1 /*
2 * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/universe.hpp"
29
30 #include "gc/shared/gcArguments.hpp"
31 #include "gc/shared/gcTimer.hpp"
32 #include "gc/shared/gcTraceTime.inline.hpp"
33 #include "gc/shared/locationPrinter.inline.hpp"
34 #include "gc/shared/memAllocator.hpp"
35 #include "gc/shared/plab.hpp"
36 #include "gc/shared/slidingForwarding.hpp"
37 #include "gc/shared/tlab_globals.hpp"
38
39 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
40 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
41 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
42 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
43 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
44 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
45 #include "gc/shenandoah/shenandoahControlThread.hpp"
46 #include "gc/shenandoah/shenandoahFreeSet.hpp"
47 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
48 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
49 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
50 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
51 #include "gc/shenandoah/shenandoahInitLogger.hpp"
52 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
53 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
54 #include "gc/shenandoah/shenandoahMetrics.hpp"
55 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
56 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
57 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
58 #include "gc/shenandoah/shenandoahPadding.hpp"
59 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
60 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
61 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
62 #include "gc/shenandoah/shenandoahStringDedup.hpp"
63 #include "gc/shenandoah/shenandoahSTWMark.hpp"
64 #include "gc/shenandoah/shenandoahUtils.hpp"
65 #include "gc/shenandoah/shenandoahVerifier.hpp"
66 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
67 #include "gc/shenandoah/shenandoahVMOperations.hpp"
68 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
69 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
70 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
71 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
72 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
73 #if INCLUDE_JFR
74 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
75 #endif
76
77 #include "classfile/systemDictionary.hpp"
78 #include "code/codeCache.hpp"
79 #include "memory/classLoaderMetaspace.hpp"
80 #include "memory/metaspaceUtils.hpp"
81 #include "oops/compressedOops.inline.hpp"
82 #include "prims/jvmtiTagMap.hpp"
83 #include "runtime/atomic.hpp"
84 #include "runtime/globals.hpp"
85 #include "runtime/interfaceSupport.inline.hpp"
86 #include "runtime/java.hpp"
87 #include "runtime/orderAccess.hpp"
88 #include "runtime/safepointMechanism.hpp"
89 #include "runtime/vmThread.hpp"
90 #include "services/mallocTracker.hpp"
91 #include "services/memTracker.hpp"
92 #include "utilities/events.hpp"
93 #include "utilities/powerOfTwo.hpp"
94
95 class ShenandoahPretouchHeapTask : public WorkerTask {
96 private:
97 ShenandoahRegionIterator _regions;
98 const size_t _page_size;
99 public:
100 ShenandoahPretouchHeapTask(size_t page_size) :
101 WorkerTask("Shenandoah Pretouch Heap"),
102 _page_size(page_size) {}
103
104 virtual void work(uint worker_id) {
105 ShenandoahHeapRegion* r = _regions.next();
106 while (r != nullptr) {
107 if (r->is_committed()) {
108 os::pretouch_memory(r->bottom(), r->end(), _page_size);
109 }
110 r = _regions.next();
111 }
112 }
113 };
114
115 class ShenandoahPretouchBitmapTask : public WorkerTask {
116 private:
117 ShenandoahRegionIterator _regions;
118 char* _bitmap_base;
119 const size_t _bitmap_size;
120 const size_t _page_size;
121 public:
122 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
123 WorkerTask("Shenandoah Pretouch Bitmap"),
124 _bitmap_base(bitmap_base),
125 _bitmap_size(bitmap_size),
126 _page_size(page_size) {}
127
128 virtual void work(uint worker_id) {
129 ShenandoahHeapRegion* r = _regions.next();
130 while (r != nullptr) {
131 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
132 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
133 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
134
135 if (r->is_committed()) {
136 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
137 }
138
139 r = _regions.next();
140 }
141 }
142 };
143
144 jint ShenandoahHeap::initialize() {
145 //
146 // Figure out heap sizing
147 //
148
149 size_t init_byte_size = InitialHeapSize;
150 size_t min_byte_size = MinHeapSize;
151 size_t max_byte_size = MaxHeapSize;
152 size_t heap_alignment = HeapAlignment;
153
154 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
155
156 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
157 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
158
159 _num_regions = ShenandoahHeapRegion::region_count();
160 assert(_num_regions == (max_byte_size / reg_size_bytes),
161 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
162 _num_regions, max_byte_size, reg_size_bytes);
163
164 // Now we know the number of regions, initialize the heuristics.
165 initialize_heuristics();
166
167 size_t num_committed_regions = init_byte_size / reg_size_bytes;
168 num_committed_regions = MIN2(num_committed_regions, _num_regions);
169 assert(num_committed_regions <= _num_regions, "sanity");
170 _initial_size = num_committed_regions * reg_size_bytes;
171
172 size_t num_min_regions = min_byte_size / reg_size_bytes;
173 num_min_regions = MIN2(num_min_regions, _num_regions);
174 assert(num_min_regions <= _num_regions, "sanity");
175 _minimum_size = num_min_regions * reg_size_bytes;
176
177 // Default to max heap size.
178 _soft_max_size = _num_regions * reg_size_bytes;
179
180 _committed = _initial_size;
181
182 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
183 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
184 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
185
186 //
187 // Reserve and commit memory for heap
188 //
189
190 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
191 initialize_reserved_region(heap_rs);
192 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
193 _heap_region_special = heap_rs.special();
194
195 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
196 "Misaligned heap: " PTR_FORMAT, p2i(base()));
197
198 _forwarding = new SlidingForwarding(_heap_region, ShenandoahHeapRegion::region_size_words_shift());
199
200 #if SHENANDOAH_OPTIMIZED_MARKTASK
201 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
202 // Fail if we ever attempt to address more than we can.
203 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
204 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
205 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
206 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
207 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
208 vm_exit_during_initialization("Fatal Error", buf);
209 }
210 #endif
211
212 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
213 if (!_heap_region_special) {
214 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
215 "Cannot commit heap memory");
216 }
217
218 //
219 // Reserve and commit memory for bitmap(s)
220 //
221
222 _bitmap_size = ShenandoahMarkBitMap::compute_size(heap_rs.size());
223 _bitmap_size = align_up(_bitmap_size, bitmap_page_size);
224
225 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
226
227 guarantee(bitmap_bytes_per_region != 0,
228 "Bitmap bytes per region should not be zero");
229 guarantee(is_power_of_2(bitmap_bytes_per_region),
230 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
231
232 if (bitmap_page_size > bitmap_bytes_per_region) {
233 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
234 _bitmap_bytes_per_slice = bitmap_page_size;
235 } else {
236 _bitmap_regions_per_slice = 1;
237 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
238 }
239
240 guarantee(_bitmap_regions_per_slice >= 1,
241 "Should have at least one region per slice: " SIZE_FORMAT,
242 _bitmap_regions_per_slice);
243
244 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
245 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
246 _bitmap_bytes_per_slice, bitmap_page_size);
247
248 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
249 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
250 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
251 _bitmap_region_special = bitmap.special();
252
253 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
254 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
255 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
256 if (!_bitmap_region_special) {
257 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
258 "Cannot commit bitmap memory");
259 }
260
261 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions, _max_workers);
262
263 if (ShenandoahVerify) {
264 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
265 if (!verify_bitmap.special()) {
266 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
267 "Cannot commit verification bitmap memory");
268 }
269 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
270 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
271 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
272 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
273 }
274
275 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
276 ReservedSpace aux_bitmap(_bitmap_size, bitmap_page_size);
277 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
278 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
279 _aux_bitmap_region_special = aux_bitmap.special();
280 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
281
282 //
283 // Create regions and region sets
284 //
285 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
286 size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
287 region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());
288
289 ReservedSpace region_storage(region_storage_size, region_page_size);
290 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
291 if (!region_storage.special()) {
292 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
293 "Cannot commit region memory");
294 }
295
296 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
297 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
298 // If not successful, bite a bullet and allocate at whatever address.
