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/shenandoahStackChunkGCData.inline.hpp"
77 #include "gc/shenandoah/shenandoahStackWatermark.hpp"
78 #include "gc/shenandoah/shenandoahSTWMark.hpp"
79 #include "gc/shenandoah/shenandoahUncommitThread.hpp"
80 #include "gc/shenandoah/shenandoahUtils.hpp"
81 #include "gc/shenandoah/shenandoahVerifier.hpp"
82 #include "gc/shenandoah/shenandoahVMOperations.hpp"
83 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
84 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
85 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
86 #include "memory/allocation.hpp"
87 #include "memory/classLoaderMetaspace.hpp"
88 #include "memory/memoryReserver.hpp"
89 #include "memory/metaspaceUtils.hpp"
90 #include "memory/universe.hpp"
91 #include "nmt/mallocTracker.hpp"
92 #include "nmt/memTracker.hpp"
93 #include "oops/compressedOops.inline.hpp"
94 #include "prims/jvmtiTagMap.hpp"
95 #include "runtime/atomic.hpp"
96 #include "runtime/atomicAccess.hpp"
97 #include "runtime/globals.hpp"
98 #include "runtime/interfaceSupport.inline.hpp"
99 #include "runtime/java.hpp"
100 #include "runtime/orderAccess.hpp"
101 #include "runtime/safepointMechanism.hpp"
102 #include "runtime/stackWatermarkSet.hpp"
103 #include "runtime/threads.hpp"
104 #include "runtime/vmThread.hpp"
105 #include "utilities/events.hpp"
106 #include "utilities/globalDefinitions.hpp"
107 #include "utilities/powerOfTwo.hpp"
108 #if INCLUDE_JFR
109 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
110 #endif
111
112 class ShenandoahPretouchHeapTask : public WorkerTask {
113 private:
114 ShenandoahRegionIterator _regions;
115 const size_t _page_size;
116 public:
117 ShenandoahPretouchHeapTask(size_t page_size) :
118 WorkerTask("Shenandoah Pretouch Heap"),
119 _page_size(page_size) {}
120
121 virtual void work(uint worker_id) {
122 ShenandoahHeapRegion* r = _regions.next();
123 while (r != nullptr) {
124 if (r->is_committed()) {
125 os::pretouch_memory(r->bottom(), r->end(), _page_size);
126 }
127 r = _regions.next();
128 }
129 }
130 };
131
132 class ShenandoahPretouchBitmapTask : public WorkerTask {
133 private:
134 ShenandoahRegionIterator _regions;
135 char* _bitmap_base;
136 const size_t _bitmap_size;
137 const size_t _page_size;
138 public:
139 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
140 WorkerTask("Shenandoah Pretouch Bitmap"),
141 _bitmap_base(bitmap_base),
142 _bitmap_size(bitmap_size),
143 _page_size(page_size) {}
144
145 virtual void work(uint worker_id) {
146 ShenandoahHeapRegion* r = _regions.next();
147 while (r != nullptr) {
148 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
149 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
150 assert (end <= _bitmap_size, "end is sane: %zu < %zu", end, _bitmap_size);
151
152 if (r->is_committed()) {
153 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
154 }
155
156 r = _regions.next();
157 }
158 }
159 };
160
161 static ReservedSpace reserve(size_t size, size_t preferred_page_size) {
162 // When a page size is given we don't want to mix large
163 // and normal pages. If the size is not a multiple of the
164 // page size it will be aligned up to achieve this.
165 size_t alignment = os::vm_allocation_granularity();
166 if (preferred_page_size != os::vm_page_size()) {
167 alignment = MAX2(preferred_page_size, alignment);
168 size = align_up(size, alignment);
169 }
170
171 const ReservedSpace reserved = MemoryReserver::reserve(size, alignment, preferred_page_size, mtGC);
172 if (!reserved.is_reserved()) {
173 vm_exit_during_initialization("Could not reserve space");
174 }
175 return reserved;
176 }
177
178 jint ShenandoahHeap::initialize() {
179 //
180 // Figure out heap sizing
181 //
182
183 size_t init_byte_size = InitialHeapSize;
184 size_t min_byte_size = MinHeapSize;
185 size_t max_byte_size = MaxHeapSize;
186 size_t heap_alignment = HeapAlignment;
187
188 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
189
190 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
191 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
192
193 _num_regions = ShenandoahHeapRegion::region_count();
194 assert(_num_regions == (max_byte_size / reg_size_bytes),
195 "Regions should cover entire heap exactly: %zu != %zu/%zu",
196 _num_regions, max_byte_size, reg_size_bytes);
197
198 size_t num_committed_regions = init_byte_size / reg_size_bytes;
199 num_committed_regions = MIN2(num_committed_regions, _num_regions);
200 assert(num_committed_regions <= _num_regions, "sanity");
201 _initial_size = num_committed_regions * reg_size_bytes;
202
203 size_t num_min_regions = min_byte_size / reg_size_bytes;
204 num_min_regions = MIN2(num_min_regions, _num_regions);
205 assert(num_min_regions <= _num_regions, "sanity");
206 _minimum_size = num_min_regions * reg_size_bytes;
207
208 _soft_max_size.store_relaxed(clamp(SoftMaxHeapSize, min_capacity(), max_capacity()));
209
210 _committed.store_relaxed(_initial_size);
211
212 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
213 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
214 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
215
216 //
217 // Reserve and commit memory for heap
218 //
219
220 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
221 initialize_reserved_region(heap_rs);
222 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
223 _heap_region_special = heap_rs.special();
224
225 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
226 "Misaligned heap: " PTR_FORMAT, p2i(base()));
227 os::trace_page_sizes_for_requested_size("Heap",
228 max_byte_size, heap_alignment,
229 heap_rs.base(),
230 heap_rs.size(), heap_rs.page_size());
231
232 #if SHENANDOAH_OPTIMIZED_MARKTASK
233 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
234 // Fail if we ever attempt to address more than we can.
235 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
236 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
237 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
238 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
239 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
240 vm_exit_during_initialization("Fatal Error", buf);
241 }
242 #endif
243
244 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
245 if (!_heap_region_special) {
246 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
247 "Cannot commit heap memory");
248 }
249
250 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
251
252 // Now we know the number of regions and heap sizes, initialize the heuristics.
253 initialize_heuristics();
254
255 // If ShenandoahCardBarrier is enabled but it's not generational mode
256 // it means we're under passive mode and we have to initialize old gen
257 // for the purpose of having card table.
258 if (ShenandoahCardBarrier && !(mode()->is_generational())) {
259 _old_generation = new ShenandoahOldGeneration(max_workers());
260 }
261
262 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
263
264 //
265 // Worker threads must be initialized after the barrier is configured
266 //
267 _workers = new ShenandoahWorkerThreads("ShenWorker", _max_workers);
268 if (_workers == nullptr) {
269 vm_exit_during_initialization("Failed necessary allocation.");
270 } else {
271 _workers->initialize_workers();
272 }
273
274 if (ParallelGCThreads > 1) {
275 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
276 _safepoint_workers->initialize_workers();
277 }
278
279 //
280 // Reserve and commit memory for bitmap(s)
281 //
282
283 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
284 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
285
286 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
287
288 guarantee(bitmap_bytes_per_region != 0,
289 "Bitmap bytes per region should not be zero");
290 guarantee(is_power_of_2(bitmap_bytes_per_region),
291 "Bitmap bytes per region should be power of two: %zu", bitmap_bytes_per_region);
292
293 if (bitmap_page_size > bitmap_bytes_per_region) {
294 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
295 _bitmap_bytes_per_slice = bitmap_page_size;
296 } else {
297 _bitmap_regions_per_slice = 1;
298 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
299 }
300
301 guarantee(_bitmap_regions_per_slice >= 1,
302 "Should have at least one region per slice: %zu",
303 _bitmap_regions_per_slice);
304
305 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
306 "Bitmap slices should be page-granular: bps = %zu, page size = %zu",
307 _bitmap_bytes_per_slice, bitmap_page_size);
308
309 ReservedSpace bitmap = reserve(_bitmap_size, bitmap_page_size);
310 os::trace_page_sizes_for_requested_size("Mark Bitmap",
311 bitmap_size_orig, bitmap_page_size,
312 bitmap.base(),
313 bitmap.size(), bitmap.page_size());
314 MemTracker::record_virtual_memory_tag(bitmap, mtGC);
315 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
316 _bitmap_region_special = bitmap.special();
317
318 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
319 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
320 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
321 if (!_bitmap_region_special) {
322 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
323 "Cannot commit bitmap memory");
324 }
325
326 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
327
328 if (ShenandoahVerify) {
329 ReservedSpace verify_bitmap = reserve(_bitmap_size, bitmap_page_size);
330 os::trace_page_sizes_for_requested_size("Verify Bitmap",
331 bitmap_size_orig, bitmap_page_size,
332 verify_bitmap.base(),
333 verify_bitmap.size(), verify_bitmap.page_size());
334 if (!verify_bitmap.special()) {
335 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
336 "Cannot commit verification bitmap memory");
337 }
338 MemTracker::record_virtual_memory_tag(verify_bitmap, mtGC);
339 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
340 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
341 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
342 }
343
344 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
345 size_t aux_bitmap_page_size = bitmap_page_size;
346
347 ReservedSpace aux_bitmap = reserve(_bitmap_size, aux_bitmap_page_size);
348 os::trace_page_sizes_for_requested_size("Aux Bitmap",
349 bitmap_size_orig, aux_bitmap_page_size,
350 aux_bitmap.base(),
351 aux_bitmap.size(), aux_bitmap.page_size());
352 MemTracker::record_virtual_memory_tag(aux_bitmap, mtGC);
353 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
354 _aux_bitmap_region_special = aux_bitmap.special();
355 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
356
357 //
358 // Create regions and region sets
359 //
360 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
361 size_t region_storage_size_orig = region_align * _num_regions;
362 size_t region_storage_size = align_up(region_storage_size_orig,
363 MAX2(region_page_size, os::vm_allocation_granularity()));
364
365 ReservedSpace region_storage = reserve(region_storage_size, region_page_size);
366 os::trace_page_sizes_for_requested_size("Region Storage",
367 region_storage_size_orig, region_page_size,
368 region_storage.base(),
369 region_storage.size(), region_storage.page_size());
370 MemTracker::record_virtual_memory_tag(region_storage, mtGC);
371 if (!region_storage.special()) {
372 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
373 "Cannot commit region memory");
374 }
375
376 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
377 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
378 // If not successful, bite a bullet and allocate at whatever address.
379 {
380 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
381 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
382 const size_t cset_page_size = os::vm_page_size();
383
384 uintptr_t min = round_up_power_of_2(cset_align);
385 uintptr_t max = (1u << 30u);
386 ReservedSpace cset_rs;
387
388 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
389 char* req_addr = (char*)addr;
390 assert(is_aligned(req_addr, cset_align), "Should be aligned");
391 cset_rs = MemoryReserver::reserve(req_addr, cset_size, cset_align, cset_page_size, mtGC);
392 if (cset_rs.is_reserved()) {
393 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
394 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
395 break;
396 }
397 }
398
399 if (_collection_set == nullptr) {
400 cset_rs = MemoryReserver::reserve(cset_size, cset_align, os::vm_page_size(), mtGC);
401 if (!cset_rs.is_reserved()) {
402 vm_exit_during_initialization("Cannot reserve memory for collection set");
403 }
404
405 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
406 }
407 os::trace_page_sizes_for_requested_size("Collection Set",
408 cset_size, cset_page_size,
409 cset_rs.base(),
410 cset_rs.size(), cset_rs.page_size());
411 }
412
413 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
414 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
415
416 {
417 ShenandoahHeapLocker locker(lock());
418 for (size_t i = 0; i < _num_regions; i++) {
419 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
420 bool is_committed = i < num_committed_regions;
421 void* loc = region_storage.base() + i * region_align;
422
423 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
424 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
425
426 _marking_context->initialize_top_at_mark_start(r);
427 _regions[i] = r;
428 assert(!collection_set()->is_in(i), "New region should not be in collection set");
429
430 _affiliations[i] = ShenandoahAffiliation::FREE;
431 }
432
433 if (mode()->is_generational()) {
434 size_t young_reserve = (soft_max_capacity() * ShenandoahEvacReserve) / 100;
435 young_generation()->set_evacuation_reserve(young_reserve);
436 old_generation()->set_evacuation_reserve((size_t) 0);
437 old_generation()->set_promoted_reserve((size_t) 0);
438 }
439
440 _free_set = new ShenandoahFreeSet(this, _num_regions);
441 _allocator = new ShenandoahAllocator(_free_set);
442 initialize_generations();
443
444 // We are initializing free set. We ignore cset region tallies.
