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 #include "gc/shared/classUnloadingContext.hpp"
31 #include "gc/shared/fullGCForwarding.hpp"
32 #include "gc/shared/gcArguments.hpp"
33 #include "gc/shared/gcTimer.hpp"
34 #include "gc/shared/gcTraceTime.inline.hpp"
35 #include "gc/shared/locationPrinter.inline.hpp"
36 #include "gc/shared/memAllocator.hpp"
37 #include "gc/shared/plab.hpp"
38 #include "gc/shared/tlab_globals.hpp"
39 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
40 #include "gc/shenandoah/heuristics/shenandoahYoungHeuristics.hpp"
41 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
42 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
43 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
44 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
45 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
46 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
47 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
48 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
49 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
50 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
51 #include "gc/shenandoah/shenandoahControlThread.hpp"
52 #include "gc/shenandoah/shenandoahFreeSet.hpp"
53 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp"
54 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
55 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
56 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
57 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
58 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
59 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
60 #include "gc/shenandoah/shenandoahInitLogger.hpp"
61 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
62 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
63 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
64 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
65 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
66 #include "gc/shenandoah/shenandoahPadding.hpp"
67 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
68 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
69 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
70 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
71 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
72 #include "gc/shenandoah/shenandoahSTWMark.hpp"
73 #include "gc/shenandoah/shenandoahUncommitThread.hpp"
74 #include "gc/shenandoah/shenandoahUtils.hpp"
75 #include "gc/shenandoah/shenandoahVerifier.hpp"
76 #include "gc/shenandoah/shenandoahVMOperations.hpp"
77 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
78 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
79 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
80 #include "memory/allocation.hpp"
81 #include "memory/classLoaderMetaspace.hpp"
82 #include "memory/memoryReserver.hpp"
83 #include "memory/metaspaceUtils.hpp"
84 #include "memory/universe.hpp"
85 #include "nmt/mallocTracker.hpp"
86 #include "nmt/memTracker.hpp"
87 #include "oops/compressedOops.inline.hpp"
88 #include "prims/jvmtiTagMap.hpp"
89 #include "runtime/atomic.hpp"
90 #include "runtime/globals.hpp"
91 #include "runtime/interfaceSupport.inline.hpp"
92 #include "runtime/java.hpp"
93 #include "runtime/orderAccess.hpp"
94 #include "runtime/safepointMechanism.hpp"
95 #include "runtime/stackWatermarkSet.hpp"
96 #include "runtime/threads.hpp"
97 #include "runtime/vmThread.hpp"
98 #include "utilities/events.hpp"
99 #include "utilities/globalDefinitions.hpp"
100 #include "utilities/powerOfTwo.hpp"
101 #if INCLUDE_JFR
102 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
103 #endif
104
105 class ShenandoahPretouchHeapTask : public WorkerTask {
106 private:
107 ShenandoahRegionIterator _regions;
108 const size_t _page_size;
109 public:
110 ShenandoahPretouchHeapTask(size_t page_size) :
111 WorkerTask("Shenandoah Pretouch Heap"),
112 _page_size(page_size) {}
113
114 virtual void work(uint worker_id) {
115 ShenandoahHeapRegion* r = _regions.next();
116 while (r != nullptr) {
117 if (r->is_committed()) {
118 os::pretouch_memory(r->bottom(), r->end(), _page_size);
119 }
120 r = _regions.next();
121 }
122 }
123 };
124
125 class ShenandoahPretouchBitmapTask : public WorkerTask {
126 private:
127 ShenandoahRegionIterator _regions;
128 char* _bitmap_base;
129 const size_t _bitmap_size;
130 const size_t _page_size;
131 public:
132 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
133 WorkerTask("Shenandoah Pretouch Bitmap"),
134 _bitmap_base(bitmap_base),
135 _bitmap_size(bitmap_size),
136 _page_size(page_size) {}
137
138 virtual void work(uint worker_id) {
139 ShenandoahHeapRegion* r = _regions.next();
140 while (r != nullptr) {
141 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
142 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
143 assert (end <= _bitmap_size, "end is sane: %zu < %zu", end, _bitmap_size);
144
145 if (r->is_committed()) {
146 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
147 }
148
149 r = _regions.next();
150 }
151 }
152 };
153
154 static ReservedSpace reserve(size_t size, size_t preferred_page_size) {
155 // When a page size is given we don't want to mix large
156 // and normal pages. If the size is not a multiple of the
157 // page size it will be aligned up to achieve this.
158 size_t alignment = os::vm_allocation_granularity();
159 if (preferred_page_size != os::vm_page_size()) {
160 alignment = MAX2(preferred_page_size, alignment);
161 size = align_up(size, alignment);
162 }
163
164 const ReservedSpace reserved = MemoryReserver::reserve(size, alignment, preferred_page_size, mtGC);
165 if (!reserved.is_reserved()) {
166 vm_exit_during_initialization("Could not reserve space");
167 }
168 return reserved;
169 }
170
171 jint ShenandoahHeap::initialize() {
172 //
173 // Figure out heap sizing
174 //
175
176 size_t init_byte_size = InitialHeapSize;
177 size_t min_byte_size = MinHeapSize;
178 size_t max_byte_size = MaxHeapSize;
179 size_t heap_alignment = HeapAlignment;
180
181 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
182
183 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
184 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
185
186 _num_regions = ShenandoahHeapRegion::region_count();
187 assert(_num_regions == (max_byte_size / reg_size_bytes),
188 "Regions should cover entire heap exactly: %zu != %zu/%zu",
189 _num_regions, max_byte_size, reg_size_bytes);
190
191 size_t num_committed_regions = init_byte_size / reg_size_bytes;
192 num_committed_regions = MIN2(num_committed_regions, _num_regions);
193 assert(num_committed_regions <= _num_regions, "sanity");
194 _initial_size = num_committed_regions * reg_size_bytes;
195
196 size_t num_min_regions = min_byte_size / reg_size_bytes;
197 num_min_regions = MIN2(num_min_regions, _num_regions);
198 assert(num_min_regions <= _num_regions, "sanity");
199 _minimum_size = num_min_regions * reg_size_bytes;
200
201 // Default to max heap size.
202 _soft_max_size = _num_regions * reg_size_bytes;
203
204 _committed = _initial_size;
205
206 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
207 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
208 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
209
210 //
211 // Reserve and commit memory for heap
212 //
213
214 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
215 initialize_reserved_region(heap_rs);
216 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
217 _heap_region_special = heap_rs.special();
218
219 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
220 "Misaligned heap: " PTR_FORMAT, p2i(base()));
221 os::trace_page_sizes_for_requested_size("Heap",
222 max_byte_size, heap_alignment,
223 heap_rs.base(),
224 heap_rs.size(), heap_rs.page_size());
225
226 #if SHENANDOAH_OPTIMIZED_MARKTASK
227 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
228 // Fail if we ever attempt to address more than we can.
229 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
230 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
231 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
232 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
233 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
234 vm_exit_during_initialization("Fatal Error", buf);
235 }
236 #endif
237
238 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
239 if (!_heap_region_special) {
240 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
241 "Cannot commit heap memory");
242 }
243
244 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
245
246 // Now we know the number of regions and heap sizes, initialize the heuristics.
247 initialize_heuristics();
248
249 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
250
251 //
252 // Worker threads must be initialized after the barrier is configured
253 //
254 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
255 if (_workers == nullptr) {
256 vm_exit_during_initialization("Failed necessary allocation.");
257 } else {
258 _workers->initialize_workers();
259 }
260
261 if (ParallelGCThreads > 1) {
262 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
263 _safepoint_workers->initialize_workers();
264 }
265
266 //
267 // Reserve and commit memory for bitmap(s)
268 //
269
270 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
271 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
272
273 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
274
275 guarantee(bitmap_bytes_per_region != 0,
276 "Bitmap bytes per region should not be zero");
277 guarantee(is_power_of_2(bitmap_bytes_per_region),
278 "Bitmap bytes per region should be power of two: %zu", bitmap_bytes_per_region);
279
280 if (bitmap_page_size > bitmap_bytes_per_region) {
281 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
282 _bitmap_bytes_per_slice = bitmap_page_size;
283 } else {
284 _bitmap_regions_per_slice = 1;
285 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
286 }
287
288 guarantee(_bitmap_regions_per_slice >= 1,
289 "Should have at least one region per slice: %zu",
290 _bitmap_regions_per_slice);
291
292 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
293 "Bitmap slices should be page-granular: bps = %zu, page size = %zu",
294 _bitmap_bytes_per_slice, bitmap_page_size);
295
296 ReservedSpace bitmap = reserve(_bitmap_size, bitmap_page_size);
297 os::trace_page_sizes_for_requested_size("Mark Bitmap",
298 bitmap_size_orig, bitmap_page_size,
299 bitmap.base(),
300 bitmap.size(), bitmap.page_size());
301 MemTracker::record_virtual_memory_tag(bitmap, mtGC);
302 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
303 _bitmap_region_special = bitmap.special();
304
305 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
306 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
307 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
308 if (!_bitmap_region_special) {
309 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
310 "Cannot commit bitmap memory");
311 }
312
313 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
314
315 if (ShenandoahVerify) {
316 ReservedSpace verify_bitmap = reserve(_bitmap_size, bitmap_page_size);
317 os::trace_page_sizes_for_requested_size("Verify Bitmap",
318 bitmap_size_orig, bitmap_page_size,
319 verify_bitmap.base(),
320 verify_bitmap.size(), verify_bitmap.page_size());
321 if (!verify_bitmap.special()) {
322 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
323 "Cannot commit verification bitmap memory");
324 }
325 MemTracker::record_virtual_memory_tag(verify_bitmap, mtGC);
326 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
327 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
328 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
329 }
330
331 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
332 size_t aux_bitmap_page_size = bitmap_page_size;
333
334 ReservedSpace aux_bitmap = reserve(_bitmap_size, aux_bitmap_page_size);
335 os::trace_page_sizes_for_requested_size("Aux Bitmap",
336 bitmap_size_orig, aux_bitmap_page_size,
337 aux_bitmap.base(),
338 aux_bitmap.size(), aux_bitmap.page_size());
339 MemTracker::record_virtual_memory_tag(aux_bitmap, mtGC);
340 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
341 _aux_bitmap_region_special = aux_bitmap.special();
342 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
343
344 //
345 // Create regions and region sets
346 //
347 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
348 size_t region_storage_size_orig = region_align * _num_regions;
349 size_t region_storage_size = align_up(region_storage_size_orig,
350 MAX2(region_page_size, os::vm_allocation_granularity()));
351
352 ReservedSpace region_storage = reserve(region_storage_size, region_page_size);
353 os::trace_page_sizes_for_requested_size("Region Storage",
354 region_storage_size_orig, region_page_size,
355 region_storage.base(),
356 region_storage.size(), region_storage.page_size());
357 MemTracker::record_virtual_memory_tag(region_storage, mtGC);
358 if (!region_storage.special()) {
359 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
360 "Cannot commit region memory");
361 }
362
363 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
364 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
365 // If not successful, bite a bullet and allocate at whatever address.
