1 /*
2 * Copyright (c) 2023, 2025, 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.inline.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/shenandoahAllocRequest.hpp"
46 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
47 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
48 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
49 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
50 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
51 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
52 #include "gc/shenandoah/shenandoahControlThread.hpp"
53 #include "gc/shenandoah/shenandoahFreeSet.hpp"
54 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp"
55 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
56 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
57 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
58 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
59 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
60 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
61 #include "gc/shenandoah/shenandoahInitLogger.hpp"
62 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
63 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
64 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
65 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
66 #include "gc/shenandoah/shenandoahPadding.hpp"
67 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
68 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
69 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
70 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
71 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
72 #include "gc/shenandoah/shenandoahSTWMark.hpp"
73 #include "gc/shenandoah/shenandoahUncommitThread.hpp"
74 #include "gc/shenandoah/shenandoahUtils.hpp"
75 #include "gc/shenandoah/shenandoahVerifier.hpp"
76 #include "gc/shenandoah/shenandoahVMOperations.hpp"
77 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
78 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
79 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
80 #include "memory/allocation.hpp"
81 #include "memory/classLoaderMetaspace.hpp"
82 #include "memory/memoryReserver.hpp"
83 #include "memory/metaspaceUtils.hpp"
84 #include "memory/universe.hpp"
85 #include "nmt/mallocTracker.hpp"
86 #include "nmt/memTracker.hpp"
87 #include "oops/compressedOops.inline.hpp"
88 #include "prims/jvmtiTagMap.hpp"
89 #include "runtime/atomic.hpp"
90 #include "runtime/atomicAccess.hpp"
91 #include "runtime/globals.hpp"
92 #include "runtime/interfaceSupport.inline.hpp"
93 #include "runtime/java.hpp"
94 #include "runtime/orderAccess.hpp"
95 #include "runtime/safepointMechanism.hpp"
96 #include "runtime/stackWatermarkSet.hpp"
97 #include "runtime/threads.hpp"
98 #include "runtime/vmThread.hpp"
99 #include "utilities/events.hpp"
100 #include "utilities/globalDefinitions.hpp"
101 #include "utilities/powerOfTwo.hpp"
102 #if INCLUDE_JVMCI
103 #include "jvmci/jvmci.hpp"
104 #endif
105 #if INCLUDE_JFR
106 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
107 #endif
108
109 class ShenandoahPretouchHeapTask : public WorkerTask {
110 private:
111 ShenandoahRegionIterator _regions;
112 const size_t _page_size;
113 public:
114 ShenandoahPretouchHeapTask(size_t page_size) :
115 WorkerTask("Shenandoah Pretouch Heap"),
116 _page_size(page_size) {}
117
118 virtual void work(uint worker_id) {
119 ShenandoahHeapRegion* r = _regions.next();
120 while (r != nullptr) {
121 if (r->is_committed()) {
122 os::pretouch_memory(r->bottom(), r->end(), _page_size);
123 }
124 r = _regions.next();
125 }
126 }
127 };
128
129 class ShenandoahPretouchBitmapTask : public WorkerTask {
130 private:
131 ShenandoahRegionIterator _regions;
132 char* _bitmap_base;
133 const size_t _bitmap_size;
134 const size_t _page_size;
135 public:
136 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
137 WorkerTask("Shenandoah Pretouch Bitmap"),
138 _bitmap_base(bitmap_base),
139 _bitmap_size(bitmap_size),
140 _page_size(page_size) {}
141
142 virtual void work(uint worker_id) {
143 ShenandoahHeapRegion* r = _regions.next();
144 while (r != nullptr) {
145 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
146 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
147 assert (end <= _bitmap_size, "end is sane: %zu < %zu", end, _bitmap_size);
148
149 if (r->is_committed()) {
150 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
151 }
152
153 r = _regions.next();
154 }
155 }
156 };
157
158 static ReservedSpace reserve(size_t size, size_t preferred_page_size) {
159 // When a page size is given we don't want to mix large
160 // and normal pages. If the size is not a multiple of the
161 // page size it will be aligned up to achieve this.
162 size_t alignment = os::vm_allocation_granularity();
163 if (preferred_page_size != os::vm_page_size()) {
164 alignment = MAX2(preferred_page_size, alignment);
165 size = align_up(size, alignment);
166 }
167
168 const ReservedSpace reserved = MemoryReserver::reserve(size, alignment, preferred_page_size, mtGC);
169 if (!reserved.is_reserved()) {
170 vm_exit_during_initialization("Could not reserve space");
171 }
172 return reserved;
173 }
174
175 jint ShenandoahHeap::initialize() {
176 //
177 // Figure out heap sizing
178 //
179
180 size_t init_byte_size = InitialHeapSize;
181 size_t min_byte_size = MinHeapSize;
182 size_t max_byte_size = MaxHeapSize;
183 size_t heap_alignment = HeapAlignment;
184
185 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
186
187 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
188 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
189
190 _num_regions = ShenandoahHeapRegion::region_count();
191 assert(_num_regions == (max_byte_size / reg_size_bytes),
192 "Regions should cover entire heap exactly: %zu != %zu/%zu",
193 _num_regions, max_byte_size, reg_size_bytes);
194
195 size_t num_committed_regions = init_byte_size / reg_size_bytes;
196 num_committed_regions = MIN2(num_committed_regions, _num_regions);
197 assert(num_committed_regions <= _num_regions, "sanity");
198 _initial_size = num_committed_regions * reg_size_bytes;
199
200 size_t num_min_regions = min_byte_size / reg_size_bytes;
201 num_min_regions = MIN2(num_min_regions, _num_regions);
202 assert(num_min_regions <= _num_regions, "sanity");
203 _minimum_size = num_min_regions * reg_size_bytes;
204
205 _soft_max_size.store_relaxed(clamp(SoftMaxHeapSize, min_capacity(), max_capacity()));
206
207 _committed.store_relaxed(_initial_size);
208
209 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
210 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
211 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
212
213 //
214 // Reserve and commit memory for heap
215 //
216
217 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
218 initialize_reserved_region(heap_rs);
219 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
220 _heap_region_special = heap_rs.special();
221
222 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
223 "Misaligned heap: " PTR_FORMAT, p2i(base()));
224 os::trace_page_sizes_for_requested_size("Heap",
225 max_byte_size, heap_alignment,
226 heap_rs.base(),
227 heap_rs.size(), heap_rs.page_size());
228
229 #if SHENANDOAH_OPTIMIZED_MARKTASK
230 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
231 // Fail if we ever attempt to address more than we can.
232 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
233 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
234 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
235 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
236 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
237 vm_exit_during_initialization("Fatal Error", buf);
238 }
239 #endif
240
241 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
242 if (!_heap_region_special) {
243 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
244 "Cannot commit heap memory");
245 }
246
247 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
248
249 // Now we know the number of regions and heap sizes, initialize the heuristics.
250 initialize_heuristics();
251
252 // If ShenandoahCardBarrier is enabled but it's not generational mode
253 // it means we're under passive mode and we have to initialize old gen
254 // for the purpose of having card table.
255 if (ShenandoahCardBarrier && !(mode()->is_generational())) {
256 _old_generation = new ShenandoahOldGeneration(max_workers());
257 }
258
259 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
260
261 //
262 // Worker threads must be initialized after the barrier is configured
263 //
264 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
265 if (_workers == nullptr) {
266 vm_exit_during_initialization("Failed necessary allocation.");
267 } else {
268 _workers->initialize_workers();
269 }
270
271 if (ParallelGCThreads > 1) {
272 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
273 _safepoint_workers->initialize_workers();
274 }
275
276 //
277 // Reserve and commit memory for bitmap(s)
278 //
279
280 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
281 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
282
283 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
284
285 guarantee(bitmap_bytes_per_region != 0,
286 "Bitmap bytes per region should not be zero");
287 guarantee(is_power_of_2(bitmap_bytes_per_region),
288 "Bitmap bytes per region should be power of two: %zu", bitmap_bytes_per_region);
289
290 if (bitmap_page_size > bitmap_bytes_per_region) {
291 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
292 _bitmap_bytes_per_slice = bitmap_page_size;
293 } else {
294 _bitmap_regions_per_slice = 1;
295 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
296 }
297
298 guarantee(_bitmap_regions_per_slice >= 1,
299 "Should have at least one region per slice: %zu",
300 _bitmap_regions_per_slice);
301
302 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
303 "Bitmap slices should be page-granular: bps = %zu, page size = %zu",
304 _bitmap_bytes_per_slice, bitmap_page_size);
305
306 ReservedSpace bitmap = reserve(_bitmap_size, bitmap_page_size);
307 os::trace_page_sizes_for_requested_size("Mark Bitmap",
308 bitmap_size_orig, bitmap_page_size,
309 bitmap.base(),
310 bitmap.size(), bitmap.page_size());
311 MemTracker::record_virtual_memory_tag(bitmap, mtGC);
312 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
313 _bitmap_region_special = bitmap.special();
314
315 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
316 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
317 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
318 if (!_bitmap_region_special) {
319 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
320 "Cannot commit bitmap memory");
321 }
322
323 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
324
325 if (ShenandoahVerify) {
326 ReservedSpace verify_bitmap = reserve(_bitmap_size, bitmap_page_size);
327 os::trace_page_sizes_for_requested_size("Verify Bitmap",
328 bitmap_size_orig, bitmap_page_size,
329 verify_bitmap.base(),
330 verify_bitmap.size(), verify_bitmap.page_size());
331 if (!verify_bitmap.special()) {
332 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
333 "Cannot commit verification bitmap memory");
334 }
335 MemTracker::record_virtual_memory_tag(verify_bitmap, mtGC);
336 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
337 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
338 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
339 }
340
341 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
342 size_t aux_bitmap_page_size = bitmap_page_size;
343
344 ReservedSpace aux_bitmap = reserve(_bitmap_size, aux_bitmap_page_size);
345 os::trace_page_sizes_for_requested_size("Aux Bitmap",
346 bitmap_size_orig, aux_bitmap_page_size,
347 aux_bitmap.base(),
348 aux_bitmap.size(), aux_bitmap.page_size());
349 MemTracker::record_virtual_memory_tag(aux_bitmap, mtGC);
350 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
351 _aux_bitmap_region_special = aux_bitmap.special();
352 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
353
354 //
355 // Create regions and region sets
356 //
357 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
358 size_t region_storage_size_orig = region_align * _num_regions;
359 size_t region_storage_size = align_up(region_storage_size_orig,
360 MAX2(region_page_size, os::vm_allocation_granularity()));
361
362 ReservedSpace region_storage = reserve(region_storage_size, region_page_size);
363 os::trace_page_sizes_for_requested_size("Region Storage",
364 region_storage_size_orig, region_page_size,
365 region_storage.base(),
366 region_storage.size(), region_storage.page_size());
367 MemTracker::record_virtual_memory_tag(region_storage, mtGC);
368 if (!region_storage.special()) {
369 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
370 "Cannot commit region memory");
371 }
372
373 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
374 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
375 // If not successful, bite a bullet and allocate at whatever address.
