unload_classes()) return;
1771 ClassUnloadingContext ctx(_workers->active_workers(),
1772 true /* unregister_nmethods_during_purge */,
1773 false /* lock_codeblob_free_separately */);
1774
1775 // Unload classes and purge SystemDictionary.
1776 {
1777 ShenandoahPhaseTimings::Phase phase = full_gc ?
1778 ShenandoahPhaseTimings::full_gc_purge_class_unload :
1779 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
1780 ShenandoahIsAliveSelector is_alive;
1781 {
1782 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
1783 ShenandoahGCPhase gc_phase(phase);
1784 ShenandoahGCWorkerPhase worker_phase(phase);
1785 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
1786
1787 uint num_workers = _workers->active_workers();
1788 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
1789 _workers->run_task(&unlink_task);
1790 }
1791 // Release unloaded nmethods's memory.
1792 ClassUnloadingContext::context()->purge_and_free_nmethods();
1793 }
1794
1795 {
1796 ShenandoahGCPhase phase(full_gc ?
1797 ShenandoahPhaseTimings::full_gc_purge_cldg :
1798 ShenandoahPhaseTimings::degen_gc_purge_cldg);
1799 ClassLoaderDataGraph::purge(true /* at_safepoint */);
1800 }
1801 // Resize and verify metaspace
1802 MetaspaceGC::compute_new_size();
1803 DEBUG_ONLY(MetaspaceUtils::verify();)
1804 }
1805
1806 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
1807 // so they should not have forwarded oops.
1808 // However, we do need to "null" dead oops in the roots, if can not be done
1809 // in concurrent cycles.
1810 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
1811 uint num_workers = _workers->active_workers();
1812 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
1813 ShenandoahPhaseTimings::full_gc_purge_weak_par :
1814 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
1815 ShenandoahGCPhase phase(timing_phase);
1816 ShenandoahGCWorkerPhase worker_phase(timing_phase);
1817 // Cleanup weak roots
1818 if (has_forwarded_objects()) {
1819 ShenandoahForwardedIsAliveClosure is_alive;
1820 ShenandoahUpdateRefsClosure keep_alive;
1821 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
1822 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
1823 _workers->run_task(&cleaning_task);
1824 } else {
1825 ShenandoahIsAliveClosure is_alive;
1826 #ifdef ASSERT
1827 ShenandoahAssertNotForwardedClosure verify_cl;
1828 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
1829 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
1830 #else
1831 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
1832 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
1833 #endif
1834 _workers->run_task(&cleaning_task);
1835 }
1836 }
1837
1838 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
1839 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1840 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
1841 ShenandoahGCPhase phase(full_gc ?
1842 ShenandoahPhaseTimings::full_gc_purge :
1843 ShenandoahPhaseTimings::degen_gc_purge);
1844 stw_weak_refs(full_gc);
1845 stw_process_weak_roots(full_gc);
1846 stw_unload_classes(full_gc);
1847 }
1848
1849 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
1850 set_gc_state(HAS_FORWARDED, cond);
1851 }
1852
1853 void ShenandoahHeap::set_unload_classes(bool uc) {
1854 _unload_classes.set_cond(uc);
1855 }
1856
1857 bool ShenandoahHeap::unload_classes() const {
1858 return _unload_classes.is_set();
1859 }
1860
1861 address ShenandoahHeap::in_cset_fast_test_addr() {
1862 ShenandoahHeap* heap = ShenandoahHeap::heap();
1863 assert(heap->collection_set() != nullptr, "Sanity");
1864 return (address) heap->collection_set()->biased_map_address();
1865 }
1866
1867 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
1868 return Atomic::load(&_bytes_allocated_since_gc_start);
1869 }
1870
1871 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
1872 Atomic::store(&_bytes_allocated_since_gc_start, (size_t)0);
1873 }
1874
1875 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
1876 _degenerated_gc_in_progress.set_cond(in_progress);
1877 }
1878
1879 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
1880 _full_gc_in_progress.set_cond(in_progress);
1881 }
1882
1883 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
1884 assert (is_full_gc_in_progress(), "should be");
1885 _full_gc_move_in_progress.set_cond(in_progress);
1886 }
1887
1888 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
1889 set_gc_state(UPDATEREFS, in_progress);
1890 }
1891
1892 void ShenandoahHeap::register_nmethod(nmethod* nm) {
1893 ShenandoahCodeRoots::register_nmethod(nm);
1894 }
1895
1896 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
1897 ShenandoahCodeRoots::unregister_nmethod(nm);
1898 }
1899
1900 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
1901 heap_region_containing(o)->record_pin();
