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/shenandoahCardTable.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/shenandoahRegulatorThread.hpp"
47 #include "gc/shenandoah/shenandoahFreeSet.hpp"
48 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
49 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
50 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
51 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
52 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
53 #include "gc/shenandoah/shenandoahInitLogger.hpp"
54 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
55 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
56 #include "gc/shenandoah/shenandoahMetrics.hpp"
57 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
58 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
59 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
60 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
61 #include "gc/shenandoah/shenandoahPadding.hpp"
62 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
63 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
64 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
65 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
66 #include "gc/shenandoah/shenandoahStringDedup.hpp"
67 #include "gc/shenandoah/shenandoahSTWMark.hpp"
68 #include "gc/shenandoah/shenandoahUtils.hpp"
69 #include "gc/shenandoah/shenandoahVerifier.hpp"
70 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
71 #include "gc/shenandoah/shenandoahVMOperations.hpp"
72 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
73 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
74 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
75 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
76 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
77 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
78 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
79
80 #if INCLUDE_JFR
81 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
82 #endif
83
84 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
85
86 #include "classfile/systemDictionary.hpp"
87 #include "code/codeCache.hpp"
88 #include "memory/classLoaderMetaspace.hpp"
89 #include "memory/metaspaceUtils.hpp"
90 #include "oops/compressedOops.inline.hpp"
91 #include "prims/jvmtiTagMap.hpp"
92 #include "runtime/atomic.hpp"
93 #include "runtime/globals.hpp"
94 #include "runtime/interfaceSupport.inline.hpp"
95 #include "runtime/java.hpp"
96 #include "runtime/orderAccess.hpp"
97 #include "runtime/safepointMechanism.hpp"
98 #include "runtime/vmThread.hpp"
99 #include "services/mallocTracker.hpp"
100 #include "services/memTracker.hpp"
101 #include "utilities/events.hpp"
102 #include "utilities/powerOfTwo.hpp"
103
104 class ShenandoahPretouchHeapTask : public WorkerTask {
105 private:
106 ShenandoahRegionIterator _regions;
107 const size_t _page_size;
108 public:
109 ShenandoahPretouchHeapTask(size_t page_size) :
110 WorkerTask("Shenandoah Pretouch Heap"),
111 _page_size(page_size) {}
112
113 virtual void work(uint worker_id) {
114 ShenandoahHeapRegion* r = _regions.next();
115 while (r != nullptr) {
116 if (r->is_committed()) {
117 os::pretouch_memory(r->bottom(), r->end(), _page_size);
118 }
119 r = _regions.next();
120 }
121 }
122 };
123
124 class ShenandoahPretouchBitmapTask : public WorkerTask {
125 private:
126 ShenandoahRegionIterator _regions;
127 char* _bitmap_base;
128 const size_t _bitmap_size;
129 const size_t _page_size;
130 public:
131 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
132 WorkerTask("Shenandoah Pretouch Bitmap"),
133 _bitmap_base(bitmap_base),
134 _bitmap_size(bitmap_size),
135 _page_size(page_size) {}
136
137 virtual void work(uint worker_id) {
138 ShenandoahHeapRegion* r = _regions.next();
139 while (r != nullptr) {
140 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
141 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
142 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
143
144 if (r->is_committed()) {
145 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
146 }
147
148 r = _regions.next();
149 }
150 }
151 };
152
153 jint ShenandoahHeap::initialize() {
154 //
155 // Figure out heap sizing
156 //
157
158 size_t init_byte_size = InitialHeapSize;
159 size_t min_byte_size = MinHeapSize;
160 size_t max_byte_size = MaxHeapSize;
161 size_t heap_alignment = HeapAlignment;
162
163 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
164
165 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
166 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
167
168 _num_regions = ShenandoahHeapRegion::region_count();
169 assert(_num_regions == (max_byte_size / reg_size_bytes),
170 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
171 _num_regions, max_byte_size, reg_size_bytes);
172
173 size_t num_committed_regions = init_byte_size / reg_size_bytes;
174 num_committed_regions = MIN2(num_committed_regions, _num_regions);
175 assert(num_committed_regions <= _num_regions, "sanity");
176 _initial_size = num_committed_regions * reg_size_bytes;
177
178 size_t num_min_regions = min_byte_size / reg_size_bytes;
179 num_min_regions = MIN2(num_min_regions, _num_regions);
180 assert(num_min_regions <= _num_regions, "sanity");
181 _minimum_size = num_min_regions * reg_size_bytes;
182
183 // Default to max heap size.
184 _soft_max_size = _num_regions * reg_size_bytes;
185
186 _committed = _initial_size;
187
188 // Now we know the number of regions and heap sizes, initialize the heuristics.
189 initialize_generations();
190 initialize_heuristics();
191
192 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
193 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
194 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
195
196 //
197 // Reserve and commit memory for heap
198 //
199
200 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
201 initialize_reserved_region(heap_rs);
202 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
203 _heap_region_special = heap_rs.special();
204
205 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
206 "Misaligned heap: " PTR_FORMAT, p2i(base()));
207
208 #if SHENANDOAH_OPTIMIZED_MARKTASK
209 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
210 // Fail if we ever attempt to address more than we can.
211 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
212 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
213 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
214 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
215 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
216 vm_exit_during_initialization("Fatal Error", buf);
217 }
218 #endif
219
220 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
221 if (!_heap_region_special) {
222 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
223 "Cannot commit heap memory");
224 }
225
226 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
227
228 //
229 // After reserving the Java heap, create the card table, barriers, and workers, in dependency order
230 //
231 if (mode()->is_generational()) {
232 ShenandoahDirectCardMarkRememberedSet *rs;
233 ShenandoahCardTable* card_table = ShenandoahBarrierSet::barrier_set()->card_table();
234 size_t card_count = card_table->cards_required(heap_rs.size() / HeapWordSize);
235 rs = new ShenandoahDirectCardMarkRememberedSet(ShenandoahBarrierSet::barrier_set()->card_table(), card_count);
236 _card_scan = new ShenandoahScanRemembered<ShenandoahDirectCardMarkRememberedSet>(rs);
237 }
238
239 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
240 if (_workers == nullptr) {
241 vm_exit_during_initialization("Failed necessary allocation.");
242 } else {
243 _workers->initialize_workers();
244 }
245
246 if (ParallelGCThreads > 1) {
247 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
248 _safepoint_workers->initialize_workers();
249 }
250
251 //
252 // Reserve and commit memory for bitmap(s)
253 //
254
255 _bitmap_size = ShenandoahMarkBitMap::compute_size(heap_rs.size());
256 _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
257
258 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
259
260 guarantee(bitmap_bytes_per_region != 0,
261 "Bitmap bytes per region should not be zero");
262 guarantee(is_power_of_2(bitmap_bytes_per_region),
263 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
264
265 if (bitmap_page_size > bitmap_bytes_per_region) {
266 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
267 _bitmap_bytes_per_slice = bitmap_page_size;
268 } else {
269 _bitmap_regions_per_slice = 1;
270 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
271 }
272
273 guarantee(_bitmap_regions_per_slice >= 1,
274 "Should have at least one region per slice: " SIZE_FORMAT,
275 _bitmap_regions_per_slice);
276
277 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
278 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
279 _bitmap_bytes_per_slice, bitmap_page_size);
280
281 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
282 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
283 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
284 _bitmap_region_special = bitmap.special();
285
286 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
287 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
288 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
289 if (!_bitmap_region_special) {
290 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
291 "Cannot commit bitmap memory");
292 }
293
294 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
295
296 if (ShenandoahVerify) {
297 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
298 if (!verify_bitmap.special()) {
299 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
300 "Cannot commit verification bitmap memory");
301 }
302 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
303 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
304 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
305 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
306 }
307
308 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
309 ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
310 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
311 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
312 _aux_bitmap_region_special = aux_bitmap.special();
313 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
314
315 //
316 // Create regions and region sets
317 //
318 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
319 size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
320 region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
321
322 ReservedSpace region_storage(region_storage_size, region_page_size);
323 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
324 if (!region_storage.special()) {
325 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
326 "Cannot commit region memory");
327 }
328
329 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
330 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
331 // If not successful, bite a bullet and allocate at whatever address.
332 {
333 size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
334 size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
335
336 uintptr_t min = round_up_power_of_2(cset_align);
337 uintptr_t max = (1u << 30u);
338
339 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
340 char* req_addr = (char*)addr;
341 assert(is_aligned(req_addr, cset_align), "Should be aligned");
342 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size(), req_addr);
343 if (cset_rs.is_reserved()) {
344 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
345 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
346 break;
347 }
348 }
349
350 if (_collection_set == nullptr) {
351 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size());
352 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
353 }
354 }
355
356 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
357 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
358 _free_set = new ShenandoahFreeSet(this, _num_regions);
359
360 {
361 ShenandoahHeapLocker locker(lock());
362
363
364 for (size_t i = 0; i < _num_regions; i++) {
365 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
366 bool is_committed = i < num_committed_regions;
367 void* loc = region_storage.base() + i * region_align;
368
369 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
370 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
371
372 _marking_context->initialize_top_at_mark_start(r);
373 _regions[i] = r;
374 assert(!collection_set()->is_in(i), "New region should not be in collection set");
375
376 _affiliations[i] = ShenandoahRegionAffiliation::FREE;
377 }
378
379 // Initialize to complete
380 _marking_context->mark_complete();
381
382 _free_set->rebuild();
383 }
384
385 if (AlwaysPreTouch) {
386 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
387 // before initialize() below zeroes it with initializing thread. For any given region,
388 // we touch the region and the corresponding bitmaps from the same thread.
389 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
390
391 _pretouch_heap_page_size = heap_page_size;
392 _pretouch_bitmap_page_size = bitmap_page_size;
393
394 #ifdef LINUX
395 // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
396 // pages. But, the kernel needs to know that every small page is used, in order to coalesce
397 // them into huge one. Therefore, we need to pretouch with smaller pages.
398 if (UseTransparentHugePages) {
399 _pretouch_heap_page_size = (size_t)os::vm_page_size();
400 _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
401 }
402 #endif
403
404 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
405 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
406
407 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
408 _workers->run_task(&bcl);
409
410 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
411 _workers->run_task(&hcl);
412 }
413
414 //
415 // Initialize the rest of GC subsystems
416 //
417
418 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
419 for (uint worker = 0; worker < _max_workers; worker++) {
420 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
421 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
422 }
423
424 // There should probably be Shenandoah-specific options for these,
425 // just as there are G1-specific options.
426 {
427 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
428 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
429 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
430 }
431
432 _monitoring_support = new ShenandoahMonitoringSupport(this);
433 _phase_timings = new ShenandoahPhaseTimings(max_workers());
434 ShenandoahCodeRoots::initialize();
435
436 if (ShenandoahPacing) {
437 _pacer = new ShenandoahPacer(this);
438 _pacer->setup_for_idle();
439 } else {
440 _pacer = nullptr;
441 }
442
443 _control_thread = new ShenandoahControlThread();
444 _regulator_thread = new ShenandoahRegulatorThread(_control_thread);
445
446 ShenandoahInitLogger::print();
447
448 return JNI_OK;
449 }
450
451 size_t ShenandoahHeap::max_size_for(ShenandoahGeneration* generation) const {
452 switch (generation->generation_mode()) {
453 case YOUNG: return _generation_sizer.max_young_size();
454 case OLD: return max_capacity() - _generation_sizer.min_young_size();
455 case GLOBAL: return max_capacity();
456 default:
457 ShouldNotReachHere();
458 return 0;
459 }
460 }
461
462 size_t ShenandoahHeap::min_size_for(ShenandoahGeneration* generation) const {
463 switch (generation->generation_mode()) {
464 case YOUNG: return _generation_sizer.min_young_size();
465 case OLD: return max_capacity() - _generation_sizer.max_young_size();
466 case GLOBAL: return min_capacity();
467 default:
468 ShouldNotReachHere();
469 return 0;
470 }
471 }
472
473 void ShenandoahHeap::initialize_generations() {
474 // Max capacity is the maximum _allowed_ capacity. That is, the maximum allowed capacity
475 // for old would be total heap - minimum capacity of young. This means the sum of the maximum
476 // allowed for old and young could exceed the total heap size. It remains the case that the
477 // _actual_ capacity of young + old = total.
