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/archiveHeapWriter.hpp"
29 #include "classfile/systemDictionary.hpp"
30
31 #include "gc/shared/classUnloadingContext.hpp"
32 #include "gc/shared/fullGCForwarding.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
41 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
42 #include "gc/shenandoah/heuristics/shenandoahYoungHeuristics.hpp"
43 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
44 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
45 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
46 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
47 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
48 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
49 #include "gc/shenandoah/shenandoahControlThread.hpp"
50 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
51 #include "gc/shenandoah/shenandoahFreeSet.hpp"
52 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp"
53 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
54 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
55 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
56 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
57 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
58 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
59 #include "gc/shenandoah/shenandoahInitLogger.hpp"
60 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
61 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
62 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
63 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
64 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
65 #include "gc/shenandoah/shenandoahPadding.hpp"
66 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
67 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
68 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
69 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
70 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
71 #include "gc/shenandoah/shenandoahSTWMark.hpp"
72 #include "gc/shenandoah/shenandoahUncommitThread.hpp"
73 #include "gc/shenandoah/shenandoahUtils.hpp"
74 #include "gc/shenandoah/shenandoahVerifier.hpp"
75 #include "gc/shenandoah/shenandoahVMOperations.hpp"
76 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
77 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
78 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
79 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
80 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
81 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
82
83 #if INCLUDE_JFR
84 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
85 #endif
86
87 #include "memory/allocation.hpp"
88 #include "memory/allocation.hpp"
89 #include "memory/classLoaderMetaspace.hpp"
90 #include "memory/memoryReserver.hpp"
91 #include "memory/metaspaceUtils.hpp"
92 #include "memory/universe.hpp"
93 #include "nmt/mallocTracker.hpp"
94 #include "nmt/memTracker.hpp"
95 #include "oops/compressedOops.inline.hpp"
96 #include "prims/jvmtiTagMap.hpp"
97 #include "runtime/atomic.hpp"
98 #include "runtime/globals.hpp"
99 #include "runtime/interfaceSupport.inline.hpp"
100 #include "runtime/java.hpp"
101 #include "runtime/orderAccess.hpp"
102 #include "runtime/safepointMechanism.hpp"
103 #include "runtime/stackWatermarkSet.hpp"
104 #include "runtime/threads.hpp"
105 #include "runtime/vmThread.hpp"
106 #include "utilities/globalDefinitions.hpp"
107 #include "utilities/events.hpp"
108 #include "utilities/powerOfTwo.hpp"
109
110 class ShenandoahPretouchHeapTask : public WorkerTask {
111 private:
112 ShenandoahRegionIterator _regions;
113 const size_t _page_size;
114 public:
115 ShenandoahPretouchHeapTask(size_t page_size) :
116 WorkerTask("Shenandoah Pretouch Heap"),
117 _page_size(page_size) {}
118
119 virtual void work(uint worker_id) {
120 ShenandoahHeapRegion* r = _regions.next();
121 while (r != nullptr) {
122 if (r->is_committed()) {
123 os::pretouch_memory(r->bottom(), r->end(), _page_size);
124 }
125 r = _regions.next();
126 }
127 }
128 };
129
130 class ShenandoahPretouchBitmapTask : public WorkerTask {
131 private:
132 ShenandoahRegionIterator _regions;
133 char* _bitmap_base;
134 const size_t _bitmap_size;
135 const size_t _page_size;
136 public:
137 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
138 WorkerTask("Shenandoah Pretouch Bitmap"),
139 _bitmap_base(bitmap_base),
140 _bitmap_size(bitmap_size),
141 _page_size(page_size) {}
142
143 virtual void work(uint worker_id) {
144 ShenandoahHeapRegion* r = _regions.next();
145 while (r != nullptr) {
146 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
147 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
148 assert (end <= _bitmap_size, "end is sane: %zu < %zu", end, _bitmap_size);
149
150 if (r->is_committed()) {
151 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
152 }
153
154 r = _regions.next();
155 }
156 }
157 };
158
159 static ReservedSpace reserve(size_t size, size_t preferred_page_size) {
160 // When a page size is given we don't want to mix large
161 // and normal pages. If the size is not a multiple of the
162 // page size it will be aligned up to achieve this.
163 size_t alignment = os::vm_allocation_granularity();
164 if (preferred_page_size != os::vm_page_size()) {
165 alignment = MAX2(preferred_page_size, alignment);
166 size = align_up(size, alignment);
167 }
168
169 const ReservedSpace reserved = MemoryReserver::reserve(size, alignment, preferred_page_size);
170 if (!reserved.is_reserved()) {
171 vm_exit_during_initialization("Could not reserve space");
172 }
173 return reserved;
174 }
175
176 jint ShenandoahHeap::initialize() {
177 //
178 // Figure out heap sizing
179 //
180
181 size_t init_byte_size = InitialHeapSize;
182 size_t min_byte_size = MinHeapSize;
183 size_t max_byte_size = MaxHeapSize;
184 size_t heap_alignment = HeapAlignment;
185
186 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
187
188 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
189 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
190
191 _num_regions = ShenandoahHeapRegion::region_count();
192 assert(_num_regions == (max_byte_size / reg_size_bytes),
193 "Regions should cover entire heap exactly: %zu != %zu/%zu",
194 _num_regions, max_byte_size, reg_size_bytes);
195
196 size_t num_committed_regions = init_byte_size / reg_size_bytes;
197 num_committed_regions = MIN2(num_committed_regions, _num_regions);
198 assert(num_committed_regions <= _num_regions, "sanity");
199 _initial_size = num_committed_regions * reg_size_bytes;
200
201 size_t num_min_regions = min_byte_size / reg_size_bytes;
202 num_min_regions = MIN2(num_min_regions, _num_regions);
203 assert(num_min_regions <= _num_regions, "sanity");
204 _minimum_size = num_min_regions * reg_size_bytes;
205
206 // Default to max heap size.
207 _soft_max_size = _num_regions * reg_size_bytes;
208
209 _committed = _initial_size;
210
211 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
212 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
213 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
214
215 //
216 // Reserve and commit memory for heap
217 //
218
219 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
220 initialize_reserved_region(heap_rs);
221 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
222 _heap_region_special = heap_rs.special();
223
224 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
225 "Misaligned heap: " PTR_FORMAT, p2i(base()));
226 os::trace_page_sizes_for_requested_size("Heap",
227 max_byte_size, heap_alignment,
228 heap_rs.base(),
229 heap_rs.size(), heap_rs.page_size());
230
231 #if SHENANDOAH_OPTIMIZED_MARKTASK
232 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
233 // Fail if we ever attempt to address more than we can.
234 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
235 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
236 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
237 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
238 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
239 vm_exit_during_initialization("Fatal Error", buf);
240 }
241 #endif
242
243 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
244 if (!_heap_region_special) {
245 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
246 "Cannot commit heap memory");
247 }
248
249 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
250
251 // Now we know the number of regions and heap sizes, initialize the heuristics.
252 initialize_heuristics();
253
254 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
255
256 //
257 // Worker threads must be initialized after the barrier is configured
258 //
259 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
260 if (_workers == nullptr) {
261 vm_exit_during_initialization("Failed necessary allocation.");
262 } else {
263 _workers->initialize_workers();
264 }
265
266 if (ParallelGCThreads > 1) {
267 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
268 _safepoint_workers->initialize_workers();
269 }
270
271 //
272 // Reserve and commit memory for bitmap(s)
273 //
274
275 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
276 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
277
278 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
279
280 guarantee(bitmap_bytes_per_region != 0,
281 "Bitmap bytes per region should not be zero");
282 guarantee(is_power_of_2(bitmap_bytes_per_region),
283 "Bitmap bytes per region should be power of two: %zu", bitmap_bytes_per_region);
284
285 if (bitmap_page_size > bitmap_bytes_per_region) {
286 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
287 _bitmap_bytes_per_slice = bitmap_page_size;
288 } else {
289 _bitmap_regions_per_slice = 1;
290 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
291 }
292
293 guarantee(_bitmap_regions_per_slice >= 1,
294 "Should have at least one region per slice: %zu",
295 _bitmap_regions_per_slice);
296
297 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
298 "Bitmap slices should be page-granular: bps = %zu, page size = %zu",
299 _bitmap_bytes_per_slice, bitmap_page_size);
300
301 ReservedSpace bitmap = reserve(_bitmap_size, bitmap_page_size);
302 os::trace_page_sizes_for_requested_size("Mark Bitmap",
303 bitmap_size_orig, bitmap_page_size,
304 bitmap.base(),
305 bitmap.size(), bitmap.page_size());
306 MemTracker::record_virtual_memory_tag(bitmap, mtGC);
307 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
308 _bitmap_region_special = bitmap.special();
309
310 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
311 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
312 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
313 if (!_bitmap_region_special) {
314 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
315 "Cannot commit bitmap memory");
316 }
317
318 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
319
320 if (ShenandoahVerify) {
321 ReservedSpace verify_bitmap = reserve(_bitmap_size, bitmap_page_size);
322 os::trace_page_sizes_for_requested_size("Verify Bitmap",
323 bitmap_size_orig, bitmap_page_size,
324 verify_bitmap.base(),
325 verify_bitmap.size(), verify_bitmap.page_size());
326 if (!verify_bitmap.special()) {
327 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
328 "Cannot commit verification bitmap memory");
329 }
330 MemTracker::record_virtual_memory_tag(verify_bitmap, mtGC);
331 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
332 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
333 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
334 }
335
336 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
337 size_t aux_bitmap_page_size = bitmap_page_size;
338
339 ReservedSpace aux_bitmap = reserve(_bitmap_size, aux_bitmap_page_size);
340 os::trace_page_sizes_for_requested_size("Aux Bitmap",
341 bitmap_size_orig, aux_bitmap_page_size,
342 aux_bitmap.base(),
343 aux_bitmap.size(), aux_bitmap.page_size());
344 MemTracker::record_virtual_memory_tag(aux_bitmap, mtGC);
345 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
346 _aux_bitmap_region_special = aux_bitmap.special();
347 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
348
349 //
350 // Create regions and region sets
351 //
352 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
353 size_t region_storage_size_orig = region_align * _num_regions;
354 size_t region_storage_size = align_up(region_storage_size_orig,
355 MAX2(region_page_size, os::vm_allocation_granularity()));
356
357 ReservedSpace region_storage = reserve(region_storage_size, region_page_size);
358 os::trace_page_sizes_for_requested_size("Region Storage",
359 region_storage_size_orig, region_page_size,
360 region_storage.base(),
361 region_storage.size(), region_storage.page_size());
362 MemTracker::record_virtual_memory_tag(region_storage, mtGC);
363 if (!region_storage.special()) {
364 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
365 "Cannot commit region memory");
366 }
367
368 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
369 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
370 // If not successful, bite a bullet and allocate at whatever address.