445 size_t young_trashed_regions, old_trashed_regions, first_old, last_old, num_old;
446 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old, last_old, num_old);
447 if (mode()->is_generational()) {
448 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
449 // We cannot call
450 // gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions)
451 // until after the heap is fully initialized. So we make up a safe value here.
452 size_t allocation_runway = InitialHeapSize / 2;
453 // We're initializing the heap. All regions within young are initially empty.
454 size_t max_transfer = allocation_runway;
455 gen_heap->compute_old_generation_balance(max_transfer, old_trashed_regions, young_trashed_regions);
456 }
457 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, num_old);
458 }
459
460 if (AlwaysPreTouch) {
461 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
462 // before initialize() below zeroes it with initializing thread. For any given region,
463 // we touch the region and the corresponding bitmaps from the same thread.
464 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
465
466 _pretouch_heap_page_size = heap_page_size;
467 _pretouch_bitmap_page_size = bitmap_page_size;
468
469 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
470 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
471
472 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
473 _workers->run_task(&bcl);
474
475 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
476 _workers->run_task(&hcl);
477 }
478
479 //
480 // Initialize the rest of GC subsystems
481 //
482
483 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
484 for (uint worker = 0; worker < _max_workers; worker++) {
485 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
486 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
487 }
488
489 // There should probably be Shenandoah-specific options for these,
490 // just as there are G1-specific options.
491 {
492 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
493 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
494 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
495 }
496
497 _monitoring_support = new ShenandoahMonitoringSupport(this);
498 _phase_timings = new ShenandoahPhaseTimings(max_workers());
499 ShenandoahCodeRoots::initialize();
500
501 // Initialization of controller makes use of variables established by initialize_heuristics.
502 initialize_controller();
503
504 // Certain initialization of heuristics must be deferred until after controller is initialized.
505 post_initialize_heuristics();
506 start_idle_span();
507 if (ShenandoahUncommit) {
508 _uncommit_thread = new ShenandoahUncommitThread(this);
509 }
510 print_init_logger();
511 FullGCForwarding::initialize(_heap_region);
512 return JNI_OK;
513 }
514
515 void ShenandoahHeap::initialize_controller() {
516 _control_thread = new ShenandoahControlThread();
517 }
518
519 void ShenandoahHeap::print_init_logger() const {
520 ShenandoahInitLogger::print();
521 }
522
523 void ShenandoahHeap::initialize_mode() {
524 if (ShenandoahGCMode != nullptr) {
525 if (strcmp(ShenandoahGCMode, "satb") == 0) {
526 _gc_mode = new ShenandoahSATBMode();
527 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
528 _gc_mode = new ShenandoahPassiveMode();
529 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
530 _gc_mode = new ShenandoahGenerationalMode();
531 } else {
532 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
533 }
534 } else {
535 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
536 }
537 _gc_mode->initialize_flags();
538 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
539 vm_exit_during_initialization(
540 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
541 _gc_mode->name()));
542 }
543 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
544 vm_exit_during_initialization(
545 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
546 _gc_mode->name()));
547 }
548 }
549
550 void ShenandoahHeap::initialize_heuristics() {
551 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers());
552 _global_generation->initialize_heuristics(mode());
553 }
554
555 #ifdef _MSC_VER
556 #pragma warning( push )
557 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
558 #endif
559
560 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
561 CollectedHeap(),
562 _active_generation(nullptr),
563 _initial_size(0),
564 _committed(0),
565 _alloc_rate_decay(&_alloc_rate),
566 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
567 _workers(nullptr),
568 _safepoint_workers(nullptr),
569 _heap_region_special(false),
570 _num_regions(0),
571 _regions(nullptr),
572 _affiliations(nullptr),
573 _gc_state_changed(false),
574 _gc_no_progress_count(0),
575 _cancel_requested_time(0),
576 _update_refs_iterator(this),
577 _global_generation(nullptr),
578 _control_thread(nullptr),
579 _uncommit_thread(nullptr),
580 _young_generation(nullptr),
581 _old_generation(nullptr),
582 _shenandoah_policy(policy),
583 _gc_mode(nullptr),
584 _free_set(nullptr),
585 _allocator(nullptr),
586 _verifier(nullptr),
587 _phase_timings(nullptr),
588 _monitoring_support(nullptr),
589 _memory_pool(nullptr),
590 _stw_memory_manager("Shenandoah Pauses"),
591 _cycle_memory_manager("Shenandoah Cycles"),
592 _gc_timer(new ConcurrentGCTimer()),
593 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
594 _marking_context(nullptr),
595 _bitmap_size(0),
596 _bitmap_regions_per_slice(0),
597 _bitmap_bytes_per_slice(0),
598 _bitmap_region_special(false),
599 _aux_bitmap_region_special(false),
600 _liveness_cache(nullptr),
601 _collection_set(nullptr),
602 _evac_tracker(new ShenandoahEvacuationTracker()),
603 _injected_pin_count(0)
604 {
605 // Initialize GC mode early, many subsequent initialization procedures depend on it
606 initialize_mode();
607 _cancelled_gc.set(GCCause::_no_gc);
608 }
609
610 #ifdef _MSC_VER
611 #pragma warning( pop )
612 #endif
613
614 void ShenandoahHeap::print_heap_on(outputStream* st) const {
615 const bool is_generational = mode()->is_generational();
616 const char* front_spacing = "";
617 if (is_generational) {
618 st->print_cr("Generational Shenandoah Heap");
619 st->print_cr(" Young:");
620 st->print_cr(" " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(young_generation()->max_capacity()), PROPERFMTARGS(young_generation()->used()));
621 st->print_cr(" Old:");
622 st->print_cr(" " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(old_generation()->max_capacity()), PROPERFMTARGS(old_generation()->used()));
623 st->print_cr(" Entire heap:");
624 st->print_cr(" " PROPERFMT " soft max, " PROPERFMT " committed",
625 PROPERFMTARGS(soft_max_capacity()), PROPERFMTARGS(committed()));
626 front_spacing = " ";
627 } else {
628 st->print_cr("Shenandoah Heap");
629 st->print_cr(" " PROPERFMT " max, " PROPERFMT " soft max, " PROPERFMT " committed, " PROPERFMT " used",
630 PROPERFMTARGS(max_capacity()),
631 PROPERFMTARGS(soft_max_capacity()),
632 PROPERFMTARGS(committed()),
633 PROPERFMTARGS(used())
634 );
635 }
636 st->print_cr("%s %zu x " PROPERFMT " regions",
637 front_spacing,
638 num_regions(),
639 PROPERFMTARGS(ShenandoahHeapRegion::region_size_bytes()));
640
641 st->print("Status: ");
642 if (has_forwarded_objects()) st->print("has forwarded objects, ");
643 if (!is_generational) {
644 if (is_concurrent_mark_in_progress()) st->print("marking,");
645 } else {
646 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
647 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
648 }
649 if (is_evacuation_in_progress()) st->print("evacuating, ");
650 if (is_update_refs_in_progress()) st->print("updating refs, ");
651 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
652 if (is_full_gc_in_progress()) st->print("full gc, ");
653 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
654 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
655 if (is_concurrent_strong_root_in_progress() &&
656 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
657
658 if (cancelled_gc()) {
659 st->print("cancelled");
660 } else {
661 st->print("not cancelled");
662 }
663 st->cr();
664
665 st->print_cr("Reserved region:");
666 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
667 p2i(reserved_region().start()),
668 p2i(reserved_region().end()));
669
670 ShenandoahCollectionSet* cset = collection_set();
671 st->print_cr("Collection set:");
672 if (cset != nullptr) {
673 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
674 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
675 } else {
676 st->print_cr(" (null)");
677 }
678
679 st->cr();
680
681 if (Verbose) {
682 st->cr();
683 print_heap_regions_on(st);
684 }
685 }
686
687 void ShenandoahHeap::print_gc_on(outputStream* st) const {
688 print_heap_regions_on(st);
689 }
690
691 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
692 public:
693 void do_thread(Thread* thread) {
694 assert(thread != nullptr, "Sanity");
695 ShenandoahThreadLocalData::initialize_gclab(thread);
696 }
697 };
698
699 void ShenandoahHeap::initialize_generations() {
700 _global_generation->post_initialize(this);
701 }
702
703 // We do not call this explicitly It is called by Hotspot infrastructure.
704 void ShenandoahHeap::post_initialize() {
705 CollectedHeap::post_initialize();
706
707 check_soft_max_changed();
708
709 // Schedule periodic task to report on gc thread CPU utilization
710 _mmu_tracker.initialize();
711
712 // Periodically decay allocation rate to compensate for not being updated when allocation rate
713 // is low. Heuristics are evaluated unconditionally from a dedicated thread so it will continue
714 // to see the last (possibly stale) allocation rate if the allocation rate is low.
715 _alloc_rate_decay.enroll();
716
717 MutexLocker ml(Threads_lock);
718
719 ShenandoahInitWorkerGCLABClosure init_gclabs;
720 _workers->threads_do(&init_gclabs);
721
722 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
723 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
724 _workers->set_initialize_gclab();
725
726 // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump
727 // during a concurrent evacuation phase.
728 if (_safepoint_workers != nullptr) {
729 _safepoint_workers->threads_do(&init_gclabs);
730 _safepoint_workers->set_initialize_gclab();
731 }
732
733 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
734 }
735
736 void ShenandoahHeap::post_initialize_heuristics() {
737 _global_generation->post_initialize_heuristics();
738 }
739
740 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
741 return _global_generation->heuristics();
742 }
743
744 size_t ShenandoahHeap::used() const {
745 return global_generation()->used();
746 }
747
748 size_t ShenandoahHeap::committed() const {
749 return _committed.load_relaxed();
750 }
751
752 void ShenandoahHeap::increase_committed(size_t bytes) {
753 shenandoah_assert_heaplocked_or_safepoint();
754 _committed.fetch_then_add(bytes, memory_order_relaxed);
755 }
756
757 void ShenandoahHeap::decrease_committed(size_t bytes) {
758 shenandoah_assert_heaplocked_or_safepoint();
759 _committed.fetch_then_sub(bytes, memory_order_relaxed);
760 }
761
762 size_t ShenandoahHeap::capacity() const {
763 return committed();
764 }
765
766 size_t ShenandoahHeap::max_capacity() const {
767 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
768 }
769
770 size_t ShenandoahHeap::soft_max_capacity() const {
771 size_t v = _soft_max_size.load_relaxed();
772 assert(min_capacity() <= v && v <= max_capacity(),
773 "Should be in bounds: %zu <= %zu <= %zu",
774 min_capacity(), v, max_capacity());
775 return v;
776 }
777
778 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
779 assert(min_capacity() <= v && v <= max_capacity(),
780 "Should be in bounds: %zu <= %zu <= %zu",
781 min_capacity(), v, max_capacity());
782 _soft_max_size.store_relaxed(v);
783 heuristics()->compute_headroom_adjustment();
784 }
785
786 size_t ShenandoahHeap::min_capacity() const {
787 return _minimum_size;
788 }
789
790 size_t ShenandoahHeap::initial_capacity() const {
791 return _initial_size;
792 }
793
794 bool ShenandoahHeap::is_in(const void* p) const {
795 if (!is_in_reserved(p)) {
796 return false;
797 }
798
799 if (is_full_gc_move_in_progress()) {
800 // Full GC move is running, we do not have a consistent region
801 // information yet. But we know the pointer is in heap.
802 return true;
803 }
804
805 // Now check if we point to a live section in active region.
806 const ShenandoahHeapRegion* r = heap_region_containing(p);
807 if (p >= r->top()) {
808 return false;
809 }
810
811 if (r->is_active()) {
812 return true;
813 }
814
815 // The region is trash, but won't be recycled until after concurrent weak
816 // roots. We also don't allow mutators to allocate from trash regions
817 // during weak roots. Concurrent class unloading may access unmarked oops
818 // in trash regions.