478 _generation_sizer.heap_size_changed(soft_max_capacity());
479 size_t initial_capacity_young = _generation_sizer.max_young_size();
480 size_t max_capacity_young = _generation_sizer.max_young_size();
481 size_t initial_capacity_old = max_capacity() - max_capacity_young;
482 size_t max_capacity_old = max_capacity() - initial_capacity_young;
483
484 _young_generation = new ShenandoahYoungGeneration(_max_workers, max_capacity_young, initial_capacity_young);
485 _old_generation = new ShenandoahOldGeneration(_max_workers, max_capacity_old, initial_capacity_old);
486 _global_generation = new ShenandoahGlobalGeneration(_max_workers, soft_max_capacity(), soft_max_capacity());
487 }
488
489 void ShenandoahHeap::initialize_heuristics() {
490 if (ShenandoahGCMode != nullptr) {
491 if (strcmp(ShenandoahGCMode, "satb") == 0) {
492 _gc_mode = new ShenandoahSATBMode();
493 } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
494 _gc_mode = new ShenandoahIUMode();
495 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
496 _gc_mode = new ShenandoahPassiveMode();
497 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
498 _gc_mode = new ShenandoahGenerationalMode();
499 } else {
500 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
501 }
502 } else {
503 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
504 }
505 _gc_mode->initialize_flags();
506 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
507 vm_exit_during_initialization(
508 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
509 _gc_mode->name()));
510 }
511 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
512 vm_exit_during_initialization(
513 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
514 _gc_mode->name()));
515 }
516
517 _global_generation->initialize_heuristics(_gc_mode);
518 if (mode()->is_generational()) {
519 _young_generation->initialize_heuristics(_gc_mode);
520 _old_generation->initialize_heuristics(_gc_mode);
521
522 ShenandoahEvacWaste = ShenandoahGenerationalEvacWaste;
523 }
524 }
525
526 #ifdef _MSC_VER
527 #pragma warning( push )
528 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
529 #endif
530
531 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
532 CollectedHeap(),
533 _gc_generation(nullptr),
534 _prepare_for_old_mark(false),
535 _initial_size(0),
536 _used(0),
537 _committed(0),
538 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
539 _workers(nullptr),
540 _safepoint_workers(nullptr),
541 _heap_region_special(false),
542 _num_regions(0),
543 _regions(nullptr),
544 _affiliations(nullptr),
545 _update_refs_iterator(this),
546 _alloc_supplement_reserve(0),
547 _promoted_reserve(0),
548 _old_evac_reserve(0),
549 _old_evac_expended(0),
550 _young_evac_reserve(0),
551 _captured_old_usage(0),
552 _previous_promotion(0),
553 _cancel_requested_time(0),
554 _young_generation(nullptr),
555 _global_generation(nullptr),
556 _old_generation(nullptr),
557 _control_thread(nullptr),
558 _regulator_thread(nullptr),
559 _shenandoah_policy(policy),
560 _free_set(nullptr),
561 _pacer(nullptr),
562 _verifier(nullptr),
563 _phase_timings(nullptr),
564 _evac_tracker(new ShenandoahEvacuationTracker()),
565 _mmu_tracker(),
566 _generation_sizer(&_mmu_tracker),
567 _monitoring_support(nullptr),
568 _memory_pool(nullptr),
569 _young_gen_memory_pool(nullptr),
570 _old_gen_memory_pool(nullptr),
571 _stw_memory_manager("Shenandoah Pauses", "end of GC pause"),
572 _cycle_memory_manager("Shenandoah Cycles", "end of GC cycle"),
573 _gc_timer(new ConcurrentGCTimer()),
574 _soft_ref_policy(),
575 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
576 _marking_context(nullptr),
577 _bitmap_size(0),
578 _bitmap_regions_per_slice(0),
579 _bitmap_bytes_per_slice(0),
580 _bitmap_region_special(false),
581 _aux_bitmap_region_special(false),
582 _liveness_cache(nullptr),
583 _collection_set(nullptr),
584 _card_scan(nullptr)
585 {
586 }
587
588 #ifdef _MSC_VER
589 #pragma warning( pop )
590 #endif
591
592 void ShenandoahHeap::print_on(outputStream* st) const {
593 st->print_cr("Shenandoah Heap");
594 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
595 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
596 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
597 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
598 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
599 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
600 num_regions(),
601 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
602 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
603
604 st->print("Status: ");
605 if (has_forwarded_objects()) st->print("has forwarded objects, ");
606 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
607 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
608 if (is_evacuation_in_progress()) st->print("evacuating, ");
609 if (is_update_refs_in_progress()) st->print("updating refs, ");
610 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
611 if (is_full_gc_in_progress()) st->print("full gc, ");
612 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
613 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
614 if (is_concurrent_strong_root_in_progress() &&
615 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
616
617 if (cancelled_gc()) {
618 st->print("cancelled");
619 } else {
620 st->print("not cancelled");
621 }
622 st->cr();
623
624 st->print_cr("Reserved region:");
625 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
626 p2i(reserved_region().start()),
627 p2i(reserved_region().end()));
628
629 ShenandoahCollectionSet* cset = collection_set();
630 st->print_cr("Collection set:");
631 if (cset != nullptr) {
632 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
633 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
634 } else {
635 st->print_cr(" (null)");
636 }
637
638 st->cr();
639 MetaspaceUtils::print_on(st);
640
641 if (Verbose) {
642 print_heap_regions_on(st);
643 }
644 }
645
646 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
647 public:
648 void do_thread(Thread* thread) {
649 assert(thread != nullptr, "Sanity");
650 assert(thread->is_Worker_thread(), "Only worker thread expected");
651 ShenandoahThreadLocalData::initialize_gclab(thread);
652 }
653 };
654
655 void ShenandoahHeap::post_initialize() {
656 CollectedHeap::post_initialize();
657 _mmu_tracker.initialize();
658
659 MutexLocker ml(Threads_lock);
660
661 ShenandoahInitWorkerGCLABClosure init_gclabs;
662 _workers->threads_do(&init_gclabs);
663
664 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
665 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
666 _workers->set_initialize_gclab();
667 if (_safepoint_workers != nullptr) {
668 _safepoint_workers->threads_do(&init_gclabs);
669 _safepoint_workers->set_initialize_gclab();
670 }
671
672 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
673 }
674
675
676 ShenandoahOldHeuristics* ShenandoahHeap::old_heuristics() {
677 return (ShenandoahOldHeuristics*) _old_generation->heuristics();
678 }
679
680 bool ShenandoahHeap::doing_mixed_evacuations() {
681 return old_heuristics()->unprocessed_old_collection_candidates() > 0;
682 }
683
684 bool ShenandoahHeap::is_old_bitmap_stable() const {
685 ShenandoahOldGeneration::State state = _old_generation->state();
686 return state != ShenandoahOldGeneration::MARKING
687 && state != ShenandoahOldGeneration::BOOTSTRAPPING;
688 }
689
690 bool ShenandoahHeap::is_gc_generation_young() const {
691 return _gc_generation != nullptr && _gc_generation->generation_mode() == YOUNG;
692 }
693
694 size_t ShenandoahHeap::used() const {
695 return Atomic::load(&_used);
696 }
697
698 size_t ShenandoahHeap::committed() const {
699 return Atomic::load(&_committed);
700 }
701
702 void ShenandoahHeap::increase_committed(size_t bytes) {
703 shenandoah_assert_heaplocked_or_safepoint();
704 _committed += bytes;
705 }
706
707 void ShenandoahHeap::decrease_committed(size_t bytes) {
708 shenandoah_assert_heaplocked_or_safepoint();
709 _committed -= bytes;
710 }
711
712 void ShenandoahHeap::increase_used(size_t bytes) {
713 Atomic::add(&_used, bytes, memory_order_relaxed);
714 }
715
716 void ShenandoahHeap::set_used(size_t bytes) {
717 Atomic::store(&_used, bytes);
718 }
719
720 void ShenandoahHeap::decrease_used(size_t bytes) {
721 assert(used() >= bytes, "never decrease heap size by more than we've left");
722 Atomic::sub(&_used, bytes, memory_order_relaxed);
723 }
724
725 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
726 size_t bytes = words * HeapWordSize;
727 if (!waste) {
728 increase_used(bytes);
729 }
730
731 if (ShenandoahPacing) {
732 control_thread()->pacing_notify_alloc(words);
733 if (waste) {
734 pacer()->claim_for_alloc(words, true);
735 }
736 }
737 }
738
739 size_t ShenandoahHeap::capacity() const {
740 return committed();
741 }
742
743 size_t ShenandoahHeap::max_capacity() const {
744 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
745 }
746
747 size_t ShenandoahHeap::soft_max_capacity() const {
748 size_t v = Atomic::load(&_soft_max_size);
749 assert(min_capacity() <= v && v <= max_capacity(),
750 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
751 min_capacity(), v, max_capacity());
752 return v;
753 }
754
755 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
756 assert(min_capacity() <= v && v <= max_capacity(),
757 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
758 min_capacity(), v, max_capacity());
759 Atomic::store(&_soft_max_size, v);
760
761 if (mode()->is_generational()) {
762 _generation_sizer.heap_size_changed(_soft_max_size);
763 size_t soft_max_capacity_young = _generation_sizer.max_young_size();
764 size_t soft_max_capacity_old = _soft_max_size - soft_max_capacity_young;
765 _young_generation->set_soft_max_capacity(soft_max_capacity_young);
766 _old_generation->set_soft_max_capacity(soft_max_capacity_old);
767 }
768 }
769
770 size_t ShenandoahHeap::min_capacity() const {
771 return _minimum_size;
772 }
773
774 size_t ShenandoahHeap::initial_capacity() const {
775 return _initial_size;
776 }
777
778 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
779 assert (ShenandoahUncommit, "should be enabled");
780
781 // Application allocates from the beginning of the heap, and GC allocates at
782 // the end of it. It is more efficient to uncommit from the end, so that applications
783 // could enjoy the near committed regions. GC allocations are much less frequent,
784 // and therefore can accept the committing costs.
785
786 size_t count = 0;
787 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
788 ShenandoahHeapRegion* r = get_region(i - 1);
789 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
790 ShenandoahHeapLocker locker(lock());
791 if (r->is_empty_committed()) {
792 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
793 break;
794 }
795
796 r->make_uncommitted();
797 count++;
798 }
799 }
800 SpinPause(); // allow allocators to take the lock
801 }
802
803 if (count > 0) {
804 control_thread()->notify_heap_changed();
805 regulator_thread()->notify_heap_changed();
806 }
807 }
808
809 void ShenandoahHeap::handle_old_evacuation(HeapWord* obj, size_t words, bool promotion) {
810 // Only register the copy of the object that won the evacuation race.
811 card_scan()->register_object_wo_lock(obj);
812
813 // Mark the entire range of the evacuated object as dirty. At next remembered set scan,
814 // we will clear dirty bits that do not hold interesting pointers. It's more efficient to
815 // do this in batch, in a background GC thread than to try to carefully dirty only cards
816 // that hold interesting pointers right now.
817 card_scan()->mark_range_as_dirty(obj, words);
818
819 if (promotion) {
820 // This evacuation was a promotion, track this as allocation against old gen
821 old_generation()->increase_allocated(words * HeapWordSize);
822 }
823 }
824
825 void ShenandoahHeap::handle_old_evacuation_failure() {
826 if (_old_gen_oom_evac.try_set()) {
827 log_info(gc)("Old gen evac failure.");
828 }
829 }
830
831 void ShenandoahHeap::handle_promotion_failure() {
832 old_heuristics()->handle_promotion_failure();
833 }
834
835 void ShenandoahHeap::report_promotion_failure(Thread* thread, size_t size) {
836 // We squelch excessive reports to reduce noise in logs. Squelch enforcement is not "perfect" because
837 // this same code can be in-lined in multiple contexts, and each context will have its own copy of the static
838 // last_report_epoch and this_epoch_report_count variables.
839 const size_t MaxReportsPerEpoch = 4;
840 static size_t last_report_epoch = 0;
841 static size_t epoch_report_count = 0;
842
843 size_t promotion_reserve;
844 size_t promotion_expended;
845
846 size_t gc_id = control_thread()->get_gc_id();
847
848 if ((gc_id != last_report_epoch) || (epoch_report_count++ < MaxReportsPerEpoch)) {
849 {
850 // Promotion failures should be very rare. Invest in providing useful diagnostic info.
851 ShenandoahHeapLocker locker(lock());
852 promotion_reserve = get_promoted_reserve();
853 promotion_expended = get_promoted_expended();
854 }
855 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
856 size_t words_remaining = (plab == nullptr)? 0: plab->words_remaining();
857 const char* promote_enabled = ShenandoahThreadLocalData::allow_plab_promotions(thread)? "enabled": "disabled";
858
859 log_info(gc, ergo)("Promotion failed, size " SIZE_FORMAT ", has plab? %s, PLAB remaining: " SIZE_FORMAT
860 ", plab promotions %s, promotion reserve: " SIZE_FORMAT ", promotion expended: " SIZE_FORMAT,
861 size, plab == nullptr? "no": "yes",
862 words_remaining, promote_enabled, promotion_reserve, promotion_expended);
863 if ((gc_id == last_report_epoch) && (epoch_report_count >= MaxReportsPerEpoch)) {
864 log_info(gc, ergo)("Squelching additional promotion failure reports for current epoch");
865 } else if (gc_id != last_report_epoch) {
866 last_report_epoch = gc_id;;
867 epoch_report_count = 1;
868 }
869 }
870 }
871
872 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
873 // New object should fit the GCLAB size
874 size_t min_size = MAX2(size, PLAB::min_size());
875
876 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
877 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
878
879 // Limit growth of GCLABs to ShenandoahMaxEvacLABRatio * the minimum size. This enables more equitable distribution of
880 // available evacuation buidget between the many threads that are coordinating in the evacuation effort.
881 if (ShenandoahMaxEvacLABRatio > 0) {
882 log_debug(gc, free)("Allocate new gclab: " SIZE_FORMAT ", " SIZE_FORMAT, new_size, PLAB::min_size() * ShenandoahMaxEvacLABRatio);
883 new_size = MIN2(new_size, PLAB::min_size() * ShenandoahMaxEvacLABRatio);
884 }
885
886 new_size = MIN2(new_size, PLAB::max_size());
887 new_size = MAX2(new_size, PLAB::min_size());
888
889 // Record new heuristic value even if we take any shortcut. This captures
890 // the case when moderately-sized objects always take a shortcut. At some point,
891 // heuristics should catch up with them.
892 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
893
894 if (new_size < size) {
895 // New size still does not fit the object. Fall back to shared allocation.
896 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
897 log_debug(gc, free)("New gclab size (" SIZE_FORMAT ") is too small for " SIZE_FORMAT, new_size, size);
898 return nullptr;
899 }
900
901 // Retire current GCLAB, and allocate a new one.
902 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
903 gclab->retire();
904
905 size_t actual_size = 0;
906 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
907 if (gclab_buf == nullptr) {
908 return nullptr;
909 }
910
911 assert (size <= actual_size, "allocation should fit");
912
913 if (ZeroTLAB) {
914 // ..and clear it.
915 Copy::zero_to_words(gclab_buf, actual_size);
916 } else {
917 // ...and zap just allocated object.
918 #ifdef ASSERT
919 // Skip mangling the space corresponding to the object header to
920 // ensure that the returned space is not considered parsable by
921 // any concurrent GC thread.
922 size_t hdr_size = oopDesc::header_size();
923 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
924 #endif // ASSERT
925 }
926 gclab->set_buf(gclab_buf, actual_size);
927 return gclab->allocate(size);
928 }
929
930 // Establish a new PLAB and allocate size HeapWords within it.
931 HeapWord* ShenandoahHeap::allocate_from_plab_slow(Thread* thread, size_t size, bool is_promotion) {
932 // New object should fit the PLAB size
933 size_t min_size = MAX2(size, PLAB::min_size());
934
935 // Figure out size of new PLAB, looking back at heuristics. Expand aggressively.
936 size_t cur_size = ShenandoahThreadLocalData::plab_size(thread);
937 if (cur_size == 0) {
938 cur_size = PLAB::min_size();
939 }
940 size_t future_size = cur_size * 2;
941 // Limit growth of PLABs to ShenandoahMaxEvacLABRatio * the minimum size. This enables more equitable distribution of
942 // available evacuation buidget between the many threads that are coordinating in the evacuation effort.
943 if (ShenandoahMaxEvacLABRatio > 0) {
944 future_size = MIN2(future_size, PLAB::min_size() * ShenandoahMaxEvacLABRatio);
945 }
946 future_size = MIN2(future_size, PLAB::max_size());
947 future_size = MAX2(future_size, PLAB::min_size());
948
949 size_t unalignment = future_size % CardTable::card_size_in_words();
950 if (unalignment != 0) {
951 future_size = future_size - unalignment + CardTable::card_size_in_words();
952 }
953
954 // Record new heuristic value even if we take any shortcut. This captures
955 // the case when moderately-sized objects always take a shortcut. At some point,
956 // heuristics should catch up with them. Note that the requested cur_size may
957 // not be honored, but we remember that this is the preferred size.
