1 /*
2 * Copyright (c) 2023, 2025, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
4 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
5 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 *
7 * This code is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 only, as
9 * published by the Free Software Foundation.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27
28 #include "cds/archiveHeapWriter.hpp"
29 #include "classfile/systemDictionary.hpp"
30
31 #include "gc/shared/classUnloadingContext.hpp"
32 #include "gc/shared/fullGCForwarding.hpp"
33 #include "gc/shared/gcArguments.hpp"
34 #include "gc/shared/gcTimer.hpp"
35 #include "gc/shared/gcTraceTime.inline.hpp"
36 #include "gc/shared/locationPrinter.inline.hpp"
37 #include "gc/shared/memAllocator.hpp"
38 #include "gc/shared/plab.hpp"
39 #include "gc/shared/tlab_globals.hpp"
40
41 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
42 #include "gc/shenandoah/heuristics/shenandoahYoungHeuristics.hpp"
43 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
44 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
45 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
46 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
47 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
48 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
49 #include "gc/shenandoah/shenandoahControlThread.hpp"
50 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
51 #include "gc/shenandoah/shenandoahFreeSet.hpp"
52 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp"
53 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
54 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
55 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
56 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
57 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
58 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
59 #include "gc/shenandoah/shenandoahInitLogger.hpp"
60 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
61 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
62 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
63 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
64 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
65 #include "gc/shenandoah/shenandoahPadding.hpp"
66 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
67 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
68 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
69 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
70 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
71 #include "gc/shenandoah/shenandoahSTWMark.hpp"
72 #include "gc/shenandoah/shenandoahUncommitThread.hpp"
73 #include "gc/shenandoah/shenandoahUtils.hpp"
74 #include "gc/shenandoah/shenandoahVerifier.hpp"
75 #include "gc/shenandoah/shenandoahVMOperations.hpp"
76 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
77 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
78 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
79 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
80 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
81 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
82
83 #if INCLUDE_JFR
84 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
85 #endif
86
87 #include "memory/allocation.hpp"
88 #include "memory/allocation.hpp"
89 #include "memory/classLoaderMetaspace.hpp"
90 #include "memory/memoryReserver.hpp"
91 #include "memory/metaspaceUtils.hpp"
92 #include "memory/universe.hpp"
93 #include "nmt/mallocTracker.hpp"
94 #include "nmt/memTracker.hpp"
95 #include "oops/compressedOops.inline.hpp"
96 #include "prims/jvmtiTagMap.hpp"
97 #include "runtime/atomic.hpp"
98 #include "runtime/globals.hpp"
99 #include "runtime/interfaceSupport.inline.hpp"
100 #include "runtime/java.hpp"
101 #include "runtime/orderAccess.hpp"
102 #include "runtime/safepointMechanism.hpp"
103 #include "runtime/stackWatermarkSet.hpp"
104 #include "runtime/threads.hpp"
105 #include "runtime/vmThread.hpp"
106 #include "utilities/globalDefinitions.hpp"
107 #include "utilities/events.hpp"
108 #include "utilities/powerOfTwo.hpp"
109
110 class ShenandoahPretouchHeapTask : public WorkerTask {
111 private:
112 ShenandoahRegionIterator _regions;
113 const size_t _page_size;
114 public:
115 ShenandoahPretouchHeapTask(size_t page_size) :
116 WorkerTask("Shenandoah Pretouch Heap"),
117 _page_size(page_size) {}
118
119 virtual void work(uint worker_id) {
120 ShenandoahHeapRegion* r = _regions.next();
121 while (r != nullptr) {
122 if (r->is_committed()) {
123 os::pretouch_memory(r->bottom(), r->end(), _page_size);
124 }
125 r = _regions.next();
126 }
127 }
128 };
129
130 class ShenandoahPretouchBitmapTask : public WorkerTask {
131 private:
132 ShenandoahRegionIterator _regions;
133 char* _bitmap_base;
134 const size_t _bitmap_size;
135 const size_t _page_size;
136 public:
137 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
138 WorkerTask("Shenandoah Pretouch Bitmap"),
139 _bitmap_base(bitmap_base),
140 _bitmap_size(bitmap_size),
141 _page_size(page_size) {}
142
143 virtual void work(uint worker_id) {
144 ShenandoahHeapRegion* r = _regions.next();
145 while (r != nullptr) {
146 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
147 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
148 assert (end <= _bitmap_size, "end is sane: %zu < %zu", end, _bitmap_size);
149
150 if (r->is_committed()) {
151 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
152 }
153
154 r = _regions.next();
155 }
156 }
157 };
158
159 static ReservedSpace reserve(size_t size, size_t preferred_page_size) {
160 // When a page size is given we don't want to mix large
161 // and normal pages. If the size is not a multiple of the
162 // page size it will be aligned up to achieve this.
163 size_t alignment = os::vm_allocation_granularity();
164 if (preferred_page_size != os::vm_page_size()) {
165 alignment = MAX2(preferred_page_size, alignment);
166 size = align_up(size, alignment);
167 }
168
169 const ReservedSpace reserved = MemoryReserver::reserve(size, alignment, preferred_page_size);
170 if (!reserved.is_reserved()) {
171 vm_exit_during_initialization("Could not reserve space");
172 }
173 return reserved;
174 }
175
176 jint ShenandoahHeap::initialize() {
177 //
178 // Figure out heap sizing
179 //
180
181 size_t init_byte_size = InitialHeapSize;
182 size_t min_byte_size = MinHeapSize;
183 size_t max_byte_size = MaxHeapSize;
184 size_t heap_alignment = HeapAlignment;
185
186 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
187
188 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
189 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
190
191 _num_regions = ShenandoahHeapRegion::region_count();
192 assert(_num_regions == (max_byte_size / reg_size_bytes),
193 "Regions should cover entire heap exactly: %zu != %zu/%zu",
194 _num_regions, max_byte_size, reg_size_bytes);
195
196 size_t num_committed_regions = init_byte_size / reg_size_bytes;
197 num_committed_regions = MIN2(num_committed_regions, _num_regions);
198 assert(num_committed_regions <= _num_regions, "sanity");
199 _initial_size = num_committed_regions * reg_size_bytes;
200
201 size_t num_min_regions = min_byte_size / reg_size_bytes;
202 num_min_regions = MIN2(num_min_regions, _num_regions);
203 assert(num_min_regions <= _num_regions, "sanity");
204 _minimum_size = num_min_regions * reg_size_bytes;
205
206 // Default to max heap size.
207 _soft_max_size = _num_regions * reg_size_bytes;
208
209 _committed = _initial_size;
210
211 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
212 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
213 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
214
215 //
216 // Reserve and commit memory for heap
217 //
218
219 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
220 initialize_reserved_region(heap_rs);
221 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
222 _heap_region_special = heap_rs.special();
223
224 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
225 "Misaligned heap: " PTR_FORMAT, p2i(base()));
226 os::trace_page_sizes_for_requested_size("Heap",
227 max_byte_size, heap_alignment,
228 heap_rs.base(),
229 heap_rs.size(), heap_rs.page_size());
230
231 #if SHENANDOAH_OPTIMIZED_MARKTASK
232 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
233 // Fail if we ever attempt to address more than we can.
234 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
235 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
236 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
237 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
238 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
239 vm_exit_during_initialization("Fatal Error", buf);
240 }
241 #endif
242
243 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
244 if (!_heap_region_special) {
245 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
246 "Cannot commit heap memory");
247 }
248
249 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
250
251 // Now we know the number of regions and heap sizes, initialize the heuristics.
252 initialize_heuristics();
253
254 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
255
256 //
257 // Worker threads must be initialized after the barrier is configured
258 //
259 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
260 if (_workers == nullptr) {
261 vm_exit_during_initialization("Failed necessary allocation.");
262 } else {
263 _workers->initialize_workers();
264 }
265
266 if (ParallelGCThreads > 1) {
267 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
268 _safepoint_workers->initialize_workers();
269 }
270
271 //
272 // Reserve and commit memory for bitmap(s)
273 //
274
275 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
276 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
277
278 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
279
280 guarantee(bitmap_bytes_per_region != 0,
281 "Bitmap bytes per region should not be zero");
282 guarantee(is_power_of_2(bitmap_bytes_per_region),
283 "Bitmap bytes per region should be power of two: %zu", bitmap_bytes_per_region);
284
285 if (bitmap_page_size > bitmap_bytes_per_region) {
286 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
287 _bitmap_bytes_per_slice = bitmap_page_size;
288 } else {
289 _bitmap_regions_per_slice = 1;
290 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
291 }
292
293 guarantee(_bitmap_regions_per_slice >= 1,
294 "Should have at least one region per slice: %zu",
295 _bitmap_regions_per_slice);
296
297 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
298 "Bitmap slices should be page-granular: bps = %zu, page size = %zu",
299 _bitmap_bytes_per_slice, bitmap_page_size);
300
301 ReservedSpace bitmap = reserve(_bitmap_size, bitmap_page_size);
302 os::trace_page_sizes_for_requested_size("Mark Bitmap",
303 bitmap_size_orig, bitmap_page_size,
304 bitmap.base(),
305 bitmap.size(), bitmap.page_size());
306 MemTracker::record_virtual_memory_tag(bitmap.base(), mtGC);
307 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
308 _bitmap_region_special = bitmap.special();
309
310 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
311 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
312 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
313 if (!_bitmap_region_special) {
314 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
315 "Cannot commit bitmap memory");
316 }
317
318 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
319
320 if (ShenandoahVerify) {
321 ReservedSpace verify_bitmap = reserve(_bitmap_size, bitmap_page_size);
322 os::trace_page_sizes_for_requested_size("Verify Bitmap",
323 bitmap_size_orig, bitmap_page_size,
324 verify_bitmap.base(),
325 verify_bitmap.size(), verify_bitmap.page_size());
326 if (!verify_bitmap.special()) {
327 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
328 "Cannot commit verification bitmap memory");
329 }
330 MemTracker::record_virtual_memory_tag(verify_bitmap.base(), mtGC);
331 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
332 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
333 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
334 }
335
336 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
337 size_t aux_bitmap_page_size = bitmap_page_size;
338
339 ReservedSpace aux_bitmap = reserve(_bitmap_size, aux_bitmap_page_size);
340 os::trace_page_sizes_for_requested_size("Aux Bitmap",
341 bitmap_size_orig, aux_bitmap_page_size,
342 aux_bitmap.base(),
343 aux_bitmap.size(), aux_bitmap.page_size());
344 MemTracker::record_virtual_memory_tag(aux_bitmap.base(), mtGC);
345 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
346 _aux_bitmap_region_special = aux_bitmap.special();
347 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
348
349 //
350 // Create regions and region sets
351 //
352 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
353 size_t region_storage_size_orig = region_align * _num_regions;
354 size_t region_storage_size = align_up(region_storage_size_orig,
355 MAX2(region_page_size, os::vm_allocation_granularity()));
356
357 ReservedSpace region_storage = reserve(region_storage_size, region_page_size);
358 os::trace_page_sizes_for_requested_size("Region Storage",
359 region_storage_size_orig, region_page_size,
360 region_storage.base(),
361 region_storage.size(), region_storage.page_size());
362 MemTracker::record_virtual_memory_tag(region_storage.base(), mtGC);
363 if (!region_storage.special()) {
364 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
365 "Cannot commit region memory");
366 }
367
368 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
369 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
370 // If not successful, bite a bullet and allocate at whatever address.
