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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/universe.hpp"
29
30 #include "gc/shared/classUnloadingContext.hpp"
31 #include "gc/shared/gcArguments.hpp"
32 #include "gc/shared/gcTimer.hpp"
33 #include "gc/shared/gcTraceTime.inline.hpp"
34 #include "gc/shared/locationPrinter.inline.hpp"
35 #include "gc/shared/memAllocator.hpp"
36 #include "gc/shared/plab.hpp"
37 #include "gc/shared/tlab_globals.hpp"
38
39 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
40 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
41 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
42 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
43 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
44 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
45 #include "gc/shenandoah/shenandoahControlThread.hpp"
46 #include "gc/shenandoah/shenandoahFreeSet.hpp"
47 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
48 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
49 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
50 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
51 #include "gc/shenandoah/shenandoahInitLogger.hpp"
52 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
53 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
54 #include "gc/shenandoah/shenandoahMetrics.hpp"
55 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
56 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
57 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
58 #include "gc/shenandoah/shenandoahPadding.hpp"
59 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
60 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
61 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
62 #include "gc/shenandoah/shenandoahSTWMark.hpp"
63 #include "gc/shenandoah/shenandoahUtils.hpp"
64 #include "gc/shenandoah/shenandoahVerifier.hpp"
65 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
66 #include "gc/shenandoah/shenandoahVMOperations.hpp"
67 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
68 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
69 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
70 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
71 #if INCLUDE_JFR
72 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
73 #endif
74
75 #include "classfile/systemDictionary.hpp"
76 #include "code/codeCache.hpp"
77 #include "memory/classLoaderMetaspace.hpp"
78 #include "memory/metaspaceUtils.hpp"
79 #include "nmt/mallocTracker.hpp"
80 #include "nmt/memTracker.hpp"
81 #include "oops/compressedOops.inline.hpp"
82 #include "prims/jvmtiTagMap.hpp"
83 #include "runtime/atomic.hpp"
84 #include "runtime/globals.hpp"
85 #include "runtime/interfaceSupport.inline.hpp"
86 #include "runtime/java.hpp"
87 #include "runtime/orderAccess.hpp"
88 #include "runtime/safepointMechanism.hpp"
89 #include "runtime/stackWatermarkSet.hpp"
90 #include "runtime/vmThread.hpp"
91 #include "utilities/events.hpp"
92 #include "utilities/powerOfTwo.hpp"
93
94 class ShenandoahPretouchHeapTask : public WorkerTask {
95 private:
96 ShenandoahRegionIterator _regions;
97 const size_t _page_size;
98 public:
99 ShenandoahPretouchHeapTask(size_t page_size) :
100 WorkerTask("Shenandoah Pretouch Heap"),
101 _page_size(page_size) {}
102
103 virtual void work(uint worker_id) {
104 ShenandoahHeapRegion* r = _regions.next();
105 while (r != nullptr) {
106 if (r->is_committed()) {
107 os::pretouch_memory(r->bottom(), r->end(), _page_size);
108 }
109 r = _regions.next();
110 }
111 }
112 };
113
114 class ShenandoahPretouchBitmapTask : public WorkerTask {
115 private:
116 ShenandoahRegionIterator _regions;
117 char* _bitmap_base;
118 const size_t _bitmap_size;
119 const size_t _page_size;
120 public:
121 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
122 WorkerTask("Shenandoah Pretouch Bitmap"),
123 _bitmap_base(bitmap_base),
124 _bitmap_size(bitmap_size),
125 _page_size(page_size) {}
126
127 virtual void work(uint worker_id) {
128 ShenandoahHeapRegion* r = _regions.next();
129 while (r != nullptr) {
130 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
131 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
132 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
133
134 if (r->is_committed()) {
135 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
136 }
137
138 r = _regions.next();
139 }
140 }
141 };
142
143 jint ShenandoahHeap::initialize() {
144 //
145 // Figure out heap sizing
146 //
147
148 size_t init_byte_size = InitialHeapSize;
149 size_t min_byte_size = MinHeapSize;
150 size_t max_byte_size = MaxHeapSize;
151 size_t heap_alignment = HeapAlignment;
152
153 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
154
155 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
156 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
157
158 _num_regions = ShenandoahHeapRegion::region_count();
159 assert(_num_regions == (max_byte_size / reg_size_bytes),
160 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
161 _num_regions, max_byte_size, reg_size_bytes);
162
163 // Now we know the number of regions, initialize the heuristics.
164 initialize_heuristics();
165
166 size_t num_committed_regions = init_byte_size / reg_size_bytes;
167 num_committed_regions = MIN2(num_committed_regions, _num_regions);
168 assert(num_committed_regions <= _num_regions, "sanity");
169 _initial_size = num_committed_regions * reg_size_bytes;
170
171 size_t num_min_regions = min_byte_size / reg_size_bytes;
172 num_min_regions = MIN2(num_min_regions, _num_regions);
173 assert(num_min_regions <= _num_regions, "sanity");
174 _minimum_size = num_min_regions * reg_size_bytes;
175
176 // Default to max heap size.
177 _soft_max_size = _num_regions * reg_size_bytes;
178
179 _committed = _initial_size;
180
181 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
182 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
183 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
184
185 //
186 // Reserve and commit memory for heap
187 //
188
189 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
190 initialize_reserved_region(heap_rs);
191 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
192 _heap_region_special = heap_rs.special();
193
194 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
195 "Misaligned heap: " PTR_FORMAT, p2i(base()));
196 os::trace_page_sizes_for_requested_size("Heap",
197 max_byte_size, heap_alignment,
198 heap_rs.base(),
199 heap_rs.size(), heap_rs.page_size());
200
201 #if SHENANDOAH_OPTIMIZED_MARKTASK
202 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
203 // Fail if we ever attempt to address more than we can.