1902 }
1903
1904 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
1905 ShenandoahHeapRegion* r = heap_region_containing(o);
1906 assert(r != nullptr, "Sanity");
1907 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
1908 r->record_unpin();
1909 }
1910
1911 void ShenandoahHeap::sync_pinned_region_status() {
1912 ShenandoahHeapLocker locker(lock());
1913
1914 for (size_t i = 0; i < num_regions(); i++) {
1915 ShenandoahHeapRegion *r = get_region(i);
1916 if (r->is_active()) {
1917 if (r->is_pinned()) {
1918 if (r->pin_count() == 0) {
1919 r->make_unpinned();
1920 }
1921 } else {
1922 if (r->pin_count() > 0) {
1923 r->make_pinned();
1924 }
1925 }
1926 }
1927 }
1928
1929 assert_pinned_region_status();
1930 }
1931
1932 #ifdef ASSERT
1933 void ShenandoahHeap::assert_pinned_region_status() {
1934 for (size_t i = 0; i < num_regions(); i++) {
1935 ShenandoahHeapRegion* r = get_region(i);
1936 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
1937 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
1938 }
1939 }
1940 #endif
1941
1942 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
1943 return _gc_timer;
1944 }
1945
1946 void ShenandoahHeap::prepare_concurrent_roots() {
1947 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1948 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1949 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
1950 set_concurrent_weak_root_in_progress(true);
1951 if (unload_classes()) {
1952 _unloader.prepare();
1953 }
1954 }
1955
1956 void ShenandoahHeap::finish_concurrent_roots() {
1957 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1958 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1959 if (unload_classes()) {
1960 _unloader.finish();
1961 }
1962 }
1963
1964 #ifdef ASSERT
1965 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
1966 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
1967
1968 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1969 if (UseDynamicNumberOfGCThreads) {
1970 assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
1971 } else {
1972 // Use ParallelGCThreads inside safepoints
1973 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
1974 }
1975 } else {
1976 if (UseDynamicNumberOfGCThreads) {
1977 assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
1978 } else {
1979 // Use ConcGCThreads outside safepoints
1980 assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
1981 }
1982 }
1983 }
1984 #endif
1985
1986 ShenandoahVerifier* ShenandoahHeap::verifier() {
1987 guarantee(ShenandoahVerify, "Should be enabled");
1988 assert (_verifier != nullptr, "sanity");
1989 return _verifier;
1990 }
1991
1992 template<bool CONCURRENT>
1993 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
1994 private:
1995 ShenandoahHeap* _heap;
1996 ShenandoahRegionIterator* _regions;
1997 public:
1998 ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
1999 WorkerTask("Shenandoah Update References"),
2000 _heap(ShenandoahHeap::heap()),
2001 _regions(regions) {
2002 }
2003
2004 void work(uint worker_id) {
2005 if (CONCURRENT) {
2006 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2007 ShenandoahSuspendibleThreadSetJoiner stsj;
2008 do_work<ShenandoahConcUpdateRefsClosure>();
2009 } else {
2010 ShenandoahParallelWorkerSession worker_session(worker_id);
2011 do_work<ShenandoahSTWUpdateRefsClosure>();
2012 }
2013 }
2014
2015 private:
2016 template<class T>
2017 void do_work() {
2018 T cl;
2019 ShenandoahHeapRegion* r = _regions->next();
2020 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2021 while (r != nullptr) {
2022 HeapWord* update_watermark = r->get_update_watermark();
2023 assert (update_watermark >= r->bottom(), "sanity");
2024 if (r->is_active() && !r->is_cset()) {
2025 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2026 }
2027 if (ShenandoahPacing) {
2028 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2029 }
2030 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2031 return;
2032 }
2033 r = _regions->next();
2034 }
2035 }
2036 };
2037
2038 void ShenandoahHeap::update_heap_references(bool concurrent) {
2039 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2040
2041 if (concurrent) {
2042 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2043 workers()->run_task(&task);
2044 } else {
2045 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2046 workers()->run_task(&task);
2047 }
2048 }
2049
2050
2051 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2052 private:
2053 ShenandoahHeapLock* const _lock;
2054
2055 public:
2056 ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2057
2058 void heap_region_do(ShenandoahHeapRegion* r) {
2059 // Drop unnecessary "pinned" state from regions that does not have CP marks
2060 // anymore, as this would allow trashing them.