376 {
377 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
378 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
379 const size_t cset_page_size = os::vm_page_size();
380
381 uintptr_t min = round_up_power_of_2(cset_align);
382 uintptr_t max = (1u << 30u);
383 ReservedSpace cset_rs;
384
385 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
386 char* req_addr = (char*)addr;
387 assert(is_aligned(req_addr, cset_align), "Should be aligned");
388 cset_rs = MemoryReserver::reserve(req_addr, cset_size, cset_align, cset_page_size, mtGC);
389 if (cset_rs.is_reserved()) {
390 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
391 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
392 break;
393 }
394 }
395
396 if (_collection_set == nullptr) {
397 cset_rs = MemoryReserver::reserve(cset_size, cset_align, os::vm_page_size(), mtGC);
398 if (!cset_rs.is_reserved()) {
399 vm_exit_during_initialization("Cannot reserve memory for collection set");
400 }
401
402 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
403 }
404 os::trace_page_sizes_for_requested_size("Collection Set",
405 cset_size, cset_page_size,
406 cset_rs.base(),
407 cset_rs.size(), cset_rs.page_size());
408 }
409
410 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
411 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
412
413 {
414 ShenandoahHeapLocker locker(lock());
415 for (size_t i = 0; i < _num_regions; i++) {
416 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
417 bool is_committed = i < num_committed_regions;
418 void* loc = region_storage.base() + i * region_align;
419
420 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
421 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
422
423 _marking_context->initialize_top_at_mark_start(r);
424 _regions[i] = r;
425 assert(!collection_set()->is_in(i), "New region should not be in collection set");
426
427 _affiliations[i] = ShenandoahAffiliation::FREE;
428 }
429
430 if (mode()->is_generational()) {
431 size_t young_reserve = (soft_max_capacity() * ShenandoahEvacReserve) / 100;
432 young_generation()->set_evacuation_reserve(young_reserve);
433 old_generation()->set_evacuation_reserve((size_t) 0);
434 old_generation()->set_promoted_reserve((size_t) 0);
435 }
436
437 _free_set = new ShenandoahFreeSet(this, _num_regions);
438 initialize_generations();
439
440 // We are initializing free set. We ignore cset region tallies.
441 size_t young_trashed_regions, old_trashed_regions, first_old, last_old, num_old;
442 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old, last_old, num_old);
443 if (mode()->is_generational()) {
444 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
445 // We cannot call
446 // gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions)
447 // until after the heap is fully initialized. So we make up a safe value here.
448 size_t allocation_runway = InitialHeapSize / 2;
449 gen_heap->compute_old_generation_balance(allocation_runway, old_trashed_regions, young_trashed_regions);
450 }
451 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, num_old);
452 }
453
454 if (AlwaysPreTouch) {
455 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
456 // before initialize() below zeroes it with initializing thread. For any given region,
457 // we touch the region and the corresponding bitmaps from the same thread.
458 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
459
460 _pretouch_heap_page_size = heap_page_size;
461 _pretouch_bitmap_page_size = bitmap_page_size;
462
463 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
464 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
465
466 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
467 _workers->run_task(&bcl);
468
469 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
470 _workers->run_task(&hcl);
471 }
472
473 //
474 // Initialize the rest of GC subsystems
475 //
476
477 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
478 for (uint worker = 0; worker < _max_workers; worker++) {
479 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
480 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
481 }
482
483 // There should probably be Shenandoah-specific options for these,
484 // just as there are G1-specific options.
485 {
486 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
487 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
488 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
489 }
490
491 _monitoring_support = new ShenandoahMonitoringSupport(this);
492 _phase_timings = new ShenandoahPhaseTimings(max_workers());
493 ShenandoahCodeRoots::initialize();
494
495 // Initialization of controller makes use of variables established by initialize_heuristics.
496 initialize_controller();
497
498 // Certain initialization of heuristics must be deferred until after controller is initialized.
499 post_initialize_heuristics();
500 start_idle_span();
501 if (ShenandoahUncommit) {
502 _uncommit_thread = new ShenandoahUncommitThread(this);
503 }
504 print_init_logger();
505 FullGCForwarding::initialize(_heap_region);
506 return JNI_OK;
507 }
508
509 void ShenandoahHeap::initialize_controller() {
510 _control_thread = new ShenandoahControlThread();
511 }
512
513 void ShenandoahHeap::print_init_logger() const {
514 ShenandoahInitLogger::print();
515 }
516
517 void ShenandoahHeap::initialize_mode() {
518 if (ShenandoahGCMode != nullptr) {
519 if (strcmp(ShenandoahGCMode, "satb") == 0) {
520 _gc_mode = new ShenandoahSATBMode();
521 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
522 _gc_mode = new ShenandoahPassiveMode();
523 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
524 _gc_mode = new ShenandoahGenerationalMode();
525 } else {
526 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
527 }
528 } else {
529 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
530 }
531 _gc_mode->initialize_flags();
532 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
533 vm_exit_during_initialization(
534 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
535 _gc_mode->name()));
536 }
537 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
538 vm_exit_during_initialization(
539 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
540 _gc_mode->name()));
541 }
542 }
543
544 void ShenandoahHeap::initialize_heuristics() {
545 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers());
546 _global_generation->initialize_heuristics(mode());
547 }
548
549 #ifdef _MSC_VER
550 #pragma warning( push )
551 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
552 #endif
553
554 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
555 CollectedHeap(),
556 _active_generation(nullptr),
557 _initial_size(0),
558 _committed(0),
559 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
560 _workers(nullptr),
561 _safepoint_workers(nullptr),
562 _heap_region_special(false),
563 _num_regions(0),
564 _regions(nullptr),
565 _affiliations(nullptr),
566 _gc_state_changed(false),
567 _gc_no_progress_count(0),
568 _cancel_requested_time(0),
569 _update_refs_iterator(this),
570 _global_generation(nullptr),
571 _control_thread(nullptr),
572 _uncommit_thread(nullptr),
573 _young_generation(nullptr),
574 _old_generation(nullptr),
575 _shenandoah_policy(policy),
576 _gc_mode(nullptr),
577 _free_set(nullptr),
578 _verifier(nullptr),
579 _phase_timings(nullptr),
580 _monitoring_support(nullptr),
581 _memory_pool(nullptr),
582 _stw_memory_manager("Shenandoah Pauses"),
583 _cycle_memory_manager("Shenandoah Cycles"),
584 _gc_timer(new ConcurrentGCTimer()),
585 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
586 _marking_context(nullptr),
587 _bitmap_size(0),
588 _bitmap_regions_per_slice(0),
589 _bitmap_bytes_per_slice(0),
590 _bitmap_region_special(false),
591 _aux_bitmap_region_special(false),
592 _liveness_cache(nullptr),
593 _collection_set(nullptr),
594 _evac_tracker(new ShenandoahEvacuationTracker())
595 {
596 // Initialize GC mode early, many subsequent initialization procedures depend on it
597 initialize_mode();
598 _cancelled_gc.set(GCCause::_no_gc);
599 }
600
601 #ifdef _MSC_VER
602 #pragma warning( pop )
603 #endif
604
605 void ShenandoahHeap::print_heap_on(outputStream* st) const {
606 const bool is_generational = mode()->is_generational();
607 const char* front_spacing = "";
608 if (is_generational) {
609 st->print_cr("Generational Shenandoah Heap");
610 st->print_cr(" Young:");
611 st->print_cr(" " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(young_generation()->max_capacity()), PROPERFMTARGS(young_generation()->used()));
612 st->print_cr(" Old:");
613 st->print_cr(" " PROPERFMT " max, " PROPERFMT " used", PROPERFMTARGS(old_generation()->max_capacity()), PROPERFMTARGS(old_generation()->used()));
614 st->print_cr(" Entire heap:");
615 st->print_cr(" " PROPERFMT " soft max, " PROPERFMT " committed",
616 PROPERFMTARGS(soft_max_capacity()), PROPERFMTARGS(committed()));
617 front_spacing = " ";
618 } else {
619 st->print_cr("Shenandoah Heap");
620 st->print_cr(" " PROPERFMT " max, " PROPERFMT " soft max, " PROPERFMT " committed, " PROPERFMT " used",
621 PROPERFMTARGS(max_capacity()),
622 PROPERFMTARGS(soft_max_capacity()),
623 PROPERFMTARGS(committed()),
624 PROPERFMTARGS(used())
625 );
626 }
627 st->print_cr("%s %zu x " PROPERFMT " regions",
628 front_spacing,
629 num_regions(),
630 PROPERFMTARGS(ShenandoahHeapRegion::region_size_bytes()));
631
632 st->print("Status: ");
633 if (has_forwarded_objects()) st->print("has forwarded objects, ");
634 if (!is_generational) {
635 if (is_concurrent_mark_in_progress()) st->print("marking,");
636 } else {
637 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
638 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
639 }
640 if (is_evacuation_in_progress()) st->print("evacuating, ");
641 if (is_update_refs_in_progress()) st->print("updating refs, ");
642 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
643 if (is_full_gc_in_progress()) st->print("full gc, ");
644 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
645 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
646 if (is_concurrent_strong_root_in_progress() &&
647 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
648
649 if (cancelled_gc()) {
650 st->print("cancelled");
651 } else {
652 st->print("not cancelled");
653 }
654 st->cr();
655
656 st->print_cr("Reserved region:");
657 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
658 p2i(reserved_region().start()),
659 p2i(reserved_region().end()));
660
661 ShenandoahCollectionSet* cset = collection_set();
662 st->print_cr("Collection set:");
663 if (cset != nullptr) {
664 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
665 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
666 } else {
667 st->print_cr(" (null)");
668 }
669
670 st->cr();
671
672 if (Verbose) {
673 st->cr();
674 print_heap_regions_on(st);
675 }
676 }
677
678 void ShenandoahHeap::print_gc_on(outputStream* st) const {
679 print_heap_regions_on(st);
680 }
681
682 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
683 public:
684 void do_thread(Thread* thread) {
685 assert(thread != nullptr, "Sanity");
686 ShenandoahThreadLocalData::initialize_gclab(thread);
687 }
688 };
689
690 void ShenandoahHeap::initialize_generations() {
691 _global_generation->post_initialize(this);
692 }
693
694 // We do not call this explicitly It is called by Hotspot infrastructure.
695 void ShenandoahHeap::post_initialize() {
696 CollectedHeap::post_initialize();
697
698 check_soft_max_changed();
699
700 // Schedule periodic task to report on gc thread CPU utilization
701 _mmu_tracker.initialize();
702
703 MutexLocker ml(Threads_lock);
704
705 ShenandoahInitWorkerGCLABClosure init_gclabs;
706 _workers->threads_do(&init_gclabs);
707
708 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
709 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
710 _workers->set_initialize_gclab();
711
712 // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump
713 // during a concurrent evacuation phase.
