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