1 /*
2 * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/universe.hpp"
29
30 #include "gc/shared/gcArguments.hpp"
31 #include "gc/shared/gcTimer.hpp"
32 #include "gc/shared/gcTraceTime.inline.hpp"
33 #include "gc/shared/locationPrinter.inline.hpp"
34 #include "gc/shared/memAllocator.hpp"
35 #include "gc/shared/plab.hpp"
36 #include "gc/shared/slidingForwarding.hpp"
37 #include "gc/shared/tlab_globals.hpp"
38
39 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
40 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
41 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
42 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
43 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
44 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
45 #include "gc/shenandoah/shenandoahControlThread.hpp"
46 #include "gc/shenandoah/shenandoahFreeSet.hpp"
47 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
48 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
49 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
50 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
51 #include "gc/shenandoah/shenandoahInitLogger.hpp"
52 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
53 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
54 #include "gc/shenandoah/shenandoahMetrics.hpp"
55 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
56 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
57 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
58 #include "gc/shenandoah/shenandoahPadding.hpp"
59 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
60 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
61 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
62 #include "gc/shenandoah/shenandoahSTWMark.hpp"
63 #include "gc/shenandoah/shenandoahUtils.hpp"
64 #include "gc/shenandoah/shenandoahVerifier.hpp"
65 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
66 #include "gc/shenandoah/shenandoahVMOperations.hpp"
67 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
68 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
69 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
70 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
71 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
72 #if INCLUDE_JFR
73 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
74 #endif
75
76 #include "classfile/systemDictionary.hpp"
77 #include "code/codeCache.hpp"
78 #include "memory/classLoaderMetaspace.hpp"
79 #include "memory/metaspaceUtils.hpp"
80 #include "oops/compressedOops.inline.hpp"
81 #include "prims/jvmtiTagMap.hpp"
82 #include "runtime/atomic.hpp"
83 #include "runtime/globals.hpp"
84 #include "runtime/interfaceSupport.inline.hpp"
85 #include "runtime/java.hpp"
86 #include "runtime/orderAccess.hpp"
87 #include "runtime/safepointMechanism.hpp"
88 #include "runtime/vmThread.hpp"
89 #include "services/mallocTracker.hpp"
90 #include "services/memTracker.hpp"
91 #include "utilities/events.hpp"
92 #include "utilities/powerOfTwo.hpp"
93
94 class ShenandoahPretouchHeapTask : public WorkerTask {
95 private:
96 ShenandoahRegionIterator _regions;
97 const size_t _page_size;
98 public:
99 ShenandoahPretouchHeapTask(size_t page_size) :
100 WorkerTask("Shenandoah Pretouch Heap"),
101 _page_size(page_size) {}
102
103 virtual void work(uint worker_id) {
104 ShenandoahHeapRegion* r = _regions.next();
105 while (r != nullptr) {
106 if (r->is_committed()) {
107 os::pretouch_memory(r->bottom(), r->end(), _page_size);
108 }
109 r = _regions.next();
110 }
111 }
112 };
113
114 class ShenandoahPretouchBitmapTask : public WorkerTask {
115 private:
116 ShenandoahRegionIterator _regions;
117 char* _bitmap_base;
118 const size_t _bitmap_size;
119 const size_t _page_size;
120 public:
121 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
122 WorkerTask("Shenandoah Pretouch Bitmap"),
123 _bitmap_base(bitmap_base),
124 _bitmap_size(bitmap_size),
125 _page_size(page_size) {}
126
127 virtual void work(uint worker_id) {
128 ShenandoahHeapRegion* r = _regions.next();
129 while (r != nullptr) {
130 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
131 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
132 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
133
134 if (r->is_committed()) {
135 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
136 }
137
138 r = _regions.next();
139 }
140 }
141 };
142
143 jint ShenandoahHeap::initialize() {
144 //
145 // Figure out heap sizing
146 //
147
148 size_t init_byte_size = InitialHeapSize;
149 size_t min_byte_size = MinHeapSize;
150 size_t max_byte_size = MaxHeapSize;
151 size_t heap_alignment = HeapAlignment;
152
153 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
154
155 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
156 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
157
158 _num_regions = ShenandoahHeapRegion::region_count();
159 assert(_num_regions == (max_byte_size / reg_size_bytes),
160 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
161 _num_regions, max_byte_size, reg_size_bytes);
162
163 // Now we know the number of regions, initialize the heuristics.
164 initialize_heuristics();
165
166 size_t num_committed_regions = init_byte_size / reg_size_bytes;
167 num_committed_regions = MIN2(num_committed_regions, _num_regions);
168 assert(num_committed_regions <= _num_regions, "sanity");
169 _initial_size = num_committed_regions * reg_size_bytes;
170
171 size_t num_min_regions = min_byte_size / reg_size_bytes;
172 num_min_regions = MIN2(num_min_regions, _num_regions);
173 assert(num_min_regions <= _num_regions, "sanity");
174 _minimum_size = num_min_regions * reg_size_bytes;
175
176 // Default to max heap size.
177 _soft_max_size = _num_regions * reg_size_bytes;
178
179 _committed = _initial_size;
180
181 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
182 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
183 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
184
185 //
186 // Reserve and commit memory for heap
187 //
188
189 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
190 initialize_reserved_region(heap_rs);
191 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
192 _heap_region_special = heap_rs.special();
193
194 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
195 "Misaligned heap: " PTR_FORMAT, p2i(base()));
196
197 #if SHENANDOAH_OPTIMIZED_MARKTASK
198 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
199 // Fail if we ever attempt to address more than we can.
200 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
201 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
202 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
203 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
204 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
205 vm_exit_during_initialization("Fatal Error", buf);
206 }
207 #endif
208
209 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
210 if (!_heap_region_special) {
211 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
212 "Cannot commit heap memory");
213 }
214
215 //
216 // Reserve and commit memory for bitmap(s)
217 //
218
219 _bitmap_size = ShenandoahMarkBitMap::compute_size(heap_rs.size());
220 _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
221
222 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
223
224 guarantee(bitmap_bytes_per_region != 0,
225 "Bitmap bytes per region should not be zero");
226 guarantee(is_power_of_2(bitmap_bytes_per_region),
227 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
228
229 if (bitmap_page_size > bitmap_bytes_per_region) {
230 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
231 _bitmap_bytes_per_slice = bitmap_page_size;
232 } else {
233 _bitmap_regions_per_slice = 1;
234 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
235 }
236
237 guarantee(_bitmap_regions_per_slice >= 1,
238 "Should have at least one region per slice: " SIZE_FORMAT,
239 _bitmap_regions_per_slice);
240
241 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
242 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
243 _bitmap_bytes_per_slice, bitmap_page_size);
244
245 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
246 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
247 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
248 _bitmap_region_special = bitmap.special();
249
250 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
251 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
252 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
253 if (!_bitmap_region_special) {
254 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
255 "Cannot commit bitmap memory");
256 }
257
258 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions, _max_workers);
259
260 if (ShenandoahVerify) {
261 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
262 if (!verify_bitmap.special()) {
263 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
264 "Cannot commit verification bitmap memory");
265 }
266 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
267 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
268 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
269 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
270 }
271
272 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
273 ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
274 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
275 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
276 _aux_bitmap_region_special = aux_bitmap.special();
277 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
278
279 //
280 // Create regions and region sets
281 //
282 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
283 size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
284 region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
285
286 ReservedSpace region_storage(region_storage_size, region_page_size);
287 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
288 if (!region_storage.special()) {
289 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
290 "Cannot commit region memory");
291 }
292
293 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
294 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
295 // If not successful, bite a bullet and allocate at whatever address.
