1 /*
2 * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/universe.hpp"
29
30 #include "gc/shared/classUnloadingContext.hpp"
31 #include "gc/shared/gcArguments.hpp"
32 #include "gc/shared/gcTimer.hpp"
33 #include "gc/shared/gcTraceTime.inline.hpp"
34 #include "gc/shared/locationPrinter.inline.hpp"
35 #include "gc/shared/memAllocator.hpp"
36 #include "gc/shared/plab.hpp"
37 #include "gc/shared/tlab_globals.hpp"
38
39 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
40 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
41 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
42 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
43 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
44 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
45 #include "gc/shenandoah/shenandoahControlThread.hpp"
46 #include "gc/shenandoah/shenandoahFreeSet.hpp"
47 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
48 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
49 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
50 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
51 #include "gc/shenandoah/shenandoahInitLogger.hpp"
52 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
53 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
54 #include "gc/shenandoah/shenandoahMetrics.hpp"
55 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
56 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
57 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
58 #include "gc/shenandoah/shenandoahPadding.hpp"
59 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
60 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
61 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
62 #include "gc/shenandoah/shenandoahSTWMark.hpp"
63 #include "gc/shenandoah/shenandoahUtils.hpp"
64 #include "gc/shenandoah/shenandoahVerifier.hpp"
65 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
66 #include "gc/shenandoah/shenandoahVMOperations.hpp"
67 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
68 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
69 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
70 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
71 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
72 #if INCLUDE_JFR
73 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
74 #endif
75
76 #include "classfile/systemDictionary.hpp"
77 #include "code/codeCache.hpp"
78 #include "memory/classLoaderMetaspace.hpp"
79 #include "memory/metaspaceUtils.hpp"
80 #include "oops/compressedOops.inline.hpp"
81 #include "prims/jvmtiTagMap.hpp"
82 #include "runtime/atomic.hpp"
83 #include "runtime/globals.hpp"
84 #include "runtime/interfaceSupport.inline.hpp"
85 #include "runtime/java.hpp"
86 #include "runtime/orderAccess.hpp"
87 #include "runtime/safepointMechanism.hpp"
88 #include "runtime/vmThread.hpp"
89 #include "services/mallocTracker.hpp"
90 #include "services/memTracker.hpp"
91 #include "utilities/events.hpp"
92 #include "utilities/powerOfTwo.hpp"
93
94 class ShenandoahPretouchHeapTask : public WorkerTask {
95 private:
96 ShenandoahRegionIterator _regions;
97 const size_t _page_size;
98 public:
99 ShenandoahPretouchHeapTask(size_t page_size) :
100 WorkerTask("Shenandoah Pretouch Heap"),
101 _page_size(page_size) {}
102
103 virtual void work(uint worker_id) {
104 ShenandoahHeapRegion* r = _regions.next();
105 while (r != nullptr) {
106 if (r->is_committed()) {
107 os::pretouch_memory(r->bottom(), r->end(), _page_size);
108 }
109 r = _regions.next();
110 }
111 }
112 };
113
114 class ShenandoahPretouchBitmapTask : public WorkerTask {
115 private:
116 ShenandoahRegionIterator _regions;
117 char* _bitmap_base;
118 const size_t _bitmap_size;
119 const size_t _page_size;
120 public:
121 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
122 WorkerTask("Shenandoah Pretouch Bitmap"),
123 _bitmap_base(bitmap_base),
124 _bitmap_size(bitmap_size),
125 _page_size(page_size) {}
126
127 virtual void work(uint worker_id) {
128 ShenandoahHeapRegion* r = _regions.next();
129 while (r != nullptr) {
130 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
131 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
132 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
133
134 if (r->is_committed()) {
135 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
136 }
137
138 r = _regions.next();
139 }
140 }
141 };
142
143 jint ShenandoahHeap::initialize() {
144 //
145 // Figure out heap sizing
146 //
147
148 size_t init_byte_size = InitialHeapSize;
149 size_t min_byte_size = MinHeapSize;
150 size_t max_byte_size = MaxHeapSize;
151 size_t heap_alignment = HeapAlignment;
152
153 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
154
155 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
156 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
157
158 _num_regions = ShenandoahHeapRegion::region_count();
159 assert(_num_regions == (max_byte_size / reg_size_bytes),
160 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
161 _num_regions, max_byte_size, reg_size_bytes);
162
163 // Now we know the number of regions, initialize the heuristics.
164 initialize_heuristics();
165
166 size_t num_committed_regions = init_byte_size / reg_size_bytes;
167 num_committed_regions = MIN2(num_committed_regions, _num_regions);
168 assert(num_committed_regions <= _num_regions, "sanity");
169 _initial_size = num_committed_regions * reg_size_bytes;
170
171 size_t num_min_regions = min_byte_size / reg_size_bytes;
172 num_min_regions = MIN2(num_min_regions, _num_regions);
173 assert(num_min_regions <= _num_regions, "sanity");
174 _minimum_size = num_min_regions * reg_size_bytes;
175
176 // Default to max heap size.
177 _soft_max_size = _num_regions * reg_size_bytes;
178
179 _committed = _initial_size;
180
181 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
182 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
183 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
184
185 //
186 // Reserve and commit memory for heap
187 //
188
189 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
190 initialize_reserved_region(heap_rs);
191 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
192 _heap_region_special = heap_rs.special();
193
194 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
195 "Misaligned heap: " PTR_FORMAT, p2i(base()));
196
197 #if SHENANDOAH_OPTIMIZED_MARKTASK
198 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
199 // Fail if we ever attempt to address more than we can.