714 if (_safepoint_workers != nullptr) {
715 _safepoint_workers->threads_do(&init_gclabs);
716 _safepoint_workers->set_initialize_gclab();
717 }
718
719 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
720 }
721
722 void ShenandoahHeap::post_initialize_heuristics() {
723 _global_generation->post_initialize_heuristics();
724 }
725
726 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
727 return _global_generation->heuristics();
728 }
729
730 size_t ShenandoahHeap::used() const {
731 return global_generation()->used();
732 }
733
734 size_t ShenandoahHeap::committed() const {
735 return _committed.load_relaxed();
736 }
737
738 void ShenandoahHeap::increase_committed(size_t bytes) {
739 shenandoah_assert_heaplocked_or_safepoint();
740 _committed.fetch_then_add(bytes, memory_order_relaxed);
741 }
742
743 void ShenandoahHeap::decrease_committed(size_t bytes) {
744 shenandoah_assert_heaplocked_or_safepoint();
745 _committed.fetch_then_sub(bytes, memory_order_relaxed);
746 }
747
748 size_t ShenandoahHeap::capacity() const {
749 return committed();
750 }
751
752 size_t ShenandoahHeap::max_capacity() const {
753 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
754 }
755
756 size_t ShenandoahHeap::soft_max_capacity() const {
757 size_t v = _soft_max_size.load_relaxed();
758 assert(min_capacity() <= v && v <= max_capacity(),
759 "Should be in bounds: %zu <= %zu <= %zu",
760 min_capacity(), v, max_capacity());
761 return v;
762 }
763
764 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
765 assert(min_capacity() <= v && v <= max_capacity(),
766 "Should be in bounds: %zu <= %zu <= %zu",
767 min_capacity(), v, max_capacity());
768 _soft_max_size.store_relaxed(v);
769 heuristics()->compute_headroom_adjustment();
770 }
771
772 size_t ShenandoahHeap::min_capacity() const {
773 return _minimum_size;
774 }
775
776 size_t ShenandoahHeap::initial_capacity() const {
777 return _initial_size;
778 }
779
780 bool ShenandoahHeap::is_in(const void* p) const {
781 if (!is_in_reserved(p)) {
782 return false;
783 }
784
785 if (is_full_gc_move_in_progress()) {
786 // Full GC move is running, we do not have a consistent region
787 // information yet. But we know the pointer is in heap.
788 return true;
789 }
790
791 // Now check if we point to a live section in active region.
792 const ShenandoahHeapRegion* r = heap_region_containing(p);
793 if (p >= r->top()) {
794 return false;
795 }
796
797 if (r->is_active()) {
798 return true;
799 }
800
801 // The region is trash, but won't be recycled until after concurrent weak
802 // roots. We also don't allow mutators to allocate from trash regions
803 // during weak roots. Concurrent class unloading may access unmarked oops
804 // in trash regions.
805 return r->is_trash() && is_concurrent_weak_root_in_progress();
806 }
807
808 void ShenandoahHeap::notify_soft_max_changed() {
809 if (_uncommit_thread != nullptr) {
810 _uncommit_thread->notify_soft_max_changed();
811 }
812 }
813
814 void ShenandoahHeap::notify_explicit_gc_requested() {
815 if (_uncommit_thread != nullptr) {
816 _uncommit_thread->notify_explicit_gc_requested();
817 }
818 }
819
820 bool ShenandoahHeap::check_soft_max_changed() {
821 size_t new_soft_max = AtomicAccess::load(&SoftMaxHeapSize);
822 size_t old_soft_max = soft_max_capacity();
823 if (new_soft_max != old_soft_max) {
824 new_soft_max = MAX2(min_capacity(), new_soft_max);
825 new_soft_max = MIN2(max_capacity(), new_soft_max);
826 if (new_soft_max != old_soft_max) {
827 log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s",
828 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
829 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
830 );
831 set_soft_max_capacity(new_soft_max);
832 return true;
833 }
834 }
835 return false;
836 }
837
838 void ShenandoahHeap::notify_heap_changed() {
839 // Update monitoring counters when we took a new region. This amortizes the
840 // update costs on slow path.
841 monitoring_support()->notify_heap_changed();
842 _heap_changed.try_set();
843 }
844
845 void ShenandoahHeap::start_idle_span() {
846 heuristics()->start_idle_span();
847 }
848
849 void ShenandoahHeap::set_forced_counters_update(bool value) {
850 monitoring_support()->set_forced_counters_update(value);
851 }
852
853 void ShenandoahHeap::handle_force_counters_update() {
854 monitoring_support()->handle_force_counters_update();
855 }
856
857 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
858 // New object should fit the GCLAB size
859 size_t min_size = MAX2(size, PLAB::min_size());
860
861 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
862 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
863
864 new_size = MIN2(new_size, PLAB::max_size());
865 new_size = MAX2(new_size, PLAB::min_size());
866
867 // Record new heuristic value even if we take any shortcut. This captures
868 // the case when moderately-sized objects always take a shortcut. At some point,
869 // heuristics should catch up with them.
870 log_debug(gc, free)("Set new GCLAB size: %zu", new_size);
871 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
872
873 if (new_size < size) {
874 // New size still does not fit the object. Fall back to shared allocation.
875 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
876 log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size);
877 return nullptr;
878 }
879
880 // Retire current GCLAB, and allocate a new one.
881 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
882 gclab->retire();
883
884 size_t actual_size = 0;
885 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
886 if (gclab_buf == nullptr) {
887 return nullptr;
888 }
889
890 assert (size <= actual_size, "allocation should fit");
891
892 // ...and clear or zap just allocated TLAB, if needed.
893 if (ZeroTLAB) {
894 Copy::zero_to_words(gclab_buf, actual_size);
895 } else if (ZapTLAB) {
896 // Skip mangling the space corresponding to the object header to
897 // ensure that the returned space is not considered parsable by
898 // any concurrent GC thread.
899 size_t hdr_size = oopDesc::header_size();
900 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
901 }
902 gclab->set_buf(gclab_buf, actual_size);
903 return gclab->allocate(size);
904 }
905
906 // Called from stubs in JIT code or interpreter
907 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
908 size_t requested_size,
909 size_t* actual_size) {
910 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
911 HeapWord* res = allocate_memory(req);
912 if (res != nullptr) {
913 *actual_size = req.actual_size();
914 } else {
915 *actual_size = 0;
916 }
917 return res;
918 }
919
920 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
921 size_t word_size,
922 size_t* actual_size) {
923 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
924 HeapWord* res = allocate_memory(req);
925 if (res != nullptr) {
926 *actual_size = req.actual_size();
927 } else {
928 *actual_size = 0;
929 }
930 return res;
931 }
932
933 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
934 bool in_new_region = false;
935 HeapWord* result = nullptr;
936
937 if (req.is_mutator_alloc()) {
938
939 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
940 result = allocate_memory_under_lock(req, in_new_region);
941 }
942
943 // Check that gc overhead is not exceeded.
944 //
945 // Shenandoah will grind along for quite a while allocating one
946 // object at a time using shared (non-tlab) allocations. This check
947 // is testing that the GC overhead limit has not been exceeded.
948 // This will notify the collector to start a cycle, but will raise
949 // an OOME to the mutator if the last Full GCs have not made progress.
950 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
951 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
952 control_thread()->handle_alloc_failure(req, false);
953 req.set_actual_size(0);
954 return nullptr;
955 }
956
957 if (result == nullptr) {
958 // Block until control thread reacted, then retry allocation.
959 //
960 // It might happen that one of the threads requesting allocation would unblock
961 // way later after GC happened, only to fail the second allocation, because
962 // other threads have already depleted the free storage. In this case, a better
963 // strategy is to try again, until at least one full GC has completed.
964 //
965 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
966 // a) We experienced a GC that had good progress, or
967 // b) We experienced at least one Full GC (whether or not it had good progress)
968
969 const size_t original_count = shenandoah_policy()->full_gc_count();
970 while (result == nullptr && should_retry_allocation(original_count)) {
971 control_thread()->handle_alloc_failure(req, true);
972 result = allocate_memory_under_lock(req, in_new_region);
973 }
974 if (result != nullptr) {
975 // If our allocation request has been satisfied after it initially failed, we count this as good gc progress
976 notify_gc_progress();
977 }
978 if (log_develop_is_enabled(Debug, gc, alloc)) {
979 ResourceMark rm;
980 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu"
981 ", Original: %zu, Latest: %zu",
982 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
983 original_count, get_gc_no_progress_count());
984 }
985 }
986 } else {
987 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
988 result = allocate_memory_under_lock(req, in_new_region);
989 // Do not call handle_alloc_failure() here, because we cannot block.
990 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
991 }
992
993 if (in_new_region) {
994 notify_heap_changed();
995 }
996
997 if (result == nullptr) {
998 req.set_actual_size(0);
999 }
1000
1001 if (result != nullptr) {
1002 size_t requested = req.size();
1003 size_t actual = req.actual_size();
1004
1005 assert (req.is_lab_alloc() || (requested == actual),
1006 "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu",
1007 req.type_string(), requested, actual);
1008 }
1009
1010 return result;
1011 }
1012
1013 inline bool ShenandoahHeap::should_retry_allocation(size_t original_full_gc_count) const {
1014 return shenandoah_policy()->full_gc_count() == original_full_gc_count
1015 && !shenandoah_policy()->is_at_shutdown();
1016 }
1017
1018 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1019 // If we are dealing with mutator allocation, then we may need to block for safepoint.
1020 // We cannot block for safepoint for GC allocations, because there is a high chance
1021 // we are already running at safepoint or from stack watermark machinery, and we cannot
1022 // block again.
1023 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1024
1025 // Make sure the old generation has room for either evacuations or promotions before trying to allocate.
1026 if (req.is_old() && !old_generation()->can_allocate(req)) {
1027 return nullptr;
1028 }
1029
1030 // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available
1031 // memory.
1032 HeapWord* result = _free_set->allocate(req, in_new_region);
1033
1034 // Record the plab configuration for this result and register the object.
1035 if (result != nullptr && req.is_old()) {
1036 if (req.is_lab_alloc()) {
1037 old_generation()->configure_plab_for_current_thread(req);
1038 } else {
1039 // Register the newly allocated object while we're holding the global lock since there's no synchronization
1040 // built in to the implementation of register_object(). There are potential races when multiple independent
1041 // threads are allocating objects, some of which might span the same card region. For example, consider
1042 // a card table's memory region within which three objects are being allocated by three different threads:
1043 //
1044 // objects being "concurrently" allocated:
1045 // [-----a------][-----b-----][--------------c------------------]
1046 // [---- card table memory range --------------]
1047 //
1048 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a
1049 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region.
1050 // Allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region.
1051 // Allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this
1052 // card region.
1053 //
1054 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as
1055 // last-start representing object b while first-start represents object c. This is why we need to require all
1056 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range.
1057 old_generation()->card_scan()->register_object(result);
1058
1059 if (req.is_promotion()) {
1060 // Shared promotion.
