1 /*
2 * Copyright (c) 2023, 2026, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
4 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
5 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 *
7 * This code is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 only, as
9 * published by the Free Software Foundation.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27
28 #include "cds/aotMappedHeapWriter.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "gc/shared/classUnloadingContext.hpp"
31 #include "gc/shared/fullGCForwarding.hpp"
32 #include "gc/shared/gc_globals.hpp"
33 #include "gc/shared/gcArguments.hpp"
34 #include "gc/shared/gcTimer.hpp"
35 #include "gc/shared/gcTraceTime.inline.hpp"
36 #include "gc/shared/locationPrinter.inline.hpp"
37 #include "gc/shared/memAllocator.hpp"
38 #include "gc/shared/plab.hpp"
39 #include "gc/shared/tlab_globals.hpp"
40 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
41 #include "gc/shenandoah/heuristics/shenandoahYoungHeuristics.hpp"
42 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
43 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
44 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
45 #include "gc/shenandoah/shenandoahAllocator.hpp"
46 #include "gc/shenandoah/shenandoahAllocRate.inline.hpp"
47 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
48 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
49 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
50 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
51 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
52 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
53 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
54 #include "gc/shenandoah/shenandoahControlThread.hpp"
55 #include "gc/shenandoah/shenandoahFreeSet.hpp"
56 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp"
57 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
58 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
59 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
60 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
61 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
62 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
63 #include "gc/shenandoah/shenandoahInitLogger.hpp"
64 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
65 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
66 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
67 #include "gc/shenandoah/shenandoahObjArrayAllocator.hpp"
68 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
69 #include "gc/shenandoah/shenandoahPadding.hpp"
70 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
71 #include "gc/shenandoah/shenandoahPartitionAllocator.hpp"
72 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
73 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
74 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
75 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
76 #include "gc/shenandoah/shenandoahSTWMark.hpp"
77 #include "gc/shenandoah/shenandoahUncommitThread.hpp"
78 #include "gc/shenandoah/shenandoahUtils.hpp"
79 #include "gc/shenandoah/shenandoahVerifier.hpp"
80 #include "gc/shenandoah/shenandoahVMOperations.hpp"
81 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
82 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
83 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
84 #include "memory/allocation.hpp"
85 #include "memory/classLoaderMetaspace.hpp"
86 #include "memory/memoryReserver.hpp"
87 #include "memory/metaspaceUtils.hpp"
88 #include "memory/universe.hpp"
89 #include "nmt/mallocTracker.hpp"
90 #include "nmt/memTracker.hpp"
91 #include "oops/compressedOops.inline.hpp"
92 #include "prims/jvmtiTagMap.hpp"
93 #include "runtime/atomic.hpp"
94 #include "runtime/atomicAccess.hpp"
95 #include "runtime/globals.hpp"
96 #include "runtime/interfaceSupport.inline.hpp"
97 #include "runtime/java.hpp"
98 #include "runtime/orderAccess.hpp"
99 #include "runtime/safepointMechanism.hpp"
100 #include "runtime/stackWatermarkSet.hpp"
101 #include "runtime/threads.hpp"
102 #include "runtime/vmThread.hpp"
103 #include "utilities/events.hpp"
104 #include "utilities/globalDefinitions.hpp"
105 #include "utilities/powerOfTwo.hpp"
106 #if INCLUDE_JFR
107 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
108 #endif
109
110 class ShenandoahPretouchHeapTask : public WorkerTask {
111 private:
112 ShenandoahRegionIterator _regions;
113 const size_t _page_size;
114 public:
115 ShenandoahPretouchHeapTask(size_t page_size) :
116 WorkerTask("Shenandoah Pretouch Heap"),
117 _page_size(page_size) {}
118
119 virtual void work(uint worker_id) {
120 ShenandoahHeapRegion* r = _regions.next();
121 while (r != nullptr) {
122 if (r->is_committed()) {
123 os::pretouch_memory(r->bottom(), r->end(), _page_size);
124 }
125 r = _regions.next();
126 }
127 }
128 };
129
130 class ShenandoahPretouchBitmapTask : public WorkerTask {
131 private:
132 ShenandoahRegionIterator _regions;
133 char* _bitmap_base;
134 const size_t _bitmap_size;
135 const size_t _page_size;
136 public:
137 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
138 WorkerTask("Shenandoah Pretouch Bitmap"),
139 _bitmap_base(bitmap_base),
140 _bitmap_size(bitmap_size),
141 _page_size(page_size) {}
142
143 virtual void work(uint worker_id) {
144 ShenandoahHeapRegion* r = _regions.next();
145 while (r != nullptr) {
146 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
147 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
148 assert (end <= _bitmap_size, "end is sane: %zu < %zu", end, _bitmap_size);
149
150 if (r->is_committed()) {
151 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
152 }
153
154 r = _regions.next();
155 }
156 }
157 };
158
159 static ReservedSpace reserve(size_t size, size_t preferred_page_size) {
160 // When a page size is given we don't want to mix large
161 // and normal pages. If the size is not a multiple of the
162 // page size it will be aligned up to achieve this.
163 size_t alignment = os::vm_allocation_granularity();
164 if (preferred_page_size != os::vm_page_size()) {
165 alignment = MAX2(preferred_page_size, alignment);
166 size = align_up(size, alignment);
167 }
168
169 const ReservedSpace reserved = MemoryReserver::reserve(size, alignment, preferred_page_size, mtGC);
170 if (!reserved.is_reserved()) {
171 vm_exit_during_initialization("Could not reserve space");
172 }
173 return reserved;
174 }
175
176 jint ShenandoahHeap::initialize() {
177 //
178 // Figure out heap sizing
179 //
180
181 size_t init_byte_size = InitialHeapSize;
182 size_t min_byte_size = MinHeapSize;
183 size_t max_byte_size = MaxHeapSize;
184 size_t heap_alignment = HeapAlignment;
185
186 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
187
188 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
189 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
190
191 _num_regions = ShenandoahHeapRegion::region_count();
192 assert(_num_regions == (max_byte_size / reg_size_bytes),
193 "Regions should cover entire heap exactly: %zu != %zu/%zu",
194 _num_regions, max_byte_size, reg_size_bytes);
195
196 size_t num_committed_regions = init_byte_size / reg_size_bytes;
197 num_committed_regions = MIN2(num_committed_regions, _num_regions);
198 assert(num_committed_regions <= _num_regions, "sanity");
199 _initial_size = num_committed_regions * reg_size_bytes;
200
201 size_t num_min_regions = min_byte_size / reg_size_bytes;
202 num_min_regions = MIN2(num_min_regions, _num_regions);
203 assert(num_min_regions <= _num_regions, "sanity");
204 _minimum_size = num_min_regions * reg_size_bytes;
205
206 _soft_max_size.store_relaxed(clamp(SoftMaxHeapSize, min_capacity(), max_capacity()));
207
208 _committed.store_relaxed(_initial_size);
209
210 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
211 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
212 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
213
214 //
215 // Reserve and commit memory for heap
216 //
217
218 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
219 initialize_reserved_region(heap_rs);
220 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
221 _heap_region_special = heap_rs.special();
222
223 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
224 "Misaligned heap: " PTR_FORMAT, p2i(base()));
225 os::trace_page_sizes_for_requested_size("Heap",
226 max_byte_size, heap_alignment,
227 heap_rs.base(),
228 heap_rs.size(), heap_rs.page_size());
229
230 #if SHENANDOAH_OPTIMIZED_MARKTASK
231 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
232 // Fail if we ever attempt to address more than we can.
233 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
234 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
235 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
236 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
237 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
238 vm_exit_during_initialization("Fatal Error", buf);
239 }
240 #endif
241
242 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
243 if (!_heap_region_special) {
244 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
245 "Cannot commit heap memory");
246 }
247
248 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
249
250 // Now we know the number of regions and heap sizes, initialize the heuristics.
251 initialize_heuristics();
252
253 // If ShenandoahCardBarrier is enabled but it's not generational mode
254 // it means we're under passive mode and we have to initialize old gen
255 // for the purpose of having card table.
256 if (ShenandoahCardBarrier && !(mode()->is_generational())) {
257 _old_generation = new ShenandoahOldGeneration(max_workers());
258 }
259
260 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
261
262 //
263 // Worker threads must be initialized after the barrier is configured
264 //
265 _workers = new ShenandoahWorkerThreads("ShenWorker", _max_workers);
266 if (_workers == nullptr) {
267 vm_exit_during_initialization("Failed necessary allocation.");
268 } else {
269 _workers->initialize_workers();
270 }
271
272 if (ParallelGCThreads > 1) {
273 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
274 _safepoint_workers->initialize_workers();
275 }
276
277 //
278 // Reserve and commit memory for bitmap(s)
279 //
280
281 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
282 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
283
284 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
285
286 guarantee(bitmap_bytes_per_region != 0,
287 "Bitmap bytes per region should not be zero");
288 guarantee(is_power_of_2(bitmap_bytes_per_region),
289 "Bitmap bytes per region should be power of two: %zu", bitmap_bytes_per_region);
290
291 if (bitmap_page_size > bitmap_bytes_per_region) {
292 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
293 _bitmap_bytes_per_slice = bitmap_page_size;
294 } else {
295 _bitmap_regions_per_slice = 1;
296 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
297 }
298
299 guarantee(_bitmap_regions_per_slice >= 1,
300 "Should have at least one region per slice: %zu",
301 _bitmap_regions_per_slice);
302
303 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
304 "Bitmap slices should be page-granular: bps = %zu, page size = %zu",
305 _bitmap_bytes_per_slice, bitmap_page_size);
306
307 ReservedSpace bitmap = reserve(_bitmap_size, bitmap_page_size);
308 os::trace_page_sizes_for_requested_size("Mark Bitmap",
309 bitmap_size_orig, bitmap_page_size,
310 bitmap.base(),
311 bitmap.size(), bitmap.page_size());
312 MemTracker::record_virtual_memory_tag(bitmap, mtGC);
313 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
314 _bitmap_region_special = bitmap.special();
315
316 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
317 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
318 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
319 if (!_bitmap_region_special) {
320 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
321 "Cannot commit bitmap memory");
322 }
323
324 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
325
326 if (ShenandoahVerify) {
327 ReservedSpace verify_bitmap = reserve(_bitmap_size, bitmap_page_size);
328 os::trace_page_sizes_for_requested_size("Verify Bitmap",
329 bitmap_size_orig, bitmap_page_size,
330 verify_bitmap.base(),
331 verify_bitmap.size(), verify_bitmap.page_size());
332 if (!verify_bitmap.special()) {
333 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
334 "Cannot commit verification bitmap memory");
335 }
336 MemTracker::record_virtual_memory_tag(verify_bitmap, mtGC);
337 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
338 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
339 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
340 }
341
342 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
343 size_t aux_bitmap_page_size = bitmap_page_size;
344
345 ReservedSpace aux_bitmap = reserve(_bitmap_size, aux_bitmap_page_size);
346 os::trace_page_sizes_for_requested_size("Aux Bitmap",
347 bitmap_size_orig, aux_bitmap_page_size,
348 aux_bitmap.base(),
349 aux_bitmap.size(), aux_bitmap.page_size());
350 MemTracker::record_virtual_memory_tag(aux_bitmap, mtGC);
351 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
352 _aux_bitmap_region_special = aux_bitmap.special();
353 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
354
355 //
356 // Create regions and region sets
357 //
358 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
359 size_t region_storage_size_orig = region_align * _num_regions;
360 size_t region_storage_size = align_up(region_storage_size_orig,
361 MAX2(region_page_size, os::vm_allocation_granularity()));
362
363 ReservedSpace region_storage = reserve(region_storage_size, region_page_size);
364 os::trace_page_sizes_for_requested_size("Region Storage",
365 region_storage_size_orig, region_page_size,
366 region_storage.base(),
367 region_storage.size(), region_storage.page_size());
368 MemTracker::record_virtual_memory_tag(region_storage, mtGC);
369 if (!region_storage.special()) {
370 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
371 "Cannot commit region memory");
372 }
373
374 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
375 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
376 // If not successful, bite a bullet and allocate at whatever address.
