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/slidingForwarding.hpp"
38 #include "gc/shared/tlab_globals.hpp"
39
40 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
41 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
42 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
43 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
44 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
45 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
46 #include "gc/shenandoah/shenandoahControlThread.hpp"
47 #include "gc/shenandoah/shenandoahFreeSet.hpp"
48 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
49 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
50 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
51 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
52 #include "gc/shenandoah/shenandoahInitLogger.hpp"
53 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
54 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
55 #include "gc/shenandoah/shenandoahMetrics.hpp"
56 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
57 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
58 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
59 #include "gc/shenandoah/shenandoahPadding.hpp"
60 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
61 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
62 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
63 #include "gc/shenandoah/shenandoahSTWMark.hpp"
64 #include "gc/shenandoah/shenandoahUtils.hpp"
65 #include "gc/shenandoah/shenandoahVerifier.hpp"
66 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
67 #include "gc/shenandoah/shenandoahVMOperations.hpp"
68 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
69 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
70 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
71 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
72 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
73 #if INCLUDE_JFR
74 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
75 #endif
76
77 #include "classfile/systemDictionary.hpp"
78 #include "code/codeCache.hpp"
79 #include "memory/classLoaderMetaspace.hpp"
80 #include "memory/metaspaceUtils.hpp"
81 #include "oops/compressedOops.inline.hpp"
82 #include "prims/jvmtiTagMap.hpp"
83 #include "runtime/atomic.hpp"
84 #include "runtime/globals.hpp"
85 #include "runtime/interfaceSupport.inline.hpp"
86 #include "runtime/java.hpp"
87 #include "runtime/orderAccess.hpp"
88 #include "runtime/safepointMechanism.hpp"
89 #include "runtime/vmThread.hpp"
90 #include "services/mallocTracker.hpp"
91 #include "services/memTracker.hpp"
92 #include "utilities/events.hpp"
93 #include "utilities/powerOfTwo.hpp"
94
95 class ShenandoahPretouchHeapTask : public WorkerTask {
96 private:
97 ShenandoahRegionIterator _regions;
98 const size_t _page_size;
99 public:
100 ShenandoahPretouchHeapTask(size_t page_size) :
101 WorkerTask("Shenandoah Pretouch Heap"),
102 _page_size(page_size) {}
103
104 virtual void work(uint worker_id) {
105 ShenandoahHeapRegion* r = _regions.next();
106 while (r != nullptr) {
107 if (r->is_committed()) {
108 os::pretouch_memory(r->bottom(), r->end(), _page_size);
109 }
110 r = _regions.next();
111 }
112 }
113 };
114
115 class ShenandoahPretouchBitmapTask : public WorkerTask {
116 private:
117 ShenandoahRegionIterator _regions;
118 char* _bitmap_base;
119 const size_t _bitmap_size;
120 const size_t _page_size;
121 public:
122 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
123 WorkerTask("Shenandoah Pretouch Bitmap"),
124 _bitmap_base(bitmap_base),
125 _bitmap_size(bitmap_size),
126 _page_size(page_size) {}
127
128 virtual void work(uint worker_id) {
129 ShenandoahHeapRegion* r = _regions.next();
130 while (r != nullptr) {
131 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
132 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
133 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
134
135 if (r->is_committed()) {
136 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
137 }
138
139 r = _regions.next();
140 }
141 }
142 };
143
144 jint ShenandoahHeap::initialize() {
145 //
146 // Figure out heap sizing
147 //
148
149 size_t init_byte_size = InitialHeapSize;
150 size_t min_byte_size = MinHeapSize;
151 size_t max_byte_size = MaxHeapSize;
152 size_t heap_alignment = HeapAlignment;
153
154 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
155
156 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
157 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
158
159 _num_regions = ShenandoahHeapRegion::region_count();
160 assert(_num_regions == (max_byte_size / reg_size_bytes),
161 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
162 _num_regions, max_byte_size, reg_size_bytes);
163
164 // Now we know the number of regions, initialize the heuristics.
165 initialize_heuristics();
166
167 size_t num_committed_regions = init_byte_size / reg_size_bytes;
168 num_committed_regions = MIN2(num_committed_regions, _num_regions);
169 assert(num_committed_regions <= _num_regions, "sanity");
170 _initial_size = num_committed_regions * reg_size_bytes;
171
172 size_t num_min_regions = min_byte_size / reg_size_bytes;
173 num_min_regions = MIN2(num_min_regions, _num_regions);
174 assert(num_min_regions <= _num_regions, "sanity");
175 _minimum_size = num_min_regions * reg_size_bytes;
176
177 // Default to max heap size.
178 _soft_max_size = _num_regions * reg_size_bytes;
179
180 _committed = _initial_size;
181
182 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
183 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
184 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
185
186 //
187 // Reserve and commit memory for heap
188 //
189
190 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
191 initialize_reserved_region(heap_rs);
192 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
193 _heap_region_special = heap_rs.special();
194
195 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
196 "Misaligned heap: " PTR_FORMAT, p2i(base()));
197
198 #if SHENANDOAH_OPTIMIZED_MARKTASK
199 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
200 // Fail if we ever attempt to address more than we can.
201 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
202 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
203 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
204 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
205 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
206 vm_exit_during_initialization("Fatal Error", buf);
207 }
208 #endif
209
210 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
211 if (!_heap_region_special) {
212 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
213 "Cannot commit heap memory");
214 }
215
216 //
217 // Reserve and commit memory for bitmap(s)
218 //
219
220 _bitmap_size = ShenandoahMarkBitMap::compute_size(heap_rs.size());
221 _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
222
223 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
224
225 guarantee(bitmap_bytes_per_region != 0,
226 "Bitmap bytes per region should not be zero");
227 guarantee(is_power_of_2(bitmap_bytes_per_region),
228 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
229
230 if (bitmap_page_size > bitmap_bytes_per_region) {
231 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
232 _bitmap_bytes_per_slice = bitmap_page_size;
233 } else {
234 _bitmap_regions_per_slice = 1;
235 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
236 }
237
238 guarantee(_bitmap_regions_per_slice >= 1,
239 "Should have at least one region per slice: " SIZE_FORMAT,
240 _bitmap_regions_per_slice);
241
242 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
243 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
244 _bitmap_bytes_per_slice, bitmap_page_size);
245
246 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
247 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
248 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
249 _bitmap_region_special = bitmap.special();
250
251 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
252 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
253 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
254 if (!_bitmap_region_special) {
255 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
256 "Cannot commit bitmap memory");
257 }
258
259 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions, _max_workers);
260
261 if (ShenandoahVerify) {
262 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
263 if (!verify_bitmap.special()) {
264 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
265 "Cannot commit verification bitmap memory");
266 }
267 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
268 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
269 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
270 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
271 }
272
273 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
274 ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
275 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
276 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
277 _aux_bitmap_region_special = aux_bitmap.special();
278 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
279
280 //
281 // Create regions and region sets
282 //
283 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
284 size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
285 region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
286
287 ReservedSpace region_storage(region_storage_size, region_page_size);
288 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
289 if (!region_storage.special()) {
290 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
291 "Cannot commit region memory");
292 }
293
294 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
295 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
296 // If not successful, bite a bullet and allocate at whatever address.