371 {
372 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
373 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
374 const size_t cset_page_size = os::vm_page_size();
375
376 uintptr_t min = round_up_power_of_2(cset_align);
377 uintptr_t max = (1u << 30u);
378 ReservedSpace cset_rs;
379
380 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
381 char* req_addr = (char*)addr;
382 assert(is_aligned(req_addr, cset_align), "Should be aligned");
383 cset_rs = MemoryReserver::reserve(req_addr, cset_size, cset_align, cset_page_size);
384 if (cset_rs.is_reserved()) {
385 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
386 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
387 break;
388 }
389 }
390
391 if (_collection_set == nullptr) {
392 cset_rs = MemoryReserver::reserve(cset_size, cset_align, os::vm_page_size());
393 if (!cset_rs.is_reserved()) {
394 vm_exit_during_initialization("Cannot reserve memory for collection set");
395 }
396
397 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
398 }
399 os::trace_page_sizes_for_requested_size("Collection Set",
400 cset_size, cset_page_size,
401 cset_rs.base(),
402 cset_rs.size(), cset_rs.page_size());
403 }
404
405 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
406 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
407 _free_set = new ShenandoahFreeSet(this, _num_regions);
408
409 {
410 ShenandoahHeapLocker locker(lock());
411
412 for (size_t i = 0; i < _num_regions; i++) {
413 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
414 bool is_committed = i < num_committed_regions;
415 void* loc = region_storage.base() + i * region_align;
416
417 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
418 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
419
420 _marking_context->initialize_top_at_mark_start(r);
421 _regions[i] = r;
422 assert(!collection_set()->is_in(i), "New region should not be in collection set");
423
424 _affiliations[i] = ShenandoahAffiliation::FREE;
425 }
426
427 // Initialize to complete
428 _marking_context->mark_complete();
429 size_t young_cset_regions, old_cset_regions;
430
431 // We are initializing free set. We ignore cset region tallies.
432 size_t first_old, last_old, num_old;
433 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old, last_old, num_old);
434 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, num_old);
435 }
436
437 if (AlwaysPreTouch) {
438 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
439 // before initialize() below zeroes it with initializing thread. For any given region,
440 // we touch the region and the corresponding bitmaps from the same thread.
441 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
442
443 _pretouch_heap_page_size = heap_page_size;
444 _pretouch_bitmap_page_size = bitmap_page_size;
445
446 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
447 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
448
449 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
450 _workers->run_task(&bcl);
451
452 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
453 _workers->run_task(&hcl);
454 }
455
456 //
457 // Initialize the rest of GC subsystems
458 //
459
460 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
461 for (uint worker = 0; worker < _max_workers; worker++) {
462 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
463 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
464 }
465
466 // There should probably be Shenandoah-specific options for these,
467 // just as there are G1-specific options.
468 {
469 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
470 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
471 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
472 }
473
474 _monitoring_support = new ShenandoahMonitoringSupport(this);
475 _phase_timings = new ShenandoahPhaseTimings(max_workers());
476 ShenandoahCodeRoots::initialize();
477
478 if (ShenandoahPacing) {
479 _pacer = new ShenandoahPacer(this);
480 _pacer->setup_for_idle();
481 }
482
483 initialize_controller();
484
485 if (ShenandoahUncommit) {
486 _uncommit_thread = new ShenandoahUncommitThread(this);
487 }
488
489 print_init_logger();
490
491 FullGCForwarding::initialize(_heap_region);
492
493 return JNI_OK;
494 }
495
496 void ShenandoahHeap::initialize_controller() {
497 _control_thread = new ShenandoahControlThread();
498 }
499
500 void ShenandoahHeap::print_init_logger() const {
501 ShenandoahInitLogger::print();
502 }
503
504 void ShenandoahHeap::initialize_mode() {
505 if (ShenandoahGCMode != nullptr) {
506 if (strcmp(ShenandoahGCMode, "satb") == 0) {
507 _gc_mode = new ShenandoahSATBMode();
508 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
509 _gc_mode = new ShenandoahPassiveMode();
510 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
511 _gc_mode = new ShenandoahGenerationalMode();
512 } else {
513 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
514 }
515 } else {
516 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
517 }
518 _gc_mode->initialize_flags();
519 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
520 vm_exit_during_initialization(
521 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
522 _gc_mode->name()));
523 }
524 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
525 vm_exit_during_initialization(
526 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
527 _gc_mode->name()));
528 }
529 }
530
531 void ShenandoahHeap::initialize_heuristics() {
532 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers(), max_capacity(), max_capacity());
533 _global_generation->initialize_heuristics(mode());
534 }
535
536 #ifdef _MSC_VER
537 #pragma warning( push )
538 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
539 #endif
540
541 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
542 CollectedHeap(),
543 _gc_generation(nullptr),
544 _active_generation(nullptr),
545 _initial_size(0),
546 _committed(0),
547 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
548 _workers(nullptr),
549 _safepoint_workers(nullptr),
550 _heap_region_special(false),
551 _num_regions(0),
552 _regions(nullptr),
553 _affiliations(nullptr),
554 _gc_state_changed(false),
555 _gc_no_progress_count(0),
556 _cancel_requested_time(0),
557 _update_refs_iterator(this),
558 _global_generation(nullptr),
559 _control_thread(nullptr),
560 _uncommit_thread(nullptr),
561 _young_generation(nullptr),
562 _old_generation(nullptr),
563 _shenandoah_policy(policy),
564 _gc_mode(nullptr),
565 _free_set(nullptr),
566 _pacer(nullptr),
567 _verifier(nullptr),
568 _phase_timings(nullptr),
569 _monitoring_support(nullptr),
570 _memory_pool(nullptr),
571 _stw_memory_manager("Shenandoah Pauses"),
572 _cycle_memory_manager("Shenandoah Cycles"),
573 _gc_timer(new ConcurrentGCTimer()),
574 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
575 _marking_context(nullptr),
576 _bitmap_size(0),
577 _bitmap_regions_per_slice(0),
578 _bitmap_bytes_per_slice(0),
579 _bitmap_region_special(false),
580 _aux_bitmap_region_special(false),
581 _liveness_cache(nullptr),
582 _collection_set(nullptr)
583 {
584 // Initialize GC mode early, many subsequent initialization procedures depend on it
585 initialize_mode();
586 }
587
588 #ifdef _MSC_VER
589 #pragma warning( pop )
590 #endif
591
592 void ShenandoahHeap::print_on(outputStream* st) const {
593 st->print_cr("Shenandoah Heap");
594 st->print_cr(" %zu%s max, %zu%s soft max, %zu%s committed, %zu%s used",
595 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
596 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
597 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
598 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
599 st->print_cr(" %zu x %zu %s regions",
600 num_regions(),
601 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
602 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
603
604 st->print("Status: ");
605 if (has_forwarded_objects()) st->print("has forwarded objects, ");
606 if (!mode()->is_generational()) {
607 if (is_concurrent_mark_in_progress()) st->print("marking,");
608 } else {
609 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
610 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
611 }
612 if (is_evacuation_in_progress()) st->print("evacuating, ");
613 if (is_update_refs_in_progress()) st->print("updating refs, ");
614 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
615 if (is_full_gc_in_progress()) st->print("full gc, ");
616 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
617 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
618 if (is_concurrent_strong_root_in_progress() &&
619 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
620
621 if (cancelled_gc()) {
622 st->print("cancelled");
623 } else {
624 st->print("not cancelled");
625 }
626 st->cr();
627
628 st->print_cr("Reserved region:");
629 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
630 p2i(reserved_region().start()),
631 p2i(reserved_region().end()));
632
633 ShenandoahCollectionSet* cset = collection_set();
634 st->print_cr("Collection set:");
635 if (cset != nullptr) {
636 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
637 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
638 } else {
639 st->print_cr(" (null)");
640 }
641
642 st->cr();
643 MetaspaceUtils::print_on(st);
644
645 if (Verbose) {
646 st->cr();
647 print_heap_regions_on(st);
648 }
649 }
650
651 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
652 public:
653 void do_thread(Thread* thread) {
654 assert(thread != nullptr, "Sanity");
655 ShenandoahThreadLocalData::initialize_gclab(thread);
656 }
657 };
658
659 void ShenandoahHeap::post_initialize() {
660 CollectedHeap::post_initialize();
661
662 // Schedule periodic task to report on gc thread CPU utilization
663 _mmu_tracker.initialize();
664
665 MutexLocker ml(Threads_lock);
666
667 ShenandoahInitWorkerGCLABClosure init_gclabs;
668 _workers->threads_do(&init_gclabs);
669
670 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
671 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
672 _workers->set_initialize_gclab();
673
674 // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump
675 // during a concurrent evacuation phase.
676 if (_safepoint_workers != nullptr) {
677 _safepoint_workers->threads_do(&init_gclabs);
678 _safepoint_workers->set_initialize_gclab();
679 }
680
681 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
682 }
683
684 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
685 return _global_generation->heuristics();
686 }
687
688 size_t ShenandoahHeap::used() const {
689 return global_generation()->used();
690 }
691
692 size_t ShenandoahHeap::committed() const {
693 return Atomic::load(&_committed);
694 }
695
696 void ShenandoahHeap::increase_committed(size_t bytes) {
697 shenandoah_assert_heaplocked_or_safepoint();
698 _committed += bytes;
699 }
700
701 void ShenandoahHeap::decrease_committed(size_t bytes) {
702 shenandoah_assert_heaplocked_or_safepoint();
703 _committed -= bytes;
704 }
705
706 // For tracking usage based on allocations, it should be the case that:
707 // * The sum of regions::used == heap::used
708 // * The sum of a generation's regions::used == generation::used
709 // * The sum of a generation's humongous regions::free == generation::humongous_waste
710 // These invariants are checked by the verifier on GC safepoints.
711 //
712 // Additional notes:
713 // * When a mutator's allocation request causes a region to be retired, the
714 // free memory left in that region is considered waste. It does not contribute
715 // to the usage, but it _does_ contribute to allocation rate.
716 // * The bottom of a PLAB must be aligned on card size. In some cases this will
717 // require padding in front of the PLAB (a filler object). Because this padding
718 // is included in the region's used memory we include the padding in the usage
719 // accounting as waste.
