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/shenandoahStackWatermark.hpp"
77 #include "gc/shenandoah/shenandoahSTWMark.hpp"
78 #include "gc/shenandoah/shenandoahUncommitThread.hpp"
79 #include "gc/shenandoah/shenandoahUtils.hpp"
80 #include "gc/shenandoah/shenandoahVerifier.hpp"
81 #include "gc/shenandoah/shenandoahVMOperations.hpp"
82 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
83 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
84 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
85 #include "memory/allocation.hpp"
86 #include "memory/classLoaderMetaspace.hpp"
87 #include "memory/memoryReserver.hpp"
88 #include "memory/metaspaceUtils.hpp"
89 #include "memory/universe.hpp"
90 #include "nmt/mallocTracker.hpp"
91 #include "nmt/memTracker.hpp"
92 #include "oops/compressedOops.inline.hpp"
93 #include "prims/jvmtiTagMap.hpp"
94 #include "runtime/atomic.hpp"
95 #include "runtime/atomicAccess.hpp"
96 #include "runtime/globals.hpp"
97 #include "runtime/interfaceSupport.inline.hpp"
98 #include "runtime/java.hpp"
99 #include "runtime/orderAccess.hpp"
100 #include "runtime/safepointMechanism.hpp"
101 #include "runtime/stackWatermarkSet.hpp"
102 #include "runtime/threads.hpp"
103 #include "runtime/vmThread.hpp"
104 #include "utilities/events.hpp"
105 #include "utilities/globalDefinitions.hpp"
106 #include "utilities/powerOfTwo.hpp"
107 #if INCLUDE_JFR
108 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
109 #endif
110
111 class ShenandoahPretouchHeapTask : public WorkerTask {
112 private:
113 ShenandoahRegionIterator _regions;
114 const size_t _page_size;
115 public:
116 ShenandoahPretouchHeapTask(size_t page_size) :
117 WorkerTask("Shenandoah Pretouch Heap"),
118 _page_size(page_size) {}
119
120 virtual void work(uint worker_id) {
121 ShenandoahHeapRegion* r = _regions.next();
122 while (r != nullptr) {
123 if (r->is_committed()) {
124 os::pretouch_memory(r->bottom(), r->end(), _page_size);
125 }
126 r = _regions.next();
127 }
128 }
129 };
130
131 class ShenandoahPretouchBitmapTask : public WorkerTask {
132 private:
133 ShenandoahRegionIterator _regions;
134 char* _bitmap_base;
135 const size_t _bitmap_size;
136 const size_t _page_size;
137 public:
138 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
139 WorkerTask("Shenandoah Pretouch Bitmap"),
140 _bitmap_base(bitmap_base),
141 _bitmap_size(bitmap_size),
142 _page_size(page_size) {}
143
144 virtual void work(uint worker_id) {
145 ShenandoahHeapRegion* r = _regions.next();
146 while (r != nullptr) {
147 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
148 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
149 assert (end <= _bitmap_size, "end is sane: %zu < %zu", end, _bitmap_size);
150
151 if (r->is_committed()) {
152 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
153 }
154
155 r = _regions.next();
156 }
157 }
158 };
159
160 static ReservedSpace reserve(size_t size, size_t preferred_page_size) {
161 // When a page size is given we don't want to mix large
162 // and normal pages. If the size is not a multiple of the
163 // page size it will be aligned up to achieve this.
164 size_t alignment = os::vm_allocation_granularity();
165 if (preferred_page_size != os::vm_page_size()) {
166 alignment = MAX2(preferred_page_size, alignment);
167 size = align_up(size, alignment);
168 }
169
170 const ReservedSpace reserved = MemoryReserver::reserve(size, alignment, preferred_page_size, mtGC);
171 if (!reserved.is_reserved()) {
172 vm_exit_during_initialization("Could not reserve space");
173 }
174 return reserved;
175 }
176
177 jint ShenandoahHeap::initialize() {
178 //
179 // Figure out heap sizing
180 //
181
182 size_t init_byte_size = InitialHeapSize;
183 size_t min_byte_size = MinHeapSize;
184 size_t max_byte_size = MaxHeapSize;
185 size_t heap_alignment = HeapAlignment;
186
187 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
188
189 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
190 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
191
192 _num_regions = ShenandoahHeapRegion::region_count();
193 assert(_num_regions == (max_byte_size / reg_size_bytes),
194 "Regions should cover entire heap exactly: %zu != %zu/%zu",
195 _num_regions, max_byte_size, reg_size_bytes);
196
197 size_t num_committed_regions = init_byte_size / reg_size_bytes;
198 num_committed_regions = MIN2(num_committed_regions, _num_regions);
199 assert(num_committed_regions <= _num_regions, "sanity");
200 _initial_size = num_committed_regions * reg_size_bytes;
201
202 size_t num_min_regions = min_byte_size / reg_size_bytes;
203 num_min_regions = MIN2(num_min_regions, _num_regions);
204 assert(num_min_regions <= _num_regions, "sanity");
205 _minimum_size = num_min_regions * reg_size_bytes;
206
207 _soft_max_size.store_relaxed(clamp(SoftMaxHeapSize, min_capacity(), max_capacity()));
208
209 _committed.store_relaxed(_initial_size);
210
211 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
212 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
213 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
214
215 //
216 // Reserve and commit memory for heap
217 //
218
219 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
220 initialize_reserved_region(heap_rs);
221 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
222 _heap_region_special = heap_rs.special();
223
224 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
225 "Misaligned heap: " PTR_FORMAT, p2i(base()));
226 os::trace_page_sizes_for_requested_size("Heap",
227 max_byte_size, heap_alignment,
228 heap_rs.base(),
229 heap_rs.size(), heap_rs.page_size());
230
231 #if SHENANDOAH_OPTIMIZED_MARKTASK
232 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
233 // Fail if we ever attempt to address more than we can.
234 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
235 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
236 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
237 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
238 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
239 vm_exit_during_initialization("Fatal Error", buf);
240 }
241 #endif
242
243 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
244 if (!_heap_region_special) {
245 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
246 "Cannot commit heap memory");
247 }
248
249 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
250
251 // Now we know the number of regions and heap sizes, initialize the heuristics.
252 initialize_heuristics();
253
254 // If ShenandoahCardBarrier is enabled but it's not generational mode
255 // it means we're under passive mode and we have to initialize old gen
256 // for the purpose of having card table.
257 if (ShenandoahCardBarrier && !(mode()->is_generational())) {
258 _old_generation = new ShenandoahOldGeneration(max_workers());
259 }
260
261 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
262
263 //
264 // Worker threads must be initialized after the barrier is configured
265 //
266 _workers = new ShenandoahWorkerThreads("ShenWorker", _max_workers);
267 if (_workers == nullptr) {
268 vm_exit_during_initialization("Failed necessary allocation.");
269 } else {
270 _workers->initialize_workers();
271 }
272
273 if (ParallelGCThreads > 1) {
274 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
275 _safepoint_workers->initialize_workers();
276 }
277
278 //
279 // Reserve and commit memory for bitmap(s)
280 //
281
282 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
283 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
284
285 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
286
287 guarantee(bitmap_bytes_per_region != 0,
288 "Bitmap bytes per region should not be zero");
289 guarantee(is_power_of_2(bitmap_bytes_per_region),
290 "Bitmap bytes per region should be power of two: %zu", bitmap_bytes_per_region);
291
292 if (bitmap_page_size > bitmap_bytes_per_region) {
293 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
294 _bitmap_bytes_per_slice = bitmap_page_size;
295 } else {
296 _bitmap_regions_per_slice = 1;
297 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
298 }
299
300 guarantee(_bitmap_regions_per_slice >= 1,
301 "Should have at least one region per slice: %zu",
302 _bitmap_regions_per_slice);
303
304 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
305 "Bitmap slices should be page-granular: bps = %zu, page size = %zu",
306 _bitmap_bytes_per_slice, bitmap_page_size);
307
308 ReservedSpace bitmap = reserve(_bitmap_size, bitmap_page_size);
309 os::trace_page_sizes_for_requested_size("Mark Bitmap",
310 bitmap_size_orig, bitmap_page_size,
311 bitmap.base(),
312 bitmap.size(), bitmap.page_size());
313 MemTracker::record_virtual_memory_tag(bitmap, mtGC);
314 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
315 _bitmap_region_special = bitmap.special();
316
317 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
318 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
319 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
320 if (!_bitmap_region_special) {
321 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
322 "Cannot commit bitmap memory");
323 }
324
325 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
326
327 if (ShenandoahVerify) {
328 ReservedSpace verify_bitmap = reserve(_bitmap_size, bitmap_page_size);
329 os::trace_page_sizes_for_requested_size("Verify Bitmap",
330 bitmap_size_orig, bitmap_page_size,
331 verify_bitmap.base(),
332 verify_bitmap.size(), verify_bitmap.page_size());
333 if (!verify_bitmap.special()) {
334 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
335 "Cannot commit verification bitmap memory");
336 }
337 MemTracker::record_virtual_memory_tag(verify_bitmap, mtGC);
338 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
339 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
340 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
341 }
342
343 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
344 size_t aux_bitmap_page_size = bitmap_page_size;
345
346 ReservedSpace aux_bitmap = reserve(_bitmap_size, aux_bitmap_page_size);
347 os::trace_page_sizes_for_requested_size("Aux Bitmap",
348 bitmap_size_orig, aux_bitmap_page_size,
349 aux_bitmap.base(),
350 aux_bitmap.size(), aux_bitmap.page_size());
351 MemTracker::record_virtual_memory_tag(aux_bitmap, mtGC);
352 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
353 _aux_bitmap_region_special = aux_bitmap.special();
354 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
355
356 //
357 // Create regions and region sets
358 //
359 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
360 size_t region_storage_size_orig = region_align * _num_regions;
361 size_t region_storage_size = align_up(region_storage_size_orig,
362 MAX2(region_page_size, os::vm_allocation_granularity()));
363
364 ReservedSpace region_storage = reserve(region_storage_size, region_page_size);
365 os::trace_page_sizes_for_requested_size("Region Storage",
366 region_storage_size_orig, region_page_size,
367 region_storage.base(),
368 region_storage.size(), region_storage.page_size());
369 MemTracker::record_virtual_memory_tag(region_storage, mtGC);
370 if (!region_storage.special()) {
371 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
372 "Cannot commit region memory");
373 }
374
375 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
376 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
377 // If not successful, bite a bullet and allocate at whatever address.
378 {
379 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
380 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
381 const size_t cset_page_size = os::vm_page_size();
382
383 uintptr_t min = round_up_power_of_2(cset_align);
384 uintptr_t max = (1u << 30u);
385 ReservedSpace cset_rs;
386
387 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
388 char* req_addr = (char*)addr;
389 assert(is_aligned(req_addr, cset_align), "Should be aligned");
390 cset_rs = MemoryReserver::reserve(req_addr, cset_size, cset_align, cset_page_size, mtGC);
391 if (cset_rs.is_reserved()) {
392 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
393 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
394 break;
395 }
396 }
397
398 if (_collection_set == nullptr) {
399 cset_rs = MemoryReserver::reserve(cset_size, cset_align, os::vm_page_size(), mtGC);
400 if (!cset_rs.is_reserved()) {
401 vm_exit_during_initialization("Cannot reserve memory for collection set");
402 }
403
404 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
405 }
406 os::trace_page_sizes_for_requested_size("Collection Set",
407 cset_size, cset_page_size,
408 cset_rs.base(),
409 cset_rs.size(), cset_rs.page_size());
410 }
411
412 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
413 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
414
415 {
416 ShenandoahHeapLocker locker(lock());
417 for (size_t i = 0; i < _num_regions; i++) {
418 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
419 bool is_committed = i < num_committed_regions;
420 void* loc = region_storage.base() + i * region_align;
421
422 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
423 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
424
425 _marking_context->initialize_top_at_mark_start(r);
426 _regions[i] = r;
427 assert(!collection_set()->is_in(i), "New region should not be in collection set");
428
429 _affiliations[i] = ShenandoahAffiliation::FREE;
430 }
431
432 if (mode()->is_generational()) {
433 size_t young_reserve = (soft_max_capacity() * ShenandoahEvacReserve) / 100;
434 young_generation()->set_evacuation_reserve(young_reserve);
435 old_generation()->set_evacuation_reserve((size_t) 0);
436 old_generation()->set_promoted_reserve((size_t) 0);
437 }
438
439 _free_set = new ShenandoahFreeSet(this, _num_regions);
440 _allocator = new ShenandoahAllocator(_free_set);
441 initialize_generations();
442
443 // We are initializing free set. We ignore cset region tallies.