377 {
378 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
379 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
380 const size_t cset_page_size = os::vm_page_size();
381
382 uintptr_t min = round_up_power_of_2(cset_align);
383 uintptr_t max = (1u << 30u);
384 ReservedSpace cset_rs;
385
386 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
387 char* req_addr = (char*)addr;
388 assert(is_aligned(req_addr, cset_align), "Should be aligned");
389 cset_rs = MemoryReserver::reserve(req_addr, cset_size, cset_align, cset_page_size, mtGC);
390 if (cset_rs.is_reserved()) {
391 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
392 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
393 break;
394 }
395 }
396
397 if (_collection_set == nullptr) {
398 cset_rs = MemoryReserver::reserve(cset_size, cset_align, os::vm_page_size(), mtGC);
399 if (!cset_rs.is_reserved()) {
400 vm_exit_during_initialization("Cannot reserve memory for collection set");
401 }
402
403 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
404 }
405 os::trace_page_sizes_for_requested_size("Collection Set",
406 cset_size, cset_page_size,
407 cset_rs.base(),
408 cset_rs.size(), cset_rs.page_size());
409 }
410
411 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
412 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
413
414 {
415 ShenandoahHeapLocker locker(lock());
416 for (size_t i = 0; i < _num_regions; i++) {
417 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
418 bool is_committed = i < num_committed_regions;
419 void* loc = region_storage.base() + i * region_align;
420
421 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
422 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
423
424 _marking_context->initialize_top_at_mark_start(r);
425 _regions[i] = r;
426 assert(!collection_set()->is_in(i), "New region should not be in collection set");
427
428 _affiliations[i] = ShenandoahAffiliation::FREE;
429 }
430
431 if (mode()->is_generational()) {
432 size_t young_reserve = (soft_max_capacity() * ShenandoahEvacReserve) / 100;
433 young_generation()->set_evacuation_reserve(young_reserve);
434 old_generation()->set_evacuation_reserve((size_t) 0);
435 old_generation()->set_promoted_reserve((size_t) 0);
436 }
437
438 _free_set = new ShenandoahFreeSet(this, _num_regions);
439 _allocator = new ShenandoahAllocator(_free_set);
440 initialize_generations();
441
442 // We are initializing free set. We ignore cset region tallies.
443 size_t young_trashed_regions, old_trashed_regions, first_old, last_old, num_old;
444 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old, last_old, num_old);
445 if (mode()->is_generational()) {
446 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
447 // We cannot call
448 // gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions)
449 // until after the heap is fully initialized. So we make up a safe value here.
450 size_t allocation_runway = InitialHeapSize / 2;
451 gen_heap->compute_old_generation_balance(allocation_runway, old_trashed_regions, young_trashed_regions);
452 }
453 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, num_old);
454 }
455
456 if (AlwaysPreTouch) {
457 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
458 // before initialize() below zeroes it with initializing thread. For any given region,
459 // we touch the region and the corresponding bitmaps from the same thread.
460 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
461
462 _pretouch_heap_page_size = heap_page_size;
463 _pretouch_bitmap_page_size = bitmap_page_size;
464
465 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
466 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
467
468 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
469 _workers->run_task(&bcl);
470
471 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
472 _workers->run_task(&hcl);
473 }
474
475 //
476 // Initialize the rest of GC subsystems
477 //
478
479 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
480 for (uint worker = 0; worker < _max_workers; worker++) {
481 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
482 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
483 }
484
485 // There should probably be Shenandoah-specific options for these,
486 // just as there are G1-specific options.
487 {
488 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
489 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
490 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
491 }
492
493 _monitoring_support = new ShenandoahMonitoringSupport(this);
494 _phase_timings = new ShenandoahPhaseTimings(max_workers());
495 ShenandoahCodeRoots::initialize();
496
497 // Initialization of controller makes use of variables established by initialize_heuristics.
498 initialize_controller();
499
500 // Certain initialization of heuristics must be deferred until after controller is initialized.
501 post_initialize_heuristics();
502 start_idle_span();
503 if (ShenandoahUncommit) {
504 _uncommit_thread = new ShenandoahUncommitThread(this);
505 }
506 print_init_logger();
507 FullGCForwarding::initialize(_heap_region);
508 return JNI_OK;
509 }
510
511 void ShenandoahHeap::initialize_controller() {
512 _control_thread = new ShenandoahControlThread();
513 }
514
515 void ShenandoahHeap::print_init_logger() const {
516 ShenandoahInitLogger::print();
517 }
518
519 void ShenandoahHeap::initialize_mode() {
520 if (ShenandoahGCMode != nullptr) {
521 if (strcmp(ShenandoahGCMode, "satb") == 0) {
522 _gc_mode = new ShenandoahSATBMode();
523 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
524 _gc_mode = new ShenandoahPassiveMode();
525 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
526 _gc_mode = new ShenandoahGenerationalMode();
527 } else {
528 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
529 }
530 } else {
531 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
532 }
533 _gc_mode->initialize_flags();
534 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
535 vm_exit_during_initialization(
536 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
537 _gc_mode->name()));
538 }
539 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
540 vm_exit_during_initialization(
541 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
542 _gc_mode->name()));
543 }
544 }
545
546 void ShenandoahHeap::initialize_heuristics() {
547 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers());
548 _global_generation->initialize_heuristics(mode());
549 }
550
551 #ifdef _MSC_VER
552 #pragma warning( push )
553 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
554 #endif
555
556 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
557 CollectedHeap(),
558 _active_generation(nullptr),
559 _initial_size(0),
560 _committed(0),
561 _alloc_rate_decay(&_alloc_rate),
562 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
563 _workers(nullptr),
564 _safepoint_workers(nullptr),
565 _heap_region_special(false),
566 _num_regions(0),
567 _regions(nullptr),
568 _affiliations(nullptr),
569 _gc_state_changed(false),
570 _gc_no_progress_count(0),
571 _cancel_requested_time(0),
572 _update_refs_iterator(this),
573 _global_generation(nullptr),
574 _control_thread(nullptr),
575 _uncommit_thread(nullptr),
576 _young_generation(nullptr),
577 _old_generation(nullptr),
578 _shenandoah_policy(policy),
579 _gc_mode(nullptr),
580 _free_set(nullptr),
581 _allocator(nullptr),
582 _verifier(nullptr),
583 _phase_timings(nullptr),
584 _monitoring_support(nullptr),
585 _memory_pool(nullptr),
586 _stw_memory_manager("Shenandoah Pauses"),
587 _cycle_memory_manager("Shenandoah Cycles"),
588 _gc_timer(new ConcurrentGCTimer()),
589 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
590 _marking_context(nullptr),
591 _bitmap_size(0),
592 _bitmap_regions_per_slice(0),
593 _bitmap_bytes_per_slice(0),
594 _bitmap_region_special(false),
595 _aux_bitmap_region_special(false),
596 _liveness_cache(nullptr),
597 _collection_set(nullptr),
598 _evac_tracker(new ShenandoahEvacuationTracker()),
599 _injected_pin_count(0)
600 {
601 // Initialize GC mode early, many subsequent initialization procedures depend on it
602 initialize_mode();
603 _cancelled_gc.set(GCCause::_no_gc);
604 }
605
606 #ifdef _MSC_VER
607 #pragma warning( pop )
608 #endif
609
610 void ShenandoahHeap::print_heap_on(outputStream* st) const {
611 const bool is_generational = mode()->is_generational();
612 const char* front_spacing = "";
613 if (is_generational) {
614 st->print_cr("Generational Shenandoah Heap");
615 st->print_cr(" Young:");
616 st->print_cr(" " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(young_generation()->max_capacity()), PROPERFMTARGS(young_generation()->used()));
617 st->print_cr(" Old:");
618 st->print_cr(" " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(old_generation()->max_capacity()), PROPERFMTARGS(old_generation()->used()));
619 st->print_cr(" Entire heap:");
620 st->print_cr(" " PROPERFMT " soft max, " PROPERFMT " committed",
621 PROPERFMTARGS(soft_max_capacity()), PROPERFMTARGS(committed()));
622 front_spacing = " ";
623 } else {
624 st->print_cr("Shenandoah Heap");
625 st->print_cr(" " PROPERFMT " max, " PROPERFMT " soft max, " PROPERFMT " committed, " PROPERFMT " used",
626 PROPERFMTARGS(max_capacity()),
627 PROPERFMTARGS(soft_max_capacity()),
628 PROPERFMTARGS(committed()),
629 PROPERFMTARGS(used())
630 );
631 }
632 st->print_cr("%s %zu x " PROPERFMT " regions",
633 front_spacing,
634 num_regions(),
635 PROPERFMTARGS(ShenandoahHeapRegion::region_size_bytes()));
636
637 st->print("Status: ");
638 if (has_forwarded_objects()) st->print("has forwarded objects, ");
639 if (!is_generational) {
640 if (is_concurrent_mark_in_progress()) st->print("marking,");
641 } else {
642 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
643 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
644 }
645 if (is_evacuation_in_progress()) st->print("evacuating, ");
646 if (is_update_refs_in_progress()) st->print("updating refs, ");
647 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
648 if (is_full_gc_in_progress()) st->print("full gc, ");
649 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
650 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
651 if (is_concurrent_strong_root_in_progress() &&
652 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
653
654 if (cancelled_gc()) {
655 st->print("cancelled");
656 } else {
657 st->print("not cancelled");
658 }
659 st->cr();
660
661 st->print_cr("Reserved region:");
662 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
663 p2i(reserved_region().start()),
664 p2i(reserved_region().end()));
665
666 ShenandoahCollectionSet* cset = collection_set();
667 st->print_cr("Collection set:");
668 if (cset != nullptr) {
669 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
670 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
671 } else {
672 st->print_cr(" (null)");
673 }
674
675 st->cr();
676
677 if (Verbose) {
678 st->cr();
679 print_heap_regions_on(st);
680 }
681 }
682
683 void ShenandoahHeap::print_gc_on(outputStream* st) const {
684 print_heap_regions_on(st);
685 }
686
687 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
688 public:
689 void do_thread(Thread* thread) {
690 assert(thread != nullptr, "Sanity");
691 ShenandoahThreadLocalData::initialize_gclab(thread);
692 }
693 };
694
695 void ShenandoahHeap::initialize_generations() {
696 _global_generation->post_initialize(this);
697 }
698
699 // We do not call this explicitly It is called by Hotspot infrastructure.
700 void ShenandoahHeap::post_initialize() {
701 CollectedHeap::post_initialize();
702
703 check_soft_max_changed();
704
705 // Schedule periodic task to report on gc thread CPU utilization
706 _mmu_tracker.initialize();
707
708 // Periodically decay allocation rate to compensate for not being updated when allocation rate
709 // is low. Heuristics are evaluated unconditionally from a dedicated thread so it will continue
710 // to see the last (possibly stale) allocation rate if the allocation rate is low.
711 _alloc_rate_decay.enroll();
712
713 MutexLocker ml(Threads_lock);
714
715 ShenandoahInitWorkerGCLABClosure init_gclabs;
716 _workers->threads_do(&init_gclabs);
717
718 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
719 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
720 _workers->set_initialize_gclab();
721
722 // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump
723 // during a concurrent evacuation phase.