958 ShenandoahThreadLocalData::set_plab_size(thread, future_size);
959 if (cur_size < size) {
960 // The PLAB to be allocated is still not large enough to hold the object. Fall back to shared allocation.
961 // This avoids retiring perfectly good PLABs in order to represent a single large object allocation.
962 return nullptr;
963 }
964
965 // Retire current PLAB, and allocate a new one.
966 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
967 if (plab->words_remaining() < PLAB::min_size()) {
968 // Retire current PLAB, and allocate a new one.
969 // CAUTION: retire_plab may register the remnant filler object with the remembered set scanner without a lock. This
970 // is safe iff it is assured that each PLAB is a whole-number multiple of card-mark memory size and each PLAB is
971 // aligned with the start of a card's memory range.
972
973 retire_plab(plab, thread);
974
975 size_t actual_size = 0;
976 // allocate_new_plab resets plab_evacuated and plab_promoted and disables promotions if old-gen available is
977 // less than the remaining evacuation need. It also adjusts plab_preallocated and expend_promoted if appropriate.
978 HeapWord* plab_buf = allocate_new_plab(min_size, cur_size, &actual_size);
979 if (plab_buf == nullptr) {
980 return nullptr;
981 } else {
982 ShenandoahThreadLocalData::enable_plab_retries(thread);
983 }
984 assert (size <= actual_size, "allocation should fit");
985 if (ZeroTLAB) {
986 // ..and clear it.
987 Copy::zero_to_words(plab_buf, actual_size);
988 } else {
989 // ...and zap just allocated object.
990 #ifdef ASSERT
991 // Skip mangling the space corresponding to the object header to
992 // ensure that the returned space is not considered parsable by
993 // any concurrent GC thread.
994 size_t hdr_size = oopDesc::header_size();
995 Copy::fill_to_words(plab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
996 #endif // ASSERT
997 }
998 plab->set_buf(plab_buf, actual_size);
999
1000 if (is_promotion && !ShenandoahThreadLocalData::allow_plab_promotions(thread)) {
1001 return nullptr;
1002 }
1003 return plab->allocate(size);
1004 } else {
1005 // If there's still at least min_size() words available within the current plab, don't retire it. Let's gnaw
1006 // away on this plab as long as we can. Meanwhile, return nullptr to force this particular allocation request
1007 // to be satisfied with a shared allocation. By packing more promotions into the previously allocated PLAB, we
1008 // reduce the likelihood of evacuation failures, and we we reduce the need for downsizing our PLABs.
1009 return nullptr;
1010 }
1011 }
1012
1013 // TODO: It is probably most efficient to register all objects (both promotions and evacuations) that were allocated within
1014 // this plab at the time we retire the plab. A tight registration loop will run within both code and data caches. This change
1015 // would allow smaller and faster in-line implementation of alloc_from_plab(). Since plabs are aligned on card-table boundaries,
1016 // this object registration loop can be performed without acquiring a lock.
1017 void ShenandoahHeap::retire_plab(PLAB* plab, Thread* thread) {
1018 // We don't enforce limits on plab_evacuated. We let it consume all available old-gen memory in order to reduce
1019 // probability of an evacuation failure. We do enforce limits on promotion, to make sure that excessive promotion
1020 // does not result in an old-gen evacuation failure. Note that a failed promotion is relatively harmless. Any
1021 // object that fails to promote in the current cycle will be eligible for promotion in a subsequent cycle.
1022
1023 // When the plab was instantiated, its entirety was treated as if the entire buffer was going to be dedicated to
1024 // promotions. Now that we are retiring the buffer, we adjust for the reality that the plab is not entirely promotions.
1025 // 1. Some of the plab may have been dedicated to evacuations.
1026 // 2. Some of the plab may have been abandoned due to waste (at the end of the plab).
1027 size_t not_promoted =
1028 ShenandoahThreadLocalData::get_plab_preallocated_promoted(thread) - ShenandoahThreadLocalData::get_plab_promoted(thread);
1029 ShenandoahThreadLocalData::reset_plab_promoted(thread);
1030 ShenandoahThreadLocalData::reset_plab_evacuated(thread);
1031 ShenandoahThreadLocalData::set_plab_preallocated_promoted(thread, 0);
1032 if (not_promoted > 0) {
1033 unexpend_promoted(not_promoted);
1034 }
1035 size_t waste = plab->waste();
1036 HeapWord* top = plab->top();
1037 plab->retire();
1038 if (top != nullptr && plab->waste() > waste && is_in_old(top)) {
1039 // If retiring the plab created a filler object, then we
1040 // need to register it with our card scanner so it can
1041 // safely walk the region backing the plab.
1042 log_debug(gc)("retire_plab() is registering remnant of size " SIZE_FORMAT " at " PTR_FORMAT,
1043 plab->waste() - waste, p2i(top));
1044 card_scan()->register_object_wo_lock(top);
1045 }
1046 }
1047
1048 void ShenandoahHeap::retire_plab(PLAB* plab) {
1049 Thread* thread = Thread::current();
1050 retire_plab(plab, thread);
1051 }
1052
1053 void ShenandoahHeap::cancel_old_gc() {
1054 shenandoah_assert_safepoint();
1055 assert(_old_generation != nullptr, "Should only have mixed collections in generation mode.");
1056 log_info(gc)("Terminating old gc cycle.");
1057
1058 // Stop marking
1059 old_generation()->cancel_marking();
1060 // Stop coalescing undead objects
1061 set_prepare_for_old_mark_in_progress(false);
1062 // Stop tracking old regions
1063 old_heuristics()->abandon_collection_candidates();
1064 // Remove old generation access to young generation mark queues
1065 young_generation()->set_old_gen_task_queues(nullptr);
1066 // Transition to IDLE now.
1067 _old_generation->transition_to(ShenandoahOldGeneration::IDLE);
1068 }
1069
1070 bool ShenandoahHeap::is_old_gc_active() {
1071 return is_concurrent_old_mark_in_progress()
1072 || is_prepare_for_old_mark_in_progress()
1073 || old_heuristics()->unprocessed_old_collection_candidates() > 0
1074 || young_generation()->old_gen_task_queues() != nullptr;
1075 }
1076
1077 void ShenandoahHeap::coalesce_and_fill_old_regions() {
1078 class ShenandoahGlobalCoalesceAndFill : public ShenandoahHeapRegionClosure {
1079 public:
1080 virtual void heap_region_do(ShenandoahHeapRegion* region) override {
1081 // old region is not in the collection set and was not immediately trashed
1082 if (region->is_old() && region->is_active() && !region->is_humongous()) {
1083 // Reset the coalesce and fill boundary because this is a global collect
1084 // and cannot be preempted by young collects. We want to be sure the entire
1085 // region is coalesced here and does not resume from a previously interrupted
1086 // or completed coalescing.
1087 region->begin_preemptible_coalesce_and_fill();
1088 region->oop_fill_and_coalesce();
1089 }
1090 }
1091
1092 virtual bool is_thread_safe() override {
1093 return true;
1094 }
1095 };
1096 ShenandoahGlobalCoalesceAndFill coalesce;
1097 parallel_heap_region_iterate(&coalesce);
1098 }
1099
1100 bool ShenandoahHeap::adjust_generation_sizes() {
1101 if (mode()->is_generational()) {
1102 return _generation_sizer.adjust_generation_sizes();
1103 }
1104 return false;
1105 }
1106
1107 // Called from stubs in JIT code or interpreter
1108 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
1109 size_t requested_size,
1110 size_t* actual_size) {
1111 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
1112 HeapWord* res = allocate_memory(req, false);
1113 if (res != nullptr) {
1114 *actual_size = req.actual_size();
1115 } else {
1116 *actual_size = 0;
1117 }
1118 return res;
1119 }
1120
1121 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
1122 size_t word_size,
1123 size_t* actual_size) {
1124 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
1125 HeapWord* res = allocate_memory(req, false);
1126 if (res != nullptr) {
1127 *actual_size = req.actual_size();
1128 } else {
1129 *actual_size = 0;
1130 }
1131 return res;
1132 }
1133
1134 HeapWord* ShenandoahHeap::allocate_new_plab(size_t min_size,
1135 size_t word_size,
1136 size_t* actual_size) {
1137 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_plab(min_size, word_size);
1138 // Note that allocate_memory() sets a thread-local flag to prohibit further promotions by this thread
1139 // if we are at risk of exceeding the old-gen evacuation budget.
1140 HeapWord* res = allocate_memory(req, false);
1141 if (res != nullptr) {
1142 *actual_size = req.actual_size();
1143 } else {
1144 *actual_size = 0;
1145 }
1146 return res;
1147 }
1148
1149 // is_promotion is true iff this allocation is known for sure to hold the result of young-gen evacuation
1150 // to old-gen. plab allocates are not known as such, since they may hold old-gen evacuations.
1151 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req, bool is_promotion) {
1152 intptr_t pacer_epoch = 0;
1153 bool in_new_region = false;
1154 HeapWord* result = nullptr;
1155
1156 if (req.is_mutator_alloc()) {
1157 if (ShenandoahPacing) {
1158 pacer()->pace_for_alloc(req.size());
1159 pacer_epoch = pacer()->epoch();
1160 }
1161
1162 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
1163 result = allocate_memory_under_lock(req, in_new_region, is_promotion);
1164 }
1165
1166 // Allocation failed, block until control thread reacted, then retry allocation.
1167 //
1168 // It might happen that one of the threads requesting allocation would unblock
1169 // way later after GC happened, only to fail the second allocation, because
1170 // other threads have already depleted the free storage. In this case, a better
1171 // strategy is to try again, as long as GC makes progress.
1172 //
1173 // Then, we need to make sure the allocation was retried after at least one
1174 // Full GC, which means we want to try more than ShenandoahFullGCThreshold times.
1175 size_t tries = 0;
1176 while (result == nullptr && _progress_last_gc.is_set()) {
1177 tries++;
1178 control_thread()->handle_alloc_failure(req);
1179 result = allocate_memory_under_lock(req, in_new_region, is_promotion);
1180 }
1181 while (result == nullptr && tries <= ShenandoahFullGCThreshold) {
1182 tries++;
1183 control_thread()->handle_alloc_failure(req);
1184 result = allocate_memory_under_lock(req, in_new_region, is_promotion);
1185 }
1186 } else {
1187 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
1188 result = allocate_memory_under_lock(req, in_new_region, is_promotion);
1189 // Do not call handle_alloc_failure() here, because we cannot block.
1190 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1191 }
1192
1193 if (in_new_region) {
1194 control_thread()->notify_heap_changed();
1195 regulator_thread()->notify_heap_changed();
1196 }
1197
1198 if (result != nullptr) {
1199 ShenandoahGeneration* alloc_generation = generation_for(req.affiliation());
1200 size_t requested = req.size();
1201 size_t actual = req.actual_size();
1202 size_t actual_bytes = actual * HeapWordSize;
1203
1204 assert (req.is_lab_alloc() || (requested == actual),
1205 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
1206 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
1207
1208 if (req.is_mutator_alloc()) {
1209 notify_mutator_alloc_words(actual, false);
1210 alloc_generation->increase_allocated(actual_bytes);
1211
1212 // If we requested more than we were granted, give the rest back to pacer.
1213 // This only matters if we are in the same pacing epoch: do not try to unpace
1214 // over the budget for the other phase.
1215 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
1216 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
1217 }
1218 } else {
1219 increase_used(actual_bytes);
1220 }
1221 }
1222
1223 return result;
1224 }
1225
1226 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region, bool is_promotion) {
1227 bool try_smaller_lab_size = false;
1228 size_t smaller_lab_size;
1229 {
1230 // promotion_eligible pertains only to PLAB allocations, denoting that the PLAB is allowed to allocate for promotions.
1231 bool promotion_eligible = false;
1232 bool allow_allocation = true;
1233 bool plab_alloc = false;
1234 size_t requested_bytes = req.size() * HeapWordSize;
1235 HeapWord* result = nullptr;
1236 ShenandoahHeapLocker locker(lock());
1237 Thread* thread = Thread::current();
1238
1239 if (mode()->is_generational()) {
1240 if (req.affiliation() == YOUNG_GENERATION) {
1241 if (req.is_mutator_alloc()) {
1242 size_t young_available = young_generation()->adjusted_available();
1243 if (requested_bytes > young_available) {
1244 // We know this is not a GCLAB. This must be a TLAB or a shared allocation.
1245 if (req.is_lab_alloc() && (young_available >= req.min_size())) {
1246 try_smaller_lab_size = true;
1247 smaller_lab_size = young_available / HeapWordSize;
1248 } else {
1249 // Can't allocate because even min_size() is larger than remaining young_available
1250 log_info(gc, ergo)("Unable to shrink %s alloc request of minimum size: " SIZE_FORMAT
1251 ", young available: " SIZE_FORMAT,
1252 req.is_lab_alloc()? "TLAB": "shared",
1253 HeapWordSize * (req.is_lab_alloc()? req.min_size(): req.size()), young_available);
1254 return nullptr;
1255 }
1256 }
1257 }
1258 } else { // reg.affiliation() == OLD_GENERATION
1259 assert(req.type() != ShenandoahAllocRequest::_alloc_gclab, "GCLAB pertains only to young-gen memory");
1260 if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
1261 plab_alloc = true;
1262 size_t promotion_avail = get_promoted_reserve();
1263 size_t promotion_expended = get_promoted_expended();
1264 if (promotion_expended + requested_bytes > promotion_avail) {
1265 promotion_avail = 0;
1266 if (get_old_evac_reserve() == 0) {
1267 // There are no old-gen evacuations in this pass. There's no value in creating a plab that cannot
1268 // be used for promotions.
1269 allow_allocation = false;
1270 }
1271 } else {
1272 promotion_avail = promotion_avail - (promotion_expended + requested_bytes);
1273 promotion_eligible = true;
1274 }
1275 } else if (is_promotion) {
1276 // This is a shared alloc for promotion
1277 size_t promotion_avail = get_promoted_reserve();
1278 size_t promotion_expended = get_promoted_expended();
1279 if (promotion_expended + requested_bytes > promotion_avail) {
1280 promotion_avail = 0;
1281 } else {
1282 promotion_avail = promotion_avail - (promotion_expended + requested_bytes);
1283 }
1284 if (promotion_avail == 0) {
1285 // We need to reserve the remaining memory for evacuation. Reject this allocation. The object will be
1286 // evacuated to young-gen memory and promoted during a future GC pass.