204 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
205 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
206 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
207 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
208 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
209 vm_exit_during_initialization("Fatal Error", buf);
210 }
211 #endif
212
213 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
214 if (!_heap_region_special) {
215 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
216 "Cannot commit heap memory");
217 }
218
219 //
220 // Reserve and commit memory for bitmap(s)
221 //
222
223 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
224 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
225
226 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
227
228 guarantee(bitmap_bytes_per_region != 0,
229 "Bitmap bytes per region should not be zero");
230 guarantee(is_power_of_2(bitmap_bytes_per_region),
231 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
232
233 if (bitmap_page_size > bitmap_bytes_per_region) {
234 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
235 _bitmap_bytes_per_slice = bitmap_page_size;
236 } else {
237 _bitmap_regions_per_slice = 1;
238 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
239 }
240
241 guarantee(_bitmap_regions_per_slice >= 1,
242 "Should have at least one region per slice: " SIZE_FORMAT,
243 _bitmap_regions_per_slice);
244
245 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
246 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
247 _bitmap_bytes_per_slice, bitmap_page_size);
248
249 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
250 os::trace_page_sizes_for_requested_size("Mark Bitmap",
251 bitmap_size_orig, bitmap_page_size,
252 bitmap.base(),
253 bitmap.size(), bitmap.page_size());
254 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
255 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
256 _bitmap_region_special = bitmap.special();
257
258 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
259 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
260 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
261 if (!_bitmap_region_special) {
262 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
263 "Cannot commit bitmap memory");
264 }
265
266 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions, _max_workers);
267
268 if (ShenandoahVerify) {
269 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
270 os::trace_page_sizes_for_requested_size("Verify Bitmap",
271 bitmap_size_orig, bitmap_page_size,
272 verify_bitmap.base(),
273 verify_bitmap.size(), verify_bitmap.page_size());
274 if (!verify_bitmap.special()) {
275 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
276 "Cannot commit verification bitmap memory");
277 }
278 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
279 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
280 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
281 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
282 }
283
284 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
285 size_t aux_bitmap_page_size = bitmap_page_size;
286
287 ReservedSpace aux_bitmap(_bitmap_size, aux_bitmap_page_size);
288 os::trace_page_sizes_for_requested_size("Aux Bitmap",
289 bitmap_size_orig, aux_bitmap_page_size,
290 aux_bitmap.base(),
291 aux_bitmap.size(), aux_bitmap.page_size());
292 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
293 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
294 _aux_bitmap_region_special = aux_bitmap.special();
295 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
296
297 //
298 // Create regions and region sets
299 //
300 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
301 size_t region_storage_size_orig = region_align * _num_regions;
302 size_t region_storage_size = align_up(region_storage_size_orig,
303 MAX2(region_page_size, os::vm_allocation_granularity()));
304
305 ReservedSpace region_storage(region_storage_size, region_page_size);
306 os::trace_page_sizes_for_requested_size("Region Storage",
307 region_storage_size_orig, region_page_size,
308 region_storage.base(),
309 region_storage.size(), region_storage.page_size());
310 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
311 if (!region_storage.special()) {
312 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
313 "Cannot commit region memory");
314 }
315
316 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
317 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
318 // If not successful, bite a bullet and allocate at whatever address.
319 {
320 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
321 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
322 const size_t cset_page_size = os::vm_page_size();
323
324 uintptr_t min = round_up_power_of_2(cset_align);
325 uintptr_t max = (1u << 30u);
326 ReservedSpace cset_rs;
327
328 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
329 char* req_addr = (char*)addr;
330 assert(is_aligned(req_addr, cset_align), "Should be aligned");
331 cset_rs = ReservedSpace(cset_size, cset_align, cset_page_size, req_addr);
332 if (cset_rs.is_reserved()) {
333 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
334 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
335 break;
336 }
337 }
338
339 if (_collection_set == nullptr) {
340 cset_rs = ReservedSpace(cset_size, cset_align, os::vm_page_size());
341 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
342 }
343 os::trace_page_sizes_for_requested_size("Collection Set",
344 cset_size, cset_page_size,
345 cset_rs.base(),
346 cset_rs.size(), cset_rs.page_size());
347 }
348
349 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
350 _free_set = new ShenandoahFreeSet(this, _num_regions);
351
352 {
353 ShenandoahHeapLocker locker(lock());
354
355 for (size_t i = 0; i < _num_regions; i++) {
356 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
357 bool is_committed = i < num_committed_regions;
358 void* loc = region_storage.base() + i * region_align;
359
360 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
361 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
362
363 _marking_context->initialize_top_at_mark_start(r);
364 _regions[i] = r;
365 assert(!collection_set()->is_in(i), "New region should not be in collection set");
366 }
367
368 // Initialize to complete
369 _marking_context->mark_complete();
370
371 _free_set->rebuild();
372 }
373
374 if (AlwaysPreTouch) {
375 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
376 // before initialize() below zeroes it with initializing thread. For any given region,
377 // we touch the region and the corresponding bitmaps from the same thread.
378 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
379
380 _pretouch_heap_page_size = heap_page_size;
381 _pretouch_bitmap_page_size = bitmap_page_size;
382
383 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
384 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
385
386 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
387 _workers->run_task(&bcl);
388
389 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
390 _workers->run_task(&hcl);
391 }
392
393 //
394 // Initialize the rest of GC subsystems
395 //
396
397 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
398 for (uint worker = 0; worker < _max_workers; worker++) {
399 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
400 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
401 }
402
403 // There should probably be Shenandoah-specific options for these,
404 // just as there are G1-specific options.