366 {
367 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
368 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
369 const size_t cset_page_size = os::vm_page_size();
370
371 uintptr_t min = round_up_power_of_2(cset_align);
372 uintptr_t max = (1u << 30u);
373 ReservedSpace cset_rs;
374
375 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
376 char* req_addr = (char*)addr;
377 assert(is_aligned(req_addr, cset_align), "Should be aligned");
378 cset_rs = MemoryReserver::reserve(req_addr, cset_size, cset_align, cset_page_size, mtGC);
379 if (cset_rs.is_reserved()) {
380 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
381 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
382 break;
383 }
384 }
385
386 if (_collection_set == nullptr) {
387 cset_rs = MemoryReserver::reserve(cset_size, cset_align, os::vm_page_size(), mtGC);
388 if (!cset_rs.is_reserved()) {
389 vm_exit_during_initialization("Cannot reserve memory for collection set");
390 }
391
392 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
393 }
394 os::trace_page_sizes_for_requested_size("Collection Set",
395 cset_size, cset_page_size,
396 cset_rs.base(),
397 cset_rs.size(), cset_rs.page_size());
398 }
399
400 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
401 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
402 _free_set = new ShenandoahFreeSet(this, _num_regions);
403
404 {
405 ShenandoahHeapLocker locker(lock());
406
407 for (size_t i = 0; i < _num_regions; i++) {
408 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
409 bool is_committed = i < num_committed_regions;
410 void* loc = region_storage.base() + i * region_align;
411
412 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
413 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
414
415 _marking_context->initialize_top_at_mark_start(r);
416 _regions[i] = r;
417 assert(!collection_set()->is_in(i), "New region should not be in collection set");
418
419 _affiliations[i] = ShenandoahAffiliation::FREE;
420 }
421
422 size_t young_cset_regions, old_cset_regions;
423
424 // We are initializing free set. We ignore cset region tallies.
425 size_t first_old, last_old, num_old;
426 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old, last_old, num_old);
427 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, num_old);
428 }
429
430 if (AlwaysPreTouch) {
431 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
432 // before initialize() below zeroes it with initializing thread. For any given region,
433 // we touch the region and the corresponding bitmaps from the same thread.
434 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
435
436 _pretouch_heap_page_size = heap_page_size;
437 _pretouch_bitmap_page_size = bitmap_page_size;
438
439 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
440 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
441
442 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
443 _workers->run_task(&bcl);
444
445 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
446 _workers->run_task(&hcl);
447 }
448
449 //
450 // Initialize the rest of GC subsystems
451 //
452
453 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
454 for (uint worker = 0; worker < _max_workers; worker++) {
455 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
456 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
457 }
458
459 // There should probably be Shenandoah-specific options for these,
460 // just as there are G1-specific options.
461 {
462 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
463 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
464 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
465 }
466
467 _monitoring_support = new ShenandoahMonitoringSupport(this);
468 _phase_timings = new ShenandoahPhaseTimings(max_workers());
469 ShenandoahCodeRoots::initialize();
470
471 if (ShenandoahPacing) {
472 _pacer = new ShenandoahPacer(this);
473 _pacer->setup_for_idle();
474 }
475
476 initialize_controller();
477
478 if (ShenandoahUncommit) {
479 _uncommit_thread = new ShenandoahUncommitThread(this);
480 }
481
482 print_init_logger();
483
484 FullGCForwarding::initialize(_heap_region);
485
486 return JNI_OK;
487 }
488
489 void ShenandoahHeap::initialize_controller() {
490 _control_thread = new ShenandoahControlThread();
491 }
492
493 void ShenandoahHeap::print_init_logger() const {
494 ShenandoahInitLogger::print();
495 }
496
497 void ShenandoahHeap::initialize_mode() {
498 if (ShenandoahGCMode != nullptr) {
499 if (strcmp(ShenandoahGCMode, "satb") == 0) {
500 _gc_mode = new ShenandoahSATBMode();
501 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
502 _gc_mode = new ShenandoahPassiveMode();
503 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
504 _gc_mode = new ShenandoahGenerationalMode();
505 } else {
506 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
507 }
508 } else {
509 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
510 }
511 _gc_mode->initialize_flags();
512 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
513 vm_exit_during_initialization(
514 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
515 _gc_mode->name()));
516 }
517 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
518 vm_exit_during_initialization(
519 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
520 _gc_mode->name()));
521 }
522 }
523
524 void ShenandoahHeap::initialize_heuristics() {
525 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers(), max_capacity(), max_capacity());
526 _global_generation->initialize_heuristics(mode());
527 }
528
529 #ifdef _MSC_VER
530 #pragma warning( push )
531 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
532 #endif
533
534 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
535 CollectedHeap(),
536 _gc_generation(nullptr),
537 _active_generation(nullptr),
538 _initial_size(0),
539 _committed(0),
540 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
541 _workers(nullptr),
542 _safepoint_workers(nullptr),
543 _heap_region_special(false),
544 _num_regions(0),
545 _regions(nullptr),
546 _affiliations(nullptr),
547 _gc_state_changed(false),
548 _gc_no_progress_count(0),
549 _cancel_requested_time(0),
550 _update_refs_iterator(this),
551 _global_generation(nullptr),
552 _control_thread(nullptr),
553 _uncommit_thread(nullptr),
554 _young_generation(nullptr),
555 _old_generation(nullptr),
556 _shenandoah_policy(policy),
557 _gc_mode(nullptr),
558 _free_set(nullptr),
559 _pacer(nullptr),
560 _verifier(nullptr),
561 _phase_timings(nullptr),
562 _monitoring_support(nullptr),
563 _memory_pool(nullptr),
564 _stw_memory_manager("Shenandoah Pauses"),
565 _cycle_memory_manager("Shenandoah Cycles"),
566 _gc_timer(new ConcurrentGCTimer()),
567 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
568 _marking_context(nullptr),
569 _bitmap_size(0),
570 _bitmap_regions_per_slice(0),
571 _bitmap_bytes_per_slice(0),
572 _bitmap_region_special(false),
573 _aux_bitmap_region_special(false),
574 _liveness_cache(nullptr),
575 _collection_set(nullptr)
576 {
577 // Initialize GC mode early, many subsequent initialization procedures depend on it
578 initialize_mode();
579 _cancelled_gc.set(GCCause::_no_gc);
580 }
581
582 #ifdef _MSC_VER
583 #pragma warning( pop )
584 #endif
585
586 void ShenandoahHeap::print_heap_on(outputStream* st) const {
587 st->print_cr("Shenandoah Heap");
588 st->print_cr(" %zu%s max, %zu%s soft max, %zu%s committed, %zu%s used",
589 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
590 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
591 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
592 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
593 st->print_cr(" %zu x %zu %s regions",
594 num_regions(),
595 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
596 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
597
598 st->print("Status: ");
599 if (has_forwarded_objects()) st->print("has forwarded objects, ");
600 if (!mode()->is_generational()) {
601 if (is_concurrent_mark_in_progress()) st->print("marking,");
602 } else {
603 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
604 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
605 }
606 if (is_evacuation_in_progress()) st->print("evacuating, ");
607 if (is_update_refs_in_progress()) st->print("updating refs, ");
608 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
609 if (is_full_gc_in_progress()) st->print("full gc, ");
610 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
611 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
612 if (is_concurrent_strong_root_in_progress() &&
613 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
614
615 if (cancelled_gc()) {
616 st->print("cancelled");
617 } else {
618 st->print("not cancelled");
619 }
620 st->cr();
621
622 st->print_cr("Reserved region:");
623 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
624 p2i(reserved_region().start()),
625 p2i(reserved_region().end()));
626
627 ShenandoahCollectionSet* cset = collection_set();
628 st->print_cr("Collection set:");
629 if (cset != nullptr) {
630 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
631 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
632 } else {
633 st->print_cr(" (null)");
634 }
635
636 st->cr();
637
638 if (Verbose) {
639 st->cr();
640 print_heap_regions_on(st);
641 }
642 }
643
644 void ShenandoahHeap::print_gc_on(outputStream* st) const {
645 print_heap_regions_on(st);
646 }
647
648 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
649 public:
650 void do_thread(Thread* thread) {
651 assert(thread != nullptr, "Sanity");
652 ShenandoahThreadLocalData::initialize_gclab(thread);
653 }
654 };
655
656 void ShenandoahHeap::post_initialize() {
657 CollectedHeap::post_initialize();
658
659 // Schedule periodic task to report on gc thread CPU utilization
660 _mmu_tracker.initialize();
661
662 MutexLocker ml(Threads_lock);
663
664 ShenandoahInitWorkerGCLABClosure init_gclabs;
665 _workers->threads_do(&init_gclabs);
666
667 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
668 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
669 _workers->set_initialize_gclab();
670
671 // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump
672 // during a concurrent evacuation phase.
673 if (_safepoint_workers != nullptr) {
674 _safepoint_workers->threads_do(&init_gclabs);
675 _safepoint_workers->set_initialize_gclab();
676 }
677
678 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
679 }
680
681 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
682 return _global_generation->heuristics();
683 }
684
685 size_t ShenandoahHeap::used() const {
686 return global_generation()->used();
687 }
688
689 size_t ShenandoahHeap::committed() const {
690 return Atomic::load(&_committed);
691 }
692
693 void ShenandoahHeap::increase_committed(size_t bytes) {
694 shenandoah_assert_heaplocked_or_safepoint();
695 _committed += bytes;
696 }
697
698 void ShenandoahHeap::decrease_committed(size_t bytes) {
699 shenandoah_assert_heaplocked_or_safepoint();
700 _committed -= bytes;
701 }
702
703 // For tracking usage based on allocations, it should be the case that:
704 // * The sum of regions::used == heap::used
705 // * The sum of a generation's regions::used == generation::used
706 // * The sum of a generation's humongous regions::free == generation::humongous_waste
707 // These invariants are checked by the verifier on GC safepoints.
708 //
709 // Additional notes:
710 // * When a mutator's allocation request causes a region to be retired, the
711 // free memory left in that region is considered waste. It does not contribute
712 // to the usage, but it _does_ contribute to allocation rate.
713 // * The bottom of a PLAB must be aligned on card size. In some cases this will
714 // require padding in front of the PLAB (a filler object). Because this padding
715 // is included in the region's used memory we include the padding in the usage
716 // accounting as waste.
717 // * Mutator allocations are used to compute an allocation rate. They are also
718 // sent to the Pacer for those purposes.
