1 /*
2 * Copyright (c) 2023, 2024, 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 #include "precompiled.hpp"
28
29 #include "cds/archiveHeapWriter.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "code/codeCache.hpp"
32
33 #include "gc/shared/classUnloadingContext.hpp"
34 #include "gc/shared/fullGCForwarding.hpp"
35 #include "gc/shared/gcArguments.hpp"
36 #include "gc/shared/gcTimer.hpp"
37 #include "gc/shared/gcTraceTime.inline.hpp"
38 #include "gc/shared/locationPrinter.inline.hpp"
39 #include "gc/shared/memAllocator.hpp"
40 #include "gc/shared/plab.hpp"
41 #include "gc/shared/tlab_globals.hpp"
42
43 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
44 #include "gc/shenandoah/heuristics/shenandoahYoungHeuristics.hpp"
45 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
46 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
47 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
48 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
49 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
50 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
51 #include "gc/shenandoah/shenandoahControlThread.hpp"
52 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
53 #include "gc/shenandoah/shenandoahFreeSet.hpp"
54 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp"
55 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
56 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
57 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
58 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
59 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
60 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
61 #include "gc/shenandoah/shenandoahInitLogger.hpp"
62 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
63 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
64 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
65 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
66 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
67 #include "gc/shenandoah/shenandoahPadding.hpp"
68 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
69 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
70 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
71 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
72 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
73 #include "gc/shenandoah/shenandoahSTWMark.hpp"
74 #include "gc/shenandoah/shenandoahUncommitThread.hpp"
75 #include "gc/shenandoah/shenandoahUtils.hpp"
76 #include "gc/shenandoah/shenandoahVerifier.hpp"
77 #include "gc/shenandoah/shenandoahVMOperations.hpp"
78 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
79 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
80 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
81 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
82 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
83 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
84
85 #if INCLUDE_JFR
86 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
87 #endif
88
89
90 #include "memory/allocation.hpp"
91 #include "memory/classLoaderMetaspace.hpp"
92 #include "memory/metaspaceUtils.hpp"
93 #include "memory/universe.hpp"
94 #include "nmt/mallocTracker.hpp"
95 #include "nmt/memTracker.hpp"
96 #include "oops/compressedOops.inline.hpp"
97 #include "prims/jvmtiTagMap.hpp"
98 #include "runtime/atomic.hpp"
99 #include "runtime/globals.hpp"
100 #include "runtime/interfaceSupport.inline.hpp"
101 #include "runtime/java.hpp"
102 #include "runtime/orderAccess.hpp"
103 #include "runtime/safepointMechanism.hpp"
104 #include "runtime/stackWatermarkSet.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: " SIZE_FORMAT " < " SIZE_FORMAT, 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 jint ShenandoahHeap::initialize() {
160 //
161 // Figure out heap sizing
162 //
163
164 size_t init_byte_size = InitialHeapSize;
165 size_t min_byte_size = MinHeapSize;
166 size_t max_byte_size = MaxHeapSize;
167 size_t heap_alignment = HeapAlignment;
168
169 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
170
171 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
172 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
173
174 _num_regions = ShenandoahHeapRegion::region_count();
175 assert(_num_regions == (max_byte_size / reg_size_bytes),
176 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
177 _num_regions, max_byte_size, reg_size_bytes);
178
179 size_t num_committed_regions = init_byte_size / reg_size_bytes;
180 num_committed_regions = MIN2(num_committed_regions, _num_regions);
181 assert(num_committed_regions <= _num_regions, "sanity");
182 _initial_size = num_committed_regions * reg_size_bytes;
183
184 size_t num_min_regions = min_byte_size / reg_size_bytes;
185 num_min_regions = MIN2(num_min_regions, _num_regions);
186 assert(num_min_regions <= _num_regions, "sanity");
187 _minimum_size = num_min_regions * reg_size_bytes;
188
189 // Default to max heap size.
190 _soft_max_size = _num_regions * reg_size_bytes;
191
192 _committed = _initial_size;
193
194 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
195 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
196 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
197
198 //
199 // Reserve and commit memory for heap
200 //
201
202 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
203 initialize_reserved_region(heap_rs);
204 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
205 _heap_region_special = heap_rs.special();
206
207 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
208 "Misaligned heap: " PTR_FORMAT, p2i(base()));
209 os::trace_page_sizes_for_requested_size("Heap",
210 max_byte_size, heap_alignment,
211 heap_rs.base(),
212 heap_rs.size(), heap_rs.page_size());
213
214 #if SHENANDOAH_OPTIMIZED_MARKTASK
215 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
216 // Fail if we ever attempt to address more than we can.
217 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
218 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
219 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
220 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
221 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
222 vm_exit_during_initialization("Fatal Error", buf);
223 }
224 #endif
225
226 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
227 if (!_heap_region_special) {
228 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
229 "Cannot commit heap memory");
230 }
231
232 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
233
234 // Now we know the number of regions and heap sizes, initialize the heuristics.
235 initialize_heuristics();
236
237 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
238
239 //
240 // Worker threads must be initialized after the barrier is configured
241 //
242 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
243 if (_workers == nullptr) {
244 vm_exit_during_initialization("Failed necessary allocation.");
245 } else {
246 _workers->initialize_workers();
247 }
248
249 if (ParallelGCThreads > 1) {
250 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
251 _safepoint_workers->initialize_workers();
252 }
253
254 //
255 // Reserve and commit memory for bitmap(s)
256 //
257
258 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
259 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
260
261 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
262
263 guarantee(bitmap_bytes_per_region != 0,
264 "Bitmap bytes per region should not be zero");
265 guarantee(is_power_of_2(bitmap_bytes_per_region),
266 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
267
268 if (bitmap_page_size > bitmap_bytes_per_region) {
269 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
270 _bitmap_bytes_per_slice = bitmap_page_size;
271 } else {
272 _bitmap_regions_per_slice = 1;
273 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
274 }
275
276 guarantee(_bitmap_regions_per_slice >= 1,
277 "Should have at least one region per slice: " SIZE_FORMAT,
278 _bitmap_regions_per_slice);
279
280 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
281 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
282 _bitmap_bytes_per_slice, bitmap_page_size);
283
284 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
285 os::trace_page_sizes_for_requested_size("Mark Bitmap",
286 bitmap_size_orig, bitmap_page_size,
287 bitmap.base(),
288 bitmap.size(), bitmap.page_size());
289 MemTracker::record_virtual_memory_tag(bitmap.base(), mtGC);
290 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
291 _bitmap_region_special = bitmap.special();
292
293 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
294 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
295 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
296 if (!_bitmap_region_special) {
297 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
298 "Cannot commit bitmap memory");
299 }
300
301 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
302
303 if (ShenandoahVerify) {
304 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
305 os::trace_page_sizes_for_requested_size("Verify Bitmap",
306 bitmap_size_orig, bitmap_page_size,
307 verify_bitmap.base(),
308 verify_bitmap.size(), verify_bitmap.page_size());
309 if (!verify_bitmap.special()) {
310 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
311 "Cannot commit verification bitmap memory");
312 }
313 MemTracker::record_virtual_memory_tag(verify_bitmap.base(), mtGC);
314 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
315 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
316 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
317 }
318
319 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
320 size_t aux_bitmap_page_size = bitmap_page_size;
321
322 ReservedSpace aux_bitmap(_bitmap_size, aux_bitmap_page_size);
323 os::trace_page_sizes_for_requested_size("Aux Bitmap",
324 bitmap_size_orig, aux_bitmap_page_size,
325 aux_bitmap.base(),
326 aux_bitmap.size(), aux_bitmap.page_size());
327 MemTracker::record_virtual_memory_tag(aux_bitmap.base(), mtGC);
328 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
329 _aux_bitmap_region_special = aux_bitmap.special();
330 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
331
332 //
333 // Create regions and region sets
334 //
335 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
336 size_t region_storage_size_orig = region_align * _num_regions;
337 size_t region_storage_size = align_up(region_storage_size_orig,
338 MAX2(region_page_size, os::vm_allocation_granularity()));
339
340 ReservedSpace region_storage(region_storage_size, region_page_size);
341 os::trace_page_sizes_for_requested_size("Region Storage",
342 region_storage_size_orig, region_page_size,
343 region_storage.base(),
344 region_storage.size(), region_storage.page_size());
345 MemTracker::record_virtual_memory_tag(region_storage.base(), mtGC);
346 if (!region_storage.special()) {
347 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
348 "Cannot commit region memory");
349 }
350
351 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
352 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
353 // If not successful, bite a bullet and allocate at whatever address.
354 {
355 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
356 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
357 const size_t cset_page_size = os::vm_page_size();
358
359 uintptr_t min = round_up_power_of_2(cset_align);
360 uintptr_t max = (1u << 30u);
361 ReservedSpace cset_rs;
362
363 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
364 char* req_addr = (char*)addr;
365 assert(is_aligned(req_addr, cset_align), "Should be aligned");
366 cset_rs = ReservedSpace(cset_size, cset_align, cset_page_size, req_addr);
367 if (cset_rs.is_reserved()) {
368 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
369 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
370 break;
371 }
372 }
373
374 if (_collection_set == nullptr) {
375 cset_rs = ReservedSpace(cset_size, cset_align, os::vm_page_size());
376 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
377 }
378 os::trace_page_sizes_for_requested_size("Collection Set",
379 cset_size, cset_page_size,
380 cset_rs.base(),
381 cset_rs.size(), cset_rs.page_size());
382 }
383
384 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
385 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
386 _free_set = new ShenandoahFreeSet(this, _num_regions);
387
388 {
389 ShenandoahHeapLocker locker(lock());
390
391 for (size_t i = 0; i < _num_regions; i++) {
392 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
393 bool is_committed = i < num_committed_regions;
394 void* loc = region_storage.base() + i * region_align;
395
396 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
397 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
398
399 _marking_context->initialize_top_at_mark_start(r);
400 _regions[i] = r;
401 assert(!collection_set()->is_in(i), "New region should not be in collection set");
402
403 _affiliations[i] = ShenandoahAffiliation::FREE;
404 }
405
406 // Initialize to complete
407 _marking_context->mark_complete();
408 size_t young_cset_regions, old_cset_regions;
409
410 // We are initializing free set. We ignore cset region tallies.