405 {
406 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
407 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
408 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
409 }
410
411 _monitoring_support = new ShenandoahMonitoringSupport(this);
412 _phase_timings = new ShenandoahPhaseTimings(max_workers());
413 ShenandoahCodeRoots::initialize();
414
415 if (ShenandoahPacing) {
416 _pacer = new ShenandoahPacer(this);
417 _pacer->setup_for_idle();
418 }
419
420 _control_thread = new ShenandoahControlThread();
421
422 ShenandoahInitLogger::print();
423
424 return JNI_OK;
425 }
426
427 void ShenandoahHeap::initialize_mode() {
428 if (ShenandoahGCMode != nullptr) {
429 if (strcmp(ShenandoahGCMode, "satb") == 0) {
430 _gc_mode = new ShenandoahSATBMode();
431 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
432 _gc_mode = new ShenandoahPassiveMode();
433 } else {
434 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
435 }
436 } else {
437 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
438 }
439 _gc_mode->initialize_flags();
440 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
441 vm_exit_during_initialization(
442 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
443 _gc_mode->name()));
444 }
445 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
446 vm_exit_during_initialization(
447 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
448 _gc_mode->name()));
449 }
450 }
451
452 void ShenandoahHeap::initialize_heuristics() {
453 assert(_gc_mode != nullptr, "Must be initialized");
454 _heuristics = _gc_mode->initialize_heuristics();
455
456 if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
457 vm_exit_during_initialization(
458 err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
459 _heuristics->name()));
460 }
461 if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
462 vm_exit_during_initialization(
463 err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
464 _heuristics->name()));
465 }
466 }
467
468 #ifdef _MSC_VER
469 #pragma warning( push )
470 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
471 #endif
472
473 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
474 CollectedHeap(),
475 _initial_size(0),
476 _used(0),
477 _committed(0),
478 _bytes_allocated_since_gc_start(0),
479 _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
480 _workers(nullptr),
481 _safepoint_workers(nullptr),
482 _heap_region_special(false),
483 _num_regions(0),
484 _regions(nullptr),
485 _update_refs_iterator(this),
486 _gc_state_changed(false),
487 _gc_no_progress_count(0),
488 _control_thread(nullptr),
489 _shenandoah_policy(policy),
490 _gc_mode(nullptr),
491 _heuristics(nullptr),
492 _free_set(nullptr),
493 _pacer(nullptr),
494 _verifier(nullptr),
495 _phase_timings(nullptr),
496 _monitoring_support(nullptr),
497 _memory_pool(nullptr),
498 _stw_memory_manager("Shenandoah Pauses"),
499 _cycle_memory_manager("Shenandoah Cycles"),
500 _gc_timer(new ConcurrentGCTimer()),
501 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
502 _ref_processor(new ShenandoahReferenceProcessor(MAX2(_max_workers, 1U))),
503 _marking_context(nullptr),
504 _bitmap_size(0),
505 _bitmap_regions_per_slice(0),
506 _bitmap_bytes_per_slice(0),
507 _bitmap_region_special(false),
508 _aux_bitmap_region_special(false),
509 _liveness_cache(nullptr),
510 _collection_set(nullptr)
511 {
512 // Initialize GC mode early, so we can adjust barrier support
513 initialize_mode();
514 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
515
516 _max_workers = MAX2(_max_workers, 1U);
517 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
518 if (_workers == nullptr) {
519 vm_exit_during_initialization("Failed necessary allocation.");
520 } else {
521 _workers->initialize_workers();
522 }
523
524 if (ParallelGCThreads > 1) {
525 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread",
526 ParallelGCThreads);
527 _safepoint_workers->initialize_workers();
528 }
529 }
530
531 #ifdef _MSC_VER
532 #pragma warning( pop )
533 #endif
534
535 class ShenandoahResetBitmapTask : public WorkerTask {
536 private:
537 ShenandoahRegionIterator _regions;
538
539 public:
540 ShenandoahResetBitmapTask() :
541 WorkerTask("Shenandoah Reset Bitmap") {}
542
543 void work(uint worker_id) {
544 ShenandoahHeapRegion* region = _regions.next();
545 ShenandoahHeap* heap = ShenandoahHeap::heap();
546 ShenandoahMarkingContext* const ctx = heap->marking_context();
547 while (region != nullptr) {
548 if (heap->is_bitmap_slice_committed(region)) {
549 ctx->clear_bitmap(region);
550 }
551 region = _regions.next();
552 }
553 }
554 };
555
556 void ShenandoahHeap::reset_mark_bitmap() {
557 assert_gc_workers(_workers->active_workers());
558 mark_incomplete_marking_context();
559
560 ShenandoahResetBitmapTask task;
561 _workers->run_task(&task);
562 }
563
564 void ShenandoahHeap::print_on(outputStream* st) const {
565 st->print_cr("Shenandoah Heap");
566 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
567 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
568 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
569 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
570 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
571 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
572 num_regions(),
573 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
574 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
575
576 st->print("Status: ");
577 if (has_forwarded_objects()) st->print("has forwarded objects, ");
578 if (is_concurrent_mark_in_progress()) st->print("marking, ");
579 if (is_evacuation_in_progress()) st->print("evacuating, ");
580 if (is_update_refs_in_progress()) st->print("updating refs, ");
581 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
582 if (is_full_gc_in_progress()) st->print("full gc, ");