1061 const size_t actual_size = req.actual_size() * HeapWordSize;
1062 log_debug(gc, plab)("Expend shared promotion of %zu bytes", actual_size);
1063 old_generation()->expend_promoted(actual_size);
1064 }
1065 }
1066 }
1067
1068 return result;
1069 }
1070
1071 HeapWord* ShenandoahHeap::mem_allocate(size_t size) {
1072 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1073 return allocate_memory(req);
1074 }
1075
1076 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1077 size_t size,
1078 Metaspace::MetadataType mdtype) {
1079 MetaWord* result;
1080
1081 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1082 ShenandoahHeuristics* h = global_generation()->heuristics();
1083 if (h->can_unload_classes()) {
1084 h->record_metaspace_oom();
1085 }
1086
1087 // Expand and retry allocation
1088 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1089 if (result != nullptr) {
1090 return result;
1091 }
1092
1093 // Start full GC
1094 collect(GCCause::_metadata_GC_clear_soft_refs);
1095
1096 // Retry allocation
1097 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1098 if (result != nullptr) {
1099 return result;
1100 }
1101
1102 // Expand and retry allocation
1103 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1104 if (result != nullptr) {
1105 return result;
1106 }
1107
1108 // Out of memory
1109 return nullptr;
1110 }
1111
1112 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1113 private:
1114 ShenandoahHeap* const _heap;
1115 Thread* const _thread;
1116 public:
1117 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1118 _heap(heap), _thread(Thread::current()) {}
1119
1120 void do_object(oop p) {
1121 shenandoah_assert_marked(nullptr, p);
1122 if (!p->is_forwarded()) {
1123 _heap->evacuate_object(p, _thread);
1124 }
1125 }
1126 };
1127
1128 class ShenandoahEvacuationTask : public WorkerTask {
1129 private:
1130 ShenandoahHeap* const _sh;
1131 ShenandoahCollectionSet* const _cs;
1132 bool _concurrent;
1133 public:
1134 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1135 ShenandoahCollectionSet* cs,
1136 bool concurrent) :
1137 WorkerTask("Shenandoah Evacuation"),
1138 _sh(sh),
1139 _cs(cs),
1140 _concurrent(concurrent)
1141 {}
1142
1143 void work(uint worker_id) {
1144 if (_concurrent) {
1145 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1146 ShenandoahSuspendibleThreadSetJoiner stsj;
1147 ShenandoahEvacOOMScope oom_evac_scope;
1148 do_work();
1149 } else {
1150 ShenandoahParallelWorkerSession worker_session(worker_id);
1151 ShenandoahEvacOOMScope oom_evac_scope;
1152 do_work();
1153 }
1154 }
1155
1156 private:
1157 void do_work() {
1158 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1159 ShenandoahHeapRegion* r;
1160 while ((r =_cs->claim_next()) != nullptr) {
1161 assert(r->has_live(), "Region %zu should have been reclaimed early", r->index());
1162 _sh->marked_object_iterate(r, &cl);
1163
1164 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1165 break;
1166 }
1167 }
1168 }
1169 };
1170
1171 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1172 private:
1173 bool const _resize;
1174 public:
1175 explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1176 void do_thread(Thread* thread) override {
1177 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1178 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1179 gclab->retire();
1180 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1181 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1182 }
1183
1184 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1185 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1186 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1187
1188 // There are two reasons to retire all plabs between old-gen evacuation passes.
1189 // 1. We need to make the plab memory parsable by remembered-set scanning.
1190 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1191 ShenandoahGenerationalHeap::heap()->retire_plab(plab, thread);
1192
1193 // Re-enable promotions for the next evacuation phase.
1194 ShenandoahThreadLocalData::enable_plab_promotions(thread);
1195
1196 // Reset the fill size for next evacuation phase.
1197 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) {
1198 ShenandoahThreadLocalData::set_plab_size(thread, 0);
1199 }
1200 }
1201 }
1202 };
1203
1204 class ShenandoahGCStatePropagatorHandshakeClosure : public HandshakeClosure {
1205 public:
1206 explicit ShenandoahGCStatePropagatorHandshakeClosure(char gc_state) :
1207 HandshakeClosure("Shenandoah GC State Change"),
1208 _gc_state(gc_state) {}
1209
1210 void do_thread(Thread* thread) override {
1211 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state);
1212 }
1213 private:
1214 char _gc_state;
1215 };
1216
1217 class ShenandoahPrepareForUpdateRefsHandshakeClosure : public HandshakeClosure {
1218 public:
1219 explicit ShenandoahPrepareForUpdateRefsHandshakeClosure(char gc_state) :
1220 HandshakeClosure("Shenandoah Prepare for Update Refs"),
1221 _retire(ResizeTLAB), _propagator(gc_state) {}
1222
1223 void do_thread(Thread* thread) override {
1224 _propagator.do_thread(thread);
1225 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) {
1226 _retire.do_thread(thread);
1227 }
1228 }
1229 private:
1230 ShenandoahRetireGCLABClosure _retire;
1231 ShenandoahGCStatePropagatorHandshakeClosure _propagator;
1232 };
1233
1234 void ShenandoahHeap::evacuate_collection_set(ShenandoahGeneration* generation, bool concurrent) {
1235 assert(generation->is_global(), "Only global generation expected here");
1236 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1237 workers()->run_task(&task);
1238 }
1239
1240 void ShenandoahHeap::concurrent_prepare_for_update_refs() {
1241 {
1242 // Java threads take this lock while they are being attached and added to the list of threads.
1243 // If another thread holds this lock before we update the gc state, it will receive a stale
1244 // gc state, but they will have been added to the list of java threads and so will be corrected
1245 // by the following handshake.
1246 MutexLocker lock(Threads_lock);
1247
1248 // A cancellation at this point means the degenerated cycle must resume from update-refs.
1249 set_gc_state_concurrent(EVACUATION, false);
1250 set_gc_state_concurrent(WEAK_ROOTS, false);
1251 set_gc_state_concurrent(UPDATE_REFS, true);
1252 }
1253
1254 // This will propagate the gc state and retire gclabs and plabs for threads that require it.
1255 ShenandoahPrepareForUpdateRefsHandshakeClosure prepare_for_update_refs(_gc_state.raw_value());
1256
1257 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately.
1258 Threads::non_java_threads_do(&prepare_for_update_refs);
1259
1260 // Now retire gclabs and plabs and propagate gc_state for mutator threads
1261 Handshake::execute(&prepare_for_update_refs);
1262
1263 _update_refs_iterator.reset();
1264 }
1265
1266 class ShenandoahCompositeHandshakeClosure : public HandshakeClosure {
1267 HandshakeClosure* _handshake_1;
1268 HandshakeClosure* _handshake_2;
1269 public:
1270 ShenandoahCompositeHandshakeClosure(HandshakeClosure* handshake_1, HandshakeClosure* handshake_2) :
1271 HandshakeClosure(handshake_2->name()),
1272 _handshake_1(handshake_1), _handshake_2(handshake_2) {}
1273
1274 void do_thread(Thread* thread) override {
1275 _handshake_1->do_thread(thread);
1276 _handshake_2->do_thread(thread);
1277 }
1278 };
1279
1280 void ShenandoahHeap::concurrent_final_roots(HandshakeClosure* handshake_closure) {
1281 {
1282 assert(!is_evacuation_in_progress(), "Should not evacuate for abbreviated or old cycles");
1283 MutexLocker lock(Threads_lock);
1284 set_gc_state_concurrent(WEAK_ROOTS, false);
1285 }
1286
1287 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
1288 Threads::non_java_threads_do(&propagator);
1289 if (handshake_closure == nullptr) {
1290 Handshake::execute(&propagator);
1291 } else {
1292 ShenandoahCompositeHandshakeClosure composite(&propagator, handshake_closure);
1293 Handshake::execute(&composite);
1294 }
1295 }
1296
1297 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1298 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1299 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
1300 // This thread went through the OOM during evac protocol. It is safe to return
1301 // the forward pointer. It must not attempt to evacuate any other objects.
1302 return ShenandoahBarrierSet::resolve_forwarded(p);
1303 }
1304
1305 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1306
1307 ShenandoahHeapRegion* r = heap_region_containing(p);
1308 assert(!r->is_humongous(), "never evacuate humongous objects");
1309
1310 ShenandoahAffiliation target_gen = r->affiliation();
1311 return try_evacuate_object(p, thread, r, target_gen);
1312 }
1313
1314 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1315 ShenandoahAffiliation target_gen) {
1316 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1317 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1318 bool alloc_from_lab = true;
1319 HeapWord* copy = nullptr;
1320
1321 markWord mark = p->mark();
1322 if (ShenandoahForwarding::is_forwarded(mark)) {
1323 return ShenandoahForwarding::get_forwardee(p);
1324 }
1325 size_t old_size = ShenandoahForwarding::size(p);
1326 size_t size = p->copy_size(old_size, mark);
1327
1328 #ifdef ASSERT
1329 if (ShenandoahOOMDuringEvacALot &&
1330 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1331 copy = nullptr;
1332 } else {
1333 #endif
1334 if (UseTLAB) {
1335 copy = allocate_from_gclab(thread, size);
1336 }
1337 if (copy == nullptr) {
1338 // If we failed to allocate in LAB, we'll try a shared allocation.
1339 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1340 copy = allocate_memory(req);
1341 alloc_from_lab = false;
1342 }
1343 #ifdef ASSERT
1344 }
1345 #endif
1346
1347 if (copy == nullptr) {
1348 control_thread()->handle_alloc_failure_evac(size);
1349
1350 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1351
1352 return ShenandoahBarrierSet::resolve_forwarded(p);
1353 }
1354
1355 if (ShenandoahEvacTracking) {
1356 evac_tracker()->begin_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1357 }
1358
1359 // Copy the object:
1360 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, old_size);
1361 oop copy_val = cast_to_oop(copy);
1362
1363 // Initialize the identity hash on the copy before installing the forwarding
1364 // pointer, using the mark word we captured earlier. We must do this before
1365 // the CAS so that the copy is fully initialized when it becomes visible to
1366 // other threads. Using the captured mark (rather than re-reading the copy's
1367 // mark) avoids races with other threads that may have evacuated p and
1368 // installed a forwarding pointer in the meantime.
1369 if (UseCompactObjectHeaders && mark.is_hashed_not_expanded()) {
1370 copy_val->set_mark(copy_val->initialize_hash_if_necessary(p, mark.klass(), mark));
1371 }
1372
1373 // Try to install the new forwarding pointer.
1374 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1375 if (result == copy_val) {
1376 // Successfully evacuated. Our copy is now the public one!
1377 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1378 shenandoah_assert_correct(nullptr, copy_val);
1379 if (ShenandoahEvacTracking) {
1380 evac_tracker()->end_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1381 }
1382 return copy_val;
1383 } else {
1384 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1385 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1386 // But if it happens to contain references to evacuated regions, those references would
1387 // not get updated for this stale copy during this cycle, and we will crash while scanning
1388 // it the next cycle.
1389 if (alloc_from_lab) {
1390 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1391 // object will overwrite this stale copy, or the filler object on LAB retirement will
1392 // do this.
1393 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1394 } else {
1395 // For non-LAB allocations, we have no way to retract the allocation, and
1396 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1397 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1398 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1399 fill_with_object(copy, size);
1400 shenandoah_assert_correct(nullptr, copy_val);
1401 // For non-LAB allocations, the object has already been registered
1402 }
1403 shenandoah_assert_correct(nullptr, result);
1404 return result;
1405 }
1406 }
1407
1408 void ShenandoahHeap::trash_cset_regions() {
1409 ShenandoahHeapLocker locker(lock());
1410
1411 ShenandoahCollectionSet* set = collection_set();
1412 ShenandoahHeapRegion* r;
1413 set->clear_current_index();
1414 while ((r = set->next()) != nullptr) {
1415 r->make_trash();
1416 }
1417 collection_set()->clear();
1418 }
1419
1420 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1421 st->print_cr("Heap Regions:");
1422 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1423 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1424 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1425 st->print_cr("UWM=update watermark, U=used");
1426 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1427 st->print_cr("S=shared allocs, L=live data");
1428 st->print_cr("CP=critical pins");
1429
1430 for (size_t i = 0; i < num_regions(); i++) {
1431 get_region(i)->print_on(st);
1432 }
1433 }
1434
1435 void ShenandoahHeap::process_gc_stats() const {
1436 // Commit worker statistics to cycle data
1437 phase_timings()->flush_par_workers_to_cycle();
1438
1439 // Print GC stats for current cycle
1440 LogTarget(Info, gc, stats) lt;
1441 if (lt.is_enabled()) {
1442 ResourceMark rm;
1443 LogStream ls(lt);
1444 phase_timings()->print_cycle_on(&ls);
1445 if (ShenandoahEvacTracking) {
1446 ShenandoahCycleStats evac_stats = evac_tracker()->flush_cycle_to_global();
1447 evac_tracker()->print_evacuations_on(&ls, &evac_stats.workers,
1448 &evac_stats.mutators);
1449 }
1450 }
1451
1452 // Commit statistics to globals
1453 phase_timings()->flush_cycle_to_global();
1454 }
1455
1456 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) const {
1457 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1458 assert(!start->has_live(), "liveness must be zero");
1459
1460 // Do not try to get the size of this humongous object. STW collections will
1461 // have already unloaded classes, so an unmarked object may have a bad klass pointer.