411 size_t first_old, last_old, num_old;
412 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old, last_old, num_old);
413 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, num_old);
414 }
415
416 if (AlwaysPreTouch) {
417 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
418 // before initialize() below zeroes it with initializing thread. For any given region,
419 // we touch the region and the corresponding bitmaps from the same thread.
420 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
421
422 _pretouch_heap_page_size = heap_page_size;
423 _pretouch_bitmap_page_size = bitmap_page_size;
424
425 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
426 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
427
428 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
429 _workers->run_task(&bcl);
430
431 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
432 _workers->run_task(&hcl);
433 }
434
435 //
436 // Initialize the rest of GC subsystems
437 //
438
439 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
440 for (uint worker = 0; worker < _max_workers; worker++) {
441 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
442 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
443 }
444
445 // There should probably be Shenandoah-specific options for these,
446 // just as there are G1-specific options.
447 {
448 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
449 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
450 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
451 }
452
453 _monitoring_support = new ShenandoahMonitoringSupport(this);
454 _phase_timings = new ShenandoahPhaseTimings(max_workers());
455 ShenandoahCodeRoots::initialize();
456
457 if (ShenandoahPacing) {
458 _pacer = new ShenandoahPacer(this);
459 _pacer->setup_for_idle();
460 }
461
462 initialize_controller();
463
464 if (ShenandoahUncommit) {
465 _uncommit_thread = new ShenandoahUncommitThread(this);
466 }
467
468 print_init_logger();
469
470 FullGCForwarding::initialize(_heap_region);
471
472 return JNI_OK;
473 }
474
475 void ShenandoahHeap::initialize_controller() {
476 _control_thread = new ShenandoahControlThread();
477 }
478
479 void ShenandoahHeap::print_init_logger() const {
480 ShenandoahInitLogger::print();
481 }
482
483 void ShenandoahHeap::initialize_mode() {
484 if (ShenandoahGCMode != nullptr) {
485 if (strcmp(ShenandoahGCMode, "satb") == 0) {
486 _gc_mode = new ShenandoahSATBMode();
487 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
488 _gc_mode = new ShenandoahPassiveMode();
489 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
490 _gc_mode = new ShenandoahGenerationalMode();
491 } else {
492 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
493 }
494 } else {
495 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
496 }
497 _gc_mode->initialize_flags();
498 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
499 vm_exit_during_initialization(
500 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
501 _gc_mode->name()));
502 }
503 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
504 vm_exit_during_initialization(
505 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
506 _gc_mode->name()));
507 }
508 }
509
510 void ShenandoahHeap::initialize_heuristics() {
511 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers(), max_capacity(), max_capacity());
512 _global_generation->initialize_heuristics(mode());
513 }
514
515 #ifdef _MSC_VER
516 #pragma warning( push )
517 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
518 #endif
519
520 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
521 CollectedHeap(),
522 _gc_generation(nullptr),
523 _active_generation(nullptr),
524 _initial_size(0),
525 _committed(0),
526 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
527 _workers(nullptr),
528 _safepoint_workers(nullptr),
529 _heap_region_special(false),
530 _num_regions(0),
531 _regions(nullptr),
532 _affiliations(nullptr),
533 _gc_state_changed(false),
534 _gc_no_progress_count(0),
535 _cancel_requested_time(0),
536 _update_refs_iterator(this),
537 _global_generation(nullptr),
538 _control_thread(nullptr),
539 _uncommit_thread(nullptr),
540 _young_generation(nullptr),
541 _old_generation(nullptr),
542 _shenandoah_policy(policy),
543 _gc_mode(nullptr),
544 _free_set(nullptr),
545 _pacer(nullptr),
546 _verifier(nullptr),
547 _phase_timings(nullptr),
548 _mmu_tracker(),
549 _monitoring_support(nullptr),
550 _memory_pool(nullptr),
551 _stw_memory_manager("Shenandoah Pauses"),
552 _cycle_memory_manager("Shenandoah Cycles"),
553 _gc_timer(new ConcurrentGCTimer()),
554 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
555 _marking_context(nullptr),
556 _bitmap_size(0),
557 _bitmap_regions_per_slice(0),
558 _bitmap_bytes_per_slice(0),
559 _bitmap_region_special(false),
560 _aux_bitmap_region_special(false),
561 _liveness_cache(nullptr),
562 _collection_set(nullptr)
563 {
564 // Initialize GC mode early, many subsequent initialization procedures depend on it
565 initialize_mode();
566 }
567
568 #ifdef _MSC_VER
569 #pragma warning( pop )
570 #endif
571
572 void ShenandoahHeap::print_on(outputStream* st) const {
573 st->print_cr("Shenandoah Heap");
574 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
575 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
576 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
577 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
578 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
579 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
580 num_regions(),
581 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
582 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
583
584 st->print("Status: ");
585 if (has_forwarded_objects()) st->print("has forwarded objects, ");
586 if (!mode()->is_generational()) {
587 if (is_concurrent_mark_in_progress()) st->print("marking,");
588 } else {
589 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
590 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
591 }
592 if (is_evacuation_in_progress()) st->print("evacuating, ");
593 if (is_update_refs_in_progress()) st->print("updating refs, ");
594 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
595 if (is_full_gc_in_progress()) st->print("full gc, ");
596 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
597 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
598 if (is_concurrent_strong_root_in_progress() &&
599 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
600
601 if (cancelled_gc()) {
602 st->print("cancelled");
603 } else {
604 st->print("not cancelled");
605 }
606 st->cr();
607
608 st->print_cr("Reserved region:");
609 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
610 p2i(reserved_region().start()),
611 p2i(reserved_region().end()));
612
613 ShenandoahCollectionSet* cset = collection_set();
614 st->print_cr("Collection set:");
615 if (cset != nullptr) {
616 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
617 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
618 } else {
619 st->print_cr(" (null)");
620 }
621
622 st->cr();
623 MetaspaceUtils::print_on(st);
624
625 if (Verbose) {
626 st->cr();
627 print_heap_regions_on(st);
628 }
629 }
630
631 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
632 public:
633 void do_thread(Thread* thread) {
634 assert(thread != nullptr, "Sanity");
635 assert(thread->is_Worker_thread(), "Only worker thread expected");
636 ShenandoahThreadLocalData::initialize_gclab(thread);
637 }
638 };
639
640 void ShenandoahHeap::post_initialize() {
641 CollectedHeap::post_initialize();
642 _mmu_tracker.initialize();
643
644 MutexLocker ml(Threads_lock);
645
646 ShenandoahInitWorkerGCLABClosure init_gclabs;
647 _workers->threads_do(&init_gclabs);
648
649 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
650 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
651 _workers->set_initialize_gclab();
652 if (_safepoint_workers != nullptr) {
653 _safepoint_workers->threads_do(&init_gclabs);
654 _safepoint_workers->set_initialize_gclab();
655 }
656
657 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
658 }
659
660 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
661 return _global_generation->heuristics();
662 }
663
664 size_t ShenandoahHeap::used() const {
665 return global_generation()->used();
666 }
667
668 size_t ShenandoahHeap::committed() const {
669 return Atomic::load(&_committed);
670 }
671
672 void ShenandoahHeap::increase_committed(size_t bytes) {
673 shenandoah_assert_heaplocked_or_safepoint();
674 _committed += bytes;
675 }
676
677 void ShenandoahHeap::decrease_committed(size_t bytes) {
678 shenandoah_assert_heaplocked_or_safepoint();
679 _committed -= bytes;
680 }
681
682 // For tracking usage based on allocations, it should be the case that:
683 // * The sum of regions::used == heap::used
684 // * The sum of a generation's regions::used == generation::used
685 // * The sum of a generation's humongous regions::free == generation::humongous_waste
686 // These invariants are checked by the verifier on GC safepoints.
687 //
688 // Additional notes:
689 // * When a mutator's allocation request causes a region to be retired, the
690 // free memory left in that region is considered waste. It does not contribute
691 // to the usage, but it _does_ contribute to allocation rate.
692 // * The bottom of a PLAB must be aligned on card size. In some cases this will
693 // require padding in front of the PLAB (a filler object). Because this padding
694 // is included in the region's used memory we include the padding in the usage
695 // accounting as waste.
696 // * Mutator allocations are used to compute an allocation rate. They are also
697 // sent to the Pacer for those purposes.