719 // * There are three sources of waste:
720 // 1. The padding used to align a PLAB on card size
721 // 2. Region's free is less than minimum TLAB size and is retired
722 // 3. The unused portion of memory in the last region of a humongous object
723 void ShenandoahHeap::increase_used(const ShenandoahAllocRequest& req) {
724 size_t actual_bytes = req.actual_size() * HeapWordSize;
725 size_t wasted_bytes = req.waste() * HeapWordSize;
726 ShenandoahGeneration* generation = generation_for(req.affiliation());
727
728 if (req.is_gc_alloc()) {
729 assert(wasted_bytes == 0 || req.type() == ShenandoahAllocRequest::_alloc_plab, "Only PLABs have waste");
730 increase_used(generation, actual_bytes + wasted_bytes);
731 } else {
732 assert(req.is_mutator_alloc(), "Expected mutator alloc here");
733 // padding and actual size both count towards allocation counter
734 generation->increase_allocated(actual_bytes + wasted_bytes);
735
736 // only actual size counts toward usage for mutator allocations
737 increase_used(generation, actual_bytes);
738
739 // notify pacer of both actual size and waste
740 notify_mutator_alloc_words(req.actual_size(), req.waste());
741
742 if (wasted_bytes > 0 && ShenandoahHeapRegion::requires_humongous(req.actual_size())) {
743 increase_humongous_waste(generation,wasted_bytes);
744 }
745 }
746 }
747
748 void ShenandoahHeap::increase_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
749 generation->increase_humongous_waste(bytes);
750 if (!generation->is_global()) {
751 global_generation()->increase_humongous_waste(bytes);
752 }
753 }
754
755 void ShenandoahHeap::decrease_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
756 generation->decrease_humongous_waste(bytes);
757 if (!generation->is_global()) {
758 global_generation()->decrease_humongous_waste(bytes);
759 }
760 }
761
762 void ShenandoahHeap::increase_used(ShenandoahGeneration* generation, size_t bytes) {
763 generation->increase_used(bytes);
764 if (!generation->is_global()) {
765 global_generation()->increase_used(bytes);
766 }
767 }
768
769 void ShenandoahHeap::decrease_used(ShenandoahGeneration* generation, size_t bytes) {
770 generation->decrease_used(bytes);
771 if (!generation->is_global()) {
772 global_generation()->decrease_used(bytes);
773 }
774 }
775
776 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, size_t waste) {
777 if (ShenandoahPacing) {
778 control_thread()->pacing_notify_alloc(words);
779 if (waste > 0) {
780 pacer()->claim_for_alloc<true>(waste);
781 }
782 }
783 }
784
785 size_t ShenandoahHeap::capacity() const {
786 return committed();
787 }
788
789 size_t ShenandoahHeap::max_capacity() const {
790 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
791 }
792
793 size_t ShenandoahHeap::soft_max_capacity() const {
794 size_t v = Atomic::load(&_soft_max_size);
795 assert(min_capacity() <= v && v <= max_capacity(),
796 "Should be in bounds: %zu <= %zu <= %zu",
797 min_capacity(), v, max_capacity());
798 return v;
799 }
800
801 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
802 assert(min_capacity() <= v && v <= max_capacity(),
803 "Should be in bounds: %zu <= %zu <= %zu",
804 min_capacity(), v, max_capacity());
805 Atomic::store(&_soft_max_size, v);
806 }
807
808 size_t ShenandoahHeap::min_capacity() const {
809 return _minimum_size;
810 }
811
812 size_t ShenandoahHeap::initial_capacity() const {
813 return _initial_size;
814 }
815
816 bool ShenandoahHeap::is_in(const void* p) const {
817 if (!is_in_reserved(p)) {
818 return false;
819 }
820
821 if (is_full_gc_move_in_progress()) {
822 // Full GC move is running, we do not have a consistent region
823 // information yet. But we know the pointer is in heap.
824 return true;
825 }
826
827 // Now check if we point to a live section in active region.
828 const ShenandoahHeapRegion* r = heap_region_containing(p);
829 if (p >= r->top()) {
830 return false;
831 }
832
833 if (r->is_active()) {
834 return true;
835 }
836
837 // The region is trash, but won't be recycled until after concurrent weak
838 // roots. We also don't allow mutators to allocate from trash regions
839 // during weak roots. Concurrent class unloading may access unmarked oops
840 // in trash regions.
841 return r->is_trash() && is_concurrent_weak_root_in_progress();
842 }
843
844 void ShenandoahHeap::notify_soft_max_changed() {
845 if (_uncommit_thread != nullptr) {
846 _uncommit_thread->notify_soft_max_changed();
847 }
848 }
849
850 void ShenandoahHeap::notify_explicit_gc_requested() {
851 if (_uncommit_thread != nullptr) {
852 _uncommit_thread->notify_explicit_gc_requested();
853 }
854 }
855
856 bool ShenandoahHeap::check_soft_max_changed() {
857 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
858 size_t old_soft_max = soft_max_capacity();
859 if (new_soft_max != old_soft_max) {
860 new_soft_max = MAX2(min_capacity(), new_soft_max);
861 new_soft_max = MIN2(max_capacity(), new_soft_max);
862 if (new_soft_max != old_soft_max) {
863 log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s",
864 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
865 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
866 );
867 set_soft_max_capacity(new_soft_max);
868 return true;
869 }
870 }
871 return false;
872 }
873
874 void ShenandoahHeap::notify_heap_changed() {
875 // Update monitoring counters when we took a new region. This amortizes the
876 // update costs on slow path.
877 monitoring_support()->notify_heap_changed();
878 _heap_changed.try_set();
879 }
880
881 void ShenandoahHeap::set_forced_counters_update(bool value) {
882 monitoring_support()->set_forced_counters_update(value);
883 }
884
885 void ShenandoahHeap::handle_force_counters_update() {
886 monitoring_support()->handle_force_counters_update();
887 }
888
889 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
890 // New object should fit the GCLAB size
891 size_t min_size = MAX2(size, PLAB::min_size());
892
893 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
894 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
895
896 new_size = MIN2(new_size, PLAB::max_size());
897 new_size = MAX2(new_size, PLAB::min_size());
898
899 // Record new heuristic value even if we take any shortcut. This captures
900 // the case when moderately-sized objects always take a shortcut. At some point,
901 // heuristics should catch up with them.
902 log_debug(gc, free)("Set new GCLAB size: %zu", new_size);
903 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
904
905 if (new_size < size) {
906 // New size still does not fit the object. Fall back to shared allocation.
907 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
908 log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size);
909 return nullptr;
910 }
911
912 // Retire current GCLAB, and allocate a new one.
913 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
914 gclab->retire();
915
916 size_t actual_size = 0;
917 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
918 if (gclab_buf == nullptr) {
919 return nullptr;
920 }
921
922 assert (size <= actual_size, "allocation should fit");
923
924 // ...and clear or zap just allocated TLAB, if needed.
925 if (ZeroTLAB) {
926 Copy::zero_to_words(gclab_buf, actual_size);
927 } else if (ZapTLAB) {
928 // Skip mangling the space corresponding to the object header to
929 // ensure that the returned space is not considered parsable by
930 // any concurrent GC thread.
931 size_t hdr_size = oopDesc::header_size();
932 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
933 }
934 gclab->set_buf(gclab_buf, actual_size);
935 return gclab->allocate(size);
936 }
937
938 // Called from stubs in JIT code or interpreter
939 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
940 size_t requested_size,
941 size_t* actual_size) {
942 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
943 HeapWord* res = allocate_memory(req);
944 if (res != nullptr) {
945 *actual_size = req.actual_size();
946 } else {
947 *actual_size = 0;
948 }
949 return res;
950 }
951
952 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
953 size_t word_size,
954 size_t* actual_size) {
955 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
956 HeapWord* res = allocate_memory(req);
957 if (res != nullptr) {
958 *actual_size = req.actual_size();
959 } else {
960 *actual_size = 0;
961 }
962 return res;
963 }
964
965 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
966 intptr_t pacer_epoch = 0;
967 bool in_new_region = false;
968 HeapWord* result = nullptr;
969
970 if (req.is_mutator_alloc()) {
971 if (ShenandoahPacing) {
972 pacer()->pace_for_alloc(req.size());
973 pacer_epoch = pacer()->epoch();
974 }
975
976 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
977 result = allocate_memory_under_lock(req, in_new_region);
978 }
979
980 // Check that gc overhead is not exceeded.
981 //
982 // Shenandoah will grind along for quite a while allocating one
983 // object at a time using shared (non-tlab) allocations. This check
984 // is testing that the GC overhead limit has not been exceeded.
985 // This will notify the collector to start a cycle, but will raise
986 // an OOME to the mutator if the last Full GCs have not made progress.
987 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
988 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
989 control_thread()->handle_alloc_failure(req, false);
990 req.set_actual_size(0);
991 return nullptr;
992 }
993
994 if (result == nullptr) {
995 // Block until control thread reacted, then retry allocation.
996 //
997 // It might happen that one of the threads requesting allocation would unblock
998 // way later after GC happened, only to fail the second allocation, because
999 // other threads have already depleted the free storage. In this case, a better
1000 // strategy is to try again, until at least one full GC has completed.
1001 //
1002 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
1003 // a) We experienced a GC that had good progress, or
1004 // b) We experienced at least one Full GC (whether or not it had good progress)
1005
1006 const size_t original_count = shenandoah_policy()->full_gc_count();
1007 while (result == nullptr && should_retry_allocation(original_count)) {
1008 control_thread()->handle_alloc_failure(req, true);
1009 result = allocate_memory_under_lock(req, in_new_region);
1010 }
1011 if (result != nullptr) {
1012 // If our allocation request has been satisfied after it initially failed, we count this as good gc progress
1013 notify_gc_progress();
1014 }
1015 if (log_develop_is_enabled(Debug, gc, alloc)) {
1016 ResourceMark rm;
1017 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu"
1018 ", Original: %zu, Latest: %zu",
1019 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
1020 original_count, get_gc_no_progress_count());
1021 }
1022 }
1023 } else {
1024 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
1025 result = allocate_memory_under_lock(req, in_new_region);
1026 // Do not call handle_alloc_failure() here, because we cannot block.
1027 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1028 }
1029
1030 if (in_new_region) {
1031 notify_heap_changed();
1032 }
1033
1034 if (result == nullptr) {
1035 req.set_actual_size(0);
1036 }
1037
1038 // This is called regardless of the outcome of the allocation to account
1039 // for any waste created by retiring regions with this request.
1040 increase_used(req);
1041
1042 if (result != nullptr) {
1043 size_t requested = req.size();
1044 size_t actual = req.actual_size();
1045
1046 assert (req.is_lab_alloc() || (requested == actual),
1047 "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu",
1048 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
1049
1050 if (req.is_mutator_alloc()) {
1051 // If we requested more than we were granted, give the rest back to pacer.
1052 // This only matters if we are in the same pacing epoch: do not try to unpace
1053 // over the budget for the other phase.
1054 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
1055 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
1056 }
1057 }
1058 }
1059
1060 return result;
1061 }
1062
1063 inline bool ShenandoahHeap::should_retry_allocation(size_t original_full_gc_count) const {
1064 return shenandoah_policy()->full_gc_count() == original_full_gc_count
1065 && !shenandoah_policy()->is_at_shutdown();
1066 }
1067
1068 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1069 // If we are dealing with mutator allocation, then we may need to block for safepoint.
1070 // We cannot block for safepoint for GC allocations, because there is a high chance
1071 // we are already running at safepoint or from stack watermark machinery, and we cannot
1072 // block again.
1073 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1074
1075 // Make sure the old generation has room for either evacuations or promotions before trying to allocate.
1076 if (req.is_old() && !old_generation()->can_allocate(req)) {
1077 return nullptr;
1078 }
1079
1080 // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available
1081 // memory.
1082 HeapWord* result = _free_set->allocate(req, in_new_region);
1083
1084 // Record the plab configuration for this result and register the object.