297 {
298 size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
299 size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
300
301 uintptr_t min = round_up_power_of_2(cset_align);
302 uintptr_t max = (1u << 30u);
303
304 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
305 char* req_addr = (char*)addr;
306 assert(is_aligned(req_addr, cset_align), "Should be aligned");
307 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size(), req_addr);
308 if (cset_rs.is_reserved()) {
309 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
310 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
311 break;
312 }
313 }
314
315 if (_collection_set == nullptr) {
316 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size());
317 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
318 }
319 }
320
321 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
322 _free_set = new ShenandoahFreeSet(this, _num_regions);
323
324 {
325 ShenandoahHeapLocker locker(lock());
326
327 for (size_t i = 0; i < _num_regions; i++) {
328 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
329 bool is_committed = i < num_committed_regions;
330 void* loc = region_storage.base() + i * region_align;
331
332 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
333 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
334
335 _marking_context->initialize_top_at_mark_start(r);
336 _regions[i] = r;
337 assert(!collection_set()->is_in(i), "New region should not be in collection set");
338 }
339
340 // Initialize to complete
341 _marking_context->mark_complete();
342
343 _free_set->rebuild();
344 }
345
346 if (AlwaysPreTouch) {
347 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
348 // before initialize() below zeroes it with initializing thread. For any given region,
349 // we touch the region and the corresponding bitmaps from the same thread.
350 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
351
352 _pretouch_heap_page_size = heap_page_size;
353 _pretouch_bitmap_page_size = bitmap_page_size;
354
355 #ifdef LINUX
356 // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
357 // pages. But, the kernel needs to know that every small page is used, in order to coalesce
358 // them into huge one. Therefore, we need to pretouch with smaller pages.
359 if (UseTransparentHugePages) {
360 _pretouch_heap_page_size = (size_t)os::vm_page_size();
361 _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
362 }
363 #endif
364
365 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
366 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
367
368 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
369 _workers->run_task(&bcl);
370
371 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
372 _workers->run_task(&hcl);
373 }
374
375 //
376 // Initialize the rest of GC subsystems
377 //
378
379 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
380 for (uint worker = 0; worker < _max_workers; worker++) {
381 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
382 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
383 }
384
385 // There should probably be Shenandoah-specific options for these,
386 // just as there are G1-specific options.
387 {
388 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
389 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
390 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
391 }
392
393 _monitoring_support = new ShenandoahMonitoringSupport(this);
394 _phase_timings = new ShenandoahPhaseTimings(max_workers());
395 ShenandoahCodeRoots::initialize();
396
397 if (ShenandoahPacing) {
398 _pacer = new ShenandoahPacer(this);
399 _pacer->setup_for_idle();
400 } else {
401 _pacer = nullptr;
402 }
403
404 _control_thread = new ShenandoahControlThread();
405
406 ShenandoahInitLogger::print();
407
408 SlidingForwarding::initialize(_heap_region, ShenandoahHeapRegion::region_size_words());
409
410 return JNI_OK;
411 }
412
413 void ShenandoahHeap::initialize_mode() {
414 if (ShenandoahGCMode != nullptr) {
415 if (strcmp(ShenandoahGCMode, "satb") == 0) {
416 _gc_mode = new ShenandoahSATBMode();
417 } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
418 _gc_mode = new ShenandoahIUMode();
419 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
420 _gc_mode = new ShenandoahPassiveMode();
421 } else {
422 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
423 }
424 } else {
425 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
426 }
427 _gc_mode->initialize_flags();
428 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
429 vm_exit_during_initialization(
430 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
431 _gc_mode->name()));
432 }
433 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
434 vm_exit_during_initialization(
435 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
436 _gc_mode->name()));
437 }
438 }
439
440 void ShenandoahHeap::initialize_heuristics() {
441 assert(_gc_mode != nullptr, "Must be initialized");
442 _heuristics = _gc_mode->initialize_heuristics();
443
444 if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
445 vm_exit_during_initialization(
446 err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
447 _heuristics->name()));
448 }
449 if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
450 vm_exit_during_initialization(
451 err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
452 _heuristics->name()));
453 }
454 }
455
456 #ifdef _MSC_VER
457 #pragma warning( push )
458 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
459 #endif
460
461 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
462 CollectedHeap(),
463 _initial_size(0),
464 _used(0),
465 _committed(0),
466 _bytes_allocated_since_gc_start(0),
467 _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
468 _workers(nullptr),
469 _safepoint_workers(nullptr),
470 _heap_region_special(false),
471 _num_regions(0),
472 _regions(nullptr),
473 _update_refs_iterator(this),
474 _gc_state_changed(false),
475 _control_thread(nullptr),
476 _shenandoah_policy(policy),
477 _gc_mode(nullptr),
478 _heuristics(nullptr),
479 _free_set(nullptr),
480 _pacer(nullptr),
481 _verifier(nullptr),
482 _phase_timings(nullptr),
483 _monitoring_support(nullptr),
484 _memory_pool(nullptr),
485 _stw_memory_manager("Shenandoah Pauses"),
486 _cycle_memory_manager("Shenandoah Cycles"),
487 _gc_timer(new ConcurrentGCTimer()),
488 _soft_ref_policy(),
489 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
490 _ref_processor(new ShenandoahReferenceProcessor(MAX2(_max_workers, 1U))),
491 _marking_context(nullptr),
492 _bitmap_size(0),
493 _bitmap_regions_per_slice(0),
494 _bitmap_bytes_per_slice(0),
495 _bitmap_region_special(false),
496 _aux_bitmap_region_special(false),
497 _liveness_cache(nullptr),
498 _collection_set(nullptr)
499 {
500 // Initialize GC mode early, so we can adjust barrier support
501 initialize_mode();
502 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
503
504 _max_workers = MAX2(_max_workers, 1U);
505 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
506 if (_workers == nullptr) {
507 vm_exit_during_initialization("Failed necessary allocation.");
508 } else {
509 _workers->initialize_workers();
510 }
511
512 if (ParallelGCThreads > 1) {
513 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread",
514 ParallelGCThreads);
515 _safepoint_workers->initialize_workers();
516 }
517 }
518
519 #ifdef _MSC_VER
520 #pragma warning( pop )
521 #endif
522
523 class ShenandoahResetBitmapTask : public WorkerTask {
524 private:
525 ShenandoahRegionIterator _regions;
526
527 public:
528 ShenandoahResetBitmapTask() :
529 WorkerTask("Shenandoah Reset Bitmap") {}
530
531 void work(uint worker_id) {
532 ShenandoahHeapRegion* region = _regions.next();
533 ShenandoahHeap* heap = ShenandoahHeap::heap();
534 ShenandoahMarkingContext* const ctx = heap->marking_context();
535 while (region != nullptr) {
536 if (heap->is_bitmap_slice_committed(region)) {
537 ctx->clear_bitmap(region);
538 }
539 region = _regions.next();
540 }
541 }
542 };
543
544 void ShenandoahHeap::reset_mark_bitmap() {
545 assert_gc_workers(_workers->active_workers());
546 mark_incomplete_marking_context();
547
548 ShenandoahResetBitmapTask task;
549 _workers->run_task(&task);
550 }
551
552 void ShenandoahHeap::print_on(outputStream* st) const {
553 st->print_cr("Shenandoah Heap");
554 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
555 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