296 {
297 size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
298 size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
299
300 uintptr_t min = round_up_power_of_2(cset_align);
301 uintptr_t max = (1u << 30u);
302
303 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
304 char* req_addr = (char*)addr;
305 assert(is_aligned(req_addr, cset_align), "Should be aligned");
306 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size(), req_addr);
307 if (cset_rs.is_reserved()) {
308 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
309 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
310 break;
311 }
312 }
313
314 if (_collection_set == nullptr) {
315 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size());
316 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
317 }
318 }
319
320 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
321 _free_set = new ShenandoahFreeSet(this, _num_regions);
322
323 {
324 ShenandoahHeapLocker locker(lock());
325
326 for (size_t i = 0; i < _num_regions; i++) {
327 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
328 bool is_committed = i < num_committed_regions;
329 void* loc = region_storage.base() + i * region_align;
330
331 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
332 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
333
334 _marking_context->initialize_top_at_mark_start(r);
335 _regions[i] = r;
336 assert(!collection_set()->is_in(i), "New region should not be in collection set");
337 }
338
339 // Initialize to complete
340 _marking_context->mark_complete();
341
342 _free_set->rebuild();
343 }
344
345 if (AlwaysPreTouch) {
346 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
347 // before initialize() below zeroes it with initializing thread. For any given region,
348 // we touch the region and the corresponding bitmaps from the same thread.
349 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
350
351 _pretouch_heap_page_size = heap_page_size;
352 _pretouch_bitmap_page_size = bitmap_page_size;
353
354 #ifdef LINUX
355 // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
356 // pages. But, the kernel needs to know that every small page is used, in order to coalesce
357 // them into huge one. Therefore, we need to pretouch with smaller pages.
358 if (UseTransparentHugePages) {
359 _pretouch_heap_page_size = (size_t)os::vm_page_size();
360 _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
361 }
362 #endif
363
364 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
365 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
366
367 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
368 _workers->run_task(&bcl);
369
370 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
371 _workers->run_task(&hcl);
372 }
373
374 //
375 // Initialize the rest of GC subsystems
376 //
377
378 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
379 for (uint worker = 0; worker < _max_workers; worker++) {
380 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
381 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
382 }
383
384 // There should probably be Shenandoah-specific options for these,
385 // just as there are G1-specific options.
386 {
387 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
388 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
389 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
390 }
391
392 _monitoring_support = new ShenandoahMonitoringSupport(this);
393 _phase_timings = new ShenandoahPhaseTimings(max_workers());
394 ShenandoahCodeRoots::initialize();
395
396 if (ShenandoahPacing) {
397 _pacer = new ShenandoahPacer(this);
398 _pacer->setup_for_idle();
399 } else {
400 _pacer = nullptr;
401 }
402
403 _control_thread = new ShenandoahControlThread();
404
405 ShenandoahInitLogger::print();
406
407 SlidingForwarding::initialize(_heap_region, ShenandoahHeapRegion::region_size_words());
408
409 return JNI_OK;
410 }
411
412 void ShenandoahHeap::initialize_mode() {
413 if (ShenandoahGCMode != nullptr) {
414 if (strcmp(ShenandoahGCMode, "satb") == 0) {
415 _gc_mode = new ShenandoahSATBMode();
416 } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
417 _gc_mode = new ShenandoahIUMode();
418 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
419 _gc_mode = new ShenandoahPassiveMode();
420 } else {
421 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
422 }
423 } else {
424 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
425 }
426 _gc_mode->initialize_flags();
427 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
428 vm_exit_during_initialization(
429 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
430 _gc_mode->name()));
431 }
432 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
433 vm_exit_during_initialization(
434 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
435 _gc_mode->name()));
436 }
437 }
438
439 void ShenandoahHeap::initialize_heuristics() {
440 assert(_gc_mode != nullptr, "Must be initialized");
441 _heuristics = _gc_mode->initialize_heuristics();
442
443 if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
444 vm_exit_during_initialization(
445 err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
446 _heuristics->name()));
447 }
448 if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
449 vm_exit_during_initialization(
450 err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
451 _heuristics->name()));
452 }
453 }
454
455 #ifdef _MSC_VER
456 #pragma warning( push )
457 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
458 #endif
459
460 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
461 CollectedHeap(),
462 _initial_size(0),
463 _used(0),
464 _committed(0),
465 _bytes_allocated_since_gc_start(0),
466 _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
467 _workers(nullptr),
468 _safepoint_workers(nullptr),
469 _heap_region_special(false),
470 _num_regions(0),
471 _regions(nullptr),
472 _update_refs_iterator(this),
473 _control_thread(nullptr),
474 _shenandoah_policy(policy),
475 _gc_mode(nullptr),
476 _heuristics(nullptr),
477 _free_set(nullptr),
478 _pacer(nullptr),
479 _verifier(nullptr),
480 _phase_timings(nullptr),
481 _monitoring_support(nullptr),
482 _memory_pool(nullptr),
483 _stw_memory_manager("Shenandoah Pauses"),
484 _cycle_memory_manager("Shenandoah Cycles"),
485 _gc_timer(new ConcurrentGCTimer()),
486 _soft_ref_policy(),
487 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
488 _ref_processor(new ShenandoahReferenceProcessor(MAX2(_max_workers, 1U))),
489 _marking_context(nullptr),
490 _bitmap_size(0),
491 _bitmap_regions_per_slice(0),
492 _bitmap_bytes_per_slice(0),
493 _bitmap_region_special(false),
494 _aux_bitmap_region_special(false),
495 _liveness_cache(nullptr),
496 _collection_set(nullptr)
497 {
498 // Initialize GC mode early, so we can adjust barrier support
499 initialize_mode();
500 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
501
502 _max_workers = MAX2(_max_workers, 1U);
503 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
504 if (_workers == nullptr) {
505 vm_exit_during_initialization("Failed necessary allocation.");
506 } else {
507 _workers->initialize_workers();
508 }
509
510 if (ParallelGCThreads > 1) {
511 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread",
512 ParallelGCThreads);
513 _safepoint_workers->initialize_workers();
514 }
515 }
516
517 #ifdef _MSC_VER
518 #pragma warning( pop )
519 #endif
520
521 class ShenandoahResetBitmapTask : public WorkerTask {
522 private:
523 ShenandoahRegionIterator _regions;
524
525 public:
526 ShenandoahResetBitmapTask() :
527 WorkerTask("Shenandoah Reset Bitmap") {}
528
529 void work(uint worker_id) {
530 ShenandoahHeapRegion* region = _regions.next();
531 ShenandoahHeap* heap = ShenandoahHeap::heap();
532 ShenandoahMarkingContext* const ctx = heap->marking_context();
533 while (region != nullptr) {
534 if (heap->is_bitmap_slice_committed(region)) {
535 ctx->clear_bitmap(region);
536 }
537 region = _regions.next();
538 }
539 }
540 };
541
542 void ShenandoahHeap::reset_mark_bitmap() {
543 assert_gc_workers(_workers->active_workers());
544 mark_incomplete_marking_context();
545
546 ShenandoahResetBitmapTask task;
547 _workers->run_task(&task);
548 }
549
550 void ShenandoahHeap::print_on(outputStream* st) const {
551 st->print_cr("Shenandoah Heap");
552 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
553 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
554 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
555 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
556 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
557 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
558 num_regions(),
559 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
560 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
561
562 st->print("Status: ");
563 if (has_forwarded_objects()) st->print("has forwarded objects, ");
564 if (is_concurrent_mark_in_progress()) st->print("marking, ");
565 if (is_evacuation_in_progress()) st->print("evacuating, ");
566 if (is_update_refs_in_progress()) st->print("updating refs, ");
567 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
568 if (is_full_gc_in_progress()) st->print("full gc, ");
569 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
570 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
571 if (is_concurrent_strong_root_in_progress() &&
572 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
573
574 if (cancelled_gc()) {
575 st->print("cancelled");
576 } else {
577 st->print("not cancelled");
578 }
579 st->cr();
580
581 st->print_cr("Reserved region:");
582 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
