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.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("ShenWorker", _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 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1186 assert(shenandoah_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 shenandoah_plab->retire();
1192
1193 // Re-enable promotions for the next evacuation phase.
1194 shenandoah_plab->enable_promotions();
1195
1196 // Reset the fill size for next evacuation phase.
1197 if (_resize && shenandoah_plab->desired_size() > 0) {
1198 shenandoah_plab->set_desired_size(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), _gc_state_fast(ShenandoahThreadLocalData::compute_gc_state_fast(gc_state)) {}
1209
1210 void do_thread(Thread* thread) override {
1211 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state, _gc_state_fast);
1212 }
1213 private:
1214 char _gc_state;
1215 char _gc_state_fast;
1216 };
1217
1218 class ShenandoahPrepareForUpdateRefsHandshakeClosure : public HandshakeClosure {
1219 public:
1220 explicit ShenandoahPrepareForUpdateRefsHandshakeClosure(char gc_state) :
1221 HandshakeClosure("Shenandoah Prepare for Update Refs"),
1222 _retire(ResizeTLAB), _propagator(gc_state) {}
1223
1224 void do_thread(Thread* thread) override {
1225 _propagator.do_thread(thread);
1226 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) {
1227 _retire.do_thread(thread);
1228 }
1229 }
1230 private:
1231 ShenandoahRetireGCLABClosure _retire;
1232 ShenandoahGCStatePropagatorHandshakeClosure _propagator;
1233 };
1234
1235 void ShenandoahHeap::evacuate_collection_set(ShenandoahGeneration* generation, bool concurrent) {
1236 if (concurrent && ShenandoahWeakRootsEarly) {
1237 // Turn weak roots off now, so that weak barriers do not go slow.
1238 {
1239 MutexLocker lock(Threads_lock);
1240 set_gc_state_concurrent(WEAK_ROOTS, false);
1241 }
1242
1243 ShenandoahGCStatePropagatorHandshakeClosure propagate_gc_state(_gc_state.raw_value());
1244 Threads::non_java_threads_do(&propagate_gc_state);
1245 Handshake::execute(&propagate_gc_state);
1246 }
1247
1248 assert(generation->is_global(), "Only global generation expected here");
1249 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1250 workers()->run_task(&task);
1251 }
1252
1253 void ShenandoahHeap::concurrent_prepare_for_update_refs() {
1254 {
1255 // Java threads take this lock while they are being attached and added to the list of threads.
1256 // If another thread holds this lock before we update the gc state, it will receive a stale
1257 // gc state, but they will have been added to the list of java threads and so will be corrected
1258 // by the following handshake.
1259 MutexLocker lock(Threads_lock);
1260
1261 // A cancellation at this point means the degenerated cycle must resume from update-refs.
1262 set_gc_state_concurrent(EVACUATION, false);
1263 set_gc_state_concurrent(UPDATE_REFS, true);
1264 if (!ShenandoahWeakRootsEarly) {
1265 set_gc_state_concurrent(WEAK_ROOTS, false);
1266 }
1267 }
1268
1269 // This will propagate the gc state and retire gclabs and plabs for threads that require it.
1270 ShenandoahPrepareForUpdateRefsHandshakeClosure prepare_for_update_refs(_gc_state.raw_value());
1271
1272 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately.
1273 Threads::non_java_threads_do(&prepare_for_update_refs);
1274
1275 // Now retire gclabs and plabs and propagate gc_state for mutator threads
1276 Handshake::execute(&prepare_for_update_refs);
1277
1278 _update_refs_iterator.reset();
1279 }
1280
1281 class ShenandoahCompositeHandshakeClosure : public HandshakeClosure {
1282 HandshakeClosure* _handshake_1;
1283 HandshakeClosure* _handshake_2;
1284 public:
1285 ShenandoahCompositeHandshakeClosure(HandshakeClosure* handshake_1, HandshakeClosure* handshake_2) :
1286 HandshakeClosure(handshake_2->name()),
1287 _handshake_1(handshake_1), _handshake_2(handshake_2) {}
1288
1289 void do_thread(Thread* thread) override {
1290 _handshake_1->do_thread(thread);
1291 _handshake_2->do_thread(thread);
1292 }
1293 };
1294
1295 void ShenandoahHeap::concurrent_final_roots(HandshakeClosure* handshake_closure) {
1296 {
1297 assert(!is_evacuation_in_progress(), "Should not evacuate for abbreviated or old cycles");
1298 MutexLocker lock(Threads_lock);
1299 set_gc_state_concurrent(WEAK_ROOTS, false);
1300 }
1301
1302 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
1303 Threads::non_java_threads_do(&propagator);
1304 if (handshake_closure == nullptr) {
1305 Handshake::execute(&propagator);
1306 } else {
1307 ShenandoahCompositeHandshakeClosure composite(&propagator, handshake_closure);
1308 Handshake::execute(&composite);
1309 }
1310 }
1311
1312 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1313 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1314 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
1315 // This thread went through the OOM during evac protocol. It is safe to return
1316 // the forward pointer. It must not attempt to evacuate any other objects.
1317 return ShenandoahBarrierSet::resolve_forwarded(p);
1318 }
1319
1320 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1321
1322 ShenandoahHeapRegion* r = heap_region_containing(p);
1323 assert(!r->is_humongous(), "never evacuate humongous objects");
1324
1325 ShenandoahAffiliation target_gen = r->affiliation();
1326 return try_evacuate_object(p, thread, r, target_gen);
1327 }
1328
1329 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1330 ShenandoahAffiliation target_gen) {
1331 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1332 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1333 bool alloc_from_lab = true;
1334 HeapWord* copy = nullptr;
1335 size_t size = ShenandoahForwarding::size(p);
1336
1337 #ifdef ASSERT
1338 if (ShenandoahOOMDuringEvacALot &&
1339 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1340 copy = nullptr;
1341 } else {
1342 #endif
1343 if (UseTLAB) {
1344 copy = allocate_from_gclab(thread, size);
1345 }
1346 if (copy == nullptr) {
1347 // If we failed to allocate in LAB, we'll try a shared allocation.
1348 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1349 copy = allocate_memory(req);
1350 alloc_from_lab = false;
1351 }
1352 #ifdef ASSERT
1353 }
1354 #endif
1355
1356 if (copy == nullptr) {
1357 control_thread()->handle_alloc_failure_evac(size);
1358
1359 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1360
1361 return ShenandoahBarrierSet::resolve_forwarded(p);
1362 }
1363
1364 if (ShenandoahEvacTracking) {
1365 evac_tracker()->begin_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1366 }
1367
1368 // Copy the object:
1369 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1370
1371 oop copy_val = cast_to_oop(copy);
1372
1373 // Relativize stack chunks before publishing the copy. After the forwarding CAS,
1374 // mutators can see the copy and thaw it via the fast path if flags == 0. We must
1375 // relativize derived pointers and set gc_mode before that happens. Skip if the
1376 // copy's mark word is already a forwarding pointer (another thread won the race
1377 // and overwrote the original's header before we copied it).