1462 ShenandoahHeapRegion* region = start;
1463 size_t index = region->index();
1464 do {
1465 assert(region->is_humongous(), "Expect correct humongous start or continuation");
1466 assert(!region->is_cset(), "Humongous region should not be in collection set");
1467 region->make_trash_immediate();
1468 region = get_region(++index);
1469 } while (region != nullptr && region->is_humongous_continuation());
1470
1471 // Return number of regions trashed
1472 return index - start->index();
1473 }
1474
1475 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1476 public:
1477 ShenandoahCheckCleanGCLABClosure() {}
1478 void do_thread(Thread* thread) {
1479 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1480 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1481 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1482
1483 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1484 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1485 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1486 assert(plab->words_remaining() == 0, "PLAB should not need retirement");
1487 }
1488 }
1489 };
1490
1491 void ShenandoahHeap::labs_make_parsable() {
1492 assert(UseTLAB, "Only call with UseTLAB");
1493
1494 ShenandoahRetireGCLABClosure cl(false);
1495
1496 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1497 ThreadLocalAllocBuffer& tlab = t->tlab();
1498 tlab.make_parsable();
1499 if (ZeroTLAB) {
1500 t->retire_tlab();
1501 }
1502 cl.do_thread(t);
1503 }
1504
1505 workers()->threads_do(&cl);
1506
1507 if (safepoint_workers() != nullptr) {
1508 safepoint_workers()->threads_do(&cl);
1509 }
1510 }
1511
1512 void ShenandoahHeap::tlabs_retire(bool resize) {
1513 assert(UseTLAB, "Only call with UseTLAB");
1514 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1515
1516 ThreadLocalAllocStats stats;
1517
1518 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1519 t->retire_tlab(&stats);
1520 if (resize) {
1521 t->tlab().resize();
1522 }
1523 }
1524
1525 stats.publish();
1526
1527 #ifdef ASSERT
1528 ShenandoahCheckCleanGCLABClosure cl;
1529 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1530 cl.do_thread(t);
1531 }
1532 workers()->threads_do(&cl);
1533 #endif
1534 }
1535
1536 void ShenandoahHeap::gclabs_retire(bool resize) {
1537 assert(UseTLAB, "Only call with UseTLAB");
1538 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1539
1540 ShenandoahRetireGCLABClosure cl(resize);
1541 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1542 cl.do_thread(t);
1543 }
1544
1545 workers()->threads_do(&cl);
1546
1547 if (safepoint_workers() != nullptr) {
1548 safepoint_workers()->threads_do(&cl);
1549 }
1550 }
1551
1552 // Returns size in bytes
1553 size_t ShenandoahHeap::unsafe_max_tlab_alloc() const {
1554 // Return the max allowed size, and let the allocation path
1555 // figure out the safe size for current allocation.
1556 return ShenandoahHeapRegion::max_tlab_size_bytes();
1557 }
1558
1559 size_t ShenandoahHeap::max_tlab_size() const {
1560 // Returns size in words
1561 return ShenandoahHeapRegion::max_tlab_size_words();
1562 }
1563
1564 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) {
1565 // These requests are ignored because we can't easily have Shenandoah jump into
1566 // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent
1567 // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly
1568 // on the VM thread, but this would confuse the control thread mightily and doesn't
1569 // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a
1570 // concurrent cycle in the prologue of the heap inspect/dump operation (see VM_HeapDumper::doit_prologue).
1571 // This is how other concurrent collectors in the JVM handle this scenario as well.
1572 assert(Thread::current()->is_VM_thread(), "Should be the VM thread");
1573 guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause");
1574 }
1575
1576 void ShenandoahHeap::collect(GCCause::Cause cause) {
1577 control_thread()->request_gc(cause);
1578 }
1579
1580 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1581 // This method is only called by `CollectedHeap::collect_as_vm_thread`, which we have
1582 // overridden to do nothing. See the comment there for an explanation of how heap inspections
1583 // work for Shenandoah.
1584 ShouldNotReachHere();
1585 }
1586
1587 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1588 ShenandoahHeapRegion* r = heap_region_containing(addr);
1589 if (r != nullptr) {
1590 return r->block_start(addr);
1591 }
1592 return nullptr;
1593 }
1594
1595 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1596 ShenandoahHeapRegion* r = heap_region_containing(addr);
1597 return r->block_is_obj(addr);
1598 }
1599
1600 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1601 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1602 }
1603
1604 void ShenandoahHeap::prepare_for_verify() {
1605 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1606 labs_make_parsable();
1607 }
1608 }
1609
1610 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1611 if (_shenandoah_policy->is_at_shutdown()) {
1612 return;
1613 }
1614
1615 if (_control_thread != nullptr) {
1616 tcl->do_thread(_control_thread);
1617 }
1618
1619 if (_uncommit_thread != nullptr) {
1620 tcl->do_thread(_uncommit_thread);
1621 }
1622
1623 workers()->threads_do(tcl);
1624 if (_safepoint_workers != nullptr) {
1625 _safepoint_workers->threads_do(tcl);
1626 }
1627 }
1628
1629 void ShenandoahHeap::print_tracing_info() const {
1630 LogTarget(Info, gc, stats) lt;
1631 if (lt.is_enabled()) {
1632 ResourceMark rm;
1633 LogStream ls(lt);
1634
1635 if (ShenandoahEvacTracking) {
1636 evac_tracker()->print_global_on(&ls);
1637 ls.cr();
1638 ls.cr();
1639 }
1640
1641 phase_timings()->print_global_on(&ls);
1642
1643 ls.cr();
1644 ls.cr();
1645
1646 shenandoah_policy()->print_gc_stats(&ls);
1647
1648 ls.cr();
1649 ls.cr();
1650 }
1651 }
1652
1653 // Active generation may only be set by the VM thread at a safepoint.
1654 void ShenandoahHeap::set_active_generation(ShenandoahGeneration* generation) {
1655 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1656 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1657 _active_generation = generation;
1658 }
1659
1660 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
1661 shenandoah_policy()->record_collection_cause(cause);
1662
1663 const GCCause::Cause current = gc_cause();
1664 assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s",
1665 GCCause::to_string(current), GCCause::to_string(cause));
1666
1667 set_gc_cause(cause);
1668
1669 generation->heuristics()->record_cycle_start();
1670 }
1671
1672 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1673 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1674
1675 generation->heuristics()->record_cycle_end();
1676 if (mode()->is_generational() && generation->is_global()) {
1677 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1678 young_generation()->heuristics()->record_cycle_end();
1679 old_generation()->heuristics()->record_cycle_end();
1680 }
1681
1682 set_gc_cause(GCCause::_no_gc);
1683 }
1684
1685 void ShenandoahHeap::verify(VerifyOption vo) {
1686 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1687 if (ShenandoahVerify) {
1688 verifier()->verify_generic(active_generation(), vo);
1689 } else {
1690 // TODO: Consider allocating verification bitmaps on demand,
1691 // and turn this on unconditionally.
1692 }
1693 }
1694 }
1695 size_t ShenandoahHeap::tlab_capacity() const {
1696 return _free_set->capacity_not_holding_lock();
1697 }
1698
1699 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1700 private:
1701 MarkBitMap* _bitmap;
1702 ShenandoahScanObjectStack* _oop_stack;
1703 ShenandoahHeap* const _heap;
1704 ShenandoahMarkingContext* const _marking_context;
1705
1706 template <class T>
1707 void do_oop_work(T* p) {
1708 T o = RawAccess<>::oop_load(p);
1709 if (!CompressedOops::is_null(o)) {
1710 oop obj = CompressedOops::decode_not_null(o);
1711 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1712 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1713 return;
1714 }
1715 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1716
1717 assert(oopDesc::is_oop(obj), "must be a valid oop");
1718 if (!_bitmap->is_marked(obj)) {
1719 _bitmap->mark(obj);
1720 _oop_stack->push(obj);
1721 }
1722 }
1723 }
1724 public:
1725 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1726 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1727 _marking_context(_heap->marking_context()) {}
1728 void do_oop(oop* p) { do_oop_work(p); }
1729 void do_oop(narrowOop* p) { do_oop_work(p); }
1730 };
1731
1732 /*
1733 * This is public API, used in preparation of object_iterate().
1734 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1735 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1736 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1737 */
1738 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1739 // No-op.
1740 }
1741
1742 /*
1743 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1744 *
1745 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1746 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1747 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1748 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1749 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1750 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1751 * wiped the bitmap in preparation for next marking).
1752 *
1753 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1754 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1755 * is allowed to report dead objects, but is not required to do so.
1756 */
1757 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1758 // Reset bitmap
1759 if (!prepare_aux_bitmap_for_iteration())
1760 return;
1761
1762 ShenandoahScanObjectStack oop_stack;
1763 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1764 // Seed the stack with root scan
1765 scan_roots_for_iteration(&oop_stack, &oops);
1766
1767 // Work through the oop stack to traverse heap
1768 while (! oop_stack.is_empty()) {
1769 oop obj = oop_stack.pop();
1770 assert(oopDesc::is_oop(obj), "must be a valid oop");
1771 cl->do_object(obj);
1772 obj->oop_iterate(&oops);
1773 }
1774
1775 assert(oop_stack.is_empty(), "should be empty");
1776 // Reclaim bitmap
1777 reclaim_aux_bitmap_for_iteration();
1778 }
1779
1780 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1781 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1782 if (!_aux_bitmap_region_special) {
1783 bool success = os::commit_memory((char *) _aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false);
1784 if (!success) {
1785 log_warning(gc)("Auxiliary marking bitmap commit failed: " PTR_FORMAT " (%zu bytes)",
1786 p2i(_aux_bitmap_region.start()), _aux_bitmap_region.byte_size());
1787 return false;
1788 }
1789 }
1790 _aux_bit_map.clear();
1791 return true;
1792 }
1793
1794 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1795 // Process GC roots according to current GC cycle
1796 // This populates the work stack with initial objects
1797 // It is important to relinquish the associated locks before diving
1798 // into heap dumper
1799 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1800 ShenandoahHeapIterationRootScanner rp(n_workers);
1801 rp.roots_do(oops);
1802 }
1803
1804 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1805 if (!_aux_bitmap_region_special) {
1806 os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size());
1807 }
1808 }
1809
1810 // Closure for parallelly iterate objects
1811 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1812 private:
1813 MarkBitMap* _bitmap;
1814 ShenandoahObjToScanQueue* _queue;
1815 ShenandoahHeap* const _heap;
1816 ShenandoahMarkingContext* const _marking_context;
1817
1818 template <class T>
1819 void do_oop_work(T* p) {
1820 T o = RawAccess<>::oop_load(p);
1821 if (!CompressedOops::is_null(o)) {
1822 oop obj = CompressedOops::decode_not_null(o);
1823 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1824 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1825 return;
1826 }
1827 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1828
1829 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1830 if (_bitmap->par_mark(obj)) {
1831 _queue->push(ShenandoahMarkTask(obj));
1832 }
1833 }
1834 }
1835 public:
1836 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1837 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1838 _marking_context(_heap->marking_context()) {}
1839 void do_oop(oop* p) { do_oop_work(p); }
1840 void do_oop(narrowOop* p) { do_oop_work(p); }
1841 };
1842
1843 // Object iterator for parallel heap iteraion.