299 {
300 size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
301 size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
302
303 uintptr_t min = round_up_power_of_2(cset_align);
304 uintptr_t max = (1u << 30u);
305
306 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
307 char* req_addr = (char*)addr;
308 assert(is_aligned(req_addr, cset_align), "Should be aligned");
309 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size(), req_addr);
310 if (cset_rs.is_reserved()) {
311 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
312 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
313 break;
314 }
315 }
316
317 if (_collection_set == nullptr) {
318 ReservedSpace cset_rs(cset_size, cset_align, os::vm_page_size());
319 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
320 }
321 }
322
323 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
324 _free_set = new ShenandoahFreeSet(this, _num_regions);
325
326 {
327 ShenandoahHeapLocker locker(lock());
328
329 for (size_t i = 0; i < _num_regions; i++) {
330 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
331 bool is_committed = i < num_committed_regions;
332 void* loc = region_storage.base() + i * region_align;
333
334 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
335 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
336
337 _marking_context->initialize_top_at_mark_start(r);
338 _regions[i] = r;
339 assert(!collection_set()->is_in(i), "New region should not be in collection set");
340 }
341
342 // Initialize to complete
343 _marking_context->mark_complete();
344
345 _free_set->rebuild();
346 }
347
348 if (AlwaysPreTouch) {
349 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
350 // before initialize() below zeroes it with initializing thread. For any given region,
351 // we touch the region and the corresponding bitmaps from the same thread.
352 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
353
354 _pretouch_heap_page_size = heap_page_size;
355 _pretouch_bitmap_page_size = bitmap_page_size;
356
357 #ifdef LINUX
358 // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
359 // pages. But, the kernel needs to know that every small page is used, in order to coalesce
360 // them into huge one. Therefore, we need to pretouch with smaller pages.
361 if (UseTransparentHugePages) {
362 _pretouch_heap_page_size = (size_t)os::vm_page_size();
363 _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
364 }
365 #endif
366
367 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
368 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
369
370 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
371 _workers->run_task(&bcl);
372
373 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
374 _workers->run_task(&hcl);
375 }
376
377 //
378 // Initialize the rest of GC subsystems
379 //
380
381 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
382 for (uint worker = 0; worker < _max_workers; worker++) {
383 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
384 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
385 }
386
387 // There should probably be Shenandoah-specific options for these,
388 // just as there are G1-specific options.
389 {
390 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
391 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
392 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
393 }
394
395 _monitoring_support = new ShenandoahMonitoringSupport(this);
396 _phase_timings = new ShenandoahPhaseTimings(max_workers());
397 ShenandoahCodeRoots::initialize();
398
399 if (ShenandoahPacing) {
400 _pacer = new ShenandoahPacer(this);
401 _pacer->setup_for_idle();
402 } else {
403 _pacer = nullptr;
404 }
405
406 _control_thread = new ShenandoahControlThread();
407
408 ShenandoahInitLogger::print();
409
410 return JNI_OK;
411 }
412
413 void ShenandoahHeap::initialize_mode() {
414 if (ShenandoahGCMode != nullptr) {
415 if (strcmp(ShenandoahGCMode, "satb") == 0) {
416 _gc_mode = new ShenandoahSATBMode();
417 } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
418 _gc_mode = new ShenandoahIUMode();
419 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
420 _gc_mode = new ShenandoahPassiveMode();
421 } else {
422 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
423 }
424 } else {
425 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
426 }
427 _gc_mode->initialize_flags();
428 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
429 vm_exit_during_initialization(
430 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
431 _gc_mode->name()));
432 }
433 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
434 vm_exit_during_initialization(
435 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
436 _gc_mode->name()));
437 }
438 }
439
440 void ShenandoahHeap::initialize_heuristics() {
441 assert(_gc_mode != nullptr, "Must be initialized");
442 _heuristics = _gc_mode->initialize_heuristics();
443
444 if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
445 vm_exit_during_initialization(
446 err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
447 _heuristics->name()));
448 }
449 if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
450 vm_exit_during_initialization(
451 err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
452 _heuristics->name()));
453 }
454 }
455
456 #ifdef _MSC_VER
457 #pragma warning( push )
458 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
459 #endif
460
461 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
462 CollectedHeap(),
463 _initial_size(0),
464 _used(0),
465 _committed(0),
466 _bytes_allocated_since_gc_start(0),
467 _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
468 _workers(nullptr),
469 _safepoint_workers(nullptr),
470 _heap_region_special(false),
471 _num_regions(0),
472 _regions(nullptr),
473 _update_refs_iterator(this),
474 _control_thread(nullptr),
475 _shenandoah_policy(policy),
476 _gc_mode(nullptr),
477 _heuristics(nullptr),
478 _free_set(nullptr),
479 _pacer(nullptr),
480 _verifier(nullptr),
481 _phase_timings(nullptr),
482 _monitoring_support(nullptr),
483 _memory_pool(nullptr),
484 _stw_memory_manager("Shenandoah Pauses", "end of GC pause"),
485 _cycle_memory_manager("Shenandoah Cycles", "end of GC cycle"),
486 _gc_timer(new ConcurrentGCTimer()),
487 _soft_ref_policy(),
488 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
489 _ref_processor(new ShenandoahReferenceProcessor(MAX2(_max_workers, 1U))),
490 _marking_context(nullptr),
491 _bitmap_size(0),
492 _bitmap_regions_per_slice(0),
493 _bitmap_bytes_per_slice(0),
494 _bitmap_region_special(false),
495 _aux_bitmap_region_special(false),
496 _liveness_cache(nullptr),
497 _collection_set(nullptr)
498 {
499 // Initialize GC mode early, so we can adjust barrier support
500 initialize_mode();
501 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
502
503 _max_workers = MAX2(_max_workers, 1U);
504 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
505 if (_workers == nullptr) {
506 vm_exit_during_initialization("Failed necessary allocation.");
507 } else {
508 _workers->initialize_workers();
509 }
510
511 if (ParallelGCThreads > 1) {
512 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread",
513 ParallelGCThreads);
514 _safepoint_workers->initialize_workers();
515 }
516 }
517
518 #ifdef _MSC_VER
519 #pragma warning( pop )
520 #endif
521
522 class ShenandoahResetBitmapTask : public WorkerTask {
523 private:
524 ShenandoahRegionIterator _regions;
525
526 public:
527 ShenandoahResetBitmapTask() :
528 WorkerTask("Shenandoah Reset Bitmap") {}
529
530 void work(uint worker_id) {
531 ShenandoahHeapRegion* region = _regions.next();
532 ShenandoahHeap* heap = ShenandoahHeap::heap();
533 ShenandoahMarkingContext* const ctx = heap->marking_context();
534 while (region != nullptr) {
535 if (heap->is_bitmap_slice_committed(region)) {
536 ctx->clear_bitmap(region);
537 }
538 region = _regions.next();
539 }
540 }
541 };
542
543 void ShenandoahHeap::reset_mark_bitmap() {
544 assert_gc_workers(_workers->active_workers());
545 mark_incomplete_marking_context();
546
547 ShenandoahResetBitmapTask task;
548 _workers->run_task(&task);
549 }
550
551 void ShenandoahHeap::print_on(outputStream* st) const {
552 st->print_cr("Shenandoah Heap");
553 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
554 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
555 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
556 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
557 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
558 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
559 num_regions(),
560 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
561 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
562
563 st->print("Status: ");
564 if (has_forwarded_objects()) st->print("has forwarded objects, ");
565 if (is_concurrent_mark_in_progress()) st->print("marking, ");
566 if (is_evacuation_in_progress()) st->print("evacuating, ");
567 if (is_update_refs_in_progress()) st->print("updating refs, ");
568 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
569 if (is_full_gc_in_progress()) st->print("full gc, ");
570 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
571 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
572 if (is_concurrent_strong_root_in_progress() &&
573 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
574
575 if (cancelled_gc()) {
576 st->print("cancelled");
577 } else {
578 st->print("not cancelled");
579 }
580 st->cr();
581
582 st->print_cr("Reserved region:");
583 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
584 p2i(reserved_region().start()),
585 p2i(reserved_region().end()));
586
587 ShenandoahCollectionSet* cset = collection_set();
588 st->print_cr("Collection set:");
589 if (cset != nullptr) {
590 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
591 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
592 } else {
593 st->print_cr(" (null)");
594 }
595
596 st->cr();
597 MetaspaceUtils::print_on(st);
598
599 if (Verbose) {