371 {
372 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
373 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
374 const size_t cset_page_size = os::vm_page_size();
375
376 uintptr_t min = round_up_power_of_2(cset_align);
377 uintptr_t max = (1u << 30u);
378 ReservedSpace cset_rs;
379
380 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
381 char* req_addr = (char*)addr;
382 assert(is_aligned(req_addr, cset_align), "Should be aligned");
383 cset_rs = MemoryReserver::reserve(req_addr, cset_size, cset_align, cset_page_size);
384 if (cset_rs.is_reserved()) {
385 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
386 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
387 break;
388 }
389 }
390
391 if (_collection_set == nullptr) {
392 cset_rs = MemoryReserver::reserve(cset_size, cset_align, os::vm_page_size());
393 if (!cset_rs.is_reserved()) {
394 vm_exit_during_initialization("Cannot reserve memory for collection set");
395 }
396
397 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
398 }
399 os::trace_page_sizes_for_requested_size("Collection Set",
400 cset_size, cset_page_size,
401 cset_rs.base(),
402 cset_rs.size(), cset_rs.page_size());
403 }
404
405 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
406 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
407 _free_set = new ShenandoahFreeSet(this, _num_regions);
408
409 {
410 ShenandoahHeapLocker locker(lock());
411
412 for (size_t i = 0; i < _num_regions; i++) {
413 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
414 bool is_committed = i < num_committed_regions;
415 void* loc = region_storage.base() + i * region_align;
416
417 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
418 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
419
420 _marking_context->initialize_top_at_mark_start(r);
421 _regions[i] = r;
422 assert(!collection_set()->is_in(i), "New region should not be in collection set");
423
424 _affiliations[i] = ShenandoahAffiliation::FREE;
425 }
426
427 // Initialize to complete
428 _marking_context->mark_complete();
429 size_t young_cset_regions, old_cset_regions;
430
431 // We are initializing free set. We ignore cset region tallies.
432 size_t first_old, last_old, num_old;
433 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old, last_old, num_old);
434 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, num_old);
435 }
436
437 if (AlwaysPreTouch) {
438 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
439 // before initialize() below zeroes it with initializing thread. For any given region,
440 // we touch the region and the corresponding bitmaps from the same thread.
441 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
442
443 _pretouch_heap_page_size = heap_page_size;
444 _pretouch_bitmap_page_size = bitmap_page_size;
445
446 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
447 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
448
449 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
450 _workers->run_task(&bcl);
451
452 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
453 _workers->run_task(&hcl);
454 }
455
456 //
457 // Initialize the rest of GC subsystems
458 //
459
460 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
461 for (uint worker = 0; worker < _max_workers; worker++) {
462 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
463 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
464 }
465
466 // There should probably be Shenandoah-specific options for these,
467 // just as there are G1-specific options.
468 {
469 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
470 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
471 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
472 }
473
474 _monitoring_support = new ShenandoahMonitoringSupport(this);
475 _phase_timings = new ShenandoahPhaseTimings(max_workers());
476 ShenandoahCodeRoots::initialize();
477
478 if (ShenandoahPacing) {
479 _pacer = new ShenandoahPacer(this);
480 _pacer->setup_for_idle();
481 }
482
483 initialize_controller();
484
485 if (ShenandoahUncommit) {
486 _uncommit_thread = new ShenandoahUncommitThread(this);
487 }
488
489 print_init_logger();
490
491 FullGCForwarding::initialize(_heap_region);
492
493 return JNI_OK;
494 }
495
496 void ShenandoahHeap::initialize_controller() {
497 _control_thread = new ShenandoahControlThread();
498 }
499
500 void ShenandoahHeap::print_init_logger() const {
501 ShenandoahInitLogger::print();
502 }
503
504 void ShenandoahHeap::initialize_mode() {
505 if (ShenandoahGCMode != nullptr) {
506 if (strcmp(ShenandoahGCMode, "satb") == 0) {
507 _gc_mode = new ShenandoahSATBMode();
508 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
509 _gc_mode = new ShenandoahPassiveMode();
510 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
511 _gc_mode = new ShenandoahGenerationalMode();
512 } else {
513 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
514 }
515 } else {
516 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
517 }
518 _gc_mode->initialize_flags();
519 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
520 vm_exit_during_initialization(
521 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
522 _gc_mode->name()));
523 }
524 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
525 vm_exit_during_initialization(
526 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
527 _gc_mode->name()));
528 }
529 }
530
531 void ShenandoahHeap::initialize_heuristics() {
532 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers(), max_capacity(), max_capacity());
533 _global_generation->initialize_heuristics(mode());
534 }
535
536 #ifdef _MSC_VER
537 #pragma warning( push )
538 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
539 #endif
540
541 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
542 CollectedHeap(),
543 _gc_generation(nullptr),
544 _active_generation(nullptr),
545 _initial_size(0),
546 _committed(0),
547 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
548 _workers(nullptr),
549 _safepoint_workers(nullptr),
550 _heap_region_special(false),
551 _num_regions(0),
552 _regions(nullptr),
553 _affiliations(nullptr),
554 _gc_state_changed(false),
555 _gc_no_progress_count(0),
556 _cancel_requested_time(0),
557 _update_refs_iterator(this),
558 _global_generation(nullptr),
559 _control_thread(nullptr),
560 _uncommit_thread(nullptr),
561 _young_generation(nullptr),
562 _old_generation(nullptr),
563 _shenandoah_policy(policy),
564 _gc_mode(nullptr),
565 _free_set(nullptr),
566 _pacer(nullptr),
567 _verifier(nullptr),
568 _phase_timings(nullptr),
569 _monitoring_support(nullptr),
570 _memory_pool(nullptr),
571 _stw_memory_manager("Shenandoah Pauses"),
572 _cycle_memory_manager("Shenandoah Cycles"),
573 _gc_timer(new ConcurrentGCTimer()),
574 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
575 _marking_context(nullptr),
576 _bitmap_size(0),
577 _bitmap_regions_per_slice(0),
578 _bitmap_bytes_per_slice(0),
579 _bitmap_region_special(false),
580 _aux_bitmap_region_special(false),
581 _liveness_cache(nullptr),
582 _collection_set(nullptr)
583 {
584 // Initialize GC mode early, many subsequent initialization procedures depend on it
585 initialize_mode();
586 _cancelled_gc.set(GCCause::_no_gc);
587 }
588
589 #ifdef _MSC_VER
590 #pragma warning( pop )
591 #endif
592
593 void ShenandoahHeap::print_on(outputStream* st) const {
594 st->print_cr("Shenandoah Heap");
595 st->print_cr(" %zu%s max, %zu%s soft max, %zu%s committed, %zu%s used",
596 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
597 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
598 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
599 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
600 st->print_cr(" %zu x %zu %s regions",
601 num_regions(),
602 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
603 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
604
605 st->print("Status: ");
606 if (has_forwarded_objects()) st->print("has forwarded objects, ");
607 if (!mode()->is_generational()) {
608 if (is_concurrent_mark_in_progress()) st->print("marking,");
609 } else {
610 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
611 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
612 }
613 if (is_evacuation_in_progress()) st->print("evacuating, ");
614 if (is_update_refs_in_progress()) st->print("updating refs, ");
615 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
616 if (is_full_gc_in_progress()) st->print("full gc, ");
617 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
618 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
619 if (is_concurrent_strong_root_in_progress() &&
620 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
621
622 if (cancelled_gc()) {
623 st->print("cancelled");
624 } else {
625 st->print("not cancelled");
626 }
627 st->cr();
628
629 st->print_cr("Reserved region:");
630 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
631 p2i(reserved_region().start()),
632 p2i(reserved_region().end()));
633
634 ShenandoahCollectionSet* cset = collection_set();
635 st->print_cr("Collection set:");
636 if (cset != nullptr) {
637 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
638 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
639 } else {
640 st->print_cr(" (null)");
641 }
642
643 st->cr();
644 MetaspaceUtils::print_on(st);
645
646 if (Verbose) {
647 st->cr();
648 print_heap_regions_on(st);
649 }
650 }
651
652 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
653 public:
654 void do_thread(Thread* thread) {
655 assert(thread != nullptr, "Sanity");
656 ShenandoahThreadLocalData::initialize_gclab(thread);
657 }
658 };
659
660 void ShenandoahHeap::post_initialize() {
661 CollectedHeap::post_initialize();
662
663 // Schedule periodic task to report on gc thread CPU utilization
664 _mmu_tracker.initialize();
665
666 MutexLocker ml(Threads_lock);
667
668 ShenandoahInitWorkerGCLABClosure init_gclabs;
669 _workers->threads_do(&init_gclabs);
670
671 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
672 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
673 _workers->set_initialize_gclab();
674
675 // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump
676 // during a concurrent evacuation phase.
677 if (_safepoint_workers != nullptr) {
678 _safepoint_workers->threads_do(&init_gclabs);
679 _safepoint_workers->set_initialize_gclab();
680 }
681
682 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
683 }
684
685 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
686 return _global_generation->heuristics();
687 }
688
689 size_t ShenandoahHeap::used() const {
690 return global_generation()->used();
691 }
692
693 size_t ShenandoahHeap::committed() const {
694 return Atomic::load(&_committed);
695 }
696
697 void ShenandoahHeap::increase_committed(size_t bytes) {
698 shenandoah_assert_heaplocked_or_safepoint();
699 _committed += bytes;
700 }
701
702 void ShenandoahHeap::decrease_committed(size_t bytes) {
703 shenandoah_assert_heaplocked_or_safepoint();
704 _committed -= bytes;
705 }
706
707 // For tracking usage based on allocations, it should be the case that:
708 // * The sum of regions::used == heap::used
709 // * The sum of a generation's regions::used == generation::used
710 // * The sum of a generation's humongous regions::free == generation::humongous_waste
711 // These invariants are checked by the verifier on GC safepoints.
712 //
713 // Additional notes:
714 // * When a mutator's allocation request causes a region to be retired, the
715 // free memory left in that region is considered waste. It does not contribute
716 // to the usage, but it _does_ contribute to allocation rate.
717 // * The bottom of a PLAB must be aligned on card size. In some cases this will
718 // require padding in front of the PLAB (a filler object). Because this padding
719 // is included in the region's used memory we include the padding in the usage
720 // accounting as waste.
721 // * Mutator allocations are used to compute an allocation rate. They are also
722 // sent to the Pacer for those purposes.