698 // * There are three sources of waste:
699 // 1. The padding used to align a PLAB on card size
700 // 2. Region's free is less than minimum TLAB size and is retired
701 // 3. The unused portion of memory in the last region of a humongous object
702 void ShenandoahHeap::increase_used(const ShenandoahAllocRequest& req) {
703 size_t actual_bytes = req.actual_size() * HeapWordSize;
704 size_t wasted_bytes = req.waste() * HeapWordSize;
705 ShenandoahGeneration* generation = generation_for(req.affiliation());
706
707 if (req.is_gc_alloc()) {
708 assert(wasted_bytes == 0 || req.type() == ShenandoahAllocRequest::_alloc_plab, "Only PLABs have waste");
709 increase_used(generation, actual_bytes + wasted_bytes);
710 } else {
711 assert(req.is_mutator_alloc(), "Expected mutator alloc here");
712 // padding and actual size both count towards allocation counter
713 generation->increase_allocated(actual_bytes + wasted_bytes);
714
715 // only actual size counts toward usage for mutator allocations
716 increase_used(generation, actual_bytes);
717
718 // notify pacer of both actual size and waste
719 notify_mutator_alloc_words(req.actual_size(), req.waste());
720
721 if (wasted_bytes > 0 && ShenandoahHeapRegion::requires_humongous(req.actual_size())) {
722 increase_humongous_waste(generation,wasted_bytes);
723 }
724 }
725 }
726
727 void ShenandoahHeap::increase_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
728 generation->increase_humongous_waste(bytes);
729 if (!generation->is_global()) {
730 global_generation()->increase_humongous_waste(bytes);
731 }
732 }
733
734 void ShenandoahHeap::decrease_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
735 generation->decrease_humongous_waste(bytes);
736 if (!generation->is_global()) {
737 global_generation()->decrease_humongous_waste(bytes);
738 }
739 }
740
741 void ShenandoahHeap::increase_used(ShenandoahGeneration* generation, size_t bytes) {
742 generation->increase_used(bytes);
743 if (!generation->is_global()) {
744 global_generation()->increase_used(bytes);
745 }
746 }
747
748 void ShenandoahHeap::decrease_used(ShenandoahGeneration* generation, size_t bytes) {
749 generation->decrease_used(bytes);
750 if (!generation->is_global()) {
751 global_generation()->decrease_used(bytes);
752 }
753 }
754
755 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, size_t waste) {
756 if (ShenandoahPacing) {
757 control_thread()->pacing_notify_alloc(words);
758 if (waste > 0) {
759 pacer()->claim_for_alloc<true>(waste);
760 }
761 }
762 }
763
764 size_t ShenandoahHeap::capacity() const {
765 return committed();
766 }
767
768 size_t ShenandoahHeap::max_capacity() const {
769 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
770 }
771
772 size_t ShenandoahHeap::soft_max_capacity() const {
773 size_t v = Atomic::load(&_soft_max_size);
774 assert(min_capacity() <= v && v <= max_capacity(),
775 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
776 min_capacity(), v, max_capacity());
777 return v;
778 }
779
780 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
781 assert(min_capacity() <= v && v <= max_capacity(),
782 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
783 min_capacity(), v, max_capacity());
784 Atomic::store(&_soft_max_size, v);
785 }
786
787 size_t ShenandoahHeap::min_capacity() const {
788 return _minimum_size;
789 }
790
791 size_t ShenandoahHeap::initial_capacity() const {
792 return _initial_size;
793 }
794
795 bool ShenandoahHeap::is_in(const void* p) const {
796 if (is_in_reserved(p)) {
797 if (is_full_gc_move_in_progress()) {
798 // Full GC move is running, we do not have a consistent region
799 // information yet. But we know the pointer is in heap.
800 return true;
801 }
802 // Now check if we point to a live section in active region.
803 ShenandoahHeapRegion* r = heap_region_containing(p);
804 return (r->is_active() && p < r->top());
805 } else {
806 return false;
807 }
808 }
809
810 void ShenandoahHeap::notify_soft_max_changed() {
811 if (_uncommit_thread != nullptr) {
812 _uncommit_thread->notify_soft_max_changed();
813 }
814 }
815
816 void ShenandoahHeap::notify_explicit_gc_requested() {
817 if (_uncommit_thread != nullptr) {
818 _uncommit_thread->notify_explicit_gc_requested();
819 }
820 }
821
822 bool ShenandoahHeap::check_soft_max_changed() {
823 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
824 size_t old_soft_max = soft_max_capacity();
825 if (new_soft_max != old_soft_max) {
826 new_soft_max = MAX2(min_capacity(), new_soft_max);
827 new_soft_max = MIN2(max_capacity(), new_soft_max);
828 if (new_soft_max != old_soft_max) {
829 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
830 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
831 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
832 );
833 set_soft_max_capacity(new_soft_max);
834 return true;
835 }
836 }
837 return false;
838 }
839
840 void ShenandoahHeap::notify_heap_changed() {
841 // Update monitoring counters when we took a new region. This amortizes the
842 // update costs on slow path.
843 monitoring_support()->notify_heap_changed();
844 _heap_changed.try_set();
845 }
846
847 void ShenandoahHeap::set_forced_counters_update(bool value) {
848 monitoring_support()->set_forced_counters_update(value);
849 }
850
851 void ShenandoahHeap::handle_force_counters_update() {
852 monitoring_support()->handle_force_counters_update();
853 }
854
855 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
856 // New object should fit the GCLAB size
857 size_t min_size = MAX2(size, PLAB::min_size());
858
859 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
860 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
861
862 new_size = MIN2(new_size, PLAB::max_size());
863 new_size = MAX2(new_size, PLAB::min_size());
864
865 // Record new heuristic value even if we take any shortcut. This captures
866 // the case when moderately-sized objects always take a shortcut. At some point,
867 // heuristics should catch up with them.
868 log_debug(gc, free)("Set new GCLAB size: " SIZE_FORMAT, new_size);
869 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
870
871 if (new_size < size) {
872 // New size still does not fit the object. Fall back to shared allocation.
873 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
874 log_debug(gc, free)("New gclab size (" SIZE_FORMAT ") is too small for " SIZE_FORMAT, new_size, size);
875 return nullptr;
876 }
877
878 // Retire current GCLAB, and allocate a new one.
879 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
880 gclab->retire();
881
882 size_t actual_size = 0;
883 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
884 if (gclab_buf == nullptr) {
885 return nullptr;
886 }
887
888 assert (size <= actual_size, "allocation should fit");
889
890 // ...and clear or zap just allocated TLAB, if needed.
891 if (ZeroTLAB) {
892 Copy::zero_to_words(gclab_buf, actual_size);
893 } else if (ZapTLAB) {
894 // Skip mangling the space corresponding to the object header to
895 // ensure that the returned space is not considered parsable by
896 // any concurrent GC thread.
897 size_t hdr_size = oopDesc::header_size();
898 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
899 }
900 gclab->set_buf(gclab_buf, actual_size);
901 return gclab->allocate(size);
902 }
903
904 // Called from stubs in JIT code or interpreter
905 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
906 size_t requested_size,
907 size_t* actual_size) {
908 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
909 HeapWord* res = allocate_memory(req);
910 if (res != nullptr) {
911 *actual_size = req.actual_size();
912 } else {
913 *actual_size = 0;
914 }
915 return res;
916 }
917
918 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
919 size_t word_size,
920 size_t* actual_size) {
921 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
922 HeapWord* res = allocate_memory(req);
923 if (res != nullptr) {
924 *actual_size = req.actual_size();
925 } else {
926 *actual_size = 0;
927 }
928 return res;
929 }
930
931 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
932 intptr_t pacer_epoch = 0;
933 bool in_new_region = false;
934 HeapWord* result = nullptr;
935
936 if (req.is_mutator_alloc()) {
937 if (ShenandoahPacing) {
938 pacer()->pace_for_alloc(req.size());
939 pacer_epoch = pacer()->epoch();
940 }
941
942 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
943 result = allocate_memory_under_lock(req, in_new_region);
944 }
945
946 // Check that gc overhead is not exceeded.
947 //
948 // Shenandoah will grind along for quite a while allocating one
949 // object at a time using shared (non-tlab) allocations. This check
950 // is testing that the GC overhead limit has not been exceeded.
951 // This will notify the collector to start a cycle, but will raise
952 // an OOME to the mutator if the last Full GCs have not made progress.
953 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
954 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
955 control_thread()->handle_alloc_failure(req, false);
956 req.set_actual_size(0);
957 return nullptr;
958 }
959
960 if (result == nullptr) {
961 // Block until control thread reacted, then retry allocation.
962 //
963 // It might happen that one of the threads requesting allocation would unblock
964 // way later after GC happened, only to fail the second allocation, because
965 // other threads have already depleted the free storage. In this case, a better
966 // strategy is to try again, until at least one full GC has completed.
967 //
968 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
969 // a) We experienced a GC that had good progress, or
970 // b) We experienced at least one Full GC (whether or not it had good progress)
971
972 size_t original_count = shenandoah_policy()->full_gc_count();
973 while ((result == nullptr) && (original_count == shenandoah_policy()->full_gc_count())) {
974 control_thread()->handle_alloc_failure(req, true);
975 result = allocate_memory_under_lock(req, in_new_region);
976 }
977 if (result != nullptr) {
978 // If our allocation request has been satisifed after it initially failed, we count this as good gc progress
979 notify_gc_progress();
980 }
981 if (log_develop_is_enabled(Debug, gc, alloc)) {
982 ResourceMark rm;
983 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: " SIZE_FORMAT
984 ", Original: " SIZE_FORMAT ", Latest: " SIZE_FORMAT,
985 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
986 original_count, get_gc_no_progress_count());
987 }
988 }
989 } else {
990 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
991 result = allocate_memory_under_lock(req, in_new_region);
992 // Do not call handle_alloc_failure() here, because we cannot block.
993 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
994 }
995
996 if (in_new_region) {
997 notify_heap_changed();
998 }
999
1000 if (result == nullptr) {
1001 req.set_actual_size(0);
1002 }
1003
1004 // This is called regardless of the outcome of the allocation to account
1005 // for any waste created by retiring regions with this request.
1006 increase_used(req);
1007
1008 if (result != nullptr) {
1009 size_t requested = req.size();
1010 size_t actual = req.actual_size();
1011
1012 assert (req.is_lab_alloc() || (requested == actual),
1013 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
1014 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
1015
1016 if (req.is_mutator_alloc()) {
1017 // If we requested more than we were granted, give the rest back to pacer.
1018 // This only matters if we are in the same pacing epoch: do not try to unpace
1019 // over the budget for the other phase.
1020 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
1021 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
1022 }
1023 }
1024 }
1025
1026 return result;
1027 }
1028
1029 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1030 // If we are dealing with mutator allocation, then we may need to block for safepoint.
1031 // We cannot block for safepoint for GC allocations, because there is a high chance
1032 // we are already running at safepoint or from stack watermark machinery, and we cannot
1033 // block again.
1034 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1035
1036 // Make sure the old generation has room for either evacuations or promotions before trying to allocate.
1037 if (req.is_old() && !old_generation()->can_allocate(req)) {
1038 return nullptr;
1039 }
1040
1041 // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available
1042 // memory.
1043 HeapWord* result = _free_set->allocate(req, in_new_region);
1044
1045 // Record the plab configuration for this result and register the object.
