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 _biased_affiliations = _affiliations - (p2u(base()) >> ShenandoahHeapRegion::region_size_bytes_shift());
416
417 {
418 ShenandoahHeapLocker locker(lock());
419 for (size_t i = 0; i < _num_regions; i++) {
420 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
421 bool is_committed = i < num_committed_regions;
422 void* loc = region_storage.base() + i * region_align;
423
424 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
425 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
426
427 _marking_context->initialize_top_at_mark_start(r);
428 _regions[i] = r;
429 assert(!collection_set()->is_in(i), "New region should not be in collection set");
430
431 _affiliations[i] = ShenandoahAffiliation::FREE;
432 }
433
434 if (mode()->is_generational()) {
435 size_t young_reserve = (soft_max_capacity() * ShenandoahEvacReserve) / 100;
436 young_generation()->set_evacuation_reserve(young_reserve);
437 old_generation()->set_evacuation_reserve((size_t) 0);
438 old_generation()->set_promoted_reserve((size_t) 0);
439 }
440
441 _free_set = new ShenandoahFreeSet(this, _num_regions);
442 _allocator = new ShenandoahAllocator(_free_set);
443 initialize_generations();
444
445 // We are initializing free set. We ignore cset region tallies.
446 size_t young_trashed_regions, old_trashed_regions, first_old, last_old, num_old;
447 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old, last_old, num_old);
448 if (mode()->is_generational()) {
449 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
450 // We cannot call
451 // gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions)
452 // until after the heap is fully initialized. So we make up a safe value here.
453 size_t allocation_runway = InitialHeapSize / 2;
454 // We're initializing the heap. All regions within young are initially empty.
455 size_t max_transfer = allocation_runway;
456 gen_heap->compute_old_generation_balance(max_transfer, old_trashed_regions, young_trashed_regions);
457 }
458 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, num_old);
459 }
460
461 if (AlwaysPreTouch) {
462 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
463 // before initialize() below zeroes it with initializing thread. For any given region,
464 // we touch the region and the corresponding bitmaps from the same thread.
465 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
466
467 _pretouch_heap_page_size = heap_page_size;
468 _pretouch_bitmap_page_size = bitmap_page_size;
469
470 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
471 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
472
473 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
474 _workers->run_task(&bcl);
475
476 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
477 _workers->run_task(&hcl);
478 }
479
480 //
481 // Initialize the rest of GC subsystems
482 //
483
484 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
485 for (uint worker = 0; worker < _max_workers; worker++) {
486 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
487 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
488 }
489
490 // There should probably be Shenandoah-specific options for these,
491 // just as there are G1-specific options.
492 {
493 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
494 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
495 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
496 }
497
498 _monitoring_support = new ShenandoahMonitoringSupport(this);
499 _phase_timings = new ShenandoahPhaseTimings(max_workers());
500 ShenandoahCodeRoots::initialize();
501
502 // Initialization of controller makes use of variables established by initialize_heuristics.
503 initialize_controller();
504
505 // Certain initialization of heuristics must be deferred until after controller is initialized.
506 post_initialize_heuristics();
507 start_idle_span();
508 if (ShenandoahUncommit) {
509 _uncommit_thread = new ShenandoahUncommitThread(this);
510 }
511 print_init_logger();
512 FullGCForwarding::initialize(_heap_region);
513 return JNI_OK;
514 }
515
516 void ShenandoahHeap::initialize_controller() {
517 _control_thread = new ShenandoahControlThread();
518 }
519
520 void ShenandoahHeap::print_init_logger() const {
521 ShenandoahInitLogger::print();
522 }
523
524 void ShenandoahHeap::initialize_mode() {
525 if (ShenandoahGCMode != nullptr) {
526 if (strcmp(ShenandoahGCMode, "satb") == 0) {
527 _gc_mode = new ShenandoahSATBMode();
528 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
529 _gc_mode = new ShenandoahPassiveMode();
530 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
531 _gc_mode = new ShenandoahGenerationalMode();
532 } else {
533 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
534 }
535 } else {
536 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
537 }
538 _gc_mode->initialize_flags();
539 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
540 vm_exit_during_initialization(
541 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
542 _gc_mode->name()));
543 }
544 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
545 vm_exit_during_initialization(
546 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
547 _gc_mode->name()));
548 }
549 }
550
551 void ShenandoahHeap::initialize_heuristics() {
552 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers());
553 _global_generation->initialize_heuristics(mode());
554 }
555
556 #ifdef _MSC_VER
557 #pragma warning( push )
558 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
559 #endif
560
561 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
562 CollectedHeap(),
563 _active_generation(nullptr),
564 _initial_size(0),
565 _committed(0),
566 _alloc_rate_decay(&_alloc_rate),
567 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
568 _workers(nullptr),
569 _safepoint_workers(nullptr),
570 _heap_region_special(false),
571 _num_regions(0),
572 _regions(nullptr),
573 _affiliations(nullptr),
574 _biased_affiliations(nullptr),
575 _gc_state_changed(false),
576 _gc_no_progress_count(0),
577 _cancel_requested_time(0),
578 _update_refs_iterator(this),
579 _global_generation(nullptr),
580 _control_thread(nullptr),
581 _uncommit_thread(nullptr),
582 _young_generation(nullptr),
583 _old_generation(nullptr),
584 _shenandoah_policy(policy),
585 _gc_mode(nullptr),
586 _free_set(nullptr),
587 _allocator(nullptr),
588 _verifier(nullptr),
589 _phase_timings(nullptr),
590 _monitoring_support(nullptr),
591 _memory_pool(nullptr),
592 _stw_memory_manager("Shenandoah Pauses"),
593 _cycle_memory_manager("Shenandoah Cycles"),
594 _gc_timer(new ConcurrentGCTimer()),
595 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
596 _marking_context(nullptr),
597 _bitmap_size(0),
598 _bitmap_regions_per_slice(0),
599 _bitmap_bytes_per_slice(0),
600 _bitmap_region_special(false),
601 _aux_bitmap_region_special(false),
602 _liveness_cache(nullptr),
603 _collection_set(nullptr),
604 _evac_tracker(new ShenandoahEvacuationTracker()),
605 _injected_pin_count(0)
606 {
607 // Initialize GC mode early, many subsequent initialization procedures depend on it
608 initialize_mode();
609 _cancelled_gc.set(GCCause::_no_gc);
610 }
611
612 #ifdef _MSC_VER
613 #pragma warning( pop )
614 #endif
615
616 void ShenandoahHeap::print_heap_on(outputStream* st) const {
617 const bool is_generational = mode()->is_generational();
618 const char* front_spacing = "";
619 if (is_generational) {
620 st->print_cr("Generational Shenandoah Heap");
621 st->print_cr(" Young:");
622 st->print_cr(" " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(young_generation()->max_capacity()), PROPERFMTARGS(young_generation()->used()));
623 st->print_cr(" Old:");
624 st->print_cr(" " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(old_generation()->max_capacity()), PROPERFMTARGS(old_generation()->used()));
625 st->print_cr(" Entire heap:");
626 st->print_cr(" " PROPERFMT " soft max, " PROPERFMT " committed",
627 PROPERFMTARGS(soft_max_capacity()), PROPERFMTARGS(committed()));
628 front_spacing = " ";
629 } else {
630 st->print_cr("Shenandoah Heap");
631 st->print_cr(" " PROPERFMT " max, " PROPERFMT " soft max, " PROPERFMT " committed, " PROPERFMT " used",
632 PROPERFMTARGS(max_capacity()),
633 PROPERFMTARGS(soft_max_capacity()),
634 PROPERFMTARGS(committed()),
635 PROPERFMTARGS(used())
636 );
637 }
638 st->print_cr("%s %zu x " PROPERFMT " regions",
639 front_spacing,
640 num_regions(),
641 PROPERFMTARGS(ShenandoahHeapRegion::region_size_bytes()));
642
643 st->print("Status: ");
644 if (has_forwarded_objects()) st->print("has forwarded objects, ");
645 if (!is_generational) {
646 if (is_concurrent_mark_in_progress()) st->print("marking,");
647 } else {
648 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
649 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
650 }
651 if (is_evacuation_in_progress()) st->print("evacuating, ");
652 if (is_update_refs_in_progress()) st->print("updating refs, ");
653 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
654 if (is_full_gc_in_progress()) st->print("full gc, ");
655 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
656 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
657 if (is_concurrent_strong_root_in_progress() &&
658 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
659
660 if (cancelled_gc()) {
661 st->print("cancelled");
662 } else {
663 st->print("not cancelled");
664 }
665 st->cr();
666
667 st->print_cr("Reserved region:");
668 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
669 p2i(reserved_region().start()),
670 p2i(reserved_region().end()));
671
672 ShenandoahCollectionSet* cset = collection_set();
673 st->print_cr("Collection set:");
674 if (cset != nullptr) {
675 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
676 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
677 } else {
678 st->print_cr(" (null)");
679 }
680
681 st->cr();
682
683 if (Verbose) {
684 st->cr();
685 print_heap_regions_on(st);
686 }
687 }
688
689 void ShenandoahHeap::print_gc_on(outputStream* st) const {
690 print_heap_regions_on(st);
691 }
692
693 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
694 public:
695 void do_thread(Thread* thread) {
696 assert(thread != nullptr, "Sanity");
697 ShenandoahThreadLocalData::initialize_gclab(thread);
698 }
699 };
700
701 void ShenandoahHeap::initialize_generations() {
702 _global_generation->post_initialize(this);
703 }
704
705 // We do not call this explicitly It is called by Hotspot infrastructure.
706 void ShenandoahHeap::post_initialize() {
707 CollectedHeap::post_initialize();
708
709 check_soft_max_changed();
710
711 // Schedule periodic task to report on gc thread CPU utilization
712 _mmu_tracker.initialize();
713
714 // Periodically decay allocation rate to compensate for not being updated when allocation rate
715 // is low. Heuristics are evaluated unconditionally from a dedicated thread so it will continue
716 // to see the last (possibly stale) allocation rate if the allocation rate is low.
717 _alloc_rate_decay.enroll();
718
719 MutexLocker ml(Threads_lock);
720
721 ShenandoahInitWorkerGCLABClosure init_gclabs;
722 _workers->threads_do(&init_gclabs);
723
724 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
725 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
726 _workers->set_initialize_gclab();
727
728 // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump
729 // during a concurrent evacuation phase.