600 print_heap_regions_on(st);
601 }
602 }
603
604 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
605 public:
606 void do_thread(Thread* thread) {
607 assert(thread != nullptr, "Sanity");
608 assert(thread->is_Worker_thread(), "Only worker thread expected");
609 ShenandoahThreadLocalData::initialize_gclab(thread);
610 }
611 };
612
613 void ShenandoahHeap::post_initialize() {
614 CollectedHeap::post_initialize();
615 MutexLocker ml(Threads_lock);
616
617 ShenandoahInitWorkerGCLABClosure init_gclabs;
618 _workers->threads_do(&init_gclabs);
619
620 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
621 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
622 _workers->set_initialize_gclab();
623 if (_safepoint_workers != nullptr) {
624 _safepoint_workers->threads_do(&init_gclabs);
625 _safepoint_workers->set_initialize_gclab();
626 }
627
628 _heuristics->initialize();
629
630 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers());
631 }
632
633 size_t ShenandoahHeap::used() const {
634 return Atomic::load(&_used);
635 }
636
637 size_t ShenandoahHeap::committed() const {
638 return Atomic::load(&_committed);
639 }
640
641 void ShenandoahHeap::increase_committed(size_t bytes) {
642 shenandoah_assert_heaplocked_or_safepoint();
643 _committed += bytes;
644 }
645
646 void ShenandoahHeap::decrease_committed(size_t bytes) {
647 shenandoah_assert_heaplocked_or_safepoint();
648 _committed -= bytes;
649 }
650
651 void ShenandoahHeap::increase_used(size_t bytes) {
652 Atomic::add(&_used, bytes, memory_order_relaxed);
653 }
654
655 void ShenandoahHeap::set_used(size_t bytes) {
656 Atomic::store(&_used, bytes);
657 }
658
659 void ShenandoahHeap::decrease_used(size_t bytes) {
660 assert(used() >= bytes, "never decrease heap size by more than we've left");
661 Atomic::sub(&_used, bytes, memory_order_relaxed);
662 }
663
664 void ShenandoahHeap::increase_allocated(size_t bytes) {
665 Atomic::add(&_bytes_allocated_since_gc_start, bytes, memory_order_relaxed);
666 }
667
668 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
669 size_t bytes = words * HeapWordSize;
670 if (!waste) {
671 increase_used(bytes);
672 }
673 increase_allocated(bytes);
674 if (ShenandoahPacing) {
675 control_thread()->pacing_notify_alloc(words);
676 if (waste) {
677 pacer()->claim_for_alloc(words, true);
678 }
679 }
680 }
681
682 size_t ShenandoahHeap::capacity() const {
683 return committed();
684 }
685
686 size_t ShenandoahHeap::max_capacity() const {
687 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
688 }
689
690 size_t ShenandoahHeap::soft_max_capacity() const {
691 size_t v = Atomic::load(&_soft_max_size);
692 assert(min_capacity() <= v && v <= max_capacity(),
693 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
694 min_capacity(), v, max_capacity());
695 return v;
696 }
697
698 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
699 assert(min_capacity() <= v && v <= max_capacity(),
700 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
701 min_capacity(), v, max_capacity());
702 Atomic::store(&_soft_max_size, v);
703 }
704
705 size_t ShenandoahHeap::min_capacity() const {
706 return _minimum_size;
707 }
708
709 size_t ShenandoahHeap::initial_capacity() const {
710 return _initial_size;
711 }
712
713 bool ShenandoahHeap::is_in(const void* p) const {
714 HeapWord* heap_base = (HeapWord*) base();
715 HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
716 return p >= heap_base && p < last_region_end;
717 }
718
719 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
720 assert (ShenandoahUncommit, "should be enabled");
721
722 // Application allocates from the beginning of the heap, and GC allocates at
723 // the end of it. It is more efficient to uncommit from the end, so that applications
724 // could enjoy the near committed regions. GC allocations are much less frequent,
725 // and therefore can accept the committing costs.
726
727 size_t count = 0;
728 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
729 ShenandoahHeapRegion* r = get_region(i - 1);
730 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
731 ShenandoahHeapLocker locker(lock());
732 if (r->is_empty_committed()) {
733 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
734 break;
735 }
736
737 r->make_uncommitted();
738 count++;
739 }
740 }
741 SpinPause(); // allow allocators to take the lock
742 }
743
744 if (count > 0) {
745 control_thread()->notify_heap_changed();
746 }
747 }
748
749 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
750 // New object should fit the GCLAB size
751 size_t min_size = MAX2(size, PLAB::min_size());
752
753 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
754 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
755 new_size = MIN2(new_size, PLAB::max_size());
756 new_size = MAX2(new_size, PLAB::min_size());
757
758 // Record new heuristic value even if we take any shortcut. This captures
759 // the case when moderately-sized objects always take a shortcut. At some point,
760 // heuristics should catch up with them.
761 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
762
763 if (new_size < size) {
764 // New size still does not fit the object. Fall back to shared allocation.
765 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
766 return nullptr;
767 }
768
769 // Retire current GCLAB, and allocate a new one.
770 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
771 gclab->retire();
772
773 size_t actual_size = 0;
774 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
775 if (gclab_buf == nullptr) {
776 return nullptr;
777 }
778
779 assert (size <= actual_size, "allocation should fit");
780
781 if (ZeroTLAB) {
782 // ..and clear it.
783 Copy::zero_to_words(gclab_buf, actual_size);
784 } else {
785 // ...and zap just allocated object.
786 #ifdef ASSERT
787 // Skip mangling the space corresponding to the object header to
788 // ensure that the returned space is not considered parsable by
789 // any concurrent GC thread.
790 size_t hdr_size = oopDesc::header_size();
791 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
792 #endif // ASSERT
793 }
794 gclab->set_buf(gclab_buf, actual_size);
795 return gclab->allocate(size);
796 }
797
798 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
799 size_t requested_size,
800 size_t* actual_size) {
801 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
802 HeapWord* res = allocate_memory(req);
803 if (res != nullptr) {
804 *actual_size = req.actual_size();
805 } else {
806 *actual_size = 0;
807 }
808 return res;
809 }
810
811 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
812 size_t word_size,
813 size_t* actual_size) {
814 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
815 HeapWord* res = allocate_memory(req);
816 if (res != nullptr) {
817 *actual_size = req.actual_size();
818 } else {
819 *actual_size = 0;
820 }
821 return res;
822 }
823
824 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
825 intptr_t pacer_epoch = 0;
826 bool in_new_region = false;
827 HeapWord* result = nullptr;
828
829 if (req.is_mutator_alloc()) {
830 if (ShenandoahPacing) {
831 pacer()->pace_for_alloc(req.size());
832 pacer_epoch = pacer()->epoch();
833 }
834
835 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
836 result = allocate_memory_under_lock(req, in_new_region);
837 }
838
839 // Allocation failed, block until control thread reacted, then retry allocation.
840 //
841 // It might happen that one of the threads requesting allocation would unblock
842 // way later after GC happened, only to fail the second allocation, because
843 // other threads have already depleted the free storage. In this case, a better
844 // strategy is to try again, as long as GC makes progress.
845 //
846 // Then, we need to make sure the allocation was retried after at least one
847 // Full GC, which means we want to try more than ShenandoahFullGCThreshold times.
848
849 size_t tries = 0;
850
851 while (result == nullptr && _progress_last_gc.is_set()) {
852 tries++;
853 control_thread()->handle_alloc_failure(req);
854 result = allocate_memory_under_lock(req, in_new_region);
855 }
856
857 while (result == nullptr && tries <= ShenandoahFullGCThreshold) {
858 tries++;
859 control_thread()->handle_alloc_failure(req);
860 result = allocate_memory_under_lock(req, in_new_region);
861 }
862
863 } else {
864 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
865 result = allocate_memory_under_lock(req, in_new_region);
866 // Do not call handle_alloc_failure() here, because we cannot block.
867 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
868 }
869
870 if (in_new_region) {
871 control_thread()->notify_heap_changed();
872 }
873
874 if (result != nullptr) {
875 size_t requested = req.size();
876 size_t actual = req.actual_size();
877
878 assert (req.is_lab_alloc() || (requested == actual),
879 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
880 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
881
882 if (req.is_mutator_alloc()) {
883 notify_mutator_alloc_words(actual, false);
884
885 // If we requested more than we were granted, give the rest back to pacer.
886 // This only matters if we are in the same pacing epoch: do not try to unpace
887 // over the budget for the other phase.
888 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
889 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
890 }
891 } else {
892 increase_used(actual*HeapWordSize);
893 }
894 }
895
896 return result;
897 }
898
899 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
900 ShenandoahHeapLocker locker(lock());
901 return _free_set->allocate(req, in_new_region);
902 }
903
904 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
905 bool* gc_overhead_limit_was_exceeded) {
906 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
907 return allocate_memory(req);
908 }
909
910 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
911 size_t size,
912 Metaspace::MetadataType mdtype) {
913 MetaWord* result;
914
915 // Inform metaspace OOM to GC heuristics if class unloading is possible.