556 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
557 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
558 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
559 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
560 num_regions(),
561 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
562 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
563
564 st->print("Status: ");
565 if (has_forwarded_objects()) st->print("has forwarded objects, ");
566 if (is_concurrent_mark_in_progress()) st->print("marking, ");
567 if (is_evacuation_in_progress()) st->print("evacuating, ");
568 if (is_update_refs_in_progress()) st->print("updating refs, ");
569 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
570 if (is_full_gc_in_progress()) st->print("full gc, ");
571 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
572 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
573 if (is_concurrent_strong_root_in_progress() &&
574 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
575
576 if (cancelled_gc()) {
577 st->print("cancelled");
578 } else {
579 st->print("not cancelled");
580 }
581 st->cr();
582
583 st->print_cr("Reserved region:");
584 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
585 p2i(reserved_region().start()),
586 p2i(reserved_region().end()));
587
588 ShenandoahCollectionSet* cset = collection_set();
589 st->print_cr("Collection set:");
590 if (cset != nullptr) {
591 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
592 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
593 } else {
594 st->print_cr(" (null)");
595 }
596
597 st->cr();
598 MetaspaceUtils::print_on(st);
599
600 if (Verbose) {
601 st->cr();
602 print_heap_regions_on(st);
603 }
604 }
605
606 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
607 public:
608 void do_thread(Thread* thread) {
609 assert(thread != nullptr, "Sanity");
610 assert(thread->is_Worker_thread(), "Only worker thread expected");
611 ShenandoahThreadLocalData::initialize_gclab(thread);
612 }
613 };
614
615 void ShenandoahHeap::post_initialize() {
616 CollectedHeap::post_initialize();
617 MutexLocker ml(Threads_lock);
618
619 ShenandoahInitWorkerGCLABClosure init_gclabs;
620 _workers->threads_do(&init_gclabs);
621
622 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
623 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
624 _workers->set_initialize_gclab();
625 if (_safepoint_workers != nullptr) {
626 _safepoint_workers->threads_do(&init_gclabs);
627 _safepoint_workers->set_initialize_gclab();
628 }
629
630 _heuristics->initialize();
631
632 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
633 }
634
635 size_t ShenandoahHeap::used() const {
636 return Atomic::load(&_used);
637 }
638
639 size_t ShenandoahHeap::committed() const {
640 return Atomic::load(&_committed);
641 }
642
643 void ShenandoahHeap::increase_committed(size_t bytes) {
644 shenandoah_assert_heaplocked_or_safepoint();
645 _committed += bytes;
646 }
647
648 void ShenandoahHeap::decrease_committed(size_t bytes) {
649 shenandoah_assert_heaplocked_or_safepoint();
650 _committed -= bytes;
651 }
652
653 void ShenandoahHeap::increase_used(size_t bytes) {
654 Atomic::add(&_used, bytes, memory_order_relaxed);
655 }
656
657 void ShenandoahHeap::set_used(size_t bytes) {
658 Atomic::store(&_used, bytes);
659 }
660
661 void ShenandoahHeap::decrease_used(size_t bytes) {
662 assert(used() >= bytes, "never decrease heap size by more than we've left");
663 Atomic::sub(&_used, bytes, memory_order_relaxed);
664 }
665
666 void ShenandoahHeap::increase_allocated(size_t bytes) {
667 Atomic::add(&_bytes_allocated_since_gc_start, bytes, memory_order_relaxed);
668 }
669
670 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
671 size_t bytes = words * HeapWordSize;
672 if (!waste) {
673 increase_used(bytes);
674 }
675 increase_allocated(bytes);
676 if (ShenandoahPacing) {
677 control_thread()->pacing_notify_alloc(words);
678 if (waste) {
679 pacer()->claim_for_alloc(words, true);
680 }
681 }
682 }
683
684 size_t ShenandoahHeap::capacity() const {
685 return committed();
686 }
687
688 size_t ShenandoahHeap::max_capacity() const {
689 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
690 }
691
692 size_t ShenandoahHeap::soft_max_capacity() const {
693 size_t v = Atomic::load(&_soft_max_size);
694 assert(min_capacity() <= v && v <= max_capacity(),
695 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
696 min_capacity(), v, max_capacity());
697 return v;
698 }
699
700 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
701 assert(min_capacity() <= v && v <= max_capacity(),
702 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
703 min_capacity(), v, max_capacity());
704 Atomic::store(&_soft_max_size, v);
705 }
706
707 size_t ShenandoahHeap::min_capacity() const {
708 return _minimum_size;
709 }
710
711 size_t ShenandoahHeap::initial_capacity() const {
712 return _initial_size;
713 }
714
715 bool ShenandoahHeap::is_in(const void* p) const {
716 HeapWord* heap_base = (HeapWord*) base();
717 HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
718 return p >= heap_base && p < last_region_end;
719 }
720
721 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
722 assert (ShenandoahUncommit, "should be enabled");
723
724 // Application allocates from the beginning of the heap, and GC allocates at
725 // the end of it. It is more efficient to uncommit from the end, so that applications
726 // could enjoy the near committed regions. GC allocations are much less frequent,
727 // and therefore can accept the committing costs.
728
729 size_t count = 0;
730 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
731 ShenandoahHeapRegion* r = get_region(i - 1);
732 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
733 ShenandoahHeapLocker locker(lock());
734 if (r->is_empty_committed()) {
735 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
736 break;
737 }
738
739 r->make_uncommitted();
740 count++;
741 }
742 }
743 SpinPause(); // allow allocators to take the lock
744 }
745
746 if (count > 0) {
747 control_thread()->notify_heap_changed();
748 }
749 }
750
751 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
752 // New object should fit the GCLAB size
753 size_t min_size = MAX2(size, PLAB::min_size());
754
755 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
756 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
757 new_size = MIN2(new_size, PLAB::max_size());
758 new_size = MAX2(new_size, PLAB::min_size());
759
760 // Record new heuristic value even if we take any shortcut. This captures
761 // the case when moderately-sized objects always take a shortcut. At some point,
762 // heuristics should catch up with them.
763 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
764
765 if (new_size < size) {
766 // New size still does not fit the object. Fall back to shared allocation.
767 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
768 return nullptr;
769 }
770
771 // Retire current GCLAB, and allocate a new one.
772 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
773 gclab->retire();
774
775 size_t actual_size = 0;
776 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
777 if (gclab_buf == nullptr) {
778 return nullptr;
779 }
780
781 assert (size <= actual_size, "allocation should fit");
782
783 // ...and clear or zap just allocated TLAB, if needed.
784 if (ZeroTLAB) {
785 Copy::zero_to_words(gclab_buf, actual_size);
786 } else if (ZapTLAB) {
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 }
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 // If we are dealing with mutator allocation, then we may need to block for safepoint.
889 // We cannot block for safepoint for GC allocations, because there is a high chance
890 // we are already running at safepoint or from stack watermark machinery, and we cannot
891 // block again.
892 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
893 return _free_set->allocate(req, in_new_region);
894 }
895
896 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
897 bool* gc_overhead_limit_was_exceeded) {
898 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
899 return allocate_memory(req);
900 }
901
902 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
903 size_t size,
904 Metaspace::MetadataType mdtype) {
905 MetaWord* result;
906
907 // Inform metaspace OOM to GC heuristics if class unloading is possible.