720 // * Mutator allocations are used to compute an allocation rate. They are also
721 // sent to the Pacer for those purposes.
722 // * There are three sources of waste:
723 // 1. The padding used to align a PLAB on card size
724 // 2. Region's free is less than minimum TLAB size and is retired
725 // 3. The unused portion of memory in the last region of a humongous object
726 void ShenandoahHeap::increase_used(const ShenandoahAllocRequest& req) {
727 size_t actual_bytes = req.actual_size() * HeapWordSize;
728 size_t wasted_bytes = req.waste() * HeapWordSize;
729 ShenandoahGeneration* generation = generation_for(req.affiliation());
730
731 if (req.is_gc_alloc()) {
732 assert(wasted_bytes == 0 || req.type() == ShenandoahAllocRequest::_alloc_plab, "Only PLABs have waste");
733 increase_used(generation, actual_bytes + wasted_bytes);
734 } else {
735 assert(req.is_mutator_alloc(), "Expected mutator alloc here");
736 // padding and actual size both count towards allocation counter
737 generation->increase_allocated(actual_bytes + wasted_bytes);
738
739 // only actual size counts toward usage for mutator allocations
740 increase_used(generation, actual_bytes);
741
742 // notify pacer of both actual size and waste
743 notify_mutator_alloc_words(req.actual_size(), req.waste());
744
745 if (wasted_bytes > 0 && ShenandoahHeapRegion::requires_humongous(req.actual_size())) {
746 increase_humongous_waste(generation,wasted_bytes);
747 }
748 }
749 }
750
751 void ShenandoahHeap::increase_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
752 generation->increase_humongous_waste(bytes);
753 if (!generation->is_global()) {
754 global_generation()->increase_humongous_waste(bytes);
755 }
756 }
757
758 void ShenandoahHeap::decrease_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
759 generation->decrease_humongous_waste(bytes);
760 if (!generation->is_global()) {
761 global_generation()->decrease_humongous_waste(bytes);
762 }
763 }
764
765 void ShenandoahHeap::increase_used(ShenandoahGeneration* generation, size_t bytes) {
766 generation->increase_used(bytes);
767 if (!generation->is_global()) {
768 global_generation()->increase_used(bytes);
769 }
770 }
771
772 void ShenandoahHeap::decrease_used(ShenandoahGeneration* generation, size_t bytes) {
773 generation->decrease_used(bytes);
774 if (!generation->is_global()) {
775 global_generation()->decrease_used(bytes);
776 }
777 }
778
779 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, size_t waste) {
780 if (ShenandoahPacing) {
781 control_thread()->pacing_notify_alloc(words);
782 if (waste > 0) {
783 pacer()->claim_for_alloc<true>(waste);
784 }
785 }
786 }
787
788 size_t ShenandoahHeap::capacity() const {
789 return committed();
790 }
791
792 size_t ShenandoahHeap::max_capacity() const {
793 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
794 }
795
796 size_t ShenandoahHeap::soft_max_capacity() const {
797 size_t v = Atomic::load(&_soft_max_size);
798 assert(min_capacity() <= v && v <= max_capacity(),
799 "Should be in bounds: %zu <= %zu <= %zu",
800 min_capacity(), v, max_capacity());
801 return v;
802 }
803
804 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
805 assert(min_capacity() <= v && v <= max_capacity(),
806 "Should be in bounds: %zu <= %zu <= %zu",
807 min_capacity(), v, max_capacity());
808 Atomic::store(&_soft_max_size, v);
809 }
810
811 size_t ShenandoahHeap::min_capacity() const {
812 return _minimum_size;
813 }
814
815 size_t ShenandoahHeap::initial_capacity() const {
816 return _initial_size;
817 }
818
819 bool ShenandoahHeap::is_in(const void* p) const {
820 if (is_in_reserved(p)) {
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 // Now check if we point to a live section in active region.
827 ShenandoahHeapRegion* r = heap_region_containing(p);
828 return (r->is_active() && p < r->top());
829 } else {
830 return false;
831 }
832 }
833
834 void ShenandoahHeap::notify_soft_max_changed() {
835 if (_uncommit_thread != nullptr) {
836 _uncommit_thread->notify_soft_max_changed();
837 }
838 }
839
840 void ShenandoahHeap::notify_explicit_gc_requested() {
841 if (_uncommit_thread != nullptr) {
842 _uncommit_thread->notify_explicit_gc_requested();
843 }
844 }
845
846 bool ShenandoahHeap::check_soft_max_changed() {
847 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
848 size_t old_soft_max = soft_max_capacity();
849 if (new_soft_max != old_soft_max) {
850 new_soft_max = MAX2(min_capacity(), new_soft_max);
851 new_soft_max = MIN2(max_capacity(), new_soft_max);
852 if (new_soft_max != old_soft_max) {
853 log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s",
854 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
855 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
856 );
857 set_soft_max_capacity(new_soft_max);
858 return true;
859 }
860 }
861 return false;
862 }
863
864 void ShenandoahHeap::notify_heap_changed() {
865 // Update monitoring counters when we took a new region. This amortizes the
866 // update costs on slow path.
867 monitoring_support()->notify_heap_changed();
868 _heap_changed.try_set();
869 }
870
871 void ShenandoahHeap::set_forced_counters_update(bool value) {
872 monitoring_support()->set_forced_counters_update(value);
873 }
874
875 void ShenandoahHeap::handle_force_counters_update() {
876 monitoring_support()->handle_force_counters_update();
877 }
878
879 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
880 // New object should fit the GCLAB size
881 size_t min_size = MAX2(size, PLAB::min_size());
882
883 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
884 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
885
886 new_size = MIN2(new_size, PLAB::max_size());
887 new_size = MAX2(new_size, PLAB::min_size());
888
889 // Record new heuristic value even if we take any shortcut. This captures
890 // the case when moderately-sized objects always take a shortcut. At some point,
891 // heuristics should catch up with them.
892 log_debug(gc, free)("Set new GCLAB size: %zu", new_size);
893 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
894
895 if (new_size < size) {
896 // New size still does not fit the object. Fall back to shared allocation.
897 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
898 log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size);
899 return nullptr;
900 }
901
902 // Retire current GCLAB, and allocate a new one.
903 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
904 gclab->retire();
905
906 size_t actual_size = 0;
907 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
908 if (gclab_buf == nullptr) {
909 return nullptr;
910 }
911
912 assert (size <= actual_size, "allocation should fit");
913
914 // ...and clear or zap just allocated TLAB, if needed.
915 if (ZeroTLAB) {
916 Copy::zero_to_words(gclab_buf, actual_size);
917 } else if (ZapTLAB) {
918 // Skip mangling the space corresponding to the object header to
919 // ensure that the returned space is not considered parsable by
920 // any concurrent GC thread.
921 size_t hdr_size = oopDesc::header_size();
922 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
923 }
924 gclab->set_buf(gclab_buf, actual_size);
925 return gclab->allocate(size);
926 }
927
928 // Called from stubs in JIT code or interpreter
929 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
930 size_t requested_size,
931 size_t* actual_size) {
932 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
933 HeapWord* res = allocate_memory(req);
934 if (res != nullptr) {
935 *actual_size = req.actual_size();
936 } else {
937 *actual_size = 0;
938 }
939 return res;
940 }
941
942 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
943 size_t word_size,
944 size_t* actual_size) {
945 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
946 HeapWord* res = allocate_memory(req);
947 if (res != nullptr) {
948 *actual_size = req.actual_size();
949 } else {
950 *actual_size = 0;
951 }
952 return res;
953 }
954
955 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
956 intptr_t pacer_epoch = 0;
957 bool in_new_region = false;
958 HeapWord* result = nullptr;
959
960 if (req.is_mutator_alloc()) {
961 if (ShenandoahPacing) {
962 pacer()->pace_for_alloc(req.size());
963 pacer_epoch = pacer()->epoch();
964 }
965
966 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
967 result = allocate_memory_under_lock(req, in_new_region);
968 }
969
970 // Check that gc overhead is not exceeded.
971 //
972 // Shenandoah will grind along for quite a while allocating one
973 // object at a time using shared (non-tlab) allocations. This check
974 // is testing that the GC overhead limit has not been exceeded.
975 // This will notify the collector to start a cycle, but will raise
976 // an OOME to the mutator if the last Full GCs have not made progress.
977 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
978 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
979 control_thread()->handle_alloc_failure(req, false);
980 req.set_actual_size(0);
981 return nullptr;
982 }
983
984 if (result == nullptr) {
985 // Block until control thread reacted, then retry allocation.
986 //
987 // It might happen that one of the threads requesting allocation would unblock
988 // way later after GC happened, only to fail the second allocation, because
989 // other threads have already depleted the free storage. In this case, a better
990 // strategy is to try again, until at least one full GC has completed.
991 //
992 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
993 // a) We experienced a GC that had good progress, or
994 // b) We experienced at least one Full GC (whether or not it had good progress)
995
996 size_t original_count = shenandoah_policy()->full_gc_count();
997 while ((result == nullptr) && (original_count == shenandoah_policy()->full_gc_count())) {
998 control_thread()->handle_alloc_failure(req, true);
999 result = allocate_memory_under_lock(req, in_new_region);
1000 }
1001 if (result != nullptr) {
1002 // If our allocation request has been satisifed after it initially failed, we count this as good gc progress
1003 notify_gc_progress();
1004 }
1005 if (log_develop_is_enabled(Debug, gc, alloc)) {
1006 ResourceMark rm;
1007 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu"
1008 ", Original: %zu, Latest: %zu",
1009 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
1010 original_count, get_gc_no_progress_count());
1011 }
1012 }
1013 } else {
1014 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
1015 result = allocate_memory_under_lock(req, in_new_region);
1016 // Do not call handle_alloc_failure() here, because we cannot block.
1017 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1018 }
1019
1020 if (in_new_region) {
1021 notify_heap_changed();
1022 }
1023
1024 if (result == nullptr) {
1025 req.set_actual_size(0);
1026 }
1027
1028 // This is called regardless of the outcome of the allocation to account
1029 // for any waste created by retiring regions with this request.
1030 increase_used(req);
1031
1032 if (result != nullptr) {
1033 size_t requested = req.size();
1034 size_t actual = req.actual_size();
1035
1036 assert (req.is_lab_alloc() || (requested == actual),
1037 "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu",
1038 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
1039
1040 if (req.is_mutator_alloc()) {
1041 // If we requested more than we were granted, give the rest back to pacer.
1042 // This only matters if we are in the same pacing epoch: do not try to unpace
1043 // over the budget for the other phase.
1044 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
1045 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
1046 }
1047 }
1048 }
1049
1050 return result;
1051 }
1052
1053 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1054 // If we are dealing with mutator allocation, then we may need to block for safepoint.
1055 // We cannot block for safepoint for GC allocations, because there is a high chance
1056 // we are already running at safepoint or from stack watermark machinery, and we cannot
1057 // block again.