1085 if (result != nullptr && req.is_old()) {
1086 old_generation()->configure_plab_for_current_thread(req);
1087 if (req.type() == ShenandoahAllocRequest::_alloc_shared_gc) {
1088 // Register the newly allocated object while we're holding the global lock since there's no synchronization
1089 // built in to the implementation of register_object(). There are potential races when multiple independent
1090 // threads are allocating objects, some of which might span the same card region. For example, consider
1091 // a card table's memory region within which three objects are being allocated by three different threads:
1092 //
1093 // objects being "concurrently" allocated:
1094 // [-----a------][-----b-----][--------------c------------------]
1095 // [---- card table memory range --------------]
1096 //
1097 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a
1098 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region.
1099 // Allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region.
1100 // Allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this
1101 // card region.
1102 //
1103 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as
1104 // last-start representing object b while first-start represents object c. This is why we need to require all
1105 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range.
1106 old_generation()->card_scan()->register_object(result);
1107 }
1108 }
1109
1110 return result;
1111 }
1112
1113 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1114 bool* gc_overhead_limit_was_exceeded) {
1115 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1116 return allocate_memory(req);
1117 }
1118
1119 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1120 size_t size,
1121 Metaspace::MetadataType mdtype) {
1122 MetaWord* result;
1123
1124 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1125 ShenandoahHeuristics* h = global_generation()->heuristics();
1126 if (h->can_unload_classes()) {
1127 h->record_metaspace_oom();
1128 }
1129
1130 // Expand and retry allocation
1131 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1132 if (result != nullptr) {
1133 return result;
1134 }
1135
1136 // Start full GC
1137 collect(GCCause::_metadata_GC_clear_soft_refs);
1138
1139 // Retry allocation
1140 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1141 if (result != nullptr) {
1142 return result;
1143 }
1144
1145 // Expand and retry allocation
1146 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1147 if (result != nullptr) {
1148 return result;
1149 }
1150
1151 // Out of memory
1152 return nullptr;
1153 }
1154
1155 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1156 private:
1157 ShenandoahHeap* const _heap;
1158 Thread* const _thread;
1159 public:
1160 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1161 _heap(heap), _thread(Thread::current()) {}
1162
1163 void do_object(oop p) {
1164 shenandoah_assert_marked(nullptr, p);
1165 if (!p->is_forwarded()) {
1166 _heap->evacuate_object(p, _thread);
1167 }
1168 }
1169 };
1170
1171 class ShenandoahEvacuationTask : public WorkerTask {
1172 private:
1173 ShenandoahHeap* const _sh;
1174 ShenandoahCollectionSet* const _cs;
1175 bool _concurrent;
1176 public:
1177 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1178 ShenandoahCollectionSet* cs,
1179 bool concurrent) :
1180 WorkerTask("Shenandoah Evacuation"),
1181 _sh(sh),
1182 _cs(cs),
1183 _concurrent(concurrent)
1184 {}
1185
1186 void work(uint worker_id) {
1187 if (_concurrent) {
1188 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1189 ShenandoahSuspendibleThreadSetJoiner stsj;
1190 ShenandoahEvacOOMScope oom_evac_scope;
1191 do_work();
1192 } else {
1193 ShenandoahParallelWorkerSession worker_session(worker_id);
1194 ShenandoahEvacOOMScope oom_evac_scope;
1195 do_work();
1196 }
1197 }
1198
1199 private:
1200 void do_work() {
1201 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1202 ShenandoahHeapRegion* r;
1203 while ((r =_cs->claim_next()) != nullptr) {
1204 assert(r->has_live(), "Region %zu should have been reclaimed early", r->index());
1205 _sh->marked_object_iterate(r, &cl);
1206
1207 if (ShenandoahPacing) {
1208 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1209 }
1210
1211 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1212 break;
1213 }
1214 }
1215 }
1216 };
1217
1218 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1219 private:
1220 bool const _resize;
1221 public:
1222 explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1223 void do_thread(Thread* thread) override {
1224 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1225 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1226 gclab->retire();
1227 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1228 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1229 }
1230
1231 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1232 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1233 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1234
1235 // There are two reasons to retire all plabs between old-gen evacuation passes.
1236 // 1. We need to make the plab memory parsable by remembered-set scanning.
1237 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1238 ShenandoahGenerationalHeap::heap()->retire_plab(plab, thread);
1239 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) {
1240 ShenandoahThreadLocalData::set_plab_size(thread, 0);
1241 }
1242 }
1243 }
1244 };
1245
1246 class ShenandoahGCStatePropagator : public HandshakeClosure {
1247 public:
1248 explicit ShenandoahGCStatePropagator(char gc_state) :
1249 HandshakeClosure("Shenandoah GC State Change"),
1250 _gc_state(gc_state) {}
1251
1252 void do_thread(Thread* thread) override {
1253 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state);
1254 }
1255 private:
1256 char _gc_state;
1257 };
1258
1259 class ShenandoahPrepareForUpdateRefs : public HandshakeClosure {
1260 public:
1261 explicit ShenandoahPrepareForUpdateRefs(char gc_state) :
1262 HandshakeClosure("Shenandoah Prepare for Update Refs"),
1263 _retire(ResizeTLAB), _propagator(gc_state) {}
1264
1265 void do_thread(Thread* thread) override {
1266 _propagator.do_thread(thread);
1267 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) {
1268 _retire.do_thread(thread);
1269 }
1270 }
1271 private:
1272 ShenandoahRetireGCLABClosure _retire;
1273 ShenandoahGCStatePropagator _propagator;
1274 };
1275
1276 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1277 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1278 workers()->run_task(&task);
1279 }
1280
1281 void ShenandoahHeap::concurrent_prepare_for_update_refs() {
1282 {
1283 // Java threads take this lock while they are being attached and added to the list of thread.
1284 // If another thread holds this lock before we update the gc state, it will receive a stale
1285 // gc state, but they will have been added to the list of java threads and so will be corrected
1286 // by the following handshake.
1287 MutexLocker lock(Threads_lock);
1288
1289 // A cancellation at this point means the degenerated cycle must resume from update-refs.
1290 set_gc_state_concurrent(EVACUATION, false);
1291 set_gc_state_concurrent(WEAK_ROOTS, false);
1292 set_gc_state_concurrent(UPDATE_REFS, true);
1293 }
1294
1295 // This will propagate the gc state and retire gclabs and plabs for threads that require it.
1296 ShenandoahPrepareForUpdateRefs prepare_for_update_refs(_gc_state.raw_value());
1297
1298 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately.
1299 Threads::non_java_threads_do(&prepare_for_update_refs);
1300
1301 // Now retire gclabs and plabs and propagate gc_state for mutator threads
1302 Handshake::execute(&prepare_for_update_refs);
1303
1304 _update_refs_iterator.reset();
1305 }
1306
1307 class ShenandoahCompositeHandshakeClosure : public HandshakeClosure {
1308 HandshakeClosure* _handshake_1;
1309 HandshakeClosure* _handshake_2;
1310 public:
1311 ShenandoahCompositeHandshakeClosure(HandshakeClosure* handshake_1, HandshakeClosure* handshake_2) :
1312 HandshakeClosure(handshake_2->name()),
1313 _handshake_1(handshake_1), _handshake_2(handshake_2) {}
1314
1315 void do_thread(Thread* thread) override {
1316 _handshake_1->do_thread(thread);
1317 _handshake_2->do_thread(thread);
1318 }
1319 };
1320
1321 void ShenandoahHeap::concurrent_final_roots(HandshakeClosure* handshake_closure) {
1322 {
1323 assert(!is_evacuation_in_progress(), "Should not evacuate for abbreviated or old cycles");
1324 MutexLocker lock(Threads_lock);
1325 set_gc_state_concurrent(WEAK_ROOTS, false);
1326 }
1327
1328 ShenandoahGCStatePropagator propagator(_gc_state.raw_value());
1329 Threads::non_java_threads_do(&propagator);
1330 if (handshake_closure == nullptr) {
1331 Handshake::execute(&propagator);
1332 } else {
1333 ShenandoahCompositeHandshakeClosure composite(&propagator, handshake_closure);
1334 Handshake::execute(&composite);
1335 }
1336 }
1337
1338 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1339 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1340 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
1341 // This thread went through the OOM during evac protocol. It is safe to return
1342 // the forward pointer. It must not attempt to evacuate any other objects.
1343 return ShenandoahBarrierSet::resolve_forwarded(p);
1344 }
1345
1346 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1347
1348 ShenandoahHeapRegion* r = heap_region_containing(p);
1349 assert(!r->is_humongous(), "never evacuate humongous objects");
1350
1351 ShenandoahAffiliation target_gen = r->affiliation();
1352 return try_evacuate_object(p, thread, r, target_gen);
1353 }
1354
1355 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1356 ShenandoahAffiliation target_gen) {
1357 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1358 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1359 bool alloc_from_lab = true;
1360 HeapWord* copy = nullptr;
1361
1362 markWord mark = p->mark();
1363 if (ShenandoahForwarding::is_forwarded(mark)) {
1364 return ShenandoahForwarding::get_forwardee(p);
1365 }
1366 size_t old_size = ShenandoahForwarding::size(p);
1367 size_t size = p->copy_size(old_size, mark);
1368
1369 #ifdef ASSERT
1370 if (ShenandoahOOMDuringEvacALot &&
1371 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1372 copy = nullptr;
1373 } else {
1374 #endif
1375 if (UseTLAB) {
1376 copy = allocate_from_gclab(thread, size);
1377 }
1378 if (copy == nullptr) {
1379 // If we failed to allocate in LAB, we'll try a shared allocation.
1380 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1381 copy = allocate_memory(req);
1382 alloc_from_lab = false;
1383 }
1384 #ifdef ASSERT
1385 }
1386 #endif
1387
1388 if (copy == nullptr) {
1389 control_thread()->handle_alloc_failure_evac(size);
1390
1391 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1392
1393 return ShenandoahBarrierSet::resolve_forwarded(p);
1394 }
1395
1396 // Copy the object:
1397 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, old_size);
1398
1399 // Try to install the new forwarding pointer.
1400 oop copy_val = cast_to_oop(copy);
1401 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1402 if (result == copy_val) {
1403 // Successfully evacuated. Our copy is now the public one!
1404 copy_val->initialize_hash_if_necessary(p);
1405 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1406 shenandoah_assert_correct(nullptr, copy_val);
1407 return copy_val;
1408 } else {
1409 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1410 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1411 // But if it happens to contain references to evacuated regions, those references would
1412 // not get updated for this stale copy during this cycle, and we will crash while scanning
1413 // it the next cycle.
1414 if (alloc_from_lab) {
1415 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1416 // object will overwrite this stale copy, or the filler object on LAB retirement will
1417 // do this.