583 p2i(reserved_region().start()),
584 p2i(reserved_region().end()));
585
586 ShenandoahCollectionSet* cset = collection_set();
587 st->print_cr("Collection set:");
588 if (cset != nullptr) {
589 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
590 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
591 } else {
592 st->print_cr(" (null)");
593 }
594
595 st->cr();
596 MetaspaceUtils::print_on(st);
597
598 if (Verbose) {
599 st->cr();
600 print_heap_regions_on(st);
601 }
602 }
603
604 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
605 public:
606 void do_thread(Thread* thread) {
607 assert(thread != nullptr, "Sanity");
608 assert(thread->is_Worker_thread(), "Only worker thread expected");
609 ShenandoahThreadLocalData::initialize_gclab(thread);
610 }
611 };
612
613 void ShenandoahHeap::post_initialize() {
614 CollectedHeap::post_initialize();
615 MutexLocker ml(Threads_lock);
616
617 ShenandoahInitWorkerGCLABClosure init_gclabs;
618 _workers->threads_do(&init_gclabs);
619
620 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
621 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
622 _workers->set_initialize_gclab();
623 if (_safepoint_workers != nullptr) {
624 _safepoint_workers->threads_do(&init_gclabs);
625 _safepoint_workers->set_initialize_gclab();
626 }
627
628 _heuristics->initialize();
629
630 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
631 }
632
633 size_t ShenandoahHeap::used() const {
634 return Atomic::load(&_used);
635 }
636
637 size_t ShenandoahHeap::committed() const {
638 return Atomic::load(&_committed);
639 }
640
641 void ShenandoahHeap::increase_committed(size_t bytes) {
642 shenandoah_assert_heaplocked_or_safepoint();
643 _committed += bytes;
644 }
645
646 void ShenandoahHeap::decrease_committed(size_t bytes) {
647 shenandoah_assert_heaplocked_or_safepoint();
648 _committed -= bytes;
649 }
650
651 void ShenandoahHeap::increase_used(size_t bytes) {
652 Atomic::add(&_used, bytes, memory_order_relaxed);
653 }
654
655 void ShenandoahHeap::set_used(size_t bytes) {
656 Atomic::store(&_used, bytes);
657 }
658
659 void ShenandoahHeap::decrease_used(size_t bytes) {
660 assert(used() >= bytes, "never decrease heap size by more than we've left");
661 Atomic::sub(&_used, bytes, memory_order_relaxed);
662 }
663
664 void ShenandoahHeap::increase_allocated(size_t bytes) {
665 Atomic::add(&_bytes_allocated_since_gc_start, bytes, memory_order_relaxed);
666 }
667
668 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
669 size_t bytes = words * HeapWordSize;
670 if (!waste) {
671 increase_used(bytes);
672 }
673 increase_allocated(bytes);
674 if (ShenandoahPacing) {
675 control_thread()->pacing_notify_alloc(words);
676 if (waste) {
677 pacer()->claim_for_alloc(words, true);
678 }
679 }
680 }
681
682 size_t ShenandoahHeap::capacity() const {
683 return committed();
684 }
685
686 size_t ShenandoahHeap::max_capacity() const {
687 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
688 }
689
690 size_t ShenandoahHeap::soft_max_capacity() const {
691 size_t v = Atomic::load(&_soft_max_size);
692 assert(min_capacity() <= v && v <= max_capacity(),
693 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
694 min_capacity(), v, max_capacity());
695 return v;
696 }
697
698 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
699 assert(min_capacity() <= v && v <= max_capacity(),
700 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
701 min_capacity(), v, max_capacity());
702 Atomic::store(&_soft_max_size, v);
703 }
704
705 size_t ShenandoahHeap::min_capacity() const {
706 return _minimum_size;
707 }
708
709 size_t ShenandoahHeap::initial_capacity() const {
710 return _initial_size;
711 }
712
713 bool ShenandoahHeap::is_in(const void* p) const {
714 HeapWord* heap_base = (HeapWord*) base();
715 HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
716 return p >= heap_base && p < last_region_end;
717 }
718
719 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
720 assert (ShenandoahUncommit, "should be enabled");
721
722 // Application allocates from the beginning of the heap, and GC allocates at
723 // the end of it. It is more efficient to uncommit from the end, so that applications
724 // could enjoy the near committed regions. GC allocations are much less frequent,
725 // and therefore can accept the committing costs.
726
727 size_t count = 0;
728 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
729 ShenandoahHeapRegion* r = get_region(i - 1);
730 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
731 ShenandoahHeapLocker locker(lock());
732 if (r->is_empty_committed()) {
733 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
734 break;
735 }
736
737 r->make_uncommitted();
738 count++;
739 }
740 }
741 SpinPause(); // allow allocators to take the lock
742 }
743
744 if (count > 0) {
745 control_thread()->notify_heap_changed();
746 }
747 }
748
749 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
750 // New object should fit the GCLAB size
751 size_t min_size = MAX2(size, PLAB::min_size());
752
753 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
754 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
755 new_size = MIN2(new_size, PLAB::max_size());
756 new_size = MAX2(new_size, PLAB::min_size());
757
758 // Record new heuristic value even if we take any shortcut. This captures
759 // the case when moderately-sized objects always take a shortcut. At some point,
760 // heuristics should catch up with them.
761 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
762
763 if (new_size < size) {
764 // New size still does not fit the object. Fall back to shared allocation.
765 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
766 return nullptr;
767 }
768
769 // Retire current GCLAB, and allocate a new one.
770 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
771 gclab->retire();
772
773 size_t actual_size = 0;
774 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
775 if (gclab_buf == nullptr) {
776 return nullptr;
777 }
778
779 assert (size <= actual_size, "allocation should fit");
780
781 if (ZeroTLAB) {
782 // ..and clear it.
783 Copy::zero_to_words(gclab_buf, actual_size);
784 } else {
785 // ...and zap just allocated object.
786 #ifdef ASSERT
787 // Skip mangling the space corresponding to the object header to
788 // ensure that the returned space is not considered parsable by
789 // any concurrent GC thread.
790 size_t hdr_size = oopDesc::header_size();
791 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
792 #endif // ASSERT
793 }
794 gclab->set_buf(gclab_buf, actual_size);
795 return gclab->allocate(size);
796 }
797
798 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
799 size_t requested_size,
800 size_t* actual_size) {
801 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
802 HeapWord* res = allocate_memory(req);
803 if (res != nullptr) {
804 *actual_size = req.actual_size();
805 } else {
806 *actual_size = 0;
807 }
808 return res;
809 }
810
811 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
812 size_t word_size,
813 size_t* actual_size) {
814 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
815 HeapWord* res = allocate_memory(req);
816 if (res != nullptr) {
817 *actual_size = req.actual_size();
818 } else {
819 *actual_size = 0;
820 }
821 return res;
822 }
823
824 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
825 intptr_t pacer_epoch = 0;
826 bool in_new_region = false;
827 HeapWord* result = nullptr;
828
829 if (req.is_mutator_alloc()) {
830 if (ShenandoahPacing) {
831 pacer()->pace_for_alloc(req.size());
832 pacer_epoch = pacer()->epoch();
833 }
834
835 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
836 result = allocate_memory_under_lock(req, in_new_region);
837 }
838
839 // Allocation failed, block until control thread reacted, then retry allocation.
840 //
841 // It might happen that one of the threads requesting allocation would unblock
842 // way later after GC happened, only to fail the second allocation, because
843 // other threads have already depleted the free storage. In this case, a better
844 // strategy is to try again, as long as GC makes progress.
845 //
846 // Then, we need to make sure the allocation was retried after at least one
847 // Full GC, which means we want to try more than ShenandoahFullGCThreshold times.
848
849 size_t tries = 0;
850
851 while (result == nullptr && _progress_last_gc.is_set()) {
852 tries++;
853 control_thread()->handle_alloc_failure(req);
854 result = allocate_memory_under_lock(req, in_new_region);
855 }
856
857 while (result == nullptr && tries <= ShenandoahFullGCThreshold) {
858 tries++;
859 control_thread()->handle_alloc_failure(req);
860 result = allocate_memory_under_lock(req, in_new_region);
861 }
862
863 } else {
864 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
865 result = allocate_memory_under_lock(req, in_new_region);
866 // Do not call handle_alloc_failure() here, because we cannot block.
867 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
868 }
869
870 if (in_new_region) {
871 control_thread()->notify_heap_changed();
872 }
873
874 if (result != nullptr) {
875 size_t requested = req.size();
876 size_t actual = req.actual_size();
877
878 assert (req.is_lab_alloc() || (requested == actual),
879 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
880 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
881
882 if (req.is_mutator_alloc()) {
883 notify_mutator_alloc_words(actual, false);
884
885 // If we requested more than we were granted, give the rest back to pacer.
886 // This only matters if we are in the same pacing epoch: do not try to unpace
887 // over the budget for the other phase.