1058 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1059
1060 // Make sure the old generation has room for either evacuations or promotions before trying to allocate.
1061 if (req.is_old() && !old_generation()->can_allocate(req)) {
1062 return nullptr;
1063 }
1064
1065 // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available
1066 // memory.
1067 HeapWord* result = _free_set->allocate(req, in_new_region);
1068
1069 // Record the plab configuration for this result and register the object.
1070 if (result != nullptr && req.is_old()) {
1071 old_generation()->configure_plab_for_current_thread(req);
1072 if (req.type() == ShenandoahAllocRequest::_alloc_shared_gc) {
1073 // Register the newly allocated object while we're holding the global lock since there's no synchronization
1074 // built in to the implementation of register_object(). There are potential races when multiple independent
1075 // threads are allocating objects, some of which might span the same card region. For example, consider
1076 // a card table's memory region within which three objects are being allocated by three different threads:
1077 //
1078 // objects being "concurrently" allocated:
1079 // [-----a------][-----b-----][--------------c------------------]
1080 // [---- card table memory range --------------]
1081 //
1082 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a
1083 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region.
1084 // Allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region.
1085 // Allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this
1086 // card region.
1087 //
1088 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as
1089 // last-start representing object b while first-start represents object c. This is why we need to require all
1090 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range.
1091 old_generation()->card_scan()->register_object(result);
1092 }
1093 }
1094
1095 return result;
1096 }
1097
1098 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1099 bool* gc_overhead_limit_was_exceeded) {
1100 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1101 return allocate_memory(req);
1102 }
1103
1104 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1105 size_t size,
1106 Metaspace::MetadataType mdtype) {
1107 MetaWord* result;
1108
1109 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1110 ShenandoahHeuristics* h = global_generation()->heuristics();
1111 if (h->can_unload_classes()) {
1112 h->record_metaspace_oom();
1113 }
1114
1115 // Expand and retry allocation
1116 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1117 if (result != nullptr) {
1118 return result;
1119 }
1120
1121 // Start full GC
1122 collect(GCCause::_metadata_GC_clear_soft_refs);
1123
1124 // Retry allocation
1125 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1126 if (result != nullptr) {
1127 return result;
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 // Out of memory
1137 return nullptr;
1138 }
1139
1140 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1141 private:
1142 ShenandoahHeap* const _heap;
1143 Thread* const _thread;
1144 public:
1145 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1146 _heap(heap), _thread(Thread::current()) {}
1147
1148 void do_object(oop p) {
1149 shenandoah_assert_marked(nullptr, p);
1150 if (!p->is_forwarded()) {
1151 _heap->evacuate_object(p, _thread);
1152 }
1153 }
1154 };
1155
1156 class ShenandoahEvacuationTask : public WorkerTask {
1157 private:
1158 ShenandoahHeap* const _sh;
1159 ShenandoahCollectionSet* const _cs;
1160 bool _concurrent;
1161 public:
1162 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1163 ShenandoahCollectionSet* cs,
1164 bool concurrent) :
1165 WorkerTask("Shenandoah Evacuation"),
1166 _sh(sh),
1167 _cs(cs),
1168 _concurrent(concurrent)
1169 {}
1170
1171 void work(uint worker_id) {
1172 if (_concurrent) {
1173 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1174 ShenandoahSuspendibleThreadSetJoiner stsj;
1175 ShenandoahEvacOOMScope oom_evac_scope;
1176 do_work();
1177 } else {
1178 ShenandoahParallelWorkerSession worker_session(worker_id);
1179 ShenandoahEvacOOMScope oom_evac_scope;
1180 do_work();
1181 }
1182 }
1183
1184 private:
1185 void do_work() {
1186 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1187 ShenandoahHeapRegion* r;
1188 while ((r =_cs->claim_next()) != nullptr) {
1189 assert(r->has_live(), "Region %zu should have been reclaimed early", r->index());
1190 _sh->marked_object_iterate(r, &cl);
1191
1192 if (ShenandoahPacing) {
1193 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1194 }
1195
1196 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1197 break;
1198 }
1199 }
1200 }
1201 };
1202
1203 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1204 private:
1205 bool const _resize;
1206 public:
1207 explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1208 void do_thread(Thread* thread) override {
1209 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1210 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1211 gclab->retire();
1212 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1213 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1214 }
1215
1216 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1217 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1218 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1219
1220 // There are two reasons to retire all plabs between old-gen evacuation passes.
1221 // 1. We need to make the plab memory parsable by remembered-set scanning.
1222 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1223 ShenandoahGenerationalHeap::heap()->retire_plab(plab, thread);
1224 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) {
1225 ShenandoahThreadLocalData::set_plab_size(thread, 0);
1226 }
1227 }
1228 }
1229 };
1230
1231 class ShenandoahGCStatePropagator : public ThreadClosure {
1232 public:
1233 explicit ShenandoahGCStatePropagator(char gc_state) : _gc_state(gc_state) {}
1234
1235 void do_thread(Thread* thread) override {
1236 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state);
1237 }
1238 private:
1239 char _gc_state;
1240 };
1241
1242 class ShenandoahPrepareForUpdateRefs : public HandshakeClosure {
1243 public:
1244 explicit ShenandoahPrepareForUpdateRefs(char gc_state) :
1245 HandshakeClosure("Shenandoah Prepare for Update Refs"),
1246 _retire(ResizeTLAB), _propagator(gc_state) {}
1247
1248 void do_thread(Thread* thread) override {
1249 _propagator.do_thread(thread);
1250 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) {
1251 _retire.do_thread(thread);
1252 }
1253 }
1254 private:
1255 ShenandoahRetireGCLABClosure _retire;
1256 ShenandoahGCStatePropagator _propagator;
1257 };
1258
1259 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1260 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1261 workers()->run_task(&task);
1262 }
1263
1264 void ShenandoahHeap::concurrent_prepare_for_update_refs() {
1265 // It's possible that evacuation succeeded, but we could still be cancelled when we get here.
1266 // A cancellation at this point means the degenerated cycle must resume from update-refs.
1267 set_gc_state_concurrent(EVACUATION, false);
1268 set_gc_state_concurrent(WEAK_ROOTS, false);
1269 set_gc_state_concurrent(UPDATE_REFS, true);
1270
1271 // This will propagate the gc state and retire gclabs and plabs for threads that require it.
1272 ShenandoahPrepareForUpdateRefs prepare_for_update_refs(_gc_state.raw_value());
1273
1274 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately.
1275 Threads::non_java_threads_do(&prepare_for_update_refs);
1276
1277 // Now retire gclabs and plabs and propagate gc_state for mutator threads
1278 Handshake::execute(&prepare_for_update_refs);
1279
1280 _update_refs_iterator.reset();
1281 }
1282
1283 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1284 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1285 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
1286 // This thread went through the OOM during evac protocol. It is safe to return
1287 // the forward pointer. It must not attempt to evacuate any other objects.
1288 return ShenandoahBarrierSet::resolve_forwarded(p);
1289 }
1290
1291 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1292
1293 ShenandoahHeapRegion* r = heap_region_containing(p);
1294 assert(!r->is_humongous(), "never evacuate humongous objects");
1295
1296 ShenandoahAffiliation target_gen = r->affiliation();
1297 return try_evacuate_object(p, thread, r, target_gen);
1298 }
1299
1300 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1301 ShenandoahAffiliation target_gen) {
1302 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1303 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1304 bool alloc_from_lab = true;
1305 HeapWord* copy = nullptr;
1306
1307 markWord mark = p->mark();
1308 if (ShenandoahForwarding::is_forwarded(mark)) {
1309 return ShenandoahForwarding::get_forwardee(p);
1310 }
1311 size_t old_size = ShenandoahForwarding::size(p);
1312 size_t size = p->copy_size(old_size, mark);
1313
1314 #ifdef ASSERT
1315 if (ShenandoahOOMDuringEvacALot &&
1316 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1317 copy = nullptr;
1318 } else {
1319 #endif
1320 if (UseTLAB) {
1321 copy = allocate_from_gclab(thread, size);
1322 }
1323 if (copy == nullptr) {
1324 // If we failed to allocate in LAB, we'll try a shared allocation.
1325 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1326 copy = allocate_memory(req);
1327 alloc_from_lab = false;
1328 }
1329 #ifdef ASSERT
1330 }
1331 #endif
1332
1333 if (copy == nullptr) {
1334 control_thread()->handle_alloc_failure_evac(size);
1335
1336 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1337
1338 return ShenandoahBarrierSet::resolve_forwarded(p);
1339 }
1340
1341 // Copy the object:
1342 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, old_size);
1343
1344 // Try to install the new forwarding pointer.
1345 oop copy_val = cast_to_oop(copy);
1346 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1347 if (result == copy_val) {
1348 // Successfully evacuated. Our copy is now the public one!
1349 copy_val->initialize_hash_if_necessary(p);
1350 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1351 shenandoah_assert_correct(nullptr, copy_val);
1352 return copy_val;
1353 } else {
1354 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1355 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1356 // But if it happens to contain references to evacuated regions, those references would
1357 // not get updated for this stale copy during this cycle, and we will crash while scanning
1358 // it the next cycle.
1359 if (alloc_from_lab) {
1360 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1361 // object will overwrite this stale copy, or the filler object on LAB retirement will
1362 // do this.