723 // * There are three sources of waste:
724 // 1. The padding used to align a PLAB on card size
725 // 2. Region's free is less than minimum TLAB size and is retired
726 // 3. The unused portion of memory in the last region of a humongous object
727 void ShenandoahHeap::increase_used(const ShenandoahAllocRequest& req) {
728 size_t actual_bytes = req.actual_size() * HeapWordSize;
729 size_t wasted_bytes = req.waste() * HeapWordSize;
730 ShenandoahGeneration* generation = generation_for(req.affiliation());
731
732 if (req.is_gc_alloc()) {
733 assert(wasted_bytes == 0 || req.type() == ShenandoahAllocRequest::_alloc_plab, "Only PLABs have waste");
734 increase_used(generation, actual_bytes + wasted_bytes);
735 } else {
736 assert(req.is_mutator_alloc(), "Expected mutator alloc here");
737 // padding and actual size both count towards allocation counter
738 generation->increase_allocated(actual_bytes + wasted_bytes);
739
740 // only actual size counts toward usage for mutator allocations
741 increase_used(generation, actual_bytes);
742
743 // notify pacer of both actual size and waste
744 notify_mutator_alloc_words(req.actual_size(), req.waste());
745
746 if (wasted_bytes > 0 && ShenandoahHeapRegion::requires_humongous(req.actual_size())) {
747 increase_humongous_waste(generation,wasted_bytes);
748 }
749 }
750 }
751
752 void ShenandoahHeap::increase_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
753 generation->increase_humongous_waste(bytes);
754 if (!generation->is_global()) {
755 global_generation()->increase_humongous_waste(bytes);
756 }
757 }
758
759 void ShenandoahHeap::decrease_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
760 generation->decrease_humongous_waste(bytes);
761 if (!generation->is_global()) {
762 global_generation()->decrease_humongous_waste(bytes);
763 }
764 }
765
766 void ShenandoahHeap::increase_used(ShenandoahGeneration* generation, size_t bytes) {
767 generation->increase_used(bytes);
768 if (!generation->is_global()) {
769 global_generation()->increase_used(bytes);
770 }
771 }
772
773 void ShenandoahHeap::decrease_used(ShenandoahGeneration* generation, size_t bytes) {
774 generation->decrease_used(bytes);
775 if (!generation->is_global()) {
776 global_generation()->decrease_used(bytes);
777 }
778 }
779
780 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, size_t waste) {
781 if (ShenandoahPacing) {
782 control_thread()->pacing_notify_alloc(words);
783 if (waste > 0) {
784 pacer()->claim_for_alloc<true>(waste);
785 }
786 }
787 }
788
789 size_t ShenandoahHeap::capacity() const {
790 return committed();
791 }
792
793 size_t ShenandoahHeap::max_capacity() const {
794 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
795 }
796
797 size_t ShenandoahHeap::soft_max_capacity() const {
798 size_t v = Atomic::load(&_soft_max_size);
799 assert(min_capacity() <= v && v <= max_capacity(),
800 "Should be in bounds: %zu <= %zu <= %zu",
801 min_capacity(), v, max_capacity());
802 return v;
803 }
804
805 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
806 assert(min_capacity() <= v && v <= max_capacity(),
807 "Should be in bounds: %zu <= %zu <= %zu",
808 min_capacity(), v, max_capacity());
809 Atomic::store(&_soft_max_size, v);
810 }
811
812 size_t ShenandoahHeap::min_capacity() const {
813 return _minimum_size;
814 }
815
816 size_t ShenandoahHeap::initial_capacity() const {
817 return _initial_size;
818 }
819
820 bool ShenandoahHeap::is_in(const void* p) const {
821 if (!is_in_reserved(p)) {
822 return false;
823 }
824
825 if (is_full_gc_move_in_progress()) {
826 // Full GC move is running, we do not have a consistent region
827 // information yet. But we know the pointer is in heap.
828 return true;
829 }
830
831 // Now check if we point to a live section in active region.
832 const ShenandoahHeapRegion* r = heap_region_containing(p);
833 if (p >= r->top()) {
834 return false;
835 }
836
837 if (r->is_active()) {
838 return true;
839 }
840
841 // The region is trash, but won't be recycled until after concurrent weak
842 // roots. We also don't allow mutators to allocate from trash regions
843 // during weak roots. Concurrent class unloading may access unmarked oops
844 // in trash regions.
845 return r->is_trash() && is_concurrent_weak_root_in_progress();
846 }
847
848 void ShenandoahHeap::notify_soft_max_changed() {
849 if (_uncommit_thread != nullptr) {
850 _uncommit_thread->notify_soft_max_changed();
851 }
852 }
853
854 void ShenandoahHeap::notify_explicit_gc_requested() {
855 if (_uncommit_thread != nullptr) {
856 _uncommit_thread->notify_explicit_gc_requested();
857 }
858 }
859
860 bool ShenandoahHeap::check_soft_max_changed() {
861 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
862 size_t old_soft_max = soft_max_capacity();
863 if (new_soft_max != old_soft_max) {
864 new_soft_max = MAX2(min_capacity(), new_soft_max);
865 new_soft_max = MIN2(max_capacity(), new_soft_max);
866 if (new_soft_max != old_soft_max) {
867 log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s",
868 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
869 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
870 );
871 set_soft_max_capacity(new_soft_max);
872 return true;
873 }
874 }
875 return false;
876 }
877
878 void ShenandoahHeap::notify_heap_changed() {
879 // Update monitoring counters when we took a new region. This amortizes the
880 // update costs on slow path.
881 monitoring_support()->notify_heap_changed();
882 _heap_changed.try_set();
883 }
884
885 void ShenandoahHeap::set_forced_counters_update(bool value) {
886 monitoring_support()->set_forced_counters_update(value);
887 }
888
889 void ShenandoahHeap::handle_force_counters_update() {
890 monitoring_support()->handle_force_counters_update();
891 }
892
893 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
894 // New object should fit the GCLAB size
895 size_t min_size = MAX2(size, PLAB::min_size());
896
897 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
898 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
899
900 new_size = MIN2(new_size, PLAB::max_size());
901 new_size = MAX2(new_size, PLAB::min_size());
902
903 // Record new heuristic value even if we take any shortcut. This captures
904 // the case when moderately-sized objects always take a shortcut. At some point,
905 // heuristics should catch up with them.
906 log_debug(gc, free)("Set new GCLAB size: %zu", new_size);
907 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
908
909 if (new_size < size) {
910 // New size still does not fit the object. Fall back to shared allocation.
911 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
912 log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size);
913 return nullptr;
914 }
915
916 // Retire current GCLAB, and allocate a new one.
917 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
918 gclab->retire();
919
920 size_t actual_size = 0;
921 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
922 if (gclab_buf == nullptr) {
923 return nullptr;
924 }
925
926 assert (size <= actual_size, "allocation should fit");
927
928 // ...and clear or zap just allocated TLAB, if needed.
929 if (ZeroTLAB) {
930 Copy::zero_to_words(gclab_buf, actual_size);
931 } else if (ZapTLAB) {
932 // Skip mangling the space corresponding to the object header to
933 // ensure that the returned space is not considered parsable by
934 // any concurrent GC thread.
935 size_t hdr_size = oopDesc::header_size();
936 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
937 }
938 gclab->set_buf(gclab_buf, actual_size);
939 return gclab->allocate(size);
940 }
941
942 // Called from stubs in JIT code or interpreter
943 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
944 size_t requested_size,
945 size_t* actual_size) {
946 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
947 HeapWord* res = allocate_memory(req);
948 if (res != nullptr) {
949 *actual_size = req.actual_size();
950 } else {
951 *actual_size = 0;
952 }
953 return res;
954 }
955
956 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
957 size_t word_size,
958 size_t* actual_size) {
959 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
960 HeapWord* res = allocate_memory(req);
961 if (res != nullptr) {
962 *actual_size = req.actual_size();
963 } else {
964 *actual_size = 0;
965 }
966 return res;
967 }
968
969 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
970 intptr_t pacer_epoch = 0;
971 bool in_new_region = false;
972 HeapWord* result = nullptr;
973
974 if (req.is_mutator_alloc()) {
975 if (ShenandoahPacing) {
976 pacer()->pace_for_alloc(req.size());
977 pacer_epoch = pacer()->epoch();
978 }
979
980 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
981 result = allocate_memory_under_lock(req, in_new_region);
982 }
983
984 // Check that gc overhead is not exceeded.
985 //
986 // Shenandoah will grind along for quite a while allocating one
987 // object at a time using shared (non-tlab) allocations. This check
988 // is testing that the GC overhead limit has not been exceeded.
989 // This will notify the collector to start a cycle, but will raise
990 // an OOME to the mutator if the last Full GCs have not made progress.
991 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
992 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
993 control_thread()->handle_alloc_failure(req, false);
994 req.set_actual_size(0);
995 return nullptr;
996 }
997
998 if (result == nullptr) {
999 // Block until control thread reacted, then retry allocation.
1000 //
1001 // It might happen that one of the threads requesting allocation would unblock
1002 // way later after GC happened, only to fail the second allocation, because
1003 // other threads have already depleted the free storage. In this case, a better
1004 // strategy is to try again, until at least one full GC has completed.
1005 //
1006 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
1007 // a) We experienced a GC that had good progress, or
1008 // b) We experienced at least one Full GC (whether or not it had good progress)
1009
1010 const size_t original_count = shenandoah_policy()->full_gc_count();
1011 while (result == nullptr && should_retry_allocation(original_count)) {
1012 control_thread()->handle_alloc_failure(req, true);
1013 result = allocate_memory_under_lock(req, in_new_region);
1014 }
1015 if (result != nullptr) {
1016 // If our allocation request has been satisfied after it initially failed, we count this as good gc progress
1017 notify_gc_progress();
1018 }
1019 if (log_develop_is_enabled(Debug, gc, alloc)) {
1020 ResourceMark rm;
1021 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu"
1022 ", Original: %zu, Latest: %zu",
1023 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
1024 original_count, get_gc_no_progress_count());
1025 }
1026 }
1027 } else {
1028 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
1029 result = allocate_memory_under_lock(req, in_new_region);
1030 // Do not call handle_alloc_failure() here, because we cannot block.
1031 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1032 }
1033
1034 if (in_new_region) {
1035 notify_heap_changed();
1036 }
1037
1038 if (result == nullptr) {
1039 req.set_actual_size(0);
1040 }
1041
1042 // This is called regardless of the outcome of the allocation to account
1043 // for any waste created by retiring regions with this request.
1044 increase_used(req);
1045
1046 if (result != nullptr) {
1047 size_t requested = req.size();
1048 size_t actual = req.actual_size();
1049
1050 assert (req.is_lab_alloc() || (requested == actual),
1051 "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu",
1052 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
1053
1054 if (req.is_mutator_alloc()) {
1055 // If we requested more than we were granted, give the rest back to pacer.
1056 // This only matters if we are in the same pacing epoch: do not try to unpace
1057 // over the budget for the other phase.
1058 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
1059 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
1060 }
1061 }
1062 }
1063
1064 return result;
1065 }
1066
1067 inline bool ShenandoahHeap::should_retry_allocation(size_t original_full_gc_count) const {
1068 return shenandoah_policy()->full_gc_count() == original_full_gc_count
1069 && !shenandoah_policy()->is_at_shutdown();
1070 }
1071
1072 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1073 // If we are dealing with mutator allocation, then we may need to block for safepoint.