200 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
201 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
202 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
203 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
204 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
205 vm_exit_during_initialization("Fatal Error", buf);
206 }
207 #endif
208
209 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
210 if (!_heap_region_special) {
211 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
212 "Cannot commit heap memory");
213 }
214
215 //
216 // Reserve and commit memory for bitmap(s)
217 //
218
219 _bitmap_size = ShenandoahMarkBitMap::compute_size(heap_rs.size());
220 _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
221
222 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
223
224 guarantee(bitmap_bytes_per_region != 0,
225 "Bitmap bytes per region should not be zero");
226 guarantee(is_power_of_2(bitmap_bytes_per_region),
227 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
228
229 if (bitmap_page_size > bitmap_bytes_per_region) {
230 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
231 _bitmap_bytes_per_slice = bitmap_page_size;
232 } else {
233 _bitmap_regions_per_slice = 1;
234 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
235 }
236
237 guarantee(_bitmap_regions_per_slice >= 1,
238 "Should have at least one region per slice: " SIZE_FORMAT,
239 _bitmap_regions_per_slice);
240
241 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
242 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
243 _bitmap_bytes_per_slice, bitmap_page_size);
244
245 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
246 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
247 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
248 _bitmap_region_special = bitmap.special();
249
250 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
251 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
252 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
253 if (!_bitmap_region_special) {
254 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
255 "Cannot commit bitmap memory");
256 }
257
258 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions, _max_workers);
259
260 if (ShenandoahVerify) {
261 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
262 if (!verify_bitmap.special()) {
263 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
264 "Cannot commit verification bitmap memory");
265 }
266 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
267 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
268 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
269 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
270 }
271
272 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
273 ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
274 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
275 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
276 _aux_bitmap_region_special = aux_bitmap.special();
277 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
278
279 //
280 // Create regions and region sets
281 //
282 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
283 size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
284 region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
285
286 ReservedSpace region_storage(region_storage_size, region_page_size);
287 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
288 if (!region_storage.special()) {
289 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
290 "Cannot commit region memory");
291 }
292
293 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
294 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
295 // If not successful, bite a bullet and allocate at whatever address.
296 {
297 size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
298 size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
299
300 uintptr_t min = round_up_power_of_2(cset_align);
301 uintptr_t max = (1u << 30u);
302
303 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
304 char* req_addr = (char*)addr;
305 assert(is_aligned(req_addr, cset_align), "Should be aligned");
306 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size(), req_addr);
307 if (cset_rs.is_reserved()) {
308 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
309 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
310 break;
311 }
312 }
313
314 if (_collection_set == nullptr) {
315 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size());
316 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
317 }
318 }
319
320 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
321 _free_set = new ShenandoahFreeSet(this, _num_regions);
322
323 {
324 ShenandoahHeapLocker locker(lock());
325
326 for (size_t i = 0; i < _num_regions; i++) {
327 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
328 bool is_committed = i < num_committed_regions;
329 void* loc = region_storage.base() + i * region_align;
330
331 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
332 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
333
334 _marking_context->initialize_top_at_mark_start(r);
335 _regions[i] = r;
336 assert(!collection_set()->is_in(i), "New region should not be in collection set");
337 }
338
339 // Initialize to complete
340 _marking_context->mark_complete();
341
342 _free_set->rebuild();
343 }
344
345 if (AlwaysPreTouch) {
346 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
347 // before initialize() below zeroes it with initializing thread. For any given region,
348 // we touch the region and the corresponding bitmaps from the same thread.
349 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
350
351 _pretouch_heap_page_size = heap_page_size;
352 _pretouch_bitmap_page_size = bitmap_page_size;
353
354 #ifdef LINUX
355 // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
356 // pages. But, the kernel needs to know that every small page is used, in order to coalesce
357 // them into huge one. Therefore, we need to pretouch with smaller pages.
358 if (UseTransparentHugePages) {
359 _pretouch_heap_page_size = (size_t)os::vm_page_size();
360 _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
361 }
362 #endif
363
364 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
365 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
366
367 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
368 _workers->run_task(&bcl);
369
370 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
371 _workers->run_task(&hcl);
372 }
373
374 //
375 // Initialize the rest of GC subsystems
376 //
377
378 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
379 for (uint worker = 0; worker < _max_workers; worker++) {
380 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
381 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
382 }
383
384 // There should probably be Shenandoah-specific options for these,
385 // just as there are G1-specific options.
386 {
387 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
388 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
389 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
390 }
391
392 _monitoring_support = new ShenandoahMonitoringSupport(this);
393 _phase_timings = new ShenandoahPhaseTimings(max_workers());
394 ShenandoahCodeRoots::initialize();
395
396 if (ShenandoahPacing) {
397 _pacer = new ShenandoahPacer(this);
398 _pacer->setup_for_idle();
399 } else {
400 _pacer = nullptr;
401 }
402
403 _control_thread = new ShenandoahControlThread();
404
405 ShenandoahInitLogger::print();
406
407 return JNI_OK;
408 }
409
410 void ShenandoahHeap::initialize_mode() {
411 if (ShenandoahGCMode != nullptr) {
412 if (strcmp(ShenandoahGCMode, "satb") == 0) {
413 _gc_mode = new ShenandoahSATBMode();
414 } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
415 _gc_mode = new ShenandoahIUMode();
416 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
417 _gc_mode = new ShenandoahPassiveMode();
418 } else {
419 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
420 }
421 } else {
422 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
423 }
424 _gc_mode->initialize_flags();
425 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
426 vm_exit_during_initialization(
427 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
428 _gc_mode->name()));
429 }
430 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
431 vm_exit_during_initialization(
432 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
433 _gc_mode->name()));
434 }
435 }
436
437 void ShenandoahHeap::initialize_heuristics() {
438 assert(_gc_mode != nullptr, "Must be initialized");
439 _heuristics = _gc_mode->initialize_heuristics();
440
441 if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
442 vm_exit_during_initialization(
443 err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