724 if (_safepoint_workers != nullptr) {
725 _safepoint_workers->threads_do(&init_gclabs);
726 _safepoint_workers->set_initialize_gclab();
727 }
728
729 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
730 }
731
732 void ShenandoahHeap::post_initialize_heuristics() {
733 _global_generation->post_initialize_heuristics();
734 }
735
736 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
737 return _global_generation->heuristics();
738 }
739
740 size_t ShenandoahHeap::used() const {
741 return global_generation()->used();
742 }
743
744 size_t ShenandoahHeap::committed() const {
745 return _committed.load_relaxed();
746 }
747
748 void ShenandoahHeap::increase_committed(size_t bytes) {
749 shenandoah_assert_heaplocked_or_safepoint();
750 _committed.fetch_then_add(bytes, memory_order_relaxed);
751 }
752
753 void ShenandoahHeap::decrease_committed(size_t bytes) {
754 shenandoah_assert_heaplocked_or_safepoint();
755 _committed.fetch_then_sub(bytes, memory_order_relaxed);
756 }
757
758 size_t ShenandoahHeap::capacity() const {
759 return committed();
760 }
761
762 size_t ShenandoahHeap::max_capacity() const {
763 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
764 }
765
766 size_t ShenandoahHeap::soft_max_capacity() const {
767 size_t v = _soft_max_size.load_relaxed();
768 assert(min_capacity() <= v && v <= max_capacity(),
769 "Should be in bounds: %zu <= %zu <= %zu",
770 min_capacity(), v, max_capacity());
771 return v;
772 }
773
774 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
775 assert(min_capacity() <= v && v <= max_capacity(),
776 "Should be in bounds: %zu <= %zu <= %zu",
777 min_capacity(), v, max_capacity());
778 _soft_max_size.store_relaxed(v);
779 heuristics()->compute_headroom_adjustment();
780 }
781
782 size_t ShenandoahHeap::min_capacity() const {
783 return _minimum_size;
784 }
785
786 size_t ShenandoahHeap::initial_capacity() const {
787 return _initial_size;
788 }
789
790 bool ShenandoahHeap::is_in(const void* p) const {
791 if (!is_in_reserved(p)) {
792 return false;
793 }
794
795 if (is_full_gc_move_in_progress()) {
796 // Full GC move is running, we do not have a consistent region
797 // information yet. But we know the pointer is in heap.
798 return true;
799 }
800
801 // Now check if we point to a live section in active region.
802 const ShenandoahHeapRegion* r = heap_region_containing(p);
803 if (p >= r->top()) {
804 return false;
805 }
806
807 if (r->is_active()) {
808 return true;
809 }
810
811 // The region is trash, but won't be recycled until after concurrent weak
812 // roots. We also don't allow mutators to allocate from trash regions
813 // during weak roots. Concurrent class unloading may access unmarked oops
814 // in trash regions.
815 return r->is_trash() && is_concurrent_weak_root_in_progress();
816 }
817
818 void ShenandoahHeap::notify_soft_max_changed() {
819 if (_uncommit_thread != nullptr) {
820 _uncommit_thread->notify_soft_max_changed();
821 }
822 }
823
824 void ShenandoahHeap::notify_explicit_gc_requested() {
825 if (_uncommit_thread != nullptr) {
826 _uncommit_thread->notify_explicit_gc_requested();
827 }
828 }
829
830 bool ShenandoahHeap::check_soft_max_changed() {
831 size_t new_soft_max = AtomicAccess::load(&SoftMaxHeapSize);
832 size_t old_soft_max = soft_max_capacity();
833 if (new_soft_max != old_soft_max) {
834 new_soft_max = clamp(new_soft_max, min_capacity(), max_capacity());
835 if (new_soft_max != old_soft_max) {
836 log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s",
837 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
838 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
839 );
840 set_soft_max_capacity(new_soft_max);
841 return true;
842 }
843 }
844 return false;
845 }
846
847 void ShenandoahHeap::notify_heap_changed() {
848 // Update monitoring counters when we took a new region. This amortizes the
849 // update costs on slow path.
850 monitoring_support()->notify_heap_changed();
851 _heap_changed.try_set();
852 }
853
854 void ShenandoahHeap::start_idle_span() {
855 heuristics()->start_idle_span();
856 }
857
858 void ShenandoahHeap::set_forced_counters_update(bool value) {
859 monitoring_support()->set_forced_counters_update(value);
860 }
861
862 void ShenandoahHeap::handle_force_counters_update() {
863 monitoring_support()->handle_force_counters_update();
864 }
865
866 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
867 // New object should fit the GCLAB size
868 size_t min_size = MAX2(size, PLAB::min_size());
869
870 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
871 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
872
873 new_size = MIN2(new_size, PLAB::max_size());
874 new_size = MAX2(new_size, PLAB::min_size());
875
876 // Record new heuristic value even if we take any shortcut. This captures
877 // the case when moderately-sized objects always take a shortcut. At some point,
878 // heuristics should catch up with them.
879 log_debug(gc, free)("Set new GCLAB size: %zu", new_size);
880 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
881
882 if (new_size < size) {
883 // New size still does not fit the object. Fall back to shared allocation.
884 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
885 log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size);
886 return nullptr;
887 }
888
889 // Retire current GCLAB, and allocate a new one.
890 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
891 gclab->retire();
892
893 size_t actual_size = 0;
894 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
895 if (gclab_buf == nullptr) {
896 return nullptr;
897 }
898
899 assert (size <= actual_size, "allocation should fit");
900
901 // ...and clear or zap just allocated TLAB, if needed.
902 if (ZeroTLAB) {
903 Copy::zero_to_words(gclab_buf, actual_size);
904 } else if (ZapTLAB) {
905 // Skip mangling the space corresponding to the object header to
906 // ensure that the returned space is not considered parsable by
907 // any concurrent GC thread.
908 size_t hdr_size = oopDesc::header_size();
909 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
910 }
911 gclab->set_buf(gclab_buf, actual_size);
912 return gclab->allocate(size);
913 }
914
915 // Called from stubs in JIT code or interpreter
916 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
917 size_t requested_size,
918 size_t* actual_size) {
919 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
920 HeapWord* res = allocate_memory(req);
921 if (res != nullptr) {
922 *actual_size = req.actual_size();
923 } else {
924 *actual_size = 0;
925 }
926 return res;
927 }
928
929 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
930 size_t word_size,
931 size_t* actual_size) {
932 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
933 HeapWord* res = allocate_memory(req);
934 if (res != nullptr) {
935 *actual_size = req.actual_size();
936 } else {
937 *actual_size = 0;
938 }
939 return res;
940 }
941
942 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
943 bool in_new_region = false;
944 HeapWord* result = nullptr;
945
946 if (req.is_mutator_alloc()) {
947
948 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
949 result = allocate_memory_work(req, in_new_region);
950 }
951
952 // Check that gc overhead is not exceeded.
953 //
954 // Shenandoah will grind along for quite a while allocating one
955 // object at a time using shared (non-tlab) allocations. This check
956 // is testing that the GC overhead limit has not been exceeded.
957 // This will notify the collector to start a cycle, but will raise
958 // an OOME to the mutator if the last Full GCs have not made progress.
959 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
960 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
961 control_thread()->handle_alloc_failure(req, false);
962 req.set_actual_size(0);
963 return nullptr;
964 }
965
966 if (result == nullptr) {
967 // Block until control thread reacted, then retry allocation.
968 //
969 // It might happen that one of the threads requesting allocation would unblock
970 // way later after GC happened, only to fail the second allocation, because
971 // other threads have already depleted the free storage. In this case, a better
972 // strategy is to try again, until at least one full GC has completed.
973 //
974 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
975 // a) We experienced a GC that had good progress, or
976 // b) We experienced at least one Full GC (whether or not it had good progress)
977
978 const size_t original_count = shenandoah_policy()->full_gc_count();
979 while (result == nullptr && should_retry_allocation(original_count)) {
980 control_thread()->handle_alloc_failure(req, true);
981 result = allocate_memory_work(req, in_new_region);
982 }
983 if (result != nullptr) {
984 // If our allocation request has been satisfied after it initially failed, we count this as good gc progress
985 notify_gc_progress();
986 }
987 if (log_develop_is_enabled(Debug, gc, alloc)) {
988 ResourceMark rm;
989 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu"
990 ", Original: %zu, Latest: %zu",
991 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
992 original_count, get_gc_no_progress_count());
993 }
994 }
995 } else {
996 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
997 result = allocate_memory_work(req, in_new_region);
998 // Do not call handle_alloc_failure() here, because we cannot block.
999 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1000 }
1001
1002 if (in_new_region) {
1003 notify_heap_changed();
1004 }
1005
1006 if (result == nullptr) {
1007 req.set_actual_size(0);
1008 }
1009
1010 if (result != nullptr) {
1011 size_t requested = req.size();
1012 size_t actual = req.actual_size();
1013
1014 assert (req.is_lab_alloc() || (requested == actual),
1015 "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu",
1016 req.type_string(), requested, actual);
1017 }
1018
1019 return result;
1020 }
1021
1022 inline bool ShenandoahHeap::should_retry_allocation(size_t original_full_gc_count) const {
1023 return shenandoah_policy()->full_gc_count() == original_full_gc_count
1024 && !shenandoah_policy()->is_at_shutdown();
1025 }
1026
1027 HeapWord* ShenandoahHeap::allocate_memory_work(ShenandoahAllocRequest& req, bool& in_new_region) {
1028 // Reserve the promotion budget up front so it is enforced atomically without the heap lock.
1029 // If the reserve is exhausted, deny the promotion rather than overshoot it; the reservation
1030 // is refunded below if the allocation itself fails.
1031 if (req.is_promotion() && !old_generation()->try_expend_promoted(req.size() << LogHeapWordSize)) {
1032 return nullptr;
1033 }
1034
1035 HeapWord* result = _allocator->allocate(req, in_new_region);
1036
1037 if (result != nullptr) {
1038 if (req.is_mutator_alloc()) {
1039 _alloc_rate.allocated((req.actual_size() + req.waste()) * HeapWordSize);
1040 }
1041
1042 if (req.is_old()) {
1043 if (req.is_lab_alloc()) {
1044 old_generation()->configure_plab_for_current_thread(req);
1045 } else if (req.is_promotion()) {
1046 log_debug(gc, plab)("Expend shared promotion of %zu bytes", req.actual_size() * HeapWordSize);
1047 }
1048 }
1049 } else if (req.is_promotion()) {
1050 // Allocation failed, so refund the promotion budget reserved above.
1051 old_generation()->unexpend_promoted(req.size() << LogHeapWordSize);
1052 }
1053 return result;
1054 }
1055
1056 HeapWord* ShenandoahHeap::mem_allocate(size_t size) {
1057 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1058 return allocate_memory(req);
1059 }
1060
1061 oop ShenandoahHeap::array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS) {
1062 ShenandoahObjArrayAllocator allocator(klass, size, length, do_zero, THREAD);
1063 return allocator.allocate();
1064 }
1065
1066 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1067 size_t size,
1068 Metaspace::MetadataType mdtype) {
1069 MetaWord* result;
1070
1071 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1072 ShenandoahHeuristics* h = global_generation()->heuristics();
1073 if (h->can_unload_classes()) {
1074 h->record_metaspace_oom();
1075 }
1076
1077 // Expand and retry allocation
1078 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1079 if (result != nullptr) {
1080 return result;
1081 }
1082
1083 // Start full GC
1084 collect(GCCause::_metadata_GC_clear_soft_refs);
1085
1086 // Retry allocation
1087 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1088 if (result != nullptr) {
1089 return result;
1090 }
1091
1092 // Expand and retry allocation
1093 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1094 if (result != nullptr) {
1095 return result;
1096 }
1097
1098 // Out of memory
1099 return nullptr;
1100 }
1101
1102 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1103 private:
1104 ShenandoahHeap* const _heap;
1105 Thread* const _thread;
1106 public:
1107 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1108 _heap(heap), _thread(Thread::current()) {}
1109
1110 void do_object(oop p) {
1111 shenandoah_assert_marked(nullptr, p);
1112 if (!p->is_forwarded()) {
1113 _heap->evacuate_object(p, _thread);
1114 }
1115 }
1116 };
1117
1118 class ShenandoahEvacuationTask : public WorkerTask {
1119 private:
1120 ShenandoahHeap* const _sh;
1121 ShenandoahCollectionSet* const _cs;
1122 bool _concurrent;
1123 public:
1124 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1125 ShenandoahCollectionSet* cs,
1126 bool concurrent) :
1127 WorkerTask("Shenandoah Evacuation"),
1128 _sh(sh),
1129 _cs(cs),
1130 _concurrent(concurrent)
1131 {}
1132
1133 void work(uint worker_id) {
1134 if (_concurrent) {
1135 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_evac, ShenandoahPhaseTimings::Work, worker_id, true);
1136 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1137 SuspendibleThreadSetJoiner stsj;
1138 do_work();
1139 } else {
1140 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_evac, ShenandoahPhaseTimings::Work, worker_id, true);
1141 ShenandoahParallelWorkerSession worker_session(worker_id);
1142 do_work();
1143 }
1144 }
1145
1146 private:
1147 void do_work() {
1148 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1149 ShenandoahHeapRegion* r;
1150 while ((r =_cs->claim_next()) != nullptr) {
1151 assert(r->has_live(), "Region %zu should have been reclaimed early", r->index());
1152 _sh->marked_object_iterate(r, &cl);
1153
1154 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1155 break;
1156 }
1157 }
1158 }
1159 };
1160
1161 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1162 private:
1163 bool const _resize;
1164 public:
1165 explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1166 void do_thread(Thread* thread) override {
1167 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1168 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1169 gclab->retire();
1170 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1171 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1172 }
1173
1174 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1175 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1176 assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1177
1178 // There are two reasons to retire all plabs between old-gen evacuation passes.