1074 // We cannot block for safepoint for GC allocations, because there is a high chance
1075 // we are already running at safepoint or from stack watermark machinery, and we cannot
1076 // block again.
1077 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1078
1079 // Make sure the old generation has room for either evacuations or promotions before trying to allocate.
1080 if (req.is_old() && !old_generation()->can_allocate(req)) {
1081 return nullptr;
1082 }
1083
1084 // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available
1085 // memory.
1086 HeapWord* result = _free_set->allocate(req, in_new_region);
1087
1088 // Record the plab configuration for this result and register the object.
1089 if (result != nullptr && req.is_old()) {
1090 old_generation()->configure_plab_for_current_thread(req);
1091 if (req.type() == ShenandoahAllocRequest::_alloc_shared_gc) {
1092 // Register the newly allocated object while we're holding the global lock since there's no synchronization
1093 // built in to the implementation of register_object(). There are potential races when multiple independent
1094 // threads are allocating objects, some of which might span the same card region. For example, consider
1095 // a card table's memory region within which three objects are being allocated by three different threads:
1096 //
1097 // objects being "concurrently" allocated:
1098 // [-----a------][-----b-----][--------------c------------------]
1099 // [---- card table memory range --------------]
1100 //
1101 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a
1102 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region.
1103 // Allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region.
1104 // Allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this
1105 // card region.
1106 //
1107 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as
1108 // last-start representing object b while first-start represents object c. This is why we need to require all
1109 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range.
1110 old_generation()->card_scan()->register_object(result);
1111 }
1112 }
1113
1114 return result;
1115 }
1116
1117 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1118 bool* gc_overhead_limit_was_exceeded) {
1119 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1120 return allocate_memory(req);
1121 }
1122
1123 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1124 size_t size,
1125 Metaspace::MetadataType mdtype) {
1126 MetaWord* result;
1127
1128 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1129 ShenandoahHeuristics* h = global_generation()->heuristics();
1130 if (h->can_unload_classes()) {
1131 h->record_metaspace_oom();
1132 }
1133
1134 // Expand and retry allocation
1135 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1136 if (result != nullptr) {
1137 return result;
1138 }
1139
1140 // Start full GC
1141 collect(GCCause::_metadata_GC_clear_soft_refs);
1142
1143 // Retry allocation
1144 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1145 if (result != nullptr) {
1146 return result;
1147 }
1148
1149 // Expand and retry allocation
1150 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1151 if (result != nullptr) {
1152 return result;
1153 }
1154
1155 // Out of memory
1156 return nullptr;
1157 }
1158
1159 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1160 private:
1161 ShenandoahHeap* const _heap;
1162 Thread* const _thread;
1163 public:
1164 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1165 _heap(heap), _thread(Thread::current()) {}
1166
1167 void do_object(oop p) {
1168 shenandoah_assert_marked(nullptr, p);
1169 if (!p->is_forwarded()) {
1170 _heap->evacuate_object(p, _thread);
1171 }
1172 }
1173 };
1174
1175 class ShenandoahEvacuationTask : public WorkerTask {
1176 private:
1177 ShenandoahHeap* const _sh;
1178 ShenandoahCollectionSet* const _cs;
1179 bool _concurrent;
1180 public:
1181 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1182 ShenandoahCollectionSet* cs,
1183 bool concurrent) :
1184 WorkerTask("Shenandoah Evacuation"),
1185 _sh(sh),
1186 _cs(cs),
1187 _concurrent(concurrent)
1188 {}
1189
1190 void work(uint worker_id) {
1191 if (_concurrent) {
1192 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1193 ShenandoahSuspendibleThreadSetJoiner stsj;
1194 ShenandoahEvacOOMScope oom_evac_scope;
1195 do_work();
1196 } else {
1197 ShenandoahParallelWorkerSession worker_session(worker_id);
1198 ShenandoahEvacOOMScope oom_evac_scope;
1199 do_work();
1200 }
1201 }
1202
1203 private:
1204 void do_work() {
1205 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1206 ShenandoahHeapRegion* r;
1207 while ((r =_cs->claim_next()) != nullptr) {
1208 assert(r->has_live(), "Region %zu should have been reclaimed early", r->index());
1209 _sh->marked_object_iterate(r, &cl);
1210
1211 if (ShenandoahPacing) {
1212 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1213 }
1214
1215 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1216 break;
1217 }
1218 }
1219 }
1220 };
1221
1222 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1223 private:
1224 bool const _resize;
1225 public:
1226 explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1227 void do_thread(Thread* thread) override {
1228 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1229 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1230 gclab->retire();
1231 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1232 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1233 }
1234
1235 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1236 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1237 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1238
1239 // There are two reasons to retire all plabs between old-gen evacuation passes.
1240 // 1. We need to make the plab memory parsable by remembered-set scanning.
1241 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1242 ShenandoahGenerationalHeap::heap()->retire_plab(plab, thread);
1243 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) {
1244 ShenandoahThreadLocalData::set_plab_size(thread, 0);
1245 }
1246 }
1247 }
1248 };
1249
1250 class ShenandoahGCStatePropagator : public HandshakeClosure {
1251 public:
1252 explicit ShenandoahGCStatePropagator(char gc_state) :
1253 HandshakeClosure("Shenandoah GC State Change"),
1254 _gc_state(gc_state) {}
1255
1256 void do_thread(Thread* thread) override {
1257 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state);
1258 }
1259 private:
1260 char _gc_state;
1261 };
1262
1263 class ShenandoahPrepareForUpdateRefs : public HandshakeClosure {
1264 public:
1265 explicit ShenandoahPrepareForUpdateRefs(char gc_state) :
1266 HandshakeClosure("Shenandoah Prepare for Update Refs"),
1267 _retire(ResizeTLAB), _propagator(gc_state) {}
1268
1269 void do_thread(Thread* thread) override {
1270 _propagator.do_thread(thread);
1271 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) {
1272 _retire.do_thread(thread);
1273 }
1274 }
1275 private:
1276 ShenandoahRetireGCLABClosure _retire;
1277 ShenandoahGCStatePropagator _propagator;
1278 };
1279
1280 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1281 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1282 workers()->run_task(&task);
1283 }
1284
1285 void ShenandoahHeap::concurrent_prepare_for_update_refs() {
1286 {
1287 // Java threads take this lock while they are being attached and added to the list of thread.
1288 // If another thread holds this lock before we update the gc state, it will receive a stale
1289 // gc state, but they will have been added to the list of java threads and so will be corrected
1290 // by the following handshake.
1291 MutexLocker lock(Threads_lock);
1292
1293 // A cancellation at this point means the degenerated cycle must resume from update-refs.
1294 set_gc_state_concurrent(EVACUATION, false);
1295 set_gc_state_concurrent(WEAK_ROOTS, false);
1296 set_gc_state_concurrent(UPDATE_REFS, true);
1297 }
1298
1299 // This will propagate the gc state and retire gclabs and plabs for threads that require it.
1300 ShenandoahPrepareForUpdateRefs prepare_for_update_refs(_gc_state.raw_value());
1301
1302 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately.
1303 Threads::non_java_threads_do(&prepare_for_update_refs);
1304
1305 // Now retire gclabs and plabs and propagate gc_state for mutator threads
1306 Handshake::execute(&prepare_for_update_refs);
1307
1308 _update_refs_iterator.reset();
1309 }
1310
1311 class ShenandoahCompositeHandshakeClosure : public HandshakeClosure {
1312 HandshakeClosure* _handshake_1;
1313 HandshakeClosure* _handshake_2;
1314 public:
1315 ShenandoahCompositeHandshakeClosure(HandshakeClosure* handshake_1, HandshakeClosure* handshake_2) :
1316 HandshakeClosure(handshake_2->name()),
1317 _handshake_1(handshake_1), _handshake_2(handshake_2) {}
1318
1319 void do_thread(Thread* thread) override {
1320 _handshake_1->do_thread(thread);
1321 _handshake_2->do_thread(thread);
1322 }
1323 };
1324
1325 void ShenandoahHeap::concurrent_final_roots(HandshakeClosure* handshake_closure) {
1326 {
1327 assert(!is_evacuation_in_progress(), "Should not evacuate for abbreviated or old cycles");
1328 MutexLocker lock(Threads_lock);
1329 set_gc_state_concurrent(WEAK_ROOTS, false);
1330 }
1331
1332 ShenandoahGCStatePropagator propagator(_gc_state.raw_value());
1333 Threads::non_java_threads_do(&propagator);
1334 if (handshake_closure == nullptr) {
1335 Handshake::execute(&propagator);
1336 } else {
1337 ShenandoahCompositeHandshakeClosure composite(&propagator, handshake_closure);
1338 Handshake::execute(&composite);
1339 }
1340 }
1341
1342 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1343 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1344 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
1345 // This thread went through the OOM during evac protocol. It is safe to return
1346 // the forward pointer. It must not attempt to evacuate any other objects.
1347 return ShenandoahBarrierSet::resolve_forwarded(p);
1348 }
1349
1350 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1351
1352 ShenandoahHeapRegion* r = heap_region_containing(p);
1353 assert(!r->is_humongous(), "never evacuate humongous objects");
1354
1355 ShenandoahAffiliation target_gen = r->affiliation();
1356 return try_evacuate_object(p, thread, r, target_gen);
1357 }
1358
1359 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1360 ShenandoahAffiliation target_gen) {
1361 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1362 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1363 bool alloc_from_lab = true;
1364 HeapWord* copy = nullptr;
1365 size_t size = ShenandoahForwarding::size(p);
1366
1367 #ifdef ASSERT
1368 if (ShenandoahOOMDuringEvacALot &&
1369 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1370 copy = nullptr;
1371 } else {
1372 #endif
1373 if (UseTLAB) {
1374 copy = allocate_from_gclab(thread, size);
1375 }
1376 if (copy == nullptr) {
1377 // If we failed to allocate in LAB, we'll try a shared allocation.
1378 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1379 copy = allocate_memory(req);
1380 alloc_from_lab = false;
1381 }
1382 #ifdef ASSERT
1383 }
1384 #endif
1385
1386 if (copy == nullptr) {
1387 control_thread()->handle_alloc_failure_evac(size);
1388
1389 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1390
1391 return ShenandoahBarrierSet::resolve_forwarded(p);
1392 }
1393
1394 // Copy the object:
1395 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1396
1397 // Try to install the new forwarding pointer.
1398 oop copy_val = cast_to_oop(copy);
1399 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1400 if (result == copy_val) {
1401 // Successfully evacuated. Our copy is now the public one!
1402 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1403 shenandoah_assert_correct(nullptr, copy_val);
1404 return copy_val;
1405 } else {
1406 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1407 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1408 // But if it happens to contain references to evacuated regions, those references would
1409 // not get updated for this stale copy during this cycle, and we will crash while scanning
1410 // it the next cycle.