888 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
889 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
890 }
891 } else {
892 increase_used(actual*HeapWordSize);
893 }
894 }
895
896 return result;
897 }
898
899 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
900 ShenandoahHeapLocker locker(lock());
901 return _free_set->allocate(req, in_new_region);
902 }
903
904 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
905 bool* gc_overhead_limit_was_exceeded) {
906 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
907 return allocate_memory(req);
908 }
909
910 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
911 size_t size,
912 Metaspace::MetadataType mdtype) {
913 MetaWord* result;
914
915 // Inform metaspace OOM to GC heuristics if class unloading is possible.
916 if (heuristics()->can_unload_classes()) {
917 ShenandoahHeuristics* h = heuristics();
918 h->record_metaspace_oom();
919 }
920
921 // Expand and retry allocation
922 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
923 if (result != nullptr) {
924 return result;
925 }
926
927 // Start full GC
928 collect(GCCause::_metadata_GC_clear_soft_refs);
929
930 // Retry allocation
931 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
932 if (result != nullptr) {
933 return result;
934 }
935
936 // Expand and retry allocation
937 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
938 if (result != nullptr) {
939 return result;
940 }
941
942 // Out of memory
943 return nullptr;
944 }
945
946 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
947 private:
948 ShenandoahHeap* const _heap;
949 Thread* const _thread;
950 public:
951 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
952 _heap(heap), _thread(Thread::current()) {}
953
954 void do_object(oop p) {
955 shenandoah_assert_marked(nullptr, p);
956 if (!p->is_forwarded()) {
957 _heap->evacuate_object(p, _thread);
958 }
959 }
960 };
961
962 class ShenandoahEvacuationTask : public WorkerTask {
963 private:
964 ShenandoahHeap* const _sh;
965 ShenandoahCollectionSet* const _cs;
966 bool _concurrent;
967 public:
968 ShenandoahEvacuationTask(ShenandoahHeap* sh,
969 ShenandoahCollectionSet* cs,
970 bool concurrent) :
971 WorkerTask("Shenandoah Evacuation"),
972 _sh(sh),
973 _cs(cs),
974 _concurrent(concurrent)
975 {}
976
977 void work(uint worker_id) {
978 if (_concurrent) {
979 ShenandoahConcurrentWorkerSession worker_session(worker_id);
980 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
981 ShenandoahEvacOOMScope oom_evac_scope;
982 do_work();
983 } else {
984 ShenandoahParallelWorkerSession worker_session(worker_id);
985 ShenandoahEvacOOMScope oom_evac_scope;
986 do_work();
987 }
988 }
989
990 private:
991 void do_work() {
992 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
993 ShenandoahHeapRegion* r;
994 while ((r =_cs->claim_next()) != nullptr) {
995 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
996 _sh->marked_object_iterate(r, &cl);
997
998 if (ShenandoahPacing) {
999 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1000 }
1001
1002 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1003 break;
1004 }
1005 }
1006 }
1007 };
1008
1009 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1010 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1011 workers()->run_task(&task);
1012 }
1013
1014 void ShenandoahHeap::trash_cset_regions() {
1015 ShenandoahHeapLocker locker(lock());
1016
1017 ShenandoahCollectionSet* set = collection_set();
1018 ShenandoahHeapRegion* r;
1019 set->clear_current_index();
1020 while ((r = set->next()) != nullptr) {
1021 r->make_trash();
1022 }
1023 collection_set()->clear();
1024 }
1025
1026 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1027 st->print_cr("Heap Regions:");
1028 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1029 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1030 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1031 st->print_cr("UWM=update watermark, U=used");
1032 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1033 st->print_cr("S=shared allocs, L=live data");
1034 st->print_cr("CP=critical pins");
1035
1036 for (size_t i = 0; i < num_regions(); i++) {
1037 get_region(i)->print_on(st);
1038 }
1039 }
1040
1041 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1042 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1043
1044 oop humongous_obj = cast_to_oop(start->bottom());
1045 size_t size = humongous_obj->size();
1046 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1047 size_t index = start->index() + required_regions - 1;
1048
1049 assert(!start->has_live(), "liveness must be zero");
1050
1051 for(size_t i = 0; i < required_regions; i++) {
1052 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1053 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1054 ShenandoahHeapRegion* region = get_region(index --);
1055
1056 assert(region->is_humongous(), "expect correct humongous start or continuation");
1057 assert(!region->is_cset(), "Humongous region should not be in collection set");
1058
1059 region->make_trash_immediate();
1060 }
1061 }
1062
1063 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1064 public:
1065 ShenandoahCheckCleanGCLABClosure() {}
1066 void do_thread(Thread* thread) {
1067 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1068 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1069 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1070 }
1071 };
1072
1073 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1074 private:
1075 bool const _resize;
1076 public:
1077 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1078 void do_thread(Thread* thread) {
1079 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1080 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1081 gclab->retire();
1082 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1083 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1084 }
1085 }
1086 };
1087
1088 void ShenandoahHeap::labs_make_parsable() {
1089 assert(UseTLAB, "Only call with UseTLAB");
1090
1091 ShenandoahRetireGCLABClosure cl(false);
1092
1093 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1094 ThreadLocalAllocBuffer& tlab = t->tlab();
1095 tlab.make_parsable();
1096 cl.do_thread(t);
1097 }
1098
1099 workers()->threads_do(&cl);
1100 }
1101
1102 void ShenandoahHeap::tlabs_retire(bool resize) {
1103 assert(UseTLAB, "Only call with UseTLAB");
1104 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1105
1106 ThreadLocalAllocStats stats;
1107
1108 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1109 ThreadLocalAllocBuffer& tlab = t->tlab();
1110 tlab.retire(&stats);
1111 if (resize) {
1112 tlab.resize();
1113 }
1114 }
1115
1116 stats.publish();
1117
1118 #ifdef ASSERT
1119 ShenandoahCheckCleanGCLABClosure cl;
1120 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1121 cl.do_thread(t);
1122 }
1123 workers()->threads_do(&cl);
1124 #endif
1125 }
1126
1127 void ShenandoahHeap::gclabs_retire(bool resize) {
1128 assert(UseTLAB, "Only call with UseTLAB");
1129 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1130
1131 ShenandoahRetireGCLABClosure cl(resize);
1132 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1133 cl.do_thread(t);
1134 }
1135 workers()->threads_do(&cl);
1136
1137 if (safepoint_workers() != nullptr) {
1138 safepoint_workers()->threads_do(&cl);
1139 }
1140 }
1141
1142 // Returns size in bytes
1143 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1144 if (ShenandoahElasticTLAB) {
1145 // With Elastic TLABs, return the max allowed size, and let the allocation path
1146 // figure out the safe size for current allocation.
1147 return ShenandoahHeapRegion::max_tlab_size_bytes();
1148 } else {
1149 return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes());
1150 }
1151 }
1152
1153 size_t ShenandoahHeap::max_tlab_size() const {
1154 // Returns size in words
1155 return ShenandoahHeapRegion::max_tlab_size_words();
1156 }
1157
1158 void ShenandoahHeap::collect(GCCause::Cause cause) {
1159 control_thread()->request_gc(cause);
1160 }
1161
1162 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1163 //assert(false, "Shouldn't need to do full collections");
1164 }
1165
1166 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1167 ShenandoahHeapRegion* r = heap_region_containing(addr);
1168 if (r != nullptr) {
1169 return r->block_start(addr);
1170 }
1171 return nullptr;
1172 }
1173
1174 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1175 ShenandoahHeapRegion* r = heap_region_containing(addr);
1176 return r->block_is_obj(addr);
1177 }
1178
1179 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1180 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1181 }
1182
1183 void ShenandoahHeap::prepare_for_verify() {
1184 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1185 labs_make_parsable();
1186 }
1187 }
1188
1189 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1190 tcl->do_thread(_control_thread);
1191 workers()->threads_do(tcl);
1192 if (_safepoint_workers != nullptr) {
1193 _safepoint_workers->threads_do(tcl);
1194 }
1195 }
1196
1197 void ShenandoahHeap::print_tracing_info() const {
1198 LogTarget(Info, gc, stats) lt;
1199 if (lt.is_enabled()) {
1200 ResourceMark rm;
1201 LogStream ls(lt);
1202
1203 phase_timings()->print_global_on(&ls);
1204
1205 ls.cr();
1206 ls.cr();
1207
1208 shenandoah_policy()->print_gc_stats(&ls);
1209
1210 ls.cr();
1211 ls.cr();
1212 }
1213 }
1214
1215 void ShenandoahHeap::verify(VerifyOption vo) {
1216 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1217 if (ShenandoahVerify) {
1218 verifier()->verify_generic(vo);
1219 } else {
1220 // TODO: Consider allocating verification bitmaps on demand,
1221 // and turn this on unconditionally.