1363 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1364 } else {
1365 // For non-LAB allocations, we have no way to retract the allocation, and
1366 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1367 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1368 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1369 fill_with_object(copy, size);
1370 shenandoah_assert_correct(nullptr, copy_val);
1371 // For non-LAB allocations, the object has already been registered
1372 }
1373 shenandoah_assert_correct(nullptr, result);
1374 return result;
1375 }
1376 }
1377
1378 void ShenandoahHeap::trash_cset_regions() {
1379 ShenandoahHeapLocker locker(lock());
1380
1381 ShenandoahCollectionSet* set = collection_set();
1382 ShenandoahHeapRegion* r;
1383 set->clear_current_index();
1384 while ((r = set->next()) != nullptr) {
1385 r->make_trash();
1386 }
1387 collection_set()->clear();
1388 }
1389
1390 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1391 st->print_cr("Heap Regions:");
1392 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1393 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1394 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1395 st->print_cr("UWM=update watermark, U=used");
1396 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1397 st->print_cr("S=shared allocs, L=live data");
1398 st->print_cr("CP=critical pins");
1399
1400 for (size_t i = 0; i < num_regions(); i++) {
1401 get_region(i)->print_on(st);
1402 }
1403 }
1404
1405 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1406 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1407
1408 oop humongous_obj = cast_to_oop(start->bottom());
1409 size_t size = humongous_obj->size();
1410 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1411 size_t index = start->index() + required_regions - 1;
1412
1413 assert(!start->has_live(), "liveness must be zero");
1414
1415 for(size_t i = 0; i < required_regions; i++) {
1416 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1417 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1418 ShenandoahHeapRegion* region = get_region(index --);
1419
1420 assert(region->is_humongous(), "expect correct humongous start or continuation");
1421 assert(!region->is_cset(), "Humongous region should not be in collection set");
1422
1423 region->make_trash_immediate();
1424 }
1425 return required_regions;
1426 }
1427
1428 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1429 public:
1430 ShenandoahCheckCleanGCLABClosure() {}
1431 void do_thread(Thread* thread) {
1432 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1433 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1434 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1435
1436 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1437 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1438 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1439 assert(plab->words_remaining() == 0, "PLAB should not need retirement");
1440 }
1441 }
1442 };
1443
1444 void ShenandoahHeap::labs_make_parsable() {
1445 assert(UseTLAB, "Only call with UseTLAB");
1446
1447 ShenandoahRetireGCLABClosure cl(false);
1448
1449 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1450 ThreadLocalAllocBuffer& tlab = t->tlab();
1451 tlab.make_parsable();
1452 cl.do_thread(t);
1453 }
1454
1455 workers()->threads_do(&cl);
1456
1457 if (safepoint_workers() != nullptr) {
1458 safepoint_workers()->threads_do(&cl);
1459 }
1460 }
1461
1462 void ShenandoahHeap::tlabs_retire(bool resize) {
1463 assert(UseTLAB, "Only call with UseTLAB");
1464 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1465
1466 ThreadLocalAllocStats stats;
1467
1468 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1469 ThreadLocalAllocBuffer& tlab = t->tlab();
1470 tlab.retire(&stats);
1471 if (resize) {
1472 tlab.resize();
1473 }
1474 }
1475
1476 stats.publish();
1477
1478 #ifdef ASSERT
1479 ShenandoahCheckCleanGCLABClosure cl;
1480 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1481 cl.do_thread(t);
1482 }
1483 workers()->threads_do(&cl);
1484 #endif
1485 }
1486
1487 void ShenandoahHeap::gclabs_retire(bool resize) {
1488 assert(UseTLAB, "Only call with UseTLAB");
1489 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1490
1491 ShenandoahRetireGCLABClosure cl(resize);
1492 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1493 cl.do_thread(t);
1494 }
1495
1496 workers()->threads_do(&cl);
1497
1498 if (safepoint_workers() != nullptr) {
1499 safepoint_workers()->threads_do(&cl);
1500 }
1501 }
1502
1503 // Returns size in bytes
1504 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1505 // Return the max allowed size, and let the allocation path
1506 // figure out the safe size for current allocation.
1507 return ShenandoahHeapRegion::max_tlab_size_bytes();
1508 }
1509
1510 size_t ShenandoahHeap::max_tlab_size() const {
1511 // Returns size in words
1512 return ShenandoahHeapRegion::max_tlab_size_words();
1513 }
1514
1515 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) {
1516 // These requests are ignored because we can't easily have Shenandoah jump into
1517 // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent
1518 // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly
1519 // on the VM thread, but this would confuse the control thread mightily and doesn't
1520 // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a
1521 // concurrent cycle in the prologue of the heap inspect/dump operation. This is how
1522 // other concurrent collectors in the JVM handle this scenario as well.
1523 assert(Thread::current()->is_VM_thread(), "Should be the VM thread");
1524 guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause");
1525 }
1526
1527 void ShenandoahHeap::collect(GCCause::Cause cause) {
1528 control_thread()->request_gc(cause);
1529 }
1530
1531 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1532 //assert(false, "Shouldn't need to do full collections");
1533 }
1534
1535 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1536 ShenandoahHeapRegion* r = heap_region_containing(addr);
1537 if (r != nullptr) {
1538 return r->block_start(addr);
1539 }
1540 return nullptr;
1541 }
1542
1543 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1544 ShenandoahHeapRegion* r = heap_region_containing(addr);
1545 return r->block_is_obj(addr);
1546 }
1547
1548 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1549 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1550 }
1551
1552 void ShenandoahHeap::prepare_for_verify() {
1553 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1554 labs_make_parsable();
1555 }
1556 }
1557
1558 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1559 if (_shenandoah_policy->is_at_shutdown()) {
1560 return;
1561 }
1562
1563 if (_control_thread != nullptr) {
1564 tcl->do_thread(_control_thread);
1565 }
1566
1567 if (_uncommit_thread != nullptr) {
1568 tcl->do_thread(_uncommit_thread);
1569 }
1570
1571 workers()->threads_do(tcl);
1572 if (_safepoint_workers != nullptr) {
1573 _safepoint_workers->threads_do(tcl);
1574 }
1575 }
1576
1577 void ShenandoahHeap::print_tracing_info() const {
1578 LogTarget(Info, gc, stats) lt;
1579 if (lt.is_enabled()) {
1580 ResourceMark rm;
1581 LogStream ls(lt);
1582
1583 phase_timings()->print_global_on(&ls);
1584
1585 ls.cr();
1586 ls.cr();
1587
1588 shenandoah_policy()->print_gc_stats(&ls);
1589
1590 ls.cr();
1591 ls.cr();
1592 }
1593 }
1594
1595 void ShenandoahHeap::set_gc_generation(ShenandoahGeneration* generation) {
1596 shenandoah_assert_control_or_vm_thread_at_safepoint();
1597 _gc_generation = generation;
1598 }
1599
1600 // Active generation may only be set by the VM thread at a safepoint.
1601 void ShenandoahHeap::set_active_generation() {
1602 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1603 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1604 assert(_gc_generation != nullptr, "Will set _active_generation to nullptr");
1605 _active_generation = _gc_generation;
1606 }
1607
1608 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
1609 shenandoah_policy()->record_collection_cause(cause);
1610
1611 const GCCause::Cause current = gc_cause();
1612 assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s",
1613 GCCause::to_string(current), GCCause::to_string(cause));
1614 assert(_gc_generation == nullptr, "Over-writing _gc_generation");
1615
1616 set_gc_cause(cause);
1617 set_gc_generation(generation);
1618
1619 generation->heuristics()->record_cycle_start();
1620 }
1621
1622 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1623 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1624 assert(_gc_generation != nullptr, "_gc_generation wasn't set");
1625
1626 generation->heuristics()->record_cycle_end();
1627 if (mode()->is_generational() && generation->is_global()) {
1628 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1629 young_generation()->heuristics()->record_cycle_end();
1630 old_generation()->heuristics()->record_cycle_end();
1631 }
1632
1633 set_gc_generation(nullptr);
1634 set_gc_cause(GCCause::_no_gc);
1635 }
1636
1637 void ShenandoahHeap::verify(VerifyOption vo) {
1638 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1639 if (ShenandoahVerify) {
1640 verifier()->verify_generic(vo);
1641 } else {
1642 // TODO: Consider allocating verification bitmaps on demand,
1643 // and turn this on unconditionally.
1644 }
1645 }
1646 }
1647 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1648 return _free_set->capacity();
1649 }
1650
1651 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1652 private:
1653 MarkBitMap* _bitmap;
1654 ShenandoahScanObjectStack* _oop_stack;
1655 ShenandoahHeap* const _heap;
1656 ShenandoahMarkingContext* const _marking_context;
1657
1658 template <class T>
1659 void do_oop_work(T* p) {
1660 T o = RawAccess<>::oop_load(p);
1661 if (!CompressedOops::is_null(o)) {
1662 oop obj = CompressedOops::decode_not_null(o);
1663 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1664 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1665 return;
1666 }
1667 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1668
1669 assert(oopDesc::is_oop(obj), "must be a valid oop");
1670 if (!_bitmap->is_marked(obj)) {
1671 _bitmap->mark(obj);
1672 _oop_stack->push(obj);
1673 }
1674 }
1675 }
1676 public:
1677 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1678 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1679 _marking_context(_heap->marking_context()) {}
1680 void do_oop(oop* p) { do_oop_work(p); }
1681 void do_oop(narrowOop* p) { do_oop_work(p); }
1682 };
1683
1684 /*
1685 * This is public API, used in preparation of object_iterate().
1686 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1687 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1688 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1689 */
1690 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1691 // No-op.
1692 }
1693
1694 /*
1695 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1696 *
1697 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1698 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1699 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1700 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1701 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1702 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1703 * wiped the bitmap in preparation for next marking).
1704 *
1705 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1706 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1707 * is allowed to report dead objects, but is not required to do so.
1708 */
1709 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1710 // Reset bitmap
1711 if (!prepare_aux_bitmap_for_iteration())
1712 return;
1713
1714 ShenandoahScanObjectStack oop_stack;
1715 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1716 // Seed the stack with root scan
1717 scan_roots_for_iteration(&oop_stack, &oops);
1718
1719 // Work through the oop stack to traverse heap
1720 while (! oop_stack.is_empty()) {
1721 oop obj = oop_stack.pop();
1722 assert(oopDesc::is_oop(obj), "must be a valid oop");
1723 cl->do_object(obj);
1724 obj->oop_iterate(&oops);
1725 }
1726
1727 assert(oop_stack.is_empty(), "should be empty");
1728 // Reclaim bitmap
1729 reclaim_aux_bitmap_for_iteration();
1730 }
1731
1732 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1733 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1734
1735 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1736 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1737 return false;
1738 }
1739 // Reset bitmap
1740 _aux_bit_map.clear();
1741 return true;
1742 }
1743
1744 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1745 // Process GC roots according to current GC cycle
1746 // This populates the work stack with initial objects
1747 // It is important to relinquish the associated locks before diving
1748 // into heap dumper
1749 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1750 ShenandoahHeapIterationRootScanner rp(n_workers);
1751 rp.roots_do(oops);
1752 }
1753
1754 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1755 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1756 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1757 }
1758 }
1759
1760 // Closure for parallelly iterate objects
1761 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1762 private:
1763 MarkBitMap* _bitmap;
1764 ShenandoahObjToScanQueue* _queue;
1765 ShenandoahHeap* const _heap;
1766 ShenandoahMarkingContext* const _marking_context;
1767
1768 template <class T>
1769 void do_oop_work(T* p) {
1770 T o = RawAccess<>::oop_load(p);
1771 if (!CompressedOops::is_null(o)) {
1772 oop obj = CompressedOops::decode_not_null(o);
1773 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1774 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1775 return;
1776 }
1777 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1778
1779 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1780 if (_bitmap->par_mark(obj)) {
1781 _queue->push(ShenandoahMarkTask(obj));
1782 }
1783 }
1784 }
1785 public:
1786 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1787 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1788 _marking_context(_heap->marking_context()) {}
1789 void do_oop(oop* p) { do_oop_work(p); }
1790 void do_oop(narrowOop* p) { do_oop_work(p); }
1791 };
1792
1793 // Object iterator for parallel heap iteraion.
1794 // The root scanning phase happenes in construction as a preparation of
1795 // parallel marking queues.