1287 return nullptr;
1288 }
1289 // Else, we'll allow the allocation to proceed. (Since we hold heap lock, the tested condition remains true.)
1290 } else {
1291 // This is a shared allocation for evacuation. Memory has already been reserved for this purpose.
1292 }
1293 }
1294 } // This ends the is_generational() block
1295
1296 if (!try_smaller_lab_size) {
1297 result = (allow_allocation)? _free_set->allocate(req, in_new_region): nullptr;
1298 if (result != nullptr) {
1299 if (req.affiliation() == ShenandoahRegionAffiliation::OLD_GENERATION) {
1300 ShenandoahThreadLocalData::reset_plab_promoted(thread);
1301 if (req.is_gc_alloc()) {
1302 if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
1303 if (promotion_eligible) {
1304 size_t actual_size = req.actual_size() * HeapWordSize;
1305 // Assume the entirety of this PLAB will be used for promotion. This prevents promotion from overreach.
1306 // When we retire this plab, we'll unexpend what we don't really use.
1307 ShenandoahThreadLocalData::enable_plab_promotions(thread);
1308 expend_promoted(actual_size);
1309 assert(get_promoted_expended() <= get_promoted_reserve(), "Do not expend more promotion than budgeted");
1310 ShenandoahThreadLocalData::set_plab_preallocated_promoted(thread, actual_size);
1311 } else {
1312 // Disable promotions in this thread because entirety of this PLAB must be available to hold old-gen evacuations.
1313 ShenandoahThreadLocalData::disable_plab_promotions(thread);
1314 ShenandoahThreadLocalData::set_plab_preallocated_promoted(thread, 0);
1315 }
1316 } else if (is_promotion) {
1317 // Shared promotion. Assume size is requested_bytes.
1318 expend_promoted(requested_bytes);
1319 assert(get_promoted_expended() <= get_promoted_reserve(), "Do not expend more promotion than budgeted");
1320 }
1321 }
1322
1323 // Register the newly allocated object while we're holding the global lock since there's no synchronization
1324 // built in to the implementation of register_object(). There are potential races when multiple independent
1325 // threads are allocating objects, some of which might span the same card region. For example, consider
1326 // a card table's memory region within which three objects are being allocated by three different threads:
1327 //
1328 // objects being "concurrently" allocated:
1329 // [-----a------][-----b-----][--------------c------------------]
1330 // [---- card table memory range --------------]
1331 //
1332 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a
1333 // wants to set the has-object, first-start, and last-start attributes of the preceding card region.
1334 // allocation of object b wants to set the has-object, first-start, and last-start attributes of this card region.
1335 // allocation of object c also wants to set the has-object, first-start, and last-start attributes of this card region.
1336 //
1337 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as
1338 // last-start representing object b while first-start represents object c. This is why we need to require all
1339 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range.
1340 ShenandoahHeap::heap()->card_scan()->register_object(result);
1341 }
1342 } else {
1343 // The allocation failed. If this was a plab allocation, We've already retired it and no longer have a plab.
1344 if ((req.affiliation() == ShenandoahRegionAffiliation::OLD_GENERATION) && req.is_gc_alloc() &&
1345 (req.type() == ShenandoahAllocRequest::_alloc_plab)) {
1346 // We don't need to disable PLAB promotions because there is no PLAB. We leave promotions enabled because
1347 // this allows the surrounding infrastructure to retry alloc_plab_slow() with a smaller PLAB size.
1348 ShenandoahThreadLocalData::set_plab_preallocated_promoted(thread, 0);
1349 }
1350 }
1351 return result;
1352 }
1353 // else, try_smaller_lab_size is true so we fall through and recurse with a smaller lab size
1354 } // This closes the block that holds the heap lock. This releases the lock.
1355
1356 // We arrive here if the tlab allocation request can be resized to fit within young_available
1357 assert((req.affiliation() == YOUNG_GENERATION) && req.is_lab_alloc() && req.is_mutator_alloc() &&
1358 (smaller_lab_size < req.size()), "Only shrink allocation request size for TLAB allocations");
1359
1360 // By convention, ShenandoahAllocationRequest is primarily read-only. The only mutable instance data is represented by
1361 // actual_size(), which is overwritten with the size of the allocaion when the allocation request is satisfied. We use a
1362 // recursive call here rather than introducing new methods to mutate the existing ShenandoahAllocationRequest argument.
1363 // Mutation of the existing object might result in astonishing results if calling contexts assume the content of immutable
1364 // fields remain constant. The original TLAB allocation request was for memory that exceeded the current capacity. We'll
1365 // attempt to allocate a smaller TLAB. If this is successful, we'll update actual_size() of our incoming
1366 // ShenandoahAllocRequest. If the recursive request fails, we'll simply return nullptr.
1367
1368 // Note that we've relinquished the HeapLock and some other thread may perform additional allocation before our recursive
1369 // call reacquires the lock. If that happens, we will need another recursive call to further reduce the size of our request
1370 // for each time another thread allocates young memory during the brief intervals that the heap lock is available to
1371 // interfering threads. We expect this interference to be rare. The recursion bottoms out when young_available is
1372 // smaller than req.min_size(). The inner-nested call to allocate_memory_under_lock() uses the same min_size() value
1373 // as this call, but it uses a preferred size() that is smaller than our preferred size, and is no larger than what we most
1374 // recently saw as the memory currently available within the young generation.
1375
1376 // TODO: At the expense of code clarity, we could rewrite this recursive solution to use iteration. We need at most one
1377 // extra instance of the ShenandoahAllocRequest, which we can re-initialize multiple times inside a loop, with one iteration
1378 // of the loop required for each time the existing solution would recurse. An iterative solution would be more efficient
1379 // in CPU time and stack memory utilization. The expectation is that it is very rare that we would recurse more than once
1380 // so making this change is not currently seen as a high priority.
1381
1382 ShenandoahAllocRequest smaller_req = ShenandoahAllocRequest::for_tlab(req.min_size(), smaller_lab_size);
1383
1384 // Note that shrinking the preferred size gets us past the gatekeeper that checks whether there's available memory to
1385 // satisfy the allocation request. The reality is the actual TLAB size is likely to be even smaller, because it will
1386 // depend on how much memory is available within mutator regions that are not yet fully used.
1387 HeapWord* result = allocate_memory_under_lock(smaller_req, in_new_region, is_promotion);
1388 if (result != nullptr) {
1389 req.set_actual_size(smaller_req.actual_size());
1390 }
1391 return result;
1392 }
1393
1394 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1395 bool* gc_overhead_limit_was_exceeded) {
1396 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1397 return allocate_memory(req, false);
1398 }
1399
1400 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1401 size_t size,
1402 Metaspace::MetadataType mdtype) {
1403 MetaWord* result;
1404
1405 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1406 ShenandoahHeuristics* h = global_generation()->heuristics();
1407 if (h->can_unload_classes()) {
1408 h->record_metaspace_oom();
1409 }
1410
1411 // Expand and retry allocation
1412 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1413 if (result != nullptr) {
1414 return result;
1415 }
1416
1417 // Start full GC
1418 collect(GCCause::_metadata_GC_clear_soft_refs);
1419
1420 // Retry allocation
1421 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1422 if (result != nullptr) {
1423 return result;
1424 }
1425
1426 // Expand and retry allocation
1427 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1428 if (result != nullptr) {
1429 return result;
1430 }
1431
1432 // Out of memory
1433 return nullptr;
1434 }
1435
1436 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1437 private:
1438 ShenandoahHeap* const _heap;
1439 Thread* const _thread;
1440 public:
1441 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1442 _heap(heap), _thread(Thread::current()) {}
1443
1444 void do_object(oop p) {
1445 shenandoah_assert_marked(nullptr, p);
1446 if (!p->is_forwarded()) {
1447 _heap->evacuate_object(p, _thread);
1448 }
1449 }
1450 };
1451
1452 class ShenandoahEvacuationTask : public WorkerTask {
1453 private:
1454 ShenandoahHeap* const _sh;
1455 ShenandoahCollectionSet* const _cs;
1456 bool _concurrent;
1457 public:
1458 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1459 ShenandoahCollectionSet* cs,
1460 bool concurrent) :
1461 WorkerTask("Shenandoah Evacuation"),
1462 _sh(sh),
1463 _cs(cs),
1464 _concurrent(concurrent)
1465 {}
1466
1467 void work(uint worker_id) {
1468 if (_concurrent) {
1469 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1470 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
1471 ShenandoahEvacOOMScope oom_evac_scope;
1472 do_work();
1473 } else {
1474 ShenandoahParallelWorkerSession worker_session(worker_id);
1475 ShenandoahEvacOOMScope oom_evac_scope;
1476 do_work();
1477 }
1478 }
1479
1480 private:
1481 void do_work() {
1482 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1483 ShenandoahHeapRegion* r;
1484 while ((r =_cs->claim_next()) != nullptr) {
1485 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1486
1487 _sh->marked_object_iterate(r, &cl);
1488
1489 if (ShenandoahPacing) {
1490 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1491 }
1492 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1493 break;
1494 }
1495 }
1496 }
1497 };
1498
1499 // Unlike ShenandoahEvacuationTask, this iterates over all regions rather than just the collection set.
1500 // This is needed in order to promote humongous start regions if age() >= tenure threshold.
1501 class ShenandoahGenerationalEvacuationTask : public WorkerTask {
1502 private:
1503 ShenandoahHeap* const _sh;
1504 ShenandoahRegionIterator *_regions;
1505 bool _concurrent;
1506 public:
1507 ShenandoahGenerationalEvacuationTask(ShenandoahHeap* sh,
1508 ShenandoahRegionIterator* iterator,
1509 bool concurrent) :
1510 WorkerTask("Shenandoah Evacuation"),
1511 _sh(sh),
1512 _regions(iterator),
1513 _concurrent(concurrent)
1514 {}
1515
1516 void work(uint worker_id) {
1517 if (_concurrent) {
1518 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1519 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
1520 ShenandoahEvacOOMScope oom_evac_scope;
1521 do_work();
1522 } else {
1523 ShenandoahParallelWorkerSession worker_session(worker_id);
1524 ShenandoahEvacOOMScope oom_evac_scope;
1525 do_work();
1526 }
1527 }
1528
1529 private:
1530 void do_work() {
1531 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1532 ShenandoahHeapRegion* r;
1533 while ((r = _regions->next()) != nullptr) {
1534 log_debug(gc)("GenerationalEvacuationTask do_work(), looking at %s region " SIZE_FORMAT ", (age: %d) [%s, %s]",
1535 r->is_old()? "old": r->is_young()? "young": "free", r->index(), r->age(),
1536 r->is_active()? "active": "inactive",
1537 r->is_humongous()? (r->is_humongous_start()? "humongous_start": "humongous_continuation"): "regular");
1538 if (r->is_cset()) {
1539 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1540 _sh->marked_object_iterate(r, &cl);
1541 if (ShenandoahPacing) {
1542 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1543 }
1544 } else if (r->is_young() && r->is_active() && r->is_humongous_start() && (r->age() > InitialTenuringThreshold)) {
1545 // We promote humongous_start regions along with their affiliated continuations during evacuation rather than
1546 // doing this work during a safepoint. We cannot put humongous regions into the collection set because that
1547 // triggers the load-reference barrier (LRB) to copy on reference fetch.
1548 if (r->promote_humongous() == 0) {
1549 // We chose not to promote because old-gen is out of memory. Report and handle the promotion failure because
1550 // this suggests need for expanding old-gen and/or performing collection of old-gen.
1551 ShenandoahHeap* heap = ShenandoahHeap::heap();
1552 oop obj = cast_to_oop(r->bottom());
1553 size_t size = obj->size();
1554 Thread* thread = Thread::current();
1555 heap->report_promotion_failure(thread, size);
1556 heap->handle_promotion_failure();
1557 }
1558 }
1559 // else, region is free, or OLD, or not in collection set, or humongous_continuation,
1560 // or is young humongous_start that is too young to be promoted
1561
1562 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1563 break;
1564 }
1565 }
1566 }
1567 };
1568
1569 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1570 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1571 ShenandoahRegionIterator regions;
1572 ShenandoahGenerationalEvacuationTask task(this, ®ions, concurrent);
1573 workers()->run_task(&task);
1574 } else {
1575 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1576 workers()->run_task(&task);
1577 }
1578 }
1579
1580 void ShenandoahHeap::trash_cset_regions() {
1581 ShenandoahHeapLocker locker(lock());
1582
1583 ShenandoahCollectionSet* set = collection_set();
1584 ShenandoahHeapRegion* r;
1585 set->clear_current_index();
1586 while ((r = set->next()) != nullptr) {
1587 r->make_trash();
1588 }
1589 collection_set()->clear();
1590 }
1591
1592 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1593 st->print_cr("Heap Regions:");
1594 st->print_cr("EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HC=humongous continuation, CS=collection set, T=trash, P=pinned");
1595 st->print_cr("BTE=bottom/top/end, U=used, T=TLAB allocs, G=GCLAB allocs, S=shared allocs, L=live data");
1596 st->print_cr("R=root, CP=critical pins, TAMS=top-at-mark-start, UWM=update watermark");
1597 st->print_cr("SN=alloc sequence number");
1598
1599 for (size_t i = 0; i < num_regions(); i++) {
1600 get_region(i)->print_on(st);
1601 }
1602 }
1603
1604 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1605 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1606
1607 oop humongous_obj = cast_to_oop(start->bottom());
1608 size_t size = humongous_obj->size();
1609 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1610 size_t index = start->index() + required_regions - 1;
1611
1612 assert(!start->has_live(), "liveness must be zero");
1613
1614 for(size_t i = 0; i < required_regions; i++) {
1615 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1616 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1617 ShenandoahHeapRegion* region = get_region(index --);
1618
1619 assert(region->is_humongous(), "expect correct humongous start or continuation");
1620 assert(!region->is_cset(), "Humongous region should not be in collection set");
1621
1622 region->make_trash_immediate();
1623 }
1624 return required_regions;
1625 }
1626
1627 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1628 public:
1629 ShenandoahCheckCleanGCLABClosure() {}
1630 void do_thread(Thread* thread) {
1631 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1632 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1633 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1634
1635 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1636 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1637 assert(plab->words_remaining() == 0, "PLAB should not need retirement");
1638 }
1639 };
1640
1641 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1642 private:
1643 bool const _resize;
1644 public:
1645 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1646 void do_thread(Thread* thread) {
1647 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1648 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1649 gclab->retire();
1650 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1651 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1652 }
1653
1654 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1655 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1656
1657 // There are two reasons to retire all plabs between old-gen evacuation passes.