1222 }
1223 }
1224 }
1225 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1226 return _free_set->capacity();
1227 }
1228
1229 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1230 private:
1231 MarkBitMap* _bitmap;
1232 ShenandoahScanObjectStack* _oop_stack;
1233 ShenandoahHeap* const _heap;
1234 ShenandoahMarkingContext* const _marking_context;
1235
1236 template <class T>
1237 void do_oop_work(T* p) {
1238 T o = RawAccess<>::oop_load(p);
1239 if (!CompressedOops::is_null(o)) {
1240 oop obj = CompressedOops::decode_not_null(o);
1241 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1242 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1243 return;
1244 }
1245 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1246
1247 assert(oopDesc::is_oop(obj), "must be a valid oop");
1248 if (!_bitmap->is_marked(obj)) {
1249 _bitmap->mark(obj);
1250 _oop_stack->push(obj);
1251 }
1252 }
1253 }
1254 public:
1255 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1256 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1257 _marking_context(_heap->marking_context()) {}
1258 void do_oop(oop* p) { do_oop_work(p); }
1259 void do_oop(narrowOop* p) { do_oop_work(p); }
1260 };
1261
1262 /*
1263 * This is public API, used in preparation of object_iterate().
1264 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1265 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1266 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1267 */
1268 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1269 // No-op.
1270 }
1271
1272 /*
1273 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1274 *
1275 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1276 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1277 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1278 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1279 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1280 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1281 * wiped the bitmap in preparation for next marking).
1282 *
1283 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1284 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1285 * is allowed to report dead objects, but is not required to do so.
1286 */
1287 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1288 // Reset bitmap
1289 if (!prepare_aux_bitmap_for_iteration())
1290 return;
1291
1292 ShenandoahScanObjectStack oop_stack;
1293 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1294 // Seed the stack with root scan
1295 scan_roots_for_iteration(&oop_stack, &oops);
1296
1297 // Work through the oop stack to traverse heap
1298 while (! oop_stack.is_empty()) {
1299 oop obj = oop_stack.pop();
1300 assert(oopDesc::is_oop(obj), "must be a valid oop");
1301 cl->do_object(obj);
1302 obj->oop_iterate(&oops);
1303 }
1304
1305 assert(oop_stack.is_empty(), "should be empty");
1306 // Reclaim bitmap
1307 reclaim_aux_bitmap_for_iteration();
1308 }
1309
1310 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1311 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1312
1313 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1314 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1315 return false;
1316 }
1317 // Reset bitmap
1318 _aux_bit_map.clear();
1319 return true;
1320 }
1321
1322 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1323 // Process GC roots according to current GC cycle
1324 // This populates the work stack with initial objects
1325 // It is important to relinquish the associated locks before diving
1326 // into heap dumper
1327 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1328 ShenandoahHeapIterationRootScanner rp(n_workers);
1329 rp.roots_do(oops);
1330 }
1331
1332 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1333 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1334 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1335 }
1336 }
1337
1338 // Closure for parallelly iterate objects
1339 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1340 private:
1341 MarkBitMap* _bitmap;
1342 ShenandoahObjToScanQueue* _queue;
1343 ShenandoahHeap* const _heap;
1344 ShenandoahMarkingContext* const _marking_context;
1345
1346 template <class T>
1347 void do_oop_work(T* p) {
1348 T o = RawAccess<>::oop_load(p);
1349 if (!CompressedOops::is_null(o)) {
1350 oop obj = CompressedOops::decode_not_null(o);
1351 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1352 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1353 return;
1354 }
1355 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1356
1357 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1358 if (_bitmap->par_mark(obj)) {
1359 _queue->push(ShenandoahMarkTask(obj));
1360 }
1361 }
1362 }
1363 public:
1364 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1365 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1366 _marking_context(_heap->marking_context()) {}
1367 void do_oop(oop* p) { do_oop_work(p); }
1368 void do_oop(narrowOop* p) { do_oop_work(p); }
1369 };
1370
1371 // Object iterator for parallel heap iteraion.
1372 // The root scanning phase happenes in construction as a preparation of
1373 // parallel marking queues.
1374 // Every worker processes it's own marking queue. work-stealing is used
1375 // to balance workload.
1376 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1377 private:
1378 uint _num_workers;
1379 bool _init_ready;
1380 MarkBitMap* _aux_bit_map;
1381 ShenandoahHeap* _heap;
1382 ShenandoahScanObjectStack _roots_stack; // global roots stack
1383 ShenandoahObjToScanQueueSet* _task_queues;
1384 public:
1385 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1386 _num_workers(num_workers),
1387 _init_ready(false),
1388 _aux_bit_map(bitmap),
1389 _heap(ShenandoahHeap::heap()) {
1390 // Initialize bitmap
1391 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1392 if (!_init_ready) {
1393 return;
1394 }
1395
1396 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1397 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1398
1399 _init_ready = prepare_worker_queues();
1400 }
1401
1402 ~ShenandoahParallelObjectIterator() {
1403 // Reclaim bitmap
1404 _heap->reclaim_aux_bitmap_for_iteration();
1405 // Reclaim queue for workers
1406 if (_task_queues!= nullptr) {
1407 for (uint i = 0; i < _num_workers; ++i) {
1408 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1409 if (q != nullptr) {
1410 delete q;
1411 _task_queues->register_queue(i, nullptr);
1412 }
1413 }
1414 delete _task_queues;
1415 _task_queues = nullptr;
1416 }
1417 }
1418
1419 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1420 if (_init_ready) {
1421 object_iterate_parallel(cl, worker_id, _task_queues);
1422 }
1423 }
1424
1425 private:
1426 // Divide global root_stack into worker queues
1427 bool prepare_worker_queues() {
1428 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1429 // Initialize queues for every workers
1430 for (uint i = 0; i < _num_workers; ++i) {
1431 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1432 _task_queues->register_queue(i, task_queue);
1433 }
1434 // Divide roots among the workers. Assume that object referencing distribution
1435 // is related with root kind, use round-robin to make every worker have same chance
1436 // to process every kind of roots
1437 size_t roots_num = _roots_stack.size();
1438 if (roots_num == 0) {
1439 // No work to do
1440 return false;
1441 }
1442
1443 for (uint j = 0; j < roots_num; j++) {
1444 uint stack_id = j % _num_workers;
1445 oop obj = _roots_stack.pop();
1446 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1447 }
1448 return true;
1449 }
1450
1451 void object_iterate_parallel(ObjectClosure* cl,
1452 uint worker_id,
1453 ShenandoahObjToScanQueueSet* queue_set) {
1454 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1455 assert(queue_set != nullptr, "task queue must not be null");
1456
1457 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1458 assert(q != nullptr, "object iterate queue must not be null");
1459
1460 ShenandoahMarkTask t;
1461 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1462
1463 // Work through the queue to traverse heap.
1464 // Steal when there is no task in queue.