583 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
584 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
585 if (is_concurrent_strong_root_in_progress() &&
586 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
587
588 if (cancelled_gc()) {
589 st->print("cancelled");
590 } else {
591 st->print("not cancelled");
592 }
593 st->cr();
594
595 st->print_cr("Reserved region:");
596 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
597 p2i(reserved_region().start()),
598 p2i(reserved_region().end()));
599
600 ShenandoahCollectionSet* cset = collection_set();
601 st->print_cr("Collection set:");
602 if (cset != nullptr) {
603 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
604 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
605 } else {
606 st->print_cr(" (null)");
607 }
608
609 st->cr();
610 MetaspaceUtils::print_on(st);
611
612 if (Verbose) {
613 st->cr();
614 print_heap_regions_on(st);
615 }
616 }
617
618 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
619 public:
620 void do_thread(Thread* thread) {
621 assert(thread != nullptr, "Sanity");
622 assert(thread->is_Worker_thread(), "Only worker thread expected");
623 ShenandoahThreadLocalData::initialize_gclab(thread);
624 }
625 };
626
627 void ShenandoahHeap::post_initialize() {
628 CollectedHeap::post_initialize();
629 MutexLocker ml(Threads_lock);
630
631 ShenandoahInitWorkerGCLABClosure init_gclabs;
632 _workers->threads_do(&init_gclabs);
633
634 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
635 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
636 _workers->set_initialize_gclab();
637 if (_safepoint_workers != nullptr) {
638 _safepoint_workers->threads_do(&init_gclabs);
639 _safepoint_workers->set_initialize_gclab();
640 }
641
642 _heuristics->initialize();
643
644 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
645 }
646
647 size_t ShenandoahHeap::used() const {
648 return Atomic::load(&_used);
649 }
650
651 size_t ShenandoahHeap::committed() const {
652 return Atomic::load(&_committed);
653 }
654
655 size_t ShenandoahHeap::available() const {
656 return free_set()->available();
657 }
658
659 void ShenandoahHeap::increase_committed(size_t bytes) {
660 shenandoah_assert_heaplocked_or_safepoint();
661 _committed += bytes;
662 }
663
664 void ShenandoahHeap::decrease_committed(size_t bytes) {
665 shenandoah_assert_heaplocked_or_safepoint();
666 _committed -= bytes;
667 }
668
669 void ShenandoahHeap::increase_used(size_t bytes) {
670 Atomic::add(&_used, bytes, memory_order_relaxed);
671 }
672
673 void ShenandoahHeap::set_used(size_t bytes) {
674 Atomic::store(&_used, bytes);
675 }
676
677 void ShenandoahHeap::decrease_used(size_t bytes) {
678 assert(used() >= bytes, "never decrease heap size by more than we've left");
679 Atomic::sub(&_used, bytes, memory_order_relaxed);
680 }
681
682 void ShenandoahHeap::increase_allocated(size_t bytes) {
683 Atomic::add(&_bytes_allocated_since_gc_start, bytes, memory_order_relaxed);
684 }
685
686 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
687 size_t bytes = words * HeapWordSize;
688 if (!waste) {
689 increase_used(bytes);
690 }
691 increase_allocated(bytes);
692 if (ShenandoahPacing) {
693 control_thread()->pacing_notify_alloc(words);
694 if (waste) {
695 pacer()->claim_for_alloc(words, true);
696 }
697 }
698 }
699
700 size_t ShenandoahHeap::capacity() const {
701 return committed();
702 }
703
704 size_t ShenandoahHeap::max_capacity() const {
705 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
706 }
707
708 size_t ShenandoahHeap::soft_max_capacity() const {
709 size_t v = Atomic::load(&_soft_max_size);
710 assert(min_capacity() <= v && v <= max_capacity(),
711 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
712 min_capacity(), v, max_capacity());
713 return v;
714 }
715
716 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
717 assert(min_capacity() <= v && v <= max_capacity(),
718 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
719 min_capacity(), v, max_capacity());
720 Atomic::store(&_soft_max_size, v);
721 }
722
723 size_t ShenandoahHeap::min_capacity() const {
724 return _minimum_size;
725 }
726
727 size_t ShenandoahHeap::initial_capacity() const {
728 return _initial_size;
729 }
730
731 bool ShenandoahHeap::is_in(const void* p) const {
732 HeapWord* heap_base = (HeapWord*) base();
733 HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
734 return p >= heap_base && p < last_region_end;
735 }
736
737 void ShenandoahHeap::maybe_uncommit(double shrink_before, size_t shrink_until) {
738 assert (ShenandoahUncommit, "should be enabled");
739
740 // Determine if there is work to do. This avoids taking heap lock if there is
741 // no work available, avoids spamming logs with superfluous logging messages,
742 // and minimises the amount of work while locks are taken.
743
744 if (committed() <= shrink_until) return;
745
746 bool has_work = false;
747 for (size_t i = 0; i < num_regions(); i++) {
748 ShenandoahHeapRegion* r = get_region(i);
749 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
750 has_work = true;
751 break;
752 }
753 }
754
755 if (has_work) {
756 static const char* msg = "Concurrent uncommit";
757 ShenandoahConcurrentPhase gcPhase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
758 EventMark em("%s", msg);
759
760 op_uncommit(shrink_before, shrink_until);
761 }
762 }
763
764 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
765 assert (ShenandoahUncommit, "should be enabled");
766
767 // Application allocates from the beginning of the heap, and GC allocates at
768 // the end of it. It is more efficient to uncommit from the end, so that applications
769 // could enjoy the near committed regions. GC allocations are much less frequent,
770 // and therefore can accept the committing costs.