1046 if (result != nullptr && req.is_old()) {
1047 old_generation()->configure_plab_for_current_thread(req);
1048 if (req.type() == ShenandoahAllocRequest::_alloc_shared_gc) {
1049 // Register the newly allocated object while we're holding the global lock since there's no synchronization
1050 // built in to the implementation of register_object(). There are potential races when multiple independent
1051 // threads are allocating objects, some of which might span the same card region. For example, consider
1052 // a card table's memory region within which three objects are being allocated by three different threads:
1053 //
1054 // objects being "concurrently" allocated:
1055 // [-----a------][-----b-----][--------------c------------------]
1056 // [---- card table memory range --------------]
1057 //
1058 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a
1059 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region.
1060 // Allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region.
1061 // Allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this
1062 // card region.
1063 //
1064 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as
1065 // last-start representing object b while first-start represents object c. This is why we need to require all
1066 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range.
1067 old_generation()->card_scan()->register_object(result);
1068 }
1069 }
1070
1071 return result;
1072 }
1073
1074 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1075 bool* gc_overhead_limit_was_exceeded) {
1076 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1077 return allocate_memory(req);
1078 }
1079
1080 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1081 size_t size,
1082 Metaspace::MetadataType mdtype) {
1083 MetaWord* result;
1084
1085 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1086 ShenandoahHeuristics* h = global_generation()->heuristics();
1087 if (h->can_unload_classes()) {
1088 h->record_metaspace_oom();
1089 }
1090
1091 // Expand and retry allocation
1092 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1093 if (result != nullptr) {
1094 return result;
1095 }
1096
1097 // Start full GC
1098 collect(GCCause::_metadata_GC_clear_soft_refs);
1099
1100 // Retry allocation
1101 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1102 if (result != nullptr) {
1103 return result;
1104 }
1105
1106 // Expand and retry allocation
1107 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1108 if (result != nullptr) {
1109 return result;
1110 }
1111
1112 // Out of memory
1113 return nullptr;
1114 }
1115
1116 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1117 private:
1118 ShenandoahHeap* const _heap;
1119 Thread* const _thread;
1120 public:
1121 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1122 _heap(heap), _thread(Thread::current()) {}
1123
1124 void do_object(oop p) {
1125 shenandoah_assert_marked(nullptr, p);
1126 if (!p->is_forwarded()) {
1127 _heap->evacuate_object(p, _thread);
1128 }
1129 }
1130 };
1131
1132 class ShenandoahEvacuationTask : public WorkerTask {
1133 private:
1134 ShenandoahHeap* const _sh;
1135 ShenandoahCollectionSet* const _cs;
1136 bool _concurrent;
1137 public:
1138 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1139 ShenandoahCollectionSet* cs,
1140 bool concurrent) :
1141 WorkerTask("Shenandoah Evacuation"),
1142 _sh(sh),
1143 _cs(cs),
1144 _concurrent(concurrent)
1145 {}
1146
1147 void work(uint worker_id) {
1148 if (_concurrent) {
1149 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1150 ShenandoahSuspendibleThreadSetJoiner stsj;
1151 ShenandoahEvacOOMScope oom_evac_scope;
1152 do_work();
1153 } else {
1154 ShenandoahParallelWorkerSession worker_session(worker_id);
1155 ShenandoahEvacOOMScope oom_evac_scope;
1156 do_work();
1157 }
1158 }
1159
1160 private:
1161 void do_work() {
1162 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1163 ShenandoahHeapRegion* r;
1164 while ((r =_cs->claim_next()) != nullptr) {
1165 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1166 _sh->marked_object_iterate(r, &cl);
1167
1168 if (ShenandoahPacing) {
1169 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1170 }
1171
1172 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1173 break;
1174 }
1175 }
1176 }
1177 };
1178
1179 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1180 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1181 workers()->run_task(&task);
1182 }
1183
1184 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1185 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1186 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
1187 // This thread went through the OOM during evac protocol. It is safe to return
1188 // the forward pointer. It must not attempt to evacuate any other objects.
1189 return ShenandoahBarrierSet::resolve_forwarded(p);
1190 }
1191
1192 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1193
1194 ShenandoahHeapRegion* r = heap_region_containing(p);
1195 assert(!r->is_humongous(), "never evacuate humongous objects");
1196
1197 ShenandoahAffiliation target_gen = r->affiliation();
1198 return try_evacuate_object(p, thread, r, target_gen);
1199 }
1200
1201 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1202 ShenandoahAffiliation target_gen) {
1203 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1204 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1205 bool alloc_from_lab = true;
1206 HeapWord* copy = nullptr;
1207
1208 markWord mark = p->mark();
1209 if (ShenandoahForwarding::is_forwarded(mark)) {
1210 return ShenandoahForwarding::get_forwardee(p);
1211 }
1212 size_t old_size = ShenandoahForwarding::size(p);
1213 size_t size = p->copy_size(old_size, mark);
1214
1215 #ifdef ASSERT
1216 if (ShenandoahOOMDuringEvacALot &&
1217 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1218 copy = nullptr;
1219 } else {
1220 #endif
1221 if (UseTLAB) {
1222 copy = allocate_from_gclab(thread, size);
1223 }
1224 if (copy == nullptr) {
1225 // If we failed to allocate in LAB, we'll try a shared allocation.
1226 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1227 copy = allocate_memory(req);
1228 alloc_from_lab = false;
1229 }
1230 #ifdef ASSERT
1231 }
1232 #endif
1233
1234 if (copy == nullptr) {
1235 control_thread()->handle_alloc_failure_evac(size);
1236
1237 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1238
1239 return ShenandoahBarrierSet::resolve_forwarded(p);
1240 }
1241
1242 // Copy the object:
1243 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, old_size);
1244
1245 // Try to install the new forwarding pointer.
1246 oop copy_val = cast_to_oop(copy);
1247 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1248 if (result == copy_val) {
1249 // Successfully evacuated. Our copy is now the public one!
1250 copy_val->initialize_hash_if_necessary(p);
1251 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1252 shenandoah_assert_correct(nullptr, copy_val);
1253 return copy_val;
1254 } else {
1255 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1256 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1257 // But if it happens to contain references to evacuated regions, those references would
1258 // not get updated for this stale copy during this cycle, and we will crash while scanning
1259 // it the next cycle.
1260 if (alloc_from_lab) {
1261 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1262 // object will overwrite this stale copy, or the filler object on LAB retirement will
1263 // do this.
1264 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1265 } else {
1266 // For non-LAB allocations, we have no way to retract the allocation, and
1267 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1268 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1269 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1270 fill_with_object(copy, size);
1271 shenandoah_assert_correct(nullptr, copy_val);
1272 // For non-LAB allocations, the object has already been registered
1273 }
1274 shenandoah_assert_correct(nullptr, result);
1275 return result;
1276 }
1277 }
1278
1279 void ShenandoahHeap::trash_cset_regions() {
1280 ShenandoahHeapLocker locker(lock());
1281
1282 ShenandoahCollectionSet* set = collection_set();
1283 ShenandoahHeapRegion* r;
1284 set->clear_current_index();
1285 while ((r = set->next()) != nullptr) {
1286 r->make_trash();
1287 }
1288 collection_set()->clear();
1289 }
1290
1291 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1292 st->print_cr("Heap Regions:");
1293 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1294 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1295 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1296 st->print_cr("UWM=update watermark, U=used");
1297 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1298 st->print_cr("S=shared allocs, L=live data");
1299 st->print_cr("CP=critical pins");
1300
1301 for (size_t i = 0; i < num_regions(); i++) {
1302 get_region(i)->print_on(st);
1303 }
1304 }
1305
1306 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1307 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1308
1309 oop humongous_obj = cast_to_oop(start->bottom());
1310 size_t size = humongous_obj->size();
1311 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1312 size_t index = start->index() + required_regions - 1;
1313
1314 assert(!start->has_live(), "liveness must be zero");
1315
1316 for(size_t i = 0; i < required_regions; i++) {
1317 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1318 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1319 ShenandoahHeapRegion* region = get_region(index --);
1320
1321 assert(region->is_humongous(), "expect correct humongous start or continuation");
1322 assert(!region->is_cset(), "Humongous region should not be in collection set");
1323
1324 region->make_trash_immediate();
1325 }
1326 return required_regions;
1327 }
1328
1329 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1330 public:
1331 ShenandoahCheckCleanGCLABClosure() {}
1332 void do_thread(Thread* thread) {
1333 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1334 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1335 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1336
1337 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1338 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1339 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1340 assert(plab->words_remaining() == 0, "PLAB should not need retirement");
1341 }
1342 }
1343 };
1344
1345 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1346 private:
1347 bool const _resize;
1348 public:
1349 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1350 void do_thread(Thread* thread) {
1351 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1352 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1353 gclab->retire();
1354 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1355 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1356 }
1357
1358 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1359 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1360 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1361
1362 // There are two reasons to retire all plabs between old-gen evacuation passes.
1363 // 1. We need to make the plab memory parsable by remembered-set scanning.
1364 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1365 ShenandoahGenerationalHeap::heap()->retire_plab(plab, thread);
1366 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) {
1367 ShenandoahThreadLocalData::set_plab_size(thread, 0);
1368 }
1369 }
1370 }
1371 };
1372
1373 void ShenandoahHeap::labs_make_parsable() {
1374 assert(UseTLAB, "Only call with UseTLAB");
1375
1376 ShenandoahRetireGCLABClosure cl(false);
1377
1378 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1379 ThreadLocalAllocBuffer& tlab = t->tlab();
1380 tlab.make_parsable();
1381 cl.do_thread(t);
1382 }
1383
1384 workers()->threads_do(&cl);
1385 }
1386
1387 void ShenandoahHeap::tlabs_retire(bool resize) {
1388 assert(UseTLAB, "Only call with UseTLAB");
1389 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1390
1391 ThreadLocalAllocStats stats;
1392
1393 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1394 ThreadLocalAllocBuffer& tlab = t->tlab();
1395 tlab.retire(&stats);
1396 if (resize) {
1397 tlab.resize();
1398 }
1399 }
1400
1401 stats.publish();
1402
1403 #ifdef ASSERT
1404 ShenandoahCheckCleanGCLABClosure cl;
1405 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1406 cl.do_thread(t);
1407 }
1408 workers()->threads_do(&cl);
1409 #endif
1410 }
1411
1412 void ShenandoahHeap::gclabs_retire(bool resize) {
1413 assert(UseTLAB, "Only call with UseTLAB");
1414 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1415
1416 ShenandoahRetireGCLABClosure cl(resize);
1417 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1418 cl.do_thread(t);
1419 }
1420 workers()->threads_do(&cl);
1421
1422 if (safepoint_workers() != nullptr) {
1423 safepoint_workers()->threads_do(&cl);
1424 }
1425 }
1426
1427 // Returns size in bytes
1428 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1429 // Return the max allowed size, and let the allocation path
1430 // figure out the safe size for current allocation.