908 if (heuristics()->can_unload_classes()) {
909 ShenandoahHeuristics* h = heuristics();
910 h->record_metaspace_oom();
911 }
912
913 // Expand and retry allocation
914 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
915 if (result != nullptr) {
916 return result;
917 }
918
919 // Start full GC
920 collect(GCCause::_metadata_GC_clear_soft_refs);
921
922 // Retry allocation
923 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
924 if (result != nullptr) {
925 return result;
926 }
927
928 // Expand and retry allocation
929 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
930 if (result != nullptr) {
931 return result;
932 }
933
934 // Out of memory
935 return nullptr;
936 }
937
938 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
939 private:
940 ShenandoahHeap* const _heap;
941 Thread* const _thread;
942 public:
943 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
944 _heap(heap), _thread(Thread::current()) {}
945
946 void do_object(oop p) {
947 shenandoah_assert_marked(nullptr, p);
948 if (!p->is_forwarded()) {
949 _heap->evacuate_object(p, _thread);
950 }
951 }
952 };
953
954 class ShenandoahEvacuationTask : public WorkerTask {
955 private:
956 ShenandoahHeap* const _sh;
957 ShenandoahCollectionSet* const _cs;
958 bool _concurrent;
959 public:
960 ShenandoahEvacuationTask(ShenandoahHeap* sh,
961 ShenandoahCollectionSet* cs,
962 bool concurrent) :
963 WorkerTask("Shenandoah Evacuation"),
964 _sh(sh),
965 _cs(cs),
966 _concurrent(concurrent)
967 {}
968
969 void work(uint worker_id) {
970 if (_concurrent) {
971 ShenandoahConcurrentWorkerSession worker_session(worker_id);
972 ShenandoahSuspendibleThreadSetJoiner stsj;
973 ShenandoahEvacOOMScope oom_evac_scope;
974 do_work();
975 } else {
976 ShenandoahParallelWorkerSession worker_session(worker_id);
977 ShenandoahEvacOOMScope oom_evac_scope;
978 do_work();
979 }
980 }
981
982 private:
983 void do_work() {
984 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
985 ShenandoahHeapRegion* r;
986 while ((r =_cs->claim_next()) != nullptr) {
987 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
988 _sh->marked_object_iterate(r, &cl);
989
990 if (ShenandoahPacing) {
991 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
992 }
993
994 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
995 break;
996 }
997 }
998 }
999 };
1000
1001 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1002 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1003 workers()->run_task(&task);
1004 }
1005
1006 void ShenandoahHeap::trash_cset_regions() {
1007 ShenandoahHeapLocker locker(lock());
1008
1009 ShenandoahCollectionSet* set = collection_set();
1010 ShenandoahHeapRegion* r;
1011 set->clear_current_index();
1012 while ((r = set->next()) != nullptr) {
1013 r->make_trash();
1014 }
1015 collection_set()->clear();
1016 }
1017
1018 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1019 st->print_cr("Heap Regions:");
1020 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1021 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1022 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1023 st->print_cr("UWM=update watermark, U=used");
1024 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1025 st->print_cr("S=shared allocs, L=live data");
1026 st->print_cr("CP=critical pins");
1027
1028 for (size_t i = 0; i < num_regions(); i++) {
1029 get_region(i)->print_on(st);
1030 }
1031 }
1032
1033 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1034 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1035
1036 oop humongous_obj = cast_to_oop(start->bottom());
1037 size_t size = humongous_obj->size();
1038 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1039 size_t index = start->index() + required_regions - 1;
1040
1041 assert(!start->has_live(), "liveness must be zero");
1042
1043 for(size_t i = 0; i < required_regions; i++) {
1044 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1045 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1046 ShenandoahHeapRegion* region = get_region(index --);
1047
1048 assert(region->is_humongous(), "expect correct humongous start or continuation");
1049 assert(!region->is_cset(), "Humongous region should not be in collection set");
1050
1051 region->make_trash_immediate();
1052 }
1053 }
1054
1055 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1056 public:
1057 ShenandoahCheckCleanGCLABClosure() {}
1058 void do_thread(Thread* thread) {
1059 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1060 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1061 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1062 }
1063 };
1064
1065 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1066 private:
1067 bool const _resize;
1068 public:
1069 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1070 void do_thread(Thread* thread) {
1071 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1072 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1073 gclab->retire();
1074 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1075 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1076 }
1077 }
1078 };
1079
1080 void ShenandoahHeap::labs_make_parsable() {
1081 assert(UseTLAB, "Only call with UseTLAB");
1082
1083 ShenandoahRetireGCLABClosure cl(false);
1084
1085 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1086 ThreadLocalAllocBuffer& tlab = t->tlab();
1087 tlab.make_parsable();
1088 cl.do_thread(t);
1089 }
1090
1091 workers()->threads_do(&cl);
1092 }
1093
1094 void ShenandoahHeap::tlabs_retire(bool resize) {
1095 assert(UseTLAB, "Only call with UseTLAB");
1096 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1097
1098 ThreadLocalAllocStats stats;
1099
1100 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1101 ThreadLocalAllocBuffer& tlab = t->tlab();
1102 tlab.retire(&stats);
1103 if (resize) {
1104 tlab.resize();
1105 }
1106 }
1107
1108 stats.publish();
1109
1110 #ifdef ASSERT
1111 ShenandoahCheckCleanGCLABClosure cl;
1112 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1113 cl.do_thread(t);
1114 }
1115 workers()->threads_do(&cl);
1116 #endif
1117 }
1118
1119 void ShenandoahHeap::gclabs_retire(bool resize) {
1120 assert(UseTLAB, "Only call with UseTLAB");
1121 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1122
1123 ShenandoahRetireGCLABClosure cl(resize);
1124 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1125 cl.do_thread(t);
1126 }
1127 workers()->threads_do(&cl);
1128
1129 if (safepoint_workers() != nullptr) {
1130 safepoint_workers()->threads_do(&cl);
1131 }
1132 }
1133
1134 // Returns size in bytes
1135 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1136 // Return the max allowed size, and let the allocation path
1137 // figure out the safe size for current allocation.
1138 return ShenandoahHeapRegion::max_tlab_size_bytes();
1139 }
1140
1141 size_t ShenandoahHeap::max_tlab_size() const {
1142 // Returns size in words
1143 return ShenandoahHeapRegion::max_tlab_size_words();
1144 }
1145
1146 void ShenandoahHeap::collect(GCCause::Cause cause) {
1147 control_thread()->request_gc(cause);
1148 }
1149
1150 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1151 //assert(false, "Shouldn't need to do full collections");
1152 }
1153
1154 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1155 ShenandoahHeapRegion* r = heap_region_containing(addr);
1156 if (r != nullptr) {
1157 return r->block_start(addr);
1158 }
1159 return nullptr;
1160 }
1161
1162 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1163 ShenandoahHeapRegion* r = heap_region_containing(addr);
1164 return r->block_is_obj(addr);
1165 }
1166
1167 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1168 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1169 }
1170
1171 void ShenandoahHeap::prepare_for_verify() {
1172 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1173 labs_make_parsable();
1174 }
1175 }
1176
1177 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1178 tcl->do_thread(_control_thread);
1179 workers()->threads_do(tcl);
1180 if (_safepoint_workers != nullptr) {
1181 _safepoint_workers->threads_do(tcl);
1182 }
1183 }
1184
1185 void ShenandoahHeap::print_tracing_info() const {
1186 LogTarget(Info, gc, stats) lt;
1187 if (lt.is_enabled()) {
1188 ResourceMark rm;
1189 LogStream ls(lt);
1190
1191 phase_timings()->print_global_on(&ls);
1192
1193 ls.cr();
1194 ls.cr();
1195
1196 shenandoah_policy()->print_gc_stats(&ls);
1197
1198 ls.cr();
1199 ls.cr();
1200 }
1201 }
1202
1203 void ShenandoahHeap::verify(VerifyOption vo) {
1204 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1205 if (ShenandoahVerify) {
1206 verifier()->verify_generic(vo);
1207 } else {
1208 // TODO: Consider allocating verification bitmaps on demand,
1209 // and turn this on unconditionally.
1210 }
1211 }
1212 }
1213 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1214 return _free_set->capacity();
1215 }
1216
1217 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1218 private:
1219 MarkBitMap* _bitmap;
1220 ShenandoahScanObjectStack* _oop_stack;
1221 ShenandoahHeap* const _heap;
1222 ShenandoahMarkingContext* const _marking_context;
1223
1224 template <class T>
1225 void do_oop_work(T* p) {
1226 T o = RawAccess<>::oop_load(p);
1227 if (!CompressedOops::is_null(o)) {
1228 oop obj = CompressedOops::decode_not_null(o);
1229 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1230 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1231 return;
1232 }
1233 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1234
1235 assert(oopDesc::is_oop(obj), "must be a valid oop");
1236 if (!_bitmap->is_marked(obj)) {
1237 _bitmap->mark(obj);
1238 _oop_stack->push(obj);
1239 }
1240 }
1241 }
1242 public:
1243 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1244 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1245 _marking_context(_heap->marking_context()) {}
1246 void do_oop(oop* p) { do_oop_work(p); }
1247 void do_oop(narrowOop* p) { do_oop_work(p); }
1248 };
1249
1250 /*
1251 * This is public API, used in preparation of object_iterate().