1378 if (!ShenandoahForwarding::is_forwarded(copy_val)) {
1379 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1380 }
1381
1382 // Try to install the new forwarding pointer.
1383 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1384 if (result == copy_val) {
1385 // Successfully evacuated. Our copy is now the public one!
1386 shenandoah_assert_correct(nullptr, copy_val);
1387 if (ShenandoahEvacTracking) {
1388 evac_tracker()->end_evacuation(thread, size * HeapWordSize, from_region->affiliation(), target_gen);
1389 }
1390 return copy_val;
1391 } else {
1392 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1393 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1394 // But if it happens to contain references to evacuated regions, those references would
1395 // not get updated for this stale copy during this cycle, and we will crash while scanning
1396 // it the next cycle.
1397 if (alloc_from_lab) {
1398 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1399 // object will overwrite this stale copy, or the filler object on LAB retirement will
1400 // do this.
1401 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1402 } else {
1403 // For non-LAB allocations, we have no way to retract the allocation, and
1404 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1405 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1406 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1407 fill_with_object(copy, size);
1408 shenandoah_assert_correct(nullptr, copy_val);
1409 // For non-LAB allocations, the object has already been registered
1410 }
1411 shenandoah_assert_correct(nullptr, result);
1412 return result;
1413 }
1414 }
1415
1416 void ShenandoahHeap::trash_cset_regions() {
1417 ShenandoahHeapLocker locker(lock());
1418
1419 ShenandoahCollectionSet* set = collection_set();
1420 ShenandoahHeapRegion* r;
1421 set->clear_current_index();
1422 while ((r = set->next()) != nullptr) {
1423 r->make_trash();
1424 }
1425 collection_set()->clear();
1426 }
1427
1428 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1429 st->print_cr("Heap Regions:");
1430 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1431 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1432 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1433 st->print_cr("UWM=update watermark, U=used");
1434 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1435 st->print_cr("S=shared allocs, L=live data");
1436 st->print_cr("CP=critical pins");
1437
1438 for (size_t i = 0; i < num_regions(); i++) {
1439 get_region(i)->print_on(st);
1440 }
1441 }
1442
1443 void ShenandoahHeap::process_gc_stats() const {
1444 // Commit worker statistics to cycle data
1445 phase_timings()->flush_par_workers_to_cycle();
1446
1447 // Print GC stats for current cycle
1448 LogTarget(Info, gc, stats) lt;
1449 if (lt.is_enabled()) {
1450 ResourceMark rm;
1451 LogStream ls(lt);
1452 phase_timings()->print_cycle_on(&ls);
1453 if (ShenandoahEvacTracking) {
1454 ShenandoahCycleStats evac_stats = evac_tracker()->flush_cycle_to_global();
1455 evac_tracker()->print_evacuations_on(&ls, &evac_stats.workers,
1456 &evac_stats.mutators);
1457 }
1458 }
1459
1460 // Commit statistics to globals
1461 phase_timings()->flush_cycle_to_global();
1462 }
1463
1464 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) const {
1465 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1466 assert(!start->has_live(), "liveness must be zero");
1467
1468 // Do not try to get the size of this humongous object. STW collections will
1469 // have already unloaded classes, so an unmarked object may have a bad klass pointer.
1470 ShenandoahHeapRegion* region = start;
1471 size_t index = region->index();
1472 do {
1473 assert(region->is_humongous(), "Expect correct humongous start or continuation");
1474 assert(!region->is_cset(), "Humongous region should not be in collection set");
1475 region->make_trash_immediate();
1476 region = get_region(++index);
1477 } while (region != nullptr && region->is_humongous_continuation());
1478
1479 // Return number of regions trashed
1480 return index - start->index();
1481 }
1482
1483 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1484 public:
1485 ShenandoahCheckCleanGCLABClosure() {}
1486 void do_thread(Thread* thread) {
1487 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1488 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1489 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1490
1491 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1492 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
1493 assert(shenandoah_plab != nullptr, "PLAB should be initialized for %s", thread->name());
1494 assert(shenandoah_plab->plab()->words_remaining() == 0, "PLAB should not need retirement");
1495 }
1496 }
1497 };
1498
1499 void ShenandoahHeap::labs_make_parsable() {
1500 assert(UseTLAB, "Only call with UseTLAB");
1501
1502 ShenandoahRetireGCLABClosure cl(false);
1503
1504 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1505 ThreadLocalAllocBuffer& tlab = t->tlab();
1506 tlab.make_parsable();
1507 if (ZeroTLAB) {
1508 t->retire_tlab();
1509 }
1510 cl.do_thread(t);
1511 }
1512
1513 workers()->threads_do(&cl);
1514
1515 if (safepoint_workers() != nullptr) {
1516 safepoint_workers()->threads_do(&cl);
1517 }
1518 }
1519
1520 void ShenandoahHeap::tlabs_retire(bool resize) {
1521 assert(UseTLAB, "Only call with UseTLAB");
1522 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1523
1524 ThreadLocalAllocStats stats;
1525
1526 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1527 t->retire_tlab(&stats);
1528 if (resize) {
1529 t->tlab().resize();
1530 }
1531 }
1532
1533 stats.publish();
1534
1535 #ifdef ASSERT
1536 ShenandoahCheckCleanGCLABClosure cl;
1537 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1538 cl.do_thread(t);
1539 }
1540 workers()->threads_do(&cl);
1541 #endif
1542 }
1543
1544 void ShenandoahHeap::gclabs_retire(bool resize) {
1545 assert(UseTLAB, "Only call with UseTLAB");
1546 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1547
1548 ShenandoahRetireGCLABClosure cl(resize);
1549 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1550 cl.do_thread(t);
1551 }
1552
1553 workers()->threads_do(&cl);
1554
1555 if (safepoint_workers() != nullptr) {
1556 safepoint_workers()->threads_do(&cl);
1557 }
1558 }
1559
1560 // Returns size in bytes
1561 size_t ShenandoahHeap::unsafe_max_tlab_alloc() const {
1562 // Return the max allowed size, and let the allocation path
1563 // figure out the safe size for current allocation.
1564 return ShenandoahHeapRegion::max_tlab_size_bytes();
1565 }
1566
1567 size_t ShenandoahHeap::max_tlab_size() const {
1568 // Returns size in words
1569 return ShenandoahHeapRegion::max_tlab_size_words();
1570 }
1571
1572 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) {
1573 // These requests are ignored because we can't easily have Shenandoah jump into
1574 // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent
1575 // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly
1576 // on the VM thread, but this would confuse the control thread mightily and doesn't
1577 // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a
1578 // concurrent cycle in the prologue of the heap inspect/dump operation (see VM_HeapDumper::doit_prologue).
1579 // This is how other concurrent collectors in the JVM handle this scenario as well.