1431 return ShenandoahHeapRegion::max_tlab_size_bytes();
1432 }
1433
1434 size_t ShenandoahHeap::max_tlab_size() const {
1435 // Returns size in words
1436 return ShenandoahHeapRegion::max_tlab_size_words();
1437 }
1438
1439 void ShenandoahHeap::collect(GCCause::Cause cause) {
1440 control_thread()->request_gc(cause);
1441 }
1442
1443 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1444 //assert(false, "Shouldn't need to do full collections");
1445 }
1446
1447 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1448 ShenandoahHeapRegion* r = heap_region_containing(addr);
1449 if (r != nullptr) {
1450 return r->block_start(addr);
1451 }
1452 return nullptr;
1453 }
1454
1455 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1456 ShenandoahHeapRegion* r = heap_region_containing(addr);
1457 return r->block_is_obj(addr);
1458 }
1459
1460 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1461 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1462 }
1463
1464 void ShenandoahHeap::prepare_for_verify() {
1465 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1466 labs_make_parsable();
1467 }
1468 }
1469
1470 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1471 if (_shenandoah_policy->is_at_shutdown()) {
1472 return;
1473 }
1474
1475 if (_control_thread != nullptr) {
1476 tcl->do_thread(_control_thread);
1477 }
1478
1479 if (_uncommit_thread != nullptr) {
1480 tcl->do_thread(_uncommit_thread);
1481 }
1482
1483 workers()->threads_do(tcl);
1484 if (_safepoint_workers != nullptr) {
1485 _safepoint_workers->threads_do(tcl);
1486 }
1487 }
1488
1489 void ShenandoahHeap::print_tracing_info() const {
1490 LogTarget(Info, gc, stats) lt;
1491 if (lt.is_enabled()) {
1492 ResourceMark rm;
1493 LogStream ls(lt);
1494
1495 phase_timings()->print_global_on(&ls);
1496
1497 ls.cr();
1498 ls.cr();
1499
1500 shenandoah_policy()->print_gc_stats(&ls);
1501
1502 ls.cr();
1503 ls.cr();
1504 }
1505 }
1506
1507 void ShenandoahHeap::set_gc_generation(ShenandoahGeneration* generation) {
1508 shenandoah_assert_control_or_vm_thread_at_safepoint();
1509 _gc_generation = generation;
1510 }
1511
1512 // Active generation may only be set by the VM thread at a safepoint.
1513 void ShenandoahHeap::set_active_generation() {
1514 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1515 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1516 assert(_gc_generation != nullptr, "Will set _active_generation to nullptr");
1517 _active_generation = _gc_generation;
1518 }
1519
1520 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
1521 shenandoah_policy()->record_collection_cause(cause);
1522
1523 assert(gc_cause() == GCCause::_no_gc, "Over-writing cause");
1524 assert(_gc_generation == nullptr, "Over-writing _gc_generation");
1525
1526 set_gc_cause(cause);
1527 set_gc_generation(generation);
1528
1529 generation->heuristics()->record_cycle_start();
1530 }
1531
1532 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1533 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1534 assert(_gc_generation != nullptr, "_gc_generation wasn't set");
1535
1536 generation->heuristics()->record_cycle_end();
1537 if (mode()->is_generational() && generation->is_global()) {
1538 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1539 young_generation()->heuristics()->record_cycle_end();
1540 old_generation()->heuristics()->record_cycle_end();
1541 }
1542
1543 set_gc_generation(nullptr);
1544 set_gc_cause(GCCause::_no_gc);
1545 }
1546
1547 void ShenandoahHeap::verify(VerifyOption vo) {
1548 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1549 if (ShenandoahVerify) {
1550 verifier()->verify_generic(vo);
1551 } else {
1552 // TODO: Consider allocating verification bitmaps on demand,
1553 // and turn this on unconditionally.
1554 }
1555 }
1556 }
1557 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1558 return _free_set->capacity();
1559 }
1560
1561 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1562 private:
1563 MarkBitMap* _bitmap;
1564 ShenandoahScanObjectStack* _oop_stack;
1565 ShenandoahHeap* const _heap;
1566 ShenandoahMarkingContext* const _marking_context;
1567
1568 template <class T>
1569 void do_oop_work(T* p) {
1570 T o = RawAccess<>::oop_load(p);
1571 if (!CompressedOops::is_null(o)) {
1572 oop obj = CompressedOops::decode_not_null(o);
1573 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1574 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1575 return;
1576 }
1577 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1578
1579 assert(oopDesc::is_oop(obj), "must be a valid oop");
1580 if (!_bitmap->is_marked(obj)) {
1581 _bitmap->mark(obj);
1582 _oop_stack->push(obj);
1583 }
1584 }
1585 }
1586 public:
1587 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1588 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1589 _marking_context(_heap->marking_context()) {}
1590 void do_oop(oop* p) { do_oop_work(p); }
1591 void do_oop(narrowOop* p) { do_oop_work(p); }
1592 };
1593
1594 /*
1595 * This is public API, used in preparation of object_iterate().
1596 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1597 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1598 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1599 */
1600 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1601 // No-op.
1602 }
1603
1604 /*
1605 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1606 *
1607 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1608 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1609 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1610 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1611 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1612 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1613 * wiped the bitmap in preparation for next marking).
1614 *
1615 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1616 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1617 * is allowed to report dead objects, but is not required to do so.
1618 */
1619 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1620 // Reset bitmap
1621 if (!prepare_aux_bitmap_for_iteration())
1622 return;
1623
1624 ShenandoahScanObjectStack oop_stack;
1625 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1626 // Seed the stack with root scan
1627 scan_roots_for_iteration(&oop_stack, &oops);
1628
1629 // Work through the oop stack to traverse heap
1630 while (! oop_stack.is_empty()) {
1631 oop obj = oop_stack.pop();
1632 assert(oopDesc::is_oop(obj), "must be a valid oop");
1633 cl->do_object(obj);
1634 obj->oop_iterate(&oops);
1635 }
1636
1637 assert(oop_stack.is_empty(), "should be empty");
1638 // Reclaim bitmap
1639 reclaim_aux_bitmap_for_iteration();
1640 }
1641
1642 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1643 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1644
1645 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1646 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1647 return false;
1648 }
1649 // Reset bitmap
1650 _aux_bit_map.clear();
1651 return true;
1652 }
1653
1654 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1655 // Process GC roots according to current GC cycle
1656 // This populates the work stack with initial objects
1657 // It is important to relinquish the associated locks before diving
1658 // into heap dumper
1659 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1660 ShenandoahHeapIterationRootScanner rp(n_workers);
1661 rp.roots_do(oops);
1662 }
1663
1664 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1665 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1666 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1667 }
1668 }
1669
1670 // Closure for parallelly iterate objects
1671 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1672 private:
1673 MarkBitMap* _bitmap;
1674 ShenandoahObjToScanQueue* _queue;
1675 ShenandoahHeap* const _heap;
1676 ShenandoahMarkingContext* const _marking_context;
1677
1678 template <class T>
1679 void do_oop_work(T* p) {
1680 T o = RawAccess<>::oop_load(p);
1681 if (!CompressedOops::is_null(o)) {
1682 oop obj = CompressedOops::decode_not_null(o);
1683 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1684 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1685 return;
1686 }
1687 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1688
1689 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1690 if (_bitmap->par_mark(obj)) {
1691 _queue->push(ShenandoahMarkTask(obj));
1692 }
1693 }
1694 }
1695 public:
1696 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1697 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1698 _marking_context(_heap->marking_context()) {}
1699 void do_oop(oop* p) { do_oop_work(p); }
1700 void do_oop(narrowOop* p) { do_oop_work(p); }
1701 };
1702
1703 // Object iterator for parallel heap iteraion.
1704 // The root scanning phase happenes in construction as a preparation of
1705 // parallel marking queues.
1706 // Every worker processes it's own marking queue. work-stealing is used
1707 // to balance workload.
1708 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1709 private:
1710 uint _num_workers;
1711 bool _init_ready;
1712 MarkBitMap* _aux_bit_map;
1713 ShenandoahHeap* _heap;
1714 ShenandoahScanObjectStack _roots_stack; // global roots stack
1715 ShenandoahObjToScanQueueSet* _task_queues;
1716 public:
1717 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1718 _num_workers(num_workers),
1719 _init_ready(false),
1720 _aux_bit_map(bitmap),
1721 _heap(ShenandoahHeap::heap()) {
1722 // Initialize bitmap
1723 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1724 if (!_init_ready) {
1725 return;
1726 }
1727
1728 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1729 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1730
1731 _init_ready = prepare_worker_queues();
1732 }
1733
1734 ~ShenandoahParallelObjectIterator() {
1735 // Reclaim bitmap
1736 _heap->reclaim_aux_bitmap_for_iteration();
1737 // Reclaim queue for workers
1738 if (_task_queues!= nullptr) {
1739 for (uint i = 0; i < _num_workers; ++i) {
1740 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1741 if (q != nullptr) {
1742 delete q;
1743 _task_queues->register_queue(i, nullptr);
1744 }
1745 }
1746 delete _task_queues;
1747 _task_queues = nullptr;
1748 }
1749 }
1750
1751 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1752 if (_init_ready) {
1753 object_iterate_parallel(cl, worker_id, _task_queues);
1754 }
1755 }
1756
1757 private:
1758 // Divide global root_stack into worker queues
1759 bool prepare_worker_queues() {
1760 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1761 // Initialize queues for every workers
1762 for (uint i = 0; i < _num_workers; ++i) {
1763 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1764 _task_queues->register_queue(i, task_queue);
1765 }
1766 // Divide roots among the workers. Assume that object referencing distribution
1767 // is related with root kind, use round-robin to make every worker have same chance
1768 // to process every kind of roots
1769 size_t roots_num = _roots_stack.size();
1770 if (roots_num == 0) {
1771 // No work to do
1772 return false;
1773 }
1774
1775 for (uint j = 0; j < roots_num; j++) {
1776 uint stack_id = j % _num_workers;
1777 oop obj = _roots_stack.pop();
1778 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1779 }
1780 return true;
1781 }
1782
1783 void object_iterate_parallel(ObjectClosure* cl,
1784 uint worker_id,
1785 ShenandoahObjToScanQueueSet* queue_set) {
1786 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1787 assert(queue_set != nullptr, "task queue must not be null");
1788
1789 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1790 assert(q != nullptr, "object iterate queue must not be null");
1791
1792 ShenandoahMarkTask t;
1793 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1794
1795 // Work through the queue to traverse heap.
