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