1580 assert(Thread::current()->is_VM_thread(), "Should be the VM thread");
1581 guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause");
1582 }
1583
1584 void ShenandoahHeap::collect(GCCause::Cause cause) {
1585 control_thread()->request_gc(cause);
1586 }
1587
1588 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1589 // This method is only called by `CollectedHeap::collect_as_vm_thread`, which we have
1590 // overridden to do nothing. See the comment there for an explanation of how heap inspections
1591 // work for Shenandoah.
1592 ShouldNotReachHere();
1593 }
1594
1595 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1596 ShenandoahHeapRegion* r = heap_region_containing(addr);
1597 if (r != nullptr) {
1598 return r->block_start(addr);
1599 }
1600 return nullptr;
1601 }
1602
1603 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1604 ShenandoahHeapRegion* r = heap_region_containing(addr);
1605 return r->block_is_obj(addr);
1606 }
1607
1608 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1609 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1610 }
1611
1612 void ShenandoahHeap::prepare_for_verify() {
1613 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1614 labs_make_parsable();
1615 }
1616 }
1617
1618 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1619 if (_shenandoah_policy->is_at_shutdown()) {
1620 return;
1621 }
1622
1623 if (_control_thread != nullptr) {
1624 tcl->do_thread(_control_thread);
1625 }
1626
1627 if (_uncommit_thread != nullptr) {
1628 tcl->do_thread(_uncommit_thread);
1629 }
1630
1631 workers()->threads_do(tcl);
1632 if (_safepoint_workers != nullptr) {
1633 _safepoint_workers->threads_do(tcl);
1634 }
1635 }
1636
1637 void ShenandoahHeap::print_tracing_info() const {
1638 LogTarget(Info, gc, stats) lt;
1639 if (lt.is_enabled()) {
1640 ResourceMark rm;
1641 LogStream ls(lt);
1642
1643 if (ShenandoahEvacTracking) {
1644 evac_tracker()->print_global_on(&ls);
1645 ls.cr();
1646 ls.cr();
1647 }
1648
1649 phase_timings()->print_global_on(&ls);
1650
1651 ls.cr();
1652 ls.cr();
1653
1654 shenandoah_policy()->print_gc_stats(&ls);
1655
1656 ls.cr();
1657 ls.cr();
1658 }
1659 }
1660
1661 // Active generation may only be set by the VM thread at a safepoint.
1662 void ShenandoahHeap::set_active_generation(ShenandoahGeneration* generation) {
1663 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1664 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1665 _active_generation = generation;
1666 }
1667
1668 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
1669 shenandoah_policy()->record_collection_cause(cause);
1670
1671 const GCCause::Cause current = gc_cause();
1672 assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s",
1673 GCCause::to_string(current), GCCause::to_string(cause));
1674
1675 set_gc_cause(cause);
1676
1677 generation->heuristics()->record_cycle_start();
1678 }
1679
1680 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1681 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1682
1683 generation->heuristics()->record_cycle_end();
1684 if (mode()->is_generational() && generation->is_global()) {
1685 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1686 young_generation()->heuristics()->record_cycle_end();
1687 old_generation()->heuristics()->record_cycle_end();
1688 }
1689
1690 set_gc_cause(GCCause::_no_gc);
1691 }
1692
1693 void ShenandoahHeap::verify(VerifyOption vo) {
1694 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1695 if (ShenandoahVerify) {
1696 verifier()->verify_generic(active_generation(), vo);
1697 } else {
1698 // TODO: Consider allocating verification bitmaps on demand,
1699 // and turn this on unconditionally.
1700 }
1701 }
1702 }
1703 size_t ShenandoahHeap::tlab_capacity() const {
1704 return _free_set->capacity_not_holding_lock();
1705 }
1706
1707 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1708 private:
1709 MarkBitMap* _bitmap;
1710 ShenandoahScanObjectStack* _oop_stack;
1711 ShenandoahHeap* const _heap;
1712 ShenandoahMarkingContext* const _marking_context;
1713
1714 template <class T>
1715 void do_oop_work(T* p) {
1716 T o = RawAccess<>::oop_load(p);
1717 if (!CompressedOops::is_null(o)) {
1718 oop obj = CompressedOops::decode_not_null(o);
1719 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1720 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1721 return;
1722 }
1723 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1724
1725 assert(oopDesc::is_oop(obj), "must be a valid oop");
1726 if (!_bitmap->is_marked(obj)) {
1727 _bitmap->mark(obj);
1728 _oop_stack->push(obj);
1729 }
1730 }
1731 }
1732 public:
1733 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1734 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1735 _marking_context(_heap->marking_context()) {}
1736 void do_oop(oop* p) { do_oop_work(p); }
1737 void do_oop(narrowOop* p) { do_oop_work(p); }
1738 };
1739
1740 /*
1741 * This is public API, used in preparation of object_iterate().
1742 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1743 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1744 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1745 */
1746 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1747 // No-op.
1748 }
1749
1750 /*
1751 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1752 *
1753 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1754 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1755 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1756 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1757 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1758 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1759 * wiped the bitmap in preparation for next marking).
1760 *
1761 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1762 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1763 * is allowed to report dead objects, but is not required to do so.
1764 */
1765 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1766 // Reset bitmap
1767 if (!prepare_aux_bitmap_for_iteration())
1768 return;
1769
1770 ShenandoahScanObjectStack oop_stack;
1771 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1772 // Seed the stack with root scan
1773 scan_roots_for_iteration(&oop_stack, &oops);
1774
1775 // Work through the oop stack to traverse heap
1776 while (! oop_stack.is_empty()) {
1777 oop obj = oop_stack.pop();
1778 assert(oopDesc::is_oop(obj), "must be a valid oop");
1779 cl->do_object(obj);
1780 obj->oop_iterate(&oops);
1781 }
1782
1783 assert(oop_stack.is_empty(), "should be empty");
1784 // Reclaim bitmap
1785 reclaim_aux_bitmap_for_iteration();
1786 }
1787
1788 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1789 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1790 if (!_aux_bitmap_region_special) {
1791 bool success = os::commit_memory((char *) _aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false);
1792 if (!success) {
1793 log_warning(gc)("Auxiliary marking bitmap commit failed: " PTR_FORMAT " (%zu bytes)",
1794 p2i(_aux_bitmap_region.start()), _aux_bitmap_region.byte_size());
1795 return false;
1796 }
1797 }
1798 _aux_bit_map.clear();
1799 return true;
1800 }
1801
1802 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1803 // Process GC roots according to current GC cycle
1804 // This populates the work stack with initial objects
1805 // It is important to relinquish the associated locks before diving
1806 // into heap dumper
1807 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1808 ShenandoahHeapIterationRootScanner rp(n_workers);
1809 rp.roots_do(oops);
1810 }
1811
1812 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1813 if (!_aux_bitmap_region_special) {
1814 os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size());
1815 }
1816 }
1817
1818 // Closure for parallelly iterate objects
1819 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1820 private:
1821 MarkBitMap* _bitmap;
1822 ShenandoahObjToScanQueue* _queue;
1823 ShenandoahHeap* const _heap;
1824 ShenandoahMarkingContext* const _marking_context;
1825
1826 template <class T>
1827 void do_oop_work(T* p) {
1828 T o = RawAccess<>::oop_load(p);
1829 if (!CompressedOops::is_null(o)) {
1830 oop obj = CompressedOops::decode_not_null(o);
1831 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1832 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1833 return;
1834 }
1835 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1836
1837 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1838 if (_bitmap->par_mark(obj)) {
1839 _queue->push(ShenandoahMarkTask(obj));
1840 }
1841 }
1842 }
1843 public:
1844 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1845 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1846 _marking_context(_heap->marking_context()) {}
1847 void do_oop(oop* p) { do_oop_work(p); }
1848 void do_oop(narrowOop* p) { do_oop_work(p); }
1849 };
1850
1851 // Object iterator for parallel heap iteraion.