1465 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1466 oop obj = t.obj();
1467 assert(oopDesc::is_oop(obj), "must be a valid oop");
1468 cl->do_object(obj);
1469 obj->oop_iterate(&oops);
1470 }
1471 assert(q->is_empty(), "should be empty");
1472 }
1473 };
1474
1475 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1476 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1477 }
1478
1479 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1480 void ShenandoahHeap::keep_alive(oop obj) {
1481 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1482 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1483 }
1484 }
1485
1486 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1487 for (size_t i = 0; i < num_regions(); i++) {
1488 ShenandoahHeapRegion* current = get_region(i);
1489 blk->heap_region_do(current);
1490 }
1491 }
1492
1493 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1494 private:
1495 ShenandoahHeap* const _heap;
1496 ShenandoahHeapRegionClosure* const _blk;
1497
1498 shenandoah_padding(0);
1499 volatile size_t _index;
1500 shenandoah_padding(1);
1501
1502 public:
1503 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1504 WorkerTask("Shenandoah Parallel Region Operation"),
1505 _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1506
1507 void work(uint worker_id) {
1508 ShenandoahParallelWorkerSession worker_session(worker_id);
1509 size_t stride = ShenandoahParallelRegionStride;
1510
1511 size_t max = _heap->num_regions();
1512 while (Atomic::load(&_index) < max) {
1513 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1514 size_t start = cur;
1515 size_t end = MIN2(cur + stride, max);
1516 if (start >= max) break;
1517
1518 for (size_t i = cur; i < end; i++) {
1519 ShenandoahHeapRegion* current = _heap->get_region(i);
1520 _blk->heap_region_do(current);
1521 }
1522 }
1523 }
1524 };
1525
1526 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1527 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1528 if (num_regions() > ShenandoahParallelRegionStride) {
1529 ShenandoahParallelHeapRegionTask task(blk);
1530 workers()->run_task(&task);
1531 } else {
1532 heap_region_iterate(blk);
1533 }
1534 }
1535
1536 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1537 private:
1538 ShenandoahMarkingContext* const _ctx;
1539 public:
1540 ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1541
1542 void heap_region_do(ShenandoahHeapRegion* r) {
1543 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1544 if (r->is_active()) {
1545 // Check if region needs updating its TAMS. We have updated it already during concurrent
1546 // reset, so it is very likely we don't need to do another write here.
1547 if (_ctx->top_at_mark_start(r) != r->top()) {
1548 _ctx->capture_top_at_mark_start(r);
1549 }
1550 } else {
1551 assert(_ctx->top_at_mark_start(r) == r->top(),
1552 "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
1553 }
1554 }
1555
1556 bool is_thread_safe() { return true; }
1557 };
1558
1559 class ShenandoahRendezvousClosure : public HandshakeClosure {
1560 public:
1561 inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
1562 inline void do_thread(Thread* thread) {}
1563 };
1564
1565 void ShenandoahHeap::rendezvous_threads() {
1566 ShenandoahRendezvousClosure cl;
1567 Handshake::execute(&cl);
1568 }
1569
1570 void ShenandoahHeap::recycle_trash() {
1571 free_set()->recycle_trash();
1572 }
1573
1574 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1575 private:
1576 ShenandoahMarkingContext* const _ctx;
1577 public:
1578 ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1579
1580 void heap_region_do(ShenandoahHeapRegion* r) {
1581 if (r->is_active()) {
1582 // Reset live data and set TAMS optimistically. We would recheck these under the pause
1583 // anyway to capture any updates that happened since now.
1584 r->clear_live_data();
1585 _ctx->capture_top_at_mark_start(r);
1586 }
1587 }
1588
1589 bool is_thread_safe() { return true; }
1590 };
1591
1592 void ShenandoahHeap::prepare_gc() {
1593 reset_mark_bitmap();
1594
1595 ShenandoahResetUpdateRegionStateClosure cl;
1596 parallel_heap_region_iterate(&cl);
1597 }
1598
1599 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1600 private:
1601 ShenandoahMarkingContext* const _ctx;
1602 ShenandoahHeapLock* const _lock;
1603
1604 public:
1605 ShenandoahFinalMarkUpdateRegionStateClosure() :
1606 _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1607
1608 void heap_region_do(ShenandoahHeapRegion* r) {
1609 if (r->is_active()) {
1610 // All allocations past TAMS are implicitly live, adjust the region data.
1611 // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1612 HeapWord *tams = _ctx->top_at_mark_start(r);
1613 HeapWord *top = r->top();
1614 if (top > tams) {
1615 r->increase_live_data_alloc_words(pointer_delta(top, tams));
1616 }
1617
1618 // We are about to select the collection set, make sure it knows about
1619 // current pinning status. Also, this allows trashing more regions that
1620 // now have their pinning status dropped.
1621 if (r->is_pinned()) {
1622 if (r->pin_count() == 0) {
1623 ShenandoahHeapLocker locker(_lock);
1624 r->make_unpinned();
1625 }
1626 } else {
1627 if (r->pin_count() > 0) {
1628 ShenandoahHeapLocker locker(_lock);
1629 r->make_pinned();
1630 }
1631 }
1632
1633 // Remember limit for updating refs. It's guaranteed that we get no
1634 // from-space-refs written from here on.
1635 r->set_update_watermark_at_safepoint(r->top());
1636 } else {
1637 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1638 assert(_ctx->top_at_mark_start(r) == r->top(),
1639 "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1640 }
1641 }
1642
1643 bool is_thread_safe() { return true; }
1644 };
1645
1646 void ShenandoahHeap::prepare_regions_and_collection_set(bool concurrent) {
1647 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
1648 {
1649 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states :
1650 ShenandoahPhaseTimings::degen_gc_final_update_region_states);
1651 ShenandoahFinalMarkUpdateRegionStateClosure cl;
1652 parallel_heap_region_iterate(&cl);
1653
1654 assert_pinned_region_status();
1655 }
1656
1657 {
1658 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset :
1659 ShenandoahPhaseTimings::degen_gc_choose_cset);
1660 ShenandoahHeapLocker locker(lock());
1661 _collection_set->clear();
1662 heuristics()->choose_collection_set(_collection_set);
1663 }
1664
1665 {
1666 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset :
1667 ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
1668 ShenandoahHeapLocker locker(lock());
1669 _free_set->rebuild();
1670 }
1671 }
1672
1673 void ShenandoahHeap::do_class_unloading() {
1674 _unloader.unload();
1675 }
1676
1677 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1678 // Weak refs processing
1679 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1680 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1681 ShenandoahTimingsTracker t(phase);
1682 ShenandoahGCWorkerPhase worker_phase(phase);
1683 ref_processor()->process_references(phase, workers(), false /* concurrent */);
1684 }
1685
1686 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1687 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1688
1689 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1690 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1691 // for future GCLABs here.
1692 if (UseTLAB) {
1693 ShenandoahGCPhase phase(concurrent ?
1694 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1695 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1696 gclabs_retire(ResizeTLAB);
1697 }
1698
1699 _update_refs_iterator.reset();
1700 }
1701
1702 void ShenandoahHeap::set_gc_state_all_threads(char state) {
1703 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1704 ShenandoahThreadLocalData::set_gc_state(t, state);
1705 }
1706 }
1707
1708 void ShenandoahHeap::set_gc_state_mask(uint mask, bool value) {
1709 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should really be Shenandoah safepoint");
1710 _gc_state.set_cond(mask, value);
1711 set_gc_state_all_threads(_gc_state.raw_value());
1712 }
1713
1714 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1715 assert(!has_forwarded_objects(), "Not expected before/after mark phase");
1716 set_gc_state_mask(MARKING, in_progress);
1717 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1718 }
1719
1720 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1721 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1722 set_gc_state_mask(EVACUATION, in_progress);
1723 }
1724
1725 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
1726 if (in_progress) {
1727 _concurrent_strong_root_in_progress.set();
1728 } else {
1729 _concurrent_strong_root_in_progress.unset();
1730 }
1731 }
1732
1733 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
1734 set_gc_state_mask(WEAK_ROOTS, cond);
1735 }
1736
1737 GCTracer* ShenandoahHeap::tracer() {
1738 return shenandoah_policy()->tracer();
1739 }
1740
1741 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1742 return _free_set->used();
1743 }
1744
1745 bool ShenandoahHeap::try_cancel_gc() {
1746 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1747 return prev == CANCELLABLE;
1748 }
1749
1750 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1751 if (try_cancel_gc()) {
1752 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1753 log_info(gc)("%s", msg.buffer());
1754 Events::log(Thread::current(), "%s", msg.buffer());
1755 }
1756 }
1757
1758 uint ShenandoahHeap::max_workers() {
1759 return _max_workers;
1760 }
1761
1762 void ShenandoahHeap::stop() {
1763 // The shutdown sequence should be able to terminate when GC is running.
1764
1765 // Step 0. Notify policy to disable event recording.