819 return r->is_trash() && is_concurrent_weak_root_in_progress();
820 }
821
822 void ShenandoahHeap::notify_soft_max_changed() {
823 if (_uncommit_thread != nullptr) {
824 _uncommit_thread->notify_soft_max_changed();
825 }
826 }
827
828 void ShenandoahHeap::notify_explicit_gc_requested() {
829 if (_uncommit_thread != nullptr) {
830 _uncommit_thread->notify_explicit_gc_requested();
831 }
832 }
833
834 bool ShenandoahHeap::check_soft_max_changed() {
835 size_t new_soft_max = AtomicAccess::load(&SoftMaxHeapSize);
836 size_t old_soft_max = soft_max_capacity();
837 if (new_soft_max != old_soft_max) {
838 new_soft_max = clamp(new_soft_max, min_capacity(), max_capacity());
839 if (new_soft_max != old_soft_max) {
840 log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s",
841 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
842 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
843 );
844 set_soft_max_capacity(new_soft_max);
845 return true;
846 }
847 }
848 return false;
849 }
850
851 void ShenandoahHeap::notify_heap_changed() {
852 // Update monitoring counters when we took a new region. This amortizes the
853 // update costs on slow path.
854 monitoring_support()->notify_heap_changed();
855 _heap_changed.try_set();
856 }
857
858 void ShenandoahHeap::start_idle_span() {
859 heuristics()->start_idle_span();
860 }
861
862 void ShenandoahHeap::set_forced_counters_update(bool value) {
863 monitoring_support()->set_forced_counters_update(value);
864 }
865
866 void ShenandoahHeap::handle_force_counters_update() {
867 monitoring_support()->handle_force_counters_update();
868 }
869
870 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
871 // New object should fit the GCLAB size
872 size_t min_size = MAX2(size, PLAB::min_size());
873
874 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
875 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
876
877 new_size = MIN2(new_size, PLAB::max_size());
878 new_size = MAX2(new_size, PLAB::min_size());
879
880 // Record new heuristic value even if we take any shortcut. This captures
881 // the case when moderately-sized objects always take a shortcut. At some point,
882 // heuristics should catch up with them.
883 log_debug(gc, free)("Set new GCLAB size: %zu", new_size);
884 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
885
886 if (new_size < size) {
887 // New size still does not fit the object. Fall back to shared allocation.
888 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
889 log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size);
890 return nullptr;
891 }
892
893 // Retire current GCLAB, and allocate a new one.
894 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
895 gclab->retire();
896
897 size_t actual_size = 0;
898 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
899 if (gclab_buf == nullptr) {
900 return nullptr;
901 }
902
903 assert (size <= actual_size, "allocation should fit");
904
905 // ...and clear or zap just allocated TLAB, if needed.
906 if (ZeroTLAB) {
907 Copy::zero_to_words(gclab_buf, actual_size);
908 } else if (ZapTLAB) {
909 // Skip mangling the space corresponding to the object header to
910 // ensure that the returned space is not considered parsable by
911 // any concurrent GC thread.
912 size_t hdr_size = oopDesc::header_size();
913 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
914 }
915 gclab->set_buf(gclab_buf, actual_size);
916 return gclab->allocate(size);
917 }
918
919 // Called from stubs in JIT code or interpreter
920 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
921 size_t requested_size,
922 size_t* actual_size) {
923 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
924 HeapWord* res = allocate_memory(req);
925 if (res != nullptr) {
926 *actual_size = req.actual_size();
927 } else {
928 *actual_size = 0;
929 }
930 return res;
931 }
932
933 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
934 size_t word_size,
935 size_t* actual_size) {
936 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
937 HeapWord* res = allocate_memory(req);
938 if (res != nullptr) {
939 *actual_size = req.actual_size();
940 } else {
941 *actual_size = 0;
942 }
943 return res;
944 }
945
946 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
947 bool in_new_region = false;
948 HeapWord* result = nullptr;
949
950 if (req.is_mutator_alloc()) {
951
952 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
953 result = allocate_memory_work(req, in_new_region);
954 }
955
956 // Check that gc overhead is not exceeded.
957 //
958 // Shenandoah will grind along for quite a while allocating one
959 // object at a time using shared (non-tlab) allocations. This check
960 // is testing that the GC overhead limit has not been exceeded.
961 // This will notify the collector to start a cycle, but will raise
962 // an OOME to the mutator if the last Full GCs have not made progress.
963 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
964 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
965 control_thread()->handle_alloc_failure(req, false);
966 req.set_actual_size(0);
967 return nullptr;
968 }
969
970 if (result == nullptr) {
971 // Block until control thread reacted, then retry allocation.
972 //
973 // It might happen that one of the threads requesting allocation would unblock
974 // way later after GC happened, only to fail the second allocation, because
975 // other threads have already depleted the free storage. In this case, a better
976 // strategy is to try again, until at least one full GC has completed.
977 //
978 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
979 // a) We experienced a GC that had good progress, or
980 // b) We experienced at least one Full GC (whether or not it had good progress)
981
982 const size_t original_count = shenandoah_policy()->full_gc_count();
983 while (result == nullptr && should_retry_allocation(original_count)) {
984 control_thread()->handle_alloc_failure(req, true);
985 result = allocate_memory_work(req, in_new_region);
986 }
987 if (result != nullptr) {
988 // If our allocation request has been satisfied after it initially failed, we count this as good gc progress
989 notify_gc_progress();
990 }
991 if (log_develop_is_enabled(Debug, gc, alloc)) {
992 ResourceMark rm;
993 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu"
994 ", Original: %zu, Latest: %zu",
995 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
996 original_count, get_gc_no_progress_count());
997 }
998 }
999 } else {
1000 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
1001 result = allocate_memory_work(req, in_new_region);
1002 // Do not call handle_alloc_failure() here, because we cannot block.
1003 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1004 }
1005
1006 if (in_new_region) {
1007 notify_heap_changed();
1008 }
1009
1010 if (result == nullptr) {
1011 req.set_actual_size(0);
1012 }
1013
1014 if (result != nullptr) {
1015 size_t requested = req.size();
1016 size_t actual = req.actual_size();
1017
1018 assert (req.is_lab_alloc() || (requested == actual),
1019 "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu",
1020 req.type_string(), requested, actual);
1021 }
1022
1023 return result;
1024 }
1025
1026 inline bool ShenandoahHeap::should_retry_allocation(size_t original_full_gc_count) const {
1027 return shenandoah_policy()->full_gc_count() == original_full_gc_count
1028 && !shenandoah_policy()->is_at_shutdown();
1029 }
1030
1031 HeapWord* ShenandoahHeap::allocate_memory_work(ShenandoahAllocRequest& req, bool& in_new_region) {
1032 // Reserve the promotion budget up front so it is enforced atomically without the heap lock.
1033 // If the reserve is exhausted, deny the promotion rather than overshoot it; the reservation
1034 // is refunded below if the allocation itself fails.
1035 if (req.is_promotion() && !old_generation()->try_expend_promoted(req.size() << LogHeapWordSize)) {
1036 return nullptr;
1037 }
1038
1039 HeapWord* result = _allocator->allocate(req, in_new_region);
1040
1041 if (result != nullptr) {
1042 if (req.is_mutator_alloc()) {
1043 _alloc_rate.allocated((req.actual_size() + req.waste()) * HeapWordSize);
1044 }
1045
1046 if (req.is_old()) {
1047 if (req.is_lab_alloc()) {
1048 old_generation()->configure_plab_for_current_thread(req);
1049 } else if (req.is_promotion()) {
1050 log_debug(gc, plab)("Expend shared promotion of %zu bytes", req.actual_size() * HeapWordSize);
1051 }
1052 }
1053 } else if (req.is_promotion()) {
1054 // Allocation failed, so refund the promotion budget reserved above.
1055 old_generation()->unexpend_promoted(req.size() << LogHeapWordSize);
1056 }
1057 return result;
1058 }
1059
1060 HeapWord* ShenandoahHeap::mem_allocate(size_t size) {
1061 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1062 return allocate_memory(req);
1063 }
1064
1065 oop ShenandoahHeap::array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS) {
1066 ShenandoahObjArrayAllocator allocator(klass, size, length, do_zero, THREAD);
1067 return allocator.allocate();
1068 }
1069
1070 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1071 size_t size,
1072 Metaspace::MetadataType mdtype) {
1073 MetaWord* result;
1074
1075 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1076 ShenandoahHeuristics* h = global_generation()->heuristics();
1077 if (h->can_unload_classes()) {
1078 h->record_metaspace_oom();
1079 }
1080
1081 // Expand and retry allocation
1082 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1083 if (result != nullptr) {
1084 return result;
1085 }
1086
1087 // Start full GC
1088 collect(GCCause::_metadata_GC_clear_soft_refs);
1089
1090 // Retry allocation
1091 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1092 if (result != nullptr) {
1093 return result;
1094 }
1095
1096 // Expand and retry allocation
1097 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1098 if (result != nullptr) {
1099 return result;
1100 }
1101
1102 // Out of memory
1103 return nullptr;
1104 }
1105
1106 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1107 private:
1108 ShenandoahHeap* const _heap;
1109 Thread* const _thread;
1110 public:
1111 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1112 _heap(heap), _thread(Thread::current()) {}
1113
1114 void do_object(oop p) {
1115 shenandoah_assert_marked(nullptr, p);
1116 if (!p->is_forwarded()) {
1117 _heap->evacuate_object(p, _thread);
1118 }
1119 }
1120 };
1121
1122 class ShenandoahEvacuationTask : public WorkerTask {
1123 private:
1124 ShenandoahHeap* const _sh;
1125 ShenandoahCollectionSet* const _cs;
1126 bool _concurrent;
1127 public:
1128 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1129 ShenandoahCollectionSet* cs,
1130 bool concurrent) :
1131 WorkerTask("Shenandoah Evacuation"),
1132 _sh(sh),
1133 _cs(cs),
1134 _concurrent(concurrent)
1135 {}
1136
1137 void work(uint worker_id) {
1138 if (_concurrent) {
1139 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_evac, ShenandoahPhaseTimings::Work, worker_id, true);
1140 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1141 SuspendibleThreadSetJoiner stsj;
1142 do_work();
1143 } else {
1144 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_evac, ShenandoahPhaseTimings::Work, worker_id, true);
1145 ShenandoahParallelWorkerSession worker_session(worker_id);
1146 do_work();
1147 }
1148 }
1149
1150 private:
1151 void do_work() {
1152 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1153 ShenandoahHeapRegion* r;
1154 while ((r =_cs->claim_next()) != nullptr) {
1155 assert(r->has_live(), "Region %zu should have been reclaimed early", r->index());
1156 _sh->marked_object_iterate(r, &cl);
1157
1158 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1159 break;
1160 }
1161 }
1162 }
1163 };
1164
1165 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1166 private:
1167 bool const _resize;
1168 public:
1169 explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1170 void do_thread(Thread* thread) override {
1171 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1172 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1173 gclab->retire();
1174 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1175 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1176 }
1177
1178 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1179 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1180 assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1181
1182 // There are two reasons to retire all plabs between old-gen evacuation passes.
1183 // 1. We need to make the plab memory parsable by remembered-set scanning.
1184 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1185 shenandoah_plab->retire();
1186
1187 // Re-enable promotions for the next evacuation phase.
1188 shenandoah_plab->enable_promotions();
1189
1190 // Reset the fill size for next evacuation phase.