1852 // The root scanning phase happenes in construction as a preparation of
1853 // parallel marking queues.
1854 // Every worker processes it's own marking queue. work-stealing is used
1855 // to balance workload.
1856 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1857 private:
1858 uint _num_workers;
1859 bool _init_ready;
1860 MarkBitMap* _aux_bit_map;
1861 ShenandoahHeap* _heap;
1862 ShenandoahScanObjectStack _roots_stack; // global roots stack
1863 ShenandoahObjToScanQueueSet* _task_queues;
1864 public:
1865 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1866 _num_workers(num_workers),
1867 _init_ready(false),
1868 _aux_bit_map(bitmap),
1869 _heap(ShenandoahHeap::heap()) {
1870 // Initialize bitmap
1871 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1872 if (!_init_ready) {
1873 return;
1874 }
1875
1876 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1877 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1878
1879 _init_ready = prepare_worker_queues();
1880 }
1881
1882 ~ShenandoahParallelObjectIterator() {
1883 // Reclaim bitmap
1884 _heap->reclaim_aux_bitmap_for_iteration();
1885 // Reclaim queue for workers
1886 if (_task_queues!= nullptr) {
1887 for (uint i = 0; i < _num_workers; ++i) {
1888 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1889 if (q != nullptr) {
1890 delete q;
1891 _task_queues->register_queue(i, nullptr);
1892 }
1893 }
1894 delete _task_queues;
1895 _task_queues = nullptr;
1896 }
1897 }
1898
1899 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1900 if (_init_ready) {
1901 object_iterate_parallel(cl, worker_id, _task_queues);
1902 }
1903 }
1904
1905 private:
1906 // Divide global root_stack into worker queues
1907 bool prepare_worker_queues() {
1908 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1909 // Initialize queues for every workers
1910 for (uint i = 0; i < _num_workers; ++i) {
1911 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1912 _task_queues->register_queue(i, task_queue);
1913 }
1914 // Divide roots among the workers. Assume that object referencing distribution
1915 // is related with root kind, use round-robin to make every worker have same chance
1916 // to process every kind of roots
1917 size_t roots_num = _roots_stack.size();
1918 if (roots_num == 0) {
1919 // No work to do
1920 return false;
1921 }
1922
1923 for (uint j = 0; j < roots_num; j++) {
1924 uint stack_id = j % _num_workers;
1925 oop obj = _roots_stack.pop();
1926 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1927 }
1928 return true;
1929 }
1930
1931 void object_iterate_parallel(ObjectClosure* cl,
1932 uint worker_id,
1933 ShenandoahObjToScanQueueSet* queue_set) {
1934 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1935 assert(queue_set != nullptr, "task queue must not be null");
1936
1937 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1938 assert(q != nullptr, "object iterate queue must not be null");
1939
1940 ShenandoahMarkTask t;
1941 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1942
1943 // Work through the queue to traverse heap.
1944 // Steal when there is no task in queue.
1945 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1946 oop obj = t.obj();
1947 assert(oopDesc::is_oop(obj), "must be a valid oop");
1948 cl->do_object(obj);
1949 obj->oop_iterate(&oops);
1950 }
1951 assert(q->is_empty(), "should be empty");
1952 }
1953 };
1954
1955 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1956 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1957 }
1958
1959 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1960 void ShenandoahHeap::keep_alive(oop obj) {
1961 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1962 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1963 }
1964 }
1965
1966 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1967 for (size_t i = 0; i < num_regions(); i++) {
1968 ShenandoahHeapRegion* current = get_region(i);
1969 blk->heap_region_do(current);
1970 }
1971 }
1972
1973 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1974 private:
1975 ShenandoahHeap* const _heap;
1976 ShenandoahHeapRegionClosure* const _blk;
1977 size_t const _stride;
1978
1979 shenandoah_padding(0);
1980 Atomic<size_t> _index;
1981 shenandoah_padding(1);
1982
1983 public:
1984 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
1985 WorkerTask("Shenandoah Parallel Region Operation"),
1986 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
1987
1988 void work(uint worker_id) {
1989 ShenandoahParallelWorkerSession worker_session(worker_id);
1990 size_t stride = _stride;
1991
1992 size_t max = _heap->num_regions();
1993 while (_index.load_relaxed() < max) {
1994 size_t cur = _index.fetch_then_add(stride, memory_order_relaxed);
1995 size_t start = cur;
1996 size_t end = MIN2(cur + stride, max);
1997 if (start >= max) break;
1998
1999 for (size_t i = cur; i < end; i++) {
2000 ShenandoahHeapRegion* current = _heap->get_region(i);
2001 _blk->heap_region_do(current);
2002 }
2003 }
2004 }
2005 };
2006
2007 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2008 assert(blk->is_thread_safe(), "Only thread-safe closures here");
2009 const uint active_workers = workers()->active_workers();
2010 const size_t n_regions = num_regions();
2011 size_t stride = blk->parallel_region_stride();
2012 if (stride == 0 && active_workers > 1) {
2013 // Automatically derive the stride to balance the work between threads
2014 // evenly. Do not try to split work if below the reasonable threshold.
2015 constexpr size_t threshold = 4096;
2016 stride = n_regions <= threshold ?
2017 threshold :
2018 (n_regions + active_workers - 1) / active_workers;
2019 }
2020
2021 if (n_regions > stride && active_workers > 1) {
2022 ShenandoahParallelHeapRegionTask task(blk, stride);
2023 workers()->run_task(&task);
2024 } else {
2025 heap_region_iterate(blk);
2026 }
2027 }
2028
2029 class ShenandoahRendezvousHandshakeClosure : public HandshakeClosure {
2030 public:
2031 inline ShenandoahRendezvousHandshakeClosure(const char* name) : HandshakeClosure(name) {}
2032 inline void do_thread(Thread* thread) {}
2033 };
2034
2035 void ShenandoahHeap::rendezvous_threads(const char* name) {
2036 ShenandoahRendezvousHandshakeClosure cl(name);
2037 Handshake::execute(&cl);
2038 }
2039
2040 void ShenandoahHeap::recycle_trash() {
2041 free_set()->recycle_trash();
2042 }
2043
2044 void ShenandoahHeap::do_class_unloading() {
2045 _unloader.unload();
2046 if (mode()->is_generational()) {
2047 old_generation()->set_parsable(false);
2048 }
2049 }
2050
2051 void ShenandoahHeap::stw_weak_refs(ShenandoahGeneration* generation, bool full_gc) {
2052 // Weak refs processing
2053 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2054 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2055 ShenandoahTimingsTracker t(phase);
2056 ShenandoahGCWorkerPhase worker_phase(phase);
2057 generation->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2058 }
2059
2060 void ShenandoahHeap::prepare_update_heap_references() {
2061 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2062
2063 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2064 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2065 // for future GCLABs here.