2061
2062 if (r->is_active()) {
2063 if (r->is_pinned()) {
2064 if (r->pin_count() == 0) {
2065 ShenandoahHeapLocker locker(_lock);
2066 r->make_unpinned();
2067 }
2068 } else {
2069 if (r->pin_count() > 0) {
2070 ShenandoahHeapLocker locker(_lock);
2071 r->make_pinned();
2072 }
2073 }
2074 }
2075 }
2076
2077 bool is_thread_safe() { return true; }
2078 };
2079
2080 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2081 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2082 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2083
2084 {
2085 ShenandoahGCPhase phase(concurrent ?
2086 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2087 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2088 ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2089 parallel_heap_region_iterate(&cl);
2090
2091 assert_pinned_region_status();
2092 }
2093
2094 {
2095 ShenandoahGCPhase phase(concurrent ?
2096 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2097 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2098 trash_cset_regions();
2099 }
2100 }
2101
2102 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2103 {
2104 ShenandoahGCPhase phase(concurrent ?
2105 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2106 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2107 ShenandoahHeapLocker locker(lock());
2108 _free_set->rebuild();
2109 }
2110 }
2111
2112 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2113 print_on(st);
2114 st->cr();
2115 print_heap_regions_on(st);
2116 }
2117
2118 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2119 size_t slice = r->index() / _bitmap_regions_per_slice;
2120
2121 size_t regions_from = _bitmap_regions_per_slice * slice;
2122 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2123 for (size_t g = regions_from; g < regions_to; g++) {
2124 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2125 if (skip_self && g == r->index()) continue;
2126 if (get_region(g)->is_committed()) {
2127 return true;
2128 }
2129 }
2130 return false;
2131 }
2132
2133 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2134 shenandoah_assert_heaplocked();
2135
2136 // Bitmaps in special regions do not need commits
2137 if (_bitmap_region_special) {
2138 return true;
2139 }
2140
2141 if (is_bitmap_slice_committed(r, true)) {
2142 // Some other region from the group is already committed, meaning the bitmap
2143 // slice is already committed, we exit right away.
2144 return true;
2145 }
2146
2147 // Commit the bitmap slice:
2148 size_t slice = r->index() / _bitmap_regions_per_slice;
2149 size_t off = _bitmap_bytes_per_slice * slice;
2150 size_t len = _bitmap_bytes_per_slice;
2151 char* start = (char*) _bitmap_region.start() + off;
2152
2153 if (!os::commit_memory(start, len, false)) {
2154 return false;
2155 }
2156
2157 if (AlwaysPreTouch) {
2158 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2159 }
2160
2161 return true;
2162 }
2163
2164 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2165 shenandoah_assert_heaplocked();
2166
2167 // Bitmaps in special regions do not need uncommits
2168 if (_bitmap_region_special) {
2169 return true;
2170 }
2171
2172 if (is_bitmap_slice_committed(r, true)) {
2173 // Some other region from the group is still committed, meaning the bitmap
2174 // slice is should stay committed, exit right away.