1191 if (_resize && shenandoah_plab->desired_size() > 0) {
1192 shenandoah_plab->set_desired_size(0);
1193 }
1194 }
1195 }
1196 };
1197
1198 class ShenandoahGCStatePropagatorHandshakeClosure : public HandshakeClosure {
1199 public:
1200 explicit ShenandoahGCStatePropagatorHandshakeClosure(char gc_state) :
1201 HandshakeClosure("Shenandoah GC State Change"),
1202 _gc_state(gc_state) {}
1203
1204 void do_thread(Thread* thread) override {
1205 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state);
1206 }
1207 private:
1208 char _gc_state;
1209 };
1210
1211 class ShenandoahPrepareForUpdateRefsHandshakeClosure : public HandshakeClosure {
1212 public:
1213 explicit ShenandoahPrepareForUpdateRefsHandshakeClosure(char gc_state) :
1214 HandshakeClosure("Shenandoah Prepare for Update Refs"),
1215 _retire(ResizeTLAB), _propagator(gc_state) {}
1216
1217 void do_thread(Thread* thread) override {
1218 _propagator.do_thread(thread);
1219 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) {
1220 _retire.do_thread(thread);
1221 }
1222 }
1223 private:
1224 ShenandoahRetireGCLABClosure _retire;
1225 ShenandoahGCStatePropagatorHandshakeClosure _propagator;
1226 };
1227
1228 void ShenandoahHeap::evacuate_collection_set(ShenandoahGeneration* generation, bool concurrent) {
1229 assert(generation->is_global(), "Only global generation expected here");
1230 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1231 workers()->run_task(&task);
1232 }
1233
1234 class ShenandoahCompleteStackWatermarkHandshakeClosure : public HandshakeClosure {
1235 public:
1236 ShenandoahCompleteStackWatermarkHandshakeClosure() : HandshakeClosure("Shenandoah Complete stacks handshake") {}
1237 void do_thread(Thread* thread) override {
1238 if (thread->is_Java_thread()) {
1239 JavaThread* jt = JavaThread::cast(thread);
1240 StackWatermarkSet::finish_processing(jt, nullptr, StackWatermarkKind::gc);
1241 }
1242 }
1243 };
1244
1245 void ShenandoahHeap::concurrent_prepare_for_update_refs() {
1246 // The stack watermarks are active since op_final_roots().
1247 // Make sure the current stack watermark machinery has completed before we drop evac flags.
1248 // Otherwise the stack processing on stack unwinding may enter evac closure concurrently.
1249 ShenandoahCompleteStackWatermarkHandshakeClosure cl;
1250 Handshake::execute(&cl);
1251
1252 {
1253 // Java threads take this lock while they are being attached and added to the list of threads.
1254 // If another thread holds this lock before we update the gc state, it will receive a stale
1255 // gc state, but they will have been added to the list of java threads and so will be corrected
1256 // by the following handshake.
1257 MutexLocker lock(Threads_lock);
1258
1259 // A cancellation at this point means the degenerated cycle must resume from update-refs.
1260 set_gc_state_concurrent(EVACUATION, false);
1261 set_gc_state_concurrent(UPDATE_REFS, true);
1262 }
1263
1264 // This will propagate the gc state and retire gclabs and plabs for threads that require it.
1265 ShenandoahPrepareForUpdateRefsHandshakeClosure prepare_for_update_refs(_gc_state.raw_value());
1266
1267 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately.
1268 Threads::non_java_threads_do(&prepare_for_update_refs);
1269
1270 // Now retire gclabs and plabs and propagate gc_state for mutator threads
1271 Handshake::execute(&prepare_for_update_refs);
1272
1273 _update_refs_iterator.reset();
1274 }
1275
1276 void ShenandoahHeap::op_final_roots() {
1277 #ifdef ASSERT
1278 // Check if stack watermark machinery is in safe state:
1279 // 1. With evac-in-progress, we are about to supersede evac processing with new epoch.
1280 // op_thread_roots() should have completed the stack watermark processing before
1281 // we reach here.
1282 // 2. Without evac-in-progress, we are in abbreviated cycle, and we are switching
1283 // to a new epoch that *also* does not change any oops, which is safe.
1284 if (is_evacuation_in_progress()) {
1285 for (JavaThreadIteratorWithHandle jtiwh; JavaThread* jt = jtiwh.next();) {
1286 StackWatermark* sw = StackWatermarkSet::get(jt, StackWatermarkKind::gc);
1287 assert(sw == nullptr || sw->processing_completed(),
1288 "Cannot turn off weak roots before stack watermark processing is complete");
1289 }
1290 }
1291 #endif
1292
1293 set_gc_state_at_safepoint(WEAK_ROOTS, false);
1294
1295 // Arm the nmethods to change the barriers.
1296 CodeCache::arm_all_nmethods();
1297
1298 {
1299 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_roots_propagate_gc_state);
1300 propagate_gc_state_to_all_threads();
1301 }
1302 }
1303
1304 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1305 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1306
1307 ShenandoahHeapRegion* r = heap_region_containing(p);
1308 assert(!r->is_humongous(), "never evacuate humongous objects");
1309
1310 ShenandoahAffiliation target_gen = r->affiliation();
1311 return try_evacuate_object(p, thread, r, target_gen);
1312 }
1313
1314 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1315 ShenandoahAffiliation target_gen) {
1316 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1317 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1318 bool alloc_from_lab = true;
1319 HeapWord* copy = nullptr;
1320 size_t size = ShenandoahForwarding::size(p);
1321
1322 #ifdef ASSERT
1323 if (ShenandoahOOMDuringEvacALot &&
1324 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1325 copy = nullptr;
1326 } else {
1327 #endif
1328 if (UseTLAB) {
1329 copy = allocate_from_gclab(thread, size);
1330 }
1331 if (copy == nullptr) {
1332 // If we failed to allocate in LAB, we'll try a shared allocation.
1333 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1334 copy = allocate_memory(req);
1335 alloc_from_lab = false;
1336 }
1337 #ifdef ASSERT
1338 }
1339 #endif
1340
1341 if (copy == nullptr) {
1342 control_thread()->handle_alloc_failure_evac(size);
1343
1344 // Install the self-forwarded bit on p so other evacuators/LRBs see
1345 // the object as "already handled, do not try to evacuate". The CAS
1346 // may fail if another thread concurrently installed a real forwardee
1347 // (they succeeded where we failed) or self-forwarded first.
1348 markWord old_mark = p->mark();
1349 if (old_mark.is_forwarded()) {
1350 return ShenandoahForwarding::get_forwardee(p);
1351 }
1352 oop winner = ShenandoahForwarding::try_forward_to_self(p, old_mark);
1353 if (winner == nullptr) {
1354 // We own the self-forwarding. Flag the region so the degen/full GC
1355 // entry drain knows to scan it for self_fwd bits to clear.
1356 from_region->set_has_self_forwards();
1357 return p;
1358 }
1359 return winner;
1360 }
1361
1362 if (ShenandoahEvacTracking) {
1363 evac_tracker()->begin_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1364 }
1365
1366 // Copy the object:
1367 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1368
1369 oop copy_val = cast_to_oop(copy);
1370
1371 // Relativize stack chunks before publishing the copy. After the forwarding CAS,
1372 // mutators can see the copy and thaw it via the fast path if flags == 0. We must
1373 // relativize derived pointers and set gc_mode before that happens. Skip if the
1374 // copy's mark word is already a forwarding pointer (another thread won the race
1375 // and overwrote the original's header before we copied it).
1376 if (!ShenandoahForwarding::is_forwarded(copy_val)) {
1377 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1378 }
1379
1380 // Try to install the new forwarding pointer.
1381 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1382 if (result == copy_val) {
1383 // Successfully evacuated. Our copy is now the public one!
1384 shenandoah_assert_correct(nullptr, copy_val);
1385 if (ShenandoahEvacTracking) {
1386 evac_tracker()->end_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1387 }
1388 return copy_val;
1389 } else {
1390 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1391 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1392 // But if it happens to contain references to evacuated regions, those references would
1393 // not get updated for this stale copy during this cycle, and we will crash while scanning
1394 // it the next cycle.
1395 if (alloc_from_lab) {
1396 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1397 // object will overwrite this stale copy, or the filler object on LAB retirement will
1398 // do this.
1399 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1400 } else {
1401 // For non-LAB allocations, we have no way to retract the allocation, and
1402 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1403 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1404 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1405 fill_with_object(copy, size);
1406 shenandoah_assert_correct(nullptr, copy_val);
1407 // For non-LAB allocations, the object has already been registered
1408 }
1409 shenandoah_assert_correct(nullptr, result);
1410 return result;
1411 }
1412 }
1413
1414 // Clear the self_fwd bit on a live cset object, if set. Runs at a safepoint,
1415 // so a plain store is sufficient — no concurrent writers to the mark word.
1416 class ShenandoahUnSelfForwardObjectClosure : public ObjectClosure {
1417 public:
1418 void do_object(oop obj) override {
1419 markWord m = obj->mark();
1420 if (m.is_self_forwarded()) {
1421 obj->set_mark(m.unset_self_forwarded());
1422 }
1423 }
1424 };
1425
1426 // Parallel task over flagged cset regions. Iterates the live objects via the
1427 // mark bitmap (skipping evacuated and never-marked memory), clears self_fwd
1428 // bits, and resets the region flag once done.
1429 class ShenandoahUnSelfForwardTask : public WorkerTask {
1430 private:
1431 ShenandoahHeap* const _heap;
1432 ShenandoahCollectionSet* const _cs;
1433
1434 public:
1435 ShenandoahUnSelfForwardTask(ShenandoahHeap* heap, ShenandoahCollectionSet* cs) :
1436 WorkerTask("Shenandoah Un-Self-Forward"),
1437 _heap(heap),
1438 _cs(cs) {}
1439
1440 void work(uint worker_id) override {
1441 ShenandoahParallelWorkerSession worker_session(worker_id);
1442 ShenandoahUnSelfForwardObjectClosure cl;
1443 ShenandoahHeapRegion* r;
1444 while ((r = _cs->claim_next()) != nullptr) {
1445 if (r->has_self_forwards()) {
1446 _heap->marked_object_iterate(r, &cl);
1447 r->clear_has_self_forwards();
1448 }
1449 }
1450 }
1451 };
1452
1453 void ShenandoahHeap::un_self_forward_cset_regions() {
1454 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1455 ShenandoahCollectionSet* cs = collection_set();
1456 if (cs == nullptr || cs->is_empty()) {
1457 return;
1458 }
1459 cs->clear_current_index();
1460 ShenandoahUnSelfForwardTask task(this, cs);
1461 workers()->run_task(&task);
1462 DEBUG_ONLY(assert_no_self_forwards());
1463 }
1464
1465 #ifdef ASSERT
1466 void ShenandoahHeap::assert_no_self_forwards() const {
1467 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1468 ShenandoahCollectionSet* cs = collection_set();
1469 if (cs == nullptr) return;
1470 cs->clear_current_index();
1471 ShenandoahHeapRegion* r;
1472 while ((r = cs->next()) != nullptr) {
1473 assert(!r->has_self_forwards(), "region still flagged after drain");
1474 }
1475 cs->clear_current_index();
1476 }
1477 #endif
1478
1479 void ShenandoahHeap::trash_cset_regions() {
1480 ShenandoahHeapLocker locker(lock());
1481
1482 ShenandoahCollectionSet* set = collection_set();
1483 ShenandoahHeapRegion* r;
1484 set->clear_current_index();
1485 while ((r = set->next()) != nullptr) {
1486 r->make_trash();
1487 }
1488 collection_set()->clear();
1489 }
1490
1491 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1492 st->print_cr("Heap Regions:");
1493 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1494 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1495 st->print_cr("A=age, BTE=bottom/top/end, TAMS=top-at-mark-start, UWM=update watermark, U=used");
1496 st->print_cr("T=TLAB allocs, G=GCLAB allocs, S=shared allocs, L=live data");
1497 st->print_cr("CP=critical pins");
1498
1499 for (size_t i = 0; i < num_regions(); i++) {
1500 get_region(i)->print_on(st);
1501 }
1502 }
1503
1504 void ShenandoahHeap::process_gc_stats() const {
1505 // Commit worker statistics to cycle data
1506 phase_timings()->flush_par_workers_to_cycle();
1507
1508 // Print GC stats for current cycle
1509 LogTarget(Info, gc, stats) lt;
1510 if (lt.is_enabled()) {
1511 ResourceMark rm;
1512 LogStream ls(lt);
1513 phase_timings()->print_cycle_on(&ls);
1514 if (ShenandoahEvacTracking) {
1515 ShenandoahCycleStats evac_stats = evac_tracker()->flush_cycle_to_global();
1516 evac_tracker()->print_evacuations_on(&ls, &evac_stats.workers,
1517 &evac_stats.mutators);
1518 }
1519 }
1520
1521 // Commit statistics to globals
1522 phase_timings()->flush_cycle_to_global();
1523 }
1524
1525 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) const {
1526 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1527 assert(!start->has_live(), "liveness must be zero");
1528
1529 // Do not try to get the size of this humongous object. STW collections will
1530 // have already unloaded classes, so an unmarked object may have a bad klass pointer.