771
772 size_t count = 0;
773 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
774 ShenandoahHeapRegion* r = get_region(i - 1);
775 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
776 ShenandoahHeapLocker locker(lock());
777 if (r->is_empty_committed()) {
778 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
779 break;
780 }
781
782 r->make_uncommitted();
783 count++;
784 }
785 }
786 SpinPause(); // allow allocators to take the lock
787 }
788
789 if (count > 0) {
790 notify_heap_changed();
791 }
792 }
793
794 bool ShenandoahHeap::check_soft_max_changed() {
795 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
796 size_t old_soft_max = soft_max_capacity();
797 if (new_soft_max != old_soft_max) {
798 new_soft_max = MAX2(min_capacity(), new_soft_max);
799 new_soft_max = MIN2(max_capacity(), new_soft_max);
800 if (new_soft_max != old_soft_max) {
801 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
802 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
803 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
804 );
805 set_soft_max_capacity(new_soft_max);
806 return true;
807 }
808 }
809 return false;
810 }
811
812 void ShenandoahHeap::notify_heap_changed() {
813 // Update monitoring counters when we took a new region. This amortizes the
814 // update costs on slow path.
815 monitoring_support()->notify_heap_changed();
816
817 // This is called from allocation path, and thus should be fast.
818 _heap_changed.try_set();
819 }
820
821 void ShenandoahHeap::set_forced_counters_update(bool value) {
822 monitoring_support()->set_forced_counters_update(value);
823 }
824
825 void ShenandoahHeap::handle_force_counters_update() {
826 monitoring_support()->handle_force_counters_update();
827 }
828
829 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
830 // New object should fit the GCLAB size
831 size_t min_size = MAX2(size, PLAB::min_size());
832
833 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
834 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
835 new_size = MIN2(new_size, PLAB::max_size());
836 new_size = MAX2(new_size, PLAB::min_size());
837
838 // Record new heuristic value even if we take any shortcut. This captures
839 // the case when moderately-sized objects always take a shortcut. At some point,
840 // heuristics should catch up with them.
841 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
842
843 if (new_size < size) {
844 // New size still does not fit the object. Fall back to shared allocation.
845 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
846 return nullptr;
847 }
848
849 // Retire current GCLAB, and allocate a new one.
850 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
851 gclab->retire();
852
853 size_t actual_size = 0;
854 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
855 if (gclab_buf == nullptr) {
856 return nullptr;
857 }
858
859 assert (size <= actual_size, "allocation should fit");
860
861 // ...and clear or zap just allocated TLAB, if needed.
862 if (ZeroTLAB) {
863 Copy::zero_to_words(gclab_buf, actual_size);
864 } else if (ZapTLAB) {
865 // Skip mangling the space corresponding to the object header to
866 // ensure that the returned space is not considered parsable by
867 // any concurrent GC thread.
868 size_t hdr_size = oopDesc::header_size();
869 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
870 }
871 gclab->set_buf(gclab_buf, actual_size);
872 return gclab->allocate(size);
873 }
874
875 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
876 size_t requested_size,
877 size_t* actual_size) {
878 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
879 HeapWord* res = allocate_memory(req);
880 if (res != nullptr) {
881 *actual_size = req.actual_size();
882 } else {
883 *actual_size = 0;
884 }
885 return res;
886 }
887
888 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
889 size_t word_size,
890 size_t* actual_size) {
891 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
892 HeapWord* res = allocate_memory(req);
893 if (res != nullptr) {
894 *actual_size = req.actual_size();
895 } else {
896 *actual_size = 0;
897 }
898 return res;
899 }
900
901 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
902 intptr_t pacer_epoch = 0;
903 bool in_new_region = false;
904 HeapWord* result = nullptr;
905
906 if (req.is_mutator_alloc()) {
907 if (ShenandoahPacing) {
908 pacer()->pace_for_alloc(req.size());
909 pacer_epoch = pacer()->epoch();
910 }
911
912 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
913 result = allocate_memory_under_lock(req, in_new_region);
914 }
915
916 // Check that gc overhead is not exceeded.
917 //
918 // Shenandoah will grind along for quite a while allocating one
919 // object at a time using shared (non-tlab) allocations. This check
920 // is testing that the GC overhead limit has not been exceeded.
921 // This will notify the collector to start a cycle, but will raise
922 // an OOME to the mutator if the last Full GCs have not made progress.
923 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
924 control_thread()->handle_alloc_failure(req, false);
925 return nullptr;
926 }
927
928 if (result == nullptr) {
929 // Block until control thread reacted, then retry allocation.
930 //
931 // It might happen that one of the threads requesting allocation would unblock
932 // way later after GC happened, only to fail the second allocation, because
933 // other threads have already depleted the free storage. In this case, a better
934 // strategy is to try again, until at least one full GC has completed.
935 //
936 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
937 // a) We experienced a GC that had good progress, or
938 // b) We experienced at least one Full GC (whether or not it had good progress)
939 //
940 // TODO: Consider GLOBAL GC rather than Full GC to remediate OOM condition: https://bugs.openjdk.org/browse/JDK-8335910
941
942 size_t original_count = shenandoah_policy()->full_gc_count();
943 while ((result == nullptr) && (original_count == shenandoah_policy()->full_gc_count())) {
944 control_thread()->handle_alloc_failure(req, true);
945 result = allocate_memory_under_lock(req, in_new_region);
946 }
947 if (result != nullptr) {
948 // If our allocation request has been satisifed after it initially failed, we count this as good gc progress
949 notify_gc_progress();
950 }
951 if (log_is_enabled(Debug, gc, alloc)) {
952 ResourceMark rm;
953 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: " SIZE_FORMAT
954 ", Original: " SIZE_FORMAT ", Latest: " SIZE_FORMAT,
955 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
956 original_count, get_gc_no_progress_count());
957 }
958 }
959 } else {
960 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
961 result = allocate_memory_under_lock(req, in_new_region);
962 // Do not call handle_alloc_failure() here, because we cannot block.