1796 // Every worker processes it's own marking queue. work-stealing is used
1797 // to balance workload.
1798 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1799 private:
1800 uint _num_workers;
1801 bool _init_ready;
1802 MarkBitMap* _aux_bit_map;
1803 ShenandoahHeap* _heap;
1804 ShenandoahScanObjectStack _roots_stack; // global roots stack
1805 ShenandoahObjToScanQueueSet* _task_queues;
1806 public:
1807 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1808 _num_workers(num_workers),
1809 _init_ready(false),
1810 _aux_bit_map(bitmap),
1811 _heap(ShenandoahHeap::heap()) {
1812 // Initialize bitmap
1813 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1814 if (!_init_ready) {
1815 return;
1816 }
1817
1818 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1819 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1820
1821 _init_ready = prepare_worker_queues();
1822 }
1823
1824 ~ShenandoahParallelObjectIterator() {
1825 // Reclaim bitmap
1826 _heap->reclaim_aux_bitmap_for_iteration();
1827 // Reclaim queue for workers
1828 if (_task_queues!= nullptr) {
1829 for (uint i = 0; i < _num_workers; ++i) {
1830 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1831 if (q != nullptr) {
1832 delete q;
1833 _task_queues->register_queue(i, nullptr);
1834 }
1835 }
1836 delete _task_queues;
1837 _task_queues = nullptr;
1838 }
1839 }
1840
1841 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1842 if (_init_ready) {
1843 object_iterate_parallel(cl, worker_id, _task_queues);
1844 }
1845 }
1846
1847 private:
1848 // Divide global root_stack into worker queues
1849 bool prepare_worker_queues() {
1850 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1851 // Initialize queues for every workers
1852 for (uint i = 0; i < _num_workers; ++i) {
1853 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1854 _task_queues->register_queue(i, task_queue);
1855 }
1856 // Divide roots among the workers. Assume that object referencing distribution
1857 // is related with root kind, use round-robin to make every worker have same chance
1858 // to process every kind of roots
1859 size_t roots_num = _roots_stack.size();
1860 if (roots_num == 0) {
1861 // No work to do
1862 return false;
1863 }
1864
1865 for (uint j = 0; j < roots_num; j++) {
1866 uint stack_id = j % _num_workers;
1867 oop obj = _roots_stack.pop();
1868 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1869 }
1870 return true;
1871 }
1872
1873 void object_iterate_parallel(ObjectClosure* cl,
1874 uint worker_id,
1875 ShenandoahObjToScanQueueSet* queue_set) {
1876 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1877 assert(queue_set != nullptr, "task queue must not be null");
1878
1879 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1880 assert(q != nullptr, "object iterate queue must not be null");
1881
1882 ShenandoahMarkTask t;
1883 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1884
1885 // Work through the queue to traverse heap.
1886 // Steal when there is no task in queue.
1887 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1888 oop obj = t.obj();
1889 assert(oopDesc::is_oop(obj), "must be a valid oop");
1890 cl->do_object(obj);
1891 obj->oop_iterate(&oops);
1892 }
1893 assert(q->is_empty(), "should be empty");
1894 }
1895 };
1896
1897 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1898 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1899 }
1900
1901 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1902 void ShenandoahHeap::keep_alive(oop obj) {
1903 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1904 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1905 }
1906 }
1907
1908 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1909 for (size_t i = 0; i < num_regions(); i++) {
1910 ShenandoahHeapRegion* current = get_region(i);
1911 blk->heap_region_do(current);
1912 }
1913 }
1914
1915 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1916 private:
1917 ShenandoahHeap* const _heap;
1918 ShenandoahHeapRegionClosure* const _blk;
1919 size_t const _stride;
1920
1921 shenandoah_padding(0);
1922 volatile size_t _index;
1923 shenandoah_padding(1);
1924
1925 public:
1926 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
1927 WorkerTask("Shenandoah Parallel Region Operation"),
1928 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
1929
1930 void work(uint worker_id) {
1931 ShenandoahParallelWorkerSession worker_session(worker_id);
1932 size_t stride = _stride;
1933
1934 size_t max = _heap->num_regions();
1935 while (Atomic::load(&_index) < max) {
1936 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1937 size_t start = cur;
1938 size_t end = MIN2(cur + stride, max);
1939 if (start >= max) break;
1940
1941 for (size_t i = cur; i < end; i++) {
1942 ShenandoahHeapRegion* current = _heap->get_region(i);
1943 _blk->heap_region_do(current);
1944 }
1945 }
1946 }
1947 };
1948
1949 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1950 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1951 const uint active_workers = workers()->active_workers();
1952 const size_t n_regions = num_regions();
1953 size_t stride = ShenandoahParallelRegionStride;
1954 if (stride == 0 && active_workers > 1) {
1955 // Automatically derive the stride to balance the work between threads
1956 // evenly. Do not try to split work if below the reasonable threshold.
1957 constexpr size_t threshold = 4096;
1958 stride = n_regions <= threshold ?
1959 threshold :
1960 (n_regions + active_workers - 1) / active_workers;
1961 }
1962
1963 if (n_regions > stride && active_workers > 1) {
1964 ShenandoahParallelHeapRegionTask task(blk, stride);
1965 workers()->run_task(&task);
1966 } else {
1967 heap_region_iterate(blk);
1968 }
1969 }
1970
1971 class ShenandoahRendezvousClosure : public HandshakeClosure {
1972 public:
1973 inline ShenandoahRendezvousClosure(const char* name) : HandshakeClosure(name) {}
1974 inline void do_thread(Thread* thread) {}
1975 };
1976
1977 void ShenandoahHeap::rendezvous_threads(const char* name) {
1978 ShenandoahRendezvousClosure cl(name);
1979 Handshake::execute(&cl);
1980 }
1981
1982 void ShenandoahHeap::recycle_trash() {
1983 free_set()->recycle_trash();
1984 }
1985
1986 void ShenandoahHeap::do_class_unloading() {
1987 _unloader.unload();
1988 if (mode()->is_generational()) {
1989 old_generation()->set_parsable(false);
1990 }
1991 }
1992
1993 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1994 // Weak refs processing
1995 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1996 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1997 ShenandoahTimingsTracker t(phase);
1998 ShenandoahGCWorkerPhase worker_phase(phase);
1999 shenandoah_assert_generations_reconciled();
2000 gc_generation()->ref_processor()->process_references(phase, workers(), false /* concurrent */);
2001 }
2002
2003 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
2004 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
2005
2006 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
2007 // make them parsable for update code to work correctly. Plus, we can compute new sizes
2008 // for future GCLABs here.
2009 if (UseTLAB) {
2010 ShenandoahGCPhase phase(concurrent ?
2011 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
2012 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
2013 gclabs_retire(ResizeTLAB);
2014 }
2015
2016 _update_refs_iterator.reset();
2017 }
2018
2019 void ShenandoahHeap::propagate_gc_state_to_all_threads() {
2020 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2021 if (_gc_state_changed) {
2022 ShenandoahGCStatePropagator propagator(_gc_state.raw_value());
2023 Threads::threads_do(&propagator);
2024 _gc_state_changed = false;
2025 }
2026 }
2027
2028 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) {
2029 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
2030 _gc_state.set_cond(mask, value);
2031 _gc_state_changed = true;
2032 }
2033
2034 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) {
2035 _gc_state.set_cond(mask, value);
2036 }
2037
2038 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
2039 uint mask;
2040 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
2041 if (!in_progress && is_concurrent_old_mark_in_progress()) {
2042 assert(mode()->is_generational(), "Only generational GC has old marking");
2043 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
2044 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
2045 mask = YOUNG_MARKING;
2046 } else {
2047 mask = MARKING | YOUNG_MARKING;
2048 }
2049 set_gc_state_at_safepoint(mask, in_progress);
2050 manage_satb_barrier(in_progress);
2051 }
2052
2053 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2054 #ifdef ASSERT
2055 // has_forwarded_objects() iff UPDATE_REFS or EVACUATION
2056 bool has_forwarded = has_forwarded_objects();
2057 bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION);
2058 bool evacuating = _gc_state.is_set(EVACUATION);
2059 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2060 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2061 #endif
2062 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2063 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2064 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2065 set_gc_state_at_safepoint(OLD_MARKING, in_progress);
2066 } else {
2067 set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress);
2068 }
2069 manage_satb_barrier(in_progress);
2070 }
2071
2072 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2073 return old_generation()->is_preparing_for_mark();
2074 }
2075
2076 void ShenandoahHeap::manage_satb_barrier(bool active) {
2077 if (is_concurrent_mark_in_progress()) {
2078 // Ignore request to deactivate barrier while concurrent mark is in progress.
2079 // Do not attempt to re-activate the barrier if it is already active.
2080 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2081 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2082 }
2083 } else {
2084 // No concurrent marking is in progress so honor request to deactivate,
2085 // but only if the barrier is already active.
2086 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2087 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2088 }
2089 }
2090 }
2091
2092 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2093 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2094 set_gc_state_at_safepoint(EVACUATION, in_progress);
2095 }
2096
2097 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2098 if (in_progress) {
2099 _concurrent_strong_root_in_progress.set();
2100 } else {
2101 _concurrent_strong_root_in_progress.unset();
2102 }
2103 }
2104
2105 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2106 set_gc_state_at_safepoint(WEAK_ROOTS, cond);
2107 }
2108
2109 GCTracer* ShenandoahHeap::tracer() {
2110 return shenandoah_policy()->tracer();
2111 }
2112
2113 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2114 return _free_set->used();
2115 }
2116
2117 bool ShenandoahHeap::try_cancel_gc() {
2118 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
2119 return prev == CANCELLABLE;
2120 }
2121
2122 void ShenandoahHeap::cancel_concurrent_mark() {
2123 if (mode()->is_generational()) {
2124 young_generation()->cancel_marking();
2125 old_generation()->cancel_marking();
2126 }
2127
2128 global_generation()->cancel_marking();
2129
2130 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2131 }
2132
2133 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2134 if (try_cancel_gc()) {
2135 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2136 log_info(gc)("%s", msg.buffer());
2137 Events::log(Thread::current(), "%s", msg.buffer());
2138 _cancel_requested_time = os::elapsedTime();
2139 }
2140 }
2141
2142 uint ShenandoahHeap::max_workers() {
2143 return _max_workers;
2144 }
2145
2146 void ShenandoahHeap::stop() {
2147 // The shutdown sequence should be able to terminate when GC is running.
2148
2149 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2150 _shenandoah_policy->record_shutdown();
2151
2152 // Step 0a. Stop reporting on gc thread cpu utilization
2153 mmu_tracker()->stop();
2154
2155 // Step 1. Notify control thread that we are in shutdown.
2156 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
2157 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
2158 control_thread()->prepare_for_graceful_shutdown();
2159
2160 // Step 2. Notify GC workers that we are cancelling GC.