1179 // 1. We need to make the plab memory parsable by remembered-set scanning.
1180 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1181 shenandoah_plab->retire();
1182
1183 // Re-enable promotions for the next evacuation phase.
1184 shenandoah_plab->enable_promotions();
1185
1186 // Reset the fill size for next evacuation phase.
1187 if (_resize && shenandoah_plab->desired_size() > 0) {
1188 shenandoah_plab->set_desired_size(0);
1189 }
1190 }
1191 }
1192 };
1193
1194 class ShenandoahGCStatePropagatorHandshakeClosure : public HandshakeClosure {
1195 public:
1196 explicit ShenandoahGCStatePropagatorHandshakeClosure(char gc_state) :
1197 HandshakeClosure("Shenandoah GC State Change"),
1198 _gc_state(gc_state) {}
1199
1200 void do_thread(Thread* thread) override {
1201 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state);
1202 }
1203 private:
1204 char _gc_state;
1205 };
1206
1207 class ShenandoahPrepareForUpdateRefsHandshakeClosure : public HandshakeClosure {
1208 public:
1209 explicit ShenandoahPrepareForUpdateRefsHandshakeClosure(char gc_state) :
1210 HandshakeClosure("Shenandoah Prepare for Update Refs"),
1211 _retire(ResizeTLAB), _propagator(gc_state) {}
1212
1213 void do_thread(Thread* thread) override {
1214 _propagator.do_thread(thread);
1215 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) {
1216 _retire.do_thread(thread);
1217 }
1218 }
1219 private:
1220 ShenandoahRetireGCLABClosure _retire;
1221 ShenandoahGCStatePropagatorHandshakeClosure _propagator;
1222 };
1223
1224 void ShenandoahHeap::evacuate_collection_set(ShenandoahGeneration* generation, bool concurrent) {
1225 assert(generation->is_global(), "Only global generation expected here");
1226 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1227 workers()->run_task(&task);
1228 }
1229
1230 void ShenandoahHeap::concurrent_prepare_for_update_refs() {
1231 {
1232 // Java threads take this lock while they are being attached and added to the list of threads.
1233 // If another thread holds this lock before we update the gc state, it will receive a stale
1234 // gc state, but they will have been added to the list of java threads and so will be corrected
1235 // by the following handshake.
1236 MutexLocker lock(Threads_lock);
1237
1238 // A cancellation at this point means the degenerated cycle must resume from update-refs.
1239 set_gc_state_concurrent(EVACUATION, false);
1240 set_gc_state_concurrent(UPDATE_REFS, true);
1241 }
1242
1243 // This will propagate the gc state and retire gclabs and plabs for threads that require it.
1244 ShenandoahPrepareForUpdateRefsHandshakeClosure prepare_for_update_refs(_gc_state.raw_value());
1245
1246 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately.
1247 Threads::non_java_threads_do(&prepare_for_update_refs);
1248
1249 // Now retire gclabs and plabs and propagate gc_state for mutator threads
1250 Handshake::execute(&prepare_for_update_refs);
1251
1252 _update_refs_iterator.reset();
1253 }
1254
1255 void ShenandoahHeap::concurrent_final_roots() {
1256 {
1257 MutexLocker lock(Threads_lock);
1258
1259 #ifdef ASSERT
1260 for (JavaThreadIteratorWithHandle jtiwh; JavaThread* jt = jtiwh.next();) {
1261 StackWatermark* sw = StackWatermarkSet::get(jt, StackWatermarkKind::gc);
1262 assert(sw == nullptr || sw->processing_completed(),
1263 "Cannot turn off weak roots before stack watermark processing is complete");
1264 }
1265 #endif
1266
1267 set_gc_state_concurrent(WEAK_ROOTS, false);
1268 }
1269
1270 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
1271 Threads::non_java_threads_do(&propagator);
1272 Handshake::execute(&propagator);
1273 }
1274
1275 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1276 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1277
1278 ShenandoahHeapRegion* r = heap_region_containing(p);
1279 assert(!r->is_humongous(), "never evacuate humongous objects");
1280
1281 ShenandoahAffiliation target_gen = r->affiliation();
1282 return try_evacuate_object(p, thread, r, target_gen);
1283 }
1284
1285 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1286 ShenandoahAffiliation target_gen) {
1287 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1288 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1289 bool alloc_from_lab = true;
1290 HeapWord* copy = nullptr;
1291 size_t size = ShenandoahForwarding::size(p);
1292
1293 #ifdef ASSERT
1294 if (ShenandoahOOMDuringEvacALot &&
1295 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1296 copy = nullptr;
1297 } else {
1298 #endif
1299 if (UseTLAB) {
1300 copy = allocate_from_gclab(thread, size);
1301 }
1302 if (copy == nullptr) {
1303 // If we failed to allocate in LAB, we'll try a shared allocation.
1304 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1305 copy = allocate_memory(req);
1306 alloc_from_lab = false;
1307 }
1308 #ifdef ASSERT
1309 }
1310 #endif
1311
1312 if (copy == nullptr) {
1313 control_thread()->handle_alloc_failure_evac(size);
1314
1315 // Install the self-forwarded bit on p so other evacuators/LRBs see
1316 // the object as "already handled, do not try to evacuate". The CAS
1317 // may fail if another thread concurrently installed a real forwardee
1318 // (they succeeded where we failed) or self-forwarded first.
1319 markWord old_mark = p->mark();
1320 if (old_mark.is_forwarded()) {
1321 return ShenandoahForwarding::get_forwardee(p);
1322 }
1323 oop winner = ShenandoahForwarding::try_forward_to_self(p, old_mark);
1324 if (winner == nullptr) {
1325 // We own the self-forwarding. Flag the region so the degen/full GC
1326 // entry drain knows to scan it for self_fwd bits to clear.
1327 from_region->set_has_self_forwards();
1328 return p;
1329 }
1330 return winner;
1331 }
1332
1333 if (ShenandoahEvacTracking) {
1334 evac_tracker()->begin_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1335 }
1336
1337 // Copy the object:
1338 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1339
1340 oop copy_val = cast_to_oop(copy);
1341
1342 // Relativize stack chunks before publishing the copy. After the forwarding CAS,
1343 // mutators can see the copy and thaw it via the fast path if flags == 0. We must
1344 // relativize derived pointers and set gc_mode before that happens. Skip if the
1345 // copy's mark word is already a forwarding pointer (another thread won the race
1346 // and overwrote the original's header before we copied it).
1347 if (!ShenandoahForwarding::is_forwarded(copy_val)) {
1348 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1349 }
1350
1351 // Try to install the new forwarding pointer.
1352 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1353 if (result == copy_val) {
1354 // Successfully evacuated. Our copy is now the public one!
1355 shenandoah_assert_correct(nullptr, copy_val);
1356 if (ShenandoahEvacTracking) {
1357 evac_tracker()->end_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1358 }
1359 return copy_val;
1360 } else {
1361 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1362 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1363 // But if it happens to contain references to evacuated regions, those references would
1364 // not get updated for this stale copy during this cycle, and we will crash while scanning
1365 // it the next cycle.
1366 if (alloc_from_lab) {
1367 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1368 // object will overwrite this stale copy, or the filler object on LAB retirement will
1369 // do this.
1370 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1371 } else {
1372 // For non-LAB allocations, we have no way to retract the allocation, and
1373 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1374 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1375 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1376 fill_with_object(copy, size);
1377 shenandoah_assert_correct(nullptr, copy_val);
1378 // For non-LAB allocations, the object has already been registered
1379 }
1380 shenandoah_assert_correct(nullptr, result);
1381 return result;
1382 }
1383 }
1384
1385 // Clear the self_fwd bit on a live cset object, if set. Runs at a safepoint,
1386 // so a plain store is sufficient — no concurrent writers to the mark word.
1387 class ShenandoahUnSelfForwardObjectClosure : public ObjectClosure {
1388 public:
1389 void do_object(oop obj) override {
1390 markWord m = obj->mark();
1391 if (m.is_self_forwarded()) {
1392 obj->set_mark(m.unset_self_forwarded());
1393 }
1394 }
1395 };
1396
1397 // Parallel task over flagged cset regions. Iterates the live objects via the
1398 // mark bitmap (skipping evacuated and never-marked memory), clears self_fwd
1399 // bits, and resets the region flag once done.
1400 class ShenandoahUnSelfForwardTask : public WorkerTask {
1401 private:
1402 ShenandoahHeap* const _heap;
1403 ShenandoahCollectionSet* const _cs;
1404
1405 public:
1406 ShenandoahUnSelfForwardTask(ShenandoahHeap* heap, ShenandoahCollectionSet* cs) :
1407 WorkerTask("Shenandoah Un-Self-Forward"),
1408 _heap(heap),
1409 _cs(cs) {}
1410
1411 void work(uint worker_id) override {
1412 ShenandoahParallelWorkerSession worker_session(worker_id);
1413 ShenandoahUnSelfForwardObjectClosure cl;
1414 ShenandoahHeapRegion* r;
1415 while ((r = _cs->claim_next()) != nullptr) {
1416 if (r->has_self_forwards()) {
1417 _heap->marked_object_iterate(r, &cl);
1418 r->clear_has_self_forwards();
1419 }
1420 }
1421 }
1422 };
1423
1424 void ShenandoahHeap::un_self_forward_cset_regions() {
1425 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1426 ShenandoahCollectionSet* cs = collection_set();
1427 if (cs == nullptr || cs->is_empty()) {
1428 return;
1429 }
1430 cs->clear_current_index();
1431 ShenandoahUnSelfForwardTask task(this, cs);
1432 workers()->run_task(&task);
1433 DEBUG_ONLY(assert_no_self_forwards());
1434 }
1435
1436 #ifdef ASSERT
1437 void ShenandoahHeap::assert_no_self_forwards() const {
1438 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1439 ShenandoahCollectionSet* cs = collection_set();
1440 if (cs == nullptr) return;
1441 cs->clear_current_index();
1442 ShenandoahHeapRegion* r;
1443 while ((r = cs->next()) != nullptr) {
1444 assert(!r->has_self_forwards(), "region still flagged after drain");
1445 }
1446 cs->clear_current_index();
1447 }
1448 #endif
1449
1450 void ShenandoahHeap::trash_cset_regions() {
1451 ShenandoahHeapLocker locker(lock());
1452
1453 ShenandoahCollectionSet* set = collection_set();
1454 ShenandoahHeapRegion* r;
1455 set->clear_current_index();
1456 while ((r = set->next()) != nullptr) {
1457 r->make_trash();
1458 }
1459 collection_set()->clear();
1460 }
1461
1462 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1463 st->print_cr("Heap Regions:");
1464 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1465 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1466 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1467 st->print_cr("UWM=update watermark, U=used");
1468 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1469 st->print_cr("S=shared allocs, L=live data");
1470 st->print_cr("CP=critical pins");
1471
1472 for (size_t i = 0; i < num_regions(); i++) {
1473 get_region(i)->print_on(st);
1474 }
1475 }
1476
1477 void ShenandoahHeap::process_gc_stats() const {
1478 // Commit worker statistics to cycle data
1479 phase_timings()->flush_par_workers_to_cycle();
1480
1481 // Print GC stats for current cycle
1482 LogTarget(Info, gc, stats) lt;
1483 if (lt.is_enabled()) {
1484 ResourceMark rm;
1485 LogStream ls(lt);
1486 phase_timings()->print_cycle_on(&ls);
1487 if (ShenandoahEvacTracking) {
1488 ShenandoahCycleStats evac_stats = evac_tracker()->flush_cycle_to_global();
1489 evac_tracker()->print_evacuations_on(&ls, &evac_stats.workers,
1490 &evac_stats.mutators);
1491 }
1492 }
1493
1494 // Commit statistics to globals
1495 phase_timings()->flush_cycle_to_global();
1496 }
1497
1498 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) const {
1499 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1500 assert(!start->has_live(), "liveness must be zero");
1501
1502 // Do not try to get the size of this humongous object. STW collections will
1503 // have already unloaded classes, so an unmarked object may have a bad klass pointer.
