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