1531 ShenandoahHeapRegion* region = start;
1532 size_t index = region->index();
1533 do {
1534 assert(region->is_humongous(), "Expect correct humongous start or continuation");
1535 assert(!region->is_cset(), "Humongous region should not be in collection set");
1536 region->make_trash_immediate();
1537 region = get_region(++index);
1538 } while (region != nullptr && region->is_humongous_continuation());
1539
1540 // Return number of regions trashed
1541 return index - start->index();
1542 }
1543
1544 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1545 public:
1546 ShenandoahCheckCleanGCLABClosure() {}
1547 void do_thread(Thread* thread) {
1548 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1549 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1550 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1551
1552 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1553 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1554 assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1555 assert(shenandoah_plab->plab()->words_remaining() == 0, "PLAB should not need retirement");
1556 }
1557 }
1558 };
1559
1560 void ShenandoahHeap::labs_make_parsable() {
1561 assert(UseTLAB, "Only call with UseTLAB");
1562
1563 ShenandoahRetireGCLABClosure cl(false);
1564
1565 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1566 ThreadLocalAllocBuffer& tlab = t->tlab();
1567 tlab.make_parsable();
1568 if (ZeroTLAB) {
1569 t->retire_tlab();
1570 }
1571 cl.do_thread(t);
1572 }
1573
1574 workers()->threads_do(&cl);
1575
1576 if (safepoint_workers() != nullptr) {
1577 safepoint_workers()->threads_do(&cl);
1578 }
1579 }
1580
1581 void ShenandoahHeap::tlabs_retire(bool resize) {
1582 assert(UseTLAB, "Only call with UseTLAB");
1583 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1584
1585 ThreadLocalAllocStats stats;
1586
1587 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1588 t->retire_tlab(&stats);
1589 if (resize) {
1590 t->tlab().resize();
1591 }
1592 }
1593
1594 stats.publish();
1595
1596 #ifdef ASSERT
1597 ShenandoahCheckCleanGCLABClosure cl;
1598 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1599 cl.do_thread(t);
1600 }
1601 workers()->threads_do(&cl);
1602 #endif
1603 }
1604
1605 void ShenandoahHeap::gclabs_retire(bool resize) {
1606 assert(UseTLAB, "Only call with UseTLAB");
1607 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1608
1609 ShenandoahRetireGCLABClosure cl(resize);
1610 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1611 cl.do_thread(t);
1612 }
1613
1614 workers()->threads_do(&cl);
1615
1616 if (safepoint_workers() != nullptr) {
1617 safepoint_workers()->threads_do(&cl);
1618 }
1619 }
1620
1621 // Returns size in bytes
1622 size_t ShenandoahHeap::unsafe_max_tlab_alloc() const {
1623 // Return the max allowed size, and let the allocation path
1624 // figure out the safe size for current allocation.
1625 return ShenandoahHeapRegion::max_tlab_size_bytes();
1626 }
1627
1628 size_t ShenandoahHeap::max_tlab_size() const {
1629 // Returns size in words
1630 return ShenandoahHeapRegion::max_tlab_size_words();
1631 }
1632
1633 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) {
1634 // These requests are ignored because we can't easily have Shenandoah jump into
1635 // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent
1636 // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly
1637 // on the VM thread, but this would confuse the control thread mightily and doesn't
1638 // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a
1639 // concurrent cycle in the prologue of the heap inspect/dump operation (see VM_HeapDumper::doit_prologue).
1640 // This is how other concurrent collectors in the JVM handle this scenario as well.
1641 assert(Thread::current()->is_VM_thread(), "Should be the VM thread");
1642 guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause");
1643 }
1644
1645 void ShenandoahHeap::collect(GCCause::Cause cause) {
1646 control_thread()->request_gc(cause);
1647 }
1648
1649 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1650 // This method is only called by `CollectedHeap::collect_as_vm_thread`, which we have
1651 // overridden to do nothing. See the comment there for an explanation of how heap inspections
1652 // work for Shenandoah.
1653 ShouldNotReachHere();
1654 }
1655
1656 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1657 ShenandoahHeapRegion* r = heap_region_containing(addr);
1658 if (r != nullptr) {
1659 return r->block_start(addr);
1660 }
1661 return nullptr;
1662 }
1663
1664 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1665 ShenandoahHeapRegion* r = heap_region_containing(addr);
1666 return r->block_is_obj(addr);
1667 }
1668
1669 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1670 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1671 }
1672
1673 void ShenandoahHeap::prepare_for_verify() {
1674 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1675 labs_make_parsable();
1676 }
1677 }
1678
1679 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1680 if (_shenandoah_policy->is_at_shutdown()) {
1681 return;
1682 }
1683
1684 if (_control_thread != nullptr) {
1685 tcl->do_thread(_control_thread);
1686 }
1687
1688 if (_uncommit_thread != nullptr) {
1689 tcl->do_thread(_uncommit_thread);
1690 }
1691
1692 workers()->threads_do(tcl);
1693 if (_safepoint_workers != nullptr) {
1694 _safepoint_workers->threads_do(tcl);
1695 }
1696 }
1697
1698 void ShenandoahHeap::print_tracing_info() const {
1699 LogTarget(Info, gc, stats) lt;
1700 if (lt.is_enabled()) {
1701 ResourceMark rm;
1702 LogStream ls(lt);
1703
1704 if (ShenandoahEvacTracking) {
1705 evac_tracker()->print_global_on(&ls);
1706 ls.cr();
1707 ls.cr();
1708 }
1709
1710 phase_timings()->print_global_on(&ls);
1711
1712 ls.cr();
1713 ls.cr();
1714
1715 shenandoah_policy()->print_gc_stats(&ls);
1716
1717 ls.cr();
1718 ls.cr();
1719 }
1720 }
1721
1722 // Active generation may only be set by the VM thread at a safepoint.
1723 void ShenandoahHeap::set_active_generation(ShenandoahGeneration* generation) {
1724 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1725 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1726 _active_generation = generation;
1727 }
1728
1729 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation,
1730 bool is_degenerated, bool is_out_of_cycle) {
1731 shenandoah_policy()->record_collection_cause(cause);
1732
1733 const GCCause::Cause current = gc_cause();
1734 assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s",
1735 GCCause::to_string(current), GCCause::to_string(cause));
1736
1737 set_gc_cause(cause);
1738
1739 if (is_degenerated) {
1740 generation->heuristics()->record_degenerated_cycle_start(is_out_of_cycle);
1741 } else {
1742 generation->heuristics()->record_cycle_start();
1743 }
1744 }
1745
1746 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1747 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1748
1749 generation->heuristics()->record_cycle_end();
1750 if (mode()->is_generational() && generation->is_global()) {
1751 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1752 young_generation()->heuristics()->record_cycle_end();
1753 old_generation()->heuristics()->record_cycle_end();
1754 }
1755
1756 set_gc_cause(GCCause::_no_gc);
1757 }
1758
1759 void ShenandoahHeap::verify(VerifyOption vo) {
1760 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1761 if (ShenandoahVerify) {
1762 verifier()->verify_generic(active_generation(), vo);
1763 } else {
1764 // TODO: Consider allocating verification bitmaps on demand,
1765 // and turn this on unconditionally.
1766 }
1767 }
1768 }
1769 size_t ShenandoahHeap::tlab_capacity() const {
1770 return _free_set->capacity_not_holding_lock();
1771 }
1772
1773 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1774 private:
1775 MarkBitMap* _bitmap;
1776 ShenandoahScanObjectStack* _oop_stack;
1777 ShenandoahHeap* const _heap;
1778 ShenandoahMarkingContext* const _marking_context;
1779
1780 template <class T>
1781 void do_oop_work(T* p) {
1782 T o = RawAccess<>::oop_load(p);
1783 if (!CompressedOops::is_null(o)) {
1784 oop obj = CompressedOops::decode_not_null(o);
1785 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1786 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1787 return;
1788 }
1789 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1790
1791 assert(oopDesc::is_oop(obj), "must be a valid oop");
1792 if (!_bitmap->is_marked(obj)) {
1793 _bitmap->mark(obj);
1794 _oop_stack->push(obj);
1795 }
1796 }
1797 }
1798 public:
1799 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1800 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1801 _marking_context(_heap->marking_context()) {}
1802 void do_oop(oop* p) { do_oop_work(p); }
1803 void do_oop(narrowOop* p) { do_oop_work(p); }
1804 };
1805
1806 /*
1807 * This is public API, used in preparation of object_iterate().
1808 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1809 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1810 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1811 */
1812 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1813 // No-op.
1814 }
1815
1816 /*
1817 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1818 *
1819 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1820 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1821 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1822 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1823 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1824 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1825 * wiped the bitmap in preparation for next marking).
1826 *
1827 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1828 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1829 * is allowed to report dead objects, but is not required to do so.
1830 */
1831 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1832 // Reset bitmap
1833 if (!prepare_aux_bitmap_for_iteration())
1834 return;
1835
1836 ShenandoahScanObjectStack oop_stack;
1837 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1838 // Seed the stack with root scan
1839 scan_roots_for_iteration(&oop_stack, &oops);
1840
1841 // Work through the oop stack to traverse heap
1842 while (! oop_stack.is_empty()) {
1843 oop obj = oop_stack.pop();
1844 assert(oopDesc::is_oop(obj), "must be a valid oop");
1845 cl->do_object(obj);
1846 obj->oop_iterate(&oops);
1847 }
1848
1849 assert(oop_stack.is_empty(), "should be empty");
1850 // Reclaim bitmap
1851 reclaim_aux_bitmap_for_iteration();
1852 }
1853
1854 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1855 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1856 if (!_aux_bitmap_region_special) {
1857 bool success = os::commit_memory((char *) _aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false);
1858 if (!success) {
1859 log_warning(gc)("Auxiliary marking bitmap commit failed: " PTR_FORMAT " (%zu bytes)",
1860 p2i(_aux_bitmap_region.start()), _aux_bitmap_region.byte_size());
1861 return false;
1862 }
1863 }
1864 _aux_bit_map.clear();
1865 return true;
1866 }
1867
1868 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1869 // Process GC roots according to current GC cycle
1870 // This populates the work stack with initial objects
1871 // It is important to relinquish the associated locks before diving
1872 // into heap dumper
1873 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1874 ShenandoahHeapIterationRootScanner rp(n_workers);
1875 rp.roots_do(oops);
1876 }
1877
1878 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1879 if (!_aux_bitmap_region_special) {
1880 os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size());
1881 }
1882 }
1883
1884 // Closure for parallelly iterate objects
1885 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1886 private:
1887 MarkBitMap* _bitmap;
1888 ShenandoahObjToScanQueue* _queue;
1889 ShenandoahHeap* const _heap;
1890 ShenandoahMarkingContext* const _marking_context;
1891
1892 template <class T>
1893 void do_oop_work(T* p) {
1894 T o = RawAccess<>::oop_load(p);
1895 if (!CompressedOops::is_null(o)) {
1896 oop obj = CompressedOops::decode_not_null(o);
1897 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1898 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1899 return;
1900 }
1901 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1902
1903 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1904 if (_bitmap->par_mark(obj)) {
1905 _queue->push(ShenandoahMarkTask(obj));
1906 }
1907 }
1908 }
1909 public:
1910 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1911 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1912 _marking_context(_heap->marking_context()) {}
1913 void do_oop(oop* p) { do_oop_work(p); }
1914 void do_oop(narrowOop* p) { do_oop_work(p); }
1915 };
1916
1917 // Object iterator for parallel heap iteraion.
1918 // The root scanning phase happenes in construction as a preparation of
1919 // parallel marking queues.
1920 // Every worker processes it's own marking queue. work-stealing is used
1921 // to balance workload.