963 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
964 }
965
966 if (in_new_region) {
967 notify_heap_changed();
968 }
969
970 if (result != nullptr) {
971 size_t requested = req.size();
972 size_t actual = req.actual_size();
973
974 assert (req.is_lab_alloc() || (requested == actual),
975 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
976 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
977
978 if (req.is_mutator_alloc()) {
979 notify_mutator_alloc_words(actual, false);
980
981 // If we requested more than we were granted, give the rest back to pacer.
982 // This only matters if we are in the same pacing epoch: do not try to unpace
983 // over the budget for the other phase.
984 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
985 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
986 }
987 } else {
988 increase_used(actual*HeapWordSize);
989 }
990 }
991
992 return result;
993 }
994
995 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
996 // If we are dealing with mutator allocation, then we may need to block for safepoint.
997 // We cannot block for safepoint for GC allocations, because there is a high chance
998 // we are already running at safepoint or from stack watermark machinery, and we cannot
999 // block again.
1000 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1001 return _free_set->allocate(req, in_new_region);
1002 }
1003
1004 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1005 bool* gc_overhead_limit_was_exceeded) {
1006 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1007 return allocate_memory(req);
1008 }
1009
1010 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1011 size_t size,
1012 Metaspace::MetadataType mdtype) {
1013 MetaWord* result;
1014
1015 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1016 if (heuristics()->can_unload_classes()) {
1017 ShenandoahHeuristics* h = heuristics();
1018 h->record_metaspace_oom();
1019 }
1020
1021 // Expand and retry allocation
1022 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1023 if (result != nullptr) {
1024 return result;
1025 }
1026
1027 // Start full GC
1028 collect(GCCause::_metadata_GC_clear_soft_refs);
1029
1030 // Retry allocation
1031 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1032 if (result != nullptr) {
1033 return result;
1034 }
1035
1036 // Expand and retry allocation
1037 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1038 if (result != nullptr) {
1039 return result;
1040 }
1041
1042 // Out of memory
1043 return nullptr;
1044 }
1045
1046 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1047 private:
1048 ShenandoahHeap* const _heap;
1049 Thread* const _thread;
1050 public:
1051 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1052 _heap(heap), _thread(Thread::current()) {}
1053
1054 void do_object(oop p) {
1055 shenandoah_assert_marked(nullptr, p);
1056 if (!p->is_forwarded()) {
1057 _heap->evacuate_object(p, _thread);
1058 }
1059 }
1060 };
1061
1062 class ShenandoahEvacuationTask : public WorkerTask {
1063 private:
1064 ShenandoahHeap* const _sh;
1065 ShenandoahCollectionSet* const _cs;
1066 bool _concurrent;
1067 public:
1068 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1069 ShenandoahCollectionSet* cs,
1070 bool concurrent) :
1071 WorkerTask("Shenandoah Evacuation"),
1072 _sh(sh),
1073 _cs(cs),
1074 _concurrent(concurrent)
1075 {}
1076
1077 void work(uint worker_id) {
1078 if (_concurrent) {
1079 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1080 ShenandoahSuspendibleThreadSetJoiner stsj;
1081 ShenandoahEvacOOMScope oom_evac_scope;
1082 do_work();
1083 } else {
1084 ShenandoahParallelWorkerSession worker_session(worker_id);
1085 ShenandoahEvacOOMScope oom_evac_scope;
1086 do_work();
1087 }
1088 }
1089
1090 private:
1091 void do_work() {
1092 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1093 ShenandoahHeapRegion* r;
1094 while ((r =_cs->claim_next()) != nullptr) {
1095 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1096 _sh->marked_object_iterate(r, &cl);
1097
1098 if (ShenandoahPacing) {
1099 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1100 }
1101
1102 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1103 break;
1104 }
1105 }
1106 }
1107 };
1108
1109 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1110 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1111 workers()->run_task(&task);
1112 }
1113
1114 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1115 if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
1116 // This thread went through the OOM during evac protocol and it is safe to return
1117 // the forward pointer. It must not attempt to evacuate any more.
1118 return ShenandoahBarrierSet::resolve_forwarded(p);
1119 }
1120
1121 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1122
1123 size_t size = p->size();
1124
1125 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
1126
1127 bool alloc_from_gclab = true;
1128 HeapWord* copy = nullptr;
1129
1130 #ifdef ASSERT
1131 if (ShenandoahOOMDuringEvacALot &&
1132 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1133 copy = nullptr;
1134 } else {
1135 #endif
1136 if (UseTLAB) {
1137 copy = allocate_from_gclab(thread, size);
1138 }
1139 if (copy == nullptr) {
1140 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
1141 copy = allocate_memory(req);
1142 alloc_from_gclab = false;
1143 }
1144 #ifdef ASSERT
1145 }
1146 #endif
1147
1148 if (copy == nullptr) {
1149 control_thread()->handle_alloc_failure_evac(size);
1150
1151 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1152
1153 return ShenandoahBarrierSet::resolve_forwarded(p);
1154 }
1155
1156 // Copy the object:
1157 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1158
1159 // Try to install the new forwarding pointer.
1160 oop copy_val = cast_to_oop(copy);
1161 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1162 if (result == copy_val) {
1163 // Successfully evacuated. Our copy is now the public one!