1252 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1253 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1254 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1255 */
1256 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1257 // No-op.
1258 }
1259
1260 /*
1261 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1262 *
1263 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1264 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1265 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1266 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1267 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1268 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1269 * wiped the bitmap in preparation for next marking).
1270 *
1271 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1272 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1273 * is allowed to report dead objects, but is not required to do so.
1274 */
1275 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1276 // Reset bitmap
1277 if (!prepare_aux_bitmap_for_iteration())
1278 return;
1279
1280 ShenandoahScanObjectStack oop_stack;
1281 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1282 // Seed the stack with root scan
1283 scan_roots_for_iteration(&oop_stack, &oops);
1284
1285 // Work through the oop stack to traverse heap
1286 while (! oop_stack.is_empty()) {
1287 oop obj = oop_stack.pop();
1288 assert(oopDesc::is_oop(obj), "must be a valid oop");
1289 cl->do_object(obj);
1290 obj->oop_iterate(&oops);
1291 }
1292
1293 assert(oop_stack.is_empty(), "should be empty");
1294 // Reclaim bitmap
1295 reclaim_aux_bitmap_for_iteration();
1296 }
1297
1298 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1299 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1300
1301 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1302 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1303 return false;
1304 }
1305 // Reset bitmap
1306 _aux_bit_map.clear();
1307 return true;
1308 }
1309
1310 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1311 // Process GC roots according to current GC cycle
1312 // This populates the work stack with initial objects
1313 // It is important to relinquish the associated locks before diving
1314 // into heap dumper
1315 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1316 ShenandoahHeapIterationRootScanner rp(n_workers);
1317 rp.roots_do(oops);
1318 }
1319
1320 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1321 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1322 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1323 }
1324 }
1325
1326 // Closure for parallelly iterate objects
1327 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1328 private:
1329 MarkBitMap* _bitmap;
1330 ShenandoahObjToScanQueue* _queue;
1331 ShenandoahHeap* const _heap;
1332 ShenandoahMarkingContext* const _marking_context;
1333
1334 template <class T>
1335 void do_oop_work(T* p) {
1336 T o = RawAccess<>::oop_load(p);
1337 if (!CompressedOops::is_null(o)) {
1338 oop obj = CompressedOops::decode_not_null(o);
1339 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1340 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1341 return;
1342 }
1343 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1344
1345 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1346 if (_bitmap->par_mark(obj)) {
1347 _queue->push(ShenandoahMarkTask(obj));
1348 }
1349 }
1350 }
1351 public:
1352 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1353 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1354 _marking_context(_heap->marking_context()) {}
1355 void do_oop(oop* p) { do_oop_work(p); }
1356 void do_oop(narrowOop* p) { do_oop_work(p); }
1357 };
1358
1359 // Object iterator for parallel heap iteraion.
1360 // The root scanning phase happenes in construction as a preparation of
1361 // parallel marking queues.
1362 // Every worker processes it's own marking queue. work-stealing is used
1363 // to balance workload.
1364 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1365 private:
1366 uint _num_workers;
1367 bool _init_ready;
1368 MarkBitMap* _aux_bit_map;
1369 ShenandoahHeap* _heap;
1370 ShenandoahScanObjectStack _roots_stack; // global roots stack
1371 ShenandoahObjToScanQueueSet* _task_queues;
1372 public:
1373 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1374 _num_workers(num_workers),
1375 _init_ready(false),
1376 _aux_bit_map(bitmap),
1377 _heap(ShenandoahHeap::heap()) {
1378 // Initialize bitmap
1379 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1380 if (!_init_ready) {
1381 return;
1382 }
1383
1384 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1385 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1386
1387 _init_ready = prepare_worker_queues();
1388 }
1389
1390 ~ShenandoahParallelObjectIterator() {
1391 // Reclaim bitmap
1392 _heap->reclaim_aux_bitmap_for_iteration();
1393 // Reclaim queue for workers
1394 if (_task_queues!= nullptr) {
1395 for (uint i = 0; i < _num_workers; ++i) {
1396 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1397 if (q != nullptr) {
1398 delete q;
1399 _task_queues->register_queue(i, nullptr);
1400 }
1401 }
1402 delete _task_queues;
1403 _task_queues = nullptr;
1404 }
1405 }
1406
1407 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1408 if (_init_ready) {
1409 object_iterate_parallel(cl, worker_id, _task_queues);
1410 }
1411 }
1412
1413 private:
1414 // Divide global root_stack into worker queues
1415 bool prepare_worker_queues() {
1416 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1417 // Initialize queues for every workers
1418 for (uint i = 0; i < _num_workers; ++i) {
1419 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1420 _task_queues->register_queue(i, task_queue);
1421 }
1422 // Divide roots among the workers. Assume that object referencing distribution
1423 // is related with root kind, use round-robin to make every worker have same chance
1424 // to process every kind of roots
1425 size_t roots_num = _roots_stack.size();
1426 if (roots_num == 0) {
1427 // No work to do
1428 return false;
1429 }
1430
1431 for (uint j = 0; j < roots_num; j++) {
1432 uint stack_id = j % _num_workers;
1433 oop obj = _roots_stack.pop();
1434 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1435 }
1436 return true;
1437 }
1438
1439 void object_iterate_parallel(ObjectClosure* cl,
1440 uint worker_id,
1441 ShenandoahObjToScanQueueSet* queue_set) {
1442 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1443 assert(queue_set != nullptr, "task queue must not be null");
1444
1445 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1446 assert(q != nullptr, "object iterate queue must not be null");
1447
1448 ShenandoahMarkTask t;
1449 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1450
1451 // Work through the queue to traverse heap.
1452 // Steal when there is no task in queue.
1453 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1454 oop obj = t.obj();
1455 assert(oopDesc::is_oop(obj), "must be a valid oop");
1456 cl->do_object(obj);
1457 obj->oop_iterate(&oops);
1458 }
1459 assert(q->is_empty(), "should be empty");
1460 }
1461 };
1462
1463 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1464 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1465 }
1466
1467 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1468 void ShenandoahHeap::keep_alive(oop obj) {
1469 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1470 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1471 }
1472 }
1473
1474 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1475 for (size_t i = 0; i < num_regions(); i++) {
1476 ShenandoahHeapRegion* current = get_region(i);
1477 blk->heap_region_do(current);
1478 }
1479 }
1480
1481 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1482 private:
1483 ShenandoahHeap* const _heap;
1484 ShenandoahHeapRegionClosure* const _blk;
1485
1486 shenandoah_padding(0);
1487 volatile size_t _index;
1488 shenandoah_padding(1);
1489
1490 public:
1491 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1492 WorkerTask("Shenandoah Parallel Region Operation"),
1493 _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1494
1495 void work(uint worker_id) {
1496 ShenandoahParallelWorkerSession worker_session(worker_id);
1497 size_t stride = ShenandoahParallelRegionStride;
1498
1499 size_t max = _heap->num_regions();
1500 while (Atomic::load(&_index) < max) {
1501 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1502 size_t start = cur;
1503 size_t end = MIN2(cur + stride, max);
1504 if (start >= max) break;
1505
1506 for (size_t i = cur; i < end; i++) {
1507 ShenandoahHeapRegion* current = _heap->get_region(i);
1508 _blk->heap_region_do(current);
1509 }
1510 }
1511 }
1512 };
1513
1514 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1515 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1516 if (num_regions() > ShenandoahParallelRegionStride) {
1517 ShenandoahParallelHeapRegionTask task(blk);
1518 workers()->run_task(&task);
1519 } else {
1520 heap_region_iterate(blk);
1521 }
1522 }
1523
1524 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1525 private:
1526 ShenandoahMarkingContext* const _ctx;
1527 public:
1528 ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1529
1530 void heap_region_do(ShenandoahHeapRegion* r) {
1531 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1532 if (r->is_active()) {
1533 // Check if region needs updating its TAMS. We have updated it already during concurrent
1534 // reset, so it is very likely we don't need to do another write here.