916 if (heuristics()->can_unload_classes()) {
917 ShenandoahHeuristics* h = heuristics();
918 h->record_metaspace_oom();
919 }
920
921 // Expand and retry allocation
922 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
923 if (result != nullptr) {
924 return result;
925 }
926
927 // Start full GC
928 collect(GCCause::_metadata_GC_clear_soft_refs);
929
930 // Retry allocation
931 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
932 if (result != nullptr) {
933 return result;
934 }
935
936 // Expand and retry allocation
937 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
938 if (result != nullptr) {
939 return result;
940 }
941
942 // Out of memory
943 return nullptr;
944 }
945
946 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
947 private:
948 ShenandoahHeap* const _heap;
949 Thread* const _thread;
950 public:
951 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
952 _heap(heap), _thread(Thread::current()) {}
953
954 void do_object(oop p) {
955 shenandoah_assert_marked(nullptr, p);
956 if (!ShenandoahForwarding::is_forwarded(p)) {
957 _heap->evacuate_object(p, _thread);
958 }
959 }
960 };
961
962 class ShenandoahEvacuationTask : public WorkerTask {
963 private:
964 ShenandoahHeap* const _sh;
965 ShenandoahCollectionSet* const _cs;
966 bool _concurrent;
967 public:
968 ShenandoahEvacuationTask(ShenandoahHeap* sh,
969 ShenandoahCollectionSet* cs,
970 bool concurrent) :
971 WorkerTask("Shenandoah Evacuation"),
972 _sh(sh),
973 _cs(cs),
974 _concurrent(concurrent)
975 {}
976
977 void work(uint worker_id) {
978 if (_concurrent) {
979 ShenandoahConcurrentWorkerSession worker_session(worker_id);
980 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
981 ShenandoahEvacOOMScope oom_evac_scope;
982 do_work();
983 } else {
984 ShenandoahParallelWorkerSession worker_session(worker_id);
985 ShenandoahEvacOOMScope oom_evac_scope;
986 do_work();
987 }
988 }
989
990 private:
991 void do_work() {
992 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
993 ShenandoahHeapRegion* r;
994 while ((r =_cs->claim_next()) != nullptr) {
995 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
996 _sh->marked_object_iterate(r, &cl);
997
998 if (ShenandoahPacing) {
999 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1000 }
1001
1002 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1003 break;
1004 }
1005 }
1006 }
1007 };
1008
1009 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1010 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1011 workers()->run_task(&task);
1012 }
1013
1014 void ShenandoahHeap::trash_cset_regions() {
1015 ShenandoahHeapLocker locker(lock());
1016
1017 ShenandoahCollectionSet* set = collection_set();
1018 ShenandoahHeapRegion* r;
1019 set->clear_current_index();
1020 while ((r = set->next()) != nullptr) {
1021 r->make_trash();
1022 }
1023 collection_set()->clear();
1024 }
1025
1026 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1027 st->print_cr("Heap Regions:");
1028 st->print_cr("EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HC=humongous continuation, CS=collection set, T=trash, P=pinned");
1029 st->print_cr("BTE=bottom/top/end, U=used, T=TLAB allocs, G=GCLAB allocs, S=shared allocs, L=live data");
1030 st->print_cr("R=root, CP=critical pins, TAMS=top-at-mark-start, UWM=update watermark");
1031 st->print_cr("SN=alloc sequence number");
1032
1033 for (size_t i = 0; i < num_regions(); i++) {
1034 get_region(i)->print_on(st);
1035 }
1036 }
1037
1038 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1039 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1040
1041 oop humongous_obj = cast_to_oop(start->bottom());
1042 size_t size = humongous_obj->size();
1043 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1044 size_t index = start->index() + required_regions - 1;
1045
1046 assert(!start->has_live(), "liveness must be zero");
1047
1048 for(size_t i = 0; i < required_regions; i++) {
1049 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1050 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1051 ShenandoahHeapRegion* region = get_region(index --);
1052
1053 assert(region->is_humongous(), "expect correct humongous start or continuation");
1054 assert(!region->is_cset(), "Humongous region should not be in collection set");
1055
1056 region->make_trash_immediate();
1057 }
1058 }
1059
1060 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1061 public:
1062 ShenandoahCheckCleanGCLABClosure() {}
1063 void do_thread(Thread* thread) {
1064 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1065 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1066 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1067 }
1068 };
1069
1070 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1071 private:
1072 bool const _resize;
1073 public:
1074 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1075 void do_thread(Thread* thread) {
1076 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1077 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1078 gclab->retire();
1079 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1080 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1081 }
1082 }
1083 };
1084
1085 void ShenandoahHeap::labs_make_parsable() {
1086 assert(UseTLAB, "Only call with UseTLAB");
1087
1088 ShenandoahRetireGCLABClosure cl(false);
1089
1090 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1091 ThreadLocalAllocBuffer& tlab = t->tlab();
1092 tlab.make_parsable();
1093 cl.do_thread(t);
1094 }
1095
1096 workers()->threads_do(&cl);
1097 }
1098
1099 void ShenandoahHeap::tlabs_retire(bool resize) {
1100 assert(UseTLAB, "Only call with UseTLAB");
1101 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1102
1103 ThreadLocalAllocStats stats;
1104
1105 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1106 ThreadLocalAllocBuffer& tlab = t->tlab();
1107 tlab.retire(&stats);
1108 if (resize) {
1109 tlab.resize();
1110 }
1111 }
1112
1113 stats.publish();
1114
1115 #ifdef ASSERT
1116 ShenandoahCheckCleanGCLABClosure cl;
1117 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1118 cl.do_thread(t);
1119 }
1120 workers()->threads_do(&cl);
1121 #endif
1122 }
1123
1124 void ShenandoahHeap::gclabs_retire(bool resize) {
1125 assert(UseTLAB, "Only call with UseTLAB");
1126 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1127
1128 ShenandoahRetireGCLABClosure cl(resize);
1129 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1130 cl.do_thread(t);
1131 }
1132 workers()->threads_do(&cl);
1133
1134 if (safepoint_workers() != nullptr) {
1135 safepoint_workers()->threads_do(&cl);
1136 }
1137 }
1138
1139 // Returns size in bytes
1140 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1141 if (ShenandoahElasticTLAB) {
1142 // With Elastic TLABs, return the max allowed size, and let the allocation path
1143 // figure out the safe size for current allocation.
1144 return ShenandoahHeapRegion::max_tlab_size_bytes();
1145 } else {
1146 return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes());
1147 }
1148 }
1149
1150 size_t ShenandoahHeap::max_tlab_size() const {
1151 // Returns size in words
1152 return ShenandoahHeapRegion::max_tlab_size_words();
1153 }
1154
1155 void ShenandoahHeap::collect(GCCause::Cause cause) {
1156 control_thread()->request_gc(cause);
1157 }
1158
1159 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1160 //assert(false, "Shouldn't need to do full collections");
1161 }
1162
1163 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1164 ShenandoahHeapRegion* r = heap_region_containing(addr);
1165 if (r != nullptr) {
1166 return r->block_start(addr);
1167 }
1168 return nullptr;
1169 }
1170
1171 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1172 ShenandoahHeapRegion* r = heap_region_containing(addr);
1173 return r->block_is_obj(addr);
1174 }
1175
1176 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1177 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1178 }
1179
1180 void ShenandoahHeap::prepare_for_verify() {
1181 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1182 labs_make_parsable();
1183 }
1184 }
1185
1186 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1187 tcl->do_thread(_control_thread);
1188 workers()->threads_do(tcl);
1189 if (_safepoint_workers != nullptr) {
1190 _safepoint_workers->threads_do(tcl);
1191 }
1192 if (ShenandoahStringDedup::is_enabled()) {
1193 ShenandoahStringDedup::threads_do(tcl);
1194 }
1195 }
1196
1197 void ShenandoahHeap::print_tracing_info() const {
1198 LogTarget(Info, gc, stats) lt;
1199 if (lt.is_enabled()) {
1200 ResourceMark rm;
1201 LogStream ls(lt);
1202
1203 phase_timings()->print_global_on(&ls);
1204
1205 ls.cr();
1206 ls.cr();
1207
1208 shenandoah_policy()->print_gc_stats(&ls);
1209
1210 ls.cr();
1211 ls.cr();
1212 }
1213 }
1214
1215 void ShenandoahHeap::verify(VerifyOption vo) {
1216 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1217 if (ShenandoahVerify) {
1218 verifier()->verify_generic(vo);
1219 } else {
1220 // TODO: Consider allocating verification bitmaps on demand,
1221 // and turn this on unconditionally.