1796 // Steal when there is no task in queue.
1797 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1798 oop obj = t.obj();
1799 assert(oopDesc::is_oop(obj), "must be a valid oop");
1800 cl->do_object(obj);
1801 obj->oop_iterate(&oops);
1802 }
1803 assert(q->is_empty(), "should be empty");
1804 }
1805 };
1806
1807 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1808 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1809 }
1810
1811 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1812 void ShenandoahHeap::keep_alive(oop obj) {
1813 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1814 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1815 }
1816 }
1817
1818 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1819 for (size_t i = 0; i < num_regions(); i++) {
1820 ShenandoahHeapRegion* current = get_region(i);
1821 blk->heap_region_do(current);
1822 }
1823 }
1824
1825 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1826 private:
1827 ShenandoahHeap* const _heap;
1828 ShenandoahHeapRegionClosure* const _blk;
1829 size_t const _stride;
1830
1831 shenandoah_padding(0);
1832 volatile size_t _index;
1833 shenandoah_padding(1);
1834
1835 public:
1836 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
1837 WorkerTask("Shenandoah Parallel Region Operation"),
1838 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
1839
1840 void work(uint worker_id) {
1841 ShenandoahParallelWorkerSession worker_session(worker_id);
1842 size_t stride = _stride;
1843
1844 size_t max = _heap->num_regions();
1845 while (Atomic::load(&_index) < max) {
1846 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1847 size_t start = cur;
1848 size_t end = MIN2(cur + stride, max);
1849 if (start >= max) break;
1850
1851 for (size_t i = cur; i < end; i++) {
1852 ShenandoahHeapRegion* current = _heap->get_region(i);
1853 _blk->heap_region_do(current);
1854 }
1855 }
1856 }
1857 };
1858
1859 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1860 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1861 const uint active_workers = workers()->active_workers();
1862 const size_t n_regions = num_regions();
1863 size_t stride = ShenandoahParallelRegionStride;
1864 if (stride == 0 && active_workers > 1) {
1865 // Automatically derive the stride to balance the work between threads
1866 // evenly. Do not try to split work if below the reasonable threshold.
1867 constexpr size_t threshold = 4096;
1868 stride = n_regions <= threshold ?
1869 threshold :
1870 (n_regions + active_workers - 1) / active_workers;
1871 }
1872
1873 if (n_regions > stride && active_workers > 1) {
1874 ShenandoahParallelHeapRegionTask task(blk, stride);
1875 workers()->run_task(&task);
1876 } else {
1877 heap_region_iterate(blk);
1878 }
1879 }
1880
1881 class ShenandoahRendezvousClosure : public HandshakeClosure {
1882 public:
1883 inline ShenandoahRendezvousClosure(const char* name) : HandshakeClosure(name) {}
1884 inline void do_thread(Thread* thread) {}
1885 };
1886
1887 void ShenandoahHeap::rendezvous_threads(const char* name) {
1888 ShenandoahRendezvousClosure cl(name);
1889 Handshake::execute(&cl);
1890 }
1891
1892 void ShenandoahHeap::recycle_trash() {
1893 free_set()->recycle_trash();
1894 }
1895
1896 void ShenandoahHeap::do_class_unloading() {
1897 _unloader.unload();
1898 if (mode()->is_generational()) {
1899 old_generation()->set_parsable(false);
1900 }
1901 }
1902
1903 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1904 // Weak refs processing
1905 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1906 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1907 ShenandoahTimingsTracker t(phase);
1908 ShenandoahGCWorkerPhase worker_phase(phase);
1909 shenandoah_assert_generations_reconciled();
1910 gc_generation()->ref_processor()->process_references(phase, workers(), false /* concurrent */);
1911 }
1912
1913 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1914 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1915
1916 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1917 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1918 // for future GCLABs here.
1919 if (UseTLAB) {
1920 ShenandoahGCPhase phase(concurrent ?
1921 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1922 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1923 gclabs_retire(ResizeTLAB);
1924 }
1925
1926 _update_refs_iterator.reset();
1927 }
1928
1929 void ShenandoahHeap::propagate_gc_state_to_java_threads() {
1930 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1931 if (_gc_state_changed) {
1932 _gc_state_changed = false;
1933 char state = gc_state();
1934 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1935 ShenandoahThreadLocalData::set_gc_state(t, state);
1936 }
1937 }
1938 }
1939
1940 void ShenandoahHeap::set_gc_state(uint mask, bool value) {
1941 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1942 _gc_state.set_cond(mask, value);
1943 _gc_state_changed = true;
1944 }
1945
1946 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
1947 uint mask;
1948 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
1949 if (!in_progress && is_concurrent_old_mark_in_progress()) {
1950 assert(mode()->is_generational(), "Only generational GC has old marking");
1951 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
1952 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
1953 mask = YOUNG_MARKING;
1954 } else {
1955 mask = MARKING | YOUNG_MARKING;
1956 }
1957 set_gc_state(mask, in_progress);
1958 manage_satb_barrier(in_progress);
1959 }
1960
1961 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
1962 #ifdef ASSERT
1963 // has_forwarded_objects() iff UPDATEREFS or EVACUATION
1964 bool has_forwarded = has_forwarded_objects();
1965 bool updating_or_evacuating = _gc_state.is_set(UPDATEREFS | EVACUATION);
1966 bool evacuating = _gc_state.is_set(EVACUATION);
1967 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
1968 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
1969 #endif
1970 if (!in_progress && is_concurrent_young_mark_in_progress()) {
1971 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
1972 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
1973 set_gc_state(OLD_MARKING, in_progress);
1974 } else {
1975 set_gc_state(MARKING | OLD_MARKING, in_progress);
1976 }
1977 manage_satb_barrier(in_progress);
1978 }
1979
1980 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
1981 return old_generation()->is_preparing_for_mark();
1982 }
1983
1984 void ShenandoahHeap::manage_satb_barrier(bool active) {
1985 if (is_concurrent_mark_in_progress()) {
1986 // Ignore request to deactivate barrier while concurrent mark is in progress.
1987 // Do not attempt to re-activate the barrier if it is already active.
1988 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
1989 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
1990 }
1991 } else {
1992 // No concurrent marking is in progress so honor request to deactivate,
1993 // but only if the barrier is already active.
1994 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
1995 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
1996 }
1997 }
1998 }
1999
2000 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2001 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2002 set_gc_state(EVACUATION, in_progress);
2003 }
2004
2005 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2006 if (in_progress) {
2007 _concurrent_strong_root_in_progress.set();
2008 } else {
2009 _concurrent_strong_root_in_progress.unset();
2010 }
2011 }
2012
2013 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2014 set_gc_state(WEAK_ROOTS, cond);
2015 }
2016
2017 GCTracer* ShenandoahHeap::tracer() {
2018 return shenandoah_policy()->tracer();
2019 }
2020
2021 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2022 return _free_set->used();
2023 }
2024
2025 bool ShenandoahHeap::try_cancel_gc() {
2026 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
2027 return prev == CANCELLABLE;
2028 }
2029
2030 void ShenandoahHeap::cancel_concurrent_mark() {
2031 if (mode()->is_generational()) {
2032 young_generation()->cancel_marking();
2033 old_generation()->cancel_marking();
2034 }
2035
2036 global_generation()->cancel_marking();
2037
2038 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2039 }
2040
2041 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2042 if (try_cancel_gc()) {
2043 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2044 log_info(gc)("%s", msg.buffer());
2045 Events::log(Thread::current(), "%s", msg.buffer());
2046 _cancel_requested_time = os::elapsedTime();
2047 }
2048 }
2049
2050 uint ShenandoahHeap::max_workers() {
2051 return _max_workers;
2052 }
2053
2054 void ShenandoahHeap::stop() {
2055 // The shutdown sequence should be able to terminate when GC is running.
2056
2057 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2058 _shenandoah_policy->record_shutdown();
2059
2060 // Step 1. Notify control thread that we are in shutdown.
2061 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
2062 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
2063 control_thread()->prepare_for_graceful_shutdown();
2064
2065 // Step 2. Notify GC workers that we are cancelling GC.
2066 cancel_gc(GCCause::_shenandoah_stop_vm);
2067
2068 // Step 3. Wait until GC worker exits normally.
2069 control_thread()->stop();
2070
2071 // Stop 4. Shutdown uncommit thread.
2072 if (_uncommit_thread != nullptr) {
2073 _uncommit_thread->stop();
2074 }
2075 }
2076
2077 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2078 if (!unload_classes()) return;
2079 ClassUnloadingContext ctx(_workers->active_workers(),
2080 true /* unregister_nmethods_during_purge */,
2081 false /* lock_nmethod_free_separately */);
2082
2083 // Unload classes and purge SystemDictionary.
2084 {
2085 ShenandoahPhaseTimings::Phase phase = full_gc ?
2086 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2087 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2088 ShenandoahIsAliveSelector is_alive;
2089 {
2090 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2091 ShenandoahGCPhase gc_phase(phase);
2092 ShenandoahGCWorkerPhase worker_phase(phase);
2093 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2094
2095 uint num_workers = _workers->active_workers();
2096 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
2097 _workers->run_task(&unlink_task);
2098 }
2099 // Release unloaded nmethods's memory.