730 if (_safepoint_workers != nullptr) {
731 _safepoint_workers->threads_do(&init_gclabs);
732 _safepoint_workers->set_initialize_gclab();
733 }
734
735 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
736 }
737
738 void ShenandoahHeap::post_initialize_heuristics() {
739 _global_generation->post_initialize_heuristics();
740 }
741
742 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
743 return _global_generation->heuristics();
744 }
745
746 size_t ShenandoahHeap::used() const {
747 return global_generation()->used();
748 }
749
750 size_t ShenandoahHeap::committed() const {
751 return _committed.load_relaxed();
752 }
753
754 void ShenandoahHeap::increase_committed(size_t bytes) {
755 shenandoah_assert_heaplocked_or_safepoint();
756 _committed.fetch_then_add(bytes, memory_order_relaxed);
757 }
758
759 void ShenandoahHeap::decrease_committed(size_t bytes) {
760 shenandoah_assert_heaplocked_or_safepoint();
761 _committed.fetch_then_sub(bytes, memory_order_relaxed);
762 }
763
764 size_t ShenandoahHeap::capacity() const {
765 return committed();
766 }
767
768 size_t ShenandoahHeap::max_capacity() const {
769 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
770 }
771
772 size_t ShenandoahHeap::soft_max_capacity() const {
773 size_t v = _soft_max_size.load_relaxed();
774 assert(min_capacity() <= v && v <= max_capacity(),
775 "Should be in bounds: %zu <= %zu <= %zu",
776 min_capacity(), v, max_capacity());
777 return v;
778 }
779
780 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
781 assert(min_capacity() <= v && v <= max_capacity(),
782 "Should be in bounds: %zu <= %zu <= %zu",
783 min_capacity(), v, max_capacity());
784 _soft_max_size.store_relaxed(v);
785 heuristics()->compute_headroom_adjustment();
786 }
787
788 size_t ShenandoahHeap::min_capacity() const {
789 return _minimum_size;
790 }
791
792 size_t ShenandoahHeap::initial_capacity() const {
793 return _initial_size;
794 }
795
796 bool ShenandoahHeap::is_in(const void* p) const {
797 if (!is_in_reserved(p)) {
798 return false;
799 }
800
801 if (is_full_gc_move_in_progress()) {
802 // Full GC move is running, we do not have a consistent region
803 // information yet. But we know the pointer is in heap.
804 return true;
805 }
806
807 // Now check if we point to a live section in active region.
808 const ShenandoahHeapRegion* r = heap_region_containing(p);
809 if (p >= r->top()) {
810 return false;
811 }
812
813 if (r->is_active()) {
814 return true;
815 }
816
817 // The region is trash, but won't be recycled until after concurrent weak
818 // roots. We also don't allow mutators to allocate from trash regions
819 // during weak roots. Concurrent class unloading may access unmarked oops
820 // in trash regions.
821 return r->is_trash() && is_concurrent_weak_root_in_progress();
822 }
823
824 void ShenandoahHeap::notify_soft_max_changed() {
825 if (_uncommit_thread != nullptr) {
826 _uncommit_thread->notify_soft_max_changed();
827 }
828 }
829
830 void ShenandoahHeap::notify_explicit_gc_requested() {
831 if (_uncommit_thread != nullptr) {
832 _uncommit_thread->notify_explicit_gc_requested();
833 }
834 }
835
836 bool ShenandoahHeap::check_soft_max_changed() {
837 size_t new_soft_max = AtomicAccess::load(&SoftMaxHeapSize);
838 size_t old_soft_max = soft_max_capacity();
839 if (new_soft_max != old_soft_max) {
840 new_soft_max = clamp(new_soft_max, min_capacity(), max_capacity());
841 if (new_soft_max != old_soft_max) {
842 log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s",
843 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
844 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
845 );
846 set_soft_max_capacity(new_soft_max);
847 return true;
848 }
849 }
850 return false;
851 }
852
853 void ShenandoahHeap::notify_heap_changed() {
854 // Update monitoring counters when we took a new region. This amortizes the
855 // update costs on slow path.
856 monitoring_support()->notify_heap_changed();
857 _heap_changed.try_set();
858 }
859
860 void ShenandoahHeap::start_idle_span() {
861 heuristics()->start_idle_span();
862 }
863
864 void ShenandoahHeap::set_forced_counters_update(bool value) {
865 monitoring_support()->set_forced_counters_update(value);
866 }
867
868 void ShenandoahHeap::handle_force_counters_update() {
869 monitoring_support()->handle_force_counters_update();
870 }
871
872 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
873 // New object should fit the GCLAB size
874 size_t min_size = MAX2(size, PLAB::min_size());
875
876 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
877 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
878
879 new_size = MIN2(new_size, PLAB::max_size());
880 new_size = MAX2(new_size, PLAB::min_size());
881
882 // Record new heuristic value even if we take any shortcut. This captures
883 // the case when moderately-sized objects always take a shortcut. At some point,
884 // heuristics should catch up with them.
885 log_debug(gc, free)("Set new GCLAB size: %zu", new_size);
886 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
887
888 if (new_size < size) {
889 // New size still does not fit the object. Fall back to shared allocation.
890 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
891 log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size);
892 return nullptr;
893 }
894
895 // Retire current GCLAB, and allocate a new one.
896 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
897 gclab->retire();
898
899 size_t actual_size = 0;
900 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
901 if (gclab_buf == nullptr) {
902 return nullptr;
903 }
904
905 assert (size <= actual_size, "allocation should fit");
906
907 // ...and clear or zap just allocated TLAB, if needed.
908 if (ZeroTLAB) {
909 Copy::zero_to_words(gclab_buf, actual_size);
910 } else if (ZapTLAB) {
911 // Skip mangling the space corresponding to the object header to
912 // ensure that the returned space is not considered parsable by
913 // any concurrent GC thread.
914 size_t hdr_size = oopDesc::header_size();
915 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
916 }
917 gclab->set_buf(gclab_buf, actual_size);
918 return gclab->allocate(size);
919 }
920
921 // Called from stubs in JIT code or interpreter
922 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
923 size_t requested_size,
924 size_t* actual_size) {
925 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
926 HeapWord* res = allocate_memory(req);
927 if (res != nullptr) {
928 *actual_size = req.actual_size();
929 } else {
930 *actual_size = 0;
931 }
932 return res;
933 }
934
935 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
936 size_t word_size,
937 size_t* actual_size) {
938 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
939 HeapWord* res = allocate_memory(req);
940 if (res != nullptr) {
941 *actual_size = req.actual_size();
942 } else {
943 *actual_size = 0;
944 }
945 return res;
946 }
947
948 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
949 bool in_new_region = false;
950 HeapWord* result = nullptr;
951
952 if (req.is_mutator_alloc()) {
953
954 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
955 result = allocate_memory_work(req, in_new_region);
956 }
957
958 // Check that gc overhead is not exceeded.
959 //
960 // Shenandoah will grind along for quite a while allocating one
961 // object at a time using shared (non-tlab) allocations. This check
962 // is testing that the GC overhead limit has not been exceeded.
963 // This will notify the collector to start a cycle, but will raise
964 // an OOME to the mutator if the last Full GCs have not made progress.
965 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
966 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
967 control_thread()->handle_alloc_failure(req, false);
968 req.set_actual_size(0);
969 return nullptr;
970 }
971
972 if (result == nullptr) {
973 // Block until control thread reacted, then retry allocation.
974 //
975 // It might happen that one of the threads requesting allocation would unblock
976 // way later after GC happened, only to fail the second allocation, because
977 // other threads have already depleted the free storage. In this case, a better
978 // strategy is to try again, until at least one full GC has completed.
979 //
980 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
981 // a) We experienced a GC that had good progress, or
982 // b) We experienced at least one Full GC (whether or not it had good progress)
983
984 const size_t original_count = shenandoah_policy()->full_gc_count();
985 while (result == nullptr && should_retry_allocation(original_count)) {
986 control_thread()->handle_alloc_failure(req, true);
987 result = allocate_memory_work(req, in_new_region);
988 }
989 if (result != nullptr) {
990 // If our allocation request has been satisfied after it initially failed, we count this as good gc progress
991 notify_gc_progress();
992 }
993 if (log_develop_is_enabled(Debug, gc, alloc)) {
994 ResourceMark rm;
995 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu"
996 ", Original: %zu, Latest: %zu",
997 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
998 original_count, get_gc_no_progress_count());
999 }
1000 }
1001 } else {
1002 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
1003 result = allocate_memory_work(req, in_new_region);
1004 // Do not call handle_alloc_failure() here, because we cannot block.
1005 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1006 }
1007
1008 if (in_new_region) {
1009 notify_heap_changed();
1010 }
1011
1012 if (result == nullptr) {
1013 req.set_actual_size(0);
1014 }
1015
1016 if (result != nullptr) {
1017 size_t requested = req.size();
1018 size_t actual = req.actual_size();
1019
1020 assert (req.is_lab_alloc() || (requested == actual),
1021 "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu",
1022 req.type_string(), requested, actual);
1023 }
1024
1025 return result;
1026 }
1027
1028 inline bool ShenandoahHeap::should_retry_allocation(size_t original_full_gc_count) const {
1029 return shenandoah_policy()->full_gc_count() == original_full_gc_count
1030 && !shenandoah_policy()->is_at_shutdown();
1031 }
1032
1033 HeapWord* ShenandoahHeap::allocate_memory_work(ShenandoahAllocRequest& req, bool& in_new_region) {
1034 // Reserve the promotion budget up front so it is enforced atomically without the heap lock.
1035 // If the reserve is exhausted, deny the promotion rather than overshoot it; the reservation
1036 // is refunded below if the allocation itself fails.
1037 if (req.is_promotion() && !old_generation()->try_expend_promoted(req.size() << LogHeapWordSize)) {
1038 return nullptr;
1039 }
1040
1041 HeapWord* result = _allocator->allocate(req, in_new_region);
1042
1043 if (result != nullptr) {
1044 if (req.is_mutator_alloc()) {
1045 _alloc_rate.allocated((req.actual_size() + req.waste()) * HeapWordSize);
1046 }
1047
1048 if (req.is_old()) {
1049 if (req.is_lab_alloc()) {
1050 old_generation()->configure_plab_for_current_thread(req);
1051 } else if (req.is_promotion()) {
1052 log_debug(gc, plab)("Expend shared promotion of %zu bytes", req.actual_size() * HeapWordSize);
1053 }
1054 }
1055 } else if (req.is_promotion()) {
1056 // Allocation failed, so refund the promotion budget reserved above.