1844 // The root scanning phase happenes in construction as a preparation of
1845 // parallel marking queues.
1846 // Every worker processes it's own marking queue. work-stealing is used
1847 // to balance workload.
1848 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1849 private:
1850 uint _num_workers;
1851 bool _init_ready;
1852 MarkBitMap* _aux_bit_map;
1853 ShenandoahHeap* _heap;
1854 ShenandoahScanObjectStack _roots_stack; // global roots stack
1855 ShenandoahObjToScanQueueSet* _task_queues;
1856 public:
1857 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1858 _num_workers(num_workers),
1859 _init_ready(false),
1860 _aux_bit_map(bitmap),
1861 _heap(ShenandoahHeap::heap()) {
1862 // Initialize bitmap
1863 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1864 if (!_init_ready) {
1865 return;
1866 }
1867
1868 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1869 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1870
1871 _init_ready = prepare_worker_queues();
1872 }
1873
1874 ~ShenandoahParallelObjectIterator() {
1875 // Reclaim bitmap
1876 _heap->reclaim_aux_bitmap_for_iteration();
1877 // Reclaim queue for workers
1878 if (_task_queues!= nullptr) {
1879 for (uint i = 0; i < _num_workers; ++i) {
1880 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1881 if (q != nullptr) {
1882 delete q;
1883 _task_queues->register_queue(i, nullptr);
1884 }
1885 }
1886 delete _task_queues;
1887 _task_queues = nullptr;
1888 }
1889 }
1890
1891 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1892 if (_init_ready) {
1893 object_iterate_parallel(cl, worker_id, _task_queues);
1894 }
1895 }
1896
1897 private:
1898 // Divide global root_stack into worker queues
1899 bool prepare_worker_queues() {
1900 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1901 // Initialize queues for every workers
1902 for (uint i = 0; i < _num_workers; ++i) {
1903 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1904 _task_queues->register_queue(i, task_queue);
1905 }
1906 // Divide roots among the workers. Assume that object referencing distribution
1907 // is related with root kind, use round-robin to make every worker have same chance
1908 // to process every kind of roots
1909 size_t roots_num = _roots_stack.size();
1910 if (roots_num == 0) {
1911 // No work to do
1912 return false;
1913 }
1914
1915 for (uint j = 0; j < roots_num; j++) {
1916 uint stack_id = j % _num_workers;
1917 oop obj = _roots_stack.pop();
1918 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1919 }
1920 return true;
1921 }
1922
1923 void object_iterate_parallel(ObjectClosure* cl,
1924 uint worker_id,
1925 ShenandoahObjToScanQueueSet* queue_set) {
1926 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1927 assert(queue_set != nullptr, "task queue must not be null");
1928
1929 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1930 assert(q != nullptr, "object iterate queue must not be null");
1931
1932 ShenandoahMarkTask t;
1933 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1934
1935 // Work through the queue to traverse heap.
1936 // Steal when there is no task in queue.
1937 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1938 oop obj = t.obj();
1939 assert(oopDesc::is_oop(obj), "must be a valid oop");
1940 cl->do_object(obj);
1941 obj->oop_iterate(&oops);
1942 }
1943 assert(q->is_empty(), "should be empty");
1944 }
1945 };
1946
1947 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1948 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1949 }
1950
1951 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1952 void ShenandoahHeap::keep_alive(oop obj) {
1953 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1954 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1955 }
1956 }
1957
1958 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1959 for (size_t i = 0; i < num_regions(); i++) {
1960 ShenandoahHeapRegion* current = get_region(i);
1961 blk->heap_region_do(current);
1962 }
1963 }
1964
1965 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1966 private:
1967 ShenandoahHeap* const _heap;
1968 ShenandoahHeapRegionClosure* const _blk;
1969 size_t const _stride;
1970
1971 shenandoah_padding(0);
1972 Atomic<size_t> _index;
1973 shenandoah_padding(1);
1974
1975 public:
1976 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
1977 WorkerTask("Shenandoah Parallel Region Operation"),
1978 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
1979
1980 void work(uint worker_id) {
1981 ShenandoahParallelWorkerSession worker_session(worker_id);
1982 size_t stride = _stride;
1983
1984 size_t max = _heap->num_regions();
1985 while (_index.load_relaxed() < max) {
1986 size_t cur = _index.fetch_then_add(stride, memory_order_relaxed);
1987 size_t start = cur;
1988 size_t end = MIN2(cur + stride, max);
1989 if (start >= max) break;
1990
1991 for (size_t i = cur; i < end; i++) {
1992 ShenandoahHeapRegion* current = _heap->get_region(i);
1993 _blk->heap_region_do(current);
1994 }
1995 }
1996 }
1997 };
1998
1999 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2000 assert(blk->is_thread_safe(), "Only thread-safe closures here");
2001 const uint active_workers = workers()->active_workers();
2002 const size_t n_regions = num_regions();
2003 size_t stride = blk->parallel_region_stride();
2004 if (stride == 0 && active_workers > 1) {
2005 // Automatically derive the stride to balance the work between threads
2006 // evenly. Do not try to split work if below the reasonable threshold.
2007 constexpr size_t threshold = 4096;
2008 stride = n_regions <= threshold ?
2009 threshold :
2010 (n_regions + active_workers - 1) / active_workers;
2011 }
2012
2013 if (n_regions > stride && active_workers > 1) {
2014 ShenandoahParallelHeapRegionTask task(blk, stride);
2015 workers()->run_task(&task);
2016 } else {
2017 heap_region_iterate(blk);
2018 }
2019 }
2020
2021 class ShenandoahRendezvousHandshakeClosure : public HandshakeClosure {
2022 public:
2023 inline ShenandoahRendezvousHandshakeClosure(const char* name) : HandshakeClosure(name) {}
2024 inline void do_thread(Thread* thread) {}
2025 };
2026
2027 void ShenandoahHeap::rendezvous_threads(const char* name) {
2028 ShenandoahRendezvousHandshakeClosure cl(name);
2029 Handshake::execute(&cl);
2030 }
2031
2032 void ShenandoahHeap::recycle_trash() {
2033 free_set()->recycle_trash();
2034 }
2035
2036 void ShenandoahHeap::do_class_unloading() {
2037 _unloader.unload();
2038 if (mode()->is_generational()) {
2039 old_generation()->set_parsable(false);
2040 }
2041 }
2042
2043 void ShenandoahHeap::stw_weak_refs(ShenandoahGeneration* generation, bool full_gc) {
2044 // Weak refs processing
2045 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2046 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2047 ShenandoahTimingsTracker t(phase);
2048 ShenandoahGCWorkerPhase worker_phase(phase);
2049 generation->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2050 }
2051
2052 void ShenandoahHeap::prepare_update_heap_references() {
2053 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2054
2055 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2056 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2057 // for future GCLABs here.
2058 if (UseTLAB) {
2059 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2060 gclabs_retire(ResizeTLAB);
2061 }
2062
2063 _update_refs_iterator.reset();
2064 }
2065
2066 void ShenandoahHeap::propagate_gc_state_to_all_threads() {
2067 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2068 if (_gc_state_changed) {
2069 // If we are only marking old, we do not need to process young pointers
2070 ShenandoahBarrierSet::satb_mark_queue_set().set_filter_out_young(
2071 is_concurrent_old_mark_in_progress() && !is_concurrent_young_mark_in_progress()
2072 );
2073 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
2074 Threads::threads_do(&propagator);
2075 _gc_state_changed = false;
2076 }
2077 }
2078
2079 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) {
2080 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2081 _gc_state.set_cond(mask, value);
2082 _gc_state_changed = true;
2083 }
2084
2085 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) {
2086 // Holding the thread lock here assures that any thread created after we change the gc
2087 // state will have the correct state. It also prevents attaching threads from seeing
2088 // an inconsistent state. See ShenandoahBarrierSet::on_thread_attach for reference. Established
2089 // threads will use their thread local copy of the gc state (changed by a handshake, or on a
2090 // safepoint).
2091 assert(Threads_lock->is_locked(), "Must hold thread lock for concurrent gc state change");
2092 _gc_state.set_cond(mask, value);
2093 }
2094
2095 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2096 uint mask;
2097 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2098 if (!in_progress && is_concurrent_old_mark_in_progress()) {
2099 assert(mode()->is_generational(), "Only generational GC has old marking");
2100 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2101 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2102 mask = YOUNG_MARKING;
2103 } else {
2104 mask = MARKING | YOUNG_MARKING;
2105 }
2106 set_gc_state_at_safepoint(mask, in_progress);
2107 manage_satb_barrier(in_progress);
2108 }
2109
2110 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2111 #ifdef ASSERT
2112 // has_forwarded_objects() iff UPDATE_REFS or EVACUATION
2113 bool has_forwarded = has_forwarded_objects();
2114 bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION);
2115 bool evacuating = _gc_state.is_set(EVACUATION);
2116 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2117 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2118 #endif
2119 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2120 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2121 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2122 set_gc_state_at_safepoint(OLD_MARKING, in_progress);
2123 } else {
2124 set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress);
2125 }
2126 manage_satb_barrier(in_progress);
2127 }
2128
2129 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2130 return old_generation()->is_preparing_for_mark();
2131 }
2132
2133 void ShenandoahHeap::manage_satb_barrier(bool active) {
2134 if (is_concurrent_mark_in_progress()) {
2135 // Ignore request to deactivate barrier while concurrent mark is in progress.
2136 // Do not attempt to re-activate the barrier if it is already active.
2137 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2138 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2139 }
2140 } else {
2141 // No concurrent marking is in progress so honor request to deactivate,
2142 // but only if the barrier is already active.
2143 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2144 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2145 }
2146 }
2147 }
2148
2149 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2150 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2151 set_gc_state_at_safepoint(EVACUATION, in_progress);
2152 }
2153
2154 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2155 if (in_progress) {
2156 _concurrent_strong_root_in_progress.set();
2157 } else {
2158 _concurrent_strong_root_in_progress.unset();
2159 }
2160 }
2161
2162 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2163 set_gc_state_at_safepoint(WEAK_ROOTS, cond);
2164 }
2165
2166 GCTracer* ShenandoahHeap::tracer() {
2167 return shenandoah_policy()->tracer();
2168 }
2169
2170 size_t ShenandoahHeap::tlab_used() const {
2171 return _free_set->used_not_holding_lock();
2172 }
2173
2174 bool ShenandoahHeap::try_cancel_gc(GCCause::Cause cause) {
2175 const GCCause::Cause prev = _cancelled_gc.xchg(cause);
2176 return prev == GCCause::_no_gc || prev == GCCause::_shenandoah_concurrent_gc;
2177 }
2178
2179 void ShenandoahHeap::cancel_concurrent_mark() {
2180 if (mode()->is_generational()) {
2181 young_generation()->cancel_marking();
2182 old_generation()->cancel_marking();
2183 }
2184
2185 global_generation()->cancel_marking();
2186
2187 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2188 }
2189
2190 bool ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2191 if (try_cancel_gc(cause)) {
2192 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2193 log_info(gc,thread)("%s", msg.buffer());
2194 Events::log(Thread::current(), "%s", msg.buffer());
2195 _cancel_requested_time = os::elapsedTime();
2196 return true;
2197 }
2198 return false;
2199 }
2200
2201 uint ShenandoahHeap::max_workers() {
2202 return _max_workers;
2203 }
2204
2205 void ShenandoahHeap::stop() {
2206 // The shutdown sequence should be able to terminate when GC is running.