1164 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1165 shenandoah_assert_correct(nullptr, copy_val);
1166 return copy_val;
1167 } else {
1168 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1169 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1170 // But if it happens to contain references to evacuated regions, those references would
1171 // not get updated for this stale copy during this cycle, and we will crash while scanning
1172 // it the next cycle.
1173 //
1174 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
1175 // object will overwrite this stale copy, or the filler object on LAB retirement will
1176 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
1177 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1178 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1179 if (alloc_from_gclab) {
1180 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1181 } else {
1182 fill_with_object(copy, size);
1183 shenandoah_assert_correct(nullptr, copy_val);
1184 }
1185 shenandoah_assert_correct(nullptr, result);
1186 return result;
1187 }
1188 }
1189
1190 void ShenandoahHeap::trash_cset_regions() {
1191 ShenandoahHeapLocker locker(lock());
1192
1193 ShenandoahCollectionSet* set = collection_set();
1194 ShenandoahHeapRegion* r;
1195 set->clear_current_index();
1196 while ((r = set->next()) != nullptr) {
1197 r->make_trash();
1198 }
1199 collection_set()->clear();
1200 }
1201
1202 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1203 st->print_cr("Heap Regions:");
1204 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1205 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1206 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1207 st->print_cr("UWM=update watermark, U=used");
1208 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1209 st->print_cr("S=shared allocs, L=live data");
1210 st->print_cr("CP=critical pins");
1211
1212 for (size_t i = 0; i < num_regions(); i++) {
1213 get_region(i)->print_on(st);
1214 }
1215 }
1216
1217 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1218 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1219
1220 oop humongous_obj = cast_to_oop(start->bottom());
1221 size_t size = humongous_obj->size();
1222 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1223 size_t index = start->index() + required_regions - 1;
1224
1225 assert(!start->has_live(), "liveness must be zero");
1226
1227 for(size_t i = 0; i < required_regions; i++) {
1228 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1229 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1230 ShenandoahHeapRegion* region = get_region(index --);
1231
1232 assert(region->is_humongous(), "expect correct humongous start or continuation");
1233 assert(!region->is_cset(), "Humongous region should not be in collection set");
1234
1235 region->make_trash_immediate();
1236 }
1237 }
1238
1239 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1240 public:
1241 ShenandoahCheckCleanGCLABClosure() {}
1242 void do_thread(Thread* thread) {
1243 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1244 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1245 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1246 }
1247 };
1248
1249 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1250 private:
1251 bool const _resize;
1252 public:
1253 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1254 void do_thread(Thread* thread) {
1255 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1256 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1257 gclab->retire();
1258 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1259 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1260 }
1261 }
1262 };
1263
1264 void ShenandoahHeap::labs_make_parsable() {
1265 assert(UseTLAB, "Only call with UseTLAB");
1266
1267 ShenandoahRetireGCLABClosure cl(false);
1268
1269 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1270 ThreadLocalAllocBuffer& tlab = t->tlab();
1271 tlab.make_parsable();
1272 cl.do_thread(t);
1273 }
1274
1275 workers()->threads_do(&cl);
1276 }
1277
1278 void ShenandoahHeap::tlabs_retire(bool resize) {
1279 assert(UseTLAB, "Only call with UseTLAB");
1280 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1281
1282 ThreadLocalAllocStats stats;
1283
1284 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1285 ThreadLocalAllocBuffer& tlab = t->tlab();
1286 tlab.retire(&stats);
1287 if (resize) {
1288 tlab.resize();
1289 }
1290 }
1291
1292 stats.publish();
1293
1294 #ifdef ASSERT
1295 ShenandoahCheckCleanGCLABClosure cl;
1296 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1297 cl.do_thread(t);
1298 }
1299 workers()->threads_do(&cl);
1300 #endif
1301 }
1302
1303 void ShenandoahHeap::gclabs_retire(bool resize) {
1304 assert(UseTLAB, "Only call with UseTLAB");
1305 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1306
1307 ShenandoahRetireGCLABClosure cl(resize);
1308 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1309 cl.do_thread(t);
1310 }
1311 workers()->threads_do(&cl);
1312
1313 if (safepoint_workers() != nullptr) {
1314 safepoint_workers()->threads_do(&cl);
1315 }
1316 }
1317
1318 // Returns size in bytes
1319 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1320 // Return the max allowed size, and let the allocation path
1321 // figure out the safe size for current allocation.
1322 return ShenandoahHeapRegion::max_tlab_size_bytes();
1323 }
1324
1325 size_t ShenandoahHeap::max_tlab_size() const {
1326 // Returns size in words
1327 return ShenandoahHeapRegion::max_tlab_size_words();
1328 }
1329
1330 void ShenandoahHeap::collect(GCCause::Cause cause) {
1331 control_thread()->request_gc(cause);
1332 }
1333
1334 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1335 //assert(false, "Shouldn't need to do full collections");
1336 }
1337
1338 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1339 ShenandoahHeapRegion* r = heap_region_containing(addr);
1340 if (r != nullptr) {
1341 return r->block_start(addr);
1342 }
1343 return nullptr;
1344 }
1345
1346 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1347 ShenandoahHeapRegion* r = heap_region_containing(addr);
1348 return r->block_is_obj(addr);
1349 }
1350
1351 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1352 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1353 }
1354
1355 void ShenandoahHeap::prepare_for_verify() {
1356 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1357 labs_make_parsable();
1358 }
1359 }
1360
1361 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1362 if (_shenandoah_policy->is_at_shutdown()) {
1363 return;
1364 }
1365
1366 if (_control_thread != nullptr) {
1367 tcl->do_thread(_control_thread);
1368 }
1369
1370 workers()->threads_do(tcl);
1371 if (_safepoint_workers != nullptr) {
1372 _safepoint_workers->threads_do(tcl);
1373 }
1374 }
1375
1376 void ShenandoahHeap::print_tracing_info() const {
1377 LogTarget(Info, gc, stats) lt;
1378 if (lt.is_enabled()) {
1379 ResourceMark rm;
1380 LogStream ls(lt);
1381
1382 phase_timings()->print_global_on(&ls);
1383
1384 ls.cr();
1385 ls.cr();
1386
1387 shenandoah_policy()->print_gc_stats(&ls);
1388
1389 ls.cr();
1390 ls.cr();
1391 }
1392 }
1393
1394 void ShenandoahHeap::verify(VerifyOption vo) {
1395 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1396 if (ShenandoahVerify) {
1397 verifier()->verify_generic(vo);
1398 } else {
1399 // TODO: Consider allocating verification bitmaps on demand,
1400 // and turn this on unconditionally.