1222 }
1223 }
1224 }
1225 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1226 return _free_set->capacity();
1227 }
1228
1229 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1230 private:
1231 MarkBitMap* _bitmap;
1232 ShenandoahScanObjectStack* _oop_stack;
1233 ShenandoahHeap* const _heap;
1234 ShenandoahMarkingContext* const _marking_context;
1235
1236 template <class T>
1237 void do_oop_work(T* p) {
1238 T o = RawAccess<>::oop_load(p);
1239 if (!CompressedOops::is_null(o)) {
1240 oop obj = CompressedOops::decode_not_null(o);
1241 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1242 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1243 return;
1244 }
1245 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1246
1247 assert(oopDesc::is_oop(obj), "must be a valid oop");
1248 if (!_bitmap->is_marked(obj)) {
1249 _bitmap->mark(obj);
1250 _oop_stack->push(obj);
1251 }
1252 }
1253 }
1254 public:
1255 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1256 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1257 _marking_context(_heap->marking_context()) {}
1258 void do_oop(oop* p) { do_oop_work(p); }
1259 void do_oop(narrowOop* p) { do_oop_work(p); }
1260 };
1261
1262 /*
1263 * This is public API, used in preparation of object_iterate().
1264 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1265 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1266 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1267 */
1268 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1269 // No-op.
1270 }
1271
1272 /*
1273 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1274 *
1275 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1276 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1277 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1278 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1279 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1280 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1281 * wiped the bitmap in preparation for next marking).
1282 *
1283 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1284 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1285 * is allowed to report dead objects, but is not required to do so.
1286 */
1287 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1288 // Reset bitmap
1289 if (!prepare_aux_bitmap_for_iteration())
1290 return;
1291
1292 ShenandoahScanObjectStack oop_stack;
1293 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1294 // Seed the stack with root scan
1295 scan_roots_for_iteration(&oop_stack, &oops);
1296
1297 // Work through the oop stack to traverse heap
1298 while (! oop_stack.is_empty()) {
1299 oop obj = oop_stack.pop();
1300 assert(oopDesc::is_oop(obj), "must be a valid oop");
1301 shenandoah_assert_not_in_cset_except(NULL, obj, cancelled_gc());
1302 cl->do_object(obj);
1303 obj->oop_iterate(&oops);
1304 }
1305
1306 assert(oop_stack.is_empty(), "should be empty");
1307 // Reclaim bitmap
1308 reclaim_aux_bitmap_for_iteration();
1309 }
1310
1311 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1312 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1313
1314 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1315 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1316 return false;
1317 }
1318 // Reset bitmap
1319 _aux_bit_map.clear();
1320 return true;
1321 }
1322
1323 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1324 // Process GC roots according to current GC cycle
1325 // This populates the work stack with initial objects
1326 // It is important to relinquish the associated locks before diving
1327 // into heap dumper
1328 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1329 ShenandoahHeapIterationRootScanner rp(n_workers);
1330 rp.roots_do(oops);
1331 }
1332
1333 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1334 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1335 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1336 }
1337 }
1338
1339 // Closure for parallelly iterate objects
1340 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1341 private:
1342 MarkBitMap* _bitmap;
1343 ShenandoahObjToScanQueue* _queue;
1344 ShenandoahHeap* const _heap;
1345 ShenandoahMarkingContext* const _marking_context;
1346
1347 template <class T>
1348 void do_oop_work(T* p) {
1349 T o = RawAccess<>::oop_load(p);
1350 if (!CompressedOops::is_null(o)) {
1351 oop obj = CompressedOops::decode_not_null(o);
1352 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1353 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1354 return;
1355 }
1356 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1357
1358 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1359 if (_bitmap->par_mark(obj)) {
1360 _queue->push(ShenandoahMarkTask(obj));
1361 }
1362 }
1363 }
1364 public:
1365 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1366 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1367 _marking_context(_heap->marking_context()) {}
1368 void do_oop(oop* p) { do_oop_work(p); }
1369 void do_oop(narrowOop* p) { do_oop_work(p); }
1370 };
1371
1372 // Object iterator for parallel heap iteraion.
1373 // The root scanning phase happenes in construction as a preparation of
1374 // parallel marking queues.
1375 // Every worker processes it's own marking queue. work-stealing is used
1376 // to balance workload.
1377 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1378 private:
1379 uint _num_workers;
1380 bool _init_ready;
1381 MarkBitMap* _aux_bit_map;
1382 ShenandoahHeap* _heap;
1383 ShenandoahScanObjectStack _roots_stack; // global roots stack
1384 ShenandoahObjToScanQueueSet* _task_queues;
1385 public:
1386 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1387 _num_workers(num_workers),
1388 _init_ready(false),
1389 _aux_bit_map(bitmap),
1390 _heap(ShenandoahHeap::heap()) {
1391 // Initialize bitmap
1392 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1393 if (!_init_ready) {
1394 return;
1395 }
1396
1397 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1398 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1399
1400 _init_ready = prepare_worker_queues();
1401 }
1402
1403 ~ShenandoahParallelObjectIterator() {
1404 // Reclaim bitmap
1405 _heap->reclaim_aux_bitmap_for_iteration();
1406 // Reclaim queue for workers
1407 if (_task_queues!= nullptr) {
1408 for (uint i = 0; i < _num_workers; ++i) {
1409 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1410 if (q != nullptr) {
1411 delete q;
1412 _task_queues->register_queue(i, nullptr);
1413 }
1414 }
1415 delete _task_queues;
1416 _task_queues = nullptr;
1417 }
1418 }
1419
1420 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1421 if (_init_ready) {
1422 object_iterate_parallel(cl, worker_id, _task_queues);
1423 }
1424 }
1425
1426 private:
1427 // Divide global root_stack into worker queues
1428 bool prepare_worker_queues() {
1429 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1430 // Initialize queues for every workers
1431 for (uint i = 0; i < _num_workers; ++i) {
1432 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1433 _task_queues->register_queue(i, task_queue);
1434 }
1435 // Divide roots among the workers. Assume that object referencing distribution
1436 // is related with root kind, use round-robin to make every worker have same chance
1437 // to process every kind of roots
1438 size_t roots_num = _roots_stack.size();
1439 if (roots_num == 0) {
1440 // No work to do
1441 return false;
1442 }
1443
1444 for (uint j = 0; j < roots_num; j++) {
1445 uint stack_id = j % _num_workers;
1446 oop obj = _roots_stack.pop();
1447 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1448 }
1449 return true;
1450 }
1451
1452 void object_iterate_parallel(ObjectClosure* cl,
1453 uint worker_id,
1454 ShenandoahObjToScanQueueSet* queue_set) {
1455 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1456 assert(queue_set != nullptr, "task queue must not be null");
1457
1458 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1459 assert(q != nullptr, "object iterate queue must not be null");
1460
1461 ShenandoahMarkTask t;
1462 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1463
1464 // Work through the queue to traverse heap.
1465 // Steal when there is no task in queue.