1418 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1419 } else {
1420 // For non-LAB allocations, we have no way to retract the allocation, and
1421 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1422 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1423 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1424 fill_with_object(copy, size);
1425 shenandoah_assert_correct(nullptr, copy_val);
1426 // For non-LAB allocations, the object has already been registered
1427 }
1428 shenandoah_assert_correct(nullptr, result);
1429 return result;
1430 }
1431 }
1432
1433 void ShenandoahHeap::trash_cset_regions() {
1434 ShenandoahHeapLocker locker(lock());
1435
1436 ShenandoahCollectionSet* set = collection_set();
1437 ShenandoahHeapRegion* r;
1438 set->clear_current_index();
1439 while ((r = set->next()) != nullptr) {
1440 r->make_trash();
1441 }
1442 collection_set()->clear();
1443 }
1444
1445 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1446 st->print_cr("Heap Regions:");
1447 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1448 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1449 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1450 st->print_cr("UWM=update watermark, U=used");
1451 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1452 st->print_cr("S=shared allocs, L=live data");
1453 st->print_cr("CP=critical pins");
1454
1455 for (size_t i = 0; i < num_regions(); i++) {
1456 get_region(i)->print_on(st);
1457 }
1458 }
1459
1460 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1461 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1462
1463 oop humongous_obj = cast_to_oop(start->bottom());
1464 size_t size = humongous_obj->size();
1465 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1466 size_t index = start->index() + required_regions - 1;
1467
1468 assert(!start->has_live(), "liveness must be zero");
1469
1470 for(size_t i = 0; i < required_regions; i++) {
1471 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1472 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1473 ShenandoahHeapRegion* region = get_region(index --);
1474
1475 assert(region->is_humongous(), "expect correct humongous start or continuation");
1476 assert(!region->is_cset(), "Humongous region should not be in collection set");
1477
1478 region->make_trash_immediate();
1479 }
1480 return required_regions;
1481 }
1482
1483 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1484 public:
1485 ShenandoahCheckCleanGCLABClosure() {}
1486 void do_thread(Thread* thread) {
1487 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1488 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1489 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1490
1491 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1492 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1493 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1494 assert(plab->words_remaining() == 0, "PLAB should not need retirement");
1495 }
1496 }
1497 };
1498
1499 void ShenandoahHeap::labs_make_parsable() {
1500 assert(UseTLAB, "Only call with UseTLAB");
1501
1502 ShenandoahRetireGCLABClosure cl(false);
1503
1504 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1505 ThreadLocalAllocBuffer& tlab = t->tlab();
1506 tlab.make_parsable();
1507 cl.do_thread(t);
1508 }
1509
1510 workers()->threads_do(&cl);
1511
1512 if (safepoint_workers() != nullptr) {
1513 safepoint_workers()->threads_do(&cl);
1514 }
1515 }
1516
1517 void ShenandoahHeap::tlabs_retire(bool resize) {
1518 assert(UseTLAB, "Only call with UseTLAB");
1519 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1520
1521 ThreadLocalAllocStats stats;
1522
1523 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1524 ThreadLocalAllocBuffer& tlab = t->tlab();
1525 tlab.retire(&stats);
1526 if (resize) {
1527 tlab.resize();
1528 }
1529 }
1530
1531 stats.publish();
1532
1533 #ifdef ASSERT
1534 ShenandoahCheckCleanGCLABClosure cl;
1535 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1536 cl.do_thread(t);
1537 }
1538 workers()->threads_do(&cl);
1539 #endif
1540 }
1541
1542 void ShenandoahHeap::gclabs_retire(bool resize) {
1543 assert(UseTLAB, "Only call with UseTLAB");
1544 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1545
1546 ShenandoahRetireGCLABClosure cl(resize);
1547 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1548 cl.do_thread(t);
1549 }
1550
1551 workers()->threads_do(&cl);
1552
1553 if (safepoint_workers() != nullptr) {
1554 safepoint_workers()->threads_do(&cl);
1555 }
1556 }
1557
1558 // Returns size in bytes
1559 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1560 // Return the max allowed size, and let the allocation path
1561 // figure out the safe size for current allocation.
1562 return ShenandoahHeapRegion::max_tlab_size_bytes();
1563 }
1564
1565 size_t ShenandoahHeap::max_tlab_size() const {
1566 // Returns size in words
1567 return ShenandoahHeapRegion::max_tlab_size_words();
1568 }
1569
1570 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) {
1571 // These requests are ignored because we can't easily have Shenandoah jump into
1572 // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent
1573 // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly
1574 // on the VM thread, but this would confuse the control thread mightily and doesn't
1575 // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a
1576 // concurrent cycle in the prologue of the heap inspect/dump operation. This is how
1577 // other concurrent collectors in the JVM handle this scenario as well.
1578 assert(Thread::current()->is_VM_thread(), "Should be the VM thread");
1579 guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause");
1580 }
1581
1582 void ShenandoahHeap::collect(GCCause::Cause cause) {
1583 control_thread()->request_gc(cause);
1584 }
1585
1586 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1587 //assert(false, "Shouldn't need to do full collections");
1588 }
1589
1590 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1591 ShenandoahHeapRegion* r = heap_region_containing(addr);
1592 if (r != nullptr) {
1593 return r->block_start(addr);
1594 }
1595 return nullptr;
1596 }
1597
1598 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1599 ShenandoahHeapRegion* r = heap_region_containing(addr);
1600 return r->block_is_obj(addr);
1601 }
1602
1603 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1604 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1605 }
1606
1607 void ShenandoahHeap::prepare_for_verify() {
1608 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1609 labs_make_parsable();
1610 }
1611 }
1612
1613 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1614 if (_shenandoah_policy->is_at_shutdown()) {
1615 return;
1616 }
1617
1618 if (_control_thread != nullptr) {
1619 tcl->do_thread(_control_thread);
1620 }
1621
1622 if (_uncommit_thread != nullptr) {
1623 tcl->do_thread(_uncommit_thread);
1624 }
1625
1626 workers()->threads_do(tcl);
1627 if (_safepoint_workers != nullptr) {
1628 _safepoint_workers->threads_do(tcl);
1629 }
1630 }
1631
1632 void ShenandoahHeap::print_tracing_info() const {
1633 LogTarget(Info, gc, stats) lt;
1634 if (lt.is_enabled()) {
1635 ResourceMark rm;
1636 LogStream ls(lt);
1637
1638 phase_timings()->print_global_on(&ls);
1639
1640 ls.cr();
1641 ls.cr();
1642
1643 shenandoah_policy()->print_gc_stats(&ls);
1644
1645 ls.cr();
1646 ls.cr();
1647 }
1648 }
1649
1650 void ShenandoahHeap::set_gc_generation(ShenandoahGeneration* generation) {
1651 shenandoah_assert_control_or_vm_thread_at_safepoint();
1652 _gc_generation = generation;
1653 }
1654
1655 // Active generation may only be set by the VM thread at a safepoint.
1656 void ShenandoahHeap::set_active_generation() {
1657 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1658 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1659 assert(_gc_generation != nullptr, "Will set _active_generation to nullptr");
1660 _active_generation = _gc_generation;
1661 }
1662
1663 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
1664 shenandoah_policy()->record_collection_cause(cause);
1665
1666 const GCCause::Cause current = gc_cause();
1667 assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s",
1668 GCCause::to_string(current), GCCause::to_string(cause));
1669 assert(_gc_generation == nullptr, "Over-writing _gc_generation");
1670
1671 set_gc_cause(cause);
1672 set_gc_generation(generation);
1673
1674 generation->heuristics()->record_cycle_start();
1675 }
1676
1677 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1678 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1679 assert(_gc_generation != nullptr, "_gc_generation wasn't set");
1680
1681 generation->heuristics()->record_cycle_end();
1682 if (mode()->is_generational() && generation->is_global()) {
1683 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1684 young_generation()->heuristics()->record_cycle_end();
1685 old_generation()->heuristics()->record_cycle_end();
1686 }
1687
1688 set_gc_generation(nullptr);
1689 set_gc_cause(GCCause::_no_gc);
1690 }
1691
1692 void ShenandoahHeap::verify(VerifyOption vo) {
1693 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1694 if (ShenandoahVerify) {
1695 verifier()->verify_generic(vo);
1696 } else {
1697 // TODO: Consider allocating verification bitmaps on demand,
1698 // and turn this on unconditionally.
1699 }
1700 }
1701 }
1702 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1703 return _free_set->capacity();
1704 }
1705
1706 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1707 private:
1708 MarkBitMap* _bitmap;
1709 ShenandoahScanObjectStack* _oop_stack;
1710 ShenandoahHeap* const _heap;
1711 ShenandoahMarkingContext* const _marking_context;
1712
1713 template <class T>
1714 void do_oop_work(T* p) {
1715 T o = RawAccess<>::oop_load(p);
1716 if (!CompressedOops::is_null(o)) {
1717 oop obj = CompressedOops::decode_not_null(o);
1718 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1719 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1720 return;
1721 }
1722 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1723
1724 assert(oopDesc::is_oop(obj), "must be a valid oop");
1725 if (!_bitmap->is_marked(obj)) {
1726 _bitmap->mark(obj);
1727 _oop_stack->push(obj);
1728 }
1729 }
1730 }
1731 public:
1732 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1733 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1734 _marking_context(_heap->marking_context()) {}
1735 void do_oop(oop* p) { do_oop_work(p); }
1736 void do_oop(narrowOop* p) { do_oop_work(p); }
1737 };
1738
1739 /*
1740 * This is public API, used in preparation of object_iterate().
1741 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1742 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1743 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1744 */
1745 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1746 // No-op.
1747 }
1748
1749 /*
1750 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1751 *
1752 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1753 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1754 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1755 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1756 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1757 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1758 * wiped the bitmap in preparation for next marking).
1759 *
1760 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1761 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1762 * is allowed to report dead objects, but is not required to do so.
1763 */
1764 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1765 // Reset bitmap
1766 if (!prepare_aux_bitmap_for_iteration())
1767 return;
1768
1769 ShenandoahScanObjectStack oop_stack;
1770 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1771 // Seed the stack with root scan
1772 scan_roots_for_iteration(&oop_stack, &oops);
1773
1774 // Work through the oop stack to traverse heap
1775 while (! oop_stack.is_empty()) {
1776 oop obj = oop_stack.pop();
1777 assert(oopDesc::is_oop(obj), "must be a valid oop");
1778 cl->do_object(obj);
1779 obj->oop_iterate(&oops);
1780 }
1781
1782 assert(oop_stack.is_empty(), "should be empty");
1783 // Reclaim bitmap
1784 reclaim_aux_bitmap_for_iteration();
1785 }
1786
1787 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1788 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1789
1790 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1791 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1792 return false;
1793 }
1794 // Reset bitmap
1795 _aux_bit_map.clear();
1796 return true;
1797 }
1798
1799 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1800 // Process GC roots according to current GC cycle
1801 // This populates the work stack with initial objects
1802 // It is important to relinquish the associated locks before diving
1803 // into heap dumper
1804 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1805 ShenandoahHeapIterationRootScanner rp(n_workers);
1806 rp.roots_do(oops);
1807 }
1808
1809 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1810 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1811 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1812 }
1813 }
1814
1815 // Closure for parallelly iterate objects
1816 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1817 private:
1818 MarkBitMap* _bitmap;
1819 ShenandoahObjToScanQueue* _queue;
1820 ShenandoahHeap* const _heap;
1821 ShenandoahMarkingContext* const _marking_context;
1822
1823 template <class T>
1824 void do_oop_work(T* p) {
1825 T o = RawAccess<>::oop_load(p);
1826 if (!CompressedOops::is_null(o)) {
1827 oop obj = CompressedOops::decode_not_null(o);
1828 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1829 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1830 return;
1831 }
1832 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1833
1834 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1835 if (_bitmap->par_mark(obj)) {
1836 _queue->push(ShenandoahMarkTask(obj));
1837 }
1838 }
1839 }
1840 public:
1841 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1842 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1843 _marking_context(_heap->marking_context()) {}
1844 void do_oop(oop* p) { do_oop_work(p); }
1845 void do_oop(narrowOop* p) { do_oop_work(p); }
1846 };
1847
1848 // Object iterator for parallel heap iteraion.