1057 old_generation()->unexpend_promoted(req.size() << LogHeapWordSize);
1058 }
1059 return result;
1060 }
1061
1062 HeapWord* ShenandoahHeap::mem_allocate(size_t size) {
1063 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1064 return allocate_memory(req);
1065 }
1066
1067 oop ShenandoahHeap::array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS) {
1068 ShenandoahObjArrayAllocator allocator(klass, size, length, do_zero, THREAD);
1069 return allocator.allocate();
1070 }
1071
1072 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1073 size_t size,
1074 Metaspace::MetadataType mdtype) {
1075 MetaWord* result;
1076
1077 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1078 ShenandoahHeuristics* h = global_generation()->heuristics();
1079 if (h->can_unload_classes()) {
1080 h->record_metaspace_oom();
1081 }
1082
1083 // Expand and retry allocation
1084 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1085 if (result != nullptr) {
1086 return result;
1087 }
1088
1089 // Start full GC
1090 collect(GCCause::_metadata_GC_clear_soft_refs);
1091
1092 // Retry allocation
1093 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1094 if (result != nullptr) {
1095 return result;
1096 }
1097
1098 // Expand and retry allocation
1099 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1100 if (result != nullptr) {
1101 return result;
1102 }
1103
1104 // Out of memory
1105 return nullptr;
1106 }
1107
1108 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1109 private:
1110 ShenandoahHeap* const _heap;
1111 Thread* const _thread;
1112 public:
1113 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1114 _heap(heap), _thread(Thread::current()) {}
1115
1116 void do_object(oop p) {
1117 shenandoah_assert_marked(nullptr, p);
1118 if (!p->is_forwarded()) {
1119 _heap->evacuate_object(p, _thread);
1120 }
1121 }
1122 };
1123
1124 class ShenandoahEvacuationTask : public WorkerTask {
1125 private:
1126 ShenandoahHeap* const _sh;
1127 ShenandoahCollectionSet* const _cs;
1128 bool _concurrent;
1129 public:
1130 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1131 ShenandoahCollectionSet* cs,
1132 bool concurrent) :
1133 WorkerTask("Shenandoah Evacuation"),
1134 _sh(sh),
1135 _cs(cs),
1136 _concurrent(concurrent)
1137 {}
1138
1139 void work(uint worker_id) {
1140 if (_concurrent) {
1141 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_evac, ShenandoahPhaseTimings::Work, worker_id, true);
1142 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1143 SuspendibleThreadSetJoiner stsj;
1144 do_work();
1145 } else {
1146 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_evac, ShenandoahPhaseTimings::Work, worker_id, true);
1147 ShenandoahParallelWorkerSession worker_session(worker_id);
1148 do_work();
1149 }
1150 }
1151
1152 private:
1153 void do_work() {
1154 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1155 ShenandoahHeapRegion* r;
1156 while ((r =_cs->claim_next()) != nullptr) {
1157 assert(r->has_live(), "Region %zu should have been reclaimed early", r->index());
1158 _sh->marked_object_iterate(r, &cl);
1159
1160 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1161 break;
1162 }
1163 }
1164 }
1165 };
1166
1167 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1168 private:
1169 bool const _resize;
1170 public:
1171 explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1172 void do_thread(Thread* thread) override {
1173 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1174 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1175 gclab->retire();
1176 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1177 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1178 }
1179
1180 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1181 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1182 assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1183
1184 // There are two reasons to retire all plabs between old-gen evacuation passes.
1185 // 1. We need to make the plab memory parsable by remembered-set scanning.
1186 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1187 shenandoah_plab->retire();
1188
1189 // Re-enable promotions for the next evacuation phase.
1190 shenandoah_plab->enable_promotions();
1191
1192 // Reset the fill size for next evacuation phase.
1193 if (_resize && shenandoah_plab->desired_size() > 0) {
1194 shenandoah_plab->set_desired_size(0);
1195 }
1196 }
1197 }
1198 };
1199
1200 class ShenandoahGCStatePropagatorHandshakeClosure : public HandshakeClosure {
1201 public:
1202 explicit ShenandoahGCStatePropagatorHandshakeClosure(char gc_state) :
1203 HandshakeClosure("Shenandoah GC State Change"),
1204 _gc_state(gc_state) {}
1205
1206 void do_thread(Thread* thread) override {
1207 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state);
1208 }
1209 private:
1210 char _gc_state;
1211 };
1212
1213 class ShenandoahPrepareForUpdateRefsHandshakeClosure : public HandshakeClosure {
1214 public:
1215 explicit ShenandoahPrepareForUpdateRefsHandshakeClosure(char gc_state) :
1216 HandshakeClosure("Shenandoah Prepare for Update Refs"),
1217 _retire(ResizeTLAB), _propagator(gc_state) {}
1218
1219 void do_thread(Thread* thread) override {
1220 _propagator.do_thread(thread);
1221 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) {
1222 _retire.do_thread(thread);
1223 }
1224 }
1225 private:
1226 ShenandoahRetireGCLABClosure _retire;
1227 ShenandoahGCStatePropagatorHandshakeClosure _propagator;
1228 };
1229
1230 void ShenandoahHeap::evacuate_collection_set(ShenandoahGeneration* generation, bool concurrent) {
1231 assert(generation->is_global(), "Only global generation expected here");
1232 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1233 workers()->run_task(&task);
1234 }
1235
1236 class ShenandoahCompleteStackWatermarkHandshakeClosure : public HandshakeClosure {
1237 public:
1238 ShenandoahCompleteStackWatermarkHandshakeClosure() : HandshakeClosure("Shenandoah Complete stacks handshake") {}
1239 void do_thread(Thread* thread) override {
1240 if (thread->is_Java_thread()) {
1241 JavaThread* jt = JavaThread::cast(thread);
1242 StackWatermarkSet::finish_processing(jt, nullptr, StackWatermarkKind::gc);
1243 }
1244 }
1245 };
1246
1247 void ShenandoahHeap::concurrent_prepare_for_update_refs() {
1248 // The stack watermarks are active since op_final_roots().
1249 // Make sure the current stack watermark machinery has completed before we drop evac flags.
1250 // Otherwise the stack processing on stack unwinding may enter evac closure concurrently.
1251 ShenandoahCompleteStackWatermarkHandshakeClosure cl;
1252 Handshake::execute(&cl);
1253
1254 {
1255 // Java threads take this lock while they are being attached and added to the list of threads.
1256 // If another thread holds this lock before we update the gc state, it will receive a stale
1257 // gc state, but they will have been added to the list of java threads and so will be corrected
1258 // by the following handshake.
1259 MutexLocker lock(Threads_lock);
1260
1261 // A cancellation at this point means the degenerated cycle must resume from update-refs.
1262 set_gc_state_concurrent(EVACUATION, false);
1263 set_gc_state_concurrent(UPDATE_REFS, true);
1264 }
1265
1266 // This will propagate the gc state and retire gclabs and plabs for threads that require it.
1267 ShenandoahPrepareForUpdateRefsHandshakeClosure prepare_for_update_refs(_gc_state.raw_value());
1268
1269 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately.
1270 Threads::non_java_threads_do(&prepare_for_update_refs);
1271
1272 // Now retire gclabs and plabs and propagate gc_state for mutator threads
1273 Handshake::execute(&prepare_for_update_refs);
1274
1275 _update_refs_iterator.reset();
1276 }
1277
1278 void ShenandoahHeap::op_final_roots() {
1279 #ifdef ASSERT
1280 // Check if stack watermark machinery is in safe state:
1281 // 1. With evac-in-progress, we are about to supersede evac processing with new epoch.
1282 // op_thread_roots() should have completed the stack watermark processing before
1283 // we reach here.
1284 // 2. Without evac-in-progress, we are in abbreviated cycle, and we are switching
1285 // to a new epoch that *also* does not change any oops, which is safe.
1286 if (is_evacuation_in_progress()) {
1287 for (JavaThreadIteratorWithHandle jtiwh; JavaThread* jt = jtiwh.next();) {
1288 StackWatermark* sw = StackWatermarkSet::get(jt, StackWatermarkKind::gc);
1289 assert(sw == nullptr || sw->processing_completed(),
1290 "Cannot turn off weak roots before stack watermark processing is complete");
1291 }
1292 }
1293 #endif
1294
1295 set_gc_state_at_safepoint(WEAK_ROOTS, false);
1296
1297 // Arm the nmethods to change the barriers.
1298 CodeCache::arm_all_nmethods();
1299
1300 {
1301 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_roots_propagate_gc_state);
1302 propagate_gc_state_to_all_threads();
1303 }
1304 }
1305
1306 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1307 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1308
1309 ShenandoahHeapRegion* r = heap_region_containing(p);
1310 assert(!r->is_humongous(), "never evacuate humongous objects");
1311
1312 ShenandoahAffiliation target_gen = r->affiliation();
1313 return try_evacuate_object(p, thread, r, target_gen);
1314 }
1315
1316 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1317 ShenandoahAffiliation target_gen) {
1318 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1319 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1320 bool alloc_from_lab = true;
1321 HeapWord* copy = nullptr;
1322 size_t size = ShenandoahForwarding::size(p);
1323
1324 #ifdef ASSERT
1325 if (ShenandoahOOMDuringEvacALot &&
1326 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1327 copy = nullptr;
1328 } else {
1329 #endif
1330 if (UseTLAB) {
1331 copy = allocate_from_gclab(thread, size);
1332 }
1333 if (copy == nullptr) {
1334 // If we failed to allocate in LAB, we'll try a shared allocation.
1335 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1336 copy = allocate_memory(req);
1337 alloc_from_lab = false;
1338 }
1339 #ifdef ASSERT
1340 }
1341 #endif
1342
1343 if (copy == nullptr) {
1344 control_thread()->handle_alloc_failure_evac(size);
1345
1346 // Install the self-forwarded bit on p so other evacuators/LRBs see
1347 // the object as "already handled, do not try to evacuate". The CAS
1348 // may fail if another thread concurrently installed a real forwardee
1349 // (they succeeded where we failed) or self-forwarded first.
1350 markWord old_mark = p->mark();
1351 if (old_mark.is_forwarded()) {
1352 return ShenandoahForwarding::get_forwardee(p);
1353 }
1354 oop winner = ShenandoahForwarding::try_forward_to_self(p, old_mark);
1355 if (winner == nullptr) {
1356 // We own the self-forwarding. Flag the region so the degen/full GC
1357 // entry drain knows to scan it for self_fwd bits to clear.
1358 from_region->set_has_self_forwards();
1359 return p;
1360 }
1361 return winner;
1362 }
1363
1364 if (ShenandoahEvacTracking) {
1365 evac_tracker()->begin_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1366 }
1367
1368 // Copy the object:
1369 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1370
1371 oop copy_val = cast_to_oop(copy);
1372
1373 // Relativize stack chunks before publishing the copy. After the forwarding CAS,
1374 // mutators can see the copy and thaw it via the fast path if flags == 0. We must
1375 // relativize derived pointers and set gc_mode before that happens. Skip if the
1376 // copy's mark word is already a forwarding pointer (another thread won the race
1377 // and overwrote the original's header before we copied it).
1378 if (!ShenandoahForwarding::is_forwarded(copy_val)) {
1379 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1380 }
1381
1382 // Try to install the new forwarding pointer.
1383 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1384 if (result == copy_val) {
1385 // Successfully evacuated. Our copy is now the public one!
1386 shenandoah_assert_correct(nullptr, copy_val);
1387 if (ShenandoahEvacTracking) {
1388 evac_tracker()->end_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1389 }
1390 return copy_val;
1391 } else {
1392 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1393 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1394 // But if it happens to contain references to evacuated regions, those references would
1395 // not get updated for this stale copy during this cycle, and we will crash while scanning
1396 // it the next cycle.