2100 ClassUnloadingContext::context()->purge_and_free_nmethods();
2101 }
2102
2103 {
2104 ShenandoahGCPhase phase(full_gc ?
2105 ShenandoahPhaseTimings::full_gc_purge_cldg :
2106 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2107 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2108 }
2109 // Resize and verify metaspace
2110 MetaspaceGC::compute_new_size();
2111 DEBUG_ONLY(MetaspaceUtils::verify();)
2112 }
2113
2114 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
2115 // so they should not have forwarded oops.
2116 // However, we do need to "null" dead oops in the roots, if can not be done
2117 // in concurrent cycles.
2118 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2119 uint num_workers = _workers->active_workers();
2120 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2121 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2122 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2123 ShenandoahGCPhase phase(timing_phase);
2124 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2125 // Cleanup weak roots
2126 if (has_forwarded_objects()) {
2127 ShenandoahForwardedIsAliveClosure is_alive;
2128 ShenandoahNonConcUpdateRefsClosure keep_alive;
2129 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2130 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2131 _workers->run_task(&cleaning_task);
2132 } else {
2133 ShenandoahIsAliveClosure is_alive;
2134 #ifdef ASSERT
2135 ShenandoahAssertNotForwardedClosure verify_cl;
2136 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2137 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2138 #else
2139 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2140 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2141 #endif
2142 _workers->run_task(&cleaning_task);
2143 }
2144 }
2145
2146 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2147 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2148 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2149 ShenandoahGCPhase phase(full_gc ?
2150 ShenandoahPhaseTimings::full_gc_purge :
2151 ShenandoahPhaseTimings::degen_gc_purge);
2152 stw_weak_refs(full_gc);
2153 stw_process_weak_roots(full_gc);
2154 stw_unload_classes(full_gc);
2155 }
2156
2157 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2158 set_gc_state(HAS_FORWARDED, cond);
2159 }
2160
2161 void ShenandoahHeap::set_unload_classes(bool uc) {
2162 _unload_classes.set_cond(uc);
2163 }
2164
2165 bool ShenandoahHeap::unload_classes() const {
2166 return _unload_classes.is_set();
2167 }
2168
2169 address ShenandoahHeap::in_cset_fast_test_addr() {
2170 ShenandoahHeap* heap = ShenandoahHeap::heap();
2171 assert(heap->collection_set() != nullptr, "Sanity");
2172 return (address) heap->collection_set()->biased_map_address();
2173 }
2174
2175 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2176 if (mode()->is_generational()) {
2177 young_generation()->reset_bytes_allocated_since_gc_start();
2178 old_generation()->reset_bytes_allocated_since_gc_start();
2179 }
2180
2181 global_generation()->reset_bytes_allocated_since_gc_start();
2182 }
2183
2184 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2185 _degenerated_gc_in_progress.set_cond(in_progress);
2186 }
2187
2188 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2189 _full_gc_in_progress.set_cond(in_progress);
2190 }
2191
2192 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2193 assert (is_full_gc_in_progress(), "should be");
2194 _full_gc_move_in_progress.set_cond(in_progress);
2195 }
2196
2197 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2198 set_gc_state(UPDATEREFS, in_progress);
2199 }
2200
2201 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2202 ShenandoahCodeRoots::register_nmethod(nm);
2203 }
2204
2205 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2206 ShenandoahCodeRoots::unregister_nmethod(nm);
2207 }
2208
2209 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2210 heap_region_containing(o)->record_pin();
2211 }
2212
2213 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2214 ShenandoahHeapRegion* r = heap_region_containing(o);
2215 assert(r != nullptr, "Sanity");
2216 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
2217 r->record_unpin();
2218 }
2219
2220 void ShenandoahHeap::sync_pinned_region_status() {
2221 ShenandoahHeapLocker locker(lock());
2222
2223 for (size_t i = 0; i < num_regions(); i++) {
2224 ShenandoahHeapRegion *r = get_region(i);
2225 if (r->is_active()) {
2226 if (r->is_pinned()) {
2227 if (r->pin_count() == 0) {
2228 r->make_unpinned();
2229 }
2230 } else {
2231 if (r->pin_count() > 0) {
2232 r->make_pinned();
2233 }
2234 }
2235 }
2236 }
2237
2238 assert_pinned_region_status();
2239 }
2240
2241 #ifdef ASSERT
2242 void ShenandoahHeap::assert_pinned_region_status() {
2243 for (size_t i = 0; i < num_regions(); i++) {
2244 ShenandoahHeapRegion* r = get_region(i);
2245 shenandoah_assert_generations_reconciled();
2246 if (gc_generation()->contains(r)) {
2247 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2248 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2249 }
2250 }
2251 }
2252 #endif
2253
2254 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2255 return _gc_timer;
2256 }
2257
2258 void ShenandoahHeap::prepare_concurrent_roots() {
2259 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2260 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2261 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2262 set_concurrent_weak_root_in_progress(true);
2263 if (unload_classes()) {
2264 _unloader.prepare();
2265 }
2266 }
2267
2268 void ShenandoahHeap::finish_concurrent_roots() {
2269 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2270 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2271 if (unload_classes()) {
2272 _unloader.finish();
2273 }
2274 }
2275
2276 #ifdef ASSERT
2277 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2278 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2279
2280 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2281 // Use ParallelGCThreads inside safepoints
2282 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2283 ParallelGCThreads, nworkers);
2284 } else {
2285 // Use ConcGCThreads outside safepoints
2286 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2287 ConcGCThreads, nworkers);
2288 }
2289 }
2290 #endif
2291
2292 ShenandoahVerifier* ShenandoahHeap::verifier() {
2293 guarantee(ShenandoahVerify, "Should be enabled");
2294 assert (_verifier != nullptr, "sanity");
2295 return _verifier;
2296 }
2297
2298 template<bool CONCURRENT>
2299 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2300 private:
2301 ShenandoahHeap* _heap;
2302 ShenandoahRegionIterator* _regions;
2303 public:
2304 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2305 WorkerTask("Shenandoah Update References"),
2306 _heap(ShenandoahHeap::heap()),
2307 _regions(regions) {
2308 }
2309
2310 void work(uint worker_id) {
2311 if (CONCURRENT) {
2312 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2313 ShenandoahSuspendibleThreadSetJoiner stsj;
2314 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2315 } else {
2316 ShenandoahParallelWorkerSession worker_session(worker_id);
2317 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2318 }
2319 }
2320
2321 private:
2322 template<class T>
2323 void do_work(uint worker_id) {
2324 if (CONCURRENT && (worker_id == 0)) {
2325 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2326 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2327 size_t cset_regions = _heap->collection_set()->count();
2328
2329 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2330 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2331 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2332 // next GC cycle.
2333 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2334 }
2335 // If !CONCURRENT, there's no value in expanding Mutator free set
2336 T cl;
2337 ShenandoahHeapRegion* r = _regions->next();
2338 while (r != nullptr) {
2339 HeapWord* update_watermark = r->get_update_watermark();
2340 assert (update_watermark >= r->bottom(), "sanity");
2341 if (r->is_active() && !r->is_cset()) {
2342 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2343 if (ShenandoahPacing) {
2344 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2345 }
2346 }
2347 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2348 return;
2349 }
2350 r = _regions->next();
2351 }
2352 }
2353 };
2354
2355 void ShenandoahHeap::update_heap_references(bool concurrent) {
2356 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2357
2358 if (concurrent) {
2359 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2360 workers()->run_task(&task);
2361 } else {
2362 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2363 workers()->run_task(&task);
2364 }
2365 }
2366
2367 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2368 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2369 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2370
2371 {
2372 ShenandoahGCPhase phase(concurrent ?
2373 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2374 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2375
2376 final_update_refs_update_region_states();
2377
2378 assert_pinned_region_status();
2379 }
2380
2381 {
2382 ShenandoahGCPhase phase(concurrent ?
2383 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2384 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2385 trash_cset_regions();
2386 }
2387 }
2388
2389 void ShenandoahHeap::final_update_refs_update_region_states() {
2390 ShenandoahSynchronizePinnedRegionStates cl;
2391 parallel_heap_region_iterate(&cl);
2392 }
2393
2394 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2395 ShenandoahGCPhase phase(concurrent ?
2396 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2397 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2398 ShenandoahHeapLocker locker(lock());
2399 size_t young_cset_regions, old_cset_regions;
2400 size_t first_old_region, last_old_region, old_region_count;
2401 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count);
2402 // If there are no old regions, first_old_region will be greater than last_old_region
2403 assert((first_old_region > last_old_region) ||
2404 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2405 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2406 "sanity: old_region_count: " SIZE_FORMAT ", first_old_region: " SIZE_FORMAT ", last_old_region: " SIZE_FORMAT,
2407 old_region_count, first_old_region, last_old_region);
2408
2409 if (mode()->is_generational()) {
2410 #ifdef ASSERT
2411 if (ShenandoahVerify) {
2412 verifier()->verify_before_rebuilding_free_set();
2413 }
2414 #endif
2415
2416 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2417 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2418 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2419 size_t allocation_runway = gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions);
2420 gen_heap->compute_old_generation_balance(allocation_runway, old_cset_regions);
2421
2422 // Total old_available may have been expanded to hold anticipated promotions. We trigger if the fragmented available
2423 // memory represents more than 16 regions worth of data. Note that fragmentation may increase when we promote regular
2424 // regions in place when many of these regular regions have an abundant amount of available memory within them. Fragmentation
2425 // will decrease as promote-by-copy consumes the available memory within these partially consumed regions.
2426 //
2427 // We consider old-gen to have excessive fragmentation if more than 12.5% of old-gen is free memory that resides
2428 // within partially consumed regions of memory.
2429 }
2430 // Rebuild free set based on adjusted generation sizes.