1849 // The root scanning phase happenes in construction as a preparation of
1850 // parallel marking queues.
1851 // Every worker processes it's own marking queue. work-stealing is used
1852 // to balance workload.
1853 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1854 private:
1855 uint _num_workers;
1856 bool _init_ready;
1857 MarkBitMap* _aux_bit_map;
1858 ShenandoahHeap* _heap;
1859 ShenandoahScanObjectStack _roots_stack; // global roots stack
1860 ShenandoahObjToScanQueueSet* _task_queues;
1861 public:
1862 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1863 _num_workers(num_workers),
1864 _init_ready(false),
1865 _aux_bit_map(bitmap),
1866 _heap(ShenandoahHeap::heap()) {
1867 // Initialize bitmap
1868 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1869 if (!_init_ready) {
1870 return;
1871 }
1872
1873 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1874 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1875
1876 _init_ready = prepare_worker_queues();
1877 }
1878
1879 ~ShenandoahParallelObjectIterator() {
1880 // Reclaim bitmap
1881 _heap->reclaim_aux_bitmap_for_iteration();
1882 // Reclaim queue for workers
1883 if (_task_queues!= nullptr) {
1884 for (uint i = 0; i < _num_workers; ++i) {
1885 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1886 if (q != nullptr) {
1887 delete q;
1888 _task_queues->register_queue(i, nullptr);
1889 }
1890 }
1891 delete _task_queues;
1892 _task_queues = nullptr;
1893 }
1894 }
1895
1896 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1897 if (_init_ready) {
1898 object_iterate_parallel(cl, worker_id, _task_queues);
1899 }
1900 }
1901
1902 private:
1903 // Divide global root_stack into worker queues
1904 bool prepare_worker_queues() {
1905 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1906 // Initialize queues for every workers
1907 for (uint i = 0; i < _num_workers; ++i) {
1908 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1909 _task_queues->register_queue(i, task_queue);
1910 }
1911 // Divide roots among the workers. Assume that object referencing distribution
1912 // is related with root kind, use round-robin to make every worker have same chance
1913 // to process every kind of roots
1914 size_t roots_num = _roots_stack.size();
1915 if (roots_num == 0) {
1916 // No work to do
1917 return false;
1918 }
1919
1920 for (uint j = 0; j < roots_num; j++) {
1921 uint stack_id = j % _num_workers;
1922 oop obj = _roots_stack.pop();
1923 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1924 }
1925 return true;
1926 }
1927
1928 void object_iterate_parallel(ObjectClosure* cl,
1929 uint worker_id,
1930 ShenandoahObjToScanQueueSet* queue_set) {
1931 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1932 assert(queue_set != nullptr, "task queue must not be null");
1933
1934 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1935 assert(q != nullptr, "object iterate queue must not be null");
1936
1937 ShenandoahMarkTask t;
1938 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1939
1940 // Work through the queue to traverse heap.
1941 // Steal when there is no task in queue.
1942 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1943 oop obj = t.obj();
1944 assert(oopDesc::is_oop(obj), "must be a valid oop");
1945 cl->do_object(obj);
1946 obj->oop_iterate(&oops);
1947 }
1948 assert(q->is_empty(), "should be empty");
1949 }
1950 };
1951
1952 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1953 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1954 }
1955
1956 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1957 void ShenandoahHeap::keep_alive(oop obj) {
1958 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1959 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1960 }
1961 }
1962
1963 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1964 for (size_t i = 0; i < num_regions(); i++) {
1965 ShenandoahHeapRegion* current = get_region(i);
1966 blk->heap_region_do(current);
1967 }
1968 }
1969
1970 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1971 private:
1972 ShenandoahHeap* const _heap;
1973 ShenandoahHeapRegionClosure* const _blk;
1974 size_t const _stride;
1975
1976 shenandoah_padding(0);
1977 volatile size_t _index;
1978 shenandoah_padding(1);
1979
1980 public:
1981 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
1982 WorkerTask("Shenandoah Parallel Region Operation"),
1983 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
1984
1985 void work(uint worker_id) {
1986 ShenandoahParallelWorkerSession worker_session(worker_id);
1987 size_t stride = _stride;
1988
1989 size_t max = _heap->num_regions();
1990 while (Atomic::load(&_index) < max) {
1991 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1992 size_t start = cur;
1993 size_t end = MIN2(cur + stride, max);
1994 if (start >= max) break;
1995
1996 for (size_t i = cur; i < end; i++) {
1997 ShenandoahHeapRegion* current = _heap->get_region(i);
1998 _blk->heap_region_do(current);
1999 }
2000 }
2001 }
2002 };
2003
2004 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
2005 assert(blk->is_thread_safe(), "Only thread-safe closures here");
2006 const uint active_workers = workers()->active_workers();
2007 const size_t n_regions = num_regions();
2008 size_t stride = ShenandoahParallelRegionStride;
2009 if (stride == 0 && active_workers > 1) {
2010 // Automatically derive the stride to balance the work between threads
2011 // evenly. Do not try to split work if below the reasonable threshold.
2012 constexpr size_t threshold = 4096;
2013 stride = n_regions <= threshold ?
2014 threshold :
2015 (n_regions + active_workers - 1) / active_workers;
2016 }
2017
2018 if (n_regions > stride && active_workers > 1) {
2019 ShenandoahParallelHeapRegionTask task(blk, stride);
2020 workers()->run_task(&task);
2021 } else {
2022 heap_region_iterate(blk);
2023 }
2024 }
2025
2026 class ShenandoahRendezvousClosure : public HandshakeClosure {
2027 public:
2028 inline ShenandoahRendezvousClosure(const char* name) : HandshakeClosure(name) {}
2029 inline void do_thread(Thread* thread) {}
2030 };
2031
2032 void ShenandoahHeap::rendezvous_threads(const char* name) {
2033 ShenandoahRendezvousClosure cl(name);
2034 Handshake::execute(&cl);
2035 }
2036
2037 void ShenandoahHeap::recycle_trash() {
2038 free_set()->recycle_trash();
2039 }
2040
2041 void ShenandoahHeap::do_class_unloading() {
2042 _unloader.unload();
2043 if (mode()->is_generational()) {
2044 old_generation()->set_parsable(false);
2045 }
2046 }
2047
2048 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
2049 // Weak refs processing
2050 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
2051 : ShenandoahPhaseTimings::degen_gc_weakrefs;
2052 ShenandoahTimingsTracker t(phase);
2053 ShenandoahGCWorkerPhase worker_phase(phase);
2054 shenandoah_assert_generations_reconciled();
2055 gc_generation()->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2056 }
2057
2058 void ShenandoahHeap::prepare_update_heap_references() {
2059 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2060
2061 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2062 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2063 // for future GCLABs here.
2064 if (UseTLAB) {
2065 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2066 gclabs_retire(ResizeTLAB);
2067 }
2068
2069 _update_refs_iterator.reset();
2070 }
2071
2072 void ShenandoahHeap::propagate_gc_state_to_all_threads() {
2073 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2074 if (_gc_state_changed) {
2075 ShenandoahGCStatePropagator propagator(_gc_state.raw_value());
2076 Threads::threads_do(&propagator);
2077 _gc_state_changed = false;
2078 }
2079 }
2080
2081 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) {
2082 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2083 _gc_state.set_cond(mask, value);
2084 _gc_state_changed = true;
2085 }
2086
2087 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) {
2088 // Holding the thread lock here assures that any thread created after we change the gc
2089 // state will have the correct state. It also prevents attaching threads from seeing
2090 // an inconsistent state. See ShenandoahBarrierSet::on_thread_attach for reference. Established
2091 // threads will use their thread local copy of the gc state (changed by a handshake, or on a
2092 // safepoint).
2093 assert(Threads_lock->is_locked(), "Must hold thread lock for concurrent gc state change");
2094 _gc_state.set_cond(mask, value);
2095 }
2096
2097 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2098 uint mask;
2099 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2100 if (!in_progress && is_concurrent_old_mark_in_progress()) {
2101 assert(mode()->is_generational(), "Only generational GC has old marking");
2102 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2103 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2104 mask = YOUNG_MARKING;
2105 } else {
2106 mask = MARKING | YOUNG_MARKING;
2107 }
2108 set_gc_state_at_safepoint(mask, in_progress);
2109 manage_satb_barrier(in_progress);
2110 }
2111
2112 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2113 #ifdef ASSERT
2114 // has_forwarded_objects() iff UPDATE_REFS or EVACUATION
2115 bool has_forwarded = has_forwarded_objects();
2116 bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION);
2117 bool evacuating = _gc_state.is_set(EVACUATION);
2118 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2119 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2120 #endif
2121 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2122 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2123 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2124 set_gc_state_at_safepoint(OLD_MARKING, in_progress);
2125 } else {
2126 set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress);
2127 }
2128 manage_satb_barrier(in_progress);
2129 }
2130
2131 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2132 return old_generation()->is_preparing_for_mark();
2133 }
2134
2135 void ShenandoahHeap::manage_satb_barrier(bool active) {
2136 if (is_concurrent_mark_in_progress()) {
2137 // Ignore request to deactivate barrier while concurrent mark is in progress.
2138 // Do not attempt to re-activate the barrier if it is already active.
2139 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2140 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2141 }
2142 } else {
2143 // No concurrent marking is in progress so honor request to deactivate,
2144 // but only if the barrier is already active.
2145 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2146 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2147 }
2148 }
2149 }
2150
2151 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2152 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2153 set_gc_state_at_safepoint(EVACUATION, in_progress);
2154 }
2155
2156 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2157 if (in_progress) {
2158 _concurrent_strong_root_in_progress.set();
2159 } else {
2160 _concurrent_strong_root_in_progress.unset();
2161 }
2162 }
2163
2164 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2165 set_gc_state_at_safepoint(WEAK_ROOTS, cond);
2166 }
2167
2168 GCTracer* ShenandoahHeap::tracer() {
2169 return shenandoah_policy()->tracer();
2170 }
2171
2172 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2173 return _free_set->used();
2174 }
2175
2176 bool ShenandoahHeap::try_cancel_gc(GCCause::Cause cause) {
2177 const GCCause::Cause prev = _cancelled_gc.xchg(cause);
2178 return prev == GCCause::_no_gc || prev == GCCause::_shenandoah_concurrent_gc;
2179 }
2180
2181 void ShenandoahHeap::cancel_concurrent_mark() {
2182 if (mode()->is_generational()) {
2183 young_generation()->cancel_marking();
2184 old_generation()->cancel_marking();
2185 }
2186
2187 global_generation()->cancel_marking();
2188
2189 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2190 }
2191
2192 bool ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2193 if (try_cancel_gc(cause)) {
2194 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2195 log_info(gc,thread)("%s", msg.buffer());
2196 Events::log(Thread::current(), "%s", msg.buffer());
2197 _cancel_requested_time = os::elapsedTime();
2198 return true;
2199 }
2200 return false;
2201 }
2202
2203 uint ShenandoahHeap::max_workers() {
2204 return _max_workers;
2205 }
2206
2207 void ShenandoahHeap::stop() {
2208 // The shutdown sequence should be able to terminate when GC is running.