444 size_t young_trashed_regions, old_trashed_regions, first_old, last_old, num_old;
445 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old, last_old, num_old);
446 if (mode()->is_generational()) {
447 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
448 // We cannot call
449 // gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions)
450 // until after the heap is fully initialized. So we make up a safe value here.
451 size_t allocation_runway = InitialHeapSize / 2;
452 gen_heap->compute_old_generation_balance(allocation_runway, old_trashed_regions, young_trashed_regions);
453 }
454 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, num_old);
455 }
456
457 if (AlwaysPreTouch) {
458 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
459 // before initialize() below zeroes it with initializing thread. For any given region,
460 // we touch the region and the corresponding bitmaps from the same thread.
461 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
462
463 _pretouch_heap_page_size = heap_page_size;
464 _pretouch_bitmap_page_size = bitmap_page_size;
465
466 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
467 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
468
469 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
470 _workers->run_task(&bcl);
471
472 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
473 _workers->run_task(&hcl);
474 }
475
476 //
477 // Initialize the rest of GC subsystems
478 //
479
480 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
481 for (uint worker = 0; worker < _max_workers; worker++) {
482 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
483 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
484 }
485
486 // There should probably be Shenandoah-specific options for these,
487 // just as there are G1-specific options.
488 {
489 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
490 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
491 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
492 }
493
494 _monitoring_support = new ShenandoahMonitoringSupport(this);
495 _phase_timings = new ShenandoahPhaseTimings(max_workers());
496 ShenandoahCodeRoots::initialize();
497
498 // Initialization of controller makes use of variables established by initialize_heuristics.
499 initialize_controller();
500
501 // Certain initialization of heuristics must be deferred until after controller is initialized.
502 post_initialize_heuristics();
503 start_idle_span();
504 if (ShenandoahUncommit) {
505 _uncommit_thread = new ShenandoahUncommitThread(this);
506 }
507 print_init_logger();
508 FullGCForwarding::initialize(_heap_region);
509 return JNI_OK;
510 }
511
512 void ShenandoahHeap::initialize_controller() {
513 _control_thread = new ShenandoahControlThread();
514 }
515
516 void ShenandoahHeap::print_init_logger() const {
517 ShenandoahInitLogger::print();
518 }
519
520 void ShenandoahHeap::initialize_mode() {
521 if (ShenandoahGCMode != nullptr) {
522 if (strcmp(ShenandoahGCMode, "satb") == 0) {
523 _gc_mode = new ShenandoahSATBMode();
524 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
525 _gc_mode = new ShenandoahPassiveMode();
526 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
527 _gc_mode = new ShenandoahGenerationalMode();
528 } else {
529 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
530 }
531 } else {
532 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
533 }
534 _gc_mode->initialize_flags();
535 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
536 vm_exit_during_initialization(
537 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
538 _gc_mode->name()));
539 }
540 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
541 vm_exit_during_initialization(
542 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
543 _gc_mode->name()));
544 }
545 }
546
547 void ShenandoahHeap::initialize_heuristics() {
548 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers());
549 _global_generation->initialize_heuristics(mode());
550 }
551
552 #ifdef _MSC_VER
553 #pragma warning( push )
554 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
555 #endif
556
557 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
558 CollectedHeap(),
559 _active_generation(nullptr),
560 _initial_size(0),
561 _committed(0),
562 _alloc_rate_decay(&_alloc_rate),
563 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
564 _workers(nullptr),
565 _safepoint_workers(nullptr),
566 _heap_region_special(false),
567 _num_regions(0),
568 _regions(nullptr),
569 _affiliations(nullptr),
570 _gc_state_changed(false),
571 _gc_no_progress_count(0),
572 _cancel_requested_time(0),
573 _update_refs_iterator(this),
574 _global_generation(nullptr),
575 _control_thread(nullptr),
576 _uncommit_thread(nullptr),
577 _young_generation(nullptr),
578 _old_generation(nullptr),
579 _shenandoah_policy(policy),
580 _gc_mode(nullptr),
581 _free_set(nullptr),
582 _allocator(nullptr),
583 _verifier(nullptr),
584 _phase_timings(nullptr),
585 _monitoring_support(nullptr),
586 _memory_pool(nullptr),
587 _stw_memory_manager("Shenandoah Pauses"),
588 _cycle_memory_manager("Shenandoah Cycles"),
589 _gc_timer(new ConcurrentGCTimer()),
590 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
591 _marking_context(nullptr),
592 _bitmap_size(0),
593 _bitmap_regions_per_slice(0),
594 _bitmap_bytes_per_slice(0),
595 _bitmap_region_special(false),
596 _aux_bitmap_region_special(false),
597 _liveness_cache(nullptr),
598 _collection_set(nullptr),
599 _evac_tracker(new ShenandoahEvacuationTracker()),
600 _injected_pin_count(0)
601 {
602 // Initialize GC mode early, many subsequent initialization procedures depend on it
603 initialize_mode();
604 _cancelled_gc.set(GCCause::_no_gc);
605 }
606
607 #ifdef _MSC_VER
608 #pragma warning( pop )
609 #endif
610
611 void ShenandoahHeap::print_heap_on(outputStream* st) const {
612 const bool is_generational = mode()->is_generational();
613 const char* front_spacing = "";
614 if (is_generational) {
615 st->print_cr("Generational Shenandoah Heap");
616 st->print_cr(" Young:");
617 st->print_cr(" " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(young_generation()->max_capacity()), PROPERFMTARGS(young_generation()->used()));
618 st->print_cr(" Old:");
619 st->print_cr(" " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(old_generation()->max_capacity()), PROPERFMTARGS(old_generation()->used()));
620 st->print_cr(" Entire heap:");
621 st->print_cr(" " PROPERFMT " soft max, " PROPERFMT " committed",
622 PROPERFMTARGS(soft_max_capacity()), PROPERFMTARGS(committed()));
623 front_spacing = " ";
624 } else {
625 st->print_cr("Shenandoah Heap");
626 st->print_cr(" " PROPERFMT " max, " PROPERFMT " soft max, " PROPERFMT " committed, " PROPERFMT " used",
627 PROPERFMTARGS(max_capacity()),
628 PROPERFMTARGS(soft_max_capacity()),
629 PROPERFMTARGS(committed()),
630 PROPERFMTARGS(used())
631 );
632 }
633 st->print_cr("%s %zu x " PROPERFMT " regions",
634 front_spacing,
635 num_regions(),
636 PROPERFMTARGS(ShenandoahHeapRegion::region_size_bytes()));
637
638 st->print("Status: ");
639 if (has_forwarded_objects()) st->print("has forwarded objects, ");
640 if (!is_generational) {
641 if (is_concurrent_mark_in_progress()) st->print("marking,");
642 } else {
643 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
644 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
645 }
646 if (is_evacuation_in_progress()) st->print("evacuating, ");
647 if (is_update_refs_in_progress()) st->print("updating refs, ");
648 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
649 if (is_full_gc_in_progress()) st->print("full gc, ");
650 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
651 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
652 if (is_concurrent_strong_root_in_progress() &&
653 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
654
655 if (cancelled_gc()) {
656 st->print("cancelled");
657 } else {
658 st->print("not cancelled");
659 }
660 st->cr();
661
662 st->print_cr("Reserved region:");
663 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
664 p2i(reserved_region().start()),
665 p2i(reserved_region().end()));
666
667 ShenandoahCollectionSet* cset = collection_set();
668 st->print_cr("Collection set:");
669 if (cset != nullptr) {
670 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
671 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
672 } else {
673 st->print_cr(" (null)");
674 }
675
676 st->cr();
677
678 if (Verbose) {
679 st->cr();
680 print_heap_regions_on(st);
681 }
682 }
683
684 void ShenandoahHeap::print_gc_on(outputStream* st) const {
685 print_heap_regions_on(st);
686 }
687
688 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
689 public:
690 void do_thread(Thread* thread) {
691 assert(thread != nullptr, "Sanity");
692 ShenandoahThreadLocalData::initialize_gclab(thread);
693 }
694 };
695
696 void ShenandoahHeap::initialize_generations() {
697 _global_generation->post_initialize(this);
698 }
699
700 // We do not call this explicitly It is called by Hotspot infrastructure.
701 void ShenandoahHeap::post_initialize() {
702 CollectedHeap::post_initialize();
703
704 check_soft_max_changed();
705
706 // Schedule periodic task to report on gc thread CPU utilization
707 _mmu_tracker.initialize();
708
709 // Periodically decay allocation rate to compensate for not being updated when allocation rate
710 // is low. Heuristics are evaluated unconditionally from a dedicated thread so it will continue
711 // to see the last (possibly stale) allocation rate if the allocation rate is low.
712 _alloc_rate_decay.enroll();
713
714 MutexLocker ml(Threads_lock);
715
716 ShenandoahInitWorkerGCLABClosure init_gclabs;
717 _workers->threads_do(&init_gclabs);
718
719 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
720 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
721 _workers->set_initialize_gclab();
722
723 // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump
724 // during a concurrent evacuation phase.
725 if (_safepoint_workers != nullptr) {
726 _safepoint_workers->threads_do(&init_gclabs);
727 _safepoint_workers->set_initialize_gclab();
728 }
729
730 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
731 }
732
733 void ShenandoahHeap::post_initialize_heuristics() {
734 _global_generation->post_initialize_heuristics();
735 }
736
737 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
738 return _global_generation->heuristics();
739 }
740
741 size_t ShenandoahHeap::used() const {
742 return global_generation()->used();
743 }
744
745 size_t ShenandoahHeap::committed() const {
746 return _committed.load_relaxed();
747 }
748
749 void ShenandoahHeap::increase_committed(size_t bytes) {
750 shenandoah_assert_heaplocked_or_safepoint();
751 _committed.fetch_then_add(bytes, memory_order_relaxed);
752 }
753
754 void ShenandoahHeap::decrease_committed(size_t bytes) {
755 shenandoah_assert_heaplocked_or_safepoint();
756 _committed.fetch_then_sub(bytes, memory_order_relaxed);
757 }
758
759 size_t ShenandoahHeap::capacity() const {
760 return committed();
761 }
762
763 size_t ShenandoahHeap::max_capacity() const {
764 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
765 }
766
767 size_t ShenandoahHeap::soft_max_capacity() const {
768 size_t v = _soft_max_size.load_relaxed();
769 assert(min_capacity() <= v && v <= max_capacity(),
770 "Should be in bounds: %zu <= %zu <= %zu",
771 min_capacity(), v, max_capacity());
772 return v;
773 }
774
775 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
776 assert(min_capacity() <= v && v <= max_capacity(),
777 "Should be in bounds: %zu <= %zu <= %zu",
778 min_capacity(), v, max_capacity());
779 _soft_max_size.store_relaxed(v);
780 heuristics()->compute_headroom_adjustment();
781 }
782
783 size_t ShenandoahHeap::min_capacity() const {
784 return _minimum_size;
785 }
786
787 size_t ShenandoahHeap::initial_capacity() const {
788 return _initial_size;
789 }
790
791 bool ShenandoahHeap::is_in(const void* p) const {
792 if (!is_in_reserved(p)) {
793 return false;
794 }
795
796 if (is_full_gc_move_in_progress()) {
797 // Full GC move is running, we do not have a consistent region
798 // information yet. But we know the pointer is in heap.
799 return true;
800 }
801
802 // Now check if we point to a live section in active region.