2175 return true;
2176 }
2177
2178 // Uncommit the bitmap slice:
2179 size_t slice = r->index() / _bitmap_regions_per_slice;
2180 size_t off = _bitmap_bytes_per_slice * slice;
2181 size_t len = _bitmap_bytes_per_slice;
2182 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2183 return false;
2184 }
2185 return true;
2186 }
2187
2188 void ShenandoahHeap::safepoint_synchronize_begin() {
2189 SuspendibleThreadSet::synchronize();
2190 }
2191
2192 void ShenandoahHeap::safepoint_synchronize_end() {
2193 SuspendibleThreadSet::desynchronize();
2194 }
2195
2196 void ShenandoahHeap::entry_uncommit(double shrink_before, size_t shrink_until) {
2197 static const char *msg = "Concurrent uncommit";
2198 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
2199 EventMark em("%s", msg);
2200
2201 op_uncommit(shrink_before, shrink_until);
2202 }
2203
2204 void ShenandoahHeap::try_inject_alloc_failure() {
2205 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2206 _inject_alloc_failure.set();
2207 os::naked_short_sleep(1);
2208 if (cancelled_gc()) {
2209 log_info(gc)("Allocation failure was successfully injected");
2210 }
2211 }
2212 }
2213
2214 bool ShenandoahHeap::should_inject_alloc_failure() {
2215 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2216 }
2217
2218 void ShenandoahHeap::initialize_serviceability() {
2219 _memory_pool = new ShenandoahMemoryPool(this);
2220 _cycle_memory_manager.add_pool(_memory_pool);
2221 _stw_memory_manager.add_pool(_memory_pool);
2222 }
2223
2224 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2225 GrowableArray<GCMemoryManager*> memory_managers(2);
2226 memory_managers.append(&_cycle_memory_manager);
2227 memory_managers.append(&_stw_memory_manager);
2228 return memory_managers;
2229 }
2230
2231 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2232 GrowableArray<MemoryPool*> memory_pools(1);
2233 memory_pools.append(_memory_pool);
2234 return memory_pools;
2235 }
2236
2237 MemoryUsage ShenandoahHeap::memory_usage() {
2238 return _memory_pool->get_memory_usage();
2239 }
2240
2241 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2242 _heap(ShenandoahHeap::heap()),
2243 _index(0) {}
2244
2245 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2246 _heap(heap),
2247 _index(0) {}
2248
2249 void ShenandoahRegionIterator::reset() {
2250 _index = 0;
2251 }
2252
2253 bool ShenandoahRegionIterator::has_next() const {
2254 return _index < _heap->num_regions();
2255 }
2256
2257 char ShenandoahHeap::gc_state() const {
2258 return _gc_state.raw_value();
2259 }
2260
2261 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2262 #ifdef ASSERT
2263 assert(_liveness_cache != nullptr, "sanity");
2264 assert(worker_id < _max_workers, "sanity");
2265 for (uint i = 0; i < num_regions(); i++) {
2266 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2267 }
2268 #endif
2269 return _liveness_cache[worker_id];
2270 }
2271
2272 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2273 assert(worker_id < _max_workers, "sanity");
2274 assert(_liveness_cache != nullptr, "sanity");
2275 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2276 for (uint i = 0; i < num_regions(); i++) {
2277 ShenandoahLiveData live = ld[i];
2278 if (live > 0) {
2279 ShenandoahHeapRegion* r = get_region(i);
2280 r->increase_live_data_gc_words(live);
2281 ld[i] = 0;
2282 }
2283 }
2284 }
2285
2286 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2287 if (is_idle()) return false;
2288
2289 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2290 // marking phase.
2291 if (is_concurrent_mark_in_progress() &&
2292 !marking_context()->allocated_after_mark_start(obj)) {
2293 return true;
2294 }
2295
2296 // Can not guarantee obj is deeply good.
2297 if (has_forwarded_objects()) {
2298 return true;
2299 }
2300
2301 return false;
2302 }