444 _heuristics->name()));
445 }
446 if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
447 vm_exit_during_initialization(
448 err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
449 _heuristics->name()));
450 }
451 }
452
453 #ifdef _MSC_VER
454 #pragma warning( push )
455 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
456 #endif
457
458 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
459 CollectedHeap(),
460 _initial_size(0),
461 _used(0),
462 _committed(0),
463 _bytes_allocated_since_gc_start(0),
464 _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
465 _workers(nullptr),
466 _safepoint_workers(nullptr),
467 _heap_region_special(false),
468 _num_regions(0),
469 _regions(nullptr),
470 _update_refs_iterator(this),
471 _gc_state_changed(false),
472 _control_thread(nullptr),
473 _shenandoah_policy(policy),
474 _gc_mode(nullptr),
475 _heuristics(nullptr),
476 _free_set(nullptr),
477 _pacer(nullptr),
478 _verifier(nullptr),
479 _phase_timings(nullptr),
480 _monitoring_support(nullptr),
481 _memory_pool(nullptr),
482 _stw_memory_manager("Shenandoah Pauses"),
483 _cycle_memory_manager("Shenandoah Cycles"),
484 _gc_timer(new ConcurrentGCTimer()),
485 _soft_ref_policy(),
486 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
487 _ref_processor(new ShenandoahReferenceProcessor(MAX2(_max_workers, 1U))),
488 _marking_context(nullptr),
489 _bitmap_size(0),
490 _bitmap_regions_per_slice(0),
491 _bitmap_bytes_per_slice(0),
492 _bitmap_region_special(false),
493 _aux_bitmap_region_special(false),
494 _liveness_cache(nullptr),
495 _collection_set(nullptr)
496 {
497 // Initialize GC mode early, so we can adjust barrier support
498 initialize_mode();
499 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
500
501 _max_workers = MAX2(_max_workers, 1U);
502 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
503 if (_workers == nullptr) {
504 vm_exit_during_initialization("Failed necessary allocation.");
505 } else {
506 _workers->initialize_workers();
507 }
508
509 if (ParallelGCThreads > 1) {
510 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread",
511 ParallelGCThreads);
512 _safepoint_workers->initialize_workers();
513 }
514 }
515
516 #ifdef _MSC_VER
517 #pragma warning( pop )
518 #endif
519
520 class ShenandoahResetBitmapTask : public WorkerTask {
521 private:
522 ShenandoahRegionIterator _regions;
523
524 public:
525 ShenandoahResetBitmapTask() :
526 WorkerTask("Shenandoah Reset Bitmap") {}
527
528 void work(uint worker_id) {
529 ShenandoahHeapRegion* region = _regions.next();
530 ShenandoahHeap* heap = ShenandoahHeap::heap();
531 ShenandoahMarkingContext* const ctx = heap->marking_context();
532 while (region != nullptr) {
533 if (heap->is_bitmap_slice_committed(region)) {
534 ctx->clear_bitmap(region);
535 }
536 region = _regions.next();
537 }
538 }
539 };
540
541 void ShenandoahHeap::reset_mark_bitmap() {
542 assert_gc_workers(_workers->active_workers());
543 mark_incomplete_marking_context();
544
545 ShenandoahResetBitmapTask task;
546 _workers->run_task(&task);
547 }
548
549 void ShenandoahHeap::print_on(outputStream* st) const {
550 st->print_cr("Shenandoah Heap");
551 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
552 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
553 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
554 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
555 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
556 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
557 num_regions(),
558 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
559 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
560
561 st->print("Status: ");
562 if (has_forwarded_objects()) st->print("has forwarded objects, ");
563 if (is_concurrent_mark_in_progress()) st->print("marking, ");
564 if (is_evacuation_in_progress()) st->print("evacuating, ");
565 if (is_update_refs_in_progress()) st->print("updating refs, ");
566 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
567 if (is_full_gc_in_progress()) st->print("full gc, ");
568 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
569 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
570 if (is_concurrent_strong_root_in_progress() &&
571 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
572
573 if (cancelled_gc()) {
574 st->print("cancelled");
575 } else {
576 st->print("not cancelled");
577 }
578 st->cr();
579
580 st->print_cr("Reserved region:");
581 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
582 p2i(reserved_region().start()),
583 p2i(reserved_region().end()));
584
585 ShenandoahCollectionSet* cset = collection_set();
586 st->print_cr("Collection set:");
587 if (cset != nullptr) {
588 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
589 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
590 } else {
591 st->print_cr(" (null)");
592 }
593
594 st->cr();
595 MetaspaceUtils::print_on(st);
596
597 if (Verbose) {
598 st->cr();
599 print_heap_regions_on(st);
600 }
601 }
602
603 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
604 public:
605 void do_thread(Thread* thread) {
606 assert(thread != nullptr, "Sanity");
607 assert(thread->is_Worker_thread(), "Only worker thread expected");
608 ShenandoahThreadLocalData::initialize_gclab(thread);
609 }
610 };
611
612 void ShenandoahHeap::post_initialize() {
613 CollectedHeap::post_initialize();
614 MutexLocker ml(Threads_lock);
615
616 ShenandoahInitWorkerGCLABClosure init_gclabs;
617 _workers->threads_do(&init_gclabs);
618
619 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
620 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
621 _workers->set_initialize_gclab();
622 if (_safepoint_workers != nullptr) {
623 _safepoint_workers->threads_do(&init_gclabs);
624 _safepoint_workers->set_initialize_gclab();
625 }
626
627 _heuristics->initialize();
628
629 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
630 }
631
632 size_t ShenandoahHeap::used() const {
633 return Atomic::load(&_used);
634 }
635
636 size_t ShenandoahHeap::committed() const {
637 return Atomic::load(&_committed);
638 }
639
640 void ShenandoahHeap::increase_committed(size_t bytes) {
641 shenandoah_assert_heaplocked_or_safepoint();
642 _committed += bytes;
643 }
644
645 void ShenandoahHeap::decrease_committed(size_t bytes) {
646 shenandoah_assert_heaplocked_or_safepoint();
647 _committed -= bytes;
648 }
649
650 void ShenandoahHeap::increase_used(size_t bytes) {
651 Atomic::add(&_used, bytes, memory_order_relaxed);
652 }
653
654 void ShenandoahHeap::set_used(size_t bytes) {
655 Atomic::store(&_used, bytes);
656 }
657
658 void ShenandoahHeap::decrease_used(size_t bytes) {
659 assert(used() >= bytes, "never decrease heap size by more than we've left");
660 Atomic::sub(&_used, bytes, memory_order_relaxed);
661 }
662
663 void ShenandoahHeap::increase_allocated(size_t bytes) {
664 Atomic::add(&_bytes_allocated_since_gc_start, bytes, memory_order_relaxed);
665 }
666
667 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
668 size_t bytes = words * HeapWordSize;
669 if (!waste) {
670 increase_used(bytes);
671 }
672 increase_allocated(bytes);
673 if (ShenandoahPacing) {
674 control_thread()->pacing_notify_alloc(words);
675 if (waste) {
676 pacer()->claim_for_alloc(words, true);
677 }
678 }
679 }
680
681 size_t ShenandoahHeap::capacity() const {
682 return committed();
683 }
684
685 size_t ShenandoahHeap::max_capacity() const {
686 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
687 }
688
689 size_t ShenandoahHeap::soft_max_capacity() const {
690 size_t v = Atomic::load(&_soft_max_size);
691 assert(min_capacity() <= v && v <= max_capacity(),
692 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
693 min_capacity(), v, max_capacity());
694 return v;
695 }
696
697 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
698 assert(min_capacity() <= v && v <= max_capacity(),
699 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
700 min_capacity(), v, max_capacity());
701 Atomic::store(&_soft_max_size, v);
702 }
703
704 size_t ShenandoahHeap::min_capacity() const {
705 return _minimum_size;
706 }
707
708 size_t ShenandoahHeap::initial_capacity() const {
709 return _initial_size;
710 }
711
712 bool ShenandoahHeap::is_in(const void* p) const {
713 HeapWord* heap_base = (HeapWord*) base();
714 HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
715 return p >= heap_base && p < last_region_end;
716 }
717
718 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
719 assert (ShenandoahUncommit, "should be enabled");
720
721 // Application allocates from the beginning of the heap, and GC allocates at
722 // the end of it. It is more efficient to uncommit from the end, so that applications
723 // could enjoy the near committed regions. GC allocations are much less frequent,
724 // and therefore can accept the committing costs.