803 const ShenandoahHeapRegion* r = heap_region_containing(p);
804 if (p >= r->top()) {
805 return false;
806 }
807
808 if (r->is_active()) {
809 return true;
810 }
811
812 // The region is trash, but won't be recycled until after concurrent weak
813 // roots. We also don't allow mutators to allocate from trash regions
814 // during weak roots. Concurrent class unloading may access unmarked oops
815 // in trash regions.
816 return r->is_trash() && is_concurrent_weak_root_in_progress();
817 }
818
819 void ShenandoahHeap::notify_soft_max_changed() {
820 if (_uncommit_thread != nullptr) {
821 _uncommit_thread->notify_soft_max_changed();
822 }
823 }
824
825 void ShenandoahHeap::notify_explicit_gc_requested() {
826 if (_uncommit_thread != nullptr) {
827 _uncommit_thread->notify_explicit_gc_requested();
828 }
829 }
830
831 bool ShenandoahHeap::check_soft_max_changed() {
832 size_t new_soft_max = AtomicAccess::load(&SoftMaxHeapSize);
833 size_t old_soft_max = soft_max_capacity();
834 if (new_soft_max != old_soft_max) {
835 new_soft_max = clamp(new_soft_max, min_capacity(), max_capacity());
836 if (new_soft_max != old_soft_max) {
837 log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s",
838 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
839 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
840 );
841 set_soft_max_capacity(new_soft_max);
842 return true;
843 }
844 }
845 return false;
846 }
847
848 void ShenandoahHeap::notify_heap_changed() {
849 // Update monitoring counters when we took a new region. This amortizes the
850 // update costs on slow path.
851 monitoring_support()->notify_heap_changed();
852 _heap_changed.try_set();
853 }
854
855 void ShenandoahHeap::start_idle_span() {
856 heuristics()->start_idle_span();
857 }
858
859 void ShenandoahHeap::set_forced_counters_update(bool value) {
860 monitoring_support()->set_forced_counters_update(value);
861 }
862
863 void ShenandoahHeap::handle_force_counters_update() {
864 monitoring_support()->handle_force_counters_update();
865 }
866
867 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
868 // New object should fit the GCLAB size
869 size_t min_size = MAX2(size, PLAB::min_size());
870
871 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
872 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
873
874 new_size = MIN2(new_size, PLAB::max_size());
875 new_size = MAX2(new_size, PLAB::min_size());
876
877 // Record new heuristic value even if we take any shortcut. This captures
878 // the case when moderately-sized objects always take a shortcut. At some point,
879 // heuristics should catch up with them.
880 log_debug(gc, free)("Set new GCLAB size: %zu", new_size);
881 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
882
883 if (new_size < size) {
884 // New size still does not fit the object. Fall back to shared allocation.
885 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
886 log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size);
887 return nullptr;
888 }
889
890 // Retire current GCLAB, and allocate a new one.
891 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
892 gclab->retire();
893
894 size_t actual_size = 0;
895 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
896 if (gclab_buf == nullptr) {
897 return nullptr;
898 }
899
900 assert (size <= actual_size, "allocation should fit");
901
902 // ...and clear or zap just allocated TLAB, if needed.
903 if (ZeroTLAB) {
904 Copy::zero_to_words(gclab_buf, actual_size);
905 } else if (ZapTLAB) {
906 // Skip mangling the space corresponding to the object header to
907 // ensure that the returned space is not considered parsable by
908 // any concurrent GC thread.
909 size_t hdr_size = oopDesc::header_size();
910 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
911 }
912 gclab->set_buf(gclab_buf, actual_size);
913 return gclab->allocate(size);
914 }
915
916 // Called from stubs in JIT code or interpreter
917 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
918 size_t requested_size,
919 size_t* actual_size) {
920 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
921 HeapWord* res = allocate_memory(req);
922 if (res != nullptr) {
923 *actual_size = req.actual_size();
924 } else {
925 *actual_size = 0;
926 }
927 return res;
928 }
929
930 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
931 size_t word_size,
932 size_t* actual_size) {
933 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
934 HeapWord* res = allocate_memory(req);
935 if (res != nullptr) {
936 *actual_size = req.actual_size();
937 } else {
938 *actual_size = 0;
939 }
940 return res;
941 }
942
943 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
944 bool in_new_region = false;
945 HeapWord* result = nullptr;
946
947 if (req.is_mutator_alloc()) {
948
949 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
950 result = allocate_memory_work(req, in_new_region);
951 }
952
953 // Check that gc overhead is not exceeded.
954 //
955 // Shenandoah will grind along for quite a while allocating one
956 // object at a time using shared (non-tlab) allocations. This check
957 // is testing that the GC overhead limit has not been exceeded.
958 // This will notify the collector to start a cycle, but will raise
959 // an OOME to the mutator if the last Full GCs have not made progress.
960 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
961 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
962 control_thread()->handle_alloc_failure(req, false);
963 req.set_actual_size(0);
964 return nullptr;
965 }
966
967 if (result == nullptr) {
968 // Block until control thread reacted, then retry allocation.
969 //
970 // It might happen that one of the threads requesting allocation would unblock
971 // way later after GC happened, only to fail the second allocation, because
972 // other threads have already depleted the free storage. In this case, a better
973 // strategy is to try again, until at least one full GC has completed.
974 //
975 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
976 // a) We experienced a GC that had good progress, or
977 // b) We experienced at least one Full GC (whether or not it had good progress)
978
979 const size_t original_count = shenandoah_policy()->full_gc_count();
980 while (result == nullptr && should_retry_allocation(original_count)) {
981 control_thread()->handle_alloc_failure(req, true);
982 result = allocate_memory_work(req, in_new_region);
983 }
984 if (result != nullptr) {
985 // If our allocation request has been satisfied after it initially failed, we count this as good gc progress
986 notify_gc_progress();
987 }
988 if (log_develop_is_enabled(Debug, gc, alloc)) {
989 ResourceMark rm;
990 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu"
991 ", Original: %zu, Latest: %zu",
992 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
993 original_count, get_gc_no_progress_count());
994 }
995 }
996 } else {
997 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
998 result = allocate_memory_work(req, in_new_region);
999 // Do not call handle_alloc_failure() here, because we cannot block.
1000 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1001 }
1002
1003 if (in_new_region) {
1004 notify_heap_changed();
1005 }
1006
1007 if (result == nullptr) {
1008 req.set_actual_size(0);
1009 }
1010
1011 if (result != nullptr) {
1012 size_t requested = req.size();
1013 size_t actual = req.actual_size();
1014
1015 assert (req.is_lab_alloc() || (requested == actual),
1016 "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu",
1017 req.type_string(), requested, actual);
1018 }
1019
1020 return result;
1021 }
1022
1023 inline bool ShenandoahHeap::should_retry_allocation(size_t original_full_gc_count) const {
1024 return shenandoah_policy()->full_gc_count() == original_full_gc_count
1025 && !shenandoah_policy()->is_at_shutdown();
1026 }
1027
1028 HeapWord* ShenandoahHeap::allocate_memory_work(ShenandoahAllocRequest& req, bool& in_new_region) {
1029 // Reserve the promotion budget up front so it is enforced atomically without the heap lock.
1030 // If the reserve is exhausted, deny the promotion rather than overshoot it; the reservation
1031 // is refunded below if the allocation itself fails.
1032 if (req.is_promotion() && !old_generation()->try_expend_promoted(req.size() << LogHeapWordSize)) {
1033 return nullptr;
1034 }
1035
1036 HeapWord* result = _allocator->allocate(req, in_new_region);
1037
1038 if (result != nullptr) {
1039 if (req.is_mutator_alloc()) {
1040 _alloc_rate.allocated((req.actual_size() + req.waste()) * HeapWordSize);
1041 }
1042
1043 if (req.is_old()) {
1044 if (req.is_lab_alloc()) {
1045 old_generation()->configure_plab_for_current_thread(req);
1046 } else if (req.is_promotion()) {
1047 log_debug(gc, plab)("Expend shared promotion of %zu bytes", req.actual_size() * HeapWordSize);
1048 }
1049 }
1050 } else if (req.is_promotion()) {
1051 // Allocation failed, so refund the promotion budget reserved above.
1052 old_generation()->unexpend_promoted(req.size() << LogHeapWordSize);
1053 }
1054 return result;
1055 }
1056
1057 HeapWord* ShenandoahHeap::mem_allocate(size_t size) {
1058 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1059 return allocate_memory(req);
1060 }
1061
1062 oop ShenandoahHeap::array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS) {
1063 ShenandoahObjArrayAllocator allocator(klass, size, length, do_zero, THREAD);
1064 return allocator.allocate();
1065 }
1066
1067 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1068 size_t size,
1069 Metaspace::MetadataType mdtype) {
1070 MetaWord* result;
1071
1072 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1073 ShenandoahHeuristics* h = global_generation()->heuristics();
1074 if (h->can_unload_classes()) {
1075 h->record_metaspace_oom();
1076 }
1077
1078 // Expand and retry allocation
1079 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1080 if (result != nullptr) {
1081 return result;
1082 }
1083
1084 // Start full GC
1085 collect(GCCause::_metadata_GC_clear_soft_refs);
1086
1087 // Retry allocation
1088 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1089 if (result != nullptr) {
1090 return result;
1091 }
1092
1093 // Expand and retry allocation
1094 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1095 if (result != nullptr) {
1096 return result;
1097 }
1098
1099 // Out of memory
1100 return nullptr;
1101 }
1102
1103 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1104 private:
1105 ShenandoahHeap* const _heap;
1106 Thread* const _thread;
1107 public:
1108 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1109 _heap(heap), _thread(Thread::current()) {}
1110
1111 void do_object(oop p) {
1112 shenandoah_assert_marked(nullptr, p);
1113 if (!p->is_forwarded()) {
1114 _heap->evacuate_object(p, _thread);
1115 }
1116 }
1117 };
1118
1119 class ShenandoahEvacuationTask : public WorkerTask {
1120 private:
1121 ShenandoahHeap* const _sh;
1122 ShenandoahCollectionSet* const _cs;
1123 bool _concurrent;
1124 public:
1125 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1126 ShenandoahCollectionSet* cs,
1127 bool concurrent) :
1128 WorkerTask("Shenandoah Evacuation"),
1129 _sh(sh),
1130 _cs(cs),
1131 _concurrent(concurrent)
1132 {}
1133
1134 void work(uint worker_id) {
1135 if (_concurrent) {
1136 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_evac, ShenandoahPhaseTimings::Work, worker_id, true);
1137 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1138 SuspendibleThreadSetJoiner stsj;
1139 do_work();
1140 } else {
1141 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_evac, ShenandoahPhaseTimings::Work, worker_id, true);
1142 ShenandoahParallelWorkerSession worker_session(worker_id);
1143 do_work();
1144 }
1145 }
1146
1147 private:
1148 void do_work() {
1149 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1150 ShenandoahHeapRegion* r;
1151 while ((r =_cs->claim_next()) != nullptr) {
1152 assert(r->has_live(), "Region %zu should have been reclaimed early", r->index());
1153 _sh->marked_object_iterate(r, &cl);
1154
1155 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1156 break;
1157 }
1158 }
1159 }
1160 };
1161
1162 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1163 private:
1164 bool const _resize;
1165 public:
1166 explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1167 void do_thread(Thread* thread) override {
1168 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1169 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1170 gclab->retire();
1171 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1172 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1173 }
1174
1175 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1176 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1177 assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1178
1179 // There are two reasons to retire all plabs between old-gen evacuation passes.
1180 // 1. We need to make the plab memory parsable by remembered-set scanning.
1181 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1182 shenandoah_plab->retire();
1183
1184 // Re-enable promotions for the next evacuation phase.
1185 shenandoah_plab->enable_promotions();
1186
1187 // Reset the fill size for next evacuation phase.