1535 if (_ctx->top_at_mark_start(r) != r->top()) {
1536 _ctx->capture_top_at_mark_start(r);
1537 }
1538 } else {
1539 assert(_ctx->top_at_mark_start(r) == r->top(),
1540 "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
1541 }
1542 }
1543
1544 bool is_thread_safe() { return true; }
1545 };
1546
1547 class ShenandoahRendezvousClosure : public HandshakeClosure {
1548 public:
1549 inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
1550 inline void do_thread(Thread* thread) {}
1551 };
1552
1553 void ShenandoahHeap::rendezvous_threads() {
1554 ShenandoahRendezvousClosure cl;
1555 Handshake::execute(&cl);
1556 }
1557
1558 void ShenandoahHeap::recycle_trash() {
1559 free_set()->recycle_trash();
1560 }
1561
1562 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1563 private:
1564 ShenandoahMarkingContext* const _ctx;
1565 public:
1566 ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1567
1568 void heap_region_do(ShenandoahHeapRegion* r) {
1569 if (r->is_active()) {
1570 // Reset live data and set TAMS optimistically. We would recheck these under the pause
1571 // anyway to capture any updates that happened since now.
1572 r->clear_live_data();
1573 _ctx->capture_top_at_mark_start(r);
1574 }
1575 }
1576
1577 bool is_thread_safe() { return true; }
1578 };
1579
1580 void ShenandoahHeap::prepare_gc() {
1581 reset_mark_bitmap();
1582
1583 ShenandoahResetUpdateRegionStateClosure cl;
1584 parallel_heap_region_iterate(&cl);
1585 }
1586
1587 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1588 private:
1589 ShenandoahMarkingContext* const _ctx;
1590 ShenandoahHeapLock* const _lock;
1591
1592 public:
1593 ShenandoahFinalMarkUpdateRegionStateClosure() :
1594 _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1595
1596 void heap_region_do(ShenandoahHeapRegion* r) {
1597 if (r->is_active()) {
1598 // All allocations past TAMS are implicitly live, adjust the region data.
1599 // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1600 HeapWord *tams = _ctx->top_at_mark_start(r);
1601 HeapWord *top = r->top();
1602 if (top > tams) {
1603 r->increase_live_data_alloc_words(pointer_delta(top, tams));
1604 }
1605
1606 // We are about to select the collection set, make sure it knows about
1607 // current pinning status. Also, this allows trashing more regions that
1608 // now have their pinning status dropped.
1609 if (r->is_pinned()) {
1610 if (r->pin_count() == 0) {
1611 ShenandoahHeapLocker locker(_lock);
1612 r->make_unpinned();
1613 }
1614 } else {
1615 if (r->pin_count() > 0) {
1616 ShenandoahHeapLocker locker(_lock);
1617 r->make_pinned();
1618 }
1619 }
1620
1621 // Remember limit for updating refs. It's guaranteed that we get no
1622 // from-space-refs written from here on.
1623 r->set_update_watermark_at_safepoint(r->top());
1624 } else {
1625 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1626 assert(_ctx->top_at_mark_start(r) == r->top(),
1627 "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1628 }
1629 }
1630
1631 bool is_thread_safe() { return true; }
1632 };
1633
1634 void ShenandoahHeap::prepare_regions_and_collection_set(bool concurrent) {
1635 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
1636 {
1637 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states :
1638 ShenandoahPhaseTimings::degen_gc_final_update_region_states);
1639 ShenandoahFinalMarkUpdateRegionStateClosure cl;
1640 parallel_heap_region_iterate(&cl);
1641
1642 assert_pinned_region_status();
1643 }
1644
1645 {
1646 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset :
1647 ShenandoahPhaseTimings::degen_gc_choose_cset);
1648 ShenandoahHeapLocker locker(lock());
1649 _collection_set->clear();
1650 heuristics()->choose_collection_set(_collection_set);
1651 }
1652
1653 {
1654 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset :
1655 ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
1656 ShenandoahHeapLocker locker(lock());
1657 _free_set->rebuild();
1658 }
1659 }
1660
1661 void ShenandoahHeap::do_class_unloading() {
1662 _unloader.unload();
1663 }
1664
1665 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1666 // Weak refs processing
1667 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1668 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1669 ShenandoahTimingsTracker t(phase);
1670 ShenandoahGCWorkerPhase worker_phase(phase);
1671 ref_processor()->process_references(phase, workers(), false /* concurrent */);
1672 }
1673
1674 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1675 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1676
1677 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1678 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1679 // for future GCLABs here.
1680 if (UseTLAB) {
1681 ShenandoahGCPhase phase(concurrent ?
1682 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1683 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1684 gclabs_retire(ResizeTLAB);
1685 }
1686
1687 _update_refs_iterator.reset();
1688 }
1689
1690 void ShenandoahHeap::propagate_gc_state_to_java_threads() {
1691 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1692 if (_gc_state_changed) {
1693 _gc_state_changed = false;
1694 char state = gc_state();
1695 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1696 ShenandoahThreadLocalData::set_gc_state(t, state);
1697 }
1698 }
1699 }
1700
1701 void ShenandoahHeap::set_gc_state(uint mask, bool value) {
1702 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1703 _gc_state.set_cond(mask, value);
1704 _gc_state_changed = true;
1705 }
1706
1707 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1708 assert(!has_forwarded_objects(), "Not expected before/after mark phase");
1709 set_gc_state(MARKING, in_progress);
1710 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1711 }
1712
1713 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1714 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1715 set_gc_state(EVACUATION, in_progress);
1716 }
1717
1718 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
1719 if (in_progress) {
1720 _concurrent_strong_root_in_progress.set();
1721 } else {
1722 _concurrent_strong_root_in_progress.unset();
1723 }
1724 }
1725
1726 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
1727 set_gc_state(WEAK_ROOTS, cond);
1728 }
1729
1730 GCTracer* ShenandoahHeap::tracer() {
1731 return shenandoah_policy()->tracer();
1732 }
1733
1734 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1735 return _free_set->used();
1736 }
1737
1738 bool ShenandoahHeap::try_cancel_gc() {
1739 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1740 return prev == CANCELLABLE;
1741 }
1742
1743 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1744 if (try_cancel_gc()) {
1745 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1746 log_info(gc)("%s", msg.buffer());
1747 Events::log(Thread::current(), "%s", msg.buffer());
1748 }
1749 }
1750
1751 uint ShenandoahHeap::max_workers() {
1752 return _max_workers;
1753 }
1754
1755 void ShenandoahHeap::stop() {
1756 // The shutdown sequence should be able to terminate when GC is running.
1757
1758 // Step 0. Notify policy to disable event recording.
1759 _shenandoah_policy->record_shutdown();
1760
1761 // Step 1. Notify control thread that we are in shutdown.
1762 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1763 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1764 control_thread()->prepare_for_graceful_shutdown();
1765
1766 // Step 2. Notify GC workers that we are cancelling GC.
1767 cancel_gc(GCCause::_shenandoah_stop_vm);
1768
1769 // Step 3. Wait until GC worker exits normally.
1770 control_thread()->stop();
1771 }
1772
1773 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1774 if (!unload_classes()) return;
1775 ClassUnloadingContext ctx(_workers->active_workers(),
1776 true /* unregister_nmethods_during_purge */,
1777 false /* lock_codeblob_free_separately */);
1778
1779 // Unload classes and purge SystemDictionary.