2431 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, old_region_count);
2432
2433 if (mode()->is_generational()) {
2434 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2435 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2436 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2437 }
2438 }
2439
2440 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2441 print_on(st);
2442 st->cr();
2443 print_heap_regions_on(st);
2444 }
2445
2446 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2447 size_t slice = r->index() / _bitmap_regions_per_slice;
2448
2449 size_t regions_from = _bitmap_regions_per_slice * slice;
2450 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2451 for (size_t g = regions_from; g < regions_to; g++) {
2452 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2453 if (skip_self && g == r->index()) continue;
2454 if (get_region(g)->is_committed()) {
2455 return true;
2456 }
2457 }
2458 return false;
2459 }
2460
2461 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2462 shenandoah_assert_heaplocked();
2463
2464 // Bitmaps in special regions do not need commits
2465 if (_bitmap_region_special) {
2466 return true;
2467 }
2468
2469 if (is_bitmap_slice_committed(r, true)) {
2470 // Some other region from the group is already committed, meaning the bitmap
2471 // slice is already committed, we exit right away.
2472 return true;
2473 }
2474
2475 // Commit the bitmap slice:
2476 size_t slice = r->index() / _bitmap_regions_per_slice;
2477 size_t off = _bitmap_bytes_per_slice * slice;
2478 size_t len = _bitmap_bytes_per_slice;
2479 char* start = (char*) _bitmap_region.start() + off;
2480
2481 if (!os::commit_memory(start, len, false)) {
2482 return false;
2483 }
2484
2485 if (AlwaysPreTouch) {
2486 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2487 }
2488
2489 return true;
2490 }
2491
2492 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2493 shenandoah_assert_heaplocked();
2494
2495 // Bitmaps in special regions do not need uncommits
2496 if (_bitmap_region_special) {
2497 return true;
2498 }
2499
2500 if (is_bitmap_slice_committed(r, true)) {
2501 // Some other region from the group is still committed, meaning the bitmap
2502 // slice should stay committed, exit right away.
2503 return true;
2504 }
2505
2506 // Uncommit the bitmap slice:
2507 size_t slice = r->index() / _bitmap_regions_per_slice;
2508 size_t off = _bitmap_bytes_per_slice * slice;
2509 size_t len = _bitmap_bytes_per_slice;
2510 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2511 return false;
2512 }
2513 return true;
2514 }
2515
2516 void ShenandoahHeap::forbid_uncommit() {
2517 if (_uncommit_thread != nullptr) {
2518 _uncommit_thread->forbid_uncommit();
2519 }
2520 }
2521
2522 void ShenandoahHeap::allow_uncommit() {
2523 if (_uncommit_thread != nullptr) {
2524 _uncommit_thread->allow_uncommit();
2525 }
2526 }
2527
2528 #ifdef ASSERT
2529 bool ShenandoahHeap::is_uncommit_in_progress() {
2530 if (_uncommit_thread != nullptr) {
2531 return _uncommit_thread->is_uncommit_in_progress();
2532 }
2533 return false;
2534 }
2535 #endif
2536
2537 void ShenandoahHeap::safepoint_synchronize_begin() {
2538 StackWatermarkSet::safepoint_synchronize_begin();
2539 SuspendibleThreadSet::synchronize();
2540 }
2541
2542 void ShenandoahHeap::safepoint_synchronize_end() {
2543 SuspendibleThreadSet::desynchronize();
2544 }
2545
2546 void ShenandoahHeap::try_inject_alloc_failure() {
2547 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2548 _inject_alloc_failure.set();
2549 os::naked_short_sleep(1);
2550 if (cancelled_gc()) {
2551 log_info(gc)("Allocation failure was successfully injected");
2552 }
2553 }
2554 }
2555
2556 bool ShenandoahHeap::should_inject_alloc_failure() {
2557 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2558 }
2559
2560 void ShenandoahHeap::initialize_serviceability() {
2561 _memory_pool = new ShenandoahMemoryPool(this);
2562 _cycle_memory_manager.add_pool(_memory_pool);
2563 _stw_memory_manager.add_pool(_memory_pool);
2564 }
2565
2566 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2567 GrowableArray<GCMemoryManager*> memory_managers(2);
2568 memory_managers.append(&_cycle_memory_manager);
2569 memory_managers.append(&_stw_memory_manager);
2570 return memory_managers;
2571 }
2572
2573 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2574 GrowableArray<MemoryPool*> memory_pools(1);
2575 memory_pools.append(_memory_pool);
2576 return memory_pools;
2577 }
2578
2579 MemoryUsage ShenandoahHeap::memory_usage() {
2580 return MemoryUsage(_initial_size, used(), committed(), max_capacity());
2581 }
2582
2583 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2584 _heap(ShenandoahHeap::heap()),
2585 _index(0) {}
2586
2587 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2588 _heap(heap),
2589 _index(0) {}
2590
2591 void ShenandoahRegionIterator::reset() {
2592 _index = 0;
2593 }
2594
2595 bool ShenandoahRegionIterator::has_next() const {
2596 return _index < _heap->num_regions();
2597 }
2598
2599 char ShenandoahHeap::gc_state() const {
2600 return _gc_state.raw_value();
2601 }
2602
2603 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2604 #ifdef ASSERT
2605 assert(_liveness_cache != nullptr, "sanity");
2606 assert(worker_id < _max_workers, "sanity");
2607 for (uint i = 0; i < num_regions(); i++) {
2608 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2609 }
2610 #endif
2611 return _liveness_cache[worker_id];
2612 }
2613
2614 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2615 assert(worker_id < _max_workers, "sanity");
2616 assert(_liveness_cache != nullptr, "sanity");
2617 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2618 for (uint i = 0; i < num_regions(); i++) {
2619 ShenandoahLiveData live = ld[i];
2620 if (live > 0) {
2621 ShenandoahHeapRegion* r = get_region(i);
2622 r->increase_live_data_gc_words(live);
2623 ld[i] = 0;
2624 }
2625 }
2626 }
2627
2628 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2629 if (is_idle()) return false;
2630
2631 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2632 // marking phase.
2633 if (is_concurrent_mark_in_progress() &&
2634 !marking_context()->allocated_after_mark_start(obj)) {
2635 return true;
2636 }
2637
2638 // Can not guarantee obj is deeply good.
2639 if (has_forwarded_objects()) {
2640 return true;
2641 }
2642
2643 return false;
2644 }
2645
2646 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2647 #if INCLUDE_CDS_JAVA_HEAP
2648 // CDS wants a continuous memory range to load a bunch of objects.
2649 // This effectively bypasses normal allocation paths, and requires
2650 // a bit of massaging to unbreak GC invariants.
2651
2652 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
2653
2654 // Easy case: a single regular region, no further adjustments needed.
2655 if (!ShenandoahHeapRegion::requires_humongous(size)) {
2656 return allocate_memory(req);
2657 }
2658
2659 // Hard case: the requested size would cause a humongous allocation.
2660 // We need to make sure it looks like regular allocation to the rest of GC.
2661
2662 // CDS code would guarantee no objects straddle multiple regions, as long as
2663 // regions are as large as MIN_GC_REGION_ALIGNMENT. It is impractical at this
2664 // point to deal with case when Shenandoah runs with smaller regions.
2665 // TODO: This check can be dropped once MIN_GC_REGION_ALIGNMENT agrees more with Shenandoah.
2666 if (ShenandoahHeapRegion::region_size_bytes() < ArchiveHeapWriter::MIN_GC_REGION_ALIGNMENT) {
2667 return nullptr;
2668 }
2669
2670 HeapWord* mem = allocate_memory(req);
2671 size_t start_idx = heap_region_index_containing(mem);
2672 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
2673
2674 // Flip humongous -> regular.
2675 {
2676 ShenandoahHeapLocker locker(lock(), false);
2677 for (size_t c = start_idx; c < start_idx + num_regions; c++) {
2678 get_region(c)->make_regular_bypass();
2679 }
2680 }
2681
2682 return mem;
2683 #else
2684 assert(false, "Archive heap loader should not be available, should not be here");
2685 return nullptr;
2686 #endif // INCLUDE_CDS_JAVA_HEAP
2687 }
2688
2689 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2690 // Nothing to do here, except checking that heap looks fine.
2691 #ifdef ASSERT
2692 HeapWord* start = archive_space.start();
2693 HeapWord* end = archive_space.end();
2694
2695 // No unclaimed space between the objects.
2696 // Objects are properly allocated in correct regions.
2697 HeapWord* cur = start;
2698 while (cur < end) {
2699 oop oop = cast_to_oop(cur);
2700 shenandoah_assert_in_correct_region(nullptr, oop);
2701 cur += oop->size();
2702 }
2703
2704 // No unclaimed tail at the end of archive space.
2705 assert(cur == end,
2706 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2707 p2i(cur), p2i(end));
2708
2709 // Region bounds are good.
2710 ShenandoahHeapRegion* begin_reg = heap_region_containing(start);
2711 ShenandoahHeapRegion* end_reg = heap_region_containing(end);
2712 assert(begin_reg->is_regular(), "Must be");
2713 assert(end_reg->is_regular(), "Must be");
2714 assert(begin_reg->bottom() == start,
2715 "Must agree: archive-space-start: " PTR_FORMAT ", begin-region-bottom: " PTR_FORMAT,
2716 p2i(start), p2i(begin_reg->bottom()));
2717 assert(end_reg->top() == end,
2718 "Must agree: archive-space-end: " PTR_FORMAT ", end-region-top: " PTR_FORMAT,
2719 p2i(end), p2i(end_reg->top()));
2720 #endif
2721 }
2722
2723 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2724 if (!mode()->is_generational()) {
2725 return global_generation();
2726 } else if (affiliation == YOUNG_GENERATION) {
2727 return young_generation();
2728 } else if (affiliation == OLD_GENERATION) {
2729 return old_generation();
2730 }
2731
2732 ShouldNotReachHere();
2733 return nullptr;
2734 }
2735
2736 void ShenandoahHeap::log_heap_status(const char* msg) const {
2737 if (mode()->is_generational()) {
2738 young_generation()->log_status(msg);
2739 old_generation()->log_status(msg);
2740 } else {
2741 global_generation()->log_status(msg);
2742 }
2743 }
2744