725
726 size_t count = 0;
727 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
728 ShenandoahHeapRegion* r = get_region(i - 1);
729 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
730 ShenandoahHeapLocker locker(lock());
731 if (r->is_empty_committed()) {
732 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
733 break;
734 }
735
736 r->make_uncommitted();
737 count++;
738 }
739 }
740 SpinPause(); // allow allocators to take the lock
741 }
742
743 if (count > 0) {
744 control_thread()->notify_heap_changed();
745 }
746 }
747
748 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
749 // New object should fit the GCLAB size
750 size_t min_size = MAX2(size, PLAB::min_size());
751
752 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
753 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
754 new_size = MIN2(new_size, PLAB::max_size());
755 new_size = MAX2(new_size, PLAB::min_size());
756
757 // Record new heuristic value even if we take any shortcut. This captures
758 // the case when moderately-sized objects always take a shortcut. At some point,
759 // heuristics should catch up with them.
760 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
761
762 if (new_size < size) {
763 // New size still does not fit the object. Fall back to shared allocation.
764 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
765 return nullptr;
766 }
767
768 // Retire current GCLAB, and allocate a new one.
769 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
770 gclab->retire();
771
772 size_t actual_size = 0;
773 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
774 if (gclab_buf == nullptr) {
775 return nullptr;
776 }
777
778 assert (size <= actual_size, "allocation should fit");
779
780 // ...and clear or zap just allocated TLAB, if needed.
781 if (ZeroTLAB) {
782 Copy::zero_to_words(gclab_buf, actual_size);
783 } else if (ZapTLAB) {
784 // Skip mangling the space corresponding to the object header to
785 // ensure that the returned space is not considered parsable by
786 // any concurrent GC thread.
787 size_t hdr_size = oopDesc::header_size();
788 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
789 }
790 gclab->set_buf(gclab_buf, actual_size);
791 return gclab->allocate(size);
792 }
793
794 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
795 size_t requested_size,
796 size_t* actual_size) {
797 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
798 HeapWord* res = allocate_memory(req);
799 if (res != nullptr) {
800 *actual_size = req.actual_size();
801 } else {
802 *actual_size = 0;
803 }
804 return res;
805 }
806
807 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
808 size_t word_size,
809 size_t* actual_size) {
810 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
811 HeapWord* res = allocate_memory(req);
812 if (res != nullptr) {
813 *actual_size = req.actual_size();
814 } else {
815 *actual_size = 0;
816 }
817 return res;
818 }
819
820 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
821 intptr_t pacer_epoch = 0;
822 bool in_new_region = false;
823 HeapWord* result = nullptr;
824
825 if (req.is_mutator_alloc()) {
826 if (ShenandoahPacing) {
827 pacer()->pace_for_alloc(req.size());
828 pacer_epoch = pacer()->epoch();
829 }
830
831 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
832 result = allocate_memory_under_lock(req, in_new_region);
833 }
834
835 // Allocation failed, block until control thread reacted, then retry allocation.
836 //
837 // It might happen that one of the threads requesting allocation would unblock
838 // way later after GC happened, only to fail the second allocation, because
839 // other threads have already depleted the free storage. In this case, a better
840 // strategy is to try again, as long as GC makes progress (or until at least
841 // one full GC has completed).
842 size_t original_count = shenandoah_policy()->full_gc_count();
843 while (result == nullptr
844 && (_progress_last_gc.is_set() || original_count == shenandoah_policy()->full_gc_count())) {
845 control_thread()->handle_alloc_failure(req);
846 result = allocate_memory_under_lock(req, in_new_region);
847 }
848 } else {
849 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
850 result = allocate_memory_under_lock(req, in_new_region);
851 // Do not call handle_alloc_failure() here, because we cannot block.
852 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
853 }
854
855 if (in_new_region) {
856 control_thread()->notify_heap_changed();
857 }
858
859 if (result != nullptr) {
860 size_t requested = req.size();
861 size_t actual = req.actual_size();
862
863 assert (req.is_lab_alloc() || (requested == actual),
864 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
865 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
866
867 if (req.is_mutator_alloc()) {
868 notify_mutator_alloc_words(actual, false);
869
870 // If we requested more than we were granted, give the rest back to pacer.
871 // This only matters if we are in the same pacing epoch: do not try to unpace
872 // over the budget for the other phase.
873 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
874 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
875 }
876 } else {
877 increase_used(actual*HeapWordSize);
878 }
879 }
880
881 return result;
882 }
883
884 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
885 // If we are dealing with mutator allocation, then we may need to block for safepoint.
886 // We cannot block for safepoint for GC allocations, because there is a high chance
887 // we are already running at safepoint or from stack watermark machinery, and we cannot
888 // block again.