1466 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1467 oop obj = t.obj();
1468 assert(oopDesc::is_oop(obj), "must be a valid oop");
1469 cl->do_object(obj);
1470 obj->oop_iterate(&oops);
1471 }
1472 assert(q->is_empty(), "should be empty");
1473 }
1474 };
1475
1476 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1477 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1478 }
1479
1480 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1481 void ShenandoahHeap::keep_alive(oop obj) {
1482 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1483 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1484 }
1485 }
1486
1487 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1488 for (size_t i = 0; i < num_regions(); i++) {
1489 ShenandoahHeapRegion* current = get_region(i);
1490 blk->heap_region_do(current);
1491 }
1492 }
1493
1494 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1495 private:
1496 ShenandoahHeap* const _heap;
1497 ShenandoahHeapRegionClosure* const _blk;
1498
1499 shenandoah_padding(0);
1500 volatile size_t _index;
1501 shenandoah_padding(1);
1502
1503 public:
1504 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1505 WorkerTask("Shenandoah Parallel Region Operation"),
1506 _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1507
1508 void work(uint worker_id) {
1509 ShenandoahParallelWorkerSession worker_session(worker_id);
1510 size_t stride = ShenandoahParallelRegionStride;
1511
1512 size_t max = _heap->num_regions();
1513 while (Atomic::load(&_index) < max) {
1514 size_t cur = Atomic::fetch_and_add(&_index, stride, memory_order_relaxed);
1515 size_t start = cur;
1516 size_t end = MIN2(cur + stride, max);
1517 if (start >= max) break;
1518
1519 for (size_t i = cur; i < end; i++) {
1520 ShenandoahHeapRegion* current = _heap->get_region(i);
1521 _blk->heap_region_do(current);
1522 }
1523 }
1524 }
1525 };
1526
1527 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1528 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1529 if (num_regions() > ShenandoahParallelRegionStride) {
1530 ShenandoahParallelHeapRegionTask task(blk);
1531 workers()->run_task(&task);
1532 } else {
1533 heap_region_iterate(blk);
1534 }
1535 }
1536
1537 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1538 private:
1539 ShenandoahMarkingContext* const _ctx;
1540 public:
1541 ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1542
1543 void heap_region_do(ShenandoahHeapRegion* r) {
1544 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1545 if (r->is_active()) {
1546 // Check if region needs updating its TAMS. We have updated it already during concurrent
1547 // reset, so it is very likely we don't need to do another write here.
1548 if (_ctx->top_at_mark_start(r) != r->top()) {
1549 _ctx->capture_top_at_mark_start(r);
1550 }
1551 } else {
1552 assert(_ctx->top_at_mark_start(r) == r->top(),
1553 "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
1554 }
1555 }
1556
1557 bool is_thread_safe() { return true; }
1558 };
1559
1560 class ShenandoahRendezvousClosure : public HandshakeClosure {
1561 public:
1562 inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
1563 inline void do_thread(Thread* thread) {}
1564 };
1565
1566 void ShenandoahHeap::rendezvous_threads() {
1567 ShenandoahRendezvousClosure cl;
1568 Handshake::execute(&cl);
1569 }
1570
1571 void ShenandoahHeap::recycle_trash() {
1572 free_set()->recycle_trash();
1573 }
1574
1575 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1576 private:
1577 ShenandoahMarkingContext* const _ctx;
1578 public:
1579 ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1580
1581 void heap_region_do(ShenandoahHeapRegion* r) {
1582 if (r->is_active()) {
1583 // Reset live data and set TAMS optimistically. We would recheck these under the pause
1584 // anyway to capture any updates that happened since now.
1585 r->clear_live_data();
1586 _ctx->capture_top_at_mark_start(r);
1587 }
1588 }
1589
1590 bool is_thread_safe() { return true; }
1591 };
1592
1593 void ShenandoahHeap::prepare_gc() {
1594 reset_mark_bitmap();
1595
1596 ShenandoahResetUpdateRegionStateClosure cl;
1597 parallel_heap_region_iterate(&cl);
1598 }
1599
1600 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1601 private:
1602 ShenandoahMarkingContext* const _ctx;
1603 ShenandoahHeapLock* const _lock;
1604
1605 public:
1606 ShenandoahFinalMarkUpdateRegionStateClosure() :
1607 _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1608
1609 void heap_region_do(ShenandoahHeapRegion* r) {
1610 if (r->is_active()) {
1611 // All allocations past TAMS are implicitly live, adjust the region data.
1612 // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1613 HeapWord *tams = _ctx->top_at_mark_start(r);
1614 HeapWord *top = r->top();
1615 if (top > tams) {
1616 r->increase_live_data_alloc_words(pointer_delta(top, tams));
1617 }
1618
1619 // We are about to select the collection set, make sure it knows about
1620 // current pinning status. Also, this allows trashing more regions that
1621 // now have their pinning status dropped.
1622 if (r->is_pinned()) {
1623 if (r->pin_count() == 0) {
1624 ShenandoahHeapLocker locker(_lock);
1625 r->make_unpinned();
1626 }
1627 } else {
1628 if (r->pin_count() > 0) {
1629 ShenandoahHeapLocker locker(_lock);
1630 r->make_pinned();
1631 }
1632 }
1633
1634 // Remember limit for updating refs. It's guaranteed that we get no
1635 // from-space-refs written from here on.
1636 r->set_update_watermark_at_safepoint(r->top());
1637 } else {
1638 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1639 assert(_ctx->top_at_mark_start(r) == r->top(),
1640 "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1641 }
1642 }
1643
1644 bool is_thread_safe() { return true; }
1645 };
1646
1647 void ShenandoahHeap::prepare_regions_and_collection_set(bool concurrent) {
1648 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
1649 {
1650 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states :
1651 ShenandoahPhaseTimings::degen_gc_final_update_region_states);
1652 ShenandoahFinalMarkUpdateRegionStateClosure cl;
1653 parallel_heap_region_iterate(&cl);
1654
1655 assert_pinned_region_status();
1656 }
1657
1658 {
1659 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset :
1660 ShenandoahPhaseTimings::degen_gc_choose_cset);
1661 ShenandoahHeapLocker locker(lock());
1662 _collection_set->clear();
1663 heuristics()->choose_collection_set(_collection_set);
1664 }
1665
1666 {
1667 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset :
1668 ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
1669 ShenandoahHeapLocker locker(lock());
1670 _free_set->rebuild();
1671 }
1672 }
1673
1674 void ShenandoahHeap::do_class_unloading() {
1675 _unloader.unload();
1676 }
1677
1678 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1679 // Weak refs processing
1680 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1681 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1682 ShenandoahTimingsTracker t(phase);
1683 ShenandoahGCWorkerPhase worker_phase(phase);
1684 ref_processor()->process_references(phase, workers(), false /* concurrent */);
1685 }
1686
1687 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1688 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1689
1690 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1691 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1692 // for future GCLABs here.
1693 if (UseTLAB) {
1694 ShenandoahGCPhase phase(concurrent ?
1695 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1696 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1697 gclabs_retire(ResizeTLAB);
1698 }
1699
1700 _update_refs_iterator.reset();
1701 }
1702
1703 void ShenandoahHeap::set_gc_state_all_threads(char state) {
1704 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1705 ShenandoahThreadLocalData::set_gc_state(t, state);
1706 }
1707 }
1708
1709 void ShenandoahHeap::set_gc_state_mask(uint mask, bool value) {
1710 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should really be Shenandoah safepoint");
1711 _gc_state.set_cond(mask, value);
1712 set_gc_state_all_threads(_gc_state.raw_value());
1713 }
1714
1715 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1716 assert(!has_forwarded_objects(), "Not expected before/after mark phase");
1717 set_gc_state_mask(MARKING, in_progress);
1718 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1719 }
1720
1721 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1722 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1723 set_gc_state_mask(EVACUATION, in_progress);
1724 }
1725
1726 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
1727 if (in_progress) {
1728 _concurrent_strong_root_in_progress.set();
1729 } else {
1730 _concurrent_strong_root_in_progress.unset();
1731 }
1732 }
1733
1734 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
1735 set_gc_state_mask(WEAK_ROOTS, cond);
1736 }
1737
1738 GCTracer* ShenandoahHeap::tracer() {
1739 return shenandoah_policy()->tracer();
1740 }
1741
1742 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1743 return _free_set->used();
1744 }
1745
1746 bool ShenandoahHeap::try_cancel_gc() {
1747 while (true) {
1748 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1749 if (prev == CANCELLABLE) return true;
1750 else if (prev == CANCELLED) return false;
1751 assert(ShenandoahSuspendibleWorkers, "should not get here when not using suspendible workers");
1752 assert(prev == NOT_CANCELLED, "must be NOT_CANCELLED");
1753 Thread* thread = Thread::current();
1754 if (thread->is_Java_thread()) {
1755 // We need to provide a safepoint here, otherwise we might
1756 // spin forever if a SP is pending.
1757 ThreadBlockInVM sp(JavaThread::cast(thread));
1758 SpinPause();
1759 }
1760 }
1761 }
1762
1763 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1764 if (try_cancel_gc()) {
1765 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1766 log_info(gc)("%s", msg.buffer());
1767 Events::log(Thread::current(), "%s", msg.buffer());
1768 }
1769 }
1770
1771 uint ShenandoahHeap::max_workers() {
1772 return _max_workers;
1773 }
1774
1775 void ShenandoahHeap::stop() {
1776 // The shutdown sequence should be able to terminate when GC is running.