1188 if (_resize && shenandoah_plab->desired_size() > 0) {
1189 shenandoah_plab->set_desired_size(0);
1190 }
1191 }
1192 }
1193 };
1194
1195 class ShenandoahGCStatePropagatorHandshakeClosure : public HandshakeClosure {
1196 public:
1197 explicit ShenandoahGCStatePropagatorHandshakeClosure(char gc_state) :
1198 HandshakeClosure("Shenandoah GC State Change"),
1199 _gc_state(gc_state) {}
1200
1201 void do_thread(Thread* thread) override {
1202 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state);
1203 }
1204 private:
1205 char _gc_state;
1206 };
1207
1208 class ShenandoahPrepareForUpdateRefsHandshakeClosure : public HandshakeClosure {
1209 public:
1210 explicit ShenandoahPrepareForUpdateRefsHandshakeClosure(char gc_state) :
1211 HandshakeClosure("Shenandoah Prepare for Update Refs"),
1212 _retire(ResizeTLAB), _propagator(gc_state) {}
1213
1214 void do_thread(Thread* thread) override {
1215 _propagator.do_thread(thread);
1216 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) {
1217 _retire.do_thread(thread);
1218 }
1219 }
1220 private:
1221 ShenandoahRetireGCLABClosure _retire;
1222 ShenandoahGCStatePropagatorHandshakeClosure _propagator;
1223 };
1224
1225 void ShenandoahHeap::evacuate_collection_set(ShenandoahGeneration* generation, bool concurrent) {
1226 assert(generation->is_global(), "Only global generation expected here");
1227 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1228 workers()->run_task(&task);
1229 }
1230
1231 class ShenandoahCompleteStackWatermarkHandshakeClosure : public HandshakeClosure {
1232 public:
1233 ShenandoahCompleteStackWatermarkHandshakeClosure() : HandshakeClosure("Shenandoah Complete stacks handshake") {}
1234 void do_thread(Thread* thread) override {
1235 if (thread->is_Java_thread()) {
1236 JavaThread* jt = JavaThread::cast(thread);
1237 StackWatermarkSet::finish_processing(jt, nullptr, StackWatermarkKind::gc);
1238 }
1239 }
1240 };
1241
1242 void ShenandoahHeap::concurrent_prepare_for_update_refs() {
1243 // The stack watermarks are active since op_final_roots().
1244 // Make sure the current stack watermark machinery has completed before we drop evac flags.
1245 // Otherwise the stack processing on stack unwinding may enter evac closure concurrently.
1246 ShenandoahCompleteStackWatermarkHandshakeClosure cl;
1247 Handshake::execute(&cl);
1248
1249 {
1250 // Java threads take this lock while they are being attached and added to the list of threads.
1251 // If another thread holds this lock before we update the gc state, it will receive a stale
1252 // gc state, but they will have been added to the list of java threads and so will be corrected
1253 // by the following handshake.
1254 MutexLocker lock(Threads_lock);
1255
1256 // A cancellation at this point means the degenerated cycle must resume from update-refs.
1257 set_gc_state_concurrent(EVACUATION, false);
1258 set_gc_state_concurrent(UPDATE_REFS, true);
1259 }
1260
1261 // This will propagate the gc state and retire gclabs and plabs for threads that require it.
1262 ShenandoahPrepareForUpdateRefsHandshakeClosure prepare_for_update_refs(_gc_state.raw_value());
1263
1264 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately.
1265 Threads::non_java_threads_do(&prepare_for_update_refs);
1266
1267 // Now retire gclabs and plabs and propagate gc_state for mutator threads
1268 Handshake::execute(&prepare_for_update_refs);
1269
1270 _update_refs_iterator.reset();
1271 }
1272
1273 void ShenandoahHeap::op_final_roots() {
1274 #ifdef ASSERT
1275 // Check if stack watermark machinery is in safe state:
1276 // 1. With evac-in-progress, we are about to supersede evac processing with new epoch.
1277 // op_thread_roots() should have completed the stack watermark processing before
1278 // we reach here.
1279 // 2. Without evac-in-progress, we are in abbreviated cycle, and we are switching
1280 // to a new epoch that *also* does not change any oops, which is safe.
1281 if (is_evacuation_in_progress()) {
1282 for (JavaThreadIteratorWithHandle jtiwh; JavaThread* jt = jtiwh.next();) {
1283 StackWatermark* sw = StackWatermarkSet::get(jt, StackWatermarkKind::gc);
1284 assert(sw == nullptr || sw->processing_completed(),
1285 "Cannot turn off weak roots before stack watermark processing is complete");
1286 }
1287 }
1288 #endif
1289
1290 set_gc_state_at_safepoint(WEAK_ROOTS, false);
1291
1292 // Arm the nmethods to change the barriers.
1293 ShenandoahCodeRoots::arm_nmethods();
1294
1295 {
1296 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_roots_propagate_gc_state);
1297 propagate_gc_state_to_all_threads();
1298 }
1299 }
1300
1301 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1302 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1303
1304 ShenandoahHeapRegion* r = heap_region_containing(p);
1305 assert(!r->is_humongous(), "never evacuate humongous objects");
1306
1307 ShenandoahAffiliation target_gen = r->affiliation();
1308 return try_evacuate_object(p, thread, r, target_gen);
1309 }
1310
1311 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1312 ShenandoahAffiliation target_gen) {
1313 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1314 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1315 bool alloc_from_lab = true;
1316 HeapWord* copy = nullptr;
1317 size_t size = ShenandoahForwarding::size(p);
1318
1319 #ifdef ASSERT
1320 if (ShenandoahOOMDuringEvacALot &&
1321 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1322 copy = nullptr;
1323 } else {
1324 #endif
1325 if (UseTLAB) {
1326 copy = allocate_from_gclab(thread, size);
1327 }
1328 if (copy == nullptr) {
1329 // If we failed to allocate in LAB, we'll try a shared allocation.
1330 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1331 copy = allocate_memory(req);
1332 alloc_from_lab = false;
1333 }
1334 #ifdef ASSERT
1335 }
1336 #endif
1337
1338 if (copy == nullptr) {
1339 control_thread()->handle_alloc_failure_evac(size);
1340
1341 // Install the self-forwarded bit on p so other evacuators/LRBs see
1342 // the object as "already handled, do not try to evacuate". The CAS
1343 // may fail if another thread concurrently installed a real forwardee
1344 // (they succeeded where we failed) or self-forwarded first.
1345 markWord old_mark = p->mark();
1346 if (old_mark.is_forwarded()) {
1347 return ShenandoahForwarding::get_forwardee(p);
1348 }
1349 oop winner = ShenandoahForwarding::try_forward_to_self(p, old_mark);
1350 if (winner == nullptr) {
1351 // We own the self-forwarding. Flag the region so the degen/full GC
1352 // entry drain knows to scan it for self_fwd bits to clear.
1353 from_region->set_has_self_forwards();
1354 return p;
1355 }
1356 return winner;
1357 }
1358
1359 if (ShenandoahEvacTracking) {
1360 evac_tracker()->begin_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1361 }
1362
1363 // Copy the object:
1364 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1365
1366 oop copy_val = cast_to_oop(copy);
1367
1368 // Relativize stack chunks before publishing the copy. After the forwarding CAS,
1369 // mutators can see the copy and thaw it via the fast path if flags == 0. We must
1370 // relativize derived pointers and set gc_mode before that happens. Skip if the
1371 // copy's mark word is already a forwarding pointer (another thread won the race
1372 // and overwrote the original's header before we copied it).
1373 if (!ShenandoahForwarding::is_forwarded(copy_val)) {
1374 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1375 }
1376
1377 // Try to install the new forwarding pointer.
1378 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1379 if (result == copy_val) {
1380 // Successfully evacuated. Our copy is now the public one!
1381 shenandoah_assert_correct(nullptr, copy_val);
1382 if (ShenandoahEvacTracking) {
1383 evac_tracker()->end_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1384 }
1385 return copy_val;
1386 } else {
1387 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1388 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1389 // But if it happens to contain references to evacuated regions, those references would
1390 // not get updated for this stale copy during this cycle, and we will crash while scanning
1391 // it the next cycle.
1392 if (alloc_from_lab) {
1393 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1394 // object will overwrite this stale copy, or the filler object on LAB retirement will
1395 // do this.
1396 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1397 } else {
1398 // For non-LAB allocations, we have no way to retract the allocation, and
1399 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1400 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1401 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1402 fill_with_object(copy, size);
1403 shenandoah_assert_correct(nullptr, copy_val);
1404 // For non-LAB allocations, the object has already been registered
1405 }
1406 shenandoah_assert_correct(nullptr, result);
1407 return result;
1408 }
1409 }
1410
1411 // Clear the self_fwd bit on a live cset object, if set. Runs at a safepoint,
1412 // so a plain store is sufficient — no concurrent writers to the mark word.
1413 class ShenandoahUnSelfForwardObjectClosure : public ObjectClosure {
1414 public:
1415 void do_object(oop obj) override {
1416 markWord m = obj->mark();
1417 if (m.is_self_forwarded()) {
1418 obj->set_mark(m.unset_self_forwarded());
1419 }
1420 }
1421 };
1422
1423 // Parallel task over flagged cset regions. Iterates the live objects via the
1424 // mark bitmap (skipping evacuated and never-marked memory), clears self_fwd
1425 // bits, and resets the region flag once done.
1426 class ShenandoahUnSelfForwardTask : public WorkerTask {
1427 private:
1428 ShenandoahHeap* const _heap;
1429 ShenandoahCollectionSet* const _cs;
1430
1431 public:
1432 ShenandoahUnSelfForwardTask(ShenandoahHeap* heap, ShenandoahCollectionSet* cs) :
1433 WorkerTask("Shenandoah Un-Self-Forward"),
1434 _heap(heap),
1435 _cs(cs) {}
1436
1437 void work(uint worker_id) override {
1438 ShenandoahParallelWorkerSession worker_session(worker_id);
1439 ShenandoahUnSelfForwardObjectClosure cl;
1440 ShenandoahHeapRegion* r;
1441 while ((r = _cs->claim_next()) != nullptr) {
1442 if (r->has_self_forwards()) {
1443 _heap->marked_object_iterate(r, &cl);
1444 r->clear_has_self_forwards();
1445 }
1446 }
1447 }
1448 };
1449
1450 void ShenandoahHeap::un_self_forward_cset_regions() {
1451 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1452 ShenandoahCollectionSet* cs = collection_set();
1453 if (cs == nullptr || cs->is_empty()) {
1454 return;
1455 }
1456 cs->clear_current_index();
1457 ShenandoahUnSelfForwardTask task(this, cs);
1458 workers()->run_task(&task);
1459 DEBUG_ONLY(assert_no_self_forwards());
1460 }
1461
1462 #ifdef ASSERT
1463 void ShenandoahHeap::assert_no_self_forwards() const {
1464 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1465 ShenandoahCollectionSet* cs = collection_set();
1466 if (cs == nullptr) return;
1467 cs->clear_current_index();
1468 ShenandoahHeapRegion* r;
1469 while ((r = cs->next()) != nullptr) {
1470 assert(!r->has_self_forwards(), "region still flagged after drain");
1471 }
1472 cs->clear_current_index();
1473 }
1474 #endif
1475
1476 void ShenandoahHeap::trash_cset_regions() {
1477 ShenandoahHeapLocker locker(lock());
1478
1479 ShenandoahCollectionSet* set = collection_set();
1480 ShenandoahHeapRegion* r;
1481 set->clear_current_index();
1482 while ((r = set->next()) != nullptr) {
1483 r->make_trash();
1484 }
1485 collection_set()->clear();
1486 }
1487
1488 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1489 st->print_cr("Heap Regions:");
1490 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1491 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1492 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1493 st->print_cr("UWM=update watermark, U=used");
1494 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1495 st->print_cr("S=shared allocs, L=live data");
1496 st->print_cr("CP=critical pins");
1497
1498 for (size_t i = 0; i < num_regions(); i++) {
1499 get_region(i)->print_on(st);
1500 }
1501 }
1502
1503 void ShenandoahHeap::process_gc_stats() const {
1504 // Commit worker statistics to cycle data
1505 phase_timings()->flush_par_workers_to_cycle();
1506
1507 // Print GC stats for current cycle
1508 LogTarget(Info, gc, stats) lt;
1509 if (lt.is_enabled()) {
1510 ResourceMark rm;
1511 LogStream ls(lt);
1512 phase_timings()->print_cycle_on(&ls);
1513 if (ShenandoahEvacTracking) {
1514 ShenandoahCycleStats evac_stats = evac_tracker()->flush_cycle_to_global();
1515 evac_tracker()->print_evacuations_on(&ls, &evac_stats.workers,
1516 &evac_stats.mutators);
1517 }
1518 }
1519
1520 // Commit statistics to globals
1521 phase_timings()->flush_cycle_to_global();
1522 }
1523
1524 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) const {
1525 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1526 assert(!start->has_live(), "liveness must be zero");
1527
1528 // Do not try to get the size of this humongous object. STW collections will
1529 // have already unloaded classes, so an unmarked object may have a bad klass pointer.