889 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
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 size_t const _stride;
1483
1484 shenandoah_padding(0);
1485 volatile size_t _index;
1486 shenandoah_padding(1);
1487
1488 public:
1489 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
1490 WorkerTask("Shenandoah Parallel Region Operation"),
1491 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
1492
1493 void work(uint worker_id) {
1494 ShenandoahParallelWorkerSession worker_session(worker_id);
1495 size_t stride = _stride;
1496
1497 size_t max = _heap->num_regions();
1498 while (Atomic::load(&_index) < max) {
1499 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1500 size_t start = cur;
1501 size_t end = MIN2(cur + stride, max);
1502 if (start >= max) break;
1503
1504 for (size_t i = cur; i < end; i++) {
1505 ShenandoahHeapRegion* current = _heap->get_region(i);
1506 _blk->heap_region_do(current);
1507 }
1508 }
1509 }
1510 };
1511
1512 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1513 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1514 const uint active_workers = workers()->active_workers();
1515 const size_t n_regions = num_regions();
1516 size_t stride = ShenandoahParallelRegionStride;
1517 if (stride == 0 && active_workers > 1) {
1518 // Automatically derive the stride to balance the work between threads
1519 // evenly. Do not try to split work if below the reasonable threshold.
1520 constexpr size_t threshold = 4096;
1521 stride = n_regions <= threshold ?
1522 threshold :
1523 (n_regions + active_workers - 1) / active_workers;
1524 }
1525
1526 if (n_regions > stride && active_workers > 1) {
1527 ShenandoahParallelHeapRegionTask task(blk, stride);
1528 workers()->run_task(&task);
1529 } else {
1530 heap_region_iterate(blk);
1531 }
1532 }
1533
1534 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1535 private:
1536 ShenandoahMarkingContext* const _ctx;
1537 public:
1538 ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1539
1540 void heap_region_do(ShenandoahHeapRegion* r) {
1541 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1542 if (r->is_active()) {
1543 // Check if region needs updating its TAMS. We have updated it already during concurrent
1544 // reset, so it is very likely we don't need to do another write here.
1545 if (_ctx->top_at_mark_start(r) != r->top()) {
1546 _ctx->capture_top_at_mark_start(r);
1547 }
1548 } else {
1549 assert(_ctx->top_at_mark_start(r) == r->top(),
1550 "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
1551 }
1552 }
1553
1554 bool is_thread_safe() { return true; }
1555 };
1556
1557 class ShenandoahRendezvousClosure : public HandshakeClosure {
1558 public:
1559 inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
1560 inline void do_thread(Thread* thread) {}
1561 };
1562
1563 void ShenandoahHeap::rendezvous_threads() {
1564 ShenandoahRendezvousClosure cl;
1565 Handshake::execute(&cl);
1566 }
1567
1568 void ShenandoahHeap::recycle_trash() {
1569 free_set()->recycle_trash();
1570 }
1571
1572 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1573 private:
1574 ShenandoahMarkingContext* const _ctx;
1575 public:
1576 ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1577
1578 void heap_region_do(ShenandoahHeapRegion* r) {
1579 if (r->is_active()) {
1580 // Reset live data and set TAMS optimistically. We would recheck these under the pause
1581 // anyway to capture any updates that happened since now.
1582 r->clear_live_data();
1583 _ctx->capture_top_at_mark_start(r);
1584 }
1585 }
1586
1587 bool is_thread_safe() { return true; }
1588 };
1589
1590 void ShenandoahHeap::prepare_gc() {
1591 reset_mark_bitmap();
1592
1593 ShenandoahResetUpdateRegionStateClosure cl;
1594 parallel_heap_region_iterate(&cl);
1595 }
1596
1597 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1598 private:
1599 ShenandoahMarkingContext* const _ctx;
1600 ShenandoahHeapLock* const _lock;
1601
1602 public:
1603 ShenandoahFinalMarkUpdateRegionStateClosure() :
1604 _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1605
1606 void heap_region_do(ShenandoahHeapRegion* r) {
1607 if (r->is_active()) {
1608 // All allocations past TAMS are implicitly live, adjust the region data.
1609 // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1610 HeapWord *tams = _ctx->top_at_mark_start(r);
1611 HeapWord *top = r->top();
1612 if (top > tams) {
1613 r->increase_live_data_alloc_words(pointer_delta(top, tams));
1614 }
1615
1616 // We are about to select the collection set, make sure it knows about
1617 // current pinning status. Also, this allows trashing more regions that
1618 // now have their pinning status dropped.
1619 if (r->is_pinned()) {
1620 if (r->pin_count() == 0) {
1621 ShenandoahHeapLocker locker(_lock);
1622 r->make_unpinned();
1623 }
1624 } else {
1625 if (r->pin_count() > 0) {
1626 ShenandoahHeapLocker locker(_lock);
1627 r->make_pinned();
1628 }
1629 }
1630
1631 // Remember limit for updating refs. It's guaranteed that we get no
1632 // from-space-refs written from here on.
1633 r->set_update_watermark_at_safepoint(r->top());
1634 } else {
1635 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1636 assert(_ctx->top_at_mark_start(r) == r->top(),
1637 "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1638 }
1639 }
1640
1641 bool is_thread_safe() { return true; }
1642 };
1643
1644 void ShenandoahHeap::prepare_regions_and_collection_set(bool concurrent) {
1645 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
1646 {
1647 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states :
1648 ShenandoahPhaseTimings::degen_gc_final_update_region_states);
1649 ShenandoahFinalMarkUpdateRegionStateClosure cl;
1650 parallel_heap_region_iterate(&cl);
1651
1652 assert_pinned_region_status();
1653 }
1654
1655 {
1656 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset :
1657 ShenandoahPhaseTimings::degen_gc_choose_cset);
1658 ShenandoahHeapLocker locker(lock());
1659 _collection_set->clear();
1660 heuristics()->choose_collection_set(_collection_set);
1661 }
1662
1663 {
1664 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset :
1665 ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
1666 ShenandoahHeapLocker locker(lock());
1667 _free_set->rebuild();
1668 }
1669 }
1670
1671 void ShenandoahHeap::do_class_unloading() {
1672 _unloader.unload();
1673 }
1674
1675 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1676 // Weak refs processing
1677 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1678 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1679 ShenandoahTimingsTracker t(phase);
1680 ShenandoahGCWorkerPhase worker_phase(phase);
1681 ref_processor()->process_references(phase, workers(), false /* concurrent */);
1682 }
1683
1684 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1685 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1686
1687 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1688 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1689 // for future GCLABs here.