1658 // 1. We need to make the plab memory parseable by remembered-set scanning.
1659 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1660 ShenandoahHeap::heap()->retire_plab(plab, thread);
1661 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) {
1662 ShenandoahThreadLocalData::set_plab_size(thread, 0);
1663 }
1664 }
1665 };
1666
1667 void ShenandoahHeap::labs_make_parsable() {
1668 assert(UseTLAB, "Only call with UseTLAB");
1669
1670 ShenandoahRetireGCLABClosure cl(false);
1671
1672 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1673 ThreadLocalAllocBuffer& tlab = t->tlab();
1674 tlab.make_parsable();
1675 cl.do_thread(t);
1676 }
1677
1678 workers()->threads_do(&cl);
1679 }
1680
1681 void ShenandoahHeap::tlabs_retire(bool resize) {
1682 assert(UseTLAB, "Only call with UseTLAB");
1683 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1684
1685 ThreadLocalAllocStats stats;
1686
1687 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1688 ThreadLocalAllocBuffer& tlab = t->tlab();
1689 tlab.retire(&stats);
1690 if (resize) {
1691 tlab.resize();
1692 }
1693 }
1694
1695 stats.publish();
1696
1697 #ifdef ASSERT
1698 ShenandoahCheckCleanGCLABClosure cl;
1699 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1700 cl.do_thread(t);
1701 }
1702 workers()->threads_do(&cl);
1703 #endif
1704 }
1705
1706 void ShenandoahHeap::gclabs_retire(bool resize) {
1707 assert(UseTLAB, "Only call with UseTLAB");
1708 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1709
1710 ShenandoahRetireGCLABClosure cl(resize);
1711 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1712 cl.do_thread(t);
1713 }
1714 workers()->threads_do(&cl);
1715
1716 if (safepoint_workers() != nullptr) {
1717 safepoint_workers()->threads_do(&cl);
1718 }
1719 }
1720
1721 class ShenandoahTagGCLABClosure : public ThreadClosure {
1722 public:
1723 void do_thread(Thread* thread) {
1724 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1725 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1726 if (gclab->words_remaining() > 0) {
1727 ShenandoahHeapRegion* r = ShenandoahHeap::heap()->heap_region_containing(gclab->allocate(0));
1728 r->set_young_lab_flag();
1729 }
1730 }
1731 };
1732
1733 void ShenandoahHeap::set_young_lab_region_flags() {
1734 if (!UseTLAB) {
1735 return;
1736 }
1737 for (size_t i = 0; i < _num_regions; i++) {
1738 _regions[i]->clear_young_lab_flags();
1739 }
1740 ShenandoahTagGCLABClosure cl;
1741 workers()->threads_do(&cl);
1742 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1743 cl.do_thread(t);
1744 ThreadLocalAllocBuffer& tlab = t->tlab();
1745 if (tlab.end() != nullptr) {
1746 ShenandoahHeapRegion* r = heap_region_containing(tlab.start());
1747 r->set_young_lab_flag();
1748 }
1749 }
1750 }
1751
1752 // Returns size in bytes
1753 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1754 if (ShenandoahElasticTLAB) {
1755 if (mode()->is_generational()) {
1756 return MIN2(ShenandoahHeapRegion::max_tlab_size_bytes(), young_generation()->adjusted_available());
1757 } else {
1758 // With Elastic TLABs, return the max allowed size, and let the allocation path
1759 // figure out the safe size for current allocation.
1760 return ShenandoahHeapRegion::max_tlab_size_bytes();
1761 }
1762 } else {
1763 return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes());
1764 }
1765 }
1766
1767 size_t ShenandoahHeap::max_tlab_size() const {
1768 // Returns size in words
1769 return ShenandoahHeapRegion::max_tlab_size_words();
1770 }
1771
1772 void ShenandoahHeap::collect(GCCause::Cause cause) {
1773 control_thread()->request_gc(cause);
1774 }
1775
1776 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1777 //assert(false, "Shouldn't need to do full collections");
1778 }
1779
1780 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1781 ShenandoahHeapRegion* r = heap_region_containing(addr);
1782 if (r != nullptr) {
1783 return r->block_start(addr);
1784 }
1785 return nullptr;
1786 }
1787
1788 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1789 ShenandoahHeapRegion* r = heap_region_containing(addr);
1790 return r->block_is_obj(addr);
1791 }
1792
1793 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1794 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1795 }
1796
1797 void ShenandoahHeap::prepare_for_verify() {
1798 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1799 labs_make_parsable();
1800 }
1801 }
1802
1803 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1804 if (_shenandoah_policy->is_at_shutdown()) {
1805 return;
1806 }
1807
1808 tcl->do_thread(_control_thread);
1809 tcl->do_thread(_regulator_thread);
1810 workers()->threads_do(tcl);
1811 if (_safepoint_workers != nullptr) {
1812 _safepoint_workers->threads_do(tcl);
1813 }
1814 if (ShenandoahStringDedup::is_enabled()) {
1815 ShenandoahStringDedup::threads_do(tcl);
1816 }
1817 }
1818
1819 void ShenandoahHeap::print_tracing_info() const {
1820 LogTarget(Info, gc, stats) lt;
1821 if (lt.is_enabled()) {
1822 ResourceMark rm;
1823 LogStream ls(lt);
1824
1825 phase_timings()->print_global_on(&ls);
1826
1827 ls.cr();
1828 ls.cr();
1829
1830 shenandoah_policy()->print_gc_stats(&ls);
1831
1832 ls.cr();
1833
1834 evac_tracker()->print_global_on(&ls);
1835
1836 ls.cr();
1837 ls.cr();
1838 }
1839 }
1840
1841 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
1842 set_gc_cause(cause);
1843 set_gc_generation(generation);
1844
1845 shenandoah_policy()->record_cycle_start();
1846 generation->heuristics()->record_cycle_start();
1847
1848 // When a cycle starts, attribute any thread activity when the collector
1849 // is idle to the global generation.
1850 _mmu_tracker.record(global_generation());
1851 }
1852
1853 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1854 generation->heuristics()->record_cycle_end();
1855
1856 if (mode()->is_generational() &&
1857 ((generation->generation_mode() == GLOBAL) || upgraded_to_full())) {
1858 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1859 young_generation()->heuristics()->record_cycle_end();
1860 old_generation()->heuristics()->record_cycle_end();
1861 }
1862 set_gc_cause(GCCause::_no_gc);
1863
1864 // When a cycle ends, the thread activity is attributed to the respective generation
1865 _mmu_tracker.record(generation);
1866 }
1867
1868 void ShenandoahHeap::verify(VerifyOption vo) {
1869 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1870 if (ShenandoahVerify) {
1871 verifier()->verify_generic(vo);
1872 } else {
1873 // TODO: Consider allocating verification bitmaps on demand,
1874 // and turn this on unconditionally.
1875 }
1876 }
1877 }
1878 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1879 return _free_set->capacity();
1880 }
1881
1882 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1883 private:
1884 MarkBitMap* _bitmap;
1885 ShenandoahScanObjectStack* _oop_stack;
1886 ShenandoahHeap* const _heap;
1887 ShenandoahMarkingContext* const _marking_context;
1888
1889 template <class T>
1890 void do_oop_work(T* p) {
1891 T o = RawAccess<>::oop_load(p);
1892 if (!CompressedOops::is_null(o)) {
1893 oop obj = CompressedOops::decode_not_null(o);
1894 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1895 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1896 return;
1897 }
1898 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1899
1900 assert(oopDesc::is_oop(obj), "must be a valid oop");
1901 if (!_bitmap->is_marked(obj)) {
1902 _bitmap->mark(obj);
1903 _oop_stack->push(obj);
1904 }
1905 }
1906 }
1907 public:
1908 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1909 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1910 _marking_context(_heap->marking_context()) {}
1911 void do_oop(oop* p) { do_oop_work(p); }
1912 void do_oop(narrowOop* p) { do_oop_work(p); }
1913 };
1914
1915 /*
1916 * This is public API, used in preparation of object_iterate().
1917 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1918 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1919 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1920 */
1921 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1922 // No-op.
1923 }
1924
1925 /*
1926 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1927 *
1928 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1929 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1930 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1931 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1932 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1933 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1934 * wiped the bitmap in preparation for next marking).
1935 *
1936 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1937 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1938 * is allowed to report dead objects, but is not required to do so.
1939 */
1940 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1941 // Reset bitmap
1942 if (!prepare_aux_bitmap_for_iteration())
1943 return;
1944
1945 ShenandoahScanObjectStack oop_stack;
1946 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1947 // Seed the stack with root scan
1948 scan_roots_for_iteration(&oop_stack, &oops);
1949
1950 // Work through the oop stack to traverse heap
1951 while (! oop_stack.is_empty()) {
1952 oop obj = oop_stack.pop();
1953 assert(oopDesc::is_oop(obj), "must be a valid oop");
1954 cl->do_object(obj);
1955 obj->oop_iterate(&oops);
1956 }
1957
1958 assert(oop_stack.is_empty(), "should be empty");
1959 // Reclaim bitmap
1960 reclaim_aux_bitmap_for_iteration();
1961 }
1962
1963 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1964 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1965
1966 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1967 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1968 return false;
1969 }
1970 // Reset bitmap
1971 _aux_bit_map.clear();
1972 return true;
1973 }
1974
1975 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1976 // Process GC roots according to current GC cycle
1977 // This populates the work stack with initial objects
1978 // It is important to relinquish the associated locks before diving
1979 // into heap dumper
1980 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1981 ShenandoahHeapIterationRootScanner rp(n_workers);
1982 rp.roots_do(oops);
1983 }
1984
1985 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1986 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1987 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1988 }
1989 }
1990
1991 // Closure for parallelly iterate objects
1992 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1993 private:
1994 MarkBitMap* _bitmap;
1995 ShenandoahObjToScanQueue* _queue;
1996 ShenandoahHeap* const _heap;
1997 ShenandoahMarkingContext* const _marking_context;
1998
1999 template <class T>
2000 void do_oop_work(T* p) {
2001 T o = RawAccess<>::oop_load(p);
2002 if (!CompressedOops::is_null(o)) {
2003 oop obj = CompressedOops::decode_not_null(o);
2004 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
2005 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
2006 return;
2007 }
2008 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
2009
2010 assert(oopDesc::is_oop(obj), "Must be a valid oop");
2011 if (_bitmap->par_mark(obj)) {
2012 _queue->push(ShenandoahMarkTask(obj));
2013 }
2014 }
2015 }
2016 public:
2017 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
2018 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
2019 _marking_context(_heap->marking_context()) {}
2020 void do_oop(oop* p) { do_oop_work(p); }
2021 void do_oop(narrowOop* p) { do_oop_work(p); }
2022 };
2023
2024 // Object iterator for parallel heap iteraion.
2025 // The root scanning phase happenes in construction as a preparation of
2026 // parallel marking queues.
2027 // Every worker processes it's own marking queue. work-stealing is used
2028 // to balance workload.
2029 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
2030 private:
2031 uint _num_workers;
2032 bool _init_ready;
2033 MarkBitMap* _aux_bit_map;
2034 ShenandoahHeap* _heap;
2035 ShenandoahScanObjectStack _roots_stack; // global roots stack
2036 ShenandoahObjToScanQueueSet* _task_queues;
2037 public:
2038 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
2039 _num_workers(num_workers),
2040 _init_ready(false),
2041 _aux_bit_map(bitmap),
2042 _heap(ShenandoahHeap::heap()) {
2043 // Initialize bitmap
2044 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
2045 if (!_init_ready) {
2046 return;
2047 }
2048
2049 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
2050 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
2051
2052 _init_ready = prepare_worker_queues();
2053 }
2054
2055 ~ShenandoahParallelObjectIterator() {
2056 // Reclaim bitmap
2057 _heap->reclaim_aux_bitmap_for_iteration();
2058 // Reclaim queue for workers
2059 if (_task_queues!= nullptr) {
2060 for (uint i = 0; i < _num_workers; ++i) {
2061 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
2062 if (q != nullptr) {
2063 delete q;
2064 _task_queues->register_queue(i, nullptr);
2065 }
2066 }
2067 delete _task_queues;
2068 _task_queues = nullptr;
2069 }
2070 }
2071
2072 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
2073 if (_init_ready) {
2074 object_iterate_parallel(cl, worker_id, _task_queues);
2075 }
2076 }
2077
2078 private:
2079 // Divide global root_stack into worker queues
2080 bool prepare_worker_queues() {
2081 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
2082 // Initialize queues for every workers
2083 for (uint i = 0; i < _num_workers; ++i) {
2084 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
2085 _task_queues->register_queue(i, task_queue);
2086 }
2087 // Divide roots among the workers. Assume that object referencing distribution
2088 // is related with root kind, use round-robin to make every worker have same chance
2089 // to process every kind of roots
2090 size_t roots_num = _roots_stack.size();
2091 if (roots_num == 0) {
2092 // No work to do
2093 return false;
2094 }
2095
2096 for (uint j = 0; j < roots_num; j++) {
2097 uint stack_id = j % _num_workers;
2098 oop obj = _roots_stack.pop();
2099 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
2100 }
2101 return true;
2102 }
2103
2104 void object_iterate_parallel(ObjectClosure* cl,
2105 uint worker_id,
2106 ShenandoahObjToScanQueueSet* queue_set) {
2107 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
2108 assert(queue_set != nullptr, "task queue must not be null");
2109
2110 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
2111 assert(q != nullptr, "object iterate queue must not be null");
2112
2113 ShenandoahMarkTask t;
2114 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
2115
2116 // Work through the queue to traverse heap.
2117 // Steal when there is no task in queue.