1530 ShenandoahHeapRegion* region = start;
1531 size_t index = region->index();
1532 do {
1533 assert(region->is_humongous(), "Expect correct humongous start or continuation");
1534 assert(!region->is_cset(), "Humongous region should not be in collection set");
1535 region->make_trash_immediate();
1536 region = get_region(++index);
1537 } while (region != nullptr && region->is_humongous_continuation());
1538
1539 // Return number of regions trashed
1540 return index - start->index();
1541 }
1542
1543 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1544 public:
1545 ShenandoahCheckCleanGCLABClosure() {}
1546 void do_thread(Thread* thread) {
1547 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1548 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1549 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1550
1551 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1552 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1553 assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1554 assert(shenandoah_plab->plab()->words_remaining() == 0, "PLAB should not need retirement");
1555 }
1556 }
1557 };
1558
1559 void ShenandoahHeap::labs_make_parsable() {
1560 assert(UseTLAB, "Only call with UseTLAB");
1561
1562 ShenandoahRetireGCLABClosure cl(false);
1563
1564 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1565 ThreadLocalAllocBuffer& tlab = t->tlab();
1566 tlab.make_parsable();
1567 if (ZeroTLAB) {
1568 t->retire_tlab();
1569 }
1570 cl.do_thread(t);
1571 }
1572
1573 workers()->threads_do(&cl);
1574
1575 if (safepoint_workers() != nullptr) {
1576 safepoint_workers()->threads_do(&cl);
1577 }
1578 }
1579
1580 void ShenandoahHeap::tlabs_retire(bool resize) {
1581 assert(UseTLAB, "Only call with UseTLAB");
1582 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1583
1584 ThreadLocalAllocStats stats;
1585
1586 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1587 t->retire_tlab(&stats);
1588 if (resize) {
1589 t->tlab().resize();
1590 }
1591 }
1592
1593 stats.publish();
1594
1595 #ifdef ASSERT
1596 ShenandoahCheckCleanGCLABClosure cl;
1597 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1598 cl.do_thread(t);
1599 }
1600 workers()->threads_do(&cl);
1601 #endif
1602 }
1603
1604 void ShenandoahHeap::gclabs_retire(bool resize) {
1605 assert(UseTLAB, "Only call with UseTLAB");
1606 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1607
1608 ShenandoahRetireGCLABClosure cl(resize);
1609 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1610 cl.do_thread(t);
1611 }
1612
1613 workers()->threads_do(&cl);
1614
1615 if (safepoint_workers() != nullptr) {
1616 safepoint_workers()->threads_do(&cl);
1617 }
1618 }
1619
1620 // Returns size in bytes
1621 size_t ShenandoahHeap::unsafe_max_tlab_alloc() const {
1622 // Return the max allowed size, and let the allocation path
1623 // figure out the safe size for current allocation.
1624 return ShenandoahHeapRegion::max_tlab_size_bytes();
1625 }
1626
1627 size_t ShenandoahHeap::max_tlab_size() const {
1628 // Returns size in words
1629 return ShenandoahHeapRegion::max_tlab_size_words();
1630 }
1631
1632 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) {
1633 // These requests are ignored because we can't easily have Shenandoah jump into
1634 // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent
1635 // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly
1636 // on the VM thread, but this would confuse the control thread mightily and doesn't
1637 // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a
1638 // concurrent cycle in the prologue of the heap inspect/dump operation (see VM_HeapDumper::doit_prologue).
1639 // This is how other concurrent collectors in the JVM handle this scenario as well.
1640 assert(Thread::current()->is_VM_thread(), "Should be the VM thread");
1641 guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause");
1642 }
1643
1644 void ShenandoahHeap::collect(GCCause::Cause cause) {
1645 control_thread()->request_gc(cause);
1646 }
1647
1648 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1649 // This method is only called by `CollectedHeap::collect_as_vm_thread`, which we have
1650 // overridden to do nothing. See the comment there for an explanation of how heap inspections
1651 // work for Shenandoah.
1652 ShouldNotReachHere();
1653 }
1654
1655 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1656 ShenandoahHeapRegion* r = heap_region_containing(addr);
1657 if (r != nullptr) {
1658 return r->block_start(addr);
1659 }
1660 return nullptr;
1661 }
1662
1663 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1664 ShenandoahHeapRegion* r = heap_region_containing(addr);
1665 return r->block_is_obj(addr);
1666 }
1667
1668 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1669 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1670 }
1671
1672 void ShenandoahHeap::prepare_for_verify() {
1673 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1674 labs_make_parsable();
1675 }
1676 }
1677
1678 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1679 if (_shenandoah_policy->is_at_shutdown()) {
1680 return;
1681 }
1682
1683 if (_control_thread != nullptr) {
1684 tcl->do_thread(_control_thread);
1685 }
1686
1687 if (_uncommit_thread != nullptr) {
1688 tcl->do_thread(_uncommit_thread);
1689 }
1690
1691 workers()->threads_do(tcl);
1692 if (_safepoint_workers != nullptr) {
1693 _safepoint_workers->threads_do(tcl);
1694 }
1695 }
1696
1697 void ShenandoahHeap::print_tracing_info() const {
1698 LogTarget(Info, gc, stats) lt;
1699 if (lt.is_enabled()) {
1700 ResourceMark rm;
1701 LogStream ls(lt);
1702
1703 if (ShenandoahEvacTracking) {
1704 evac_tracker()->print_global_on(&ls);
1705 ls.cr();
1706 ls.cr();
1707 }
1708
1709 phase_timings()->print_global_on(&ls);
1710
1711 ls.cr();
1712 ls.cr();
1713
1714 shenandoah_policy()->print_gc_stats(&ls);
1715
1716 ls.cr();
1717 ls.cr();
1718 }
1719 }
1720
1721 // Active generation may only be set by the VM thread at a safepoint.
1722 void ShenandoahHeap::set_active_generation(ShenandoahGeneration* generation) {
1723 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1724 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1725 _active_generation = generation;
1726 }
1727
1728 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation,
1729 bool is_degenerated, bool is_out_of_cycle) {
1730 shenandoah_policy()->record_collection_cause(cause);
1731
1732 const GCCause::Cause current = gc_cause();
1733 assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s",
1734 GCCause::to_string(current), GCCause::to_string(cause));
1735
1736 set_gc_cause(cause);
1737
1738 if (is_degenerated) {
1739 generation->heuristics()->record_degenerated_cycle_start(is_out_of_cycle);
1740 } else {
1741 generation->heuristics()->record_cycle_start();
1742 }
1743 }
1744
1745 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1746 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1747
1748 generation->heuristics()->record_cycle_end();
1749 if (mode()->is_generational() && generation->is_global()) {
1750 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1751 young_generation()->heuristics()->record_cycle_end();
1752 old_generation()->heuristics()->record_cycle_end();
1753 }
1754
1755 set_gc_cause(GCCause::_no_gc);
1756 }
1757
1758 void ShenandoahHeap::verify(VerifyOption vo) {
1759 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1760 if (ShenandoahVerify) {
1761 verifier()->verify_generic(active_generation(), vo);
1762 } else {
1763 // TODO: Consider allocating verification bitmaps on demand,
1764 // and turn this on unconditionally.
1765 }
1766 }
1767 }
1768 size_t ShenandoahHeap::tlab_capacity() const {
1769 return _free_set->capacity_not_holding_lock();
1770 }
1771
1772 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1773 private:
1774 MarkBitMap* _bitmap;
1775 ShenandoahScanObjectStack* _oop_stack;
1776 ShenandoahHeap* const _heap;
1777 ShenandoahMarkingContext* const _marking_context;
1778
1779 template <class T>
1780 void do_oop_work(T* p) {
1781 T o = RawAccess<>::oop_load(p);
1782 if (!CompressedOops::is_null(o)) {
1783 oop obj = CompressedOops::decode_not_null(o);
1784 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1785 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1786 return;
1787 }
1788 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1789
1790 assert(oopDesc::is_oop(obj), "must be a valid oop");
1791 if (!_bitmap->is_marked(obj)) {
1792 _bitmap->mark(obj);
1793 _oop_stack->push(obj);
1794 }
1795 }
1796 }
1797 public:
1798 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1799 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1800 _marking_context(_heap->marking_context()) {}
1801 void do_oop(oop* p) { do_oop_work(p); }
1802 void do_oop(narrowOop* p) { do_oop_work(p); }
1803 };
1804
1805 /*
1806 * This is public API, used in preparation of object_iterate().
1807 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1808 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1809 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1810 */
1811 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1812 // No-op.
1813 }
1814
1815 /*
1816 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1817 *
1818 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1819 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1820 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1821 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1822 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1823 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1824 * wiped the bitmap in preparation for next marking).
1825 *
1826 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1827 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1828 * is allowed to report dead objects, but is not required to do so.
1829 */
1830 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1831 // Reset bitmap
1832 if (!prepare_aux_bitmap_for_iteration())
1833 return;
1834
1835 ShenandoahScanObjectStack oop_stack;
1836 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1837 // Seed the stack with root scan
1838 scan_roots_for_iteration(&oop_stack, &oops);
1839
1840 // Work through the oop stack to traverse heap
1841 while (! oop_stack.is_empty()) {
1842 oop obj = oop_stack.pop();
1843 assert(oopDesc::is_oop(obj), "must be a valid oop");
1844 cl->do_object(obj);
1845 obj->oop_iterate(&oops);
1846 }
1847
1848 assert(oop_stack.is_empty(), "should be empty");
1849 // Reclaim bitmap
1850 reclaim_aux_bitmap_for_iteration();
1851 }
1852
1853 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1854 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1855 if (!_aux_bitmap_region_special) {
1856 bool success = os::commit_memory((char *) _aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false);
1857 if (!success) {
1858 log_warning(gc)("Auxiliary marking bitmap commit failed: " PTR_FORMAT " (%zu bytes)",
1859 p2i(_aux_bitmap_region.start()), _aux_bitmap_region.byte_size());
1860 return false;
1861 }
1862 }
1863 _aux_bit_map.clear();
1864 return true;
1865 }
1866
1867 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1868 // Process GC roots according to current GC cycle
1869 // This populates the work stack with initial objects
1870 // It is important to relinquish the associated locks before diving
1871 // into heap dumper
1872 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1873 ShenandoahHeapIterationRootScanner rp(n_workers);
1874 rp.roots_do(oops);
1875 }
1876
1877 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1878 if (!_aux_bitmap_region_special) {
1879 os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size());
1880 }
1881 }
1882
1883 // Closure for parallelly iterate objects
1884 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1885 private:
1886 MarkBitMap* _bitmap;
1887 ShenandoahObjToScanQueue* _queue;
1888 ShenandoahHeap* const _heap;
1889 ShenandoahMarkingContext* const _marking_context;
1890
1891 template <class T>
1892 void do_oop_work(T* p) {
1893 T o = RawAccess<>::oop_load(p);
1894 if (!CompressedOops::is_null(o)) {
1895 oop obj = CompressedOops::decode_not_null(o);
1896 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1897 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1898 return;
1899 }
1900 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1901
1902 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1903 if (_bitmap->par_mark(obj)) {
1904 _queue->push(ShenandoahMarkTask(obj));
1905 }
1906 }
1907 }
1908 public:
1909 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1910 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1911 _marking_context(_heap->marking_context()) {}
1912 void do_oop(oop* p) { do_oop_work(p); }
1913 void do_oop(narrowOop* p) { do_oop_work(p); }
1914 };
1915
1916 // Object iterator for parallel heap iteraion.