1504 ShenandoahHeapRegion* region = start;
1505 size_t index = region->index();
1506 do {
1507 assert(region->is_humongous(), "Expect correct humongous start or continuation");
1508 assert(!region->is_cset(), "Humongous region should not be in collection set");
1509 region->make_trash_immediate();
1510 region = get_region(++index);
1511 } while (region != nullptr && region->is_humongous_continuation());
1512
1513 // Return number of regions trashed
1514 return index - start->index();
1515 }
1516
1517 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1518 public:
1519 ShenandoahCheckCleanGCLABClosure() {}
1520 void do_thread(Thread* thread) {
1521 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1522 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1523 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1524
1525 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1526 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1527 assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1528 assert(shenandoah_plab->plab()->words_remaining() == 0, "PLAB should not need retirement");
1529 }
1530 }
1531 };
1532
1533 void ShenandoahHeap::labs_make_parsable() {
1534 assert(UseTLAB, "Only call with UseTLAB");
1535
1536 ShenandoahRetireGCLABClosure cl(false);
1537
1538 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1539 ThreadLocalAllocBuffer& tlab = t->tlab();
1540 tlab.make_parsable();
1541 if (ZeroTLAB) {
1542 t->retire_tlab();
1543 }
1544 cl.do_thread(t);
1545 }
1546
1547 workers()->threads_do(&cl);
1548
1549 if (safepoint_workers() != nullptr) {
1550 safepoint_workers()->threads_do(&cl);
1551 }
1552 }
1553
1554 void ShenandoahHeap::tlabs_retire(bool resize) {
1555 assert(UseTLAB, "Only call with UseTLAB");
1556 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1557
1558 ThreadLocalAllocStats stats;
1559
1560 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1561 t->retire_tlab(&stats);
1562 if (resize) {
1563 t->tlab().resize();
1564 }
1565 }
1566
1567 stats.publish();
1568
1569 #ifdef ASSERT
1570 ShenandoahCheckCleanGCLABClosure cl;
1571 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1572 cl.do_thread(t);
1573 }
1574 workers()->threads_do(&cl);
1575 #endif
1576 }
1577
1578 void ShenandoahHeap::gclabs_retire(bool resize) {
1579 assert(UseTLAB, "Only call with UseTLAB");
1580 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1581
1582 ShenandoahRetireGCLABClosure cl(resize);
1583 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1584 cl.do_thread(t);
1585 }
1586
1587 workers()->threads_do(&cl);
1588
1589 if (safepoint_workers() != nullptr) {
1590 safepoint_workers()->threads_do(&cl);
1591 }
1592 }
1593
1594 // Returns size in bytes
1595 size_t ShenandoahHeap::unsafe_max_tlab_alloc() const {
1596 // Return the max allowed size, and let the allocation path
1597 // figure out the safe size for current allocation.
1598 return ShenandoahHeapRegion::max_tlab_size_bytes();
1599 }
1600
1601 size_t ShenandoahHeap::max_tlab_size() const {
1602 // Returns size in words
1603 return ShenandoahHeapRegion::max_tlab_size_words();
1604 }
1605
1606 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) {
1607 // These requests are ignored because we can't easily have Shenandoah jump into
1608 // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent
1609 // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly
1610 // on the VM thread, but this would confuse the control thread mightily and doesn't
1611 // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a
1612 // concurrent cycle in the prologue of the heap inspect/dump operation (see VM_HeapDumper::doit_prologue).
1613 // This is how other concurrent collectors in the JVM handle this scenario as well.
1614 assert(Thread::current()->is_VM_thread(), "Should be the VM thread");
1615 guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause");
1616 }
1617
1618 void ShenandoahHeap::collect(GCCause::Cause cause) {
1619 control_thread()->request_gc(cause);
1620 }
1621
1622 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1623 // This method is only called by `CollectedHeap::collect_as_vm_thread`, which we have
1624 // overridden to do nothing. See the comment there for an explanation of how heap inspections
1625 // work for Shenandoah.
1626 ShouldNotReachHere();
1627 }
1628
1629 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1630 ShenandoahHeapRegion* r = heap_region_containing(addr);
1631 if (r != nullptr) {
1632 return r->block_start(addr);
1633 }
1634 return nullptr;
1635 }
1636
1637 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1638 ShenandoahHeapRegion* r = heap_region_containing(addr);
1639 return r->block_is_obj(addr);
1640 }
1641
1642 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1643 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1644 }
1645
1646 void ShenandoahHeap::prepare_for_verify() {
1647 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1648 labs_make_parsable();
1649 }
1650 }
1651
1652 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1653 if (_shenandoah_policy->is_at_shutdown()) {
1654 return;
1655 }
1656
1657 if (_control_thread != nullptr) {
1658 tcl->do_thread(_control_thread);
1659 }
1660
1661 if (_uncommit_thread != nullptr) {
1662 tcl->do_thread(_uncommit_thread);
1663 }
1664
1665 workers()->threads_do(tcl);
1666 if (_safepoint_workers != nullptr) {
1667 _safepoint_workers->threads_do(tcl);
1668 }
1669 }
1670
1671 void ShenandoahHeap::print_tracing_info() const {
1672 LogTarget(Info, gc, stats) lt;
1673 if (lt.is_enabled()) {
1674 ResourceMark rm;
1675 LogStream ls(lt);
1676
1677 if (ShenandoahEvacTracking) {
1678 evac_tracker()->print_global_on(&ls);
1679 ls.cr();
1680 ls.cr();
1681 }
1682
1683 phase_timings()->print_global_on(&ls);
1684
1685 ls.cr();
1686 ls.cr();
1687
1688 shenandoah_policy()->print_gc_stats(&ls);
1689
1690 ls.cr();
1691 ls.cr();
1692 }
1693 }
1694
1695 // Active generation may only be set by the VM thread at a safepoint.
1696 void ShenandoahHeap::set_active_generation(ShenandoahGeneration* generation) {
1697 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1698 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1699 _active_generation = generation;
1700 }
1701
1702 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation,
1703 bool is_degenerated, bool is_out_of_cycle) {
1704 shenandoah_policy()->record_collection_cause(cause);
1705
1706 const GCCause::Cause current = gc_cause();
1707 assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s",
1708 GCCause::to_string(current), GCCause::to_string(cause));
1709
1710 set_gc_cause(cause);
1711
1712 if (is_degenerated) {
1713 generation->heuristics()->record_degenerated_cycle_start(is_out_of_cycle);
1714 } else {
1715 generation->heuristics()->record_cycle_start();
1716 }
1717 }
1718
1719 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1720 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1721
1722 generation->heuristics()->record_cycle_end();
1723 if (mode()->is_generational() && generation->is_global()) {
1724 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1725 young_generation()->heuristics()->record_cycle_end();
1726 old_generation()->heuristics()->record_cycle_end();
1727 }
1728
1729 set_gc_cause(GCCause::_no_gc);
1730 }
1731
1732 void ShenandoahHeap::verify(VerifyOption vo) {
1733 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1734 if (ShenandoahVerify) {
1735 verifier()->verify_generic(active_generation(), vo);
1736 } else {
1737 // TODO: Consider allocating verification bitmaps on demand,
1738 // and turn this on unconditionally.
1739 }
1740 }
1741 }
1742 size_t ShenandoahHeap::tlab_capacity() const {
1743 return _free_set->capacity_not_holding_lock();
1744 }
1745
1746 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1747 private:
1748 MarkBitMap* _bitmap;
1749 ShenandoahScanObjectStack* _oop_stack;
1750 ShenandoahHeap* const _heap;
1751 ShenandoahMarkingContext* const _marking_context;
1752
1753 template <class T>
1754 void do_oop_work(T* p) {
1755 T o = RawAccess<>::oop_load(p);
1756 if (!CompressedOops::is_null(o)) {
1757 oop obj = CompressedOops::decode_not_null(o);
1758 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1759 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1760 return;
1761 }
1762 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1763
1764 assert(oopDesc::is_oop(obj), "must be a valid oop");
1765 if (!_bitmap->is_marked(obj)) {
1766 _bitmap->mark(obj);
1767 _oop_stack->push(obj);
1768 }
1769 }
1770 }
1771 public:
1772 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1773 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1774 _marking_context(_heap->marking_context()) {}
1775 void do_oop(oop* p) { do_oop_work(p); }
1776 void do_oop(narrowOop* p) { do_oop_work(p); }
1777 };
1778
1779 /*
1780 * This is public API, used in preparation of object_iterate().
1781 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1782 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1783 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1784 */
1785 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1786 // No-op.
1787 }
1788
1789 /*
1790 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1791 *
1792 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1793 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1794 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1795 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1796 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1797 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1798 * wiped the bitmap in preparation for next marking).
1799 *
1800 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1801 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1802 * is allowed to report dead objects, but is not required to do so.
1803 */
1804 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1805 // Reset bitmap
1806 if (!prepare_aux_bitmap_for_iteration())
1807 return;
1808
1809 ShenandoahScanObjectStack oop_stack;
1810 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1811 // Seed the stack with root scan
1812 scan_roots_for_iteration(&oop_stack, &oops);
1813
1814 // Work through the oop stack to traverse heap
1815 while (! oop_stack.is_empty()) {
1816 oop obj = oop_stack.pop();
1817 assert(oopDesc::is_oop(obj), "must be a valid oop");
1818 cl->do_object(obj);
1819 obj->oop_iterate(&oops);
1820 }
1821
1822 assert(oop_stack.is_empty(), "should be empty");
1823 // Reclaim bitmap
1824 reclaim_aux_bitmap_for_iteration();
1825 }
1826
1827 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1828 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1829 if (!_aux_bitmap_region_special) {
1830 bool success = os::commit_memory((char *) _aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false);
1831 if (!success) {
1832 log_warning(gc)("Auxiliary marking bitmap commit failed: " PTR_FORMAT " (%zu bytes)",
1833 p2i(_aux_bitmap_region.start()), _aux_bitmap_region.byte_size());
1834 return false;
1835 }
1836 }
1837 _aux_bit_map.clear();
1838 return true;
1839 }
1840
1841 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1842 // Process GC roots according to current GC cycle
1843 // This populates the work stack with initial objects
1844 // It is important to relinquish the associated locks before diving
1845 // into heap dumper
1846 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1847 ShenandoahHeapIterationRootScanner rp(n_workers);
1848 rp.roots_do(oops);
1849 }
1850
1851 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1852 if (!_aux_bitmap_region_special) {
1853 os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size());
1854 }
1855 }
1856
1857 // Closure for parallelly iterate objects
1858 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1859 private:
1860 MarkBitMap* _bitmap;
1861 ShenandoahObjToScanQueue* _queue;
1862 ShenandoahHeap* const _heap;
1863 ShenandoahMarkingContext* const _marking_context;
1864
1865 template <class T>
1866 void do_oop_work(T* p) {
1867 T o = RawAccess<>::oop_load(p);
1868 if (!CompressedOops::is_null(o)) {
1869 oop obj = CompressedOops::decode_not_null(o);
1870 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1871 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1872 return;
1873 }
1874 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1875
1876 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1877 if (_bitmap->par_mark(obj)) {
1878 _queue->push(ShenandoahMarkTask(obj));
1879 }
1880 }
1881 }
1882 public:
1883 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1884 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1885 _marking_context(_heap->marking_context()) {}
1886 void do_oop(oop* p) { do_oop_work(p); }
1887 void do_oop(narrowOop* p) { do_oop_work(p); }
1888 };
1889
1890 // Object iterator for parallel heap iteraion.