1411 if (alloc_from_lab) {
1412 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1413 // object will overwrite this stale copy, or the filler object on LAB retirement will
1414 // do this.
1415 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1416 } else {
1417 // For non-LAB allocations, we have no way to retract the allocation, and
1418 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1419 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1420 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1421 fill_with_object(copy, size);
1422 shenandoah_assert_correct(nullptr, copy_val);
1423 // For non-LAB allocations, the object has already been registered
1424 }
1425 shenandoah_assert_correct(nullptr, result);
1426 return result;
1427 }
1428 }
1429
1430 void ShenandoahHeap::trash_cset_regions() {
1431 ShenandoahHeapLocker locker(lock());
1432
1433 ShenandoahCollectionSet* set = collection_set();
1434 ShenandoahHeapRegion* r;
1435 set->clear_current_index();
1436 while ((r = set->next()) != nullptr) {
1437 r->make_trash();
1438 }
1439 collection_set()->clear();
1440 }
1441
1442 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1443 st->print_cr("Heap Regions:");
1444 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1445 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1446 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1447 st->print_cr("UWM=update watermark, U=used");
1448 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1449 st->print_cr("S=shared allocs, L=live data");
1450 st->print_cr("CP=critical pins");
1451
1452 for (size_t i = 0; i < num_regions(); i++) {
1453 get_region(i)->print_on(st);
1454 }
1455 }
1456
1457 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1458 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1459
1460 oop humongous_obj = cast_to_oop(start->bottom());
1461 size_t size = humongous_obj->size();
1462 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1463 size_t index = start->index() + required_regions - 1;
1464
1465 assert(!start->has_live(), "liveness must be zero");
1466
1467 for(size_t i = 0; i < required_regions; i++) {
1468 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1469 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1470 ShenandoahHeapRegion* region = get_region(index --);
1471
1472 assert(region->is_humongous(), "expect correct humongous start or continuation");
1473 assert(!region->is_cset(), "Humongous region should not be in collection set");
1474
1475 region->make_trash_immediate();
1476 }
1477 return required_regions;
1478 }
1479
1480 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1481 public:
1482 ShenandoahCheckCleanGCLABClosure() {}
1483 void do_thread(Thread* thread) {
1484 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1485 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1486 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1487
1488 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1489 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1490 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1491 assert(plab->words_remaining() == 0, "PLAB should not need retirement");
1492 }
1493 }
1494 };
1495
1496 void ShenandoahHeap::labs_make_parsable() {
1497 assert(UseTLAB, "Only call with UseTLAB");
1498
1499 ShenandoahRetireGCLABClosure cl(false);
1500
1501 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1502 ThreadLocalAllocBuffer& tlab = t->tlab();
1503 tlab.make_parsable();
1504 cl.do_thread(t);
1505 }
1506
1507 workers()->threads_do(&cl);
1508
1509 if (safepoint_workers() != nullptr) {
1510 safepoint_workers()->threads_do(&cl);
1511 }
1512 }
1513
1514 void ShenandoahHeap::tlabs_retire(bool resize) {
1515 assert(UseTLAB, "Only call with UseTLAB");
1516 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1517
1518 ThreadLocalAllocStats stats;
1519
1520 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1521 ThreadLocalAllocBuffer& tlab = t->tlab();
1522 tlab.retire(&stats);
1523 if (resize) {
1524 tlab.resize();
1525 }
1526 }
1527
1528 stats.publish();
1529
1530 #ifdef ASSERT
1531 ShenandoahCheckCleanGCLABClosure cl;
1532 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1533 cl.do_thread(t);
1534 }
1535 workers()->threads_do(&cl);
1536 #endif
1537 }
1538
1539 void ShenandoahHeap::gclabs_retire(bool resize) {
1540 assert(UseTLAB, "Only call with UseTLAB");
1541 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1542
1543 ShenandoahRetireGCLABClosure cl(resize);
1544 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1545 cl.do_thread(t);
1546 }
1547
1548 workers()->threads_do(&cl);
1549
1550 if (safepoint_workers() != nullptr) {
1551 safepoint_workers()->threads_do(&cl);
1552 }
1553 }
1554
1555 // Returns size in bytes
1556 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1557 // Return the max allowed size, and let the allocation path
1558 // figure out the safe size for current allocation.
1559 return ShenandoahHeapRegion::max_tlab_size_bytes();
1560 }
1561
1562 size_t ShenandoahHeap::max_tlab_size() const {
1563 // Returns size in words
1564 return ShenandoahHeapRegion::max_tlab_size_words();
1565 }
1566
1567 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) {
1568 // These requests are ignored because we can't easily have Shenandoah jump into
1569 // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent
1570 // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly
1571 // on the VM thread, but this would confuse the control thread mightily and doesn't
1572 // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a
1573 // concurrent cycle in the prologue of the heap inspect/dump operation. This is how
1574 // other concurrent collectors in the JVM handle this scenario as well.
1575 assert(Thread::current()->is_VM_thread(), "Should be the VM thread");
1576 guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause");
1577 }
1578
1579 void ShenandoahHeap::collect(GCCause::Cause cause) {
1580 control_thread()->request_gc(cause);
1581 }
1582
1583 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1584 //assert(false, "Shouldn't need to do full collections");
1585 }
1586
1587 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1588 ShenandoahHeapRegion* r = heap_region_containing(addr);
1589 if (r != nullptr) {
1590 return r->block_start(addr);
1591 }
1592 return nullptr;
1593 }
1594
1595 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1596 ShenandoahHeapRegion* r = heap_region_containing(addr);
1597 return r->block_is_obj(addr);
1598 }
1599
1600 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1601 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1602 }
1603
1604 void ShenandoahHeap::prepare_for_verify() {
1605 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1606 labs_make_parsable();
1607 }
1608 }
1609
1610 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1611 if (_shenandoah_policy->is_at_shutdown()) {
1612 return;
1613 }
1614
1615 if (_control_thread != nullptr) {
1616 tcl->do_thread(_control_thread);
1617 }
1618
1619 if (_uncommit_thread != nullptr) {
1620 tcl->do_thread(_uncommit_thread);
1621 }
1622
1623 workers()->threads_do(tcl);
1624 if (_safepoint_workers != nullptr) {
1625 _safepoint_workers->threads_do(tcl);
1626 }
1627 }
1628
1629 void ShenandoahHeap::print_tracing_info() const {
1630 LogTarget(Info, gc, stats) lt;
1631 if (lt.is_enabled()) {
1632 ResourceMark rm;
1633 LogStream ls(lt);
1634
1635 phase_timings()->print_global_on(&ls);
1636
1637 ls.cr();
1638 ls.cr();
1639
1640 shenandoah_policy()->print_gc_stats(&ls);
1641
1642 ls.cr();
1643 ls.cr();
1644 }
1645 }
1646
1647 void ShenandoahHeap::set_gc_generation(ShenandoahGeneration* generation) {
1648 shenandoah_assert_control_or_vm_thread_at_safepoint();
1649 _gc_generation = generation;
1650 }
1651
1652 // Active generation may only be set by the VM thread at a safepoint.
1653 void ShenandoahHeap::set_active_generation() {
1654 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1655 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1656 assert(_gc_generation != nullptr, "Will set _active_generation to nullptr");
1657 _active_generation = _gc_generation;
1658 }
1659
1660 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
1661 shenandoah_policy()->record_collection_cause(cause);
1662
1663 const GCCause::Cause current = gc_cause();
1664 assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s",
1665 GCCause::to_string(current), GCCause::to_string(cause));
1666 assert(_gc_generation == nullptr, "Over-writing _gc_generation");
1667
1668 set_gc_cause(cause);
1669 set_gc_generation(generation);
1670
1671 generation->heuristics()->record_cycle_start();
1672 }
1673
1674 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1675 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1676 assert(_gc_generation != nullptr, "_gc_generation wasn't set");
1677
1678 generation->heuristics()->record_cycle_end();
1679 if (mode()->is_generational() && generation->is_global()) {
1680 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1681 young_generation()->heuristics()->record_cycle_end();
1682 old_generation()->heuristics()->record_cycle_end();
1683 }
1684
1685 set_gc_generation(nullptr);
1686 set_gc_cause(GCCause::_no_gc);
1687 }
1688
1689 void ShenandoahHeap::verify(VerifyOption vo) {
1690 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1691 if (ShenandoahVerify) {
1692 verifier()->verify_generic(vo);
1693 } else {
1694 // TODO: Consider allocating verification bitmaps on demand,
1695 // and turn this on unconditionally.
1696 }
1697 }
1698 }
1699 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1700 return _free_set->capacity();
1701 }
1702
1703 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1704 private:
1705 MarkBitMap* _bitmap;
1706 ShenandoahScanObjectStack* _oop_stack;
1707 ShenandoahHeap* const _heap;
1708 ShenandoahMarkingContext* const _marking_context;
1709
1710 template <class T>
1711 void do_oop_work(T* p) {
1712 T o = RawAccess<>::oop_load(p);
1713 if (!CompressedOops::is_null(o)) {
1714 oop obj = CompressedOops::decode_not_null(o);
1715 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1716 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1717 return;
1718 }
1719 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1720
1721 assert(oopDesc::is_oop(obj), "must be a valid oop");
1722 if (!_bitmap->is_marked(obj)) {
1723 _bitmap->mark(obj);
1724 _oop_stack->push(obj);
1725 }
1726 }
1727 }
1728 public:
1729 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1730 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1731 _marking_context(_heap->marking_context()) {}
1732 void do_oop(oop* p) { do_oop_work(p); }
1733 void do_oop(narrowOop* p) { do_oop_work(p); }
1734 };
1735
1736 /*
1737 * This is public API, used in preparation of object_iterate().
1738 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1739 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1740 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1741 */
1742 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1743 // No-op.
1744 }
1745
1746 /*
1747 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1748 *
1749 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1750 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1751 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1752 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1753 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1754 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1755 * wiped the bitmap in preparation for next marking).
1756 *
1757 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1758 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1759 * is allowed to report dead objects, but is not required to do so.