1777
1778 // Step 0. Notify policy to disable event recording.
1779 _shenandoah_policy->record_shutdown();
1780
1781 // Step 1. Notify control thread that we are in shutdown.
1782 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1783 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1784 control_thread()->prepare_for_graceful_shutdown();
1785
1786 // Step 2. Notify GC workers that we are cancelling GC.
1787 cancel_gc(GCCause::_shenandoah_stop_vm);
1788
1789 // Step 3. Wait until GC worker exits normally.
1790 control_thread()->stop();
1791 }
1792
1793 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1794 if (!unload_classes()) return;
1795 // Unload classes and purge SystemDictionary.
1796 {
1797 ShenandoahPhaseTimings::Phase phase = full_gc ?
1798 ShenandoahPhaseTimings::full_gc_purge_class_unload :
1799 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
1800 ShenandoahIsAliveSelector is_alive;
1801 CodeCache::UnloadingScope scope(is_alive.is_alive_closure());
1802 ShenandoahGCPhase gc_phase(phase);
1803 ShenandoahGCWorkerPhase worker_phase(phase);
1804 bool purged_class = SystemDictionary::do_unloading(gc_timer());
1805
1806 uint num_workers = _workers->active_workers();
1807 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, purged_class);
1808 _workers->run_task(&unlink_task);
1809 }
1810
1811 {
1812 ShenandoahGCPhase phase(full_gc ?
1813 ShenandoahPhaseTimings::full_gc_purge_cldg :
1814 ShenandoahPhaseTimings::degen_gc_purge_cldg);
1815 ClassLoaderDataGraph::purge(/*at_safepoint*/true);
1816 }
1817 // Resize and verify metaspace
1818 MetaspaceGC::compute_new_size();
1819 DEBUG_ONLY(MetaspaceUtils::verify();)
1820 }
1821
1822 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
1823 // so they should not have forwarded oops.
1824 // However, we do need to "null" dead oops in the roots, if can not be done
1825 // in concurrent cycles.
1826 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
1827 uint num_workers = _workers->active_workers();
1828 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
1829 ShenandoahPhaseTimings::full_gc_purge_weak_par :
1830 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
1831 ShenandoahGCPhase phase(timing_phase);
1832 ShenandoahGCWorkerPhase worker_phase(timing_phase);
1833 // Cleanup weak roots
1834 if (has_forwarded_objects()) {
1835 ShenandoahForwardedIsAliveClosure is_alive;
1836 ShenandoahUpdateRefsClosure keep_alive;
1837 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
1838 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
1839 _workers->run_task(&cleaning_task);
1840 } else {
1841 ShenandoahIsAliveClosure is_alive;
1842 #ifdef ASSERT
1843 ShenandoahAssertNotForwardedClosure verify_cl;
1844 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
1845 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
1846 #else
1847 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
1848 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
1849 #endif
1850 _workers->run_task(&cleaning_task);
1851 }
1852 }
1853
1854 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
1855 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1856 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
1857 ShenandoahGCPhase phase(full_gc ?
1858 ShenandoahPhaseTimings::full_gc_purge :
1859 ShenandoahPhaseTimings::degen_gc_purge);
1860 stw_weak_refs(full_gc);
1861 stw_process_weak_roots(full_gc);
1862 stw_unload_classes(full_gc);
1863 }
1864
1865 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
1866 set_gc_state_mask(HAS_FORWARDED, cond);
1867 }
1868
1869 void ShenandoahHeap::set_unload_classes(bool uc) {
1870 _unload_classes.set_cond(uc);
1871 }
1872
1873 bool ShenandoahHeap::unload_classes() const {
1874 return _unload_classes.is_set();
1875 }
1876
1877 address ShenandoahHeap::in_cset_fast_test_addr() {
1878 ShenandoahHeap* heap = ShenandoahHeap::heap();
1879 assert(heap->collection_set() != nullptr, "Sanity");
1880 return (address) heap->collection_set()->biased_map_address();
1881 }
1882
1883 address ShenandoahHeap::cancelled_gc_addr() {
1884 return (address) ShenandoahHeap::heap()->_cancelled_gc.addr_of();
1885 }
1886
1887 address ShenandoahHeap::gc_state_addr() {
1888 return (address) ShenandoahHeap::heap()->_gc_state.addr_of();
1889 }
1890
1891 size_t ShenandoahHeap::bytes_allocated_since_gc_start() {
1892 return Atomic::load(&_bytes_allocated_since_gc_start);
1893 }
1894
1895 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
1896 Atomic::store(&_bytes_allocated_since_gc_start, (size_t)0);
1897 }
1898
1899 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
1900 _degenerated_gc_in_progress.set_cond(in_progress);
1901 }
1902
1903 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
1904 _full_gc_in_progress.set_cond(in_progress);
1905 }
1906
1907 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
1908 assert (is_full_gc_in_progress(), "should be");
1909 _full_gc_move_in_progress.set_cond(in_progress);
1910 }
1911
1912 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
1913 set_gc_state_mask(UPDATEREFS, in_progress);
1914 }
1915
1916 void ShenandoahHeap::register_nmethod(nmethod* nm) {
1917 ShenandoahCodeRoots::register_nmethod(nm);
1918 }
1919
1920 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
1921 ShenandoahCodeRoots::unregister_nmethod(nm);
1922 }
1923
1924 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
1925 heap_region_containing(o)->record_pin();
1926 }
1927
1928 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
1929 ShenandoahHeapRegion* r = heap_region_containing(o);
1930 assert(r != nullptr, "Sanity");
1931 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
1932 r->record_unpin();
1933 }
1934
1935 void ShenandoahHeap::sync_pinned_region_status() {
1936 ShenandoahHeapLocker locker(lock());
1937
1938 for (size_t i = 0; i < num_regions(); i++) {
1939 ShenandoahHeapRegion *r = get_region(i);
1940 if (r->is_active()) {
1941 if (r->is_pinned()) {
1942 if (r->pin_count() == 0) {
1943 r->make_unpinned();
1944 }
1945 } else {
1946 if (r->pin_count() > 0) {
1947 r->make_pinned();
1948 }
1949 }
1950 }
1951 }
1952
1953 assert_pinned_region_status();
1954 }
1955
1956 #ifdef ASSERT
1957 void ShenandoahHeap::assert_pinned_region_status() {
1958 for (size_t i = 0; i < num_regions(); i++) {
1959 ShenandoahHeapRegion* r = get_region(i);
1960 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
1961 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
1962 }
1963 }
1964 #endif
1965
1966 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
1967 return _gc_timer;
1968 }
1969
1970 void ShenandoahHeap::prepare_concurrent_roots() {
1971 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1972 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1973 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
1974 set_concurrent_weak_root_in_progress(true);
1975 if (unload_classes()) {
1976 _unloader.prepare();
1977 }
1978 }
1979
1980 void ShenandoahHeap::finish_concurrent_roots() {
1981 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
1982 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
1983 if (unload_classes()) {
1984 _unloader.finish();
1985 }
1986 }
1987
1988 #ifdef ASSERT
1989 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
1990 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
1991
1992 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1993 if (UseDynamicNumberOfGCThreads) {
1994 assert(nworkers <= ParallelGCThreads, "Cannot use more than it has");
1995 } else {
1996 // Use ParallelGCThreads inside safepoints
1997 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads within safepoints");
1998 }
1999 } else {
2000 if (UseDynamicNumberOfGCThreads) {
2001 assert(nworkers <= ConcGCThreads, "Cannot use more than it has");
2002 } else {
2003 // Use ConcGCThreads outside safepoints
2004 assert(nworkers == ConcGCThreads, "Use ConcGCThreads outside safepoints");
2005 }
2006 }
2007 }
2008 #endif
2009
2010 ShenandoahVerifier* ShenandoahHeap::verifier() {
2011 guarantee(ShenandoahVerify, "Should be enabled");
2012 assert (_verifier != nullptr, "sanity");
2013 return _verifier;
2014 }
2015
2016 template<bool CONCURRENT>
2017 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2018 private:
2019 ShenandoahHeap* _heap;
2020 ShenandoahRegionIterator* _regions;
2021 public:
2022 ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2023 WorkerTask("Shenandoah Update References"),
2024 _heap(ShenandoahHeap::heap()),
2025 _regions(regions) {
2026 }
2027
2028 void work(uint worker_id) {
2029 if (CONCURRENT) {
2030 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2031 ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
2032 do_work<ShenandoahConcUpdateRefsClosure>();
2033 } else {
2034 ShenandoahParallelWorkerSession worker_session(worker_id);
2035 do_work<ShenandoahSTWUpdateRefsClosure>();
2036 }
2037 }
2038
2039 private:
2040 template<class T>
2041 void do_work() {
2042 T cl;
2043 ShenandoahHeapRegion* r = _regions->next();
2044 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2045 while (r != nullptr) {
2046 HeapWord* update_watermark = r->get_update_watermark();
2047 assert (update_watermark >= r->bottom(), "sanity");
2048 if (r->is_active() && !r->is_cset()) {
2049 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2050 }
2051 if (ShenandoahPacing) {
2052 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2053 }
2054 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2055 return;
2056 }
2057 r = _regions->next();
2058 }
2059 }
2060 };
2061
2062 void ShenandoahHeap::update_heap_references(bool concurrent) {
2063 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2064
2065 if (concurrent) {
2066 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2067 workers()->run_task(&task);
2068 } else {
2069 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2070 workers()->run_task(&task);
2071 }
2072 }
2073
2074
2075 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2076 private:
2077 ShenandoahHeapLock* const _lock;
2078
2079 public:
2080 ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2081
2082 void heap_region_do(ShenandoahHeapRegion* r) {
2083 // Drop unnecessary "pinned" state from regions that does not have CP marks
2084 // anymore, as this would allow trashing them.