1917 // The root scanning phase happenes in construction as a preparation of
1918 // parallel marking queues.
1919 // Every worker processes it's own marking queue. work-stealing is used
1920 // to balance workload.
1921 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1922 private:
1923 uint _num_workers;
1924 bool _init_ready;
1925 MarkBitMap* _aux_bit_map;
1926 ShenandoahHeap* _heap;
1927 ShenandoahScanObjectStack _roots_stack; // global roots stack
1928 ShenandoahObjToScanQueueSet* _task_queues;
1929 public:
1930 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1931 _num_workers(num_workers),
1932 _init_ready(false),
1933 _aux_bit_map(bitmap),
1934 _heap(ShenandoahHeap::heap()) {
1935 // Initialize bitmap
1936 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1937 if (!_init_ready) {
1938 return;
1939 }
1940
1941 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1942 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1943
1944 _init_ready = prepare_worker_queues();
1945 }
1946
1947 ~ShenandoahParallelObjectIterator() {
1948 // Reclaim bitmap
1949 _heap->reclaim_aux_bitmap_for_iteration();
1950 // Reclaim queue for workers
1951 if (_task_queues!= nullptr) {
1952 for (uint i = 0; i < _num_workers; ++i) {
1953 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1954 if (q != nullptr) {
1955 delete q;
1956 _task_queues->register_queue(i, nullptr);
1957 }
1958 }
1959 delete _task_queues;
1960 _task_queues = nullptr;
1961 }
1962 }
1963
1964 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1965 if (_init_ready) {
1966 object_iterate_parallel(cl, worker_id, _task_queues);
1967 }
1968 }
1969
1970 private:
1971 // Divide global root_stack into worker queues
1972 bool prepare_worker_queues() {
1973 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1974 // Initialize queues for every workers
1975 for (uint i = 0; i < _num_workers; ++i) {
1976 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1977 _task_queues->register_queue(i, task_queue);
1978 }
1979 // Divide roots among the workers. Assume that object referencing distribution
1980 // is related with root kind, use round-robin to make every worker have same chance
1981 // to process every kind of roots
1982 size_t roots_num = _roots_stack.size();
1983 if (roots_num == 0) {
1984 // No work to do
1985 return false;
1986 }
1987
1988 for (uint j = 0; j < roots_num; j++) {
1989 uint stack_id = j % _num_workers;
1990 oop obj = _roots_stack.pop();
1991 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1992 }
1993 return true;
1994 }
1995
1996 void object_iterate_parallel(ObjectClosure* cl,
1997 uint worker_id,
1998 ShenandoahObjToScanQueueSet* queue_set) {
1999 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
2000 assert(queue_set != nullptr, "task queue must not be null");
2001
2002 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
2003 assert(q != nullptr, "object iterate queue must not be null");
2004
2005 ShenandoahMarkTask t;
2006 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
2007
2008 // Work through the queue to traverse heap.
2009 // Steal when there is no task in queue.
2010 while (q->pop(t) || queue_set->steal(worker_id, t)) {
2011 oop obj = t.obj();
2012 assert(oopDesc::is_oop(obj), "must be a valid oop");
2013 cl->do_object(obj);
2014 obj->oop_iterate(&oops);
2015 }
2016 assert(q->is_empty(), "should be empty");
2017 }
2018 };
2019
2020 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
2021 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
2022 }
2023
2024 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
2025 void ShenandoahHeap::keep_alive(oop obj) {
2026 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
2027 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
2028 }
2029 }
2030
2031 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2032 for (size_t i = 0; i < num_regions(); i++) {
2033 ShenandoahHeapRegion* current = get_region(i);
2034 blk->heap_region_do(current);
2035 }
2036 }
2037
2038 class ShenandoahHeapRegionIteratorTask : public WorkerTask {
2039 private:
2040 ShenandoahRegionIterator _regions;
2041 ShenandoahHeapRegionClosure* _closure;
2042
2043 public:
2044 ShenandoahHeapRegionIteratorTask(ShenandoahHeapRegionClosure* closure)
2045 : WorkerTask("Shenandoah Heap Region Iterator")
2046 , _closure(closure) {}
2047
2048 void work(uint worker_id) override {
2049 ShenandoahParallelWorkerSession worker_session(worker_id);
2050 ShenandoahHeapRegion* region = _regions.next();
2051 while (region != nullptr) {
2052 _closure->heap_region_do(region);
2053 region = _regions.next();
2054 }
2055 }
2056 };
2057
2058 class ShenandoahParallelHeapRegionTask : public WorkerTask {
2059 private:
2060 ShenandoahHeap* const _heap;
2061 ShenandoahHeapRegionClosure* const _blk;
2062 size_t const _stride;
2063
2064 shenandoah_padding(0);
2065 Atomic<size_t> _index;
2066 shenandoah_padding(1);
2067
2068 public:
2069 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
2070 WorkerTask("Shenandoah Parallel Region Operation"),
2071 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
2072
2073 void work(uint worker_id) {
2074 ShenandoahParallelWorkerSession worker_session(worker_id);
2075 size_t stride = _stride;
2076
2077 size_t max = _heap->num_regions();
2078 while (_index.load_relaxed() < max) {
2079 size_t cur = _index.fetch_then_add(stride, memory_order_relaxed);
2080 size_t start = cur;
2081 size_t end = MIN2(cur + stride, max);
2082 if (start >= max) break;
2083
2084 for (size_t i = cur; i < end; i++) {
2085 ShenandoahHeapRegion* current = _heap->get_region(i);
2086 _blk->heap_region_do(current);
2087 }
2088 }
2089 }
2090 };
2091
2092 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2093 assert(blk->is_thread_safe(), "Only thread-safe closures here");
2094 const uint active_workers = workers()->active_workers();
2095 const size_t n_regions = num_regions();
2096 size_t stride = blk->parallel_region_stride();
2097 if (stride == 0 && active_workers > 1) {
2098 // Automatically derive the stride to balance the work between threads
2099 // evenly. Do not try to split work if below the reasonable threshold.
2100 constexpr size_t threshold = 4096;
2101 stride = n_regions <= threshold ?
2102 threshold :
2103 (n_regions + active_workers - 1) / active_workers;
2104 }
2105
2106 if (n_regions > stride && active_workers > 1) {
2107 ShenandoahParallelHeapRegionTask task(blk, stride);
2108 workers()->run_task(&task);
2109 } else {
2110 heap_region_iterate(blk);
2111 }
2112 }
2113
2114 void ShenandoahHeap::heap_region_iterator(ShenandoahHeapRegionClosure* closure) const {
2115 ShenandoahHeapRegionIteratorTask task(closure);
2116 workers()->run_task(&task);
2117 }
2118
2119 class ShenandoahRendezvousHandshakeClosure : public HandshakeClosure {
2120 public:
2121 inline ShenandoahRendezvousHandshakeClosure(const char* name) : HandshakeClosure(name) {}
2122 inline void do_thread(Thread* thread) {}
2123 };
2124
2125 void ShenandoahHeap::rendezvous_threads(const char* name) {
2126 ShenandoahRendezvousHandshakeClosure cl(name);
2127 Handshake::execute(&cl);
2128 }
2129
2130 void ShenandoahHeap::recycle_trash() {
2131 free_set()->recycle_trash();
2132 }
2133
2134 void ShenandoahHeap::do_class_unloading() {
2135 _unloader.unload();
2136 if (mode()->is_generational()) {
2137 old_generation()->set_parsable(false);
2138 }
2139 }
2140
2141 void ShenandoahHeap::stw_weak_refs(ShenandoahGeneration* generation, bool full_gc) {
2142 // Weak refs processing
2143 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2144 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2145 ShenandoahTimingsTracker t(phase);
2146 ShenandoahGCWorkerPhase worker_phase(phase);
2147 generation->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2148 }
2149
2150 void ShenandoahHeap::prepare_update_heap_references() {
2151 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2152
2153 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2154 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2155 // for future GCLABs here.
2156 if (UseTLAB) {
2157 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2158 gclabs_retire(ResizeTLAB);
2159 }
2160
2161 _update_refs_iterator.reset();
2162 }
2163
2164 void ShenandoahHeap::propagate_gc_state_to_all_threads() {
2165 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2166 if (_gc_state_changed) {
2167 // If we are only marking old, we do not need to process young pointers
2168 ShenandoahBarrierSet::satb_mark_queue_set().set_filter_out_young(
2169 is_concurrent_old_mark_in_progress() && !is_concurrent_young_mark_in_progress()
2170 );
2171 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
2172 Threads::threads_do(&propagator);
2173 _gc_state_changed = false;
2174 }
2175 }
2176
2177 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) {
2178 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2179 _gc_state.set_cond(mask, value);
2180 _gc_state_changed = true;
2181 }
2182
2183 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) {
2184 // Holding the thread lock here assures that any thread created after we change the gc
2185 // state will have the correct state. It also prevents attaching threads from seeing
2186 // an inconsistent state. See ShenandoahBarrierSet::on_thread_attach for reference. Established
2187 // threads will use their thread local copy of the gc state (changed by a handshake, or on a
2188 // safepoint).
2189 assert(Threads_lock->is_locked(), "Must hold thread lock for concurrent gc state change");
2190 _gc_state.set_cond(mask, value);
2191 }
2192
2193 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2194 uint mask;
2195 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2196 if (!in_progress && is_concurrent_old_mark_in_progress()) {
2197 assert(mode()->is_generational(), "Only generational GC has old marking");
2198 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2199 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2200 mask = YOUNG_MARKING;
2201 } else {
2202 mask = MARKING | YOUNG_MARKING;
2203 }
2204 set_gc_state_at_safepoint(mask, in_progress);
2205 manage_satb_barrier(in_progress);
2206 }
2207
2208 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2209 #ifdef ASSERT
2210 // has_forwarded_objects() iff UPDATE_REFS or EVACUATION
2211 bool has_forwarded = has_forwarded_objects();
2212 bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION);
2213 bool evacuating = _gc_state.is_set(EVACUATION);
2214 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2215 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2216 #endif
2217 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2218 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2219 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2220 set_gc_state_at_safepoint(OLD_MARKING, in_progress);
2221 } else {
2222 set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress);
2223 }
2224 manage_satb_barrier(in_progress);
2225 }
2226
2227 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2228 return old_generation()->is_preparing_for_mark();
2229 }
2230
2231 void ShenandoahHeap::manage_satb_barrier(bool active) {
2232 if (is_concurrent_mark_in_progress()) {
2233 // Ignore request to deactivate barrier while concurrent mark is in progress.
2234 // Do not attempt to re-activate the barrier if it is already active.
2235 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2236 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2237 }
2238 } else {
2239 // No concurrent marking is in progress so honor request to deactivate,
2240 // but only if the barrier is already active.
2241 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2242 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2243 }
2244 }
2245 }
2246
2247 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2248 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2249 set_gc_state_at_safepoint(EVACUATION, in_progress);
2250 }
2251
2252 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2253 if (in_progress) {
2254 _concurrent_strong_root_in_progress.set();
2255 } else {
2256 _concurrent_strong_root_in_progress.unset();
2257 }
2258 }
2259
2260 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2261 set_gc_state_at_safepoint(WEAK_ROOTS, cond);
2262 }
2263
2264 GCTracer* ShenandoahHeap::tracer() {
2265 return shenandoah_policy()->tracer();
2266 }
2267
2268 size_t ShenandoahHeap::tlab_used() const {
2269 return _free_set->used_not_holding_lock();
2270 }
2271
2272 bool ShenandoahHeap::try_cancel_gc(GCCause::Cause cause) {
2273 while (true) {
2274 const GCCause::Cause prev = _cancelled_gc.get();
2275 if (prev != GCCause::_no_gc && prev != GCCause::_shenandoah_concurrent_gc && cause != GCCause::_shenandoah_stop_vm) {
2276 // Only when the gc has not been cancelled, or it has been cancelled to interrupt an old marking cycle
2277 // do we allow the new cancellation request to happen. We make an exception for stopping the VM.