2209
2210 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2211 _shenandoah_policy->record_shutdown();
2212
2213 // Step 1. Stop reporting on gc thread cpu utilization
2214 mmu_tracker()->stop();
2215
2216 // Step 2. Wait until GC worker exits normally (this will cancel any ongoing GC).
2217 control_thread()->stop();
2218
2219 // Stop 4. Shutdown uncommit thread.
2220 if (_uncommit_thread != nullptr) {
2221 _uncommit_thread->stop();
2222 }
2223 }
2224
2225 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2226 if (!unload_classes()) return;
2227 ClassUnloadingContext ctx(_workers->active_workers(),
2228 true /* unregister_nmethods_during_purge */,
2229 false /* lock_nmethod_free_separately */);
2230
2231 // Unload classes and purge SystemDictionary.
2232 {
2233 ShenandoahPhaseTimings::Phase phase = full_gc ?
2234 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2235 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2236 ShenandoahIsAliveSelector is_alive;
2237 {
2238 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2239 ShenandoahGCPhase gc_phase(phase);
2240 ShenandoahGCWorkerPhase worker_phase(phase);
2241 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2242
2243 uint num_workers = _workers->active_workers();
2244 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
2245 _workers->run_task(&unlink_task);
2246 }
2247 // Release unloaded nmethods's memory.
2248 ClassUnloadingContext::context()->purge_and_free_nmethods();
2249 }
2250
2251 {
2252 ShenandoahGCPhase phase(full_gc ?
2253 ShenandoahPhaseTimings::full_gc_purge_cldg :
2254 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2255 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2256 }
2257 // Resize and verify metaspace
2258 MetaspaceGC::compute_new_size();
2259 DEBUG_ONLY(MetaspaceUtils::verify();)
2260 }
2261
2262 // Weak roots are either pre-evacuated (final mark) or updated (final update refs),
2263 // so they should not have forwarded oops.
2264 // However, we do need to "null" dead oops in the roots, if can not be done
2265 // in concurrent cycles.
2266 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2267 uint num_workers = _workers->active_workers();
2268 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2269 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2270 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2271 ShenandoahGCPhase phase(timing_phase);
2272 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2273 // Cleanup weak roots
2274 if (has_forwarded_objects()) {
2275 ShenandoahForwardedIsAliveClosure is_alive;
2276 ShenandoahNonConcUpdateRefsClosure keep_alive;
2277 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2278 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2279 _workers->run_task(&cleaning_task);
2280 } else {
2281 ShenandoahIsAliveClosure is_alive;
2282 #ifdef ASSERT
2283 ShenandoahAssertNotForwardedClosure verify_cl;
2284 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2285 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2286 #else
2287 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2288 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2289 #endif
2290 _workers->run_task(&cleaning_task);
2291 }
2292 }
2293
2294 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2295 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2296 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2297 ShenandoahGCPhase phase(full_gc ?
2298 ShenandoahPhaseTimings::full_gc_purge :
2299 ShenandoahPhaseTimings::degen_gc_purge);
2300 stw_weak_refs(full_gc);
2301 stw_process_weak_roots(full_gc);
2302 stw_unload_classes(full_gc);
2303 }
2304
2305 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2306 set_gc_state_at_safepoint(HAS_FORWARDED, cond);
2307 }
2308
2309 void ShenandoahHeap::set_unload_classes(bool uc) {
2310 _unload_classes.set_cond(uc);
2311 }
2312
2313 bool ShenandoahHeap::unload_classes() const {
2314 return _unload_classes.is_set();
2315 }
2316
2317 address ShenandoahHeap::in_cset_fast_test_addr() {
2318 ShenandoahHeap* heap = ShenandoahHeap::heap();
2319 assert(heap->collection_set() != nullptr, "Sanity");
2320 return (address) heap->collection_set()->biased_map_address();
2321 }
2322
2323 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2324 if (mode()->is_generational()) {
2325 young_generation()->reset_bytes_allocated_since_gc_start();
2326 old_generation()->reset_bytes_allocated_since_gc_start();
2327 }
2328
2329 global_generation()->reset_bytes_allocated_since_gc_start();
2330 }
2331
2332 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2333 _degenerated_gc_in_progress.set_cond(in_progress);
2334 }
2335
2336 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2337 _full_gc_in_progress.set_cond(in_progress);
2338 }
2339
2340 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2341 assert (is_full_gc_in_progress(), "should be");
2342 _full_gc_move_in_progress.set_cond(in_progress);
2343 }
2344
2345 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2346 set_gc_state_at_safepoint(UPDATE_REFS, in_progress);
2347 }
2348
2349 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2350 ShenandoahCodeRoots::register_nmethod(nm);
2351 }
2352
2353 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2354 ShenandoahCodeRoots::unregister_nmethod(nm);
2355 }
2356
2357 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2358 heap_region_containing(o)->record_pin();
2359 }
2360
2361 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2362 ShenandoahHeapRegion* r = heap_region_containing(o);
2363 assert(r != nullptr, "Sanity");
2364 assert(r->pin_count() > 0, "Region %zu should have non-zero pins", r->index());
2365 r->record_unpin();
2366 }
2367
2368 void ShenandoahHeap::sync_pinned_region_status() {
2369 ShenandoahHeapLocker locker(lock());
2370
2371 for (size_t i = 0; i < num_regions(); i++) {
2372 ShenandoahHeapRegion *r = get_region(i);
2373 if (r->is_active()) {
2374 if (r->is_pinned()) {
2375 if (r->pin_count() == 0) {
2376 r->make_unpinned();
2377 }
2378 } else {
2379 if (r->pin_count() > 0) {
2380 r->make_pinned();
2381 }
2382 }
2383 }
2384 }
2385
2386 assert_pinned_region_status();
2387 }
2388
2389 #ifdef ASSERT
2390 void ShenandoahHeap::assert_pinned_region_status() {
2391 for (size_t i = 0; i < num_regions(); i++) {
2392 ShenandoahHeapRegion* r = get_region(i);
2393 shenandoah_assert_generations_reconciled();
2394 if (gc_generation()->contains(r)) {
2395 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2396 "Region %zu pinning status is inconsistent", i);
2397 }
2398 }
2399 }
2400 #endif
2401
2402 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2403 return _gc_timer;
2404 }
2405
2406 void ShenandoahHeap::prepare_concurrent_roots() {
2407 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2408 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2409 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2410 set_concurrent_weak_root_in_progress(true);
2411 if (unload_classes()) {
2412 _unloader.prepare();
2413 }
2414 }
2415
2416 void ShenandoahHeap::finish_concurrent_roots() {
2417 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2418 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2419 if (unload_classes()) {
2420 _unloader.finish();
2421 }
2422 }
2423
2424 #ifdef ASSERT
2425 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2426 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2427
2428 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2429 // Use ParallelGCThreads inside safepoints
2430 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2431 ParallelGCThreads, nworkers);
2432 } else {
2433 // Use ConcGCThreads outside safepoints
2434 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2435 ConcGCThreads, nworkers);
2436 }
2437 }
2438 #endif
2439
2440 ShenandoahVerifier* ShenandoahHeap::verifier() {
2441 guarantee(ShenandoahVerify, "Should be enabled");
2442 assert (_verifier != nullptr, "sanity");
2443 return _verifier;
2444 }
2445
2446 template<bool CONCURRENT>
2447 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2448 private:
2449 ShenandoahHeap* _heap;
2450 ShenandoahRegionIterator* _regions;
2451 public:
2452 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2453 WorkerTask("Shenandoah Update References"),
2454 _heap(ShenandoahHeap::heap()),
2455 _regions(regions) {
2456 }
2457
2458 void work(uint worker_id) {
2459 if (CONCURRENT) {
2460 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2461 ShenandoahSuspendibleThreadSetJoiner stsj;
2462 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2463 } else {
2464 ShenandoahParallelWorkerSession worker_session(worker_id);
2465 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2466 }
2467 }
2468
2469 private:
2470 template<class T>
2471 void do_work(uint worker_id) {
2472 if (CONCURRENT && (worker_id == 0)) {
2473 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2474 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2475 size_t cset_regions = _heap->collection_set()->count();
2476
2477 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2478 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2479 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2480 // next GC cycle.
2481 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2482 }
2483 // If !CONCURRENT, there's no value in expanding Mutator free set
2484 T cl;
2485 ShenandoahHeapRegion* r = _regions->next();
2486 while (r != nullptr) {
2487 HeapWord* update_watermark = r->get_update_watermark();
2488 assert (update_watermark >= r->bottom(), "sanity");
2489 if (r->is_active() && !r->is_cset()) {
2490 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2491 if (ShenandoahPacing) {
2492 _heap->pacer()->report_update_refs(pointer_delta(update_watermark, r->bottom()));
2493 }
2494 }
2495 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2496 return;
2497 }
2498 r = _regions->next();
2499 }
2500 }
2501 };
2502
2503 void ShenandoahHeap::update_heap_references(bool concurrent) {
2504 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2505
2506 if (concurrent) {
2507 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2508 workers()->run_task(&task);
2509 } else {
2510 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2511 workers()->run_task(&task);
2512 }
2513 }
2514
2515 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2516 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2517 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2518
2519 {
2520 ShenandoahGCPhase phase(concurrent ?
2521 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2522 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2523
2524 final_update_refs_update_region_states();
2525
2526 assert_pinned_region_status();
2527 }
2528
2529 {
2530 ShenandoahGCPhase phase(concurrent ?
2531 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2532 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2533 trash_cset_regions();
2534 }
2535 }
2536
2537 void ShenandoahHeap::final_update_refs_update_region_states() {
2538 ShenandoahSynchronizePinnedRegionStates cl;
2539 parallel_heap_region_iterate(&cl);
2540 }
2541
2542 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2543 ShenandoahGCPhase phase(concurrent ?
2544 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2545 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2546 ShenandoahHeapLocker locker(lock());
2547 size_t young_cset_regions, old_cset_regions;
2548 size_t first_old_region, last_old_region, old_region_count;
2549 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count);
2550 // If there are no old regions, first_old_region will be greater than last_old_region
2551 assert((first_old_region > last_old_region) ||
2552 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2553 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2554 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu",
2555 old_region_count, first_old_region, last_old_region);
2556
2557 if (mode()->is_generational()) {
2558 #ifdef ASSERT
2559 if (ShenandoahVerify) {
2560 verifier()->verify_before_rebuilding_free_set();
2561 }
2562 #endif
2563
2564 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2565 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2566 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2567 size_t allocation_runway = gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions);
2568 gen_heap->compute_old_generation_balance(allocation_runway, old_cset_regions);
2569
2570 // Total old_available may have been expanded to hold anticipated promotions. We trigger if the fragmented available
2571 // memory represents more than 16 regions worth of data. Note that fragmentation may increase when we promote regular
2572 // regions in place when many of these regular regions have an abundant amount of available memory within them. Fragmentation
2573 // will decrease as promote-by-copy consumes the available memory within these partially consumed regions.