2066 if (UseTLAB) {
2067 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2068 gclabs_retire(ResizeTLAB);
2069 }
2070
2071 _update_refs_iterator.reset();
2072 }
2073
2074 void ShenandoahHeap::propagate_gc_state_to_all_threads() {
2075 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2076 if (_gc_state_changed) {
2077 // If we are only marking old, we do not need to process young pointers
2078 ShenandoahBarrierSet::satb_mark_queue_set().set_filter_out_young(
2079 is_concurrent_old_mark_in_progress() && !is_concurrent_young_mark_in_progress()
2080 );
2081 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value());
2082 Threads::threads_do(&propagator);
2083 _gc_state_changed = false;
2084 }
2085 }
2086
2087 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) {
2088 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2089 _gc_state.set_cond(mask, value);
2090 _gc_state_changed = true;
2091 }
2092
2093 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) {
2094 // Holding the thread lock here assures that any thread created after we change the gc
2095 // state will have the correct state. It also prevents attaching threads from seeing
2096 // an inconsistent state. See ShenandoahBarrierSet::on_thread_attach for reference. Established
2097 // threads will use their thread local copy of the gc state (changed by a handshake, or on a
2098 // safepoint).
2099 assert(Threads_lock->is_locked(), "Must hold thread lock for concurrent gc state change");
2100 _gc_state.set_cond(mask, value);
2101 }
2102
2103 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2104 uint mask;
2105 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2106 if (!in_progress && is_concurrent_old_mark_in_progress()) {
2107 assert(mode()->is_generational(), "Only generational GC has old marking");
2108 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2109 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2110 mask = YOUNG_MARKING;
2111 } else {
2112 mask = MARKING | YOUNG_MARKING;
2113 }
2114 set_gc_state_at_safepoint(mask, in_progress);
2115 manage_satb_barrier(in_progress);
2116 }
2117
2118 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2119 #ifdef ASSERT
2120 // has_forwarded_objects() iff UPDATE_REFS or EVACUATION
2121 bool has_forwarded = has_forwarded_objects();
2122 bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION);
2123 bool evacuating = _gc_state.is_set(EVACUATION);
2124 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2125 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2126 #endif
2127 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2128 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2129 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2130 set_gc_state_at_safepoint(OLD_MARKING, in_progress);
2131 } else {
2132 set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress);
2133 }
2134 manage_satb_barrier(in_progress);
2135 }
2136
2137 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2138 return old_generation()->is_preparing_for_mark();
2139 }
2140
2141 void ShenandoahHeap::manage_satb_barrier(bool active) {
2142 if (is_concurrent_mark_in_progress()) {
2143 // Ignore request to deactivate barrier while concurrent mark is in progress.
2144 // Do not attempt to re-activate the barrier if it is already active.
2145 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2146 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2147 }
2148 } else {
2149 // No concurrent marking is in progress so honor request to deactivate,
2150 // but only if the barrier is already active.
2151 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2152 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2153 }
2154 }
2155 }
2156
2157 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2158 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2159 set_gc_state_at_safepoint(EVACUATION, in_progress);
2160 }
2161
2162 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2163 if (in_progress) {
2164 _concurrent_strong_root_in_progress.set();
2165 } else {
2166 _concurrent_strong_root_in_progress.unset();
2167 }
2168 }
2169
2170 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2171 set_gc_state_at_safepoint(WEAK_ROOTS, cond);
2172 }
2173
2174 GCTracer* ShenandoahHeap::tracer() {
2175 return shenandoah_policy()->tracer();
2176 }
2177
2178 size_t ShenandoahHeap::tlab_used() const {
2179 return _free_set->used_not_holding_lock();
2180 }
2181
2182 bool ShenandoahHeap::try_cancel_gc(GCCause::Cause cause) {
2183 const GCCause::Cause prev = _cancelled_gc.xchg(cause);
2184 return prev == GCCause::_no_gc || prev == GCCause::_shenandoah_concurrent_gc;
2185 }
2186
2187 void ShenandoahHeap::cancel_concurrent_mark() {
2188 if (mode()->is_generational()) {
2189 young_generation()->cancel_marking();
2190 old_generation()->cancel_marking();
2191 }
2192
2193 global_generation()->cancel_marking();
2194
2195 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2196 }
2197
2198 bool ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2199 if (try_cancel_gc(cause)) {
2200 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2201 log_info(gc,thread)("%s", msg.buffer());
2202 Events::log(Thread::current(), "%s", msg.buffer());
2203 _cancel_requested_time = os::elapsedTime();
2204 return true;
2205 }
2206 return false;
2207 }
2208
2209 uint ShenandoahHeap::max_workers() {
2210 return _max_workers;
2211 }
2212
2213 void ShenandoahHeap::stop() {
2214 // The shutdown sequence should be able to terminate when GC is running.
2215
2216 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2217 _shenandoah_policy->record_shutdown();
2218
2219 // Step 1. Stop reporting on gc thread cpu utilization
2220 mmu_tracker()->stop();
2221
2222 // Step 2. Wait until GC worker exits normally (this will cancel any ongoing GC).
2223 control_thread()->stop();
2224
2225 // Stop 4. Shutdown uncommit thread.
2226 if (_uncommit_thread != nullptr) {
2227 _uncommit_thread->stop();
2228 }
2229 }
2230
2231 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2232 if (!unload_classes()) return;
2233 ClassUnloadingContext ctx(_workers->active_workers(),
2234 true /* unregister_nmethods_during_purge */,
2235 false /* lock_nmethod_free_separately */);
2236
2237 // Unload classes and purge SystemDictionary.
2238 {
2239 ShenandoahPhaseTimings::Phase phase = full_gc ?
2240 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2241 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2242 ShenandoahIsAliveSelector is_alive;
2243 {
2244 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2245 ShenandoahGCPhase gc_phase(phase);
2246 ShenandoahGCWorkerPhase worker_phase(phase);
2247 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2248
2249 // Clean JVMCI metadata handles.
2250 JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
2251
2252 ShenandoahClassUnloadingTask unlink_task(phase, unloading_occurred);
2253 _workers->run_task(&unlink_task);
2254 }
2255 // Release unloaded nmethods's memory.