2118 while (q->pop(t) || queue_set->steal(worker_id, t)) {
2119 oop obj = t.obj();
2120 assert(oopDesc::is_oop(obj), "must be a valid oop");
2121 cl->do_object(obj);
2122 obj->oop_iterate(&oops);
2123 }
2124 assert(q->is_empty(), "should be empty");
2125 }
2126 };
2127
2128 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
2129 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
2130 }
2131
2132 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
2133 void ShenandoahHeap::keep_alive(oop obj) {
2134 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
2135 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
2136 }
2137 }
2138
2139 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2140 for (size_t i = 0; i < num_regions(); i++) {
2141 ShenandoahHeapRegion* current = get_region(i);
2142 blk->heap_region_do(current);
2143 }
2144 }
2145
2146 class ShenandoahParallelHeapRegionTask : public WorkerTask {
2147 private:
2148 ShenandoahHeap* const _heap;
2149 ShenandoahHeapRegionClosure* const _blk;
2150
2151 shenandoah_padding(0);
2152 volatile size_t _index;
2153 shenandoah_padding(1);
2154
2155 public:
2156 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
2157 WorkerTask("Shenandoah Parallel Region Operation"),
2158 _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
2159
2160 void work(uint worker_id) {
2161 ShenandoahParallelWorkerSession worker_session(worker_id);
2162 size_t stride = ShenandoahParallelRegionStride;
2163
2164 size_t max = _heap->num_regions();
2165 while (Atomic::load(&_index) < max) {
2166 size_t cur = Atomic::fetch_and_add(&_index, stride, memory_order_relaxed);
2167 size_t start = cur;
2168 size_t end = MIN2(cur + stride, max);
2169 if (start >= max) break;
2170
2171 for (size_t i = cur; i < end; i++) {
2172 ShenandoahHeapRegion* current = _heap->get_region(i);
2173 _blk->heap_region_do(current);
2174 }
2175 }
2176 }
2177 };
2178
2179 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2180 assert(blk->is_thread_safe(), "Only thread-safe closures here");
2181 if (num_regions() > ShenandoahParallelRegionStride) {
2182 ShenandoahParallelHeapRegionTask task(blk);
2183 workers()->run_task(&task);
2184 } else {
2185 heap_region_iterate(blk);
2186 }
2187 }
2188
2189 class ShenandoahRendezvousClosure : public HandshakeClosure {
2190 public:
2191 inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
2192 inline void do_thread(Thread* thread) {}
2193 };
2194
2195 void ShenandoahHeap::rendezvous_threads() {
2196 ShenandoahRendezvousClosure cl;
2197 Handshake::execute(&cl);
2198 }
2199
2200 void ShenandoahHeap::recycle_trash() {
2201 free_set()->recycle_trash();
2202 }
2203
2204 void ShenandoahHeap::do_class_unloading() {
2205 _unloader.unload();
2206 }
2207
2208 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
2209 // Weak refs processing
2210 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2211 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2212 ShenandoahTimingsTracker t(phase);
2213 ShenandoahGCWorkerPhase worker_phase(phase);
2214 active_generation()->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2215 }
2216
2217 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
2218 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2219
2220 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2221 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2222 // for future GCLABs here.
2223 if (UseTLAB) {
2224 ShenandoahGCPhase phase(concurrent ?
2225 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
2226 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2227 gclabs_retire(ResizeTLAB);
2228 }
2229
2230 _update_refs_iterator.reset();
2231 }
2232
2233 void ShenandoahHeap::set_gc_state_all_threads(char state) {
2234 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
2235 ShenandoahThreadLocalData::set_gc_state(t, state);
2236 }
2237 }
2238
2239 void ShenandoahHeap::set_gc_state_mask(uint mask, bool value) {
2240 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should really be Shenandoah safepoint");
2241 _gc_state.set_cond(mask, value);
2242 set_gc_state_all_threads(_gc_state.raw_value());
2243 }
2244
2245 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2246 if (has_forwarded_objects()) {
2247 set_gc_state_mask(YOUNG_MARKING | UPDATEREFS, in_progress);
2248 } else {
2249 set_gc_state_mask(YOUNG_MARKING, in_progress);
2250 }
2251
2252 manage_satb_barrier(in_progress);
2253 }
2254
2255 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2256 if (has_forwarded_objects()) {
2257 set_gc_state_mask(OLD_MARKING | UPDATEREFS, in_progress);
2258 } else {
2259 set_gc_state_mask(OLD_MARKING, in_progress);
2260 }
2261
2262 manage_satb_barrier(in_progress);
2263 }
2264
2265 void ShenandoahHeap::set_prepare_for_old_mark_in_progress(bool in_progress) {
2266 // Unlike other set-gc-state functions, this may happen outside safepoint.
2267 // Is only set and queried by control thread, so no coherence issues.
2268 _prepare_for_old_mark = in_progress;
2269 }
2270
2271 void ShenandoahHeap::set_aging_cycle(bool in_progress) {
2272 _is_aging_cycle.set_cond(in_progress);
2273 }
2274
2275 void ShenandoahHeap::manage_satb_barrier(bool active) {
2276 if (is_concurrent_mark_in_progress()) {
2277 // Ignore request to deactivate barrier while concurrent mark is in progress.
2278 // Do not attempt to re-activate the barrier if it is already active.
2279 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2280 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2281 }
2282 } else {
2283 // No concurrent marking is in progress so honor request to deactivate,
2284 // but only if the barrier is already active.
2285 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2286 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2287 }
2288 }
2289 }
2290
2291 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2292 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2293 set_gc_state_mask(EVACUATION, in_progress);
2294 }
2295
2296 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2297 if (in_progress) {
2298 _concurrent_strong_root_in_progress.set();
2299 } else {
2300 _concurrent_strong_root_in_progress.unset();
2301 }
2302 }
2303
2304 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2305 set_gc_state_mask(WEAK_ROOTS, cond);
2306 }
2307
2308 GCTracer* ShenandoahHeap::tracer() {
2309 return shenandoah_policy()->tracer();
2310 }
2311
2312 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2313 return _free_set->used();
2314 }
2315
2316 bool ShenandoahHeap::try_cancel_gc() {
2317 while (true) {
2318 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
2319 if (prev == CANCELLABLE) return true;
2320 else if (prev == CANCELLED) return false;
2321 assert(ShenandoahSuspendibleWorkers, "should not get here when not using suspendible workers");
2322 assert(prev == NOT_CANCELLED, "must be NOT_CANCELLED");
2323 Thread* thread = Thread::current();
2324 if (thread->is_Java_thread()) {
2325 // We need to provide a safepoint here, otherwise we might
2326 // spin forever if a SP is pending.
2327 ThreadBlockInVM sp(JavaThread::cast(thread));
2328 SpinPause();
2329 }
2330 }
2331 }
2332
2333 void ShenandoahHeap::cancel_concurrent_mark() {
2334 _young_generation->cancel_marking();
2335 _old_generation->cancel_marking();
2336 _global_generation->cancel_marking();
2337
2338 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2339 }
2340
2341 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2342 if (try_cancel_gc()) {
2343 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2344 log_info(gc)("%s", msg.buffer());
2345 Events::log(Thread::current(), "%s", msg.buffer());
2346 _cancel_requested_time = os::elapsedTime();
2347 if (cause == GCCause::_shenandoah_upgrade_to_full_gc) {
2348 _upgraded_to_full = true;
2349 }
2350 }
2351 }
2352
2353 uint ShenandoahHeap::max_workers() {
2354 return _max_workers;
2355 }
2356
2357 void ShenandoahHeap::stop() {
2358 // The shutdown sequence should be able to terminate when GC is running.
2359
2360 // Step 0a. Stop requesting collections.
2361 regulator_thread()->stop();
2362
2363 // Step 0. Notify policy to disable event recording.
2364 _shenandoah_policy->record_shutdown();
2365
2366 // Step 1. Notify control thread that we are in shutdown.
2367 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
2368 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
2369 control_thread()->prepare_for_graceful_shutdown();
2370
2371 // Step 2. Notify GC workers that we are cancelling GC.
2372 cancel_gc(GCCause::_shenandoah_stop_vm);
2373
2374 // Step 3. Wait until GC worker exits normally.
2375 control_thread()->stop();
2376 }
2377
2378 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2379 if (!unload_classes()) return;
2380 // Unload classes and purge SystemDictionary.
2381 {
2382 ShenandoahPhaseTimings::Phase phase = full_gc ?
2383 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2384 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2385 ShenandoahIsAliveSelector is_alive;
2386 CodeCache::UnloadingScope scope(is_alive.is_alive_closure());
2387 ShenandoahGCPhase gc_phase(phase);
2388 ShenandoahGCWorkerPhase worker_phase(phase);
2389 bool purged_class = SystemDictionary::do_unloading(gc_timer());
2390
2391 uint num_workers = _workers->active_workers();
2392 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, purged_class);
2393 _workers->run_task(&unlink_task);
2394 }
2395
2396 {
2397 ShenandoahGCPhase phase(full_gc ?
2398 ShenandoahPhaseTimings::full_gc_purge_cldg :
2399 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2400 ClassLoaderDataGraph::purge(/*at_safepoint*/true);
2401 }
2402 // Resize and verify metaspace
2403 MetaspaceGC::compute_new_size();
2404 DEBUG_ONLY(MetaspaceUtils::verify();)
2405 }
2406
2407 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
2408 // so they should not have forwarded oops.
2409 // However, we do need to "null" dead oops in the roots, if can not be done
2410 // in concurrent cycles.
2411 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2412 uint num_workers = _workers->active_workers();
2413 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2414 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2415 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2416 ShenandoahGCPhase phase(timing_phase);
2417 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2418 // Cleanup weak roots
2419 if (has_forwarded_objects()) {
2420 ShenandoahForwardedIsAliveClosure is_alive;
2421 ShenandoahUpdateRefsClosure keep_alive;
2422 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
2423 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2424 _workers->run_task(&cleaning_task);
2425 } else {
2426 ShenandoahIsAliveClosure is_alive;
2427 #ifdef ASSERT
2428 ShenandoahAssertNotForwardedClosure verify_cl;
2429 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2430 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2431 #else
2432 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2433 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2434 #endif
2435 _workers->run_task(&cleaning_task);
2436 }
2437 }
2438
2439 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2440 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2441 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2442 ShenandoahGCPhase phase(full_gc ?
2443 ShenandoahPhaseTimings::full_gc_purge :
2444 ShenandoahPhaseTimings::degen_gc_purge);
2445 stw_weak_refs(full_gc);
2446 stw_process_weak_roots(full_gc);
2447 stw_unload_classes(full_gc);
2448 }
2449
2450 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2451 set_gc_state_mask(HAS_FORWARDED, cond);
2452 }
2453
2454 void ShenandoahHeap::set_unload_classes(bool uc) {
2455 _unload_classes.set_cond(uc);
2456 }
2457
2458 bool ShenandoahHeap::unload_classes() const {
2459 return _unload_classes.is_set();
2460 }
2461
2462 address ShenandoahHeap::in_cset_fast_test_addr() {
2463 ShenandoahHeap* heap = ShenandoahHeap::heap();
2464 assert(heap->collection_set() != nullptr, "Sanity");
2465 return (address) heap->collection_set()->biased_map_address();
2466 }
2467
2468 address ShenandoahHeap::gc_state_addr() {
2469 return (address) ShenandoahHeap::heap()->_gc_state.addr_of();
2470 }
2471
2472 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2473 if (mode()->is_generational()) {
2474 young_generation()->reset_bytes_allocated_since_gc_start();
2475 old_generation()->reset_bytes_allocated_since_gc_start();
2476 }
2477
2478 global_generation()->reset_bytes_allocated_since_gc_start();
2479 }
2480
2481 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2482 _degenerated_gc_in_progress.set_cond(in_progress);
2483 }
2484
2485 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2486 _full_gc_in_progress.set_cond(in_progress);
2487 }
2488
2489 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2490 assert (is_full_gc_in_progress(), "should be");
2491 _full_gc_move_in_progress.set_cond(in_progress);
2492 }
2493
2494 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2495 set_gc_state_mask(UPDATEREFS, in_progress);
2496 }
2497
2498 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2499 ShenandoahCodeRoots::register_nmethod(nm);
2500 }
2501
2502 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2503 ShenandoahCodeRoots::unregister_nmethod(nm);
2504 }
2505
2506 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2507 heap_region_containing(o)->record_pin();
2508 }
2509
2510 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2511 ShenandoahHeapRegion* r = heap_region_containing(o);
2512 assert(r != nullptr, "Sanity");
2513 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
2514 r->record_unpin();
2515 }
2516
2517 void ShenandoahHeap::sync_pinned_region_status() {
2518 ShenandoahHeapLocker locker(lock());
2519
2520 for (size_t i = 0; i < num_regions(); i++) {
2521 ShenandoahHeapRegion *r = get_region(i);
2522 if (r->is_active()) {
2523 if (r->is_pinned()) {
2524 if (r->pin_count() == 0) {
2525 r->make_unpinned();
2526 }
2527 } else {
2528 if (r->pin_count() > 0) {
2529 r->make_pinned();
2530 }
2531 }
2532 }
2533 }
2534
2535 assert_pinned_region_status();
2536 }
2537
2538 #ifdef ASSERT
2539 void ShenandoahHeap::assert_pinned_region_status() {
2540 for (size_t i = 0; i < num_regions(); i++) {
2541 ShenandoahHeapRegion* r = get_region(i);
2542 if (active_generation()->contains(r)) {
2543 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2544 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2545 }
2546 }
2547 }
2548 #endif
2549
2550 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2551 return _gc_timer;
2552 }
2553
2554 void ShenandoahHeap::prepare_concurrent_roots() {
2555 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2556 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2557 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2558 set_concurrent_weak_root_in_progress(true);
2559 if (unload_classes()) {
2560 _unloader.prepare();
2561 }
2562 }
2563
2564 void ShenandoahHeap::finish_concurrent_roots() {
2565 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2566 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2567 if (unload_classes()) {
2568 _unloader.finish();
2569 }
2570 }
2571
2572 #ifdef ASSERT
2573 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2574 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2575
2576 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2577 if (UseDynamicNumberOfGCThreads) {
2578 assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
2579 } else {
2580 // Use ParallelGCThreads inside safepoints
2581 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
2582 }
2583 } else {
2584 if (UseDynamicNumberOfGCThreads) {
2585 assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
2586 } else {
2587 // Use ConcGCThreads outside safepoints
2588 assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
2589 }
2590 }
2591 }
2592 #endif
2593
2594 ShenandoahVerifier* ShenandoahHeap::verifier() {
2595 guarantee(ShenandoahVerify, "Should be enabled");
2596 assert (_verifier != nullptr, "sanity");
2597 return _verifier;
2598 }
2599
2600 template<bool CONCURRENT>
2601 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2602 private:
2603 ShenandoahHeap* _heap;
2604 ShenandoahRegionIterator* _regions;
2605 ShenandoahRegionChunkIterator* _work_chunks;
2606
2607 public:
2608 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions,
2609 ShenandoahRegionChunkIterator* work_chunks) :
2610 WorkerTask("Shenandoah Update References"),
2611 _heap(ShenandoahHeap::heap()),
2612 _regions(regions),
2613 _work_chunks(work_chunks)
2614 {
2615 }
2616
2617 void work(uint worker_id) {
2618 if (CONCURRENT) {
2619 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2620 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
2621 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2622 } else {
2623 ShenandoahParallelWorkerSession worker_session(worker_id);
2624 do_work<ShenandoahSTWUpdateRefsClosure>(worker_id);
2625 }
2626 }
2627
2628 private:
2629 template<class T>
2630 void do_work(uint worker_id) {
2631 T cl;
2632 ShenandoahHeapRegion* r = _regions->next();
2633 // We update references for global, old, and young collections.