1397 if (alloc_from_lab) {
1398 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1399 // object will overwrite this stale copy, or the filler object on LAB retirement will
1400 // do this.
1401 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1402 } else {
1403 // For non-LAB allocations, we have no way to retract the allocation, and
1404 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1405 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1406 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1407 fill_with_object(copy, size);
1408 shenandoah_assert_correct(nullptr, copy_val);
1409 // For non-LAB allocations, the object has already been registered
1410 }
1411 shenandoah_assert_correct(nullptr, result);
1412 return result;
1413 }
1414 }
1415
1416 // Clear the self_fwd bit on a live cset object, if set. Runs at a safepoint,
1417 // so a plain store is sufficient — no concurrent writers to the mark word.
1418 class ShenandoahUnSelfForwardObjectClosure : public ObjectClosure {
1419 public:
1420 void do_object(oop obj) override {
1421 markWord m = obj->mark();
1422 if (m.is_self_forwarded()) {
1423 obj->set_mark(m.unset_self_forwarded());
1424 }
1425 }
1426 };
1427
1428 // Parallel task over flagged cset regions. Iterates the live objects via the
1429 // mark bitmap (skipping evacuated and never-marked memory), clears self_fwd
1430 // bits, and resets the region flag once done.
1431 class ShenandoahUnSelfForwardTask : public WorkerTask {
1432 private:
1433 ShenandoahHeap* const _heap;
1434 ShenandoahCollectionSet* const _cs;
1435
1436 public:
1437 ShenandoahUnSelfForwardTask(ShenandoahHeap* heap, ShenandoahCollectionSet* cs) :
1438 WorkerTask("Shenandoah Un-Self-Forward"),
1439 _heap(heap),
1440 _cs(cs) {}
1441
1442 void work(uint worker_id) override {
1443 ShenandoahParallelWorkerSession worker_session(worker_id);
1444 ShenandoahUnSelfForwardObjectClosure cl;
1445 ShenandoahHeapRegion* r;
1446 while ((r = _cs->claim_next()) != nullptr) {
1447 if (r->has_self_forwards()) {
1448 _heap->marked_object_iterate(r, &cl);
1449 r->clear_has_self_forwards();
1450 }
1451 }
1452 }
1453 };
1454
1455 void ShenandoahHeap::un_self_forward_cset_regions() {
1456 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1457 ShenandoahCollectionSet* cs = collection_set();
1458 if (cs == nullptr || cs->is_empty()) {
1459 return;
1460 }
1461 cs->clear_current_index();
1462 ShenandoahUnSelfForwardTask task(this, cs);
1463 workers()->run_task(&task);
1464 DEBUG_ONLY(assert_no_self_forwards());
1465 }
1466
1467 #ifdef ASSERT
1468 void ShenandoahHeap::assert_no_self_forwards() const {
1469 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1470 ShenandoahCollectionSet* cs = collection_set();
1471 if (cs == nullptr) return;
1472 cs->clear_current_index();
1473 ShenandoahHeapRegion* r;
1474 while ((r = cs->next()) != nullptr) {
1475 assert(!r->has_self_forwards(), "region still flagged after drain");
1476 }
1477 cs->clear_current_index();
1478 }
1479 #endif
1480
1481 void ShenandoahHeap::trash_cset_regions() {
1482 ShenandoahHeapLocker locker(lock());
1483
1484 ShenandoahCollectionSet* set = collection_set();
1485 ShenandoahHeapRegion* r;
1486 set->clear_current_index();
1487 while ((r = set->next()) != nullptr) {
1488 r->make_trash();
1489 }
1490 collection_set()->clear();
1491 }
1492
1493 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1494 st->print_cr("Heap Regions:");
1495 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1496 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1497 st->print_cr("A=age, BTE=bottom/top/end, TAMS=top-at-mark-start, UWM=update watermark, U=used");
1498 st->print_cr("T=TLAB allocs, G=GCLAB allocs, S=shared allocs, L=live data");
1499 st->print_cr("CP=critical pins");
1500
1501 for (size_t i = 0; i < num_regions(); i++) {
1502 get_region(i)->print_on(st);
1503 }
1504 }
1505
1506 void ShenandoahHeap::process_gc_stats() const {
1507 // Commit worker statistics to cycle data
1508 phase_timings()->flush_par_workers_to_cycle();
1509
1510 // Print GC stats for current cycle
1511 LogTarget(Info, gc, stats) lt;
1512 if (lt.is_enabled()) {
1513 ResourceMark rm;
1514 LogStream ls(lt);
1515 phase_timings()->print_cycle_on(&ls);
1516 if (ShenandoahEvacTracking) {
1517 ShenandoahCycleStats evac_stats = evac_tracker()->flush_cycle_to_global();
1518 evac_tracker()->print_evacuations_on(&ls, &evac_stats.workers,
1519 &evac_stats.mutators);
1520 }
1521 }
1522
1523 // Commit statistics to globals
1524 phase_timings()->flush_cycle_to_global();
1525 }
1526
1527 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) const {
1528 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1529 assert(!start->has_live(), "liveness must be zero");
1530
1531 // Do not try to get the size of this humongous object. STW collections will
1532 // have already unloaded classes, so an unmarked object may have a bad klass pointer.
1533 ShenandoahHeapRegion* region = start;
1534 size_t index = region->index();
1535 do {
1536 assert(region->is_humongous(), "Expect correct humongous start or continuation");
1537 assert(!region->is_cset(), "Humongous region should not be in collection set");
1538 region->make_trash_immediate();
1539 region = get_region(++index);
1540 } while (region != nullptr && region->is_humongous_continuation());
1541
1542 // Return number of regions trashed
1543 return index - start->index();
1544 }
1545
1546 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1547 public:
1548 ShenandoahCheckCleanGCLABClosure() {}
1549 void do_thread(Thread* thread) {
1550 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1551 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1552 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1553
1554 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1555 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1556 assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1557 assert(shenandoah_plab->plab()->words_remaining() == 0, "PLAB should not need retirement");
1558 }
1559 }
1560 };
1561
1562 void ShenandoahHeap::labs_make_parsable() {
1563 assert(UseTLAB, "Only call with UseTLAB");
1564
1565 ShenandoahRetireGCLABClosure cl(false);
1566
1567 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1568 ThreadLocalAllocBuffer& tlab = t->tlab();
1569 tlab.make_parsable();
1570 if (ZeroTLAB) {
1571 t->retire_tlab();
1572 }
1573 cl.do_thread(t);
1574 }
1575
1576 workers()->threads_do(&cl);
1577
1578 if (safepoint_workers() != nullptr) {
1579 safepoint_workers()->threads_do(&cl);
1580 }
1581 }
1582
1583 void ShenandoahHeap::tlabs_retire(bool resize) {
1584 assert(UseTLAB, "Only call with UseTLAB");
1585 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1586
1587 ThreadLocalAllocStats stats;
1588
1589 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1590 t->retire_tlab(&stats);
1591 if (resize) {
1592 t->tlab().resize();
1593 }
1594 }
1595
1596 stats.publish();
1597
1598 #ifdef ASSERT
1599 ShenandoahCheckCleanGCLABClosure cl;
1600 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1601 cl.do_thread(t);
1602 }
1603 workers()->threads_do(&cl);
1604 #endif
1605 }
1606
1607 void ShenandoahHeap::gclabs_retire(bool resize) {
1608 assert(UseTLAB, "Only call with UseTLAB");
1609 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1610
1611 ShenandoahRetireGCLABClosure cl(resize);
1612 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1613 cl.do_thread(t);
1614 }
1615
1616 workers()->threads_do(&cl);
1617
1618 if (safepoint_workers() != nullptr) {
1619 safepoint_workers()->threads_do(&cl);
1620 }
1621 }
1622
1623 // Returns size in bytes
1624 size_t ShenandoahHeap::unsafe_max_tlab_alloc() const {
1625 // Return the max allowed size, and let the allocation path
1626 // figure out the safe size for current allocation.
1627 return ShenandoahHeapRegion::max_tlab_size_bytes();
1628 }
1629
1630 size_t ShenandoahHeap::max_tlab_size() const {
1631 // Returns size in words
1632 return ShenandoahHeapRegion::max_tlab_size_words();
1633 }
1634
1635 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) {
1636 // These requests are ignored because we can't easily have Shenandoah jump into
1637 // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent
1638 // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly
1639 // on the VM thread, but this would confuse the control thread mightily and doesn't
1640 // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a
1641 // concurrent cycle in the prologue of the heap inspect/dump operation (see VM_HeapDumper::doit_prologue).
1642 // This is how other concurrent collectors in the JVM handle this scenario as well.
1643 assert(Thread::current()->is_VM_thread(), "Should be the VM thread");
1644 guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause");
1645 }
1646
1647 void ShenandoahHeap::collect(GCCause::Cause cause) {
1648 control_thread()->request_gc(cause);
1649 }
1650
1651 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1652 // This method is only called by `CollectedHeap::collect_as_vm_thread`, which we have
1653 // overridden to do nothing. See the comment there for an explanation of how heap inspections
1654 // work for Shenandoah.
1655 ShouldNotReachHere();
1656 }
1657
1658 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1659 ShenandoahHeapRegion* r = heap_region_containing(addr);
1660 if (r != nullptr) {
1661 return r->block_start(addr);
1662 }
1663 return nullptr;
1664 }
1665
1666 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1667 ShenandoahHeapRegion* r = heap_region_containing(addr);
1668 return r->block_is_obj(addr);
1669 }
1670
1671 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1672 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1673 }
1674
1675 void ShenandoahHeap::prepare_for_verify() {
1676 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1677 labs_make_parsable();
1678 }
1679 }
1680
1681 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1682 if (_shenandoah_policy->is_at_shutdown()) {
1683 return;
1684 }
1685
1686 if (_control_thread != nullptr) {
1687 tcl->do_thread(_control_thread);
1688 }
1689
1690 if (_uncommit_thread != nullptr) {
1691 tcl->do_thread(_uncommit_thread);
1692 }
1693
1694 workers()->threads_do(tcl);
1695 if (_safepoint_workers != nullptr) {
1696 _safepoint_workers->threads_do(tcl);
1697 }
1698 }
1699
1700 void ShenandoahHeap::print_tracing_info() const {
1701 LogTarget(Info, gc, stats) lt;
1702 if (lt.is_enabled()) {
1703 ResourceMark rm;
1704 LogStream ls(lt);
1705
1706 if (ShenandoahEvacTracking) {
1707 evac_tracker()->print_global_on(&ls);
1708 ls.cr();
1709 ls.cr();
1710 }
1711
1712 phase_timings()->print_global_on(&ls);
1713
1714 ls.cr();
1715 ls.cr();
1716
1717 shenandoah_policy()->print_gc_stats(&ls);
1718
1719 ls.cr();
1720 ls.cr();
1721 }
1722 }
1723
1724 // Active generation may only be set by the VM thread at a safepoint.
