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