2278 return false;
2279 }
2280
2281 if (_cancelled_gc.cmpxchg(cause, prev) == prev) {
2282 return true;
2283 }
2284 }
2285 }
2286
2287 void ShenandoahHeap::cancel_concurrent_mark() {
2288 if (mode()->is_generational()) {
2289 young_generation()->cancel_marking();
2290 old_generation()->cancel_marking();
2291 }
2292
2293 global_generation()->cancel_marking();
2294
2295 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2296 }
2297
2298 bool ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2299 if (try_cancel_gc(cause)) {
2300 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2301 log_info(gc,thread)("%s", msg.buffer());
2302 Events::log(Thread::current(), "%s", msg.buffer());
2303 _cancel_requested_time = os::elapsedTime();
2304 return true;
2305 }
2306 return false;
2307 }
2308
2309 uint ShenandoahHeap::max_workers() {
2310 return _max_workers;
2311 }
2312
2313 void ShenandoahHeap::stop() {
2314 // The shutdown sequence should be able to terminate when GC is running.
2315
2316 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2317 _shenandoah_policy->record_shutdown();
2318
2319 // Step 1. Stop reporting on gc thread cpu utilization
2320 mmu_tracker()->stop();
2321
2322 // Step 2. Stop decaying allocation rate.
2323 _alloc_rate_decay.disenroll();
2324
2325 // Step 3. Wait until GC worker exits normally (this will cancel any ongoing GC).
2326 control_thread()->stop();
2327
2328 // Step 4. Shutdown uncommit thread.
2329 if (_uncommit_thread != nullptr) {
2330 _uncommit_thread->stop();
2331 }
2332 }
2333
2334 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2335 if (!unload_classes()) return;
2336 ClassUnloadingContext ctx(_workers->active_workers(),
2337 true /* unregister_nmethods_during_purge */,
2338 false /* lock_nmethod_free_separately */);
2339
2340 // Unload classes and purge SystemDictionary.
2341 {
2342 ShenandoahPhaseTimings::Phase phase = full_gc ?
2343 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2344 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2345 ShenandoahIsAliveSelector is_alive;
2346 {
2347 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2348 ShenandoahGCPhase gc_phase(phase);
2349 ShenandoahGCWorkerPhase worker_phase(phase);
2350 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2351
2352 ShenandoahClassUnloadingTask unlink_task(phase, unloading_occurred);
2353 _workers->run_task(&unlink_task);
2354 }
2355 // Release unloaded nmethods's memory.
2356 ClassUnloadingContext::context()->purge_and_free_nmethods();
2357 }
2358
2359 {
2360 ShenandoahGCPhase phase(full_gc ?
2361 ShenandoahPhaseTimings::full_gc_purge_cldg :
2362 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2363 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2364 }
2365 // Resize and verify metaspace
2366 MetaspaceGC::compute_new_size();
2367
2368 if (mode()->is_generational()) {
2369 old_generation()->set_parsable(false);
2370 }
2371
2372 DEBUG_ONLY(MetaspaceUtils::verify();)
2373 }
2374
2375 // Weak roots are either pre-evacuated (final mark) or updated (final update refs),
2376 // so they should not have forwarded oops.
2377 // However, we do need to "null" dead oops in the roots, if can not be done
2378 // in concurrent cycles.
2379 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2380 uint num_workers = _workers->active_workers();
2381 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2382 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2383 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2384 ShenandoahGCPhase phase(timing_phase);
2385 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2386 // Cleanup weak roots
2387 if (has_forwarded_objects()) {
2388 ShenandoahForwardedIsAliveClosure is_alive;
2389 ShenandoahNonConcUpdateRefsClosure keep_alive;
2390 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2391 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2392 _workers->run_task(&cleaning_task);
2393 } else {
2394 ShenandoahIsAliveClosure is_alive;
2395 #ifdef ASSERT
2396 ShenandoahAssertNotForwardedClosure verify_cl;
2397 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2398 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2399 #else
2400 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2401 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2402 #endif
2403 _workers->run_task(&cleaning_task);
2404 }
2405 }
2406
2407 void ShenandoahHeap::parallel_cleaning(ShenandoahGeneration* generation, bool full_gc) {
2408 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2409 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2410 ShenandoahGCPhase phase(full_gc ?
2411 ShenandoahPhaseTimings::full_gc_purge :
2412 ShenandoahPhaseTimings::degen_gc_purge);
2413 stw_weak_refs(generation, full_gc);
2414 stw_process_weak_roots(full_gc);
2415 stw_unload_classes(full_gc);
2416 }
2417
2418 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2419 set_gc_state_at_safepoint(HAS_FORWARDED, cond);
2420 }
2421
2422 void ShenandoahHeap::set_unload_classes(bool uc) {
2423 _unload_classes.set_cond(uc);
2424 }
2425
2426 bool ShenandoahHeap::unload_classes() const {
2427 return _unload_classes.is_set();
2428 }
2429
2430 address ShenandoahHeap::in_cset_fast_test_addr() {
2431 ShenandoahHeap* heap = ShenandoahHeap::heap();
2432 assert(heap->collection_set() != nullptr, "Sanity");
2433 return (address) heap->collection_set()->biased_map_address();
2434 }
2435
2436 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2437 _degenerated_gc_in_progress.set_cond(in_progress);
2438 }
2439
2440 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2441 _full_gc_in_progress.set_cond(in_progress);
2442 }
2443
2444 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2445 assert (is_full_gc_in_progress(), "should be");
2446 _full_gc_move_in_progress.set_cond(in_progress);
2447 }
2448
2449 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2450 set_gc_state_at_safepoint(UPDATE_REFS, in_progress);
2451 }
2452
2453 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2454 ShenandoahCodeRoots::register_nmethod(nm);
2455 }
2456
2457 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2458 ShenandoahCodeRoots::unregister_nmethod(nm);
2459 }
2460
2461 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2462 heap_region_containing(o)->record_pin();
2463 }
2464
2465 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2466 ShenandoahHeapRegion* r = heap_region_containing(o);
2467 assert(r != nullptr, "Sanity");
2468 assert(r->pin_count() > 0, "Region %zu should have non-zero pins", r->index());
2469 r->record_unpin();
2470 }
2471
2472 void ShenandoahHeap::sync_pinned_region_status() {
2473 ShenandoahHeapLocker locker(lock());
2474
2475 for (size_t i = 0; i < num_regions(); i++) {
2476 ShenandoahHeapRegion *r = get_region(i);
2477 if (r->is_active()) {
2478 if (r->is_pinned()) {
2479 if (r->pin_count() == 0) {
2480 r->make_unpinned();
2481 }
2482 } else {
2483 if (r->pin_count() > 0) {
2484 r->make_pinned();
2485 }
2486 }
2487 }
2488 }
2489
2490 assert_pinned_region_status();
2491 }
2492
2493 #ifdef ASSERT
2494 void ShenandoahHeap::assert_pinned_region_status() const {
2495 assert_pinned_region_status(global_generation());
2496 }
2497
2498 void ShenandoahHeap::assert_pinned_region_status(ShenandoahGeneration* generation) const {
2499 for (size_t i = 0; i < num_regions(); i++) {
2500 ShenandoahHeapRegion* r = get_region(i);
2501 if (generation->contains(r)) {
2502 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2503 "Region %zu pinning status is inconsistent", i);
2504 }
2505 }
2506 }
2507 #endif
2508
2509 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2510 return _gc_timer;
2511 }
2512
2513 void ShenandoahHeap::prepare_concurrent_roots() {
2514 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2515 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2516 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2517 set_concurrent_weak_root_in_progress(true);
2518 if (unload_classes()) {
2519 _unloader.prepare();
2520 }
2521 }
2522
2523 void ShenandoahHeap::finish_concurrent_roots() {
2524 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2525 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2526 if (unload_classes()) {
2527 _unloader.finish();
2528 }
2529 }
2530
2531 #ifdef ASSERT
2532 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2533 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2534
2535 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2536 // Use ParallelGCThreads inside safepoints
2537 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2538 ParallelGCThreads, nworkers);
2539 } else {
2540 // Use ConcGCThreads outside safepoints
2541 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2542 ConcGCThreads, nworkers);
2543 }
2544 }
2545 #endif
2546
2547 ShenandoahVerifier* ShenandoahHeap::verifier() {
2548 guarantee(ShenandoahVerify, "Should be enabled");
2549 assert (_verifier != nullptr, "sanity");
2550 return _verifier;
2551 }
2552
2553 template<bool CONCURRENT>
2554 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2555 private:
2556 ShenandoahHeap* _heap;
2557 ShenandoahRegionIterator* _regions;
2558 public:
2559 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2560 WorkerTask("Shenandoah Update References"),
2561 _heap(ShenandoahHeap::heap()),
2562 _regions(regions) {
2563 }
2564
2565 void work(uint worker_id) {
2566 if (CONCURRENT) {
2567 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
2568 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2569 SuspendibleThreadSetJoiner stsj;
2570 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2571 } else {
2572 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
2573 ShenandoahParallelWorkerSession worker_session(worker_id);
2574 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2575 }
2576 }
2577
2578 private:
2579 template<class T>
2580 void do_work(uint worker_id) {
2581 if (CONCURRENT && (worker_id == 0)) {
2582 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2583 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2584 size_t cset_regions = _heap->collection_set()->count();
2585
2586 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2587 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2588 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2589 // next GC cycle.
2590 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2591 }
2592 // If !CONCURRENT, there's no value in expanding Mutator free set
2593 T cl;
2594 ShenandoahHeapRegion* r = _regions->next();
2595 while (r != nullptr) {
2596 HeapWord* update_watermark = r->get_update_watermark();
2597 assert (update_watermark >= r->bottom(), "sanity");
2598 if (r->is_active() && !r->is_cset()) {
2599 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2600 }
2601 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2602 return;
2603 }
2604 r = _regions->next();
2605 }
2606 }
2607 };
2608
2609 void ShenandoahHeap::update_heap_references(ShenandoahGeneration* generation, bool concurrent) {
2610 assert(generation->is_global(), "Should only get global generation here");
2611 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2612
2613 if (concurrent) {
2614 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2615 workers()->run_task(&task);
2616 } else {
2617 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2618 workers()->run_task(&task);
2619 }
2620 }
2621
2622 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2623 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2624 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2625
2626 {
2627 ShenandoahGCPhase phase(concurrent ?
2628 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2629 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2630
2631 final_update_refs_update_region_states();
2632
2633 assert_pinned_region_status();
2634 }
2635
2636 {
2637 ShenandoahGCPhase phase(concurrent ?
2638 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2639 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2640 trash_cset_regions();
2641 }
2642 }
2643
2644 void ShenandoahHeap::final_update_refs_update_region_states() {
2645 ShenandoahSynchronizePinnedRegionStates cl;
2646 parallel_heap_region_iterate(&cl);
2647 }
2648
2649 void ShenandoahHeap::rebuild_free_set_within_phase() {
2650 ShenandoahHeapLocker locker(lock());
2651 size_t young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count;
2652 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count);
2653 // If there are no old regions, first_old_region will be greater than last_old_region
2654 assert((first_old_region > last_old_region) ||
2655 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2656 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2657 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu",
2658 old_region_count, first_old_region, last_old_region);
2659
2660 if (mode()->is_generational()) {
2661 #ifdef ASSERT
2662 if (ShenandoahVerify) {
2663 verifier()->verify_before_rebuilding_free_set();
2664 }
2665 #endif
2666
2667 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2668 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2669 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2670 size_t allocation_runway =
2671 gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_trashed_regions);
2672 gen_heap->compute_old_generation_balance(allocation_runway, old_trashed_regions, young_trashed_regions);
2673 }
2674 // Rebuild free set based on adjusted generation sizes.