1780 {
1781 ShenandoahPhaseTimings::Phase phase = full_gc ?
1782 ShenandoahPhaseTimings::full_gc_purge_class_unload :
1783 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
1784 ShenandoahIsAliveSelector is_alive;
1785 {
1786 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
1787 ShenandoahGCPhase gc_phase(phase);
1788 ShenandoahGCWorkerPhase worker_phase(phase);
1789 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
1790
1791 uint num_workers = _workers->active_workers();
1792 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
1793 _workers->run_task(&unlink_task);
1794 }
1795 // Release unloaded nmethods's memory.
1796 ClassUnloadingContext::context()->purge_and_free_nmethods();
1797 }
1798
1799 {
1800 ShenandoahGCPhase phase(full_gc ?
1801 ShenandoahPhaseTimings::full_gc_purge_cldg :
1802 ShenandoahPhaseTimings::degen_gc_purge_cldg);
1803 ClassLoaderDataGraph::purge(true /* at_safepoint */);
1804 }
1805 // Resize and verify metaspace
1806 MetaspaceGC::compute_new_size();
1807 DEBUG_ONLY(MetaspaceUtils::verify();)
1808 }
1809
1810 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
1811 // so they should not have forwarded oops.
1812 // However, we do need to "null" dead oops in the roots, if can not be done
1813 // in concurrent cycles.
1814 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
1815 uint num_workers = _workers->active_workers();
1816 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
1817 ShenandoahPhaseTimings::full_gc_purge_weak_par :
1818 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
1819 ShenandoahGCPhase phase(timing_phase);
1820 ShenandoahGCWorkerPhase worker_phase(timing_phase);
1821 // Cleanup weak roots
1822 if (has_forwarded_objects()) {
1823 ShenandoahForwardedIsAliveClosure is_alive;
1824 ShenandoahUpdateRefsClosure keep_alive;
1825 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
1826 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
1827 _workers->run_task(&cleaning_task);
1828 } else {
1829 ShenandoahIsAliveClosure is_alive;
1830 #ifdef ASSERT
1831 ShenandoahAssertNotForwardedClosure verify_cl;
1832 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
1833 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
1834 #else
1835 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
1836 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
1837 #endif
1838 _workers->run_task(&cleaning_task);
1839 }
1840 }
1841
1842 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
1843 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1844 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
1845 ShenandoahGCPhase phase(full_gc ?
1846 ShenandoahPhaseTimings::full_gc_purge :
1847 ShenandoahPhaseTimings::degen_gc_purge);
1848 stw_weak_refs(full_gc);
1849 stw_process_weak_roots(full_gc);
1850 stw_unload_classes(full_gc);
1851 }
1852
1853 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
1854 set_gc_state(HAS_FORWARDED, cond);
1855 }
1856
1857 void ShenandoahHeap::set_unload_classes(bool uc) {
1858 _unload_classes.set_cond(uc);
1859 }
1860
1861 bool ShenandoahHeap::unload_classes() const {
1862 return _unload_classes.is_set();
1863 }
1864
1865 address ShenandoahHeap::in_cset_fast_test_addr() {
1866 ShenandoahHeap* heap = ShenandoahHeap::heap();
1867 assert(heap->collection_set() != nullptr, "Sanity");
1868 return (address) heap->collection_set()->biased_map_address();
1869 }
1870
1871 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
1872 return Atomic::load(&_bytes_allocated_since_gc_start);
1873 }
1874
1875 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
1876 Atomic::store(&_bytes_allocated_since_gc_start, (size_t)0);
1877 }
1878
1879 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
1880 _degenerated_gc_in_progress.set_cond(in_progress);
1881 }
1882
1883 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
1884 _full_gc_in_progress.set_cond(in_progress);
1885 }
1886
1887 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
1888 assert (is_full_gc_in_progress(), "should be");
1889 _full_gc_move_in_progress.set_cond(in_progress);
1890 }
1891
1892 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
1893 set_gc_state(UPDATEREFS, in_progress);
1894 }
1895
1896 void ShenandoahHeap::register_nmethod(nmethod* nm) {
1897 ShenandoahCodeRoots::register_nmethod(nm);
1898 }
1899
1900 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
1901 ShenandoahCodeRoots::unregister_nmethod(nm);
1902 }
1903
1904 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
1905 heap_region_containing(o)->record_pin();
1906 }
1907
1908 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
1909 ShenandoahHeapRegion* r = heap_region_containing(o);
1910 assert(r != nullptr, "Sanity");
1911 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
1912 r->record_unpin();
1913 }
1914
1915 void ShenandoahHeap::sync_pinned_region_status() {
1916 ShenandoahHeapLocker locker(lock());
1917
1918 for (size_t i = 0; i < num_regions(); i++) {
1919 ShenandoahHeapRegion *r = get_region(i);
1920 if (r->is_active()) {
1921 if (r->is_pinned()) {
1922 if (r->pin_count() == 0) {
1923 r->make_unpinned();
1924 }
1925 } else {
1926 if (r->pin_count() > 0) {
1927 r->make_pinned();
1928 }
1929 }
1930 }
1931 }
1932
1933 assert_pinned_region_status();
1934 }
1935
1936 #ifdef ASSERT
1937 void ShenandoahHeap::assert_pinned_region_status() {
1938 for (size_t i = 0; i < num_regions(); i++) {
1939 ShenandoahHeapRegion* r = get_region(i);
1940 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
1941 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
1942 }
1943 }
1944 #endif
1945
1946 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
1947 return _gc_timer;
1948 }
1949
1950 void ShenandoahHeap::prepare_concurrent_roots() {
1951 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1952 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1953 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
1954 set_concurrent_weak_root_in_progress(true);
1955 if (unload_classes()) {
1956 _unloader.prepare();
1957 }
1958 }
1959
1960 void ShenandoahHeap::finish_concurrent_roots() {
1961 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1962 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1963 if (unload_classes()) {
1964 _unloader.finish();
1965 }
1966 }
1967
1968 #ifdef ASSERT
1969 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
1970 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
1971
1972 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1973 if (UseDynamicNumberOfGCThreads) {
1974 assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
1975 } else {
1976 // Use ParallelGCThreads inside safepoints
1977 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
1978 }
1979 } else {
1980 if (UseDynamicNumberOfGCThreads) {
1981 assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
1982 } else {
1983 // Use ConcGCThreads outside safepoints
1984 assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
1985 }
1986 }
1987 }
1988 #endif
1989
1990 ShenandoahVerifier* ShenandoahHeap::verifier() {
1991 guarantee(ShenandoahVerify, "Should be enabled");
1992 assert (_verifier != nullptr, "sanity");
1993 return _verifier;
1994 }
1995
1996 template<bool CONCURRENT>
1997 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
1998 private:
1999 ShenandoahHeap* _heap;
2000 ShenandoahRegionIterator* _regions;
2001 public:
2002 ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2003 WorkerTask("Shenandoah Update References"),
2004 _heap(ShenandoahHeap::heap()),
2005 _regions(regions) {
2006 }
2007
2008 void work(uint worker_id) {
2009 if (CONCURRENT) {
2010 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2011 ShenandoahSuspendibleThreadSetJoiner stsj;
2012 do_work<ShenandoahConcUpdateRefsClosure>();
2013 } else {
2014 ShenandoahParallelWorkerSession worker_session(worker_id);
2015 do_work<ShenandoahSTWUpdateRefsClosure>();
2016 }
2017 }
2018
2019 private:
2020 template<class T>
2021 void do_work() {
2022 T cl;
2023 ShenandoahHeapRegion* r = _regions->next();
2024 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2025 while (r != nullptr) {
2026 HeapWord* update_watermark = r->get_update_watermark();
2027 assert (update_watermark >= r->bottom(), "sanity");
2028 if (r->is_active() && !r->is_cset()) {
2029 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2030 }
2031 if (ShenandoahPacing) {
2032 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2033 }
2034 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2035 return;
2036 }
2037 r = _regions->next();
2038 }
2039 }
2040 };
2041
2042 void ShenandoahHeap::update_heap_references(bool concurrent) {
2043 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2044
2045 if (concurrent) {
2046 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2047 workers()->run_task(&task);
2048 } else {
2049 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2050 workers()->run_task(&task);
2051 }
2052 }
2053
2054
2055 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2056 private:
2057 ShenandoahHeapLock* const _lock;
2058
2059 public:
2060 ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2061
2062 void heap_region_do(ShenandoahHeapRegion* r) {
2063 // Drop unnecessary "pinned" state from regions that does not have CP marks
2064 // anymore, as this would allow trashing them.