2161 cancel_gc(GCCause::_shenandoah_stop_vm);
2162
2163 // Step 3. Wait until GC worker exits normally.
2164 control_thread()->stop();
2165
2166 // Stop 4. Shutdown uncommit thread.
2167 if (_uncommit_thread != nullptr) {
2168 _uncommit_thread->stop();
2169 }
2170 }
2171
2172 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2173 if (!unload_classes()) return;
2174 ClassUnloadingContext ctx(_workers->active_workers(),
2175 true /* unregister_nmethods_during_purge */,
2176 false /* lock_nmethod_free_separately */);
2177
2178 // Unload classes and purge SystemDictionary.
2179 {
2180 ShenandoahPhaseTimings::Phase phase = full_gc ?
2181 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2182 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2183 ShenandoahIsAliveSelector is_alive;
2184 {
2185 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2186 ShenandoahGCPhase gc_phase(phase);
2187 ShenandoahGCWorkerPhase worker_phase(phase);
2188 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2189
2190 uint num_workers = _workers->active_workers();
2191 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
2192 _workers->run_task(&unlink_task);
2193 }
2194 // Release unloaded nmethods's memory.
2195 ClassUnloadingContext::context()->purge_and_free_nmethods();
2196 }
2197
2198 {
2199 ShenandoahGCPhase phase(full_gc ?
2200 ShenandoahPhaseTimings::full_gc_purge_cldg :
2201 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2202 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2203 }
2204 // Resize and verify metaspace
2205 MetaspaceGC::compute_new_size();
2206 DEBUG_ONLY(MetaspaceUtils::verify();)
2207 }
2208
2209 // Weak roots are either pre-evacuated (final mark) or updated (final update refs),
2210 // so they should not have forwarded oops.
2211 // However, we do need to "null" dead oops in the roots, if can not be done
2212 // in concurrent cycles.
2213 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2214 uint num_workers = _workers->active_workers();
2215 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2216 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2217 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2218 ShenandoahGCPhase phase(timing_phase);
2219 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2220 // Cleanup weak roots
2221 if (has_forwarded_objects()) {
2222 ShenandoahForwardedIsAliveClosure is_alive;
2223 ShenandoahNonConcUpdateRefsClosure keep_alive;
2224 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2225 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2226 _workers->run_task(&cleaning_task);
2227 } else {
2228 ShenandoahIsAliveClosure is_alive;
2229 #ifdef ASSERT
2230 ShenandoahAssertNotForwardedClosure verify_cl;
2231 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2232 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2233 #else
2234 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2235 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2236 #endif
2237 _workers->run_task(&cleaning_task);
2238 }
2239 }
2240
2241 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2242 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2243 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2244 ShenandoahGCPhase phase(full_gc ?
2245 ShenandoahPhaseTimings::full_gc_purge :
2246 ShenandoahPhaseTimings::degen_gc_purge);
2247 stw_weak_refs(full_gc);
2248 stw_process_weak_roots(full_gc);
2249 stw_unload_classes(full_gc);
2250 }
2251
2252 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2253 set_gc_state_at_safepoint(HAS_FORWARDED, cond);
2254 }
2255
2256 void ShenandoahHeap::set_unload_classes(bool uc) {
2257 _unload_classes.set_cond(uc);
2258 }
2259
2260 bool ShenandoahHeap::unload_classes() const {
2261 return _unload_classes.is_set();
2262 }
2263
2264 address ShenandoahHeap::in_cset_fast_test_addr() {
2265 ShenandoahHeap* heap = ShenandoahHeap::heap();
2266 assert(heap->collection_set() != nullptr, "Sanity");
2267 return (address) heap->collection_set()->biased_map_address();
2268 }
2269
2270 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2271 if (mode()->is_generational()) {
2272 young_generation()->reset_bytes_allocated_since_gc_start();
2273 old_generation()->reset_bytes_allocated_since_gc_start();
2274 }
2275
2276 global_generation()->reset_bytes_allocated_since_gc_start();
2277 }
2278
2279 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2280 _degenerated_gc_in_progress.set_cond(in_progress);
2281 }
2282
2283 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2284 _full_gc_in_progress.set_cond(in_progress);
2285 }
2286
2287 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2288 assert (is_full_gc_in_progress(), "should be");
2289 _full_gc_move_in_progress.set_cond(in_progress);
2290 }
2291
2292 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2293 set_gc_state_at_safepoint(UPDATE_REFS, in_progress);
2294 }
2295
2296 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2297 ShenandoahCodeRoots::register_nmethod(nm);
2298 }
2299
2300 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2301 ShenandoahCodeRoots::unregister_nmethod(nm);
2302 }
2303
2304 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2305 heap_region_containing(o)->record_pin();
2306 }
2307
2308 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2309 ShenandoahHeapRegion* r = heap_region_containing(o);
2310 assert(r != nullptr, "Sanity");
2311 assert(r->pin_count() > 0, "Region %zu should have non-zero pins", r->index());
2312 r->record_unpin();
2313 }
2314
2315 void ShenandoahHeap::sync_pinned_region_status() {
2316 ShenandoahHeapLocker locker(lock());
2317
2318 for (size_t i = 0; i < num_regions(); i++) {
2319 ShenandoahHeapRegion *r = get_region(i);
2320 if (r->is_active()) {
2321 if (r->is_pinned()) {
2322 if (r->pin_count() == 0) {
2323 r->make_unpinned();
2324 }
2325 } else {
2326 if (r->pin_count() > 0) {
2327 r->make_pinned();
2328 }
2329 }
2330 }
2331 }
2332
2333 assert_pinned_region_status();
2334 }
2335
2336 #ifdef ASSERT
2337 void ShenandoahHeap::assert_pinned_region_status() {
2338 for (size_t i = 0; i < num_regions(); i++) {
2339 ShenandoahHeapRegion* r = get_region(i);
2340 shenandoah_assert_generations_reconciled();
2341 if (gc_generation()->contains(r)) {
2342 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2343 "Region %zu pinning status is inconsistent", i);
2344 }
2345 }
2346 }
2347 #endif
2348
2349 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2350 return _gc_timer;
2351 }
2352
2353 void ShenandoahHeap::prepare_concurrent_roots() {
2354 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2355 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2356 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2357 set_concurrent_weak_root_in_progress(true);
2358 if (unload_classes()) {
2359 _unloader.prepare();
2360 }
2361 }
2362
2363 void ShenandoahHeap::finish_concurrent_roots() {
2364 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2365 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2366 if (unload_classes()) {
2367 _unloader.finish();
2368 }
2369 }
2370
2371 #ifdef ASSERT
2372 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2373 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2374
2375 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2376 // Use ParallelGCThreads inside safepoints
2377 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2378 ParallelGCThreads, nworkers);
2379 } else {
2380 // Use ConcGCThreads outside safepoints
2381 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2382 ConcGCThreads, nworkers);
2383 }
2384 }
2385 #endif
2386
2387 ShenandoahVerifier* ShenandoahHeap::verifier() {
2388 guarantee(ShenandoahVerify, "Should be enabled");
2389 assert (_verifier != nullptr, "sanity");
2390 return _verifier;
2391 }
2392
2393 template<bool CONCURRENT>
2394 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2395 private:
2396 ShenandoahHeap* _heap;
2397 ShenandoahRegionIterator* _regions;
2398 public:
2399 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2400 WorkerTask("Shenandoah Update References"),
2401 _heap(ShenandoahHeap::heap()),
2402 _regions(regions) {
2403 }
2404
2405 void work(uint worker_id) {
2406 if (CONCURRENT) {
2407 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2408 ShenandoahSuspendibleThreadSetJoiner stsj;
2409 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2410 } else {
2411 ShenandoahParallelWorkerSession worker_session(worker_id);
2412 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2413 }
2414 }
2415
2416 private:
2417 template<class T>
2418 void do_work(uint worker_id) {
2419 if (CONCURRENT && (worker_id == 0)) {
2420 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2421 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2422 size_t cset_regions = _heap->collection_set()->count();
2423
2424 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2425 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2426 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2427 // next GC cycle.
2428 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2429 }
2430 // If !CONCURRENT, there's no value in expanding Mutator free set
2431 T cl;
2432 ShenandoahHeapRegion* r = _regions->next();
2433 while (r != nullptr) {
2434 HeapWord* update_watermark = r->get_update_watermark();
2435 assert (update_watermark >= r->bottom(), "sanity");
2436 if (r->is_active() && !r->is_cset()) {
2437 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2438 if (ShenandoahPacing) {
2439 _heap->pacer()->report_update_refs(pointer_delta(update_watermark, r->bottom()));
2440 }
2441 }
2442 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2443 return;
2444 }
2445 r = _regions->next();
2446 }
2447 }
2448 };
2449
2450 void ShenandoahHeap::update_heap_references(bool concurrent) {
2451 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2452
2453 if (concurrent) {
2454 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2455 workers()->run_task(&task);
2456 } else {
2457 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2458 workers()->run_task(&task);
2459 }
2460 }
2461
2462 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2463 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2464 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2465
2466 {
2467 ShenandoahGCPhase phase(concurrent ?
2468 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2469 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2470
2471 final_update_refs_update_region_states();
2472
2473 assert_pinned_region_status();
2474 }
2475
2476 {
2477 ShenandoahGCPhase phase(concurrent ?
2478 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2479 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2480 trash_cset_regions();
2481 }
2482 }
2483
2484 void ShenandoahHeap::final_update_refs_update_region_states() {
2485 ShenandoahSynchronizePinnedRegionStates cl;
2486 parallel_heap_region_iterate(&cl);
2487 }
2488
2489 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2490 ShenandoahGCPhase phase(concurrent ?
2491 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2492 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2493 ShenandoahHeapLocker locker(lock());
2494 size_t young_cset_regions, old_cset_regions;
2495 size_t first_old_region, last_old_region, old_region_count;
2496 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count);
2497 // If there are no old regions, first_old_region will be greater than last_old_region
2498 assert((first_old_region > last_old_region) ||
2499 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2500 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2501 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu",
2502 old_region_count, first_old_region, last_old_region);
2503
2504 if (mode()->is_generational()) {
2505 #ifdef ASSERT
2506 if (ShenandoahVerify) {
2507 verifier()->verify_before_rebuilding_free_set();
2508 }
2509 #endif
2510
2511 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2512 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2513 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2514 size_t allocation_runway = gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions);
2515 gen_heap->compute_old_generation_balance(allocation_runway, old_cset_regions);
2516
2517 // Total old_available may have been expanded to hold anticipated promotions. We trigger if the fragmented available
2518 // memory represents more than 16 regions worth of data. Note that fragmentation may increase when we promote regular
2519 // regions in place when many of these regular regions have an abundant amount of available memory within them. Fragmentation
2520 // will decrease as promote-by-copy consumes the available memory within these partially consumed regions.