1725 void ShenandoahHeap::set_active_generation(ShenandoahGeneration* generation) {
1726 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1727 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1728 _active_generation = generation;
1729 }
1730
1731 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation,
1732 bool is_degenerated, bool is_out_of_cycle) {
1733 shenandoah_policy()->record_collection_cause(cause);
1734
1735 const GCCause::Cause current = gc_cause();
1736 assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s",
1737 GCCause::to_string(current), GCCause::to_string(cause));
1738
1739 set_gc_cause(cause);
1740
1741 if (is_degenerated) {
1742 generation->heuristics()->record_degenerated_cycle_start(is_out_of_cycle);
1743 } else {
1744 generation->heuristics()->record_cycle_start();
1745 }
1746 }
1747
1748 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1749 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1750
1751 generation->heuristics()->record_cycle_end();
1752 if (mode()->is_generational() && generation->is_global()) {
1753 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1754 young_generation()->heuristics()->record_cycle_end();
1755 old_generation()->heuristics()->record_cycle_end();
1756 }
1757
1758 set_gc_cause(GCCause::_no_gc);
1759 }
1760
1761 void ShenandoahHeap::verify(VerifyOption vo) {
1762 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1763 if (ShenandoahVerify) {
1764 verifier()->verify_generic(active_generation(), vo);
1765 } else {
1766 // TODO: Consider allocating verification bitmaps on demand,
1767 // and turn this on unconditionally.
1768 }
1769 }
1770 }
1771 size_t ShenandoahHeap::tlab_capacity() const {
1772 return _free_set->capacity_not_holding_lock();
1773 }
1774
1775 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1776 private:
1777 MarkBitMap* _bitmap;
1778 ShenandoahScanObjectStack* _oop_stack;
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 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(ON_PHANTOM_OOP_REF, obj, (T*)nullptr);
1786 if (obj == nullptr) {
1787 // Dead oop, cannot touch it.
1788 return;
1789 }
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) {}
1801 void do_oop(oop* p) { do_oop_work(p); }
1802 void do_oop(narrowOop* p) { do_oop_work(p); }
1803 };
1804
1805 /*
1806 * This is public API, used in preparation of object_iterate().
1807 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1808 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1809 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1810 */
1811 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1812 // No-op.
1813 }
1814
1815 /*
1816 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1817 *
1818 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1819 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1820 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1821 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1822 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1823 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1824 * wiped the bitmap in preparation for next marking).
1825 *
1826 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1827 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1828 * is allowed to report dead objects, but is not required to do so.
1829 */
1830 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1831 // Reset bitmap
1832 if (!prepare_aux_bitmap_for_iteration())
1833 return;
1834
1835 ShenandoahScanObjectStack oop_stack;
1836 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1837 // Seed the stack with root scan
1838 scan_roots_for_iteration(&oop_stack, &oops);
1839
1840 // Work through the oop stack to traverse heap
1841 while (! oop_stack.is_empty()) {
1842 oop obj = oop_stack.pop();
1843 assert(oopDesc::is_oop(obj), "must be a valid oop");
1844 cl->do_object(obj);
1845 obj->oop_iterate(&oops);
1846 }
1847
1848 assert(oop_stack.is_empty(), "should be empty");
1849 // Reclaim bitmap
1850 reclaim_aux_bitmap_for_iteration();
1851 }
1852
1853 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1854 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1855 if (!_aux_bitmap_region_special) {
1856 bool success = os::commit_memory((char *) _aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false);
1857 if (!success) {
1858 log_warning(gc)("Auxiliary marking bitmap commit failed: " PTR_FORMAT " (%zu bytes)",
1859 p2i(_aux_bitmap_region.start()), _aux_bitmap_region.byte_size());
1860 return false;
1861 }
1862 }
1863 _aux_bit_map.clear();
1864 return true;
1865 }
1866
1867 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1868 // Process GC roots according to current GC cycle
1869 // This populates the work stack with initial objects
1870 // It is important to relinquish the associated locks before diving
1871 // into heap dumper
1872 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1873 ShenandoahHeapIterationRootScanner rp(n_workers);
1874 rp.roots_do(oops);
1875 }
1876
1877 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1878 if (!_aux_bitmap_region_special) {
1879 os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size());
1880 }
1881 }
1882
1883 // Closure for parallelly iterate objects
1884 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1885 private:
1886 MarkBitMap* _bitmap;
1887 ShenandoahObjToScanQueue* _queue;
1888
1889 template <class T>
1890 void do_oop_work(T* p) {
1891 T o = RawAccess<>::oop_load(p);
1892 if (!CompressedOops::is_null(o)) {
1893 oop obj = CompressedOops::decode_not_null(o);
1894 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(ON_PHANTOM_OOP_REF, obj, (T*)nullptr);
1895 if (obj == nullptr) {
1896 // Dead oop, cannot touch it.
1897 return;
1898 }
1899 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1900 if (_bitmap->par_mark(obj)) {
1901 _queue->push(ShenandoahMarkTask(obj));
1902 }
1903 }
1904 }
1905 public:
1906 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1907 _bitmap(bitmap), _queue(q) {}
1908 void do_oop(oop* p) { do_oop_work(p); }
1909 void do_oop(narrowOop* p) { do_oop_work(p); }
1910 };
1911
1912 // Object iterator for parallel heap iteraion.
1913 // The root scanning phase happenes in construction as a preparation of
1914 // parallel marking queues.
1915 // Every worker processes it's own marking queue. work-stealing is used
1916 // to balance workload.
1917 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1918 private:
1919 uint _num_workers;
1920 bool _init_ready;
1921 MarkBitMap* _aux_bit_map;
1922 ShenandoahHeap* _heap;
1923 ShenandoahScanObjectStack _roots_stack; // global roots stack
1924 ShenandoahObjToScanQueueSet* _task_queues;
1925 public:
1926 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1927 _num_workers(num_workers),
1928 _init_ready(false),
1929 _aux_bit_map(bitmap),
1930 _heap(ShenandoahHeap::heap()) {
1931 // Initialize bitmap
1932 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1933 if (!_init_ready) {
1934 return;
1935 }
1936
1937 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1938 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1939
1940 _init_ready = prepare_worker_queues();
1941 }
1942
1943 ~ShenandoahParallelObjectIterator() {
1944 // Reclaim bitmap
1945 _heap->reclaim_aux_bitmap_for_iteration();
1946 // Reclaim queue for workers
1947 if (_task_queues!= nullptr) {
1948 for (uint i = 0; i < _num_workers; ++i) {
1949 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1950 if (q != nullptr) {
1951 delete q;
1952 _task_queues->register_queue(i, nullptr);
1953 }
1954 }
1955 delete _task_queues;
1956 _task_queues = nullptr;
1957 }
1958 }
1959
1960 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1961 if (_init_ready) {
1962 object_iterate_parallel(cl, worker_id, _task_queues);
1963 }
1964 }
1965
1966 private:
1967 // Divide global root_stack into worker queues
1968 bool prepare_worker_queues() {
1969 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1970 // Initialize queues for every workers
1971 for (uint i = 0; i < _num_workers; ++i) {
1972 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1973 _task_queues->register_queue(i, task_queue);
1974 }
1975 // Divide roots among the workers. Assume that object referencing distribution
1976 // is related with root kind, use round-robin to make every worker have same chance
1977 // to process every kind of roots
1978 size_t roots_num = _roots_stack.size();
1979 if (roots_num == 0) {
1980 // No work to do
1981 return false;
1982 }
1983
1984 for (uint j = 0; j < roots_num; j++) {
1985 uint stack_id = j % _num_workers;
1986 oop obj = _roots_stack.pop();
1987 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1988 }
1989 return true;
1990 }
1991
1992 void object_iterate_parallel(ObjectClosure* cl,
1993 uint worker_id,
1994 ShenandoahObjToScanQueueSet* queue_set) {
1995 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1996 assert(queue_set != nullptr, "task queue must not be null");
1997
1998 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1999 assert(q != nullptr, "object iterate queue must not be null");
2000
2001 ShenandoahMarkTask t;
2002 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
2003
2004 // Work through the queue to traverse heap.
2005 // Steal when there is no task in queue.
2006 while (q->pop(t) || queue_set->steal(worker_id, t)) {
2007 oop obj = t.obj();
2008 assert(oopDesc::is_oop(obj), "must be a valid oop");
2009 cl->do_object(obj);
2010 obj->oop_iterate(&oops);
2011 }
2012 assert(q->is_empty(), "should be empty");
2013 }
2014 };
2015
2016 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
2017 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
2018 }
2019
2020 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
2021 void ShenandoahHeap::keep_alive(oop obj) {
2022 ShenandoahBarrierSet::barrier_set()->keepalive_barrier(ON_STRONG_OOP_REF, (oop*)nullptr, obj, ShenandoahBarrierSet::FILTER_MARKED);
2023 }
2024
2025 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2026 for (size_t i = 0; i < num_regions(); i++) {
2027 ShenandoahHeapRegion* current = get_region(i);
2028 blk->heap_region_do(current);
2029 }
2030 }
2031
2032 class ShenandoahHeapRegionIteratorTask : public WorkerTask {
2033 private:
2034 ShenandoahRegionIterator _regions;
2035 ShenandoahHeapRegionClosure* _closure;
2036
2037 public:
2038 ShenandoahHeapRegionIteratorTask(ShenandoahHeapRegionClosure* closure)
2039 : WorkerTask("Shenandoah Heap Region Iterator")
2040 , _closure(closure) {}
2041
2042 void work(uint worker_id) override {
2043 ShenandoahParallelWorkerSession worker_session(worker_id);
2044 ShenandoahHeapRegion* region = _regions.next();
2045 while (region != nullptr) {
2046 _closure->heap_region_do(region);
2047 region = _regions.next();
2048 }
2049 }
2050 };
2051
2052 class ShenandoahParallelHeapRegionTask : public WorkerTask {
2053 private:
2054 ShenandoahHeap* const _heap;
2055 ShenandoahHeapRegionClosure* const _blk;
2056 size_t const _stride;
2057
2058 shenandoah_padding(0);
2059 Atomic<size_t> _index;
2060 shenandoah_padding(1);
2061
2062 public:
2063 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
2064 WorkerTask("Shenandoah Parallel Region Operation"),
2065 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
2066
2067 void work(uint worker_id) {
2068 ShenandoahParallelWorkerSession worker_session(worker_id);
2069 size_t stride = _stride;
2070
2071 size_t max = _heap->num_regions();
2072 while (_index.load_relaxed() < max) {
2073 size_t cur = _index.fetch_then_add(stride, memory_order_relaxed);
2074 size_t start = cur;
2075 size_t end = MIN2(cur + stride, max);
2076 if (start >= max) break;
2077
2078 for (size_t i = cur; i < end; i++) {
2079 ShenandoahHeapRegion* current = _heap->get_region(i);
2080 _blk->heap_region_do(current);
2081 }
2082 }
2083 }
2084 };
2085
2086 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2087 assert(blk->is_thread_safe(), "Only thread-safe closures here");
2088 const uint active_workers = workers()->active_workers();
2089 const size_t n_regions = num_regions();
2090 size_t stride = blk->parallel_region_stride();
2091 if (stride == 0 && active_workers > 1) {
2092 // Automatically derive the stride to balance the work between threads
2093 // evenly. Do not try to split work if below the reasonable threshold.