1760 */
1761 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1762 // Reset bitmap
1763 if (!prepare_aux_bitmap_for_iteration())
1764 return;
1765
1766 ShenandoahScanObjectStack oop_stack;
1767 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1768 // Seed the stack with root scan
1769 scan_roots_for_iteration(&oop_stack, &oops);
1770
1771 // Work through the oop stack to traverse heap
1772 while (! oop_stack.is_empty()) {
1773 oop obj = oop_stack.pop();
1774 assert(oopDesc::is_oop(obj), "must be a valid oop");
1775 cl->do_object(obj);
1776 obj->oop_iterate(&oops);
1777 }
1778
1779 assert(oop_stack.is_empty(), "should be empty");
1780 // Reclaim bitmap
1781 reclaim_aux_bitmap_for_iteration();
1782 }
1783
1784 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1785 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1786
1787 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1788 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1789 return false;
1790 }
1791 // Reset bitmap
1792 _aux_bit_map.clear();
1793 return true;
1794 }
1795
1796 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1797 // Process GC roots according to current GC cycle
1798 // This populates the work stack with initial objects
1799 // It is important to relinquish the associated locks before diving
1800 // into heap dumper
1801 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1802 ShenandoahHeapIterationRootScanner rp(n_workers);
1803 rp.roots_do(oops);
1804 }
1805
1806 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1807 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1808 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1809 }
1810 }
1811
1812 // Closure for parallelly iterate objects
1813 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1814 private:
1815 MarkBitMap* _bitmap;
1816 ShenandoahObjToScanQueue* _queue;
1817 ShenandoahHeap* const _heap;
1818 ShenandoahMarkingContext* const _marking_context;
1819
1820 template <class T>
1821 void do_oop_work(T* p) {
1822 T o = RawAccess<>::oop_load(p);
1823 if (!CompressedOops::is_null(o)) {
1824 oop obj = CompressedOops::decode_not_null(o);
1825 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1826 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1827 return;
1828 }
1829 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1830
1831 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1832 if (_bitmap->par_mark(obj)) {
1833 _queue->push(ShenandoahMarkTask(obj));
1834 }
1835 }
1836 }
1837 public:
1838 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1839 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1840 _marking_context(_heap->marking_context()) {}
1841 void do_oop(oop* p) { do_oop_work(p); }
1842 void do_oop(narrowOop* p) { do_oop_work(p); }
1843 };
1844
1845 // Object iterator for parallel heap iteraion.
1846 // The root scanning phase happenes in construction as a preparation of
1847 // parallel marking queues.
1848 // Every worker processes it's own marking queue. work-stealing is used
1849 // to balance workload.
1850 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1851 private:
1852 uint _num_workers;
1853 bool _init_ready;
1854 MarkBitMap* _aux_bit_map;
1855 ShenandoahHeap* _heap;
1856 ShenandoahScanObjectStack _roots_stack; // global roots stack
1857 ShenandoahObjToScanQueueSet* _task_queues;
1858 public:
1859 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1860 _num_workers(num_workers),
1861 _init_ready(false),
1862 _aux_bit_map(bitmap),
1863 _heap(ShenandoahHeap::heap()) {
1864 // Initialize bitmap
1865 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1866 if (!_init_ready) {
1867 return;
1868 }
1869
1870 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1871 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1872
1873 _init_ready = prepare_worker_queues();
1874 }
1875
1876 ~ShenandoahParallelObjectIterator() {
1877 // Reclaim bitmap
1878 _heap->reclaim_aux_bitmap_for_iteration();
1879 // Reclaim queue for workers
1880 if (_task_queues!= nullptr) {
1881 for (uint i = 0; i < _num_workers; ++i) {
1882 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1883 if (q != nullptr) {
1884 delete q;
1885 _task_queues->register_queue(i, nullptr);
1886 }
1887 }
1888 delete _task_queues;
1889 _task_queues = nullptr;
1890 }
1891 }
1892
1893 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1894 if (_init_ready) {
1895 object_iterate_parallel(cl, worker_id, _task_queues);
1896 }
1897 }
1898
1899 private:
1900 // Divide global root_stack into worker queues
1901 bool prepare_worker_queues() {
1902 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1903 // Initialize queues for every workers
1904 for (uint i = 0; i < _num_workers; ++i) {
1905 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1906 _task_queues->register_queue(i, task_queue);
1907 }
1908 // Divide roots among the workers. Assume that object referencing distribution
1909 // is related with root kind, use round-robin to make every worker have same chance
1910 // to process every kind of roots
1911 size_t roots_num = _roots_stack.size();
1912 if (roots_num == 0) {
1913 // No work to do
1914 return false;
1915 }
1916
1917 for (uint j = 0; j < roots_num; j++) {
1918 uint stack_id = j % _num_workers;
1919 oop obj = _roots_stack.pop();
1920 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1921 }
1922 return true;
1923 }
1924
1925 void object_iterate_parallel(ObjectClosure* cl,
1926 uint worker_id,
1927 ShenandoahObjToScanQueueSet* queue_set) {
1928 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1929 assert(queue_set != nullptr, "task queue must not be null");
1930
1931 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1932 assert(q != nullptr, "object iterate queue must not be null");
1933
1934 ShenandoahMarkTask t;
1935 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1936
1937 // Work through the queue to traverse heap.
1938 // Steal when there is no task in queue.
1939 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1940 oop obj = t.obj();
1941 assert(oopDesc::is_oop(obj), "must be a valid oop");
1942 cl->do_object(obj);
1943 obj->oop_iterate(&oops);
1944 }
1945 assert(q->is_empty(), "should be empty");
1946 }
1947 };
1948
1949 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1950 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1951 }
1952
1953 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1954 void ShenandoahHeap::keep_alive(oop obj) {
1955 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1956 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1957 }
1958 }
1959
1960 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1961 for (size_t i = 0; i < num_regions(); i++) {
1962 ShenandoahHeapRegion* current = get_region(i);
1963 blk->heap_region_do(current);
1964 }
1965 }
1966
1967 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1968 private:
1969 ShenandoahHeap* const _heap;
1970 ShenandoahHeapRegionClosure* const _blk;
1971 size_t const _stride;
1972
1973 shenandoah_padding(0);
1974 volatile size_t _index;
1975 shenandoah_padding(1);
1976
1977 public:
1978 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
1979 WorkerTask("Shenandoah Parallel Region Operation"),
1980 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
1981
1982 void work(uint worker_id) {
1983 ShenandoahParallelWorkerSession worker_session(worker_id);
1984 size_t stride = _stride;
1985
1986 size_t max = _heap->num_regions();
1987 while (Atomic::load(&_index) < max) {
1988 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1989 size_t start = cur;
1990 size_t end = MIN2(cur + stride, max);
1991 if (start >= max) break;
1992
1993 for (size_t i = cur; i < end; i++) {
1994 ShenandoahHeapRegion* current = _heap->get_region(i);
1995 _blk->heap_region_do(current);
1996 }
1997 }
1998 }
1999 };
2000
2001 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2002 assert(blk->is_thread_safe(), "Only thread-safe closures here");
2003 const uint active_workers = workers()->active_workers();
2004 const size_t n_regions = num_regions();
2005 size_t stride = ShenandoahParallelRegionStride;
2006 if (stride == 0 && active_workers > 1) {
2007 // Automatically derive the stride to balance the work between threads
2008 // evenly. Do not try to split work if below the reasonable threshold.
2009 constexpr size_t threshold = 4096;
2010 stride = n_regions <= threshold ?
2011 threshold :
2012 (n_regions + active_workers - 1) / active_workers;
2013 }
2014
2015 if (n_regions > stride && active_workers > 1) {
2016 ShenandoahParallelHeapRegionTask task(blk, stride);
2017 workers()->run_task(&task);
2018 } else {
2019 heap_region_iterate(blk);
2020 }
2021 }
2022
2023 class ShenandoahRendezvousClosure : public HandshakeClosure {
2024 public:
2025 inline ShenandoahRendezvousClosure(const char* name) : HandshakeClosure(name) {}
2026 inline void do_thread(Thread* thread) {}
2027 };
2028
2029 void ShenandoahHeap::rendezvous_threads(const char* name) {
2030 ShenandoahRendezvousClosure cl(name);
2031 Handshake::execute(&cl);
2032 }
2033
2034 void ShenandoahHeap::recycle_trash() {
2035 free_set()->recycle_trash();
2036 }
2037
2038 void ShenandoahHeap::do_class_unloading() {
2039 _unloader.unload();
2040 if (mode()->is_generational()) {
2041 old_generation()->set_parsable(false);
2042 }
2043 }
2044
2045 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
2046 // Weak refs processing
2047 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2048 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2049 ShenandoahTimingsTracker t(phase);
2050 ShenandoahGCWorkerPhase worker_phase(phase);
2051 shenandoah_assert_generations_reconciled();
2052 gc_generation()->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2053 }
2054
2055 void ShenandoahHeap::prepare_update_heap_references() {
2056 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2057
2058 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2059 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2060 // for future GCLABs here.
2061 if (UseTLAB) {
2062 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2063 gclabs_retire(ResizeTLAB);
2064 }
2065
2066 _update_refs_iterator.reset();
2067 }
2068
2069 void ShenandoahHeap::propagate_gc_state_to_all_threads() {
2070 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2071 if (_gc_state_changed) {
2072 ShenandoahGCStatePropagator propagator(_gc_state.raw_value());
2073 Threads::threads_do(&propagator);
2074 _gc_state_changed = false;
2075 }
2076 }
2077
2078 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) {
2079 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2080 _gc_state.set_cond(mask, value);
2081 _gc_state_changed = true;
2082 }
2083
2084 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) {
2085 // Holding the thread lock here assures that any thread created after we change the gc
2086 // state will have the correct state. It also prevents attaching threads from seeing
2087 // an inconsistent state. See ShenandoahBarrierSet::on_thread_attach for reference. Established
2088 // threads will use their thread local copy of the gc state (changed by a handshake, or on a
2089 // safepoint).
2090 assert(Threads_lock->is_locked(), "Must hold thread lock for concurrent gc state change");
2091 _gc_state.set_cond(mask, value);
2092 }
2093
2094 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2095 uint mask;
2096 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2097 if (!in_progress && is_concurrent_old_mark_in_progress()) {
2098 assert(mode()->is_generational(), "Only generational GC has old marking");
2099 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2100 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2101 mask = YOUNG_MARKING;
2102 } else {
2103 mask = MARKING | YOUNG_MARKING;
2104 }
2105 set_gc_state_at_safepoint(mask, in_progress);
2106 manage_satb_barrier(in_progress);
2107 }
2108
2109 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2110 #ifdef ASSERT
2111 // has_forwarded_objects() iff UPDATE_REFS or EVACUATION
2112 bool has_forwarded = has_forwarded_objects();
2113 bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION);
2114 bool evacuating = _gc_state.is_set(EVACUATION);
2115 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2116 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2117 #endif
2118 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2119 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2120 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2121 set_gc_state_at_safepoint(OLD_MARKING, in_progress);
2122 } else {
2123 set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress);
2124 }
2125 manage_satb_barrier(in_progress);
2126 }
2127
2128 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2129 return old_generation()->is_preparing_for_mark();
2130 }
2131
2132 void ShenandoahHeap::manage_satb_barrier(bool active) {
2133 if (is_concurrent_mark_in_progress()) {
2134 // Ignore request to deactivate barrier while concurrent mark is in progress.
2135 // Do not attempt to re-activate the barrier if it is already active.
2136 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2137 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2138 }
2139 } else {
2140 // No concurrent marking is in progress so honor request to deactivate,
2141 // but only if the barrier is already active.