1766 _shenandoah_policy->record_shutdown();
1767
1768 // Step 1. Notify control thread that we are in shutdown.
1769 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1770 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1771 control_thread()->prepare_for_graceful_shutdown();
1772
1773 // Step 2. Notify GC workers that we are cancelling GC.
1774 cancel_gc(GCCause::_shenandoah_stop_vm);
1775
1776 // Step 3. Wait until GC worker exits normally.
1777 control_thread()->stop();
1778 }
1779
1780 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1781 if (!unload_classes()) return;
1782 // Unload classes and purge SystemDictionary.
1783 {
1784 ShenandoahPhaseTimings::Phase phase = full_gc ?
1785 ShenandoahPhaseTimings::full_gc_purge_class_unload :
1786 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
1787 ShenandoahIsAliveSelector is_alive;
1788 CodeCache::UnloadingScope scope(is_alive.is_alive_closure());
1789 ShenandoahGCPhase gc_phase(phase);
1790 ShenandoahGCWorkerPhase worker_phase(phase);
1791 bool purged_class = SystemDictionary::do_unloading(gc_timer());
1792
1793 uint num_workers = _workers->active_workers();
1794 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, purged_class);
1795 _workers->run_task(&unlink_task);
1796 }
1797
1798 {
1799 ShenandoahGCPhase phase(full_gc ?
1800 ShenandoahPhaseTimings::full_gc_purge_cldg :
1801 ShenandoahPhaseTimings::degen_gc_purge_cldg);
1802 ClassLoaderDataGraph::purge(/*at_safepoint*/true);
1803 }
1804 // Resize and verify metaspace
1805 MetaspaceGC::compute_new_size();
1806 DEBUG_ONLY(MetaspaceUtils::verify();)
1807 }
1808
1809 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
1810 // so they should not have forwarded oops.
1811 // However, we do need to "null" dead oops in the roots, if can not be done
1812 // in concurrent cycles.
1813 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
1814 uint num_workers = _workers->active_workers();
1815 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
1816 ShenandoahPhaseTimings::full_gc_purge_weak_par :
1817 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
1818 ShenandoahGCPhase phase(timing_phase);
1819 ShenandoahGCWorkerPhase worker_phase(timing_phase);
1820 // Cleanup weak roots
1821 if (has_forwarded_objects()) {
1822 ShenandoahForwardedIsAliveClosure is_alive;
1823 ShenandoahUpdateRefsClosure keep_alive;
1824 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
1825 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
1826 _workers->run_task(&cleaning_task);
1827 } else {
1828 ShenandoahIsAliveClosure is_alive;
1829 #ifdef ASSERT
1830 ShenandoahAssertNotForwardedClosure verify_cl;
1831 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
1832 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
1833 #else
1834 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
1835 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
1836 #endif
1837 _workers->run_task(&cleaning_task);
1838 }
1839 }
1840
1841 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
1842 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1843 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
1844 ShenandoahGCPhase phase(full_gc ?
1845 ShenandoahPhaseTimings::full_gc_purge :
1846 ShenandoahPhaseTimings::degen_gc_purge);
1847 stw_weak_refs(full_gc);
1848 stw_process_weak_roots(full_gc);
1849 stw_unload_classes(full_gc);
1850 }
1851
1852 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
1853 set_gc_state_mask(HAS_FORWARDED, cond);
1854 }
1855
1856 void ShenandoahHeap::set_unload_classes(bool uc) {
1857 _unload_classes.set_cond(uc);
1858 }
1859
1860 bool ShenandoahHeap::unload_classes() const {
1861 return _unload_classes.is_set();
1862 }
1863
1864 address ShenandoahHeap::in_cset_fast_test_addr() {
1865 ShenandoahHeap* heap = ShenandoahHeap::heap();
1866 assert(heap->collection_set() != nullptr, "Sanity");
1867 return (address) heap->collection_set()->biased_map_address();
1868 }
1869
1870 address ShenandoahHeap::cancelled_gc_addr() {
1871 return (address) ShenandoahHeap::heap()->_cancelled_gc.addr_of();
1872 }
1873
1874 address ShenandoahHeap::gc_state_addr() {
1875 return (address) ShenandoahHeap::heap()->_gc_state.addr_of();
1876 }
1877
1878 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
1879 return Atomic::load(&_bytes_allocated_since_gc_start);
1880 }
1881
1882 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
1883 Atomic::store(&_bytes_allocated_since_gc_start, (size_t)0);
1884 }
1885
1886 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
1887 _degenerated_gc_in_progress.set_cond(in_progress);
1888 }
1889
1890 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
1891 _full_gc_in_progress.set_cond(in_progress);
1892 }
1893
1894 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
1895 assert (is_full_gc_in_progress(), "should be");
1896 _full_gc_move_in_progress.set_cond(in_progress);
1897 }
1898
1899 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
1900 set_gc_state_mask(UPDATEREFS, in_progress);
1901 }
1902
1903 void ShenandoahHeap::register_nmethod(nmethod* nm) {
1904 ShenandoahCodeRoots::register_nmethod(nm);
1905 }
1906
1907 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
1908 ShenandoahCodeRoots::unregister_nmethod(nm);
1909 }
1910
1911 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
1912 heap_region_containing(o)->record_pin();
1913 }
1914
1915 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
1916 ShenandoahHeapRegion* r = heap_region_containing(o);
1917 assert(r != nullptr, "Sanity");
1918 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
1919 r->record_unpin();
1920 }
1921
1922 void ShenandoahHeap::sync_pinned_region_status() {
1923 ShenandoahHeapLocker locker(lock());
1924
1925 for (size_t i = 0; i < num_regions(); i++) {
1926 ShenandoahHeapRegion *r = get_region(i);
1927 if (r->is_active()) {
1928 if (r->is_pinned()) {
1929 if (r->pin_count() == 0) {
1930 r->make_unpinned();
1931 }
1932 } else {
1933 if (r->pin_count() > 0) {
1934 r->make_pinned();
1935 }
1936 }
1937 }
1938 }
1939
1940 assert_pinned_region_status();
1941 }
1942
1943 #ifdef ASSERT
1944 void ShenandoahHeap::assert_pinned_region_status() {
1945 for (size_t i = 0; i < num_regions(); i++) {
1946 ShenandoahHeapRegion* r = get_region(i);
1947 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
1948 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
1949 }
1950 }
1951 #endif
1952
1953 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
1954 return _gc_timer;
1955 }
1956
1957 void ShenandoahHeap::prepare_concurrent_roots() {
1958 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1959 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1960 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
1961 set_concurrent_weak_root_in_progress(true);
1962 if (unload_classes()) {
1963 _unloader.prepare();
1964 }
1965 }
1966
1967 void ShenandoahHeap::finish_concurrent_roots() {
1968 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1969 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1970 if (unload_classes()) {
1971 _unloader.finish();
1972 }
1973 }
1974
1975 #ifdef ASSERT
1976 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
1977 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
1978
1979 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1980 if (UseDynamicNumberOfGCThreads) {
1981 assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
1982 } else {
1983 // Use ParallelGCThreads inside safepoints
1984 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
1985 }
1986 } else {
1987 if (UseDynamicNumberOfGCThreads) {
1988 assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
1989 } else {
1990 // Use ConcGCThreads outside safepoints
1991 assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
1992 }
1993 }
1994 }
1995 #endif
1996
1997 ShenandoahVerifier* ShenandoahHeap::verifier() {
1998 guarantee(ShenandoahVerify, "Should be enabled");
1999 assert (_verifier != nullptr, "sanity");
2000 return _verifier;
2001 }
2002
2003 template<bool CONCURRENT>
2004 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2005 private:
2006 ShenandoahHeap* _heap;
2007 ShenandoahRegionIterator* _regions;
2008 public:
2009 ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2010 WorkerTask("Shenandoah Update References"),
2011 _heap(ShenandoahHeap::heap()),
2012 _regions(regions) {
2013 }
2014
2015 void work(uint worker_id) {
2016 if (CONCURRENT) {
2017 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2018 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
2019 do_work<ShenandoahConcUpdateRefsClosure>();
2020 } else {
2021 ShenandoahParallelWorkerSession worker_session(worker_id);
2022 do_work<ShenandoahSTWUpdateRefsClosure>();
2023 }
2024 }
2025
2026 private:
2027 template<class T>
2028 void do_work() {
2029 T cl;
2030 ShenandoahHeapRegion* r = _regions->next();
2031 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2032 while (r != nullptr) {
2033 HeapWord* update_watermark = r->get_update_watermark();
2034 assert (update_watermark >= r->bottom(), "sanity");
2035 if (r->is_active() && !r->is_cset()) {
2036 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2037 }
2038 if (ShenandoahPacing) {
2039 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2040 }
2041 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2042 return;
2043 }
2044 r = _regions->next();
2045 }
2046 }
2047 };
2048
2049 void ShenandoahHeap::update_heap_references(bool concurrent) {
2050 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2051
2052 if (concurrent) {
2053 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2054 workers()->run_task(&task);
2055 } else {
2056 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2057 workers()->run_task(&task);
2058 }
2059 }
2060
2061
2062 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2063 private:
2064 ShenandoahHeapLock* const _lock;
2065
2066 public:
2067 ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2068
2069 void heap_region_do(ShenandoahHeapRegion* r) {
2070 // Drop unnecessary "pinned" state from regions that does not have CP marks
2071 // anymore, as this would allow trashing them.