2521 //
2522 // We consider old-gen to have excessive fragmentation if more than 12.5% of old-gen is free memory that resides
2523 // within partially consumed regions of memory.
2524 }
2525 // Rebuild free set based on adjusted generation sizes.
2526 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, old_region_count);
2527
2528 if (mode()->is_generational()) {
2529 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2530 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2531 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2532 }
2533 }
2534
2535 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2536 print_on(st);
2537 st->cr();
2538 print_heap_regions_on(st);
2539 }
2540
2541 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2542 size_t slice = r->index() / _bitmap_regions_per_slice;
2543
2544 size_t regions_from = _bitmap_regions_per_slice * slice;
2545 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2546 for (size_t g = regions_from; g < regions_to; g++) {
2547 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2548 if (skip_self && g == r->index()) continue;
2549 if (get_region(g)->is_committed()) {
2550 return true;
2551 }
2552 }
2553 return false;
2554 }
2555
2556 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2557 shenandoah_assert_heaplocked();
2558
2559 // Bitmaps in special regions do not need commits
2560 if (_bitmap_region_special) {
2561 return true;
2562 }
2563
2564 if (is_bitmap_slice_committed(r, true)) {
2565 // Some other region from the group is already committed, meaning the bitmap
2566 // slice is already committed, we exit right away.
2567 return true;
2568 }
2569
2570 // Commit the bitmap slice:
2571 size_t slice = r->index() / _bitmap_regions_per_slice;
2572 size_t off = _bitmap_bytes_per_slice * slice;
2573 size_t len = _bitmap_bytes_per_slice;
2574 char* start = (char*) _bitmap_region.start() + off;
2575
2576 if (!os::commit_memory(start, len, false)) {
2577 return false;
2578 }
2579
2580 if (AlwaysPreTouch) {
2581 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2582 }
2583
2584 return true;
2585 }
2586
2587 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2588 shenandoah_assert_heaplocked();
2589
2590 // Bitmaps in special regions do not need uncommits
2591 if (_bitmap_region_special) {
2592 return true;
2593 }
2594
2595 if (is_bitmap_slice_committed(r, true)) {
2596 // Some other region from the group is still committed, meaning the bitmap
2597 // slice should stay committed, exit right away.
2598 return true;
2599 }
2600
2601 // Uncommit the bitmap slice:
2602 size_t slice = r->index() / _bitmap_regions_per_slice;
2603 size_t off = _bitmap_bytes_per_slice * slice;
2604 size_t len = _bitmap_bytes_per_slice;
2605 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2606 return false;
2607 }
2608 return true;
2609 }
2610
2611 void ShenandoahHeap::forbid_uncommit() {
2612 if (_uncommit_thread != nullptr) {
2613 _uncommit_thread->forbid_uncommit();
2614 }
2615 }
2616
2617 void ShenandoahHeap::allow_uncommit() {
2618 if (_uncommit_thread != nullptr) {
2619 _uncommit_thread->allow_uncommit();
2620 }
2621 }
2622
2623 #ifdef ASSERT
2624 bool ShenandoahHeap::is_uncommit_in_progress() {
2625 if (_uncommit_thread != nullptr) {
2626 return _uncommit_thread->is_uncommit_in_progress();
2627 }
2628 return false;
2629 }
2630 #endif
2631
2632 void ShenandoahHeap::safepoint_synchronize_begin() {
2633 StackWatermarkSet::safepoint_synchronize_begin();
2634 SuspendibleThreadSet::synchronize();
2635 }
2636
2637 void ShenandoahHeap::safepoint_synchronize_end() {
2638 SuspendibleThreadSet::desynchronize();
2639 }
2640
2641 void ShenandoahHeap::try_inject_alloc_failure() {
2642 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2643 _inject_alloc_failure.set();
2644 os::naked_short_sleep(1);
2645 if (cancelled_gc()) {
2646 log_info(gc)("Allocation failure was successfully injected");
2647 }
2648 }
2649 }
2650
2651 bool ShenandoahHeap::should_inject_alloc_failure() {
2652 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2653 }
2654
2655 void ShenandoahHeap::initialize_serviceability() {
2656 _memory_pool = new ShenandoahMemoryPool(this);
2657 _cycle_memory_manager.add_pool(_memory_pool);
2658 _stw_memory_manager.add_pool(_memory_pool);
2659 }
2660
2661 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2662 GrowableArray<GCMemoryManager*> memory_managers(2);
2663 memory_managers.append(&_cycle_memory_manager);
2664 memory_managers.append(&_stw_memory_manager);
2665 return memory_managers;
2666 }
2667
2668 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2669 GrowableArray<MemoryPool*> memory_pools(1);
2670 memory_pools.append(_memory_pool);
2671 return memory_pools;
2672 }
2673
2674 MemoryUsage ShenandoahHeap::memory_usage() {
2675 return MemoryUsage(_initial_size, used(), committed(), max_capacity());
2676 }
2677
2678 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2679 _heap(ShenandoahHeap::heap()),
2680 _index(0) {}
2681
2682 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2683 _heap(heap),
2684 _index(0) {}
2685
2686 void ShenandoahRegionIterator::reset() {
2687 _index = 0;
2688 }
2689
2690 bool ShenandoahRegionIterator::has_next() const {
2691 return _index < _heap->num_regions();
2692 }
2693
2694 char ShenandoahHeap::gc_state() const {
2695 return _gc_state.raw_value();
2696 }
2697
2698 bool ShenandoahHeap::is_gc_state(GCState state) const {
2699 // If the global gc state has been changed, but hasn't yet been propagated to all threads, then
2700 // the global gc state is the correct value. Once the gc state has been synchronized with all threads,
2701 // _gc_state_changed will be toggled to false and we need to use the thread local state.
2702 return _gc_state_changed ? _gc_state.is_set(state) : ShenandoahThreadLocalData::is_gc_state(state);
2703 }
2704
2705
2706 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2707 #ifdef ASSERT
2708 assert(_liveness_cache != nullptr, "sanity");
2709 assert(worker_id < _max_workers, "sanity");
2710 for (uint i = 0; i < num_regions(); i++) {
2711 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2712 }
2713 #endif
2714 return _liveness_cache[worker_id];
2715 }
2716
2717 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2718 assert(worker_id < _max_workers, "sanity");
2719 assert(_liveness_cache != nullptr, "sanity");
2720 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2721 for (uint i = 0; i < num_regions(); i++) {
2722 ShenandoahLiveData live = ld[i];
2723 if (live > 0) {
2724 ShenandoahHeapRegion* r = get_region(i);
2725 r->increase_live_data_gc_words(live);
2726 ld[i] = 0;
2727 }
2728 }
2729 }
2730
2731 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2732 if (is_idle()) return false;
2733
2734 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2735 // marking phase.
2736 if (is_concurrent_mark_in_progress() &&
2737 !marking_context()->allocated_after_mark_start(obj)) {
2738 return true;
2739 }
2740
2741 // Can not guarantee obj is deeply good.
2742 if (has_forwarded_objects()) {
2743 return true;
2744 }
2745
2746 return false;
2747 }
2748
2749 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2750 #if INCLUDE_CDS_JAVA_HEAP
2751 // CDS wants a continuous memory range to load a bunch of objects.
2752 // This effectively bypasses normal allocation paths, and requires
2753 // a bit of massaging to unbreak GC invariants.
2754
2755 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
2756
2757 // Easy case: a single regular region, no further adjustments needed.
2758 if (!ShenandoahHeapRegion::requires_humongous(size)) {
2759 return allocate_memory(req);
2760 }
2761
2762 // Hard case: the requested size would cause a humongous allocation.
2763 // We need to make sure it looks like regular allocation to the rest of GC.
2764
2765 // CDS code would guarantee no objects straddle multiple regions, as long as
2766 // regions are as large as MIN_GC_REGION_ALIGNMENT. It is impractical at this
2767 // point to deal with case when Shenandoah runs with smaller regions.
2768 // TODO: This check can be dropped once MIN_GC_REGION_ALIGNMENT agrees more with Shenandoah.
2769 if (ShenandoahHeapRegion::region_size_bytes() < ArchiveHeapWriter::MIN_GC_REGION_ALIGNMENT) {
2770 return nullptr;
2771 }
2772
2773 HeapWord* mem = allocate_memory(req);
2774 size_t start_idx = heap_region_index_containing(mem);
2775 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
2776
2777 // Flip humongous -> regular.
2778 {
2779 ShenandoahHeapLocker locker(lock(), false);
2780 for (size_t c = start_idx; c < start_idx + num_regions; c++) {
2781 get_region(c)->make_regular_bypass();
2782 }
2783 }
2784
2785 return mem;
2786 #else
2787 assert(false, "Archive heap loader should not be available, should not be here");
2788 return nullptr;
2789 #endif // INCLUDE_CDS_JAVA_HEAP
2790 }
2791
2792 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2793 // Nothing to do here, except checking that heap looks fine.
2794 #ifdef ASSERT
2795 HeapWord* start = archive_space.start();
2796 HeapWord* end = archive_space.end();
2797
2798 // No unclaimed space between the objects.
2799 // Objects are properly allocated in correct regions.
2800 HeapWord* cur = start;
2801 while (cur < end) {
2802 oop oop = cast_to_oop(cur);
2803 shenandoah_assert_in_correct_region(nullptr, oop);
2804 cur += oop->size();
2805 }
2806
2807 // No unclaimed tail at the end of archive space.
2808 assert(cur == end,
2809 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2810 p2i(cur), p2i(end));
2811
2812 // Region bounds are good.
2813 ShenandoahHeapRegion* begin_reg = heap_region_containing(start);
2814 ShenandoahHeapRegion* end_reg = heap_region_containing(end);
2815 assert(begin_reg->is_regular(), "Must be");
2816 assert(end_reg->is_regular(), "Must be");
2817 assert(begin_reg->bottom() == start,
2818 "Must agree: archive-space-start: " PTR_FORMAT ", begin-region-bottom: " PTR_FORMAT,
2819 p2i(start), p2i(begin_reg->bottom()));
2820 assert(end_reg->top() == end,
2821 "Must agree: archive-space-end: " PTR_FORMAT ", end-region-top: " PTR_FORMAT,
2822 p2i(end), p2i(end_reg->top()));
2823 #endif
2824 }
2825
2826 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2827 if (!mode()->is_generational()) {
2828 return global_generation();
2829 } else if (affiliation == YOUNG_GENERATION) {
2830 return young_generation();
2831 } else if (affiliation == OLD_GENERATION) {
2832 return old_generation();
2833 }
2834
2835 ShouldNotReachHere();
2836 return nullptr;
2837 }
2838
2839 void ShenandoahHeap::log_heap_status(const char* msg) const {
2840 if (mode()->is_generational()) {
2841 young_generation()->log_status(msg);
2842 old_generation()->log_status(msg);
2843 } else {
2844 global_generation()->log_status(msg);
2845 }
2846 }