2094 constexpr size_t threshold = 4096;
2095 stride = n_regions <= threshold ?
2096 threshold :
2097 (n_regions + active_workers - 1) / active_workers;
2098 }
2099
2100 if (n_regions > stride && active_workers > 1) {
2101 ShenandoahParallelHeapRegionTask task(blk, stride);
2102 workers()->run_task(&task);
2103 } else {
2104 heap_region_iterate(blk);
2105 }
2106 }
2107
2108 void ShenandoahHeap::heap_region_iterator(ShenandoahHeapRegionClosure* closure) const {
2109 ShenandoahHeapRegionIteratorTask task(closure);
2110 workers()->run_task(&task);
2111 }
2112
2113 class ShenandoahRendezvousHandshakeClosure : public HandshakeClosure {
2114 public:
2115 inline ShenandoahRendezvousHandshakeClosure(const char* name) : HandshakeClosure(name) {}
2116 inline void do_thread(Thread* thread) {}
2117 };
2118
2119 void ShenandoahHeap::rendezvous_threads(const char* name) {
2120 ShenandoahRendezvousHandshakeClosure cl(name);
2121 Handshake::execute(&cl);
2122 }
2123
2124 void ShenandoahHeap::recycle_trash() {
2125 free_set()->recycle_trash();
2126 }
2127
2128 void ShenandoahHeap::do_class_unloading() {
2129 _unloader.unload();
2130 if (mode()->is_generational()) {
2131 old_generation()->set_parsable(false);
2132 }
2133 }
2134
2135 void ShenandoahHeap::stw_weak_refs(ShenandoahGeneration* generation, bool full_gc) {
2136 // Weak refs processing
2137 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2138 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2139 ShenandoahTimingsTracker t(phase);
2140 ShenandoahGCWorkerPhase worker_phase(phase);
2141 generation->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2142 }
2143
2144 void ShenandoahHeap::prepare_update_heap_references() {
2145 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2146
2147 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2148 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2149 // for future GCLABs here.
2150 if (UseTLAB) {
2151 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2152 gclabs_retire(ResizeTLAB);
2153 }
2154
2155 _update_refs_iterator.reset();
2156 }
2157
2158 void ShenandoahHeap::propagate_gc_state_to_all_threads() {
2159 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2160 if (_gc_state_changed) {
2161 // If we are only marking old, we do not need to process young pointers
2162 ShenandoahBarrierSet::satb_mark_queue_set().set_filter_out_young(
2163 is_concurrent_old_mark_in_progress() && !is_concurrent_young_mark_in_progress()
2164 );
2165 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
2166 Threads::threads_do(&propagator);
2167 _gc_state_changed = false;
2168 }
2169 }
2170
2171 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) {
2172 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2173 _gc_state.set_cond(mask, value);
2174 _gc_state_changed = true;
2175 }
2176
2177 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) {
2178 // Holding the thread lock here assures that any thread created after we change the gc
2179 // state will have the correct state. It also prevents attaching threads from seeing
2180 // an inconsistent state. See ShenandoahBarrierSet::on_thread_attach for reference. Established
2181 // threads will use their thread local copy of the gc state (changed by a handshake, or on a
2182 // safepoint).
2183 assert(Threads_lock->is_locked(), "Must hold thread lock for concurrent gc state change");
2184 _gc_state.set_cond(mask, value);
2185 }
2186
2187 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2188 uint mask;
2189 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2190 if (!in_progress && is_concurrent_old_mark_in_progress()) {
2191 assert(mode()->is_generational(), "Only generational GC has old marking");
2192 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2193 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2194 mask = YOUNG_MARKING;
2195 } else {
2196 mask = MARKING | YOUNG_MARKING;
2197 }
2198 set_gc_state_at_safepoint(mask, in_progress);
2199 manage_satb_barrier(in_progress);
2200 }
2201
2202 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2203 #ifdef ASSERT
2204 // has_forwarded_objects() iff UPDATE_REFS or EVACUATION
2205 bool has_forwarded = has_forwarded_objects();
2206 bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION);
2207 bool evacuating = _gc_state.is_set(EVACUATION);
2208 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2209 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2210 #endif
2211 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2212 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2213 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2214 set_gc_state_at_safepoint(OLD_MARKING, in_progress);
2215 } else {
2216 set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress);
2217 }
2218 manage_satb_barrier(in_progress);
2219 }
2220
2221 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2222 return old_generation()->is_preparing_for_mark();
2223 }
2224
2225 void ShenandoahHeap::manage_satb_barrier(bool active) {
2226 if (is_concurrent_mark_in_progress()) {
2227 // Ignore request to deactivate barrier while concurrent mark is in progress.
2228 // Do not attempt to re-activate the barrier if it is already active.
2229 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2230 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2231 }
2232 } else {
2233 // No concurrent marking is in progress so honor request to deactivate,
2234 // but only if the barrier is already active.
2235 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2236 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2237 }
2238 }
2239 }
2240
2241 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2242 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2243 set_gc_state_at_safepoint(EVACUATION, in_progress);
2244 }
2245
2246 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2247 if (in_progress) {
2248 _concurrent_strong_root_in_progress.set();
2249 } else {
2250 _concurrent_strong_root_in_progress.unset();
2251 }
2252 }
2253
2254 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2255 set_gc_state_at_safepoint(WEAK_ROOTS, cond);
2256 }
2257
2258 GCTracer* ShenandoahHeap::tracer() {
2259 return shenandoah_policy()->tracer();
2260 }
2261
2262 size_t ShenandoahHeap::tlab_used() const {
2263 return _free_set->used_not_holding_lock();
2264 }
2265
2266 bool ShenandoahHeap::try_cancel_gc(GCCause::Cause cause) {
2267 while (true) {
2268 const GCCause::Cause prev = _cancelled_gc.get();
2269 if (prev != GCCause::_no_gc && prev != GCCause::_shenandoah_concurrent_gc && cause != GCCause::_shenandoah_stop_vm) {
2270 // Only when the gc has not been cancelled, or it has been cancelled to interrupt an old marking cycle
2271 // do we allow the new cancellation request to happen. We make an exception for stopping the VM.
2272 return false;
2273 }
2274
2275 if (_cancelled_gc.cmpxchg(cause, prev) == prev) {
2276 return true;
2277 }
2278 }
2279 }
2280
2281 void ShenandoahHeap::cancel_concurrent_mark() {
2282 if (mode()->is_generational()) {
2283 young_generation()->cancel_marking();
2284 old_generation()->cancel_marking();
2285 }
2286
2287 global_generation()->cancel_marking();
2288
2289 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2290 }
2291
2292 bool ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2293 if (try_cancel_gc(cause)) {
2294 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2295 log_info(gc,thread)("%s", msg.buffer());
2296 Events::log(Thread::current(), "%s", msg.buffer());
2297 _cancel_requested_time = os::elapsedTime();
2298 return true;
2299 }
2300 return false;
2301 }
2302
2303 uint ShenandoahHeap::max_workers() {
2304 return _max_workers;
2305 }
2306
2307 void ShenandoahHeap::stop() {
2308 // The shutdown sequence should be able to terminate when GC is running.
2309
2310 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2311 _shenandoah_policy->record_shutdown();
2312
2313 // Step 1. Stop reporting on gc thread cpu utilization
2314 mmu_tracker()->stop();
2315
2316 // Step 2. Stop decaying allocation rate.
2317 _alloc_rate_decay.disenroll();
2318
2319 // Step 3. Wait until GC worker exits normally (this will cancel any ongoing GC).
2320 control_thread()->stop();
2321
2322 // Step 4. Shutdown uncommit thread.
2323 if (_uncommit_thread != nullptr) {
2324 _uncommit_thread->stop();
2325 }
2326 }
2327
2328 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2329 if (!unload_classes()) return;
2330 ClassUnloadingContext ctx(_workers->active_workers(),
2331 true /* unregister_nmethods_during_purge */,
2332 false /* lock_nmethod_free_separately */);
2333
2334 // Unload classes and purge SystemDictionary.
2335 {
2336 ShenandoahPhaseTimings::Phase phase = full_gc ?
2337 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2338 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2339 ShenandoahIsAliveSelector is_alive;
2340 {
2341 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2342 ShenandoahGCPhase gc_phase(phase);
2343 ShenandoahGCWorkerPhase worker_phase(phase);
2344 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2345
2346 ShenandoahClassUnloadingTask unlink_task(phase, unloading_occurred);
2347 _workers->run_task(&unlink_task);
2348 }
2349 // Release unloaded nmethods's memory.
2350 ClassUnloadingContext::context()->purge_and_free_nmethods();
2351 }
2352
2353 {
2354 ShenandoahGCPhase phase(full_gc ?
2355 ShenandoahPhaseTimings::full_gc_purge_cldg :
2356 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2357 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2358 }
2359 // Resize and verify metaspace
2360 MetaspaceGC::compute_new_size();
2361
2362 if (mode()->is_generational()) {
2363 old_generation()->set_parsable(false);
2364 }
2365
2366 DEBUG_ONLY(MetaspaceUtils::verify();)
2367 }
2368
2369 // Weak roots are either pre-evacuated (final mark) or updated (final update refs),
2370 // so they should not have forwarded oops.
2371 // However, we do need to "null" dead oops in the roots, if can not be done
2372 // in concurrent cycles.
2373 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2374 uint num_workers = _workers->active_workers();
2375 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2376 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2377 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2378 ShenandoahGCPhase phase(timing_phase);
2379 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2380 // Cleanup weak roots
2381 if (has_forwarded_objects()) {
2382 ShenandoahForwardedIsAliveClosure is_alive;
2383 ShenandoahNonConcUpdateRefsClosure keep_alive;
2384 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2385 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2386 _workers->run_task(&cleaning_task);
2387 } else {
2388 ShenandoahIsAliveClosure is_alive;
2389 #ifdef ASSERT
2390 ShenandoahAssertNotForwardedClosure verify_cl;
2391 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2392 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2393 #else
2394 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2395 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2396 #endif
2397 _workers->run_task(&cleaning_task);
2398 }
2399 }
2400
2401 void ShenandoahHeap::parallel_cleaning(ShenandoahGeneration* generation, bool full_gc) {
2402 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2403 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2404 ShenandoahGCPhase phase(full_gc ?