2065
2066 if (r->is_active()) {
2067 if (r->is_pinned()) {
2068 if (r->pin_count() == 0) {
2069 ShenandoahHeapLocker locker(_lock);
2070 r->make_unpinned();
2071 }
2072 } else {
2073 if (r->pin_count() > 0) {
2074 ShenandoahHeapLocker locker(_lock);
2075 r->make_pinned();
2076 }
2077 }
2078 }
2079 }
2080
2081 bool is_thread_safe() { return true; }
2082 };
2083
2084 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2085 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2086 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2087
2088 {
2089 ShenandoahGCPhase phase(concurrent ?
2090 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2091 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2092 ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2093 parallel_heap_region_iterate(&cl);
2094
2095 assert_pinned_region_status();
2096 }
2097
2098 {
2099 ShenandoahGCPhase phase(concurrent ?
2100 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2101 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2102 trash_cset_regions();
2103 }
2104 }
2105
2106 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2107 {
2108 ShenandoahGCPhase phase(concurrent ?
2109 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2110 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2111 ShenandoahHeapLocker locker(lock());
2112 _free_set->rebuild();
2113 }
2114 }
2115
2116 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2117 print_on(st);
2118 st->cr();
2119 print_heap_regions_on(st);
2120 }
2121
2122 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2123 size_t slice = r->index() / _bitmap_regions_per_slice;
2124
2125 size_t regions_from = _bitmap_regions_per_slice * slice;
2126 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2127 for (size_t g = regions_from; g < regions_to; g++) {
2128 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2129 if (skip_self && g == r->index()) continue;
2130 if (get_region(g)->is_committed()) {
2131 return true;
2132 }
2133 }
2134 return false;
2135 }
2136
2137 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2138 shenandoah_assert_heaplocked();
2139
2140 // Bitmaps in special regions do not need commits
2141 if (_bitmap_region_special) {
2142 return true;
2143 }
2144
2145 if (is_bitmap_slice_committed(r, true)) {
2146 // Some other region from the group is already committed, meaning the bitmap
2147 // slice is already committed, we exit right away.
2148 return true;
2149 }
2150
2151 // Commit the bitmap slice:
2152 size_t slice = r->index() / _bitmap_regions_per_slice;
2153 size_t off = _bitmap_bytes_per_slice * slice;
2154 size_t len = _bitmap_bytes_per_slice;
2155 char* start = (char*) _bitmap_region.start() + off;
2156
2157 if (!os::commit_memory(start, len, false)) {
2158 return false;
2159 }
2160
2161 if (AlwaysPreTouch) {
2162 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2163 }
2164
2165 return true;
2166 }
2167
2168 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2169 shenandoah_assert_heaplocked();
2170
2171 // Bitmaps in special regions do not need uncommits
2172 if (_bitmap_region_special) {
2173 return true;
2174 }
2175
2176 if (is_bitmap_slice_committed(r, true)) {
2177 // Some other region from the group is still committed, meaning the bitmap
2178 // slice is should stay committed, exit right away.
2179 return true;
2180 }
2181
2182 // Uncommit the bitmap slice:
2183 size_t slice = r->index() / _bitmap_regions_per_slice;
2184 size_t off = _bitmap_bytes_per_slice * slice;
2185 size_t len = _bitmap_bytes_per_slice;
2186 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2187 return false;
2188 }
2189 return true;
2190 }
2191
2192 void ShenandoahHeap::safepoint_synchronize_begin() {
2193 SuspendibleThreadSet::synchronize();
2194 }
2195
2196 void ShenandoahHeap::safepoint_synchronize_end() {
2197 SuspendibleThreadSet::desynchronize();
2198 }
2199
2200 void ShenandoahHeap::entry_uncommit(double shrink_before, size_t shrink_until) {
2201 static const char *msg = "Concurrent uncommit";
2202 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
2203 EventMark em("%s", msg);
2204
2205 op_uncommit(shrink_before, shrink_until);
2206 }
2207
2208 void ShenandoahHeap::try_inject_alloc_failure() {
2209 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2210 _inject_alloc_failure.set();
2211 os::naked_short_sleep(1);
2212 if (cancelled_gc()) {
2213 log_info(gc)("Allocation failure was successfully injected");
2214 }
2215 }
2216 }
2217
2218 bool ShenandoahHeap::should_inject_alloc_failure() {
2219 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2220 }
2221
2222 void ShenandoahHeap::initialize_serviceability() {
2223 _memory_pool = new ShenandoahMemoryPool(this);
2224 _cycle_memory_manager.add_pool(_memory_pool);
2225 _stw_memory_manager.add_pool(_memory_pool);
2226 }
2227
2228 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2229 GrowableArray<GCMemoryManager*> memory_managers(2);
2230 memory_managers.append(&_cycle_memory_manager);
2231 memory_managers.append(&_stw_memory_manager);
2232 return memory_managers;
2233 }
2234
2235 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2236 GrowableArray<MemoryPool*> memory_pools(1);
2237 memory_pools.append(_memory_pool);
2238 return memory_pools;
2239 }
2240
2241 MemoryUsage ShenandoahHeap::memory_usage() {
2242 return _memory_pool->get_memory_usage();
2243 }
2244
2245 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2246 _heap(ShenandoahHeap::heap()),
2247 _index(0) {}
2248
2249 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2250 _heap(heap),
2251 _index(0) {}
2252
2253 void ShenandoahRegionIterator::reset() {
2254 _index = 0;
2255 }
2256
2257 bool ShenandoahRegionIterator::has_next() const {
2258 return _index < _heap->num_regions();
2259 }
2260
2261 char ShenandoahHeap::gc_state() const {
2262 return _gc_state.raw_value();
2263 }
2264
2265 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2266 #ifdef ASSERT
2267 assert(_liveness_cache != nullptr, "sanity");
2268 assert(worker_id < _max_workers, "sanity");
2269 for (uint i = 0; i < num_regions(); i++) {
2270 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2271 }
2272 #endif
2273 return _liveness_cache[worker_id];
2274 }
2275
2276 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2277 assert(worker_id < _max_workers, "sanity");
2278 assert(_liveness_cache != nullptr, "sanity");
2279 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2280 for (uint i = 0; i < num_regions(); i++) {
2281 ShenandoahLiveData live = ld[i];
2282 if (live > 0) {
2283 ShenandoahHeapRegion* r = get_region(i);
2284 r->increase_live_data_gc_words(live);
2285 ld[i] = 0;
2286 }
2287 }
2288 }
2289
2290 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2291 if (is_idle()) return false;
2292
2293 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2294 // marking phase.
2295 if (is_concurrent_mark_in_progress() &&
2296 !marking_context()->allocated_after_mark_start(obj)) {
2297 return true;
2298 }
2299
2300 // Can not guarantee obj is deeply good.
2301 if (has_forwarded_objects()) {
2302 return true;
2303 }
2304
2305 return false;
2306 }