2207
2208 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2209 _shenandoah_policy->record_shutdown();
2210
2211 // Step 1. Stop reporting on gc thread cpu utilization
2212 mmu_tracker()->stop();
2213
2214 // Step 2. Wait until GC worker exits normally (this will cancel any ongoing GC).
2215 control_thread()->stop();
2216
2217 // Stop 4. Shutdown uncommit thread.
2218 if (_uncommit_thread != nullptr) {
2219 _uncommit_thread->stop();
2220 }
2221 }
2222
2223 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2224 if (!unload_classes()) return;
2225 ClassUnloadingContext ctx(_workers->active_workers(),
2226 true /* unregister_nmethods_during_purge */,
2227 false /* lock_nmethod_free_separately */);
2228
2229 // Unload classes and purge SystemDictionary.
2230 {
2231 ShenandoahPhaseTimings::Phase phase = full_gc ?
2232 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2233 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2234 ShenandoahIsAliveSelector is_alive;
2235 {
2236 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2237 ShenandoahGCPhase gc_phase(phase);
2238 ShenandoahGCWorkerPhase worker_phase(phase);
2239 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2240
2241 // Clean JVMCI metadata handles.
2242 JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
2243
2244 ShenandoahClassUnloadingTask unlink_task(phase, unloading_occurred);
2245 _workers->run_task(&unlink_task);
2246 }
2247 // Release unloaded nmethods's memory.
2248 ClassUnloadingContext::context()->purge_and_free_nmethods();
2249 }
2250
2251 {
2252 ShenandoahGCPhase phase(full_gc ?
2253 ShenandoahPhaseTimings::full_gc_purge_cldg :
2254 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2255 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2256 }
2257 // Resize and verify metaspace
2258 MetaspaceGC::compute_new_size();
2259 DEBUG_ONLY(MetaspaceUtils::verify();)
2260 }
2261
2262 // Weak roots are either pre-evacuated (final mark) or updated (final update refs),
2263 // so they should not have forwarded oops.
2264 // However, we do need to "null" dead oops in the roots, if can not be done
2265 // in concurrent cycles.
2266 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2267 uint num_workers = _workers->active_workers();
2268 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2269 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2270 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2271 ShenandoahGCPhase phase(timing_phase);
2272 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2273 // Cleanup weak roots
2274 if (has_forwarded_objects()) {
2275 ShenandoahForwardedIsAliveClosure is_alive;
2276 ShenandoahNonConcUpdateRefsClosure keep_alive;
2277 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2278 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2279 _workers->run_task(&cleaning_task);
2280 } else {
2281 ShenandoahIsAliveClosure is_alive;
2282 #ifdef ASSERT
2283 ShenandoahAssertNotForwardedClosure verify_cl;
2284 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2285 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2286 #else
2287 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2288 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2289 #endif
2290 _workers->run_task(&cleaning_task);
2291 }
2292 }
2293
2294 void ShenandoahHeap::parallel_cleaning(ShenandoahGeneration* generation, bool full_gc) {
2295 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2296 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2297 ShenandoahGCPhase phase(full_gc ?
2298 ShenandoahPhaseTimings::full_gc_purge :
2299 ShenandoahPhaseTimings::degen_gc_purge);
2300 stw_weak_refs(generation, full_gc);
2301 stw_process_weak_roots(full_gc);
2302 stw_unload_classes(full_gc);
2303 }
2304
2305 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2306 set_gc_state_at_safepoint(HAS_FORWARDED, cond);
2307 }
2308
2309 void ShenandoahHeap::set_unload_classes(bool uc) {
2310 _unload_classes.set_cond(uc);
2311 }
2312
2313 bool ShenandoahHeap::unload_classes() const {
2314 return _unload_classes.is_set();
2315 }
2316
2317 address ShenandoahHeap::in_cset_fast_test_addr() {
2318 ShenandoahHeap* heap = ShenandoahHeap::heap();
2319 assert(heap->collection_set() != nullptr, "Sanity");
2320 return (address) heap->collection_set()->biased_map_address();
2321 }
2322
2323 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2324 // It is important to force_alloc_rate_sample() before the associated generation's bytes_allocated has been reset.
2325 // Note that there is no lock to prevent additional alloations between sampling bytes_allocated_since_gc_start() and
2326 // reset_bytes_allocated_since_gc_start(). If additional allocations happen, they will be ignored in the average
2327 // allocation rate computations. This effect is considered to be be negligible.
2328
2329 // unaccounted_bytes is the bytes not accounted for by our forced sample. If the sample interval is too short,
2330 // the "forced sample" will not happen, and any recently allocated bytes are "unaccounted for". We pretend these
2331 // bytes are allocated after the start of subsequent gc.
2332 size_t unaccounted_bytes;
2333 ShenandoahFreeSet* _free_set = free_set();
2334 size_t bytes_allocated = _free_set->get_bytes_allocated_since_gc_start();
2335 if (mode()->is_generational()) {
2336 unaccounted_bytes = young_generation()->heuristics()->force_alloc_rate_sample(bytes_allocated);
2337 } else {
2338 // Single-gen Shenandoah uses global heuristics.
2339 unaccounted_bytes = heuristics()->force_alloc_rate_sample(bytes_allocated);
2340 }
2341 ShenandoahHeapLocker locker(lock());
2342 _free_set->reset_bytes_allocated_since_gc_start(unaccounted_bytes);
2343 }
2344
2345 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2346 _degenerated_gc_in_progress.set_cond(in_progress);
2347 }
2348
2349 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2350 _full_gc_in_progress.set_cond(in_progress);
2351 }
2352
2353 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2354 assert (is_full_gc_in_progress(), "should be");
2355 _full_gc_move_in_progress.set_cond(in_progress);
2356 }
2357
2358 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2359 set_gc_state_at_safepoint(UPDATE_REFS, in_progress);
2360 }
2361
2362 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2363 ShenandoahCodeRoots::register_nmethod(nm);
2364 }
2365
2366 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2367 ShenandoahCodeRoots::unregister_nmethod(nm);
2368 }
2369
2370 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2371 heap_region_containing(o)->record_pin();
2372 }
2373
2374 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2375 ShenandoahHeapRegion* r = heap_region_containing(o);
2376 assert(r != nullptr, "Sanity");
2377 assert(r->pin_count() > 0, "Region %zu should have non-zero pins", r->index());
2378 r->record_unpin();
2379 }
2380
2381 void ShenandoahHeap::sync_pinned_region_status() {
2382 ShenandoahHeapLocker locker(lock());
2383
2384 for (size_t i = 0; i < num_regions(); i++) {
2385 ShenandoahHeapRegion *r = get_region(i);
2386 if (r->is_active()) {
2387 if (r->is_pinned()) {
2388 if (r->pin_count() == 0) {
2389 r->make_unpinned();
2390 }
2391 } else {
2392 if (r->pin_count() > 0) {
2393 r->make_pinned();
2394 }
2395 }
2396 }
2397 }
2398
2399 assert_pinned_region_status();
2400 }
2401
2402 #ifdef ASSERT
2403 void ShenandoahHeap::assert_pinned_region_status() const {
2404 assert_pinned_region_status(global_generation());
2405 }
2406
2407 void ShenandoahHeap::assert_pinned_region_status(ShenandoahGeneration* generation) const {
2408 for (size_t i = 0; i < num_regions(); i++) {
2409 ShenandoahHeapRegion* r = get_region(i);
2410 if (generation->contains(r)) {
2411 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2412 "Region %zu pinning status is inconsistent", i);
2413 }
2414 }
2415 }
2416 #endif
2417
2418 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2419 return _gc_timer;
2420 }
2421
2422 void ShenandoahHeap::prepare_concurrent_roots() {
2423 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2424 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2425 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2426 set_concurrent_weak_root_in_progress(true);
2427 if (unload_classes()) {
2428 _unloader.prepare();
2429 }
2430 }
2431
2432 void ShenandoahHeap::finish_concurrent_roots() {
2433 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2434 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2435 if (unload_classes()) {
2436 _unloader.finish();
2437 }
2438 }
2439
2440 #ifdef ASSERT
2441 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2442 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2443
2444 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2445 // Use ParallelGCThreads inside safepoints
2446 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2447 ParallelGCThreads, nworkers);
2448 } else {
2449 // Use ConcGCThreads outside safepoints
2450 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2451 ConcGCThreads, nworkers);
2452 }
2453 }
2454 #endif
2455
2456 ShenandoahVerifier* ShenandoahHeap::verifier() {
2457 guarantee(ShenandoahVerify, "Should be enabled");
2458 assert (_verifier != nullptr, "sanity");
2459 return _verifier;
2460 }
2461
2462 template<bool CONCURRENT>
2463 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2464 private:
2465 ShenandoahHeap* _heap;
2466 ShenandoahRegionIterator* _regions;
2467 public:
2468 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2469 WorkerTask("Shenandoah Update References"),
2470 _heap(ShenandoahHeap::heap()),
2471 _regions(regions) {
2472 }
2473
2474 void work(uint worker_id) {
2475 if (CONCURRENT) {
2476 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2477 ShenandoahSuspendibleThreadSetJoiner stsj;
2478 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2479 } else {
2480 ShenandoahParallelWorkerSession worker_session(worker_id);
2481 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2482 }
2483 }
2484
2485 private:
2486 template<class T>
2487 void do_work(uint worker_id) {
2488 if (CONCURRENT && (worker_id == 0)) {
2489 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2490 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2491 size_t cset_regions = _heap->collection_set()->count();
2492
2493 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2494 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2495 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2496 // next GC cycle.
2497 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2498 }
2499 // If !CONCURRENT, there's no value in expanding Mutator free set
2500 T cl;
2501 ShenandoahHeapRegion* r = _regions->next();
2502 while (r != nullptr) {
2503 HeapWord* update_watermark = r->get_update_watermark();
2504 assert (update_watermark >= r->bottom(), "sanity");
2505 if (r->is_active() && !r->is_cset()) {
2506 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2507 }
2508 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2509 return;
2510 }
2511 r = _regions->next();
2512 }
2513 }
2514 };
2515
2516 void ShenandoahHeap::update_heap_references(ShenandoahGeneration* generation, bool concurrent) {
2517 assert(generation->is_global(), "Should only get global generation here");
2518 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2519
2520 if (concurrent) {
2521 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2522 workers()->run_task(&task);
2523 } else {
2524 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2525 workers()->run_task(&task);
2526 }
2527 }
2528
2529 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2530 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2531 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2532
2533 {
2534 ShenandoahGCPhase phase(concurrent ?
2535 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2536 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2537
2538 final_update_refs_update_region_states();
2539
2540 assert_pinned_region_status();
2541 }
2542
2543 {
2544 ShenandoahGCPhase phase(concurrent ?
2545 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2546 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2547 trash_cset_regions();
2548 }
2549 }
2550
2551 void ShenandoahHeap::final_update_refs_update_region_states() {
2552 ShenandoahSynchronizePinnedRegionStates cl;
2553 parallel_heap_region_iterate(&cl);
2554 }
2555
2556 void ShenandoahHeap::rebuild_free_set_within_phase() {
2557 ShenandoahHeapLocker locker(lock());
2558 size_t young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count;
2559 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count);
2560 // If there are no old regions, first_old_region will be greater than last_old_region
2561 assert((first_old_region > last_old_region) ||
2562 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2563 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2564 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu",
2565 old_region_count, first_old_region, last_old_region);
2566
2567 if (mode()->is_generational()) {
2568 #ifdef ASSERT
2569 if (ShenandoahVerify) {
2570 verifier()->verify_before_rebuilding_free_set();
2571 }
2572 #endif
2573
2574 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2575 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2576 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2577 size_t allocation_runway =
2578 gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_trashed_regions);
2579 gen_heap->compute_old_generation_balance(allocation_runway, old_trashed_regions, young_trashed_regions);
2580 }
2581 // Rebuild free set based on adjusted generation sizes.