1891 // The root scanning phase happenes in construction as a preparation of
1892 // parallel marking queues.
1893 // Every worker processes it's own marking queue. work-stealing is used
1894 // to balance workload.
1895 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1896 private:
1897 uint _num_workers;
1898 bool _init_ready;
1899 MarkBitMap* _aux_bit_map;
1900 ShenandoahHeap* _heap;
1901 ShenandoahScanObjectStack _roots_stack; // global roots stack
1902 ShenandoahObjToScanQueueSet* _task_queues;
1903 public:
1904 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1905 _num_workers(num_workers),
1906 _init_ready(false),
1907 _aux_bit_map(bitmap),
1908 _heap(ShenandoahHeap::heap()) {
1909 // Initialize bitmap
1910 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1911 if (!_init_ready) {
1912 return;
1913 }
1914
1915 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1916 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1917
1918 _init_ready = prepare_worker_queues();
1919 }
1920
1921 ~ShenandoahParallelObjectIterator() {
1922 // Reclaim bitmap
1923 _heap->reclaim_aux_bitmap_for_iteration();
1924 // Reclaim queue for workers
1925 if (_task_queues!= nullptr) {
1926 for (uint i = 0; i < _num_workers; ++i) {
1927 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1928 if (q != nullptr) {
1929 delete q;
1930 _task_queues->register_queue(i, nullptr);
1931 }
1932 }
1933 delete _task_queues;
1934 _task_queues = nullptr;
1935 }
1936 }
1937
1938 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1939 if (_init_ready) {
1940 object_iterate_parallel(cl, worker_id, _task_queues);
1941 }
1942 }
1943
1944 private:
1945 // Divide global root_stack into worker queues
1946 bool prepare_worker_queues() {
1947 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1948 // Initialize queues for every workers
1949 for (uint i = 0; i < _num_workers; ++i) {
1950 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1951 _task_queues->register_queue(i, task_queue);
1952 }
1953 // Divide roots among the workers. Assume that object referencing distribution
1954 // is related with root kind, use round-robin to make every worker have same chance
1955 // to process every kind of roots
1956 size_t roots_num = _roots_stack.size();
1957 if (roots_num == 0) {
1958 // No work to do
1959 return false;
1960 }
1961
1962 for (uint j = 0; j < roots_num; j++) {
1963 uint stack_id = j % _num_workers;
1964 oop obj = _roots_stack.pop();
1965 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1966 }
1967 return true;
1968 }
1969
1970 void object_iterate_parallel(ObjectClosure* cl,
1971 uint worker_id,
1972 ShenandoahObjToScanQueueSet* queue_set) {
1973 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1974 assert(queue_set != nullptr, "task queue must not be null");
1975
1976 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1977 assert(q != nullptr, "object iterate queue must not be null");
1978
1979 ShenandoahMarkTask t;
1980 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1981
1982 // Work through the queue to traverse heap.
1983 // Steal when there is no task in queue.
1984 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1985 oop obj = t.obj();
1986 assert(oopDesc::is_oop(obj), "must be a valid oop");
1987 cl->do_object(obj);
1988 obj->oop_iterate(&oops);
1989 }
1990 assert(q->is_empty(), "should be empty");
1991 }
1992 };
1993
1994 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1995 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1996 }
1997
1998 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1999 void ShenandoahHeap::keep_alive(oop obj) {
2000 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
2001 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
2002 }
2003 }
2004
2005 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2006 for (size_t i = 0; i < num_regions(); i++) {
2007 ShenandoahHeapRegion* current = get_region(i);
2008 blk->heap_region_do(current);
2009 }
2010 }
2011
2012 class ShenandoahHeapRegionIteratorTask : public WorkerTask {
2013 private:
2014 ShenandoahRegionIterator _regions;
2015 ShenandoahHeapRegionClosure* _closure;
2016
2017 public:
2018 ShenandoahHeapRegionIteratorTask(ShenandoahHeapRegionClosure* closure)
2019 : WorkerTask("Shenandoah Heap Region Iterator")
2020 , _closure(closure) {}
2021
2022 void work(uint worker_id) override {
2023 ShenandoahParallelWorkerSession worker_session(worker_id);
2024 ShenandoahHeapRegion* region = _regions.next();
2025 while (region != nullptr) {
2026 _closure->heap_region_do(region);
2027 region = _regions.next();
2028 }
2029 }
2030 };
2031
2032 class ShenandoahParallelHeapRegionTask : public WorkerTask {
2033 private:
2034 ShenandoahHeap* const _heap;
2035 ShenandoahHeapRegionClosure* const _blk;
2036 size_t const _stride;
2037
2038 shenandoah_padding(0);
2039 Atomic<size_t> _index;
2040 shenandoah_padding(1);
2041
2042 public:
2043 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
2044 WorkerTask("Shenandoah Parallel Region Operation"),
2045 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
2046
2047 void work(uint worker_id) {
2048 ShenandoahParallelWorkerSession worker_session(worker_id);
2049 size_t stride = _stride;
2050
2051 size_t max = _heap->num_regions();
2052 while (_index.load_relaxed() < max) {
2053 size_t cur = _index.fetch_then_add(stride, memory_order_relaxed);
2054 size_t start = cur;
2055 size_t end = MIN2(cur + stride, max);
2056 if (start >= max) break;
2057
2058 for (size_t i = cur; i < end; i++) {
2059 ShenandoahHeapRegion* current = _heap->get_region(i);
2060 _blk->heap_region_do(current);
2061 }
2062 }
2063 }
2064 };
2065
2066 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2067 assert(blk->is_thread_safe(), "Only thread-safe closures here");
2068 const uint active_workers = workers()->active_workers();
2069 const size_t n_regions = num_regions();
2070 size_t stride = blk->parallel_region_stride();
2071 if (stride == 0 && active_workers > 1) {
2072 // Automatically derive the stride to balance the work between threads
2073 // evenly. Do not try to split work if below the reasonable threshold.
2074 constexpr size_t threshold = 4096;
2075 stride = n_regions <= threshold ?
2076 threshold :
2077 (n_regions + active_workers - 1) / active_workers;
2078 }
2079
2080 if (n_regions > stride && active_workers > 1) {
2081 ShenandoahParallelHeapRegionTask task(blk, stride);
2082 workers()->run_task(&task);
2083 } else {
2084 heap_region_iterate(blk);
2085 }
2086 }
2087
2088 void ShenandoahHeap::heap_region_iterator(ShenandoahHeapRegionClosure* closure) const {
2089 ShenandoahHeapRegionIteratorTask task(closure);
2090 workers()->run_task(&task);
2091 }
2092
2093 class ShenandoahRendezvousHandshakeClosure : public HandshakeClosure {
2094 public:
2095 inline ShenandoahRendezvousHandshakeClosure(const char* name) : HandshakeClosure(name) {}
2096 inline void do_thread(Thread* thread) {}
2097 };
2098
2099 void ShenandoahHeap::rendezvous_threads(const char* name) {
2100 ShenandoahRendezvousHandshakeClosure cl(name);
2101 Handshake::execute(&cl);
2102 }
2103
2104 void ShenandoahHeap::recycle_trash() {
2105 free_set()->recycle_trash();
2106 }
2107
2108 void ShenandoahHeap::do_class_unloading() {
2109 _unloader.unload();
2110 if (mode()->is_generational()) {
2111 old_generation()->set_parsable(false);
2112 }
2113 }
2114
2115 void ShenandoahHeap::stw_weak_refs(ShenandoahGeneration* generation, bool full_gc) {
2116 // Weak refs processing
2117 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2118 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2119 ShenandoahTimingsTracker t(phase);
2120 ShenandoahGCWorkerPhase worker_phase(phase);
2121 generation->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2122 }
2123
2124 void ShenandoahHeap::prepare_update_heap_references() {
2125 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2126
2127 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2128 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2129 // for future GCLABs here.
2130 if (UseTLAB) {
2131 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2132 gclabs_retire(ResizeTLAB);
2133 }
2134
2135 _update_refs_iterator.reset();
2136 }
2137
2138 void ShenandoahHeap::propagate_gc_state_to_all_threads() {
2139 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2140 if (_gc_state_changed) {
2141 // If we are only marking old, we do not need to process young pointers
2142 ShenandoahBarrierSet::satb_mark_queue_set().set_filter_out_young(
2143 is_concurrent_old_mark_in_progress() && !is_concurrent_young_mark_in_progress()
2144 );
2145 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
2146 Threads::threads_do(&propagator);
2147 _gc_state_changed = false;
2148 }
2149 }
2150
2151 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) {
2152 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2153 _gc_state.set_cond(mask, value);
2154 _gc_state_changed = true;
2155 }
2156
2157 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) {
2158 // Holding the thread lock here assures that any thread created after we change the gc
2159 // state will have the correct state. It also prevents attaching threads from seeing
2160 // an inconsistent state. See ShenandoahBarrierSet::on_thread_attach for reference. Established
2161 // threads will use their thread local copy of the gc state (changed by a handshake, or on a
2162 // safepoint).
2163 assert(Threads_lock->is_locked(), "Must hold thread lock for concurrent gc state change");
2164 _gc_state.set_cond(mask, value);
2165 }
2166
2167 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2168 uint mask;
2169 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2170 if (!in_progress && is_concurrent_old_mark_in_progress()) {
2171 assert(mode()->is_generational(), "Only generational GC has old marking");
2172 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2173 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2174 mask = YOUNG_MARKING;
2175 } else {
2176 mask = MARKING | YOUNG_MARKING;
2177 }
2178 set_gc_state_at_safepoint(mask, in_progress);
2179 manage_satb_barrier(in_progress);
2180 }
2181
2182 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2183 #ifdef ASSERT
2184 // has_forwarded_objects() iff UPDATE_REFS or EVACUATION
2185 bool has_forwarded = has_forwarded_objects();
2186 bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION);
2187 bool evacuating = _gc_state.is_set(EVACUATION);
2188 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2189 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2190 #endif
2191 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2192 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2193 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2194 set_gc_state_at_safepoint(OLD_MARKING, in_progress);
2195 } else {
2196 set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress);
2197 }
2198 manage_satb_barrier(in_progress);
2199 }
2200
2201 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2202 return old_generation()->is_preparing_for_mark();
2203 }
2204
2205 void ShenandoahHeap::manage_satb_barrier(bool active) {
2206 if (is_concurrent_mark_in_progress()) {
2207 // Ignore request to deactivate barrier while concurrent mark is in progress.
2208 // Do not attempt to re-activate the barrier if it is already active.
2209 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2210 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2211 }
2212 } else {
2213 // No concurrent marking is in progress so honor request to deactivate,
2214 // but only if the barrier is already active.