2142 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2143 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2144 }
2145 }
2146 }
2147
2148 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2149 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2150 set_gc_state_at_safepoint(EVACUATION, in_progress);
2151 }
2152
2153 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2154 if (in_progress) {
2155 _concurrent_strong_root_in_progress.set();
2156 } else {
2157 _concurrent_strong_root_in_progress.unset();
2158 }
2159 }
2160
2161 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2162 set_gc_state_at_safepoint(WEAK_ROOTS, cond);
2163 }
2164
2165 GCTracer* ShenandoahHeap::tracer() {
2166 return shenandoah_policy()->tracer();
2167 }
2168
2169 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2170 return _free_set->used();
2171 }
2172
2173 bool ShenandoahHeap::try_cancel_gc(GCCause::Cause cause) {
2174 const GCCause::Cause prev = _cancelled_gc.xchg(cause);
2175 return prev == GCCause::_no_gc || prev == GCCause::_shenandoah_concurrent_gc;
2176 }
2177
2178 void ShenandoahHeap::cancel_concurrent_mark() {
2179 if (mode()->is_generational()) {
2180 young_generation()->cancel_marking();
2181 old_generation()->cancel_marking();
2182 }
2183
2184 global_generation()->cancel_marking();
2185
2186 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2187 }
2188
2189 bool ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2190 if (try_cancel_gc(cause)) {
2191 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2192 log_info(gc,thread)("%s", msg.buffer());
2193 Events::log(Thread::current(), "%s", msg.buffer());
2194 _cancel_requested_time = os::elapsedTime();
2195 return true;
2196 }
2197 return false;
2198 }
2199
2200 uint ShenandoahHeap::max_workers() {
2201 return _max_workers;
2202 }
2203
2204 void ShenandoahHeap::stop() {
2205 // The shutdown sequence should be able to terminate when GC is running.
2206
2207 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2208 _shenandoah_policy->record_shutdown();
2209
2210 // Step 1. Stop reporting on gc thread cpu utilization
2211 mmu_tracker()->stop();
2212
2213 // Step 2. Wait until GC worker exits normally (this will cancel any ongoing GC).
2214 control_thread()->stop();
2215
2216 // Stop 4. Shutdown uncommit thread.
2217 if (_uncommit_thread != nullptr) {
2218 _uncommit_thread->stop();
2219 }
2220 }
2221
2222 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2223 if (!unload_classes()) return;
2224 ClassUnloadingContext ctx(_workers->active_workers(),
2225 true /* unregister_nmethods_during_purge */,
2226 false /* lock_nmethod_free_separately */);
2227
2228 // Unload classes and purge SystemDictionary.
2229 {
2230 ShenandoahPhaseTimings::Phase phase = full_gc ?
2231 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2232 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2233 ShenandoahIsAliveSelector is_alive;
2234 {
2235 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2236 ShenandoahGCPhase gc_phase(phase);
2237 ShenandoahGCWorkerPhase worker_phase(phase);
2238 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2239
2240 uint num_workers = _workers->active_workers();
2241 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
2242 _workers->run_task(&unlink_task);
2243 }
2244 // Release unloaded nmethods's memory.
2245 ClassUnloadingContext::context()->purge_and_free_nmethods();
2246 }
2247
2248 {
2249 ShenandoahGCPhase phase(full_gc ?
2250 ShenandoahPhaseTimings::full_gc_purge_cldg :
2251 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2252 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2253 }
2254 // Resize and verify metaspace
2255 MetaspaceGC::compute_new_size();
2256 DEBUG_ONLY(MetaspaceUtils::verify();)
2257 }
2258
2259 // Weak roots are either pre-evacuated (final mark) or updated (final update refs),
2260 // so they should not have forwarded oops.
2261 // However, we do need to "null" dead oops in the roots, if can not be done
2262 // in concurrent cycles.
2263 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2264 uint num_workers = _workers->active_workers();
2265 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2266 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2267 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2268 ShenandoahGCPhase phase(timing_phase);
2269 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2270 // Cleanup weak roots
2271 if (has_forwarded_objects()) {
2272 ShenandoahForwardedIsAliveClosure is_alive;
2273 ShenandoahNonConcUpdateRefsClosure keep_alive;
2274 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2275 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2276 _workers->run_task(&cleaning_task);
2277 } else {
2278 ShenandoahIsAliveClosure is_alive;
2279 #ifdef ASSERT
2280 ShenandoahAssertNotForwardedClosure verify_cl;
2281 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2282 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2283 #else
2284 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2285 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2286 #endif
2287 _workers->run_task(&cleaning_task);
2288 }
2289 }
2290
2291 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2292 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2293 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2294 ShenandoahGCPhase phase(full_gc ?
2295 ShenandoahPhaseTimings::full_gc_purge :
2296 ShenandoahPhaseTimings::degen_gc_purge);
2297 stw_weak_refs(full_gc);
2298 stw_process_weak_roots(full_gc);
2299 stw_unload_classes(full_gc);
2300 }
2301
2302 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2303 set_gc_state_at_safepoint(HAS_FORWARDED, cond);
2304 }
2305
2306 void ShenandoahHeap::set_unload_classes(bool uc) {
2307 _unload_classes.set_cond(uc);
2308 }
2309
2310 bool ShenandoahHeap::unload_classes() const {
2311 return _unload_classes.is_set();
2312 }
2313
2314 address ShenandoahHeap::in_cset_fast_test_addr() {
2315 ShenandoahHeap* heap = ShenandoahHeap::heap();
2316 assert(heap->collection_set() != nullptr, "Sanity");
2317 return (address) heap->collection_set()->biased_map_address();
2318 }
2319
2320 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2321 if (mode()->is_generational()) {
2322 young_generation()->reset_bytes_allocated_since_gc_start();
2323 old_generation()->reset_bytes_allocated_since_gc_start();
2324 }
2325
2326 global_generation()->reset_bytes_allocated_since_gc_start();
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() {
2388 for (size_t i = 0; i < num_regions(); i++) {
2389 ShenandoahHeapRegion* r = get_region(i);
2390 shenandoah_assert_generations_reconciled();
2391 if (gc_generation()->contains(r)) {
2392 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2393 "Region %zu pinning status is inconsistent", i);
2394 }
2395 }
2396 }
2397 #endif
2398
2399 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2400 return _gc_timer;
2401 }
2402
2403 void ShenandoahHeap::prepare_concurrent_roots() {
2404 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2405 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2406 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2407 set_concurrent_weak_root_in_progress(true);
2408 if (unload_classes()) {
2409 _unloader.prepare();
2410 }
2411 }
2412
2413 void ShenandoahHeap::finish_concurrent_roots() {
2414 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2415 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2416 if (unload_classes()) {
2417 _unloader.finish();
2418 }
2419 }
2420
2421 #ifdef ASSERT
2422 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2423 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2424
2425 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2426 // Use ParallelGCThreads inside safepoints
2427 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2428 ParallelGCThreads, nworkers);
2429 } else {
2430 // Use ConcGCThreads outside safepoints
2431 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2432 ConcGCThreads, nworkers);
2433 }
2434 }
2435 #endif
2436
2437 ShenandoahVerifier* ShenandoahHeap::verifier() {
2438 guarantee(ShenandoahVerify, "Should be enabled");
2439 assert (_verifier != nullptr, "sanity");
2440 return _verifier;
2441 }
2442
2443 template<bool CONCURRENT>
2444 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2445 private:
2446 ShenandoahHeap* _heap;
2447 ShenandoahRegionIterator* _regions;
2448 public:
2449 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2450 WorkerTask("Shenandoah Update References"),
2451 _heap(ShenandoahHeap::heap()),
2452 _regions(regions) {
2453 }
2454
2455 void work(uint worker_id) {
2456 if (CONCURRENT) {
2457 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2458 ShenandoahSuspendibleThreadSetJoiner stsj;
2459 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2460 } else {
2461 ShenandoahParallelWorkerSession worker_session(worker_id);
2462 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2463 }
2464 }
2465
2466 private:
2467 template<class T>
2468 void do_work(uint worker_id) {
2469 if (CONCURRENT && (worker_id == 0)) {
2470 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2471 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2472 size_t cset_regions = _heap->collection_set()->count();
2473
2474 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2475 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2476 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2477 // next GC cycle.
2478 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2479 }
2480 // If !CONCURRENT, there's no value in expanding Mutator free set
2481 T cl;
2482 ShenandoahHeapRegion* r = _regions->next();
2483 while (r != nullptr) {
2484 HeapWord* update_watermark = r->get_update_watermark();
2485 assert (update_watermark >= r->bottom(), "sanity");
2486 if (r->is_active() && !r->is_cset()) {
2487 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2488 if (ShenandoahPacing) {
2489 _heap->pacer()->report_update_refs(pointer_delta(update_watermark, r->bottom()));
2490 }
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(bool concurrent) {
2501 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2502
2503 if (concurrent) {
2504 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2505 workers()->run_task(&task);
2506 } else {
2507 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2508 workers()->run_task(&task);
2509 }
2510 }
2511
2512 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2513 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2514 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2515
2516 {
2517 ShenandoahGCPhase phase(concurrent ?
2518 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2519 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2520
2521 final_update_refs_update_region_states();
2522
2523 assert_pinned_region_status();
2524 }
2525
2526 {
2527 ShenandoahGCPhase phase(concurrent ?
2528 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2529 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2530 trash_cset_regions();
2531 }
2532 }
2533
2534 void ShenandoahHeap::final_update_refs_update_region_states() {
2535 ShenandoahSynchronizePinnedRegionStates cl;
2536 parallel_heap_region_iterate(&cl);
2537 }
2538
2539 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2540 ShenandoahGCPhase phase(concurrent ?
2541 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2542 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2543 ShenandoahHeapLocker locker(lock());
2544 size_t young_cset_regions, old_cset_regions;
2545 size_t first_old_region, last_old_region, old_region_count;
2546 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count);
2547 // If there are no old regions, first_old_region will be greater than last_old_region
2548 assert((first_old_region > last_old_region) ||
2549 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2550 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2551 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu",
2552 old_region_count, first_old_region, last_old_region);
2553
2554 if (mode()->is_generational()) {
2555 #ifdef ASSERT
2556 if (ShenandoahVerify) {
2557 verifier()->verify_before_rebuilding_free_set();
2558 }
2559 #endif
2560
2561 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2562 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2563 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2564 size_t allocation_runway = gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions);
2565 gen_heap->compute_old_generation_balance(allocation_runway, old_cset_regions);
2566
2567 // Total old_available may have been expanded to hold anticipated promotions. We trigger if the fragmented available
2568 // memory represents more than 16 regions worth of data. Note that fragmentation may increase when we promote regular
2569 // regions in place when many of these regular regions have an abundant amount of available memory within them. Fragmentation
2570 // will decrease as promote-by-copy consumes the available memory within these partially consumed regions.