2405 ShenandoahPhaseTimings::full_gc_purge :
2406 ShenandoahPhaseTimings::degen_gc_purge);
2407 stw_weak_refs(generation, full_gc);
2408 stw_process_weak_roots(full_gc);
2409 stw_unload_classes(full_gc);
2410 }
2411
2412 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2413 set_gc_state_at_safepoint(HAS_FORWARDED, cond);
2414 }
2415
2416 void ShenandoahHeap::set_unload_classes(bool uc) {
2417 _unload_classes.set_cond(uc);
2418 }
2419
2420 bool ShenandoahHeap::unload_classes() const {
2421 return _unload_classes.is_set();
2422 }
2423
2424 address ShenandoahHeap::in_cset_fast_test_addr() {
2425 ShenandoahHeap* heap = ShenandoahHeap::heap();
2426 assert(heap->collection_set() != nullptr, "Sanity");
2427 return (address) heap->collection_set()->biased_map_address();
2428 }
2429
2430 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2431 _degenerated_gc_in_progress.set_cond(in_progress);
2432 }
2433
2434 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2435 _full_gc_in_progress.set_cond(in_progress);
2436 }
2437
2438 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2439 assert (is_full_gc_in_progress(), "should be");
2440 _full_gc_move_in_progress.set_cond(in_progress);
2441 }
2442
2443 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2444 set_gc_state_at_safepoint(UPDATE_REFS, in_progress);
2445 }
2446
2447 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2448 ShenandoahCodeRoots::register_nmethod(nm);
2449 }
2450
2451 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2452 ShenandoahCodeRoots::unregister_nmethod(nm);
2453 }
2454
2455 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2456 assert(thr == JavaThread::current(), "Sanity");
2457 size_t reg_idx_pin = heap_region_index_containing(o);
2458 size_t reg_idx_cached = ShenandoahThreadLocalData::pin_cache_region(thr);
2459 size_t count = ShenandoahThreadLocalData::pin_cache_count(thr);
2460 if (reg_idx_pin == reg_idx_cached) {
2461 ShenandoahThreadLocalData::pin_cache_set_count(thr, count + 1);
2462 } else {
2463 if (count != 0) {
2464 get_region(reg_idx_cached)->record_pin(count);
2465 }
2466 ShenandoahThreadLocalData::pin_cache_set_region(thr, reg_idx_pin);
2467 ShenandoahThreadLocalData::pin_cache_set_count(thr, 1);
2468 }
2469 }
2470
2471 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2472 assert(thr == JavaThread::current(), "Sanity");
2473 size_t reg_idx_pin = heap_region_index_containing(o);
2474 size_t reg_idx_cached = ShenandoahThreadLocalData::pin_cache_region(thr);
2475 if (reg_idx_pin == reg_idx_cached) {
2476 size_t count = ShenandoahThreadLocalData::pin_cache_count(thr);
2477 ShenandoahThreadLocalData::pin_cache_set_count(thr, count - 1);
2478 } else {
2479 get_region(reg_idx_pin)->record_unpin();
2480 }
2481 }
2482
2483 void ShenandoahHeap::flush_region_pin_cache(JavaThread* thr) {
2484 size_t count = ShenandoahThreadLocalData::pin_cache_count(thr);
2485 if (count != 0) {
2486 size_t reg_idx_cached = ShenandoahThreadLocalData::pin_cache_region(thr);
2487 get_region(reg_idx_cached)->record_pin(count);
2488 ShenandoahThreadLocalData::pin_cache_set_count(thr, 0);
2489 }
2490 }
2491
2492 void ShenandoahHeap::flush_region_pin_cache() {
2493 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2494 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
2495 flush_region_pin_cache(t);
2496 }
2497 }
2498
2499 void ShenandoahHeap::sync_pinned_region_status() {
2500 flush_region_pin_cache();
2501 ShenandoahHeapLocker locker(lock());
2502
2503 for (size_t i = 0; i < num_regions(); i++) {
2504 ShenandoahHeapRegion *r = get_region(i);
2505 if (r->is_active()) {
2506 if (r->is_pinned()) {
2507 if (r->pin_count() == 0) {
2508 r->make_unpinned();
2509 }
2510 } else {
2511 if (r->pin_count() > 0) {
2512 r->make_pinned();
2513 }
2514 }
2515 }
2516 }
2517
2518 assert_pinned_region_status();
2519 }
2520
2521 #ifdef ASSERT
2522 void ShenandoahHeap::assert_pinned_region_status() const {
2523 assert_pinned_region_status(global_generation());
2524 }
2525
2526 void ShenandoahHeap::assert_pinned_region_status(ShenandoahGeneration* generation) const {
2527 for (size_t i = 0; i < num_regions(); i++) {
2528 if (!generation->contains(region_affiliation(i))) {
2529 // Skip regions outside this generation
2530 continue;
2531 }
2532
2533 ShenandoahHeapRegion* r = get_region(i);
2534 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2535 "Region %zu pinning status is inconsistent", i);
2536 }
2537 }
2538 #endif
2539
2540 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2541 return _gc_timer;
2542 }
2543
2544 void ShenandoahHeap::prepare_concurrent_roots() {
2545 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2546 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2547 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2548 set_concurrent_weak_root_in_progress(true);
2549 if (unload_classes()) {
2550 _unloader.prepare();
2551 }
2552 }
2553
2554 void ShenandoahHeap::finish_concurrent_roots() {
2555 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2556 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2557 if (unload_classes()) {
2558 _unloader.finish();
2559 }
2560 }
2561
2562 #ifdef ASSERT
2563 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2564 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2565
2566 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2567 // Use ParallelGCThreads inside safepoints
2568 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2569 ParallelGCThreads, nworkers);
2570 } else {
2571 // Use ConcGCThreads outside safepoints
2572 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2573 ConcGCThreads, nworkers);
2574 }
2575 }
2576 #endif
2577
2578 ShenandoahVerifier* ShenandoahHeap::verifier() {
2579 guarantee(ShenandoahVerify, "Should be enabled");
2580 assert (_verifier != nullptr, "sanity");
2581 return _verifier;
2582 }
2583
2584 template<bool CONCURRENT>
2585 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2586 private:
2587 ShenandoahHeap* _heap;
2588 ShenandoahRegionIterator* _regions;
2589 public:
2590 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2591 WorkerTask("Shenandoah Update References"),
2592 _heap(ShenandoahHeap::heap()),
2593 _regions(regions) {
2594 }
2595
2596 void work(uint worker_id) {
2597 if (CONCURRENT) {
2598 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
2599 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2600 SuspendibleThreadSetJoiner stsj;
2601 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2602 } else {
2603 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
2604 ShenandoahParallelWorkerSession worker_session(worker_id);
2605 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2606 }
2607 }
2608
2609 private:
2610 template<class T>
2611 void do_work(uint worker_id) {
2612 if (CONCURRENT && (worker_id == 0)) {
2613 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2614 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2615 size_t cset_regions = _heap->collection_set()->count();
2616
2617 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2618 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2619 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2620 // next GC cycle.
2621 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2622 }
2623 // If !CONCURRENT, there's no value in expanding Mutator free set
2624 T cl;
2625 ShenandoahHeapRegion* r = _regions->next();
2626 while (r != nullptr) {
2627 HeapWord* update_watermark = r->get_update_watermark();
2628 assert (update_watermark >= r->bottom(), "sanity");
2629 if (r->is_active() && !r->is_cset()) {
2630 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2631 }
2632 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2633 return;
2634 }
2635 r = _regions->next();
2636 }
2637 }
2638 };
2639
2640 void ShenandoahHeap::update_heap_references(ShenandoahGeneration* generation, bool concurrent) {
2641 assert(generation->is_global(), "Should only get global generation here");
2642 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2643
2644 if (concurrent) {
2645 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2646 workers()->run_task(&task);
2647 } else {
2648 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2649 workers()->run_task(&task);
2650 }
2651 }
2652
2653 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2654 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2655 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2656
2657 {
2658 ShenandoahGCPhase phase(concurrent ?
2659 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2660 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2661
2662 final_update_refs_update_region_states();
2663
2664 assert_pinned_region_status();
2665 }
2666
2667 {
2668 ShenandoahGCPhase phase(concurrent ?
2669 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2670 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2671 trash_cset_regions();
2672 }
2673 }
2674
2675 void ShenandoahHeap::final_update_refs_update_region_states() {
2676 ShenandoahSynchronizePinnedRegionStates cl;
2677 parallel_heap_region_iterate(&cl);
2678 }
2679
2680 void ShenandoahHeap::rebuild_free_set_within_phase() {
2681 ShenandoahHeapLocker locker(lock());
2682 size_t young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count;
2683 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count);
2684 // If there are no old regions, first_old_region will be greater than last_old_region
2685 assert((first_old_region > last_old_region) ||
2686 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2687 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2688 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu",
2689 old_region_count, first_old_region, last_old_region);
2690
2691 if (mode()->is_generational()) {
2692 #ifdef ASSERT
2693 if (ShenandoahVerify) {
2694 verifier()->verify_before_rebuilding_free_set();
2695 }
2696 #endif
2697
2698 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2699 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2700 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2701 size_t allocation_runway =
2702 gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_trashed_regions);
2703 size_t max_transfer = MIN2(allocation_runway,
2704 (gen_heap->young_generation()->free_unaffiliated_regions() + young_trashed_regions) *
2705 ShenandoahHeapRegion::region_size_bytes());
2706 gen_heap->compute_old_generation_balance(max_transfer, old_trashed_regions, young_trashed_regions);
2707 }
2708 // Rebuild free set based on adjusted generation sizes.
2709 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, old_region_count);
2710
2711 if (mode()->is_generational()) {
2712 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2713 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2714 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2715 }
2716 }
2717
2718 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2719 ShenandoahGCPhase phase(concurrent ?
2720 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2721 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2722 rebuild_free_set_within_phase();
2723 }
2724
2725 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2726 size_t slice = r->index() / _bitmap_regions_per_slice;
2727
2728 size_t regions_from = _bitmap_regions_per_slice * slice;
2729 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2730 for (size_t g = regions_from; g < regions_to; g++) {
2731 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2732 if (skip_self && g == r->index()) continue;
2733 if (get_region(g)->is_committed()) {
2734 return true;
2735 }
2736 }
2737 return false;
2738 }
2739
2740 void ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2741 shenandoah_assert_heaplocked();
2742 assert(!is_bitmap_region_special(), "Not for special memory");
2743
2744 if (is_bitmap_slice_committed(r, true)) {
2745 // Some other region from the group is already committed, meaning the bitmap
2746 // slice is already committed, we exit right away.