2256 ClassUnloadingContext::context()->purge_and_free_nmethods();
2257 }
2258
2259 {
2260 ShenandoahGCPhase phase(full_gc ?
2261 ShenandoahPhaseTimings::full_gc_purge_cldg :
2262 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2263 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2264 }
2265 // Resize and verify metaspace
2266 MetaspaceGC::compute_new_size();
2267 DEBUG_ONLY(MetaspaceUtils::verify();)
2268 }
2269
2270 // Weak roots are either pre-evacuated (final mark) or updated (final update refs),
2271 // so they should not have forwarded oops.
2272 // However, we do need to "null" dead oops in the roots, if can not be done
2273 // in concurrent cycles.
2274 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2275 uint num_workers = _workers->active_workers();
2276 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2277 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2278 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2279 ShenandoahGCPhase phase(timing_phase);
2280 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2281 // Cleanup weak roots
2282 if (has_forwarded_objects()) {
2283 ShenandoahForwardedIsAliveClosure is_alive;
2284 ShenandoahNonConcUpdateRefsClosure keep_alive;
2285 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2286 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2287 _workers->run_task(&cleaning_task);
2288 } else {
2289 ShenandoahIsAliveClosure is_alive;
2290 #ifdef ASSERT
2291 ShenandoahAssertNotForwardedClosure verify_cl;
2292 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2293 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2294 #else
2295 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2296 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2297 #endif
2298 _workers->run_task(&cleaning_task);
2299 }
2300 }
2301
2302 void ShenandoahHeap::parallel_cleaning(ShenandoahGeneration* generation, bool full_gc) {
2303 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2304 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2305 ShenandoahGCPhase phase(full_gc ?
2306 ShenandoahPhaseTimings::full_gc_purge :
2307 ShenandoahPhaseTimings::degen_gc_purge);
2308 stw_weak_refs(generation, full_gc);
2309 stw_process_weak_roots(full_gc);
2310 stw_unload_classes(full_gc);
2311 }
2312
2313 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2314 set_gc_state_at_safepoint(HAS_FORWARDED, cond);
2315 }
2316
2317 void ShenandoahHeap::set_unload_classes(bool uc) {
2318 _unload_classes.set_cond(uc);
2319 }
2320
2321 bool ShenandoahHeap::unload_classes() const {
2322 return _unload_classes.is_set();
2323 }
2324
2325 address ShenandoahHeap::in_cset_fast_test_addr() {
2326 ShenandoahHeap* heap = ShenandoahHeap::heap();
2327 assert(heap->collection_set() != nullptr, "Sanity");
2328 return (address) heap->collection_set()->biased_map_address();
2329 }
2330
2331 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2332 // It is important to force_alloc_rate_sample() before the associated generation's bytes_allocated has been reset.
2333 // Note that there is no lock to prevent additional alloations between sampling bytes_allocated_since_gc_start() and
2334 // reset_bytes_allocated_since_gc_start(). If additional allocations happen, they will be ignored in the average
2335 // allocation rate computations. This effect is considered to be be negligible.
2336
2337 // unaccounted_bytes is the bytes not accounted for by our forced sample. If the sample interval is too short,
2338 // the "forced sample" will not happen, and any recently allocated bytes are "unaccounted for". We pretend these
2339 // bytes are allocated after the start of subsequent gc.
2340 size_t unaccounted_bytes;
2341 ShenandoahFreeSet* _free_set = free_set();
2342 size_t bytes_allocated = _free_set->get_bytes_allocated_since_gc_start();
2343 if (mode()->is_generational()) {
2344 unaccounted_bytes = young_generation()->heuristics()->force_alloc_rate_sample(bytes_allocated);
2345 } else {
2346 // Single-gen Shenandoah uses global heuristics.
2347 unaccounted_bytes = heuristics()->force_alloc_rate_sample(bytes_allocated);
2348 }
2349 ShenandoahHeapLocker locker(lock());
2350 _free_set->reset_bytes_allocated_since_gc_start(unaccounted_bytes);
2351 }
2352
2353 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2354 _degenerated_gc_in_progress.set_cond(in_progress);
2355 }
2356
2357 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2358 _full_gc_in_progress.set_cond(in_progress);
2359 }
2360
2361 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2362 assert (is_full_gc_in_progress(), "should be");
2363 _full_gc_move_in_progress.set_cond(in_progress);
2364 }
2365
2366 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2367 set_gc_state_at_safepoint(UPDATE_REFS, in_progress);
2368 }
2369
2370 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2371 ShenandoahCodeRoots::register_nmethod(nm);
2372 }
2373
2374 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2375 ShenandoahCodeRoots::unregister_nmethod(nm);
2376 }
2377
2378 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2379 heap_region_containing(o)->record_pin();
2380 }
2381
2382 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2383 ShenandoahHeapRegion* r = heap_region_containing(o);
2384 assert(r != nullptr, "Sanity");
2385 assert(r->pin_count() > 0, "Region %zu should have non-zero pins", r->index());
2386 r->record_unpin();
2387 }
2388
2389 void ShenandoahHeap::sync_pinned_region_status() {
2390 ShenandoahHeapLocker locker(lock());
2391
2392 for (size_t i = 0; i < num_regions(); i++) {
2393 ShenandoahHeapRegion *r = get_region(i);
2394 if (r->is_active()) {
2395 if (r->is_pinned()) {
2396 if (r->pin_count() == 0) {
2397 r->make_unpinned();
2398 }
2399 } else {
2400 if (r->pin_count() > 0) {
2401 r->make_pinned();
2402 }
2403 }
2404 }
2405 }
2406
2407 assert_pinned_region_status();
2408 }
2409
2410 #ifdef ASSERT
2411 void ShenandoahHeap::assert_pinned_region_status() const {
2412 assert_pinned_region_status(global_generation());
2413 }
2414
2415 void ShenandoahHeap::assert_pinned_region_status(ShenandoahGeneration* generation) const {
2416 for (size_t i = 0; i < num_regions(); i++) {
2417 ShenandoahHeapRegion* r = get_region(i);
2418 if (generation->contains(r)) {
2419 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2420 "Region %zu pinning status is inconsistent", i);
2421 }
2422 }
2423 }
2424 #endif
2425
2426 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2427 return _gc_timer;
2428 }
2429
2430 void ShenandoahHeap::prepare_concurrent_roots() {
2431 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2432 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2433 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2434 set_concurrent_weak_root_in_progress(true);
2435 if (unload_classes()) {
2436 _unloader.prepare();
2437 }
2438 }
2439
2440 void ShenandoahHeap::finish_concurrent_roots() {
2441 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2442 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2443 if (unload_classes()) {
2444 _unloader.finish();
2445 }
2446 }
2447
2448 #ifdef ASSERT
2449 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2450 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2451
2452 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2453 // Use ParallelGCThreads inside safepoints
2454 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2455 ParallelGCThreads, nworkers);
2456 } else {
2457 // Use ConcGCThreads outside safepoints
2458 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2459 ConcGCThreads, nworkers);
2460 }
2461 }
2462 #endif
2463
2464 ShenandoahVerifier* ShenandoahHeap::verifier() {
2465 guarantee(ShenandoahVerify, "Should be enabled");
2466 assert (_verifier != nullptr, "sanity");
2467 return _verifier;
2468 }
2469
2470 template<bool CONCURRENT>
2471 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2472 private:
2473 ShenandoahHeap* _heap;
2474 ShenandoahRegionIterator* _regions;
2475 public:
2476 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2477 WorkerTask("Shenandoah Update References"),
2478 _heap(ShenandoahHeap::heap()),
2479 _regions(regions) {
2480 }
2481
2482 void work(uint worker_id) {
2483 if (CONCURRENT) {
2484 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2485 ShenandoahSuspendibleThreadSetJoiner stsj;
2486 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2487 } else {
2488 ShenandoahParallelWorkerSession worker_session(worker_id);
2489 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2490 }
2491 }
2492
2493 private:
2494 template<class T>
2495 void do_work(uint worker_id) {
2496 if (CONCURRENT && (worker_id == 0)) {
2497 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2498 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2499 size_t cset_regions = _heap->collection_set()->count();
2500
2501 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2502 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2503 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2504 // next GC cycle.