2582 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, old_region_count);
2583
2584 if (mode()->is_generational()) {
2585 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2586 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2587 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2588 }
2589 }
2590
2591 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2592 ShenandoahGCPhase phase(concurrent ?
2593 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2594 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2595 rebuild_free_set_within_phase();
2596 }
2597
2598 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2599 size_t slice = r->index() / _bitmap_regions_per_slice;
2600
2601 size_t regions_from = _bitmap_regions_per_slice * slice;
2602 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2603 for (size_t g = regions_from; g < regions_to; g++) {
2604 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2605 if (skip_self && g == r->index()) continue;
2606 if (get_region(g)->is_committed()) {
2607 return true;
2608 }
2609 }
2610 return false;
2611 }
2612
2613 void ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2614 shenandoah_assert_heaplocked();
2615 assert(!is_bitmap_region_special(), "Not for special memory");
2616
2617 if (is_bitmap_slice_committed(r, true)) {
2618 // Some other region from the group is already committed, meaning the bitmap
2619 // slice is already committed, we exit right away.
2620 return;
2621 }
2622
2623 // Commit the bitmap slice:
2624 size_t slice = r->index() / _bitmap_regions_per_slice;
2625 size_t off = _bitmap_bytes_per_slice * slice;
2626 size_t len = _bitmap_bytes_per_slice;
2627 char* start = (char*) _bitmap_region.start() + off;
2628
2629 os::commit_memory_or_exit(start, len, false, "Unable to commit bitmap slice");
2630
2631 if (AlwaysPreTouch) {
2632 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2633 }
2634 }
2635
2636 void ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2637 shenandoah_assert_heaplocked();
2638 assert(!is_bitmap_region_special(), "Not for special memory");
2639
2640 if (is_bitmap_slice_committed(r, true)) {
2641 // Some other region from the group is still committed, meaning the bitmap
2642 // slice should stay committed, exit right away.
2643 return;
2644 }
2645
2646 // Uncommit the bitmap slice:
2647 size_t slice = r->index() / _bitmap_regions_per_slice;
2648 size_t off = _bitmap_bytes_per_slice * slice;
2649 size_t len = _bitmap_bytes_per_slice;
2650
2651 char* addr = (char*) _bitmap_region.start() + off;
2652 os::uncommit_memory(addr, len);
2653 }
2654
2655 void ShenandoahHeap::forbid_uncommit() {
2656 if (_uncommit_thread != nullptr) {
2657 _uncommit_thread->forbid_uncommit();
2658 }
2659 }
2660
2661 void ShenandoahHeap::allow_uncommit() {
2662 if (_uncommit_thread != nullptr) {
2663 _uncommit_thread->allow_uncommit();
2664 }
2665 }
2666
2667 #ifdef ASSERT
2668 bool ShenandoahHeap::is_uncommit_in_progress() {
2669 if (_uncommit_thread != nullptr) {
2670 return _uncommit_thread->is_uncommit_in_progress();
2671 }
2672 return false;
2673 }
2674 #endif
2675
2676 void ShenandoahHeap::safepoint_synchronize_begin() {
2677 StackWatermarkSet::safepoint_synchronize_begin();
2678 SuspendibleThreadSet::synchronize();
2679 }
2680
2681 void ShenandoahHeap::safepoint_synchronize_end() {
2682 SuspendibleThreadSet::desynchronize();
2683 }
2684
2685 void ShenandoahHeap::try_inject_alloc_failure() {
2686 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2687 _inject_alloc_failure.set();
2688 os::naked_short_sleep(1);
2689 if (cancelled_gc()) {
2690 log_info(gc)("Allocation failure was successfully injected");
2691 }
2692 }
2693 }
2694
2695 bool ShenandoahHeap::should_inject_alloc_failure() {
2696 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2697 }
2698
2699 void ShenandoahHeap::initialize_serviceability() {
2700 _memory_pool = new ShenandoahMemoryPool(this);
2701 _cycle_memory_manager.add_pool(_memory_pool);
2702 _stw_memory_manager.add_pool(_memory_pool);
2703 }
2704
2705 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2706 GrowableArray<GCMemoryManager*> memory_managers(2);
2707 memory_managers.append(&_cycle_memory_manager);
2708 memory_managers.append(&_stw_memory_manager);
2709 return memory_managers;
2710 }
2711
2712 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2713 GrowableArray<MemoryPool*> memory_pools(1);
2714 memory_pools.append(_memory_pool);
2715 return memory_pools;
2716 }
2717
2718 MemoryUsage ShenandoahHeap::memory_usage() {
2719 assert(_initial_size <= ShenandoahHeap::heap()->max_capacity(), "sanity");
2720 assert(used() <= ShenandoahHeap::heap()->max_capacity(), "sanity");
2721 assert(committed() <= ShenandoahHeap::heap()->max_capacity(), "sanity");
2722 return MemoryUsage(_initial_size, used(), committed(), max_capacity());
2723 }
2724
2725 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2726 _heap(ShenandoahHeap::heap()),
2727 _index(0) {}
2728
2729 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2730 _heap(heap),
2731 _index(0) {}
2732
2733 void ShenandoahRegionIterator::reset() {
2734 _index.store_relaxed(0);
2735 }
2736
2737 bool ShenandoahRegionIterator::has_next() const {
2738 return _index.load_relaxed() < _heap->num_regions();
2739 }
2740
2741 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2742 #ifdef ASSERT
2743 assert(_liveness_cache != nullptr, "sanity");
2744 assert(worker_id < _max_workers, "sanity");
2745 for (uint i = 0; i < num_regions(); i++) {
2746 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2747 }
2748 #endif
2749 return _liveness_cache[worker_id];
2750 }
2751
2752 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2753 assert(worker_id < _max_workers, "sanity");
2754 assert(_liveness_cache != nullptr, "sanity");
2755 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2756 for (uint i = 0; i < num_regions(); i++) {
2757 ShenandoahLiveData live = ld[i];
2758 if (live > 0) {
2759 ShenandoahHeapRegion* r = get_region(i);
2760 r->increase_live_data_gc_words(live);
2761 ld[i] = 0;
2762 }
2763 }
2764 }
2765
2766 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2767 if (is_idle()) return false;
2768
2769 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2770 // marking phase.
2771 if (is_concurrent_mark_in_progress() &&
2772 !marking_context()->allocated_after_mark_start(obj)) {
2773 return true;
2774 }
2775
2776 // Can not guarantee obj is deeply good.
2777 if (has_forwarded_objects()) {
2778 return true;
2779 }
2780
2781 return false;
2782 }
2783
2784 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2785 #if INCLUDE_CDS_JAVA_HEAP
2786 // CDS wants a raw continuous memory range to load a bunch of objects itself.
2787 // This is an unusual request, since all requested regions should be regular, not humongous.
2788 //
2789 // CDS would guarantee no objects straddle multiple regions, as long as regions are as large
2790 // as MIN_GC_REGION_ALIGNMENT.
2791 guarantee(ShenandoahHeapRegion::region_size_bytes() >= AOTMappedHeapWriter::MIN_GC_REGION_ALIGNMENT, "Must be");
2792
2793 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_cds(size);
2794 return allocate_memory(req);
2795 #else
2796 assert(false, "Archive heap loader should not be available, should not be here");
2797 return nullptr;
2798 #endif // INCLUDE_CDS_JAVA_HEAP
2799 }
2800
2801 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2802 // Nothing to do here, except checking that heap looks fine.
2803 #ifdef ASSERT
2804 HeapWord* start = archive_space.start();
2805 HeapWord* end = archive_space.end();
2806
2807 // No unclaimed space between the objects.
2808 // Objects are properly allocated in correct regions.
2809 HeapWord* cur = start;
2810 while (cur < end) {
2811 oop oop = cast_to_oop(cur);
2812 shenandoah_assert_in_correct_region(nullptr, oop);
2813 cur += oop->size();
2814 }
2815
2816 // No unclaimed tail at the end of archive space.
2817 assert(cur == end,
2818 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2819 p2i(cur), p2i(end));
2820
2821 // All regions in contiguous space have good state.
2822 size_t begin_reg_idx = heap_region_index_containing(start);
2823 size_t end_reg_idx = heap_region_index_containing(end);
2824
2825 for (size_t idx = begin_reg_idx; idx <= end_reg_idx; idx++) {
2826 ShenandoahHeapRegion* r = get_region(idx);
2827 assert(r->is_regular(), "Must be regular");
2828 assert(r->is_young(), "Must be young");
2829 assert(idx == end_reg_idx || r->top() == r->end(),
2830 "All regions except the last one should be full: " PTR_FORMAT " " PTR_FORMAT,
2831 p2i(r->top()), p2i(r->end()));
2832 assert(idx != begin_reg_idx || r->bottom() == start,
2833 "Archive space start should be at the bottom of first region: " PTR_FORMAT " " PTR_FORMAT,
2834 p2i(r->bottom()), p2i(start));
2835 assert(idx != end_reg_idx || r->top() == end,
2836 "Archive space end should be at the top of last region: " PTR_FORMAT " " PTR_FORMAT,
2837 p2i(r->top()), p2i(end));
2838 }
2839
2840 #endif
2841 }
2842
2843 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2844 if (!mode()->is_generational()) {
2845 return global_generation();
2846 } else if (affiliation == YOUNG_GENERATION) {
2847 return young_generation();
2848 } else if (affiliation == OLD_GENERATION) {
2849 return old_generation();
2850 }
2851
2852 ShouldNotReachHere();
2853 return nullptr;
2854 }
2855
2856 void ShenandoahHeap::log_heap_status(const char* msg) const {
2857 if (mode()->is_generational()) {
2858 young_generation()->log_status(msg);
2859 old_generation()->log_status(msg);
2860 } else {
2861 global_generation()->log_status(msg);
2862 }
2863 }
2864
2865 ShenandoahHeapLocker::ShenandoahHeapLocker(ShenandoahHeapLock* lock, bool allow_block_for_safepoint) : _lock(lock) {
2866 #ifdef ASSERT
2867 ShenandoahFreeSet* free_set = ShenandoahHeap::heap()->free_set();
2868 // free_set is nullptr only at pre-initialized state
2869 assert(free_set == nullptr || !free_set->rebuild_lock()->owned_by_self(), "Dead lock, can't acquire heap lock while holding free-set rebuild lock");
2870 assert(_lock != nullptr, "Must not");
2871 #endif
2872 _lock->lock(allow_block_for_safepoint);
2873 }