1922 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1923 private:
1924 uint _num_workers;
1925 bool _init_ready;
1926 MarkBitMap* _aux_bit_map;
1927 ShenandoahHeap* _heap;
1928 ShenandoahScanObjectStack _roots_stack; // global roots stack
1929 ShenandoahObjToScanQueueSet* _task_queues;
1930 public:
1931 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1932 _num_workers(num_workers),
1933 _init_ready(false),
1934 _aux_bit_map(bitmap),
1935 _heap(ShenandoahHeap::heap()) {
1936 // Initialize bitmap
1937 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1938 if (!_init_ready) {
1939 return;
1940 }
1941
1942 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1943 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1944
1945 _init_ready = prepare_worker_queues();
1946 }
1947
1948 ~ShenandoahParallelObjectIterator() {
1949 // Reclaim bitmap
1950 _heap->reclaim_aux_bitmap_for_iteration();
1951 // Reclaim queue for workers
1952 if (_task_queues!= nullptr) {
1953 for (uint i = 0; i < _num_workers; ++i) {
1954 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1955 if (q != nullptr) {
1956 delete q;
1957 _task_queues->register_queue(i, nullptr);
1958 }
1959 }
1960 delete _task_queues;
1961 _task_queues = nullptr;
1962 }
1963 }
1964
1965 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1966 if (_init_ready) {
1967 object_iterate_parallel(cl, worker_id, _task_queues);
1968 }
1969 }
1970
1971 private:
1972 // Divide global root_stack into worker queues
1973 bool prepare_worker_queues() {
1974 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1975 // Initialize queues for every workers
1976 for (uint i = 0; i < _num_workers; ++i) {
1977 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1978 _task_queues->register_queue(i, task_queue);
1979 }
1980 // Divide roots among the workers. Assume that object referencing distribution
1981 // is related with root kind, use round-robin to make every worker have same chance
1982 // to process every kind of roots
1983 size_t roots_num = _roots_stack.size();
1984 if (roots_num == 0) {
1985 // No work to do
1986 return false;
1987 }
1988
1989 for (uint j = 0; j < roots_num; j++) {
1990 uint stack_id = j % _num_workers;
1991 oop obj = _roots_stack.pop();
1992 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1993 }
1994 return true;
1995 }
1996
1997 void object_iterate_parallel(ObjectClosure* cl,
1998 uint worker_id,
1999 ShenandoahObjToScanQueueSet* queue_set) {
2000 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
2001 assert(queue_set != nullptr, "task queue must not be null");
2002
2003 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
2004 assert(q != nullptr, "object iterate queue must not be null");
2005
2006 ShenandoahMarkTask t;
2007 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
2008
2009 // Work through the queue to traverse heap.
2010 // Steal when there is no task in queue.
2011 while (q->pop(t) || queue_set->steal(worker_id, t)) {
2012 oop obj = t.obj();
2013 assert(oopDesc::is_oop(obj), "must be a valid oop");
2014 cl->do_object(obj);
2015 obj->oop_iterate(&oops);
2016 }
2017 assert(q->is_empty(), "should be empty");
2018 }
2019 };
2020
2021 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
2022 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
2023 }
2024
2025 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
2026 void ShenandoahHeap::keep_alive(oop obj) {
2027 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
2028 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
2029 }
2030 }
2031
2032 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2033 for (size_t i = 0; i < num_regions(); i++) {
2034 ShenandoahHeapRegion* current = get_region(i);
2035 blk->heap_region_do(current);
2036 }
2037 }
2038
2039 class ShenandoahHeapRegionIteratorTask : public WorkerTask {
2040 private:
2041 ShenandoahRegionIterator _regions;
2042 ShenandoahHeapRegionClosure* _closure;
2043
2044 public:
2045 ShenandoahHeapRegionIteratorTask(ShenandoahHeapRegionClosure* closure)
2046 : WorkerTask("Shenandoah Heap Region Iterator")
2047 , _closure(closure) {}
2048
2049 void work(uint worker_id) override {
2050 ShenandoahParallelWorkerSession worker_session(worker_id);
2051 ShenandoahHeapRegion* region = _regions.next();
2052 while (region != nullptr) {
2053 _closure->heap_region_do(region);
2054 region = _regions.next();
2055 }
2056 }
2057 };
2058
2059 class ShenandoahParallelHeapRegionTask : public WorkerTask {
2060 private:
2061 ShenandoahHeap* const _heap;
2062 ShenandoahHeapRegionClosure* const _blk;
2063 size_t const _stride;
2064
2065 shenandoah_padding(0);
2066 Atomic<size_t> _index;
2067 shenandoah_padding(1);
2068
2069 public:
2070 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
2071 WorkerTask("Shenandoah Parallel Region Operation"),
2072 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
2073
2074 void work(uint worker_id) {
2075 ShenandoahParallelWorkerSession worker_session(worker_id);
2076 size_t stride = _stride;
2077
2078 size_t max = _heap->num_regions();
2079 while (_index.load_relaxed() < max) {
2080 size_t cur = _index.fetch_then_add(stride, memory_order_relaxed);
2081 size_t start = cur;
2082 size_t end = MIN2(cur + stride, max);
2083 if (start >= max) break;
2084
2085 for (size_t i = cur; i < end; i++) {
2086 ShenandoahHeapRegion* current = _heap->get_region(i);
2087 _blk->heap_region_do(current);
2088 }
2089 }
2090 }
2091 };
2092
2093 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2094 assert(blk->is_thread_safe(), "Only thread-safe closures here");
2095 const uint active_workers = workers()->active_workers();
2096 const size_t n_regions = num_regions();
2097 size_t stride = blk->parallel_region_stride();
2098 if (stride == 0 && active_workers > 1) {
2099 // Automatically derive the stride to balance the work between threads
2100 // evenly. Do not try to split work if below the reasonable threshold.
2101 constexpr size_t threshold = 4096;
2102 stride = n_regions <= threshold ?
2103 threshold :
2104 (n_regions + active_workers - 1) / active_workers;
2105 }
2106
2107 if (n_regions > stride && active_workers > 1) {
2108 ShenandoahParallelHeapRegionTask task(blk, stride);
2109 workers()->run_task(&task);
2110 } else {
2111 heap_region_iterate(blk);
2112 }
2113 }
2114
2115 void ShenandoahHeap::heap_region_iterator(ShenandoahHeapRegionClosure* closure) const {
2116 ShenandoahHeapRegionIteratorTask task(closure);
2117 workers()->run_task(&task);
2118 }
2119
2120 class ShenandoahRendezvousHandshakeClosure : public HandshakeClosure {
2121 public:
2122 inline ShenandoahRendezvousHandshakeClosure(const char* name) : HandshakeClosure(name) {}
2123 inline void do_thread(Thread* thread) {}
2124 };
2125
2126 void ShenandoahHeap::rendezvous_threads(const char* name) {
2127 ShenandoahRendezvousHandshakeClosure cl(name);
2128 Handshake::execute(&cl);
2129 }
2130
2131 void ShenandoahHeap::recycle_trash() {
2132 free_set()->recycle_trash();
2133 }
2134
2135 void ShenandoahHeap::do_class_unloading() {
2136 _unloader.unload();
2137 if (mode()->is_generational()) {
2138 old_generation()->set_parsable(false);
2139 }
2140 }
2141
2142 void ShenandoahHeap::stw_weak_refs(ShenandoahGeneration* generation, bool full_gc) {
2143 // Weak refs processing
2144 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2145 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2146 ShenandoahTimingsTracker t(phase);
2147 ShenandoahGCWorkerPhase worker_phase(phase);
2148 generation->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2149 }
2150
2151 void ShenandoahHeap::prepare_update_heap_references() {
2152 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2153
2154 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2155 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2156 // for future GCLABs here.
2157 if (UseTLAB) {
2158 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2159 gclabs_retire(ResizeTLAB);
2160 }
2161
2162 _update_refs_iterator.reset();
2163 }
2164
2165 void ShenandoahHeap::propagate_gc_state_to_all_threads() {
2166 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2167 if (_gc_state_changed) {
2168 // If we are only marking old, we do not need to process young pointers
2169 ShenandoahBarrierSet::satb_mark_queue_set().set_filter_out_young(
2170 is_concurrent_old_mark_in_progress() && !is_concurrent_young_mark_in_progress()
2171 );
2172 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
2173 Threads::threads_do(&propagator);
2174 _gc_state_changed = false;
2175 }
2176 }
2177
2178 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) {
2179 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2180 _gc_state.set_cond(mask, value);
2181 _gc_state_changed = true;
2182 }
2183
2184 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) {
2185 // Holding the thread lock here assures that any thread created after we change the gc
2186 // state will have the correct state. It also prevents attaching threads from seeing
2187 // an inconsistent state. See ShenandoahBarrierSet::on_thread_attach for reference. Established
2188 // threads will use their thread local copy of the gc state (changed by a handshake, or on a
2189 // safepoint).
2190 assert(Threads_lock->is_locked(), "Must hold thread lock for concurrent gc state change");
2191 _gc_state.set_cond(mask, value);
2192 }
2193
2194 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2195 uint mask;
2196 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2197 if (!in_progress && is_concurrent_old_mark_in_progress()) {
2198 assert(mode()->is_generational(), "Only generational GC has old marking");
2199 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2200 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2201 mask = YOUNG_MARKING;
2202 } else {
2203 mask = MARKING | YOUNG_MARKING;
2204 }
2205 set_gc_state_at_safepoint(mask, in_progress);
2206 manage_satb_barrier(in_progress);
2207 }
2208
2209 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2210 #ifdef ASSERT
2211 // has_forwarded_objects() iff UPDATE_REFS or EVACUATION
2212 bool has_forwarded = has_forwarded_objects();
2213 bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION);
2214 bool evacuating = _gc_state.is_set(EVACUATION);
2215 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2216 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2217 #endif
2218 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2219 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2220 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2221 set_gc_state_at_safepoint(OLD_MARKING, in_progress);
2222 } else {
2223 set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress);
2224 }
2225 manage_satb_barrier(in_progress);
2226 }
2227
2228 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2229 return old_generation()->is_preparing_for_mark();
2230 }
2231
2232 void ShenandoahHeap::manage_satb_barrier(bool active) {
2233 if (is_concurrent_mark_in_progress()) {
2234 // Ignore request to deactivate barrier while concurrent mark is in progress.
2235 // Do not attempt to re-activate the barrier if it is already active.
2236 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2237 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2238 }
2239 } else {
2240 // No concurrent marking is in progress so honor request to deactivate,
2241 // but only if the barrier is already active.
2242 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2243 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2244 }
2245 }
2246 }
2247
2248 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2249 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2250 set_gc_state_at_safepoint(EVACUATION, in_progress);
2251 }
2252
2253 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2254 if (in_progress) {
2255 _concurrent_strong_root_in_progress.set();
2256 } else {
2257 _concurrent_strong_root_in_progress.unset();
2258 }
2259 }
2260
2261 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2262 set_gc_state_at_safepoint(WEAK_ROOTS, cond);
2263 }
2264
2265 GCTracer* ShenandoahHeap::tracer() {
2266 return shenandoah_policy()->tracer();
2267 }
2268
2269 size_t ShenandoahHeap::tlab_used() const {
2270 return _free_set->used_not_holding_lock();
2271 }
2272
2273 bool ShenandoahHeap::try_cancel_gc(GCCause::Cause cause) {
2274 while (true) {
2275 const GCCause::Cause prev = _cancelled_gc.get();
2276 if (prev != GCCause::_no_gc && prev != GCCause::_shenandoah_concurrent_gc && cause != GCCause::_shenandoah_stop_vm) {
2277 // Only when the gc has not been cancelled, or it has been cancelled to interrupt an old marking cycle
2278 // do we allow the new cancellation request to happen. We make an exception for stopping the VM.
2279 return false;
2280 }
2281
2282 if (_cancelled_gc.cmpxchg(cause, prev) == prev) {
2283 return true;
2284 }
2285 }
2286 }
2287
2288 void ShenandoahHeap::cancel_concurrent_mark() {
2289 if (mode()->is_generational()) {
2290 young_generation()->cancel_marking();
2291 old_generation()->cancel_marking();
2292 }
2293
2294 global_generation()->cancel_marking();
2295
2296 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2297 }
2298
2299 bool ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2300 if (try_cancel_gc(cause)) {
2301 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2302 log_info(gc,thread)("%s", msg.buffer());
2303 Events::log(Thread::current(), "%s", msg.buffer());
2304 _cancel_requested_time = os::elapsedTime();
2305 return true;
2306 }
2307 return false;
2308 }
2309
2310 uint ShenandoahHeap::max_workers() {
2311 return _max_workers;
2312 }
2313
2314 void ShenandoahHeap::stop() {
2315 // The shutdown sequence should be able to terminate when GC is running.