2072
2073 if (r->is_active()) {
2074 if (r->is_pinned()) {
2075 if (r->pin_count() == 0) {
2076 ShenandoahHeapLocker locker(_lock);
2077 r->make_unpinned();
2078 }
2079 } else {
2080 if (r->pin_count() > 0) {
2081 ShenandoahHeapLocker locker(_lock);
2082 r->make_pinned();
2083 }
2084 }
2085 }
2086 }
2087
2088 bool is_thread_safe() { return true; }
2089 };
2090
2091 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2092 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2093 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2094
2095 {
2096 ShenandoahGCPhase phase(concurrent ?
2097 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2098 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2099 ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2100 parallel_heap_region_iterate(&cl);
2101
2102 assert_pinned_region_status();
2103 }
2104
2105 {
2106 ShenandoahGCPhase phase(concurrent ?
2107 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2108 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2109 trash_cset_regions();
2110 }
2111 }
2112
2113 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2114 {
2115 ShenandoahGCPhase phase(concurrent ?
2116 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2117 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2118 ShenandoahHeapLocker locker(lock());
2119 _free_set->rebuild();
2120 }
2121 }
2122
2123 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2124 print_on(st);
2125 st->cr();
2126 print_heap_regions_on(st);
2127 }
2128
2129 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2130 size_t slice = r->index() / _bitmap_regions_per_slice;
2131
2132 size_t regions_from = _bitmap_regions_per_slice * slice;
2133 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2134 for (size_t g = regions_from; g < regions_to; g++) {
2135 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2136 if (skip_self && g == r->index()) continue;
2137 if (get_region(g)->is_committed()) {
2138 return true;
2139 }
2140 }
2141 return false;
2142 }
2143
2144 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2145 shenandoah_assert_heaplocked();
2146
2147 // Bitmaps in special regions do not need commits
2148 if (_bitmap_region_special) {
2149 return true;
2150 }
2151
2152 if (is_bitmap_slice_committed(r, true)) {
2153 // Some other region from the group is already committed, meaning the bitmap
2154 // slice is already committed, we exit right away.
2155 return true;
2156 }
2157
2158 // Commit the bitmap slice:
2159 size_t slice = r->index() / _bitmap_regions_per_slice;
2160 size_t off = _bitmap_bytes_per_slice * slice;
2161 size_t len = _bitmap_bytes_per_slice;
2162 char* start = (char*) _bitmap_region.start() + off;
2163
2164 if (!os::commit_memory(start, len, false)) {
2165 return false;
2166 }
2167
2168 if (AlwaysPreTouch) {
2169 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2170 }
2171
2172 return true;
2173 }
2174
2175 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2176 shenandoah_assert_heaplocked();
2177
2178 // Bitmaps in special regions do not need uncommits
2179 if (_bitmap_region_special) {
2180 return true;
2181 }
2182
2183 if (is_bitmap_slice_committed(r, true)) {
2184 // Some other region from the group is still committed, meaning the bitmap
2185 // slice is should stay committed, exit right away.
2186 return true;
2187 }
2188
2189 // Uncommit the bitmap slice:
2190 size_t slice = r->index() / _bitmap_regions_per_slice;
2191 size_t off = _bitmap_bytes_per_slice * slice;
2192 size_t len = _bitmap_bytes_per_slice;
2193 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2194 return false;
2195 }
2196 return true;
2197 }
2198
2199 void ShenandoahHeap::safepoint_synchronize_begin() {
2200 if (ShenandoahSuspendibleWorkers) {
2201 SuspendibleThreadSet::synchronize();
2202 }
2203 }
2204
2205 void ShenandoahHeap::safepoint_synchronize_end() {
2206 if (ShenandoahSuspendibleWorkers) {
2207 SuspendibleThreadSet::desynchronize();
2208 }
2209 }
2210
2211 void ShenandoahHeap::entry_uncommit(double shrink_before, size_t shrink_until) {
2212 static const char *msg = "Concurrent uncommit";
2213 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
2214 EventMark em("%s", msg);
2215
2216 op_uncommit(shrink_before, shrink_until);
2217 }
2218
2219 void ShenandoahHeap::try_inject_alloc_failure() {
2220 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2221 _inject_alloc_failure.set();
2222 os::naked_short_sleep(1);
2223 if (cancelled_gc()) {
2224 log_info(gc)("Allocation failure was successfully injected");
2225 }
2226 }
2227 }
2228
2229 bool ShenandoahHeap::should_inject_alloc_failure() {
2230 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2231 }
2232
2233 void ShenandoahHeap::initialize_serviceability() {
2234 _memory_pool = new ShenandoahMemoryPool(this);
2235 _cycle_memory_manager.add_pool(_memory_pool);
2236 _stw_memory_manager.add_pool(_memory_pool);
2237 }
2238
2239 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2240 GrowableArray<GCMemoryManager*> memory_managers(2);
2241 memory_managers.append(&_cycle_memory_manager);
2242 memory_managers.append(&_stw_memory_manager);
2243 return memory_managers;
2244 }
2245
2246 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2247 GrowableArray<MemoryPool*> memory_pools(1);
2248 memory_pools.append(_memory_pool);
2249 return memory_pools;
2250 }
2251
2252 MemoryUsage ShenandoahHeap::memory_usage() {
2253 return _memory_pool->get_memory_usage();
2254 }
2255
2256 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2257 _heap(ShenandoahHeap::heap()),
2258 _index(0) {}
2259
2260 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2261 _heap(heap),
2262 _index(0) {}
2263
2264 void ShenandoahRegionIterator::reset() {
2265 _index = 0;
2266 }
2267
2268 bool ShenandoahRegionIterator::has_next() const {
2269 return _index < _heap->num_regions();
2270 }
2271
2272 char ShenandoahHeap::gc_state() const {
2273 return _gc_state.raw_value();
2274 }
2275
2276 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2277 #ifdef ASSERT
2278 assert(_liveness_cache != nullptr, "sanity");
2279 assert(worker_id < _max_workers, "sanity");
2280 for (uint i = 0; i < num_regions(); i++) {
2281 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2282 }
2283 #endif
2284 return _liveness_cache[worker_id];
2285 }
2286
2287 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2288 assert(worker_id < _max_workers, "sanity");
2289 assert(_liveness_cache != nullptr, "sanity");
2290 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2291 for (uint i = 0; i < num_regions(); i++) {
2292 ShenandoahLiveData live = ld[i];
2293 if (live > 0) {
2294 ShenandoahHeapRegion* r = get_region(i);
2295 r->increase_live_data_gc_words(live);
2296 ld[i] = 0;
2297 }
2298 }
2299 }
2300
2301 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2302 if (is_idle()) return false;
2303
2304 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2305 // marking phase.
2306 if (is_concurrent_mark_in_progress() &&
2307 !marking_context()->allocated_after_mark_start(obj)) {
2308 return true;
2309 }
2310
2311 // Can not guarantee obj is deeply good.
2312 if (has_forwarded_objects()) {
2313 return true;
2314 }
2315
2316 return false;
2317 }