2574 //
2575 // We consider old-gen to have excessive fragmentation if more than 12.5% of old-gen is free memory that resides
2576 // within partially consumed regions of memory.
2577 }
2578 // Rebuild free set based on adjusted generation sizes.
2579 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, old_region_count);
2580
2581 if (mode()->is_generational()) {
2582 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2583 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2584 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2585 }
2586 }
2587
2588 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2589 size_t slice = r->index() / _bitmap_regions_per_slice;
2590
2591 size_t regions_from = _bitmap_regions_per_slice * slice;
2592 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2593 for (size_t g = regions_from; g < regions_to; g++) {
2594 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2595 if (skip_self && g == r->index()) continue;
2596 if (get_region(g)->is_committed()) {
2597 return true;
2598 }
2599 }
2600 return false;
2601 }
2602
2603 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2604 shenandoah_assert_heaplocked();
2605
2606 // Bitmaps in special regions do not need commits
2607 if (_bitmap_region_special) {
2608 return true;
2609 }
2610
2611 if (is_bitmap_slice_committed(r, true)) {
2612 // Some other region from the group is already committed, meaning the bitmap
2613 // slice is already committed, we exit right away.
2614 return true;
2615 }
2616
2617 // Commit the bitmap slice:
2618 size_t slice = r->index() / _bitmap_regions_per_slice;
2619 size_t off = _bitmap_bytes_per_slice * slice;
2620 size_t len = _bitmap_bytes_per_slice;
2621 char* start = (char*) _bitmap_region.start() + off;
2622
2623 if (!os::commit_memory(start, len, false)) {
2624 return false;
2625 }
2626
2627 if (AlwaysPreTouch) {
2628 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2629 }
2630
2631 return true;
2632 }
2633
2634 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2635 shenandoah_assert_heaplocked();
2636
2637 // Bitmaps in special regions do not need uncommits
2638 if (_bitmap_region_special) {
2639 return true;
2640 }
2641
2642 if (is_bitmap_slice_committed(r, true)) {
2643 // Some other region from the group is still committed, meaning the bitmap
2644 // slice should stay committed, exit right away.
2645 return true;
2646 }
2647
2648 // Uncommit the bitmap slice:
2649 size_t slice = r->index() / _bitmap_regions_per_slice;
2650 size_t off = _bitmap_bytes_per_slice * slice;
2651 size_t len = _bitmap_bytes_per_slice;
2652 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2653 return false;
2654 }
2655 return true;
2656 }
2657
2658 void ShenandoahHeap::forbid_uncommit() {
2659 if (_uncommit_thread != nullptr) {
2660 _uncommit_thread->forbid_uncommit();
2661 }
2662 }
2663
2664 void ShenandoahHeap::allow_uncommit() {
2665 if (_uncommit_thread != nullptr) {
2666 _uncommit_thread->allow_uncommit();
2667 }
2668 }
2669
2670 #ifdef ASSERT
2671 bool ShenandoahHeap::is_uncommit_in_progress() {
2672 if (_uncommit_thread != nullptr) {
2673 return _uncommit_thread->is_uncommit_in_progress();
2674 }
2675 return false;
2676 }
2677 #endif
2678
2679 void ShenandoahHeap::safepoint_synchronize_begin() {
2680 StackWatermarkSet::safepoint_synchronize_begin();
2681 SuspendibleThreadSet::synchronize();
2682 }
2683
2684 void ShenandoahHeap::safepoint_synchronize_end() {
2685 SuspendibleThreadSet::desynchronize();
2686 }
2687
2688 void ShenandoahHeap::try_inject_alloc_failure() {
2689 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2690 _inject_alloc_failure.set();
2691 os::naked_short_sleep(1);
2692 if (cancelled_gc()) {
2693 log_info(gc)("Allocation failure was successfully injected");
2694 }
2695 }
2696 }
2697
2698 bool ShenandoahHeap::should_inject_alloc_failure() {
2699 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2700 }
2701
2702 void ShenandoahHeap::initialize_serviceability() {
2703 _memory_pool = new ShenandoahMemoryPool(this);
2704 _cycle_memory_manager.add_pool(_memory_pool);
2705 _stw_memory_manager.add_pool(_memory_pool);
2706 }
2707
2708 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2709 GrowableArray<GCMemoryManager*> memory_managers(2);
2710 memory_managers.append(&_cycle_memory_manager);
2711 memory_managers.append(&_stw_memory_manager);
2712 return memory_managers;
2713 }
2714
2715 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2716 GrowableArray<MemoryPool*> memory_pools(1);
2717 memory_pools.append(_memory_pool);
2718 return memory_pools;
2719 }
2720
2721 MemoryUsage ShenandoahHeap::memory_usage() {
2722 return MemoryUsage(_initial_size, used(), committed(), max_capacity());
2723 }
2724
2725 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2726 _heap(ShenandoahHeap::heap()),
2727 _index(0) {}
2728
2729 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2730 _heap(heap),
2731 _index(0) {}
2732
2733 void ShenandoahRegionIterator::reset() {
2734 _index = 0;
2735 }
2736
2737 bool ShenandoahRegionIterator::has_next() const {
2738 return _index < _heap->num_regions();
2739 }
2740
2741 char ShenandoahHeap::gc_state() const {
2742 return _gc_state.raw_value();
2743 }
2744
2745 bool ShenandoahHeap::is_gc_state(GCState state) const {
2746 // If the global gc state has been changed, but hasn't yet been propagated to all threads, then
2747 // the global gc state is the correct value. Once the gc state has been synchronized with all threads,
2748 // _gc_state_changed will be toggled to false and we need to use the thread local state.
2749 return _gc_state_changed ? _gc_state.is_set(state) : ShenandoahThreadLocalData::is_gc_state(state);
2750 }
2751
2752
2753 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2754 #ifdef ASSERT
2755 assert(_liveness_cache != nullptr, "sanity");
2756 assert(worker_id < _max_workers, "sanity");
2757 for (uint i = 0; i < num_regions(); i++) {
2758 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2759 }
2760 #endif
2761 return _liveness_cache[worker_id];
2762 }
2763
2764 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2765 assert(worker_id < _max_workers, "sanity");
2766 assert(_liveness_cache != nullptr, "sanity");
2767 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2768 for (uint i = 0; i < num_regions(); i++) {
2769 ShenandoahLiveData live = ld[i];
2770 if (live > 0) {
2771 ShenandoahHeapRegion* r = get_region(i);
2772 r->increase_live_data_gc_words(live);
2773 ld[i] = 0;
2774 }
2775 }
2776 }
2777
2778 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2779 if (is_idle()) return false;
2780
2781 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2782 // marking phase.
2783 if (is_concurrent_mark_in_progress() &&
2784 !marking_context()->allocated_after_mark_start(obj)) {
2785 return true;
2786 }
2787
2788 // Can not guarantee obj is deeply good.
2789 if (has_forwarded_objects()) {
2790 return true;
2791 }
2792
2793 return false;
2794 }
2795
2796 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2797 #if INCLUDE_CDS_JAVA_HEAP
2798 // CDS wants a continuous memory range to load a bunch of objects.
2799 // This effectively bypasses normal allocation paths, and requires
2800 // a bit of massaging to unbreak GC invariants.
2801
2802 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
2803
2804 // Easy case: a single regular region, no further adjustments needed.
2805 if (!ShenandoahHeapRegion::requires_humongous(size)) {
2806 return allocate_memory(req);
2807 }
2808
2809 // Hard case: the requested size would cause a humongous allocation.
2810 // We need to make sure it looks like regular allocation to the rest of GC.
2811
2812 // CDS code would guarantee no objects straddle multiple regions, as long as
2813 // regions are as large as MIN_GC_REGION_ALIGNMENT. It is impractical at this
2814 // point to deal with case when Shenandoah runs with smaller regions.
2815 // TODO: This check can be dropped once MIN_GC_REGION_ALIGNMENT agrees more with Shenandoah.
2816 if (ShenandoahHeapRegion::region_size_bytes() < ArchiveHeapWriter::MIN_GC_REGION_ALIGNMENT) {
2817 return nullptr;
2818 }
2819
2820 HeapWord* mem = allocate_memory(req);
2821 size_t start_idx = heap_region_index_containing(mem);
2822 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
2823
2824 // Flip humongous -> regular.
2825 {
2826 ShenandoahHeapLocker locker(lock(), false);
2827 for (size_t c = start_idx; c < start_idx + num_regions; c++) {
2828 get_region(c)->make_regular_bypass();
2829 }
2830 }
2831
2832 return mem;
2833 #else
2834 assert(false, "Archive heap loader should not be available, should not be here");
2835 return nullptr;
2836 #endif // INCLUDE_CDS_JAVA_HEAP
2837 }
2838
2839 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2840 // Nothing to do here, except checking that heap looks fine.
2841 #ifdef ASSERT
2842 HeapWord* start = archive_space.start();
2843 HeapWord* end = archive_space.end();
2844
2845 // No unclaimed space between the objects.
2846 // Objects are properly allocated in correct regions.
2847 HeapWord* cur = start;
2848 while (cur < end) {
2849 oop oop = cast_to_oop(cur);
2850 shenandoah_assert_in_correct_region(nullptr, oop);
2851 cur += oop->size();
2852 }
2853
2854 // No unclaimed tail at the end of archive space.
2855 assert(cur == end,
2856 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2857 p2i(cur), p2i(end));
2858
2859 // Region bounds are good.
2860 ShenandoahHeapRegion* begin_reg = heap_region_containing(start);
2861 ShenandoahHeapRegion* end_reg = heap_region_containing(end);
2862 assert(begin_reg->is_regular(), "Must be");
2863 assert(end_reg->is_regular(), "Must be");
2864 assert(begin_reg->bottom() == start,
2865 "Must agree: archive-space-start: " PTR_FORMAT ", begin-region-bottom: " PTR_FORMAT,
2866 p2i(start), p2i(begin_reg->bottom()));
2867 assert(end_reg->top() == end,
2868 "Must agree: archive-space-end: " PTR_FORMAT ", end-region-top: " PTR_FORMAT,
2869 p2i(end), p2i(end_reg->top()));
2870 #endif
2871 }
2872
2873 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2874 if (!mode()->is_generational()) {
2875 return global_generation();
2876 } else if (affiliation == YOUNG_GENERATION) {
2877 return young_generation();
2878 } else if (affiliation == OLD_GENERATION) {
2879 return old_generation();
2880 }
2881
2882 ShouldNotReachHere();
2883 return nullptr;
2884 }
2885
2886 void ShenandoahHeap::log_heap_status(const char* msg) const {
2887 if (mode()->is_generational()) {
2888 young_generation()->log_status(msg);
2889 old_generation()->log_status(msg);
2890 } else {
2891 global_generation()->log_status(msg);
2892 }
2893 }