2316
2317 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2318 _shenandoah_policy->record_shutdown();
2319
2320 // Step 1. Stop reporting on gc thread cpu utilization
2321 mmu_tracker()->stop();
2322
2323 // Step 2. Stop decaying allocation rate.
2324 _alloc_rate_decay.disenroll();
2325
2326 // Step 3. Wait until GC worker exits normally (this will cancel any ongoing GC).
2327 control_thread()->stop();
2328
2329 // Step 4. Shutdown uncommit thread.
2330 if (_uncommit_thread != nullptr) {
2331 _uncommit_thread->stop();
2332 }
2333 }
2334
2335 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2336 if (!unload_classes()) return;
2337 ClassUnloadingContext ctx(_workers->active_workers(),
2338 true /* unregister_nmethods_during_purge */,
2339 false /* lock_nmethod_free_separately */);
2340
2341 // Unload classes and purge SystemDictionary.
2342 {
2343 ShenandoahPhaseTimings::Phase phase = full_gc ?
2344 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2345 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2346 ShenandoahIsAliveSelector is_alive;
2347 {
2348 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2349 ShenandoahGCPhase gc_phase(phase);
2350 ShenandoahGCWorkerPhase worker_phase(phase);
2351 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2352
2353 ShenandoahClassUnloadingTask unlink_task(phase, unloading_occurred);
2354 _workers->run_task(&unlink_task);
2355 }
2356 // Release unloaded nmethods's memory.
2357 ClassUnloadingContext::context()->purge_and_free_nmethods();
2358 }
2359
2360 {
2361 ShenandoahGCPhase phase(full_gc ?
2362 ShenandoahPhaseTimings::full_gc_purge_cldg :
2363 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2364 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2365 }
2366 // Resize and verify metaspace
2367 MetaspaceGC::compute_new_size();
2368
2369 if (mode()->is_generational()) {
2370 old_generation()->set_parsable(false);
2371 }
2372
2373 DEBUG_ONLY(MetaspaceUtils::verify();)
2374 }
2375
2376 // Weak roots are either pre-evacuated (final mark) or updated (final update refs),
2377 // so they should not have forwarded oops.
2378 // However, we do need to "null" dead oops in the roots, if can not be done
2379 // in concurrent cycles.
2380 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2381 uint num_workers = _workers->active_workers();
2382 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2383 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2384 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2385 ShenandoahGCPhase phase(timing_phase);
2386 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2387 // Cleanup weak roots
2388 if (has_forwarded_objects()) {
2389 ShenandoahForwardedIsAliveClosure is_alive;
2390 ShenandoahNonConcUpdateRefsClosure keep_alive;
2391 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2392 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2393 _workers->run_task(&cleaning_task);
2394 } else {
2395 ShenandoahIsAliveClosure is_alive;
2396 #ifdef ASSERT
2397 ShenandoahAssertNotForwardedClosure verify_cl;
2398 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2399 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2400 #else
2401 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2402 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2403 #endif
2404 _workers->run_task(&cleaning_task);
2405 }
2406 }
2407
2408 void ShenandoahHeap::parallel_cleaning(ShenandoahGeneration* generation, bool full_gc) {
2409 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2410 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2411 ShenandoahGCPhase phase(full_gc ?
2412 ShenandoahPhaseTimings::full_gc_purge :
2413 ShenandoahPhaseTimings::degen_gc_purge);
2414 stw_weak_refs(generation, full_gc);
2415 stw_process_weak_roots(full_gc);
2416 stw_unload_classes(full_gc);
2417 }
2418
2419 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2420 set_gc_state_at_safepoint(HAS_FORWARDED, cond);
2421 }
2422
2423 void ShenandoahHeap::set_unload_classes(bool uc) {
2424 _unload_classes.set_cond(uc);
2425 }
2426
2427 bool ShenandoahHeap::unload_classes() const {
2428 return _unload_classes.is_set();
2429 }
2430
2431 address ShenandoahHeap::in_cset_fast_test_addr() {
2432 ShenandoahHeap* heap = ShenandoahHeap::heap();
2433 assert(heap->collection_set() != nullptr, "Sanity");
2434 return (address) heap->collection_set()->biased_map_address();
2435 }
2436
2437 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2438 _degenerated_gc_in_progress.set_cond(in_progress);
2439 }
2440
2441 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2442 _full_gc_in_progress.set_cond(in_progress);
2443 }
2444
2445 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2446 assert (is_full_gc_in_progress(), "should be");
2447 _full_gc_move_in_progress.set_cond(in_progress);
2448 }
2449
2450 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2451 set_gc_state_at_safepoint(UPDATE_REFS, in_progress);
2452 }
2453
2454 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2455 ShenandoahCodeRoots::register_nmethod(nm);
2456 }
2457
2458 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2459 ShenandoahCodeRoots::unregister_nmethod(nm);
2460 }
2461
2462 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2463 assert(thr == JavaThread::current(), "Sanity");
2464 size_t reg_idx_pin = heap_region_index_containing(o);
2465 size_t reg_idx_cached = ShenandoahThreadLocalData::pin_cache_region(thr);
2466 size_t count = ShenandoahThreadLocalData::pin_cache_count(thr);
2467 if (reg_idx_pin == reg_idx_cached) {
2468 ShenandoahThreadLocalData::pin_cache_set_count(thr, count + 1);
2469 } else {
2470 if (count != 0) {
2471 get_region(reg_idx_cached)->record_pin(count);
2472 }
2473 ShenandoahThreadLocalData::pin_cache_set_region(thr, reg_idx_pin);
2474 ShenandoahThreadLocalData::pin_cache_set_count(thr, 1);
2475 }
2476 }
2477
2478 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2479 assert(thr == JavaThread::current(), "Sanity");
2480 size_t reg_idx_pin = heap_region_index_containing(o);
2481 size_t reg_idx_cached = ShenandoahThreadLocalData::pin_cache_region(thr);
2482 if (reg_idx_pin == reg_idx_cached) {
2483 size_t count = ShenandoahThreadLocalData::pin_cache_count(thr);
2484 ShenandoahThreadLocalData::pin_cache_set_count(thr, count - 1);
2485 } else {
2486 get_region(reg_idx_pin)->record_unpin();
2487 }
2488 }
2489
2490 void ShenandoahHeap::flush_region_pin_cache(JavaThread* thr) {
2491 size_t count = ShenandoahThreadLocalData::pin_cache_count(thr);
2492 if (count != 0) {
2493 size_t reg_idx_cached = ShenandoahThreadLocalData::pin_cache_region(thr);
2494 get_region(reg_idx_cached)->record_pin(count);
2495 ShenandoahThreadLocalData::pin_cache_set_count(thr, 0);
2496 }
2497 }
2498
2499 void ShenandoahHeap::flush_region_pin_cache() {
2500 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2501 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
2502 flush_region_pin_cache(t);
2503 }
2504 }
2505
2506 void ShenandoahHeap::sync_pinned_region_status() {
2507 flush_region_pin_cache();
2508 ShenandoahHeapLocker locker(lock());
2509
2510 for (size_t i = 0; i < num_regions(); i++) {
2511 ShenandoahHeapRegion *r = get_region(i);
2512 if (r->is_active()) {
2513 if (r->is_pinned()) {
2514 if (r->pin_count() == 0) {
2515 r->make_unpinned();
2516 }
2517 } else {
2518 if (r->pin_count() > 0) {
2519 r->make_pinned();
2520 }
2521 }
2522 }
2523 }
2524
2525 assert_pinned_region_status();
2526 }
2527
2528 #ifdef ASSERT
2529 void ShenandoahHeap::assert_pinned_region_status() const {
2530 assert_pinned_region_status(global_generation());
2531 }
2532
2533 void ShenandoahHeap::assert_pinned_region_status(ShenandoahGeneration* generation) const {
2534 for (size_t i = 0; i < num_regions(); i++) {
2535 ShenandoahHeapRegion* r = get_region(i);
2536 if (generation->contains(r)) {
2537 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2538 "Region %zu pinning status is inconsistent", i);
2539 }
2540 }
2541 }
2542 #endif
2543
2544 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2545 return _gc_timer;
2546 }
2547
2548 void ShenandoahHeap::prepare_concurrent_roots() {
2549 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2550 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2551 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2552 set_concurrent_weak_root_in_progress(true);
2553 if (unload_classes()) {
2554 _unloader.prepare();
2555 }
2556 }
2557
2558 void ShenandoahHeap::finish_concurrent_roots() {
2559 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2560 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2561 if (unload_classes()) {
2562 _unloader.finish();
2563 }
2564 }
2565
2566 #ifdef ASSERT
2567 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2568 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2569
2570 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2571 // Use ParallelGCThreads inside safepoints
2572 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2573 ParallelGCThreads, nworkers);
2574 } else {
2575 // Use ConcGCThreads outside safepoints
2576 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2577 ConcGCThreads, nworkers);
2578 }
2579 }
2580 #endif
2581
2582 ShenandoahVerifier* ShenandoahHeap::verifier() {
2583 guarantee(ShenandoahVerify, "Should be enabled");
2584 assert (_verifier != nullptr, "sanity");
2585 return _verifier;
2586 }
2587
2588 template<bool CONCURRENT>
2589 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2590 private:
2591 ShenandoahHeap* _heap;
2592 ShenandoahRegionIterator* _regions;
2593 public:
2594 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2595 WorkerTask("Shenandoah Update References"),
2596 _heap(ShenandoahHeap::heap()),
2597 _regions(regions) {
2598 }
2599
2600 void work(uint worker_id) {
2601 if (CONCURRENT) {
2602 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
2603 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2604 SuspendibleThreadSetJoiner stsj;
2605 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2606 } else {
2607 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
2608 ShenandoahParallelWorkerSession worker_session(worker_id);
2609 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2610 }
2611 }
2612
2613 private:
2614 template<class T>
2615 void do_work(uint worker_id) {
2616 if (CONCURRENT && (worker_id == 0)) {
2617 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2618 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2619 size_t cset_regions = _heap->collection_set()->count();
2620
2621 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2622 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2623 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2624 // next GC cycle.
2625 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2626 }
2627 // If !CONCURRENT, there's no value in expanding Mutator free set
2628 T cl;
2629 ShenandoahHeapRegion* r = _regions->next();
2630 while (r != nullptr) {
2631 HeapWord* update_watermark = r->get_update_watermark();
2632 assert (update_watermark >= r->bottom(), "sanity");
2633 if (r->is_active() && !r->is_cset()) {
2634 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2635 }
2636 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2637 return;
2638 }
2639 r = _regions->next();
2640 }
2641 }
2642 };
2643
2644 void ShenandoahHeap::update_heap_references(ShenandoahGeneration* generation, bool concurrent) {
2645 assert(generation->is_global(), "Should only get global generation here");
2646 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2647
2648 if (concurrent) {
2649 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2650 workers()->run_task(&task);
2651 } else {
2652 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2653 workers()->run_task(&task);
2654 }
2655 }
2656
2657 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2658 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2659 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2660
2661 {
2662 ShenandoahGCPhase phase(concurrent ?
2663 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2664 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2665
2666 final_update_refs_update_region_states();
2667
2668 assert_pinned_region_status();
2669 }
2670
2671 {
2672 ShenandoahGCPhase phase(concurrent ?
2673 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2674 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2675 trash_cset_regions();
2676 }
2677 }
2678
2679 void ShenandoahHeap::final_update_refs_update_region_states() {
2680 ShenandoahSynchronizePinnedRegionStates cl;
2681 parallel_heap_region_iterate(&cl);
2682 }
2683
2684 void ShenandoahHeap::rebuild_free_set_within_phase() {
2685 ShenandoahHeapLocker locker(lock());
2686 size_t young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count;
2687 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count);
2688 // If there are no old regions, first_old_region will be greater than last_old_region
2689 assert((first_old_region > last_old_region) ||
2690 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2691 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2692 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu",
2693 old_region_count, first_old_region, last_old_region);
2694
2695 if (mode()->is_generational()) {
2696 #ifdef ASSERT
2697 if (ShenandoahVerify) {
2698 verifier()->verify_before_rebuilding_free_set();
2699 }
2700 #endif
2701
2702 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2703 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2704 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2705 size_t allocation_runway =
2706 gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_trashed_regions);
2707 size_t max_transfer = MIN2(allocation_runway,
2708 (gen_heap->young_generation()->free_unaffiliated_regions() + young_trashed_regions) *
2709 ShenandoahHeapRegion::region_size_bytes());
2710 gen_heap->compute_old_generation_balance(max_transfer, old_trashed_regions, young_trashed_regions);
2711 }
2712 // Rebuild free set based on adjusted generation sizes.