2747 return;
2748 }
2749
2750 // Commit the bitmap slice:
2751 size_t slice = r->index() / _bitmap_regions_per_slice;
2752 size_t off = _bitmap_bytes_per_slice * slice;
2753 size_t len = _bitmap_bytes_per_slice;
2754 char* start = (char*) _bitmap_region.start() + off;
2755
2756 os::commit_memory_or_exit(start, len, false, "Unable to commit bitmap slice");
2757
2758 if (AlwaysPreTouch) {
2759 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2760 }
2761 }
2762
2763 void ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2764 shenandoah_assert_heaplocked();
2765 assert(!is_bitmap_region_special(), "Not for special memory");
2766
2767 if (is_bitmap_slice_committed(r, true)) {
2768 // Some other region from the group is still committed, meaning the bitmap
2769 // slice should stay committed, exit right away.
2770 return;
2771 }
2772
2773 // Uncommit the bitmap slice:
2774 size_t slice = r->index() / _bitmap_regions_per_slice;
2775 size_t off = _bitmap_bytes_per_slice * slice;
2776 size_t len = _bitmap_bytes_per_slice;
2777
2778 char* addr = (char*) _bitmap_region.start() + off;
2779 os::uncommit_memory(addr, len);
2780 }
2781
2782 void ShenandoahHeap::forbid_uncommit() {
2783 if (_uncommit_thread != nullptr) {
2784 _uncommit_thread->forbid_uncommit();
2785 }
2786 }
2787
2788 void ShenandoahHeap::allow_uncommit() {
2789 if (_uncommit_thread != nullptr) {
2790 _uncommit_thread->allow_uncommit();
2791 }
2792 }
2793
2794 #ifdef ASSERT
2795 bool ShenandoahHeap::is_uncommit_in_progress() {
2796 if (_uncommit_thread != nullptr) {
2797 return _uncommit_thread->is_uncommit_in_progress();
2798 }
2799 return false;
2800 }
2801 #endif
2802
2803 void ShenandoahHeap::safepoint_synchronize_begin() {
2804 StackWatermarkSet::safepoint_synchronize_begin();
2805 SuspendibleThreadSet::synchronize();
2806 }
2807
2808 void ShenandoahHeap::safepoint_synchronize_end() {
2809 SuspendibleThreadSet::desynchronize();
2810 }
2811
2812 void ShenandoahHeap::try_inject_alloc_failure() {
2813 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2814 _inject_alloc_failure.set();
2815 os::naked_short_sleep(1);
2816 if (cancelled_gc()) {
2817 log_info(gc)("Allocation failure was successfully injected");
2818 }
2819 }
2820 }
2821
2822 bool ShenandoahHeap::should_inject_alloc_failure() {
2823 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2824 }
2825
2826 void ShenandoahHeap::try_inject_pin() {
2827 assert(!ShenandoahSafepoint::is_at_shenandoah_safepoint(), "try_inject_pin() must be called outside a safepoint.");
2828 assert(active_generation() != nullptr, "Active generation must be set before we inject pins.");
2829 assert(is_concurrent_mark_in_progress() || active_generation()->is_mark_complete(),
2830 "try_inject_pin() requires marking is in progress or has completed.");
2831 if (ShenandoahPinRegionRate && !cancelled_gc() && ((uintx)(os::random() % 1000) < ShenandoahPinRegionRate) &&
2832 _injected_pin_count < MAX_INJECTED_PINS) {
2833 const size_t idx = os::random() % num_regions();
2834 ShenandoahHeapRegion* r = get_region(idx);
2835 if ((r->is_regular() || r->is_humongous_start()) && r->has_live()) {
2836 r->record_pin();
2837 _injected_pin_indices[_injected_pin_count] = idx;
2838 _injected_pin_count++;
2839 }
2840 }
2841 }
2842
2843 void ShenandoahHeap::release_injected_pins() {
2844 if (_injected_pin_count == 0) {
2845 return;
2846 }
2847
2848 assert(_injected_pin_count <= MAX_INJECTED_PINS,
2849 "Injected pin count: %u exceeds max: %u.", _injected_pin_count, MAX_INJECTED_PINS);
2850 for (uint i = 0; i < _injected_pin_count; i++) {
2851 const size_t idx = _injected_pin_indices[i];
2852 ShenandoahHeapRegion* r = get_region(idx);
2853 assert(r->pin_count() > 0, "Region %zu in tracker must contain a pin.", idx);
2854 r->record_unpin();
2855 }
2856 _injected_pin_count = 0;
2857 }
2858
2859 void ShenandoahHeap::initialize_serviceability() {
2860 _memory_pool = new ShenandoahMemoryPool(this);
2861 _cycle_memory_manager.add_pool(_memory_pool);
2862 _stw_memory_manager.add_pool(_memory_pool);
2863 }
2864
2865 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2866 GrowableArray<GCMemoryManager*> memory_managers(2);
2867 memory_managers.append(&_cycle_memory_manager);
2868 memory_managers.append(&_stw_memory_manager);
2869 return memory_managers;
2870 }
2871
2872 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2873 GrowableArray<MemoryPool*> memory_pools(1);
2874 memory_pools.append(_memory_pool);
2875 return memory_pools;
2876 }
2877
2878 MemoryUsage ShenandoahHeap::memory_usage() {
2879 return shenandoah_memory_usage(_initial_size, used(), committed(), max_capacity());
2880 }
2881
2882 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2883 _heap(ShenandoahHeap::heap()),
2884 _index(0) {}
2885
2886 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2887 _heap(heap),
2888 _index(0) {}
2889
2890 void ShenandoahRegionIterator::reset() {
2891 _index.store_relaxed(0);
2892 }
2893
2894 bool ShenandoahRegionIterator::has_next() const {
2895 return _index.load_relaxed() < _heap->num_regions();
2896 }
2897
2898 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2899 #ifdef ASSERT
2900 assert(_liveness_cache != nullptr, "sanity");
2901 assert(worker_id < _max_workers, "sanity");
2902 for (uint i = 0; i < num_regions(); i++) {
2903 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2904 }
2905 #endif
2906 return _liveness_cache[worker_id];
2907 }
2908
2909 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2910 assert(worker_id < _max_workers, "sanity");
2911 assert(_liveness_cache != nullptr, "sanity");
2912 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2913 for (uint i = 0; i < num_regions(); i++) {
2914 ShenandoahLiveData live = ld[i];
2915 if (live > 0) {
2916 ShenandoahHeapRegion* r = get_region(i);
2917 r->increase_live_data_gc_words(live);
2918 ld[i] = 0;
2919 }
2920 }
2921 }
2922
2923 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2924 // Can not guarantee obj is deeply good.
2925 if (has_forwarded_objects()) {
2926 return true;
2927 }
2928
2929 // Objects allocated after marking start are implicitly alive.
2930 if (is_concurrent_mark_in_progress() &&
2931 !marking_context()->allocated_after_mark_start(obj)) {
2932 return true;
2933 }
2934
2935 // Nmethods referenced by stack chunk may need the barrier fixups.
2936 if (ShenandoahStackChunkGCData::is_different_epoch(obj)) {
2937 return true;
2938 }
2939
2940 return false;
2941 }
2942
2943 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2944 #if INCLUDE_CDS_JAVA_HEAP
2945 // CDS wants a raw continuous memory range to load a bunch of objects itself.
2946 // This is an unusual request, since all requested regions should be regular, not humongous.
2947 //
2948 // CDS would guarantee no objects straddle multiple regions, as long as regions are as large
2949 // as MIN_GC_REGION_ALIGNMENT.
2950 guarantee(ShenandoahHeapRegion::region_size_bytes() >= AOTMappedHeapWriter::MIN_GC_REGION_ALIGNMENT, "Must be");
2951
2952 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_cds(size);
2953 return allocate_memory(req);
2954 #else
2955 assert(false, "Archive heap loader should not be available, should not be here");
2956 return nullptr;
2957 #endif // INCLUDE_CDS_JAVA_HEAP
2958 }
2959
2960 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2961 // Nothing to do here, except checking that heap looks fine.
2962 #ifdef ASSERT
2963 HeapWord* start = archive_space.start();
2964 HeapWord* end = archive_space.end();
2965
2966 // No unclaimed space between the objects.
2967 // Objects are properly allocated in correct regions.
2968 HeapWord* cur = start;
2969 while (cur < end) {
2970 oop oop = cast_to_oop(cur);
2971 shenandoah_assert_in_correct_region(nullptr, oop);
2972 cur += oop->size();
2973 }
2974
2975 // No unclaimed tail at the end of archive space.
2976 assert(cur == end,
2977 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2978 p2i(cur), p2i(end));
2979
2980 // All regions in contiguous space have good state.
2981 size_t begin_reg_idx = heap_region_index_containing(start);
2982 size_t end_reg_idx = heap_region_index_containing(end);
2983
2984 for (size_t idx = begin_reg_idx; idx <= end_reg_idx; idx++) {
2985 ShenandoahHeapRegion* r = get_region(idx);
2986 assert(r->is_regular(), "Must be regular");
2987 assert(r->is_young(), "Must be young");
2988 assert(idx == end_reg_idx || r->top() == r->end(),
2989 "All regions except the last one should be full: " PTR_FORMAT " " PTR_FORMAT,
2990 p2i(r->top()), p2i(r->end()));
2991 assert(idx != begin_reg_idx || r->bottom() == start,
2992 "Archive space start should be at the bottom of first region: " PTR_FORMAT " " PTR_FORMAT,
2993 p2i(r->bottom()), p2i(start));
2994 assert(idx != end_reg_idx || r->top() == end,
2995 "Archive space end should be at the top of last region: " PTR_FORMAT " " PTR_FORMAT,
2996 p2i(r->top()), p2i(end));
2997 }
2998
2999 #endif
3000 }
3001
3002 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
3003 if (!mode()->is_generational()) {
3004 return global_generation();
3005 } else if (affiliation == YOUNG_GENERATION) {
3006 return young_generation();
3007 } else if (affiliation == OLD_GENERATION) {
3008 return old_generation();
3009 }
3010
3011 ShouldNotReachHere();
3012 return nullptr;
3013 }
3014
3015 void ShenandoahHeap::log_heap_status(const char* msg) const {
3016 if (mode()->is_generational()) {
3017 young_generation()->log_status(msg);
3018 old_generation()->log_status(msg);
3019 } else {
3020 global_generation()->log_status(msg);
3021 }
3022 }
3023
3024 ShenandoahHeapLocker::ShenandoahHeapLocker(ShenandoahHeapLock* lock, bool allow_block_for_safepoint) : _lock(lock) {
3025 #ifdef ASSERT
3026 ShenandoahFreeSet* free_set = ShenandoahHeap::heap()->free_set();
3027 // free_set is nullptr only at pre-initialized state
3028 assert(free_set == nullptr || !free_set->rebuild_lock()->owned_by_self(), "Dead lock, can't acquire heap lock while holding free-set rebuild lock");
3029 assert(_lock != nullptr, "Must not");
3030 #endif
3031 _lock->lock(allow_block_for_safepoint);
3032 }