2634 assert(_heap->active_generation()->is_mark_complete(), "Expected complete marking");
2635 ShenandoahMarkingContext* const ctx = _heap->marking_context();
2636 bool is_mixed = _heap->collection_set()->has_old_regions();
2637 while (r != nullptr) {
2638 HeapWord* update_watermark = r->get_update_watermark();
2639 assert (update_watermark >= r->bottom(), "sanity");
2640
2641 log_debug(gc)("ShenandoahUpdateHeapRefsTask::do_work(%u) looking at region " SIZE_FORMAT, worker_id, r->index());
2642 bool region_progress = false;
2643 if (r->is_active() && !r->is_cset()) {
2644 if (!_heap->mode()->is_generational() || (r->affiliation() == ShenandoahRegionAffiliation::YOUNG_GENERATION)) {
2645 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2646 region_progress = true;
2647 } else if (r->affiliation() == ShenandoahRegionAffiliation::OLD_GENERATION) {
2648 if (_heap->active_generation()->generation_mode() == GLOBAL) {
2649 // Note that GLOBAL collection is not as effectively balanced as young and mixed cycles. This is because
2650 // concurrent GC threads are parceled out entire heap regions of work at a time and there
2651 // is no "catchup phase" consisting of remembered set scanning, during which parcels of work are smaller
2652 // and more easily distributed more fairly across threads.
2653
2654 // TODO: Consider an improvement to load balance GLOBAL GC.
2655 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2656 region_progress = true;
2657 }
2658 // Otherwise, this is an old region in a young or mixed cycle. Process it during a second phase, below.
2659 // Don't bother to report pacing progress in this case.
2660 } else {
2661 // Because updating of references runs concurrently, it is possible that a FREE inactive region transitions
2662 // to a non-free active region while this loop is executing. Whenever this happens, the changing of a region's
2663 // active status may propagate at a different speed than the changing of the region's affiliation.
2664
2665 // When we reach this control point, it is because a race has allowed a region's is_active() status to be seen
2666 // by this thread before the region's affiliation() is seen by this thread.
2667
2668 // It's ok for this race to occur because the newly transformed region does not have any references to be
2669 // updated.
2670
2671 assert(r->get_update_watermark() == r->bottom(),
2672 "%s Region " SIZE_FORMAT " is_active but not recognized as YOUNG or OLD so must be newly transitioned from FREE",
2673 affiliation_name(r->affiliation()), r->index());
2674 }
2675 }
2676 if (region_progress && ShenandoahPacing) {
2677 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2678 }
2679 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2680 return;
2681 }
2682 r = _regions->next();
2683 }
2684
2685 if (_heap->mode()->is_generational() && (_heap->active_generation()->generation_mode() != GLOBAL)) {
2686 // Since this is generational and not GLOBAL, we have to process the remembered set. There's no remembered
2687 // set processing if not in generational mode or if GLOBAL mode.
2688
2689 // After this thread has exhausted its traditional update-refs work, it continues with updating refs within remembered set.
2690 // The remembered set workload is better balanced between threads, so threads that are "behind" can catch up with other
2691 // threads during this phase, allowing all threads to work more effectively in parallel.
2692 struct ShenandoahRegionChunk assignment;
2693 RememberedScanner* scanner = _heap->card_scan();
2694
2695 while (!_heap->check_cancelled_gc_and_yield(CONCURRENT) && _work_chunks->next(&assignment)) {
2696 // Keep grabbing next work chunk to process until finished, or asked to yield
2697 ShenandoahHeapRegion* r = assignment._r;
2698 if (r->is_active() && !r->is_cset() && (r->affiliation() == ShenandoahRegionAffiliation::OLD_GENERATION)) {
2699 HeapWord* start_of_range = r->bottom() + assignment._chunk_offset;
2700 HeapWord* end_of_range = r->get_update_watermark();
2701 if (end_of_range > start_of_range + assignment._chunk_size) {
2702 end_of_range = start_of_range + assignment._chunk_size;
2703 }
2704
2705 // Old region in a young cycle or mixed cycle.
2706 if (is_mixed) {
2707 // TODO: For mixed evac, consider building an old-gen remembered set that allows restricted updating
2708 // within old-gen HeapRegions. This remembered set can be constructed by old-gen concurrent marking
2709 // and augmented by card marking. For example, old-gen concurrent marking can remember for each old-gen
2710 // card which other old-gen regions it refers to: none, one-other specifically, multiple-other non-specific.
2711 // Update-references when _mixed_evac processess each old-gen memory range that has a traditional DIRTY
2712 // card or if the "old-gen remembered set" indicates that this card holds pointers specifically to an
2713 // old-gen region in the most recent collection set, or if this card holds pointers to other non-specific
2714 // old-gen heap regions.
2715
2716 if (r->is_humongous()) {
2717 if (start_of_range < end_of_range) {
2718 // Need to examine both dirty and clean cards during mixed evac.
2719 r->oop_iterate_humongous_slice(&cl, false, start_of_range, assignment._chunk_size, true);
2720 }
2721 } else {
2722 // Since this is mixed evacuation, old regions that are candidates for collection have not been coalesced
2723 // and filled. Use mark bits to find objects that need to be updated.
2724 //
2725 // Future TODO: establish a second remembered set to identify which old-gen regions point to other old-gen
2726 // regions which are in the collection set for a particular mixed evacuation.
2727 if (start_of_range < end_of_range) {
2728 HeapWord* p = nullptr;
2729 size_t card_index = scanner->card_index_for_addr(start_of_range);
2730 // In case last object in my range spans boundary of my chunk, I may need to scan all the way to top()
2731 ShenandoahObjectToOopBoundedClosure<T> objs(&cl, start_of_range, r->top());
2732
2733 // Any object that begins in a previous range is part of a different scanning assignment. Any object that
2734 // starts after end_of_range is also not my responsibility. (Either allocated during evacuation, so does
2735 // not hold pointers to from-space, or is beyond the range of my assigned work chunk.)
2736
2737 // Find the first object that begins in my range, if there is one.
2738 p = start_of_range;
2739 oop obj = cast_to_oop(p);
2740 HeapWord* tams = ctx->top_at_mark_start(r);
2741 if (p >= tams) {
2742 // We cannot use ctx->is_marked(obj) to test whether an object begins at this address. Instead,
2743 // we need to use the remembered set crossing map to advance p to the first object that starts
2744 // within the enclosing card.
2745
2746 while (true) {
2747 HeapWord* first_object = scanner->first_object_in_card(card_index);
2748 if (first_object != nullptr) {
2749 p = first_object;
2750 break;
2751 } else if (scanner->addr_for_card_index(card_index + 1) < end_of_range) {
2752 card_index++;
2753 } else {
2754 // Force the loop that follows to immediately terminate.
2755 p = end_of_range;
2756 break;
2757 }
2758 }
2759 obj = cast_to_oop(p);
2760 // Note: p may be >= end_of_range
2761 } else if (!ctx->is_marked(obj)) {
2762 p = ctx->get_next_marked_addr(p, tams);
2763 obj = cast_to_oop(p);
2764 // If there are no more marked objects before tams, this returns tams.
2765 // Note that tams is either >= end_of_range, or tams is the start of an object that is marked.
2766 }
2767 while (p < end_of_range) {
2768 // p is known to point to the beginning of marked object obj
2769 objs.do_object(obj);
2770 HeapWord* prev_p = p;
2771 p += obj->size();
2772 if (p < tams) {
2773 p = ctx->get_next_marked_addr(p, tams);
2774 // If there are no more marked objects before tams, this returns tams. Note that tams is
2775 // either >= end_of_range, or tams is the start of an object that is marked.
2776 }
2777 assert(p != prev_p, "Lack of forward progress");
2778 obj = cast_to_oop(p);
2779 }
2780 }
2781 }
2782 } else {
2783 // This is a young evac..
2784 if (start_of_range < end_of_range) {
2785 size_t cluster_size =
2786 CardTable::card_size_in_words() * ShenandoahCardCluster<ShenandoahDirectCardMarkRememberedSet>::CardsPerCluster;
2787 size_t clusters = assignment._chunk_size / cluster_size;
2788 assert(clusters * cluster_size == assignment._chunk_size, "Chunk assignment must align on cluster boundaries");
2789 scanner->process_region_slice(r, assignment._chunk_offset, clusters, end_of_range, &cl, true, worker_id);
2790 }
2791 }
2792 if (ShenandoahPacing && (start_of_range < end_of_range)) {
2793 _heap->pacer()->report_updaterefs(pointer_delta(end_of_range, start_of_range));
2794 }
2795 }
2796 }
2797 }
2798 }
2799 };
2800
2801 void ShenandoahHeap::update_heap_references(bool concurrent) {
2802 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2803 uint nworkers = workers()->active_workers();
2804 ShenandoahRegionChunkIterator work_list(nworkers);
2805
2806 if (concurrent) {
2807 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator, &work_list);
2808 workers()->run_task(&task);
2809 } else {
2810 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator, &work_list);
2811 workers()->run_task(&task);
2812 }
2813 if (ShenandoahEnableCardStats && card_scan()!=nullptr) { // generational check proxy
2814 card_scan()->log_card_stats(nworkers, CARD_STAT_UPDATE_REFS);
2815 }
2816 }
2817
2818 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2819 private:
2820 ShenandoahMarkingContext* _ctx;
2821 ShenandoahHeapLock* const _lock;
2822 bool _is_generational;
2823
2824 public:
2825 ShenandoahFinalUpdateRefsUpdateRegionStateClosure(
2826 ShenandoahMarkingContext* ctx) : _ctx(ctx), _lock(ShenandoahHeap::heap()->lock()),
2827 _is_generational(ShenandoahHeap::heap()->mode()->is_generational()) { }
2828
2829 void heap_region_do(ShenandoahHeapRegion* r) {
2830
2831 // Maintenance of region age must follow evacuation in order to account for evacuation allocations within survivor
2832 // regions. We consult region age during the subsequent evacuation to determine whether certain objects need to
2833 // be promoted.
2834 if (_is_generational && r->is_young()) {
2835 HeapWord *tams = _ctx->top_at_mark_start(r);
2836 HeapWord *top = r->top();
2837
2838 // Allocations move the watermark when top moves. However compacting
2839 // objects will sometimes lower top beneath the watermark, after which,
2840 // attempts to read the watermark will assert out (watermark should not be
2841 // higher than top).
2842 if (top > tams) {
2843 // There have been allocations in this region since the start of the cycle.
2844 // Any objects new to this region must not assimilate elevated age.
2845 r->reset_age();
2846 } else if (ShenandoahHeap::heap()->is_aging_cycle()) {
2847 r->increment_age();
2848 }
2849 }
2850
2851 // Drop unnecessary "pinned" state from regions that does not have CP marks
2852 // anymore, as this would allow trashing them.
2853 if (r->is_active()) {
2854 if (r->is_pinned()) {
2855 if (r->pin_count() == 0) {
2856 ShenandoahHeapLocker locker(_lock);
2857 r->make_unpinned();
2858 }
2859 } else {
2860 if (r->pin_count() > 0) {
2861 ShenandoahHeapLocker locker(_lock);
2862 r->make_pinned();
2863 }
2864 }
2865 }
2866 }
2867
2868 bool is_thread_safe() { return true; }
2869 };
2870
2871 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2872 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2873 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2874
2875 {
2876 ShenandoahGCPhase phase(concurrent ?
2877 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2878 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2879 ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl (active_generation()->complete_marking_context());
2880 parallel_heap_region_iterate(&cl);
2881
2882 assert_pinned_region_status();
2883 }
2884
2885 {
2886 ShenandoahGCPhase phase(concurrent ?
2887 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2888 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2889 trash_cset_regions();
2890 }
2891 }
2892
2893 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2894 {
2895 ShenandoahGCPhase phase(concurrent ?
2896 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2897 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2898 ShenandoahHeapLocker locker(lock());
2899 _free_set->rebuild();
2900 }
2901 }
2902
2903 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2904 print_on(st);
2905 print_heap_regions_on(st);
2906 }
2907
2908 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2909 size_t slice = r->index() / _bitmap_regions_per_slice;
2910
2911 size_t regions_from = _bitmap_regions_per_slice * slice;
2912 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2913 for (size_t g = regions_from; g < regions_to; g++) {
2914 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2915 if (skip_self && g == r->index()) continue;
2916 if (get_region(g)->is_committed()) {
2917 return true;
2918 }
2919 }
2920 return false;
2921 }
2922
2923 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2924 shenandoah_assert_heaplocked();
2925
2926 // Bitmaps in special regions do not need commits
2927 if (_bitmap_region_special) {
2928 return true;
2929 }
2930
2931 if (is_bitmap_slice_committed(r, true)) {
2932 // Some other region from the group is already committed, meaning the bitmap
2933 // slice is already committed, we exit right away.
2934 return true;
2935 }
2936
2937 // Commit the bitmap slice:
2938 size_t slice = r->index() / _bitmap_regions_per_slice;
2939 size_t off = _bitmap_bytes_per_slice * slice;
2940 size_t len = _bitmap_bytes_per_slice;
2941 char* start = (char*) _bitmap_region.start() + off;
2942
2943 if (!os::commit_memory(start, len, false)) {
2944 return false;
2945 }
2946
2947 if (AlwaysPreTouch) {
2948 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2949 }
2950
2951 return true;
2952 }
2953
2954 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2955 shenandoah_assert_heaplocked();
2956
2957 // Bitmaps in special regions do not need uncommits
2958 if (_bitmap_region_special) {
2959 return true;
2960 }
2961
2962 if (is_bitmap_slice_committed(r, true)) {
2963 // Some other region from the group is still committed, meaning the bitmap
2964 // slice is should stay committed, exit right away.