2713 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, old_region_count);
2714
2715 if (mode()->is_generational()) {
2716 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2717 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2718 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2719 }
2720 }
2721
2722 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2723 ShenandoahGCPhase phase(concurrent ?
2724 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2725 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2726 rebuild_free_set_within_phase();
2727 }
2728
2729 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2730 size_t slice = r->index() / _bitmap_regions_per_slice;
2731
2732 size_t regions_from = _bitmap_regions_per_slice * slice;
2733 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2734 for (size_t g = regions_from; g < regions_to; g++) {
2735 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2736 if (skip_self && g == r->index()) continue;
2737 if (get_region(g)->is_committed()) {
2738 return true;
2739 }
2740 }
2741 return false;
2742 }
2743
2744 void ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2745 shenandoah_assert_heaplocked();
2746 assert(!is_bitmap_region_special(), "Not for special memory");
2747
2748 if (is_bitmap_slice_committed(r, true)) {
2749 // Some other region from the group is already committed, meaning the bitmap
2750 // slice is already committed, we exit right away.
2751 return;
2752 }
2753
2754 // Commit the bitmap slice:
2755 size_t slice = r->index() / _bitmap_regions_per_slice;
2756 size_t off = _bitmap_bytes_per_slice * slice;
2757 size_t len = _bitmap_bytes_per_slice;
2758 char* start = (char*) _bitmap_region.start() + off;
2759
2760 os::commit_memory_or_exit(start, len, false, "Unable to commit bitmap slice");
2761
2762 if (AlwaysPreTouch) {
2763 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2764 }
2765 }
2766
2767 void ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2768 shenandoah_assert_heaplocked();
2769 assert(!is_bitmap_region_special(), "Not for special memory");
2770
2771 if (is_bitmap_slice_committed(r, true)) {
2772 // Some other region from the group is still committed, meaning the bitmap
2773 // slice should stay committed, exit right away.
2774 return;
2775 }
2776
2777 // Uncommit the bitmap slice:
2778 size_t slice = r->index() / _bitmap_regions_per_slice;
2779 size_t off = _bitmap_bytes_per_slice * slice;
2780 size_t len = _bitmap_bytes_per_slice;
2781
2782 char* addr = (char*) _bitmap_region.start() + off;
2783 os::uncommit_memory(addr, len);
2784 }
2785
2786 void ShenandoahHeap::forbid_uncommit() {
2787 if (_uncommit_thread != nullptr) {
2788 _uncommit_thread->forbid_uncommit();
2789 }
2790 }
2791
2792 void ShenandoahHeap::allow_uncommit() {
2793 if (_uncommit_thread != nullptr) {
2794 _uncommit_thread->allow_uncommit();
2795 }
2796 }
2797
2798 #ifdef ASSERT
2799 bool ShenandoahHeap::is_uncommit_in_progress() {
2800 if (_uncommit_thread != nullptr) {
2801 return _uncommit_thread->is_uncommit_in_progress();
2802 }
2803 return false;
2804 }
2805 #endif
2806
2807 void ShenandoahHeap::safepoint_synchronize_begin() {
2808 StackWatermarkSet::safepoint_synchronize_begin();
2809 SuspendibleThreadSet::synchronize();
2810 }
2811
2812 void ShenandoahHeap::safepoint_synchronize_end() {
2813 SuspendibleThreadSet::desynchronize();
2814 }
2815
2816 void ShenandoahHeap::try_inject_alloc_failure() {
2817 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2818 _inject_alloc_failure.set();
2819 os::naked_short_sleep(1);
2820 if (cancelled_gc()) {
2821 log_info(gc)("Allocation failure was successfully injected");
2822 }
2823 }
2824 }
2825
2826 bool ShenandoahHeap::should_inject_alloc_failure() {
2827 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2828 }
2829
2830 void ShenandoahHeap::try_inject_pin() {
2831 assert(!ShenandoahSafepoint::is_at_shenandoah_safepoint(), "try_inject_pin() must be called outside a safepoint.");
2832 assert(active_generation() != nullptr, "Active generation must be set before we inject pins.");
2833 assert(is_concurrent_mark_in_progress() || active_generation()->is_mark_complete(),
2834 "try_inject_pin() requires marking is in progress or has completed.");
2835 if (ShenandoahPinRegionRate && !cancelled_gc() && ((uintx)(os::random() % 1000) < ShenandoahPinRegionRate) &&
2836 _injected_pin_count < MAX_INJECTED_PINS) {
2837 const size_t idx = os::random() % num_regions();
2838 ShenandoahHeapRegion* r = get_region(idx);
2839 if ((r->is_regular() || r->is_humongous_start()) && r->has_live()) {
2840 r->record_pin();
2841 _injected_pin_indices[_injected_pin_count] = idx;
2842 _injected_pin_count++;
2843 }
2844 }
2845 }
2846
2847 void ShenandoahHeap::release_injected_pins() {
2848 if (_injected_pin_count == 0) {
2849 return;
2850 }
2851
2852 assert(_injected_pin_count <= MAX_INJECTED_PINS,
2853 "Injected pin count: %u exceeds max: %u.", _injected_pin_count, MAX_INJECTED_PINS);
2854 for (uint i = 0; i < _injected_pin_count; i++) {
2855 const size_t idx = _injected_pin_indices[i];
2856 ShenandoahHeapRegion* r = get_region(idx);
2857 assert(r->pin_count() > 0, "Region %zu in tracker must contain a pin.", idx);
2858 r->record_unpin();
2859 }
2860 _injected_pin_count = 0;
2861 }
2862
2863 void ShenandoahHeap::initialize_serviceability() {
2864 _memory_pool = new ShenandoahMemoryPool(this);
2865 _cycle_memory_manager.add_pool(_memory_pool);
2866 _stw_memory_manager.add_pool(_memory_pool);
2867 }
2868
2869 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2870 GrowableArray<GCMemoryManager*> memory_managers(2);
2871 memory_managers.append(&_cycle_memory_manager);
2872 memory_managers.append(&_stw_memory_manager);
2873 return memory_managers;
2874 }
2875
2876 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2877 GrowableArray<MemoryPool*> memory_pools(1);
2878 memory_pools.append(_memory_pool);
2879 return memory_pools;
2880 }
2881
2882 MemoryUsage ShenandoahHeap::memory_usage() {
2883 return shenandoah_memory_usage(_initial_size, used(), committed(), max_capacity());
2884 }
2885
2886 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2887 _heap(ShenandoahHeap::heap()),
2888 _index(0) {}
2889
2890 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2891 _heap(heap),
2892 _index(0) {}
2893
2894 void ShenandoahRegionIterator::reset() {
2895 _index.store_relaxed(0);
2896 }
2897
2898 bool ShenandoahRegionIterator::has_next() const {
2899 return _index.load_relaxed() < _heap->num_regions();
2900 }
2901
2902 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2903 #ifdef ASSERT
2904 assert(_liveness_cache != nullptr, "sanity");
2905 assert(worker_id < _max_workers, "sanity");
2906 for (uint i = 0; i < num_regions(); i++) {
2907 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2908 }
2909 #endif
2910 return _liveness_cache[worker_id];
2911 }
2912
2913 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2914 assert(worker_id < _max_workers, "sanity");
2915 assert(_liveness_cache != nullptr, "sanity");
2916 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2917 for (uint i = 0; i < num_regions(); i++) {
2918 ShenandoahLiveData live = ld[i];
2919 if (live > 0) {
2920 ShenandoahHeapRegion* r = get_region(i);
2921 r->increase_live_data_gc_words(live);
2922 ld[i] = 0;
2923 }
2924 }
2925 }
2926
2927 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2928 // Can not guarantee obj is deeply good.
2929 if (has_forwarded_objects()) {
2930 return true;
2931 }
2932
2933 // Objects allocated after marking start are implicitly alive.
2934 if (is_concurrent_mark_in_progress() &&
2935 !marking_context()->allocated_after_mark_start(obj)) {
2936 return true;
2937 }
2938
2939 // Nmethods referenced by stack chunk may need the barrier fixups.
2940 if (ShenandoahStackChunkGCData::is_different_epoch(obj)) {
2941 return true;
2942 }
2943
2944 return false;
2945 }
2946
2947 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2948 #if INCLUDE_CDS_JAVA_HEAP
2949 // CDS wants a raw continuous memory range to load a bunch of objects itself.
2950 // This is an unusual request, since all requested regions should be regular, not humongous.
2951 //
2952 // CDS would guarantee no objects straddle multiple regions, as long as regions are as large
2953 // as MIN_GC_REGION_ALIGNMENT.
2954 guarantee(ShenandoahHeapRegion::region_size_bytes() >= AOTMappedHeapWriter::MIN_GC_REGION_ALIGNMENT, "Must be");
2955
2956 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_cds(size);
2957 return allocate_memory(req);
2958 #else
2959 assert(false, "Archive heap loader should not be available, should not be here");
2960 return nullptr;
2961 #endif // INCLUDE_CDS_JAVA_HEAP
2962 }
2963
2964 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2965 // Nothing to do here, except checking that heap looks fine.
2966 #ifdef ASSERT
2967 HeapWord* start = archive_space.start();
2968 HeapWord* end = archive_space.end();
2969
2970 // No unclaimed space between the objects.
2971 // Objects are properly allocated in correct regions.
2972 HeapWord* cur = start;
2973 while (cur < end) {
2974 oop oop = cast_to_oop(cur);
2975 shenandoah_assert_in_correct_region(nullptr, oop);
2976 cur += oop->size();
2977 }
2978
2979 // No unclaimed tail at the end of archive space.
2980 assert(cur == end,
2981 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2982 p2i(cur), p2i(end));
2983
2984 // All regions in contiguous space have good state.
2985 size_t begin_reg_idx = heap_region_index_containing(start);
2986 size_t end_reg_idx = heap_region_index_containing(end);
2987
2988 for (size_t idx = begin_reg_idx; idx <= end_reg_idx; idx++) {
2989 ShenandoahHeapRegion* r = get_region(idx);
2990 assert(r->is_regular(), "Must be regular");
2991 assert(r->is_young(), "Must be young");
2992 assert(idx == end_reg_idx || r->top() == r->end(),
2993 "All regions except the last one should be full: " PTR_FORMAT " " PTR_FORMAT,
2994 p2i(r->top()), p2i(r->end()));
2995 assert(idx != begin_reg_idx || r->bottom() == start,
2996 "Archive space start should be at the bottom of first region: " PTR_FORMAT " " PTR_FORMAT,
2997 p2i(r->bottom()), p2i(start));
2998 assert(idx != end_reg_idx || r->top() == end,
2999 "Archive space end should be at the top of last region: " PTR_FORMAT " " PTR_FORMAT,
3000 p2i(r->top()), p2i(end));
3001 }
3002
3003 #endif
3004 }
3005
3006 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
3007 if (!mode()->is_generational()) {
3008 return global_generation();
3009 } else if (affiliation == YOUNG_GENERATION) {
3010 return young_generation();
3011 } else if (affiliation == OLD_GENERATION) {
3012 return old_generation();
3013 }
3014
3015 ShouldNotReachHere();
3016 return nullptr;
3017 }
3018
3019 void ShenandoahHeap::log_heap_status(const char* msg) const {
3020 if (mode()->is_generational()) {
3021 young_generation()->log_status(msg);
3022 old_generation()->log_status(msg);
3023 } else {
3024 global_generation()->log_status(msg);
3025 }
3026 }
3027
3028 ShenandoahHeapLocker::ShenandoahHeapLocker(ShenandoahHeapLock* lock, bool allow_block_for_safepoint) : _lock(lock) {
3029 #ifdef ASSERT
3030 ShenandoahFreeSet* free_set = ShenandoahHeap::heap()->free_set();
3031 // free_set is nullptr only at pre-initialized state
3032 assert(free_set == nullptr || !free_set->rebuild_lock()->owned_by_self(), "Dead lock, can't acquire heap lock while holding free-set rebuild lock");
3033 assert(_lock != nullptr, "Must not");
3034 #endif
3035 _lock->lock(allow_block_for_safepoint);
3036 }