2505 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2506 }
2507 // If !CONCURRENT, there's no value in expanding Mutator free set
2508 T cl;
2509 ShenandoahHeapRegion* r = _regions->next();
2510 while (r != nullptr) {
2511 HeapWord* update_watermark = r->get_update_watermark();
2512 assert (update_watermark >= r->bottom(), "sanity");
2513 if (r->is_active() && !r->is_cset()) {
2514 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2515 }
2516 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2517 return;
2518 }
2519 r = _regions->next();
2520 }
2521 }
2522 };
2523
2524 void ShenandoahHeap::update_heap_references(ShenandoahGeneration* generation, bool concurrent) {
2525 assert(generation->is_global(), "Should only get global generation here");
2526 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2527
2528 if (concurrent) {
2529 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2530 workers()->run_task(&task);
2531 } else {
2532 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2533 workers()->run_task(&task);
2534 }
2535 }
2536
2537 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2538 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2539 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2540
2541 {
2542 ShenandoahGCPhase phase(concurrent ?
2543 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2544 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2545
2546 final_update_refs_update_region_states();
2547
2548 assert_pinned_region_status();
2549 }
2550
2551 {
2552 ShenandoahGCPhase phase(concurrent ?
2553 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2554 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2555 trash_cset_regions();
2556 }
2557 }
2558
2559 void ShenandoahHeap::final_update_refs_update_region_states() {
2560 ShenandoahSynchronizePinnedRegionStates cl;
2561 parallel_heap_region_iterate(&cl);
2562 }
2563
2564 void ShenandoahHeap::rebuild_free_set_within_phase() {
2565 ShenandoahHeapLocker locker(lock());
2566 size_t young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count;
2567 _free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old_region, last_old_region, old_region_count);
2568 // If there are no old regions, first_old_region will be greater than last_old_region
2569 assert((first_old_region > last_old_region) ||
2570 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2571 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2572 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu",
2573 old_region_count, first_old_region, last_old_region);
2574
2575 if (mode()->is_generational()) {
2576 #ifdef ASSERT
2577 if (ShenandoahVerify) {
2578 verifier()->verify_before_rebuilding_free_set();
2579 }
2580 #endif
2581
2582 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2583 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2584 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2585 size_t allocation_runway =
2586 gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_trashed_regions);
2587 gen_heap->compute_old_generation_balance(allocation_runway, old_trashed_regions, young_trashed_regions);
2588 }
2589 // Rebuild free set based on adjusted generation sizes.
2590 _free_set->finish_rebuild(young_trashed_regions, old_trashed_regions, old_region_count);
2591
2592 if (mode()->is_generational()) {
2593 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2594 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2595 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2596 }
2597 }
2598
2599 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2600 ShenandoahGCPhase phase(concurrent ?
2601 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2602 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2603 rebuild_free_set_within_phase();
2604 }
2605
2606 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2607 size_t slice = r->index() / _bitmap_regions_per_slice;
2608
2609 size_t regions_from = _bitmap_regions_per_slice * slice;
2610 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2611 for (size_t g = regions_from; g < regions_to; g++) {
2612 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2613 if (skip_self && g == r->index()) continue;
2614 if (get_region(g)->is_committed()) {
2615 return true;
2616 }
2617 }
2618 return false;
2619 }
2620
2621 void ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2622 shenandoah_assert_heaplocked();
2623 assert(!is_bitmap_region_special(), "Not for special memory");
2624
2625 if (is_bitmap_slice_committed(r, true)) {
2626 // Some other region from the group is already committed, meaning the bitmap
2627 // slice is already committed, we exit right away.
2628 return;
2629 }
2630
2631 // Commit the bitmap slice:
2632 size_t slice = r->index() / _bitmap_regions_per_slice;
2633 size_t off = _bitmap_bytes_per_slice * slice;
2634 size_t len = _bitmap_bytes_per_slice;
2635 char* start = (char*) _bitmap_region.start() + off;
2636
2637 os::commit_memory_or_exit(start, len, false, "Unable to commit bitmap slice");
2638
2639 if (AlwaysPreTouch) {
2640 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2641 }
2642 }
2643
2644 void ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2645 shenandoah_assert_heaplocked();
2646 assert(!is_bitmap_region_special(), "Not for special memory");
2647
2648 if (is_bitmap_slice_committed(r, true)) {
2649 // Some other region from the group is still committed, meaning the bitmap
2650 // slice should stay committed, exit right away.