1690 if (UseTLAB) {
1691 ShenandoahGCPhase phase(concurrent ?
1692 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1693 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1694 gclabs_retire(ResizeTLAB);
1695 }
1696
1697 _update_refs_iterator.reset();
1698 }
1699
1700 void ShenandoahHeap::propagate_gc_state_to_java_threads() {
1701 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1702 if (_gc_state_changed) {
1703 _gc_state_changed = false;
1704 char state = gc_state();
1705 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1706 ShenandoahThreadLocalData::set_gc_state(t, state);
1707 }
1708 }
1709 }
1710
1711 void ShenandoahHeap::set_gc_state(uint mask, bool value) {
1712 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1713 _gc_state.set_cond(mask, value);
1714 _gc_state_changed = true;
1715 }
1716
1717 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1718 assert(!has_forwarded_objects(), "Not expected before/after mark phase");
1719 set_gc_state(MARKING, in_progress);
1720 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1721 }
1722
1723 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1724 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1725 set_gc_state(EVACUATION, in_progress);
1726 }
1727
1728 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
1729 if (in_progress) {
1730 _concurrent_strong_root_in_progress.set();
1731 } else {
1732 _concurrent_strong_root_in_progress.unset();
1733 }
1734 }
1735
1736 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
1737 set_gc_state(WEAK_ROOTS, cond);
1738 }
1739
1740 GCTracer* ShenandoahHeap::tracer() {
1741 return shenandoah_policy()->tracer();
1742 }
1743
1744 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1745 return _free_set->used();
1746 }
1747
1748 bool ShenandoahHeap::try_cancel_gc() {
1749 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1750 return prev == CANCELLABLE;
1751 }
1752
1753 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1754 if (try_cancel_gc()) {
1755 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1756 log_info(gc)("%s", msg.buffer());
1757 Events::log(Thread::current(), "%s", msg.buffer());
1758 }
1759 }
1760
1761 uint ShenandoahHeap::max_workers() {
1762 return _max_workers;
1763 }
1764
1765 void ShenandoahHeap::stop() {
1766 // The shutdown sequence should be able to terminate when GC is running.
1767
1768 // Step 0. Notify policy to disable event recording.
1769 _shenandoah_policy->record_shutdown();
1770
1771 // Step 1. Notify control thread that we are in shutdown.
1772 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1773 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1774 control_thread()->prepare_for_graceful_shutdown();
1775
1776 // Step 2. Notify GC workers that we are cancelling GC.
1777 cancel_gc(GCCause::_shenandoah_stop_vm);
1778
1779 // Step 3. Wait until GC worker exits normally.
1780 control_thread()->stop();
1781 }
1782
1783 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1784 if (!unload_classes()) return;
1785 ClassUnloadingContext ctx(_workers->active_workers(),
1786 true /* unregister_nmethods_during_purge */,
1787 false /* lock_codeblob_free_separately */);
1788
1789 // Unload classes and purge SystemDictionary.
1790 {
1791 ShenandoahPhaseTimings::Phase phase = full_gc ?
1792 ShenandoahPhaseTimings::full_gc_purge_class_unload :
1793 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
1794 ShenandoahIsAliveSelector is_alive;
1795 {
1796 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
1797 ShenandoahGCPhase gc_phase(phase);
1798 ShenandoahGCWorkerPhase worker_phase(phase);
1799 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
1800
1801 uint num_workers = _workers->active_workers();
1802 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
1803 _workers->run_task(&unlink_task);
1804 }
1805 // Release unloaded nmethods's memory.
1806 ClassUnloadingContext::context()->purge_and_free_nmethods();
1807 }
1808
1809 {
1810 ShenandoahGCPhase phase(full_gc ?
1811 ShenandoahPhaseTimings::full_gc_purge_cldg :
1812 ShenandoahPhaseTimings::degen_gc_purge_cldg);
1813 ClassLoaderDataGraph::purge(true /* at_safepoint */);
1814 }
1815 // Resize and verify metaspace
1816 MetaspaceGC::compute_new_size();
1817 DEBUG_ONLY(MetaspaceUtils::verify();)
1818 }
1819
1820 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
1821 // so they should not have forwarded oops.
1822 // However, we do need to "null" dead oops in the roots, if can not be done
1823 // in concurrent cycles.
1824 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
1825 uint num_workers = _workers->active_workers();
1826 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
1827 ShenandoahPhaseTimings::full_gc_purge_weak_par :
1828 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
1829 ShenandoahGCPhase phase(timing_phase);
1830 ShenandoahGCWorkerPhase worker_phase(timing_phase);
1831 // Cleanup weak roots
1832 if (has_forwarded_objects()) {
1833 ShenandoahForwardedIsAliveClosure is_alive;
1834 ShenandoahUpdateRefsClosure keep_alive;
1835 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
1836 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
1837 _workers->run_task(&cleaning_task);
1838 } else {
1839 ShenandoahIsAliveClosure is_alive;
1840 #ifdef ASSERT
1841 ShenandoahAssertNotForwardedClosure verify_cl;
1842 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
1843 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
1844 #else
1845 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
1846 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
1847 #endif
1848 _workers->run_task(&cleaning_task);
1849 }
1850 }
1851
1852 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
1853 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1854 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
