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