2651 return;
2652 }
2653
2654 // Uncommit the bitmap slice:
2655 size_t slice = r->index() / _bitmap_regions_per_slice;
2656 size_t off = _bitmap_bytes_per_slice * slice;
2657 size_t len = _bitmap_bytes_per_slice;
2658
2659 char* addr = (char*) _bitmap_region.start() + off;
2660 os::uncommit_memory(addr, len);
2661 }
2662
2663 void ShenandoahHeap::forbid_uncommit() {
2664 if (_uncommit_thread != nullptr) {
2665 _uncommit_thread->forbid_uncommit();
2666 }
2667 }
2668
2669 void ShenandoahHeap::allow_uncommit() {
2670 if (_uncommit_thread != nullptr) {
2671 _uncommit_thread->allow_uncommit();
2672 }
2673 }
2674
2675 #ifdef ASSERT
2676 bool ShenandoahHeap::is_uncommit_in_progress() {
2677 if (_uncommit_thread != nullptr) {
2678 return _uncommit_thread->is_uncommit_in_progress();
2679 }
2680 return false;
2681 }
2682 #endif
2683
2684 void ShenandoahHeap::safepoint_synchronize_begin() {
2685 StackWatermarkSet::safepoint_synchronize_begin();
2686 SuspendibleThreadSet::synchronize();
2687 }
2688
2689 void ShenandoahHeap::safepoint_synchronize_end() {
2690 SuspendibleThreadSet::desynchronize();
2691 }
2692
2693 void ShenandoahHeap::try_inject_alloc_failure() {
2694 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2695 _inject_alloc_failure.set();
2696 os::naked_short_sleep(1);
2697 if (cancelled_gc()) {
2698 log_info(gc)("Allocation failure was successfully injected");
2699 }
2700 }
2701 }
2702
2703 bool ShenandoahHeap::should_inject_alloc_failure() {
2704 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2705 }
2706
2707 void ShenandoahHeap::initialize_serviceability() {
2708 _memory_pool = new ShenandoahMemoryPool(this);
2709 _cycle_memory_manager.add_pool(_memory_pool);
2710 _stw_memory_manager.add_pool(_memory_pool);
2711 }
2712
2713 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2714 GrowableArray<GCMemoryManager*> memory_managers(2);
2715 memory_managers.append(&_cycle_memory_manager);
2716 memory_managers.append(&_stw_memory_manager);
2717 return memory_managers;
2718 }
2719
2720 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2721 GrowableArray<MemoryPool*> memory_pools(1);
2722 memory_pools.append(_memory_pool);
2723 return memory_pools;
2724 }
2725
2726 MemoryUsage ShenandoahHeap::memory_usage() {
2727 return shenandoah_memory_usage(_initial_size, used(), committed(), max_capacity());
2728 }
2729
2730 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2731 _heap(ShenandoahHeap::heap()),
2732 _index(0) {}
2733
2734 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2735 _heap(heap),
2736 _index(0) {}
2737
2738 void ShenandoahRegionIterator::reset() {
2739 _index.store_relaxed(0);
2740 }
2741
2742 bool ShenandoahRegionIterator::has_next() const {
2743 return _index.load_relaxed() < _heap->num_regions();
2744 }
2745
2746 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2747 #ifdef ASSERT
2748 assert(_liveness_cache != nullptr, "sanity");
2749 assert(worker_id < _max_workers, "sanity");
2750 for (uint i = 0; i < num_regions(); i++) {
2751 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2752 }
2753 #endif
2754 return _liveness_cache[worker_id];
2755 }
2756
2757 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2758 assert(worker_id < _max_workers, "sanity");
2759 assert(_liveness_cache != nullptr, "sanity");
2760 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2761 for (uint i = 0; i < num_regions(); i++) {
2762 ShenandoahLiveData live = ld[i];
2763 if (live > 0) {
2764 ShenandoahHeapRegion* r = get_region(i);
2765 r->increase_live_data_gc_words(live);
2766 ld[i] = 0;
2767 }
2768 }
2769 }
2770
2771 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2772 if (is_idle()) return false;
2773
2774 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2775 // marking phase.
2776 if (is_concurrent_mark_in_progress() &&
2777 !marking_context()->allocated_after_mark_start(obj)) {
2778 return true;
2779 }
2780
2781 // Can not guarantee obj is deeply good.
2782 if (has_forwarded_objects()) {
2783 return true;
2784 }
2785
2786 return false;
2787 }
2788
2789 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2790 #if INCLUDE_CDS_JAVA_HEAP
2791 // CDS wants a raw continuous memory range to load a bunch of objects itself.
2792 // This is an unusual request, since all requested regions should be regular, not humongous.
2793 //
2794 // CDS would guarantee no objects straddle multiple regions, as long as regions are as large
2795 // as MIN_GC_REGION_ALIGNMENT.
2796 guarantee(ShenandoahHeapRegion::region_size_bytes() >= AOTMappedHeapWriter::MIN_GC_REGION_ALIGNMENT, "Must be");
2797
2798 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_cds(size);
2799 return allocate_memory(req);
2800 #else
2801 assert(false, "Archive heap loader should not be available, should not be here");
2802 return nullptr;
2803 #endif // INCLUDE_CDS_JAVA_HEAP
2804 }
2805
2806 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2807 // Nothing to do here, except checking that heap looks fine.
2808 #ifdef ASSERT
2809 HeapWord* start = archive_space.start();
2810 HeapWord* end = archive_space.end();
2811
2812 // No unclaimed space between the objects.
2813 // Objects are properly allocated in correct regions.
2814 HeapWord* cur = start;
2815 while (cur < end) {
2816 oop oop = cast_to_oop(cur);
2817 shenandoah_assert_in_correct_region(nullptr, oop);
2818 cur += oop->size();
2819 }
2820
2821 // No unclaimed tail at the end of archive space.
2822 assert(cur == end,
2823 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2824 p2i(cur), p2i(end));
2825
2826 // All regions in contiguous space have good state.
2827 size_t begin_reg_idx = heap_region_index_containing(start);
2828 size_t end_reg_idx = heap_region_index_containing(end);
2829
2830 for (size_t idx = begin_reg_idx; idx <= end_reg_idx; idx++) {
2831 ShenandoahHeapRegion* r = get_region(idx);
2832 assert(r->is_regular(), "Must be regular");
2833 assert(r->is_young(), "Must be young");
2834 assert(idx == end_reg_idx || r->top() == r->end(),
2835 "All regions except the last one should be full: " PTR_FORMAT " " PTR_FORMAT,
2836 p2i(r->top()), p2i(r->end()));
2837 assert(idx != begin_reg_idx || r->bottom() == start,
2838 "Archive space start should be at the bottom of first region: " PTR_FORMAT " " PTR_FORMAT,
2839 p2i(r->bottom()), p2i(start));
2840 assert(idx != end_reg_idx || r->top() == end,
2841 "Archive space end should be at the top of last region: " PTR_FORMAT " " PTR_FORMAT,
2842 p2i(r->top()), p2i(end));
2843 }
2844
2845 #endif
2846 }
2847
2848 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2849 if (!mode()->is_generational()) {
2850 return global_generation();
2851 } else if (affiliation == YOUNG_GENERATION) {
2852 return young_generation();
2853 } else if (affiliation == OLD_GENERATION) {
2854 return old_generation();
2855 }
2856
2857 ShouldNotReachHere();
2858 return nullptr;
2859 }
2860
2861 void ShenandoahHeap::log_heap_status(const char* msg) const {
2862 if (mode()->is_generational()) {
2863 young_generation()->log_status(msg);
2864 old_generation()->log_status(msg);
2865 } else {
2866 global_generation()->log_status(msg);
2867 }
2868 }
2869
2870 ShenandoahHeapLocker::ShenandoahHeapLocker(ShenandoahHeapLock* lock, bool allow_block_for_safepoint) : _lock(lock) {
2871 #ifdef ASSERT
2872 ShenandoahFreeSet* free_set = ShenandoahHeap::heap()->free_set();
2873 // free_set is nullptr only at pre-initialized state
2874 assert(free_set == nullptr || !free_set->rebuild_lock()->owned_by_self(), "Dead lock, can't acquire heap lock while holding free-set rebuild lock");
2875 assert(_lock != nullptr, "Must not");
2876 #endif
2877 _lock->lock(allow_block_for_safepoint);
2878 }