1855 ShenandoahGCPhase phase(full_gc ?
1856 ShenandoahPhaseTimings::full_gc_purge :
1857 ShenandoahPhaseTimings::degen_gc_purge);
1858 stw_weak_refs(full_gc);
1859 stw_process_weak_roots(full_gc);
1860 stw_unload_classes(full_gc);
1861 }
1862
1863 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
1864 set_gc_state(HAS_FORWARDED, cond);
1865 }
1866
1867 void ShenandoahHeap::set_unload_classes(bool uc) {
1868 _unload_classes.set_cond(uc);
1869 }
1870
1871 bool ShenandoahHeap::unload_classes() const {
1872 return _unload_classes.is_set();
1873 }
1874
1875 address ShenandoahHeap::in_cset_fast_test_addr() {
1876 ShenandoahHeap* heap = ShenandoahHeap::heap();
1877 assert(heap->collection_set() != nullptr, "Sanity");
1878 return (address) heap->collection_set()->biased_map_address();
1879 }
1880
1881 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
1882 return Atomic::load(&_bytes_allocated_since_gc_start);
1883 }
1884
1885 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
1886 Atomic::store(&_bytes_allocated_since_gc_start, (size_t)0);
1887 }
1888
1889 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
1890 _degenerated_gc_in_progress.set_cond(in_progress);
1891 }
1892
1893 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
1894 _full_gc_in_progress.set_cond(in_progress);
1895 }
1896
1897 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
1898 assert (is_full_gc_in_progress(), "should be");
1899 _full_gc_move_in_progress.set_cond(in_progress);
1900 }
1901
1902 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
1903 set_gc_state(UPDATEREFS, in_progress);
1904 }
1905
1906 void ShenandoahHeap::register_nmethod(nmethod* nm) {
1907 ShenandoahCodeRoots::register_nmethod(nm);
1908 }
1909
1910 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
1911 ShenandoahCodeRoots::unregister_nmethod(nm);
1912 }
1913
1914 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
1915 heap_region_containing(o)->record_pin();
1916 }
1917
1918 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
1919 ShenandoahHeapRegion* r = heap_region_containing(o);
1920 assert(r != nullptr, "Sanity");
1921 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
1922 r->record_unpin();
1923 }
1924
1925 void ShenandoahHeap::sync_pinned_region_status() {
1926 ShenandoahHeapLocker locker(lock());
1927
1928 for (size_t i = 0; i < num_regions(); i++) {
1929 ShenandoahHeapRegion *r = get_region(i);
1930 if (r->is_active()) {
1931 if (r->is_pinned()) {
1932 if (r->pin_count() == 0) {
1933 r->make_unpinned();
1934 }
1935 } else {
1936 if (r->pin_count() > 0) {
1937 r->make_pinned();
1938 }
1939 }
1940 }
1941 }
1942
1943 assert_pinned_region_status();
1944 }
1945
1946 #ifdef ASSERT
1947 void ShenandoahHeap::assert_pinned_region_status() {
1948 for (size_t i = 0; i < num_regions(); i++) {
1949 ShenandoahHeapRegion* r = get_region(i);
1950 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
1951 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
1952 }
1953 }
1954 #endif
1955
1956 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
1957 return _gc_timer;
1958 }
1959
1960 void ShenandoahHeap::prepare_concurrent_roots() {
1961 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1962 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1963 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
1964 set_concurrent_weak_root_in_progress(true);
1965 if (unload_classes()) {
1966 _unloader.prepare();
1967 }
1968 }
1969
1970 void ShenandoahHeap::finish_concurrent_roots() {
1971 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1972 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1973 if (unload_classes()) {
1974 _unloader.finish();
1975 }
1976 }
1977
1978 #ifdef ASSERT
1979 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
1980 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
1981
1982 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1983 if (UseDynamicNumberOfGCThreads) {
1984 assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
1985 } else {
1986 // Use ParallelGCThreads inside safepoints
1987 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
1988 }
1989 } else {
1990 if (UseDynamicNumberOfGCThreads) {
1991 assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
1992 } else {
1993 // Use ConcGCThreads outside safepoints
1994 assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
1995 }
1996 }
1997 }
1998 #endif
1999
2000 ShenandoahVerifier* ShenandoahHeap::verifier() {
2001 guarantee(ShenandoahVerify, "Should be enabled");
2002 assert (_verifier != nullptr, "sanity");
2003 return _verifier;
2004 }
2005
2006 template<bool CONCURRENT>
2007 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2008 private:
2009 ShenandoahHeap* _heap;
2010 ShenandoahRegionIterator* _regions;
2011 public:
2012 ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2013 WorkerTask("Shenandoah Update References"),
2014 _heap(ShenandoahHeap::heap()),
2015 _regions(regions) {
2016 }
2017
2018 void work(uint worker_id) {
2019 if (CONCURRENT) {
2020 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2021 ShenandoahSuspendibleThreadSetJoiner stsj;
2022 do_work<ShenandoahConcUpdateRefsClosure>();
2023 } else {
2024 ShenandoahParallelWorkerSession worker_session(worker_id);
2025 do_work<ShenandoahSTWUpdateRefsClosure>();
2026 }
2027 }
2028
2029 private:
2030 template<class T>
2031 void do_work() {
2032 T cl;
2033 ShenandoahHeapRegion* r = _regions->next();
2034 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2035 while (r != nullptr) {
2036 HeapWord* update_watermark = r->get_update_watermark();
2037 assert (update_watermark >= r->bottom(), "sanity");
2038 if (r->is_active() && !r->is_cset()) {
2039 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2040 }
2041 if (ShenandoahPacing) {
2042 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2043 }
2044 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2045 return;
2046 }
2047 r = _regions->next();
2048 }
2049 }
2050 };
2051
2052 void ShenandoahHeap::update_heap_references(bool concurrent) {
2053 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2054
2055 if (concurrent) {
2056 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2057 workers()->run_task(&task);
2058 } else {
2059 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2060 workers()->run_task(&task);
2061 }
2062 }
2063
2064
2065 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2066 private:
2067 ShenandoahHeapLock* const _lock;
2068
2069 public:
2070 ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2071
2072 void heap_region_do(ShenandoahHeapRegion* r) {
2073 // Drop unnecessary "pinned" state from regions that does not have CP marks
2074 // anymore, as this would allow trashing them.