2675 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, old_region_count);
2676
2677 if (mode()->is_generational()) {
2678 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2679 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2680 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2681 }
2682 }
2683
2684 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2685 ShenandoahGCPhase phase(concurrent ?
2686 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2687 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2688 rebuild_free_set_within_phase();
2689 }
2690
2691 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2692 size_t slice = r->index() / _bitmap_regions_per_slice;
2693
2694 size_t regions_from = _bitmap_regions_per_slice * slice;
2695 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2696 for (size_t g = regions_from; g < regions_to; g++) {
2697 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2698 if (skip_self && g == r->index()) continue;
2699 if (get_region(g)->is_committed()) {
2700 return true;
2701 }
2702 }
2703 return false;
2704 }
2705
2706 void ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2707 shenandoah_assert_heaplocked();
2708 assert(!is_bitmap_region_special(), "Not for special memory");
2709
2710 if (is_bitmap_slice_committed(r, true)) {
2711 // Some other region from the group is already committed, meaning the bitmap
2712 // slice is already committed, we exit right away.
2713 return;
2714 }
2715
2716 // Commit the bitmap slice:
2717 size_t slice = r->index() / _bitmap_regions_per_slice;
2718 size_t off = _bitmap_bytes_per_slice * slice;
2719 size_t len = _bitmap_bytes_per_slice;
2720 char* start = (char*) _bitmap_region.start() + off;
2721
2722 os::commit_memory_or_exit(start, len, false, "Unable to commit bitmap slice");
2723
2724 if (AlwaysPreTouch) {
2725 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2726 }
2727 }
2728
2729 void ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2730 shenandoah_assert_heaplocked();
2731 assert(!is_bitmap_region_special(), "Not for special memory");
2732
2733 if (is_bitmap_slice_committed(r, true)) {
2734 // Some other region from the group is still committed, meaning the bitmap
2735 // slice should stay committed, exit right away.
2736 return;
2737 }
2738
2739 // Uncommit the bitmap slice:
2740 size_t slice = r->index() / _bitmap_regions_per_slice;
2741 size_t off = _bitmap_bytes_per_slice * slice;
2742 size_t len = _bitmap_bytes_per_slice;
2743
2744 char* addr = (char*) _bitmap_region.start() + off;
2745 os::uncommit_memory(addr, len);
2746 }
2747
2748 void ShenandoahHeap::forbid_uncommit() {
2749 if (_uncommit_thread != nullptr) {
2750 _uncommit_thread->forbid_uncommit();
2751 }
2752 }
2753
2754 void ShenandoahHeap::allow_uncommit() {
2755 if (_uncommit_thread != nullptr) {
2756 _uncommit_thread->allow_uncommit();
2757 }
2758 }
2759
2760 #ifdef ASSERT
2761 bool ShenandoahHeap::is_uncommit_in_progress() {
2762 if (_uncommit_thread != nullptr) {
2763 return _uncommit_thread->is_uncommit_in_progress();
2764 }
2765 return false;
2766 }
2767 #endif
2768
2769 void ShenandoahHeap::safepoint_synchronize_begin() {
2770 StackWatermarkSet::safepoint_synchronize_begin();
2771 SuspendibleThreadSet::synchronize();
2772 }
2773
2774 void ShenandoahHeap::safepoint_synchronize_end() {
2775 SuspendibleThreadSet::desynchronize();
2776 }
2777
2778 void ShenandoahHeap::try_inject_alloc_failure() {
2779 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2780 _inject_alloc_failure.set();
2781 os::naked_short_sleep(1);
2782 if (cancelled_gc()) {
2783 log_info(gc)("Allocation failure was successfully injected");
2784 }
2785 }
2786 }
2787
2788 bool ShenandoahHeap::should_inject_alloc_failure() {
2789 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2790 }
2791
2792 void ShenandoahHeap::try_inject_pin() {
2793 assert(!ShenandoahSafepoint::is_at_shenandoah_safepoint(), "try_inject_pin() must be called outside a safepoint.");
2794 assert(active_generation() != nullptr, "Active generation must be set before we inject pins.");
2795 assert(is_concurrent_mark_in_progress() || active_generation()->is_mark_complete(),
2796 "try_inject_pin() requires marking is in progress or has completed.");
2797 if (ShenandoahPinRegionRate && !cancelled_gc() && ((uintx)(os::random() % 1000) < ShenandoahPinRegionRate) &&
2798 _injected_pin_count < MAX_INJECTED_PINS) {
2799 const size_t idx = os::random() % num_regions();
2800 ShenandoahHeapRegion* r = get_region(idx);
2801 if ((r->is_regular() || r->is_humongous_start()) && r->has_live()) {
2802 r->record_pin();
2803 _injected_pin_indices[_injected_pin_count] = idx;
2804 _injected_pin_count++;
2805 }
2806 }
2807 }
2808
2809 void ShenandoahHeap::release_injected_pins() {
2810 if (_injected_pin_count == 0) {
2811 return;
2812 }
2813
2814 assert(_injected_pin_count <= MAX_INJECTED_PINS,
2815 "Injected pin count: %u exceeds max: %u.", _injected_pin_count, MAX_INJECTED_PINS);
2816 for (uint i = 0; i < _injected_pin_count; i++) {
2817 const size_t idx = _injected_pin_indices[i];
2818 ShenandoahHeapRegion* r = get_region(idx);
2819 assert(r->pin_count() > 0, "Region %zu in tracker must contain a pin.", idx);
2820 r->record_unpin();
2821 }
2822 _injected_pin_count = 0;
2823 }
2824
2825 void ShenandoahHeap::initialize_serviceability() {
2826 _memory_pool = new ShenandoahMemoryPool(this);
2827 _cycle_memory_manager.add_pool(_memory_pool);
2828 _stw_memory_manager.add_pool(_memory_pool);
2829 }
2830
2831 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2832 GrowableArray<GCMemoryManager*> memory_managers(2);
2833 memory_managers.append(&_cycle_memory_manager);
2834 memory_managers.append(&_stw_memory_manager);
2835 return memory_managers;
2836 }
2837
2838 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2839 GrowableArray<MemoryPool*> memory_pools(1);
2840 memory_pools.append(_memory_pool);
2841 return memory_pools;
2842 }
2843
2844 MemoryUsage ShenandoahHeap::memory_usage() {
2845 return shenandoah_memory_usage(_initial_size, used(), committed(), max_capacity());
2846 }
2847
2848 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2849 _heap(ShenandoahHeap::heap()),
2850 _index(0) {}
2851
2852 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2853 _heap(heap),
2854 _index(0) {}
2855
2856 void ShenandoahRegionIterator::reset() {
2857 _index.store_relaxed(0);
2858 }
2859
2860 bool ShenandoahRegionIterator::has_next() const {
2861 return _index.load_relaxed() < _heap->num_regions();
2862 }
2863
2864 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2865 #ifdef ASSERT
2866 assert(_liveness_cache != nullptr, "sanity");
2867 assert(worker_id < _max_workers, "sanity");
2868 for (uint i = 0; i < num_regions(); i++) {
2869 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2870 }
2871 #endif
2872 return _liveness_cache[worker_id];
2873 }
2874
2875 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2876 assert(worker_id < _max_workers, "sanity");
2877 assert(_liveness_cache != nullptr, "sanity");
2878 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2879 for (uint i = 0; i < num_regions(); i++) {
2880 ShenandoahLiveData live = ld[i];
2881 if (live > 0) {
2882 ShenandoahHeapRegion* r = get_region(i);
2883 r->increase_live_data_gc_words(live);
2884 ld[i] = 0;
2885 }
2886 }
2887 }
2888
2889 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2890 if (is_idle()) return false;
2891
2892 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2893 // marking phase.
2894 if (is_concurrent_mark_in_progress() &&
2895 !marking_context()->allocated_after_mark_start(obj)) {
2896 return true;
2897 }
2898
2899 // Can not guarantee obj is deeply good.
2900 if (has_forwarded_objects()) {
2901 return true;
2902 }
2903
2904 return false;
2905 }
2906
2907 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2908 #if INCLUDE_CDS_JAVA_HEAP
2909 // CDS wants a raw continuous memory range to load a bunch of objects itself.
2910 // This is an unusual request, since all requested regions should be regular, not humongous.
2911 //
2912 // CDS would guarantee no objects straddle multiple regions, as long as regions are as large
2913 // as MIN_GC_REGION_ALIGNMENT.
2914 guarantee(ShenandoahHeapRegion::region_size_bytes() >= AOTMappedHeapWriter::MIN_GC_REGION_ALIGNMENT, "Must be");
2915
2916 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_cds(size);
2917 return allocate_memory(req);
2918 #else
2919 assert(false, "Archive heap loader should not be available, should not be here");
2920 return nullptr;
2921 #endif // INCLUDE_CDS_JAVA_HEAP
2922 }
2923
2924 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2925 // Nothing to do here, except checking that heap looks fine.
2926 #ifdef ASSERT
2927 HeapWord* start = archive_space.start();
2928 HeapWord* end = archive_space.end();
2929
2930 // No unclaimed space between the objects.
2931 // Objects are properly allocated in correct regions.
2932 HeapWord* cur = start;
2933 while (cur < end) {
2934 oop oop = cast_to_oop(cur);
2935 shenandoah_assert_in_correct_region(nullptr, oop);
2936 cur += oop->size();
2937 }
2938
2939 // No unclaimed tail at the end of archive space.
2940 assert(cur == end,
2941 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2942 p2i(cur), p2i(end));
2943
2944 // All regions in contiguous space have good state.
2945 size_t begin_reg_idx = heap_region_index_containing(start);
2946 size_t end_reg_idx = heap_region_index_containing(end);
2947
2948 for (size_t idx = begin_reg_idx; idx <= end_reg_idx; idx++) {
2949 ShenandoahHeapRegion* r = get_region(idx);
2950 assert(r->is_regular(), "Must be regular");
2951 assert(r->is_young(), "Must be young");
2952 assert(idx == end_reg_idx || r->top() == r->end(),
2953 "All regions except the last one should be full: " PTR_FORMAT " " PTR_FORMAT,
2954 p2i(r->top()), p2i(r->end()));
2955 assert(idx != begin_reg_idx || r->bottom() == start,
2956 "Archive space start should be at the bottom of first region: " PTR_FORMAT " " PTR_FORMAT,
2957 p2i(r->bottom()), p2i(start));
2958 assert(idx != end_reg_idx || r->top() == end,
2959 "Archive space end should be at the top of last region: " PTR_FORMAT " " PTR_FORMAT,
2960 p2i(r->top()), p2i(end));
2961 }
2962
2963 #endif
2964 }
2965
2966 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2967 if (!mode()->is_generational()) {
2968 return global_generation();
2969 } else if (affiliation == YOUNG_GENERATION) {
2970 return young_generation();
2971 } else if (affiliation == OLD_GENERATION) {
2972 return old_generation();
2973 }
2974
2975 ShouldNotReachHere();
2976 return nullptr;
2977 }
2978
2979 void ShenandoahHeap::log_heap_status(const char* msg) const {
2980 if (mode()->is_generational()) {
2981 young_generation()->log_status(msg);
2982 old_generation()->log_status(msg);
2983 } else {
2984 global_generation()->log_status(msg);
2985 }
2986 }
2987
2988 ShenandoahHeapLocker::ShenandoahHeapLocker(ShenandoahHeapLock* lock, bool allow_block_for_safepoint) : _lock(lock) {
2989 #ifdef ASSERT
2990 ShenandoahFreeSet* free_set = ShenandoahHeap::heap()->free_set();
2991 // free_set is nullptr only at pre-initialized state
2992 assert(free_set == nullptr || !free_set->rebuild_lock()->owned_by_self(), "Dead lock, can't acquire heap lock while holding free-set rebuild lock");
2993 assert(_lock != nullptr, "Must not");
2994 #endif
2995 _lock->lock(allow_block_for_safepoint);
2996 }