2215 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2216 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2217 }
2218 }
2219 }
2220
2221 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2222 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2223 set_gc_state_at_safepoint(EVACUATION, in_progress);
2224 }
2225
2226 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2227 if (in_progress) {
2228 _concurrent_strong_root_in_progress.set();
2229 } else {
2230 _concurrent_strong_root_in_progress.unset();
2231 }
2232 }
2233
2234 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2235 set_gc_state_at_safepoint(WEAK_ROOTS, cond);
2236 }
2237
2238 GCTracer* ShenandoahHeap::tracer() {
2239 return shenandoah_policy()->tracer();
2240 }
2241
2242 size_t ShenandoahHeap::tlab_used() const {
2243 return _free_set->used_not_holding_lock();
2244 }
2245
2246 bool ShenandoahHeap::try_cancel_gc(GCCause::Cause cause) {
2247 const GCCause::Cause prev = _cancelled_gc.xchg(cause);
2248 return prev == GCCause::_no_gc || prev == GCCause::_shenandoah_concurrent_gc;
2249 }
2250
2251 void ShenandoahHeap::cancel_concurrent_mark() {
2252 if (mode()->is_generational()) {
2253 young_generation()->cancel_marking();
2254 old_generation()->cancel_marking();
2255 }
2256
2257 global_generation()->cancel_marking();
2258
2259 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2260 }
2261
2262 bool ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2263 if (try_cancel_gc(cause)) {
2264 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2265 log_info(gc,thread)("%s", msg.buffer());
2266 Events::log(Thread::current(), "%s", msg.buffer());
2267 _cancel_requested_time = os::elapsedTime();
2268 return true;
2269 }
2270 return false;
2271 }
2272
2273 uint ShenandoahHeap::max_workers() {
2274 return _max_workers;
2275 }
2276
2277 void ShenandoahHeap::stop() {
2278 // The shutdown sequence should be able to terminate when GC is running.
2279
2280 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2281 _shenandoah_policy->record_shutdown();
2282
2283 // Step 1. Stop reporting on gc thread cpu utilization
2284 mmu_tracker()->stop();
2285
2286 // Step 2. Stop decaying allocation rate.
2287 _alloc_rate_decay.disenroll();
2288
2289 // Step 3. Wait until GC worker exits normally (this will cancel any ongoing GC).
2290 control_thread()->stop();
2291
2292 // Step 4. Shutdown uncommit thread.
2293 if (_uncommit_thread != nullptr) {
2294 _uncommit_thread->stop();
2295 }
2296 }
2297
2298 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2299 if (!unload_classes()) return;
2300 ClassUnloadingContext ctx(_workers->active_workers(),
2301 true /* unregister_nmethods_during_purge */,
2302 false /* lock_nmethod_free_separately */);
2303
2304 // Unload classes and purge SystemDictionary.
2305 {
2306 ShenandoahPhaseTimings::Phase phase = full_gc ?
2307 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2308 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2309 ShenandoahIsAliveSelector is_alive;
2310 {
2311 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2312 ShenandoahGCPhase gc_phase(phase);
2313 ShenandoahGCWorkerPhase worker_phase(phase);
2314 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2315
2316 ShenandoahClassUnloadingTask unlink_task(phase, unloading_occurred);
2317 _workers->run_task(&unlink_task);
2318 }
2319 // Release unloaded nmethods's memory.
2320 ClassUnloadingContext::context()->purge_and_free_nmethods();
2321 }
2322
2323 {
2324 ShenandoahGCPhase phase(full_gc ?
2325 ShenandoahPhaseTimings::full_gc_purge_cldg :
2326 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2327 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2328 }
2329 // Resize and verify metaspace
2330 MetaspaceGC::compute_new_size();
2331
2332 if (mode()->is_generational()) {
2333 old_generation()->set_parsable(false);
2334 }
2335
2336 DEBUG_ONLY(MetaspaceUtils::verify();)
2337 }
2338
2339 // Weak roots are either pre-evacuated (final mark) or updated (final update refs),
2340 // so they should not have forwarded oops.
2341 // However, we do need to "null" dead oops in the roots, if can not be done
2342 // in concurrent cycles.
2343 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2344 uint num_workers = _workers->active_workers();
2345 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2346 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2347 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2348 ShenandoahGCPhase phase(timing_phase);
2349 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2350 // Cleanup weak roots
2351 if (has_forwarded_objects()) {
2352 ShenandoahForwardedIsAliveClosure is_alive;
2353 ShenandoahNonConcUpdateRefsClosure keep_alive;
2354 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2355 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2356 _workers->run_task(&cleaning_task);
2357 } else {
2358 ShenandoahIsAliveClosure is_alive;
2359 #ifdef ASSERT
2360 ShenandoahAssertNotForwardedClosure verify_cl;
2361 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2362 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2363 #else
2364 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2365 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2366 #endif
2367 _workers->run_task(&cleaning_task);
2368 }
2369 }
2370
2371 void ShenandoahHeap::parallel_cleaning(ShenandoahGeneration* generation, bool full_gc) {
2372 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2373 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2374 ShenandoahGCPhase phase(full_gc ?
2375 ShenandoahPhaseTimings::full_gc_purge :
2376 ShenandoahPhaseTimings::degen_gc_purge);
2377 stw_weak_refs(generation, full_gc);
2378 stw_process_weak_roots(full_gc);
2379 stw_unload_classes(full_gc);
2380 }
2381
2382 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2383 set_gc_state_at_safepoint(HAS_FORWARDED, cond);
2384 }
2385
2386 void ShenandoahHeap::set_unload_classes(bool uc) {
2387 _unload_classes.set_cond(uc);
2388 }
2389
2390 bool ShenandoahHeap::unload_classes() const {
2391 return _unload_classes.is_set();
2392 }
2393
2394 address ShenandoahHeap::in_cset_fast_test_addr() {
2395 ShenandoahHeap* heap = ShenandoahHeap::heap();
2396 assert(heap->collection_set() != nullptr, "Sanity");
2397 return (address) heap->collection_set()->biased_map_address();
2398 }
2399
2400 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2401 _degenerated_gc_in_progress.set_cond(in_progress);
2402 }
2403
2404 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2405 _full_gc_in_progress.set_cond(in_progress);
2406 }
2407
2408 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2409 assert (is_full_gc_in_progress(), "should be");
2410 _full_gc_move_in_progress.set_cond(in_progress);
2411 }
2412
2413 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2414 set_gc_state_at_safepoint(UPDATE_REFS, in_progress);
2415 }
2416
2417 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2418 ShenandoahCodeRoots::register_nmethod(nm);
2419 }
2420
2421 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2422 ShenandoahCodeRoots::unregister_nmethod(nm);
2423 }
2424
2425 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2426 heap_region_containing(o)->record_pin();
2427 }
2428
2429 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2430 ShenandoahHeapRegion* r = heap_region_containing(o);
2431 assert(r != nullptr, "Sanity");
2432 assert(r->pin_count() > 0, "Region %zu should have non-zero pins", r->index());
2433 r->record_unpin();
2434 }
2435
2436 void ShenandoahHeap::sync_pinned_region_status() {
2437 ShenandoahHeapLocker locker(lock());
2438
2439 for (size_t i = 0; i < num_regions(); i++) {
2440 ShenandoahHeapRegion *r = get_region(i);
2441 if (r->is_active()) {
2442 if (r->is_pinned()) {
2443 if (r->pin_count() == 0) {
2444 r->make_unpinned();
2445 }
2446 } else {
2447 if (r->pin_count() > 0) {
2448 r->make_pinned();
2449 }
2450 }
2451 }
2452 }
2453
2454 assert_pinned_region_status();
2455 }
2456
2457 #ifdef ASSERT
2458 void ShenandoahHeap::assert_pinned_region_status() const {
2459 assert_pinned_region_status(global_generation());
2460 }
2461
2462 void ShenandoahHeap::assert_pinned_region_status(ShenandoahGeneration* generation) const {
2463 for (size_t i = 0; i < num_regions(); i++) {
2464 ShenandoahHeapRegion* r = get_region(i);
2465 if (generation->contains(r)) {
2466 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2467 "Region %zu pinning status is inconsistent", i);
2468 }
2469 }
2470 }
2471 #endif
2472
2473 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2474 return _gc_timer;
2475 }
2476
2477 void ShenandoahHeap::prepare_concurrent_roots() {
2478 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2479 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2480 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2481 set_concurrent_weak_root_in_progress(true);
2482 if (unload_classes()) {
2483 _unloader.prepare();
2484 }
2485 }
2486
2487 void ShenandoahHeap::finish_concurrent_roots() {
2488 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2489 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2490 if (unload_classes()) {
2491 _unloader.finish();
2492 }
2493 }
2494
2495 #ifdef ASSERT
2496 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2497 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2498
2499 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2500 // Use ParallelGCThreads inside safepoints
2501 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2502 ParallelGCThreads, nworkers);
2503 } else {
2504 // Use ConcGCThreads outside safepoints
2505 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2506 ConcGCThreads, nworkers);
2507 }
2508 }
2509 #endif
2510
2511 ShenandoahVerifier* ShenandoahHeap::verifier() {
2512 guarantee(ShenandoahVerify, "Should be enabled");
2513 assert (_verifier != nullptr, "sanity");
2514 return _verifier;
2515 }
2516
2517 template<bool CONCURRENT>
2518 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2519 private:
2520 ShenandoahHeap* _heap;
2521 ShenandoahRegionIterator* _regions;
2522 public:
2523 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2524 WorkerTask("Shenandoah Update References"),
2525 _heap(ShenandoahHeap::heap()),
2526 _regions(regions) {
2527 }
2528
2529 void work(uint worker_id) {
2530 if (CONCURRENT) {
2531 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
2532 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2533 SuspendibleThreadSetJoiner stsj;
2534 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2535 } else {
2536 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
2537 ShenandoahParallelWorkerSession worker_session(worker_id);
2538 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2539 }
2540 }
2541
2542 private:
2543 template<class T>
2544 void do_work(uint worker_id) {
2545 if (CONCURRENT && (worker_id == 0)) {
2546 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2547 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2548 size_t cset_regions = _heap->collection_set()->count();
2549
2550 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2551 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2552 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2553 // next GC cycle.
2554 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2555 }
2556 // If !CONCURRENT, there's no value in expanding Mutator free set
2557 T cl;
2558 ShenandoahHeapRegion* r = _regions->next();
2559 while (r != nullptr) {
2560 HeapWord* update_watermark = r->get_update_watermark();
2561 assert (update_watermark >= r->bottom(), "sanity");
2562 if (r->is_active() && !r->is_cset()) {
2563 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2564 }
2565 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2566 return;
2567 }
2568 r = _regions->next();
2569 }
2570 }
2571 };
2572
2573 void ShenandoahHeap::update_heap_references(ShenandoahGeneration* generation, bool concurrent) {
2574 assert(generation->is_global(), "Should only get global generation here");
2575 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2576
2577 if (concurrent) {
2578 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2579 workers()->run_task(&task);
2580 } else {
2581 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2582 workers()->run_task(&task);
2583 }
2584 }
2585
2586 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2587 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2588 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2589
2590 {
2591 ShenandoahGCPhase phase(concurrent ?
2592 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2593 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2594
2595 final_update_refs_update_region_states();
2596
2597 assert_pinned_region_status();
2598 }
2599
2600 {
2601 ShenandoahGCPhase phase(concurrent ?
2602 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2603 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2604 trash_cset_regions();
2605 }
2606 }
2607
2608 void ShenandoahHeap::final_update_refs_update_region_states() {
2609 ShenandoahSynchronizePinnedRegionStates cl;
2610 parallel_heap_region_iterate(&cl);
2611 }
2612
2613 void ShenandoahHeap::rebuild_free_set_within_phase() {
2614 ShenandoahHeapLocker locker(lock());
2615 size_t young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count;
2616 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count);
2617 // If there are no old regions, first_old_region will be greater than last_old_region
2618 assert((first_old_region > last_old_region) ||
2619 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2620 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2621 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu",
2622 old_region_count, first_old_region, last_old_region);
2623
2624 if (mode()->is_generational()) {
2625 #ifdef ASSERT
2626 if (ShenandoahVerify) {
2627 verifier()->verify_before_rebuilding_free_set();
2628 }
2629 #endif
2630
2631 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2632 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2633 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2634 size_t allocation_runway =
2635 gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_trashed_regions);
2636 gen_heap->compute_old_generation_balance(allocation_runway, old_trashed_regions, young_trashed_regions);
2637 }
2638 // Rebuild free set based on adjusted generation sizes.