2085
2086 if (r->is_active()) {
2087 if (r->is_pinned()) {
2088 if (r->pin_count() == 0) {
2089 ShenandoahHeapLocker locker(_lock);
2090 r->make_unpinned();
2091 }
2092 } else {
2093 if (r->pin_count() > 0) {
2094 ShenandoahHeapLocker locker(_lock);
2095 r->make_pinned();
2096 }
2097 }
2098 }
2099 }
2100
2101 bool is_thread_safe() { return true; }
2102 };
2103
2104 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2105 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2106 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2107
2108 {
2109 ShenandoahGCPhase phase(concurrent ?
2110 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2111 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2112 ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2113 parallel_heap_region_iterate(&cl);
2114
2115 assert_pinned_region_status();
2116 }
2117
2118 {
2119 ShenandoahGCPhase phase(concurrent ?
2120 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2121 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2122 trash_cset_regions();
2123 }
2124 }
2125
2126 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2127 {
2128 ShenandoahGCPhase phase(concurrent ?
2129 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2130 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2131 ShenandoahHeapLocker locker(lock());
2132 _free_set->rebuild();
2133 }
2134 }
2135
2136 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2137 print_on(st);
2138 print_heap_regions_on(st);
2139 }
2140
2141 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2142 size_t slice = r->index() / _bitmap_regions_per_slice;
2143
2144 size_t regions_from = _bitmap_regions_per_slice * slice;
2145 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2146 for (size_t g = regions_from; g < regions_to; g++) {
2147 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2148 if (skip_self && g == r->index()) continue;
2149 if (get_region(g)->is_committed()) {
2150 return true;
2151 }
2152 }
2153 return false;
2154 }
2155
2156 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2157 shenandoah_assert_heaplocked();
2158
2159 // Bitmaps in special regions do not need commits
2160 if (_bitmap_region_special) {
2161 return true;
2162 }
2163
2164 if (is_bitmap_slice_committed(r, true)) {
2165 // Some other region from the group is already committed, meaning the bitmap
2166 // slice is already committed, we exit right away.
2167 return true;
2168 }
2169
2170 // Commit the bitmap slice:
2171 size_t slice = r->index() / _bitmap_regions_per_slice;
2172 size_t off = _bitmap_bytes_per_slice * slice;
2173 size_t len = _bitmap_bytes_per_slice;
2174 char* start = (char*) _bitmap_region.start() + off;
2175
2176 if (!os::commit_memory(start, len, false)) {
2177 return false;
2178 }
2179
2180 if (AlwaysPreTouch) {
2181 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2182 }
2183
2184 return true;
2185 }
2186
2187 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2188 shenandoah_assert_heaplocked();
2189
2190 // Bitmaps in special regions do not need uncommits
2191 if (_bitmap_region_special) {
2192 return true;
2193 }
2194
2195 if (is_bitmap_slice_committed(r, true)) {
2196 // Some other region from the group is still committed, meaning the bitmap
2197 // slice is should stay committed, exit right away.
2198 return true;
2199 }
2200
2201 // Uncommit the bitmap slice:
2202 size_t slice = r->index() / _bitmap_regions_per_slice;
2203 size_t off = _bitmap_bytes_per_slice * slice;
2204 size_t len = _bitmap_bytes_per_slice;
2205 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2206 return false;
2207 }
2208 return true;
2209 }
2210
2211 void ShenandoahHeap::safepoint_synchronize_begin() {
2212 if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2213 SuspendibleThreadSet::synchronize();
2214 }
2215 }
2216
2217 void ShenandoahHeap::safepoint_synchronize_end() {
2218 if (ShenandoahSuspendibleWorkers || UseStringDeduplication) {
2219 SuspendibleThreadSet::desynchronize();
2220 }
2221 }
2222
2223 void ShenandoahHeap::entry_uncommit(double shrink_before, size_t shrink_until) {
2224 static const char *msg = "Concurrent uncommit";
2225 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
2226 EventMark em("%s", msg);
2227
2228 op_uncommit(shrink_before, shrink_until);
2229 }
2230
2231 void ShenandoahHeap::try_inject_alloc_failure() {
2232 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2233 _inject_alloc_failure.set();
2234 os::naked_short_sleep(1);
2235 if (cancelled_gc()) {
2236 log_info(gc)("Allocation failure was successfully injected");
2237 }
2238 }
2239 }
2240
2241 bool ShenandoahHeap::should_inject_alloc_failure() {
2242 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2243 }
2244
2245 void ShenandoahHeap::initialize_serviceability() {
2246 _memory_pool = new ShenandoahMemoryPool(this);
2247 _cycle_memory_manager.add_pool(_memory_pool);
2248 _stw_memory_manager.add_pool(_memory_pool);
2249 }
2250
2251 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2252 GrowableArray<GCMemoryManager*> memory_managers(2);
2253 memory_managers.append(&_cycle_memory_manager);
2254 memory_managers.append(&_stw_memory_manager);
2255 return memory_managers;
2256 }
2257
2258 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2259 GrowableArray<MemoryPool*> memory_pools(1);
2260 memory_pools.append(_memory_pool);
2261 return memory_pools;
2262 }
2263
2264 MemoryUsage ShenandoahHeap::memory_usage() {
2265 return _memory_pool->get_memory_usage();
2266 }
2267
2268 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2269 _heap(ShenandoahHeap::heap()),
2270 _index(0) {}
2271
2272 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2273 _heap(heap),
2274 _index(0) {}
2275
2276 void ShenandoahRegionIterator::reset() {
2277 _index = 0;
2278 }
2279
2280 bool ShenandoahRegionIterator::has_next() const {
2281 return _index < _heap->num_regions();
2282 }
2283
2284 char ShenandoahHeap::gc_state() const {
2285 return _gc_state.raw_value();
2286 }
2287
2288 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2289 #ifdef ASSERT
2290 assert(_liveness_cache != nullptr, "sanity");
2291 assert(worker_id < _max_workers, "sanity");
2292 for (uint i = 0; i < num_regions(); i++) {
2293 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2294 }
2295 #endif
2296 return _liveness_cache[worker_id];
2297 }
2298
2299 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2300 assert(worker_id < _max_workers, "sanity");
2301 assert(_liveness_cache != nullptr, "sanity");
2302 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2303 for (uint i = 0; i < num_regions(); i++) {
2304 ShenandoahLiveData live = ld[i];
2305 if (live > 0) {
2306 ShenandoahHeapRegion* r = get_region(i);
2307 r->increase_live_data_gc_words(live);
2308 ld[i] = 0;
2309 }
2310 }
2311 }
2312
2313 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2314 if (is_idle()) return false;
2315
2316 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2317 // marking phase.
2318 if (is_concurrent_mark_in_progress() &&
2319 !marking_context()->allocated_after_mark_start(obj)) {
2320 return true;
2321 }
2322
2323 // Can not guarantee obj is deeply good.
2324 if (has_forwarded_objects()) {
2325 return true;
2326 }
2327
2328 return false;
2329 }