2965 return true;
2966 }
2967
2968 // Uncommit the bitmap slice:
2969 size_t slice = r->index() / _bitmap_regions_per_slice;
2970 size_t off = _bitmap_bytes_per_slice * slice;
2971 size_t len = _bitmap_bytes_per_slice;
2972 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2973 return false;
2974 }
2975 return true;
2976 }
2977
2978 void ShenandoahHeap::safepoint_synchronize_begin() {
2979 if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2980 SuspendibleThreadSet::synchronize();
2981 }
2982 }
2983
2984 void ShenandoahHeap::safepoint_synchronize_end() {
2985 if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2986 SuspendibleThreadSet::desynchronize();
2987 }
2988 }
2989
2990 void ShenandoahHeap::entry_uncommit(double shrink_before, size_t shrink_until) {
2991 static const char *msg = "Concurrent uncommit";
2992 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
2993 EventMark em("%s", msg);
2994
2995 op_uncommit(shrink_before, shrink_until);
2996 }
2997
2998 void ShenandoahHeap::try_inject_alloc_failure() {
2999 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
3000 _inject_alloc_failure.set();
3001 os::naked_short_sleep(1);
3002 if (cancelled_gc()) {
3003 log_info(gc)("Allocation failure was successfully injected");
3004 }
3005 }
3006 }
3007
3008 bool ShenandoahHeap::should_inject_alloc_failure() {
3009 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
3010 }
3011
3012 void ShenandoahHeap::initialize_serviceability() {
3013 if (mode()->is_generational()) {
3014 _young_gen_memory_pool = new ShenandoahYoungGenMemoryPool(this);
3015 _old_gen_memory_pool = new ShenandoahOldGenMemoryPool(this);
3016 _cycle_memory_manager.add_pool(_young_gen_memory_pool);
3017 _cycle_memory_manager.add_pool(_old_gen_memory_pool);
3018 _stw_memory_manager.add_pool(_young_gen_memory_pool);
3019 _stw_memory_manager.add_pool(_old_gen_memory_pool);
3020 } else {
3021 _memory_pool = new ShenandoahMemoryPool(this);
3022 _cycle_memory_manager.add_pool(_memory_pool);
3023 _stw_memory_manager.add_pool(_memory_pool);
3024 }
3025 }
3026
3027 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
3028 GrowableArray<GCMemoryManager*> memory_managers(2);
3029 memory_managers.append(&_cycle_memory_manager);
3030 memory_managers.append(&_stw_memory_manager);
3031 return memory_managers;
3032 }
3033
3034 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
3035 GrowableArray<MemoryPool*> memory_pools(1);
3036 if (mode()->is_generational()) {
3037 memory_pools.append(_young_gen_memory_pool);
3038 memory_pools.append(_old_gen_memory_pool);
3039 } else {
3040 memory_pools.append(_memory_pool);
3041 }
3042 return memory_pools;
3043 }
3044
3045 MemoryUsage ShenandoahHeap::memory_usage() {
3046 return MemoryUsage(_initial_size, used(), committed(), max_capacity());
3047 }
3048
3049 ShenandoahRegionIterator::ShenandoahRegionIterator() :
3050 _heap(ShenandoahHeap::heap()),
3051 _index(0) {}
3052
3053 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
3054 _heap(heap),
3055 _index(0) {}
3056
3057 void ShenandoahRegionIterator::reset() {
3058 _index = 0;
3059 }
3060
3061 bool ShenandoahRegionIterator::has_next() const {
3062 return _index < _heap->num_regions();
3063 }
3064
3065 char ShenandoahHeap::gc_state() const {
3066 return _gc_state.raw_value();
3067 }
3068
3069 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
3070 #ifdef ASSERT
3071 assert(_liveness_cache != nullptr, "sanity");
3072 assert(worker_id < _max_workers, "sanity");
3073 for (uint i = 0; i < num_regions(); i++) {
3074 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
3075 }
3076 #endif
3077 return _liveness_cache[worker_id];
3078 }
3079
3080 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
3081 assert(worker_id < _max_workers, "sanity");
3082 assert(_liveness_cache != nullptr, "sanity");
3083 ShenandoahLiveData* ld = _liveness_cache[worker_id];
3084
3085 for (uint i = 0; i < num_regions(); i++) {
3086 ShenandoahLiveData live = ld[i];
3087 if (live > 0) {
3088 ShenandoahHeapRegion* r = get_region(i);
3089 r->increase_live_data_gc_words(live);
3090 ld[i] = 0;
3091 }
3092 }
3093 }
3094
3095 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
3096 if (is_idle()) return false;
3097
3098 // Objects allocated after marking start are implicitly alive, don't need any barriers during
3099 // marking phase.
3100 if (is_concurrent_mark_in_progress() &&
3101 !marking_context()->allocated_after_mark_start(obj)) {
3102 return true;
3103 }
3104
3105 // Can not guarantee obj is deeply good.
3106 if (has_forwarded_objects()) {
3107 return true;
3108 }
3109
3110 return false;
3111 }
3112
3113 void ShenandoahHeap::transfer_old_pointers_from_satb() {
3114 _old_generation->transfer_pointers_from_satb();
3115 }
3116
3117 template<>
3118 void ShenandoahGenerationRegionClosure<YOUNG>::heap_region_do(ShenandoahHeapRegion* region) {
3119 // Visit young and free regions
3120 if (region->affiliation() != OLD_GENERATION) {
3121 _cl->heap_region_do(region);
3122 }
3123 }
3124
3125 template<>
3126 void ShenandoahGenerationRegionClosure<OLD>::heap_region_do(ShenandoahHeapRegion* region) {
3127 // Visit old and free regions
3128 if (region->affiliation() != YOUNG_GENERATION) {
3129 _cl->heap_region_do(region);
3130 }
3131 }
3132
3133 template<>
3134 void ShenandoahGenerationRegionClosure<GLOBAL>::heap_region_do(ShenandoahHeapRegion* region) {
3135 _cl->heap_region_do(region);
3136 }
3137
3138 // Assure that the remember set has a dirty card everywhere there is an interesting pointer.
3139 // This examines the read_card_table between bottom() and top() since all PLABS are retired
3140 // before the safepoint for init_mark. Actually, we retire them before update-references and don't
3141 // restore them until the start of evacuation.
3142 void ShenandoahHeap::verify_rem_set_at_mark() {
3143 shenandoah_assert_safepoint();
3144 assert(mode()->is_generational(), "Only verify remembered set for generational operational modes");
3145
3146 ShenandoahRegionIterator iterator;
3147 RememberedScanner* scanner = card_scan();
3148 ShenandoahVerifyRemSetClosure check_interesting_pointers(true);
3149 ShenandoahMarkingContext* ctx;
3150
3151 log_debug(gc)("Verifying remembered set at %s mark", doing_mixed_evacuations()? "mixed": "young");
3152
3153 if (is_old_bitmap_stable() || active_generation()->generation_mode() == GLOBAL) {
3154 ctx = complete_marking_context();
3155 } else {
3156 ctx = nullptr;
3157 }
3158
3159 while (iterator.has_next()) {
3160 ShenandoahHeapRegion* r = iterator.next();
3161 HeapWord* tams = ctx? ctx->top_at_mark_start(r): nullptr;
3162 if (r == nullptr)
3163 break;
3164 if (r->is_old() && r->is_active()) {
3165 HeapWord* obj_addr = r->bottom();
3166 if (r->is_humongous_start()) {
3167 oop obj = cast_to_oop(obj_addr);
3168 if (!ctx || ctx->is_marked(obj)) {
3169 // For humongous objects, the typical object is an array, so the following checks may be overkill
3170 // For regular objects (not object arrays), if the card holding the start of the object is dirty,
3171 // we do not need to verify that cards spanning interesting pointers within this object are dirty.
3172 if (!scanner->is_card_dirty(obj_addr) || obj->is_objArray()) {
3173 obj->oop_iterate(&check_interesting_pointers);
3174 }
3175 // else, object's start is marked dirty and obj is not an objArray, so any interesting pointers are covered
3176 }
3177 // else, this humongous object is not marked so no need to verify its internal pointers
3178 if (!scanner->verify_registration(obj_addr, ctx)) {
3179 ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, obj_addr, nullptr,
3180 "Verify init-mark remembered set violation", "object not properly registered", __FILE__, __LINE__);
3181 }
3182 } else if (!r->is_humongous()) {
3183 HeapWord* top = r->top();
3184 while (obj_addr < top) {
3185 oop obj = cast_to_oop(obj_addr);
3186 // ctx->is_marked() returns true if mark bit set (TAMS not relevant during init mark)
3187 if (!ctx || ctx->is_marked(obj)) {
3188 // For regular objects (not object arrays), if the card holding the start of the object is dirty,
3189 // we do not need to verify that cards spanning interesting pointers within this object are dirty.
3190 if (!scanner->is_card_dirty(obj_addr) || obj->is_objArray()) {
3191 obj->oop_iterate(&check_interesting_pointers);
3192 }
3193 // else, object's start is marked dirty and obj is not an objArray, so any interesting pointers are covered
3194 if (!scanner->verify_registration(obj_addr, ctx)) {
3195 ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, obj_addr, nullptr,
3196 "Verify init-mark remembered set violation", "object not properly registered", __FILE__, __LINE__);
3197 }
3198 obj_addr += obj->size();
3199 } else {
3200 // This object is not live so we don't verify dirty cards contained therein
3201 assert(tams != nullptr, "If object is not live, ctx and tams should be non-null");
3202 obj_addr = ctx->get_next_marked_addr(obj_addr, tams);
3203 }
3204 }
3205 } // else, we ignore humongous continuation region
3206 } // else, this is not an OLD region so we ignore it
3207 } // all regions have been processed
3208 }
3209
3210 void ShenandoahHeap::help_verify_region_rem_set(ShenandoahHeapRegion* r, ShenandoahMarkingContext* ctx, HeapWord* from,
3211 HeapWord* top, HeapWord* registration_watermark, const char* message) {
3212 RememberedScanner* scanner = card_scan();
3213 ShenandoahVerifyRemSetClosure check_interesting_pointers(false);
3214
3215 HeapWord* obj_addr = from;
3216 if (r->is_humongous_start()) {
3217 oop obj = cast_to_oop(obj_addr);
3218 if (!ctx || ctx->is_marked(obj)) {
3219 size_t card_index = scanner->card_index_for_addr(obj_addr);
3220 // For humongous objects, the typical object is an array, so the following checks may be overkill
3221 // For regular objects (not object arrays), if the card holding the start of the object is dirty,
3222 // we do not need to verify that cards spanning interesting pointers within this object are dirty.
3223 if (!scanner->is_write_card_dirty(card_index) || obj->is_objArray()) {
3224 obj->oop_iterate(&check_interesting_pointers);
3225 }
3226 // else, object's start is marked dirty and obj is not an objArray, so any interesting pointers are covered
3227 }
3228 // else, this humongous object is not live so no need to verify its internal pointers
3229
3230 if ((obj_addr < registration_watermark) && !scanner->verify_registration(obj_addr, ctx)) {
3231 ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, obj_addr, nullptr, message,
3232 "object not properly registered", __FILE__, __LINE__);
3233 }
3234 } else if (!r->is_humongous()) {
3235 while (obj_addr < top) {
3236 oop obj = cast_to_oop(obj_addr);
3237 // ctx->is_marked() returns true if mark bit set or if obj above TAMS.
3238 if (!ctx || ctx->is_marked(obj)) {
3239 size_t card_index = scanner->card_index_for_addr(obj_addr);
3240 // For regular objects (not object arrays), if the card holding the start of the object is dirty,
3241 // we do not need to verify that cards spanning interesting pointers within this object are dirty.
3242 if (!scanner->is_write_card_dirty(card_index) || obj->is_objArray()) {
3243 obj->oop_iterate(&check_interesting_pointers);
3244 }
3245 // else, object's start is marked dirty and obj is not an objArray, so any interesting pointers are covered
3246
3247 if ((obj_addr < registration_watermark) && !scanner->verify_registration(obj_addr, ctx)) {
3248 ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, obj_addr, nullptr, message,
3249 "object not properly registered", __FILE__, __LINE__);
3250 }
3251 obj_addr += obj->size();
3252 } else {
3253 // This object is not live so we don't verify dirty cards contained therein
3254 HeapWord* tams = ctx->top_at_mark_start(r);
3255 obj_addr = ctx->get_next_marked_addr(obj_addr, tams);
3256 }
3257 }
3258 }
3259 }
3260
3261 void ShenandoahHeap::verify_rem_set_after_full_gc() {
3262 shenandoah_assert_safepoint();
3263 assert(mode()->is_generational(), "Only verify remembered set for generational operational modes");
3264
3265 ShenandoahRegionIterator iterator;
3266
3267 while (iterator.has_next()) {
3268 ShenandoahHeapRegion* r = iterator.next();
3269 if (r == nullptr)
3270 break;
3271 if (r->is_old() && !r->is_cset()) {
3272 help_verify_region_rem_set(r, nullptr, r->bottom(), r->top(), r->top(), "Remembered set violation at end of Full GC");
3273 }
3274 }
3275 }
3276
3277 // Assure that the remember set has a dirty card everywhere there is an interesting pointer. Even though
3278 // the update-references scan of remembered set only examines cards up to update_watermark, the remembered
3279 // set should be valid through top. This examines the write_card_table between bottom() and top() because
3280 // all PLABS are retired immediately before the start of update refs.
3281 void ShenandoahHeap::verify_rem_set_at_update_ref() {
3282 shenandoah_assert_safepoint();
3283 assert(mode()->is_generational(), "Only verify remembered set for generational operational modes");
3284
3285 ShenandoahRegionIterator iterator;
3286 ShenandoahMarkingContext* ctx;
3287
3288 if (is_old_bitmap_stable() || active_generation()->generation_mode() == GLOBAL) {
3289 ctx = complete_marking_context();
3290 } else {
3291 ctx = nullptr;
3292 }
3293
3294 while (iterator.has_next()) {
3295 ShenandoahHeapRegion* r = iterator.next();
3296 if (r == nullptr)
3297 break;
3298 if (r->is_old() && !r->is_cset()) {
3299 help_verify_region_rem_set(r, ctx, r->bottom(), r->top(), r->get_update_watermark(),
3300 "Remembered set violation at init-update-references");
3301 }
3302 }
3303 }
3304
3305 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahRegionAffiliation affiliation) const {
3306 if (!mode()->is_generational()) {
3307 return global_generation();
3308 } else if (affiliation == YOUNG_GENERATION) {
3309 return young_generation();
3310 } else if (affiliation == OLD_GENERATION) {
3311 return old_generation();
3312 }
3313
3314 ShouldNotReachHere();
3315 return nullptr;
3316 }
3317
3318 void ShenandoahHeap::log_heap_status(const char* msg) const {
3319 if (mode()->is_generational()) {
3320 young_generation()->log_status(msg);
3321 old_generation()->log_status(msg);
3322 } else {
3323 global_generation()->log_status(msg);
3324 }
3325 }
3326