2639 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, old_region_count);
2640
2641 if (mode()->is_generational()) {
2642 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2643 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2644 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2645 }
2646 }
2647
2648 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2649 ShenandoahGCPhase phase(concurrent ?
2650 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2651 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2652 rebuild_free_set_within_phase();
2653 }
2654
2655 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2656 size_t slice = r->index() / _bitmap_regions_per_slice;
2657
2658 size_t regions_from = _bitmap_regions_per_slice * slice;
2659 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2660 for (size_t g = regions_from; g < regions_to; g++) {
2661 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2662 if (skip_self && g == r->index()) continue;
2663 if (get_region(g)->is_committed()) {
2664 return true;
2665 }
2666 }
2667 return false;
2668 }
2669
2670 void ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2671 shenandoah_assert_heaplocked();
2672 assert(!is_bitmap_region_special(), "Not for special memory");
2673
2674 if (is_bitmap_slice_committed(r, true)) {
2675 // Some other region from the group is already committed, meaning the bitmap
2676 // slice is already committed, we exit right away.
2677 return;
2678 }
2679
2680 // Commit the bitmap slice:
2681 size_t slice = r->index() / _bitmap_regions_per_slice;
2682 size_t off = _bitmap_bytes_per_slice * slice;
2683 size_t len = _bitmap_bytes_per_slice;
2684 char* start = (char*) _bitmap_region.start() + off;
2685
2686 os::commit_memory_or_exit(start, len, false, "Unable to commit bitmap slice");
2687
2688 if (AlwaysPreTouch) {
2689 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2690 }
2691 }
2692
2693 void ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2694 shenandoah_assert_heaplocked();
2695 assert(!is_bitmap_region_special(), "Not for special memory");
2696
2697 if (is_bitmap_slice_committed(r, true)) {
2698 // Some other region from the group is still committed, meaning the bitmap
2699 // slice should stay committed, exit right away.
2700 return;
2701 }
2702
2703 // Uncommit the bitmap slice:
2704 size_t slice = r->index() / _bitmap_regions_per_slice;
2705 size_t off = _bitmap_bytes_per_slice * slice;
2706 size_t len = _bitmap_bytes_per_slice;
2707
2708 char* addr = (char*) _bitmap_region.start() + off;
2709 os::uncommit_memory(addr, len);
2710 }
2711
2712 void ShenandoahHeap::forbid_uncommit() {
2713 if (_uncommit_thread != nullptr) {
2714 _uncommit_thread->forbid_uncommit();
2715 }
2716 }
2717
2718 void ShenandoahHeap::allow_uncommit() {
2719 if (_uncommit_thread != nullptr) {
2720 _uncommit_thread->allow_uncommit();
2721 }
2722 }
2723
2724 #ifdef ASSERT
2725 bool ShenandoahHeap::is_uncommit_in_progress() {
2726 if (_uncommit_thread != nullptr) {
2727 return _uncommit_thread->is_uncommit_in_progress();
2728 }
2729 return false;
2730 }
2731 #endif
2732
2733 void ShenandoahHeap::safepoint_synchronize_begin() {
2734 StackWatermarkSet::safepoint_synchronize_begin();
2735 SuspendibleThreadSet::synchronize();
2736 }
2737
2738 void ShenandoahHeap::safepoint_synchronize_end() {
2739 SuspendibleThreadSet::desynchronize();
2740 }
2741
2742 void ShenandoahHeap::try_inject_alloc_failure() {
2743 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2744 _inject_alloc_failure.set();
2745 os::naked_short_sleep(1);
2746 if (cancelled_gc()) {
2747 log_info(gc)("Allocation failure was successfully injected");
2748 }
2749 }
2750 }
2751
2752 bool ShenandoahHeap::should_inject_alloc_failure() {
2753 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2754 }
2755
2756 void ShenandoahHeap::try_inject_pin() {
2757 assert(!ShenandoahSafepoint::is_at_shenandoah_safepoint(), "try_inject_pin() must be called outside a safepoint.");
2758 assert(active_generation() != nullptr, "Active generation must be set before we inject pins.");
2759 assert(is_concurrent_mark_in_progress() || active_generation()->is_mark_complete(),
2760 "try_inject_pin() requires marking is in progress or has completed.");
2761 if (ShenandoahPinRegionRate && !cancelled_gc() && ((uintx)(os::random() % 1000) < ShenandoahPinRegionRate) &&
2762 _injected_pin_count < MAX_INJECTED_PINS) {
2763 const size_t idx = os::random() % num_regions();
2764 ShenandoahHeapRegion* r = get_region(idx);
2765 if ((r->is_regular() || r->is_humongous_start()) && r->has_live()) {
2766 r->record_pin();
2767 _injected_pin_indices[_injected_pin_count] = idx;
2768 _injected_pin_count++;
2769 }
2770 }
2771 }
2772
2773 void ShenandoahHeap::release_injected_pins() {
2774 if (_injected_pin_count == 0) {
2775 return;
2776 }
2777
2778 assert(_injected_pin_count <= MAX_INJECTED_PINS,
2779 "Injected pin count: %u exceeds max: %u.", _injected_pin_count, MAX_INJECTED_PINS);
2780 for (uint i = 0; i < _injected_pin_count; i++) {
2781 const size_t idx = _injected_pin_indices[i];
2782 ShenandoahHeapRegion* r = get_region(idx);
2783 assert(r->pin_count() > 0, "Region %zu in tracker must contain a pin.", idx);
2784 r->record_unpin();
2785 }
2786 _injected_pin_count = 0;
2787 }
2788
2789 void ShenandoahHeap::initialize_serviceability() {
2790 _memory_pool = new ShenandoahMemoryPool(this);
2791 _cycle_memory_manager.add_pool(_memory_pool);
2792 _stw_memory_manager.add_pool(_memory_pool);
2793 }
2794
2795 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2796 GrowableArray<GCMemoryManager*> memory_managers(2);
2797 memory_managers.append(&_cycle_memory_manager);
2798 memory_managers.append(&_stw_memory_manager);
2799 return memory_managers;
2800 }
2801
2802 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2803 GrowableArray<MemoryPool*> memory_pools(1);
2804 memory_pools.append(_memory_pool);
2805 return memory_pools;
2806 }
2807
2808 MemoryUsage ShenandoahHeap::memory_usage() {
2809 return shenandoah_memory_usage(_initial_size, used(), committed(), max_capacity());
2810 }
2811
2812 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2813 _heap(ShenandoahHeap::heap()),
2814 _index(0) {}
2815
2816 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2817 _heap(heap),
2818 _index(0) {}
2819
2820 void ShenandoahRegionIterator::reset() {
2821 _index.store_relaxed(0);
2822 }
2823
2824 bool ShenandoahRegionIterator::has_next() const {
2825 return _index.load_relaxed() < _heap->num_regions();
2826 }
2827
2828 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2829 #ifdef ASSERT
2830 assert(_liveness_cache != nullptr, "sanity");
2831 assert(worker_id < _max_workers, "sanity");
2832 for (uint i = 0; i < num_regions(); i++) {
2833 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2834 }
2835 #endif
2836 return _liveness_cache[worker_id];
2837 }
2838
2839 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2840 assert(worker_id < _max_workers, "sanity");
2841 assert(_liveness_cache != nullptr, "sanity");
2842 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2843 for (uint i = 0; i < num_regions(); i++) {
2844 ShenandoahLiveData live = ld[i];
2845 if (live > 0) {
2846 ShenandoahHeapRegion* r = get_region(i);
2847 r->increase_live_data_gc_words(live);
2848 ld[i] = 0;
2849 }
2850 }
2851 }
2852
2853 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2854 if (is_idle()) return false;
2855
2856 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2857 // marking phase.
2858 if (is_concurrent_mark_in_progress() &&
2859 !marking_context()->allocated_after_mark_start(obj)) {
2860 return true;
2861 }
2862
2863 // Can not guarantee obj is deeply good.
2864 if (has_forwarded_objects()) {
2865 return true;
2866 }
2867
2868 return false;
2869 }
2870
2871 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2872 #if INCLUDE_CDS_JAVA_HEAP
2873 // CDS wants a raw continuous memory range to load a bunch of objects itself.
2874 // This is an unusual request, since all requested regions should be regular, not humongous.
2875 //
2876 // CDS would guarantee no objects straddle multiple regions, as long as regions are as large
2877 // as MIN_GC_REGION_ALIGNMENT.
2878 guarantee(ShenandoahHeapRegion::region_size_bytes() >= AOTMappedHeapWriter::MIN_GC_REGION_ALIGNMENT, "Must be");
2879
2880 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_cds(size);
2881 return allocate_memory(req);
2882 #else
2883 assert(false, "Archive heap loader should not be available, should not be here");
2884 return nullptr;
2885 #endif // INCLUDE_CDS_JAVA_HEAP
2886 }
2887
2888 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2889 // Nothing to do here, except checking that heap looks fine.
2890 #ifdef ASSERT
2891 HeapWord* start = archive_space.start();
2892 HeapWord* end = archive_space.end();
2893
2894 // No unclaimed space between the objects.
2895 // Objects are properly allocated in correct regions.
2896 HeapWord* cur = start;
2897 while (cur < end) {
2898 oop oop = cast_to_oop(cur);
2899 shenandoah_assert_in_correct_region(nullptr, oop);
2900 cur += oop->size();
2901 }
2902
2903 // No unclaimed tail at the end of archive space.
2904 assert(cur == end,
2905 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2906 p2i(cur), p2i(end));
2907
2908 // All regions in contiguous space have good state.
2909 size_t begin_reg_idx = heap_region_index_containing(start);
2910 size_t end_reg_idx = heap_region_index_containing(end);
2911
2912 for (size_t idx = begin_reg_idx; idx <= end_reg_idx; idx++) {
2913 ShenandoahHeapRegion* r = get_region(idx);
2914 assert(r->is_regular(), "Must be regular");
2915 assert(r->is_young(), "Must be young");
2916 assert(idx == end_reg_idx || r->top() == r->end(),
2917 "All regions except the last one should be full: " PTR_FORMAT " " PTR_FORMAT,
2918 p2i(r->top()), p2i(r->end()));
2919 assert(idx != begin_reg_idx || r->bottom() == start,
2920 "Archive space start should be at the bottom of first region: " PTR_FORMAT " " PTR_FORMAT,
2921 p2i(r->bottom()), p2i(start));
2922 assert(idx != end_reg_idx || r->top() == end,
2923 "Archive space end should be at the top of last region: " PTR_FORMAT " " PTR_FORMAT,
2924 p2i(r->top()), p2i(end));
2925 }
2926
2927 #endif
2928 }
2929
2930 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2931 if (!mode()->is_generational()) {
2932 return global_generation();
2933 } else if (affiliation == YOUNG_GENERATION) {
2934 return young_generation();
2935 } else if (affiliation == OLD_GENERATION) {
2936 return old_generation();
2937 }
2938
2939 ShouldNotReachHere();
2940 return nullptr;
2941 }
2942
2943 void ShenandoahHeap::log_heap_status(const char* msg) const {
2944 if (mode()->is_generational()) {
2945 young_generation()->log_status(msg);
2946 old_generation()->log_status(msg);
2947 } else {
2948 global_generation()->log_status(msg);
2949 }
2950 }
2951
2952 ShenandoahHeapLocker::ShenandoahHeapLocker(ShenandoahHeapLock* lock, bool allow_block_for_safepoint) : _lock(lock) {
2953 #ifdef ASSERT
2954 ShenandoahFreeSet* free_set = ShenandoahHeap::heap()->free_set();
2955 // free_set is nullptr only at pre-initialized state
2956 assert(free_set == nullptr || !free_set->rebuild_lock()->owned_by_self(), "Dead lock, can't acquire heap lock while holding free-set rebuild lock");
2957 assert(_lock != nullptr, "Must not");
2958 #endif
2959 _lock->lock(allow_block_for_safepoint);
2960 }