2571 //
2572 // We consider old-gen to have excessive fragmentation if more than 12.5% of old-gen is free memory that resides
2573 // within partially consumed regions of memory.
2574 }
2575 // Rebuild free set based on adjusted generation sizes.
2576 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, old_region_count);
2577
2578 if (mode()->is_generational()) {
2579 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2580 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2581 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2582 }
2583 }
2584
2585 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2586 print_on(st);
2587 st->cr();
2588 print_heap_regions_on(st);
2589 }
2590
2591 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2592 size_t slice = r->index() / _bitmap_regions_per_slice;
2593
2594 size_t regions_from = _bitmap_regions_per_slice * slice;
2595 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2596 for (size_t g = regions_from; g < regions_to; g++) {
2597 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2598 if (skip_self && g == r->index()) continue;
2599 if (get_region(g)->is_committed()) {
2600 return true;
2601 }
2602 }
2603 return false;
2604 }
2605
2606 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2607 shenandoah_assert_heaplocked();
2608
2609 // Bitmaps in special regions do not need commits
2610 if (_bitmap_region_special) {
2611 return true;
2612 }
2613
2614 if (is_bitmap_slice_committed(r, true)) {
2615 // Some other region from the group is already committed, meaning the bitmap
2616 // slice is already committed, we exit right away.
2617 return true;
2618 }
2619
2620 // Commit the bitmap slice:
2621 size_t slice = r->index() / _bitmap_regions_per_slice;
2622 size_t off = _bitmap_bytes_per_slice * slice;
2623 size_t len = _bitmap_bytes_per_slice;
2624 char* start = (char*) _bitmap_region.start() + off;
2625
2626 if (!os::commit_memory(start, len, false)) {
2627 return false;
2628 }
2629
2630 if (AlwaysPreTouch) {
2631 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2632 }
2633
2634 return true;
2635 }
2636
2637 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2638 shenandoah_assert_heaplocked();
2639
2640 // Bitmaps in special regions do not need uncommits
2641 if (_bitmap_region_special) {
2642 return true;
2643 }
2644
2645 if (is_bitmap_slice_committed(r, true)) {
2646 // Some other region from the group is still committed, meaning the bitmap
2647 // slice should stay committed, exit right away.
2648 return true;
2649 }
2650
2651 // Uncommit the bitmap slice:
2652 size_t slice = r->index() / _bitmap_regions_per_slice;
2653 size_t off = _bitmap_bytes_per_slice * slice;
2654 size_t len = _bitmap_bytes_per_slice;
2655 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2656 return false;
2657 }
2658 return true;
2659 }
2660
2661 void ShenandoahHeap::forbid_uncommit() {
2662 if (_uncommit_thread != nullptr) {
2663 _uncommit_thread->forbid_uncommit();
2664 }
2665 }
2666
2667 void ShenandoahHeap::allow_uncommit() {
2668 if (_uncommit_thread != nullptr) {
2669 _uncommit_thread->allow_uncommit();
2670 }
2671 }
2672
2673 #ifdef ASSERT
2674 bool ShenandoahHeap::is_uncommit_in_progress() {
2675 if (_uncommit_thread != nullptr) {
2676 return _uncommit_thread->is_uncommit_in_progress();
2677 }
2678 return false;
2679 }
2680 #endif
2681
2682 void ShenandoahHeap::safepoint_synchronize_begin() {
2683 StackWatermarkSet::safepoint_synchronize_begin();
2684 SuspendibleThreadSet::synchronize();
2685 }
2686
2687 void ShenandoahHeap::safepoint_synchronize_end() {
2688 SuspendibleThreadSet::desynchronize();
2689 }
2690
2691 void ShenandoahHeap::try_inject_alloc_failure() {
2692 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2693 _inject_alloc_failure.set();
2694 os::naked_short_sleep(1);
2695 if (cancelled_gc()) {
2696 log_info(gc)("Allocation failure was successfully injected");
2697 }
2698 }
2699 }
2700
2701 bool ShenandoahHeap::should_inject_alloc_failure() {
2702 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2703 }
2704
2705 void ShenandoahHeap::initialize_serviceability() {
2706 _memory_pool = new ShenandoahMemoryPool(this);
2707 _cycle_memory_manager.add_pool(_memory_pool);
2708 _stw_memory_manager.add_pool(_memory_pool);
2709 }
2710
2711 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2712 GrowableArray<GCMemoryManager*> memory_managers(2);
2713 memory_managers.append(&_cycle_memory_manager);
2714 memory_managers.append(&_stw_memory_manager);
2715 return memory_managers;
2716 }
2717
2718 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2719 GrowableArray<MemoryPool*> memory_pools(1);
2720 memory_pools.append(_memory_pool);
2721 return memory_pools;
2722 }
2723
2724 MemoryUsage ShenandoahHeap::memory_usage() {
2725 return MemoryUsage(_initial_size, used(), committed(), max_capacity());
2726 }
2727
2728 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2729 _heap(ShenandoahHeap::heap()),
2730 _index(0) {}
2731
2732 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2733 _heap(heap),
2734 _index(0) {}
2735
2736 void ShenandoahRegionIterator::reset() {
2737 _index = 0;
2738 }
2739
2740 bool ShenandoahRegionIterator::has_next() const {
2741 return _index < _heap->num_regions();
2742 }
2743
2744 char ShenandoahHeap::gc_state() const {
2745 return _gc_state.raw_value();
2746 }
2747
2748 bool ShenandoahHeap::is_gc_state(GCState state) const {
2749 // If the global gc state has been changed, but hasn't yet been propagated to all threads, then
2750 // the global gc state is the correct value. Once the gc state has been synchronized with all threads,
2751 // _gc_state_changed will be toggled to false and we need to use the thread local state.
2752 return _gc_state_changed ? _gc_state.is_set(state) : ShenandoahThreadLocalData::is_gc_state(state);
2753 }
2754
2755
2756 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2757 #ifdef ASSERT
2758 assert(_liveness_cache != nullptr, "sanity");
2759 assert(worker_id < _max_workers, "sanity");
2760 for (uint i = 0; i < num_regions(); i++) {
2761 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2762 }
2763 #endif
2764 return _liveness_cache[worker_id];
2765 }
2766
2767 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2768 assert(worker_id < _max_workers, "sanity");
2769 assert(_liveness_cache != nullptr, "sanity");
2770 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2771 for (uint i = 0; i < num_regions(); i++) {
2772 ShenandoahLiveData live = ld[i];
2773 if (live > 0) {
2774 ShenandoahHeapRegion* r = get_region(i);
2775 r->increase_live_data_gc_words(live);
2776 ld[i] = 0;
2777 }
2778 }
2779 }
2780
2781 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2782 if (is_idle()) return false;
2783
2784 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2785 // marking phase.
2786 if (is_concurrent_mark_in_progress() &&
2787 !marking_context()->allocated_after_mark_start(obj)) {
2788 return true;
2789 }
2790
2791 // Can not guarantee obj is deeply good.
2792 if (has_forwarded_objects()) {
2793 return true;
2794 }
2795
2796 return false;
2797 }
2798
2799 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2800 #if INCLUDE_CDS_JAVA_HEAP
2801 // CDS wants a continuous memory range to load a bunch of objects.
2802 // This effectively bypasses normal allocation paths, and requires
2803 // a bit of massaging to unbreak GC invariants.
2804
2805 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
2806
2807 // Easy case: a single regular region, no further adjustments needed.
2808 if (!ShenandoahHeapRegion::requires_humongous(size)) {
2809 return allocate_memory(req);
2810 }
2811
2812 // Hard case: the requested size would cause a humongous allocation.
2813 // We need to make sure it looks like regular allocation to the rest of GC.
2814
2815 // CDS code would guarantee no objects straddle multiple regions, as long as
2816 // regions are as large as MIN_GC_REGION_ALIGNMENT. It is impractical at this
2817 // point to deal with case when Shenandoah runs with smaller regions.
2818 // TODO: This check can be dropped once MIN_GC_REGION_ALIGNMENT agrees more with Shenandoah.
2819 if (ShenandoahHeapRegion::region_size_bytes() < ArchiveHeapWriter::MIN_GC_REGION_ALIGNMENT) {
2820 return nullptr;
2821 }
2822
2823 HeapWord* mem = allocate_memory(req);
2824 size_t start_idx = heap_region_index_containing(mem);
2825 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
2826
2827 // Flip humongous -> regular.
2828 {
2829 ShenandoahHeapLocker locker(lock(), false);
2830 for (size_t c = start_idx; c < start_idx + num_regions; c++) {
2831 get_region(c)->make_regular_bypass();
2832 }
2833 }
2834
2835 return mem;
2836 #else
2837 assert(false, "Archive heap loader should not be available, should not be here");
2838 return nullptr;
2839 #endif // INCLUDE_CDS_JAVA_HEAP
2840 }
2841
2842 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2843 // Nothing to do here, except checking that heap looks fine.
2844 #ifdef ASSERT
2845 HeapWord* start = archive_space.start();
2846 HeapWord* end = archive_space.end();
2847
2848 // No unclaimed space between the objects.
2849 // Objects are properly allocated in correct regions.
2850 HeapWord* cur = start;
2851 while (cur < end) {
2852 oop oop = cast_to_oop(cur);
2853 shenandoah_assert_in_correct_region(nullptr, oop);
2854 cur += oop->size();
2855 }
2856
2857 // No unclaimed tail at the end of archive space.
2858 assert(cur == end,
2859 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2860 p2i(cur), p2i(end));
2861
2862 // Region bounds are good.
2863 ShenandoahHeapRegion* begin_reg = heap_region_containing(start);
2864 ShenandoahHeapRegion* end_reg = heap_region_containing(end);
2865 assert(begin_reg->is_regular(), "Must be");
2866 assert(end_reg->is_regular(), "Must be");
2867 assert(begin_reg->bottom() == start,
2868 "Must agree: archive-space-start: " PTR_FORMAT ", begin-region-bottom: " PTR_FORMAT,
2869 p2i(start), p2i(begin_reg->bottom()));
2870 assert(end_reg->top() == end,
2871 "Must agree: archive-space-end: " PTR_FORMAT ", end-region-top: " PTR_FORMAT,
2872 p2i(end), p2i(end_reg->top()));
2873 #endif
2874 }
2875
2876 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2877 if (!mode()->is_generational()) {
2878 return global_generation();
2879 } else if (affiliation == YOUNG_GENERATION) {
2880 return young_generation();
2881 } else if (affiliation == OLD_GENERATION) {
2882 return old_generation();
2883 }
2884
2885 ShouldNotReachHere();
2886 return nullptr;
2887 }
2888
2889 void ShenandoahHeap::log_heap_status(const char* msg) const {
2890 if (mode()->is_generational()) {
2891 young_generation()->log_status(msg);
2892 old_generation()->log_status(msg);
2893 } else {
2894 global_generation()->log_status(msg);
2895 }
2896 }