2075
2076 if (r->is_active()) {
2077 if (r->is_pinned()) {
2078 if (r->pin_count() == 0) {
2079 ShenandoahHeapLocker locker(_lock);
2080 r->make_unpinned();
2081 }
2082 } else {
2083 if (r->pin_count() > 0) {
2084 ShenandoahHeapLocker locker(_lock);
2085 r->make_pinned();
2086 }
2087 }
2088 }
2089 }
2090
2091 bool is_thread_safe() { return true; }
2092 };
2093
2094 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2095 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2096 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2097
2098 {
2099 ShenandoahGCPhase phase(concurrent ?
2100 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2101 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2102 ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2103 parallel_heap_region_iterate(&cl);
2104
2105 assert_pinned_region_status();
2106 }
2107
2108 {
2109 ShenandoahGCPhase phase(concurrent ?
2110 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2111 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2112 trash_cset_regions();
2113 }
2114 }
2115
2116 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2117 {
2118 ShenandoahGCPhase phase(concurrent ?
2119 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2120 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2121 ShenandoahHeapLocker locker(lock());
2122 _free_set->rebuild();
2123 }
2124 }
2125
2126 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2127 print_on(st);
2128 st->cr();
2129 print_heap_regions_on(st);
2130 }
2131
2132 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2133 size_t slice = r->index() / _bitmap_regions_per_slice;
2134
2135 size_t regions_from = _bitmap_regions_per_slice * slice;
2136 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2137 for (size_t g = regions_from; g < regions_to; g++) {
2138 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2139 if (skip_self && g == r->index()) continue;
2140 if (get_region(g)->is_committed()) {
2141 return true;
2142 }
2143 }
2144 return false;
2145 }
2146
2147 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2148 shenandoah_assert_heaplocked();
2149
2150 // Bitmaps in special regions do not need commits
2151 if (_bitmap_region_special) {
2152 return true;
2153 }
2154
2155 if (is_bitmap_slice_committed(r, true)) {
2156 // Some other region from the group is already committed, meaning the bitmap
2157 // slice is already committed, we exit right away.
2158 return true;
2159 }
2160
2161 // Commit the bitmap slice:
2162 size_t slice = r->index() / _bitmap_regions_per_slice;
2163 size_t off = _bitmap_bytes_per_slice * slice;
2164 size_t len = _bitmap_bytes_per_slice;
2165 char* start = (char*) _bitmap_region.start() + off;
2166
2167 if (!os::commit_memory(start, len, false)) {
2168 return false;
2169 }
2170
2171 if (AlwaysPreTouch) {
2172 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2173 }
2174
2175 return true;
2176 }
2177
2178 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2179 shenandoah_assert_heaplocked();
2180
2181 // Bitmaps in special regions do not need uncommits
2182 if (_bitmap_region_special) {
2183 return true;
2184 }
2185
2186 if (is_bitmap_slice_committed(r, true)) {
2187 // Some other region from the group is still committed, meaning the bitmap
2188 // slice is should stay committed, exit right away.
2189 return true;
2190 }
2191
2192 // Uncommit the bitmap slice:
2193 size_t slice = r->index() / _bitmap_regions_per_slice;
2194 size_t off = _bitmap_bytes_per_slice * slice;
2195 size_t len = _bitmap_bytes_per_slice;
2196 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2197 return false;
2198 }
2199 return true;
2200 }
2201
2202 void ShenandoahHeap::safepoint_synchronize_begin() {
2203 SuspendibleThreadSet::synchronize();
2204 }
2205
2206 void ShenandoahHeap::safepoint_synchronize_end() {
2207 SuspendibleThreadSet::desynchronize();
2208 }
2209
2210 void ShenandoahHeap::entry_uncommit(double shrink_before, size_t shrink_until) {
2211 static const char *msg = "Concurrent uncommit";
2212 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
2213 EventMark em("%s", msg);
2214
2215 op_uncommit(shrink_before, shrink_until);
2216 }
2217
2218 void ShenandoahHeap::try_inject_alloc_failure() {
2219 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2220 _inject_alloc_failure.set();
2221 os::naked_short_sleep(1);
2222 if (cancelled_gc()) {
2223 log_info(gc)("Allocation failure was successfully injected");
2224 }
2225 }
2226 }
2227
2228 bool ShenandoahHeap::should_inject_alloc_failure() {
2229 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2230 }
2231
2232 void ShenandoahHeap::initialize_serviceability() {
2233 _memory_pool = new ShenandoahMemoryPool(this);
2234 _cycle_memory_manager.add_pool(_memory_pool);
2235 _stw_memory_manager.add_pool(_memory_pool);
2236 }
2237
2238 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2239 GrowableArray<GCMemoryManager*> memory_managers(2);
2240 memory_managers.append(&_cycle_memory_manager);
2241 memory_managers.append(&_stw_memory_manager);
2242 return memory_managers;
2243 }
2244
2245 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2246 GrowableArray<MemoryPool*> memory_pools(1);
2247 memory_pools.append(_memory_pool);
2248 return memory_pools;
2249 }
2250
2251 MemoryUsage ShenandoahHeap::memory_usage() {
2252 return _memory_pool->get_memory_usage();
2253 }
2254
2255 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2256 _heap(ShenandoahHeap::heap()),
2257 _index(0) {}
2258
2259 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2260 _heap(heap),
2261 _index(0) {}
2262
2263 void ShenandoahRegionIterator::reset() {
2264 _index = 0;
2265 }
2266
2267 bool ShenandoahRegionIterator::has_next() const {
2268 return _index < _heap->num_regions();
2269 }
2270
2271 char ShenandoahHeap::gc_state() const {
2272 return _gc_state.raw_value();
2273 }
2274
2275 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2276 #ifdef ASSERT
2277 assert(_liveness_cache != nullptr, "sanity");
2278 assert(worker_id < _max_workers, "sanity");
2279 for (uint i = 0; i < num_regions(); i++) {
2280 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2281 }
2282 #endif
2283 return _liveness_cache[worker_id];
2284 }
2285
2286 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2287 assert(worker_id < _max_workers, "sanity");
2288 assert(_liveness_cache != nullptr, "sanity");
2289 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2290 for (uint i = 0; i < num_regions(); i++) {
2291 ShenandoahLiveData live = ld[i];
2292 if (live > 0) {
2293 ShenandoahHeapRegion* r = get_region(i);
2294 r->increase_live_data_gc_words(live);
2295 ld[i] = 0;
2296 }
2297 }
2298 }
2299
2300 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2301 if (is_idle()) return false;
2302
2303 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2304 // marking phase.
2305 if (is_concurrent_mark_in_progress() &&
2306 !marking_context()->allocated_after_mark_start(obj)) {
2307 return true;
2308 }
2309
2310 // Can not guarantee obj is deeply good.
2311 if (has_forwarded_objects()) {
2312 return true;
2313 }
2314
2315 return false;
2316 }