1401 }
1402 }
1403 }
1404 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1405 return _free_set->capacity();
1406 }
1407
1408 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1409 private:
1410 MarkBitMap* _bitmap;
1411 ShenandoahScanObjectStack* _oop_stack;
1412 ShenandoahHeap* const _heap;
1413 ShenandoahMarkingContext* const _marking_context;
1414
1415 template <class T>
1416 void do_oop_work(T* p) {
1417 T o = RawAccess<>::oop_load(p);
1418 if (!CompressedOops::is_null(o)) {
1419 oop obj = CompressedOops::decode_not_null(o);
1420 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1421 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1422 return;
1423 }
1424 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1425
1426 assert(oopDesc::is_oop(obj), "must be a valid oop");
1427 if (!_bitmap->is_marked(obj)) {
1428 _bitmap->mark(obj);
1429 _oop_stack->push(obj);
1430 }
1431 }
1432 }
1433 public:
1434 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1435 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1436 _marking_context(_heap->marking_context()) {}
1437 void do_oop(oop* p) { do_oop_work(p); }
1438 void do_oop(narrowOop* p) { do_oop_work(p); }
1439 };
1440
1441 /*
1442 * This is public API, used in preparation of object_iterate().
1443 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1444 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1445 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1446 */
1447 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1448 // No-op.
1449 }
1450
1451 /*
1452 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1453 *
1454 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1455 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1456 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1457 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1458 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1459 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1460 * wiped the bitmap in preparation for next marking).
1461 *
1462 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1463 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1464 * is allowed to report dead objects, but is not required to do so.
1465 */
1466 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1467 // Reset bitmap
1468 if (!prepare_aux_bitmap_for_iteration())
1469 return;
1470
1471 ShenandoahScanObjectStack oop_stack;
1472 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1473 // Seed the stack with root scan
1474 scan_roots_for_iteration(&oop_stack, &oops);
1475
1476 // Work through the oop stack to traverse heap
1477 while (! oop_stack.is_empty()) {
1478 oop obj = oop_stack.pop();
1479 assert(oopDesc::is_oop(obj), "must be a valid oop");
1480 cl->do_object(obj);
1481 obj->oop_iterate(&oops);
1482 }
1483
1484 assert(oop_stack.is_empty(), "should be empty");
1485 // Reclaim bitmap
1486 reclaim_aux_bitmap_for_iteration();
1487 }
1488
1489 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1490 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1491
1492 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1493 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1494 return false;
1495 }
1496 // Reset bitmap
1497 _aux_bit_map.clear();
1498 return true;
1499 }
1500
1501 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1502 // Process GC roots according to current GC cycle
1503 // This populates the work stack with initial objects
1504 // It is important to relinquish the associated locks before diving
1505 // into heap dumper
1506 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1507 ShenandoahHeapIterationRootScanner rp(n_workers);
1508 rp.roots_do(oops);
1509 }
1510
1511 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1512 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1513 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1514 }
1515 }
1516
1517 // Closure for parallelly iterate objects
1518 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1519 private:
1520 MarkBitMap* _bitmap;
1521 ShenandoahObjToScanQueue* _queue;
1522 ShenandoahHeap* const _heap;
1523 ShenandoahMarkingContext* const _marking_context;
1524
1525 template <class T>
1526 void do_oop_work(T* p) {
1527 T o = RawAccess<>::oop_load(p);
1528 if (!CompressedOops::is_null(o)) {
1529 oop obj = CompressedOops::decode_not_null(o);
1530 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1531 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1532 return;
1533 }
1534 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1535
1536 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1537 if (_bitmap->par_mark(obj)) {
1538 _queue->push(ShenandoahMarkTask(obj));
1539 }
1540 }
1541 }
1542 public:
1543 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1544 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1545 _marking_context(_heap->marking_context()) {}
1546 void do_oop(oop* p) { do_oop_work(p); }
1547 void do_oop(narrowOop* p) { do_oop_work(p); }
1548 };
1549
1550 // Object iterator for parallel heap iteraion.
1551 // The root scanning phase happenes in construction as a preparation of
1552 // parallel marking queues.
1553 // Every worker processes it's own marking queue. work-stealing is used
1554 // to balance workload.
1555 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1556 private:
1557 uint _num_workers;
1558 bool _init_ready;
1559 MarkBitMap* _aux_bit_map;
1560 ShenandoahHeap* _heap;
1561 ShenandoahScanObjectStack _roots_stack; // global roots stack
1562 ShenandoahObjToScanQueueSet* _task_queues;
1563 public:
1564 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1565 _num_workers(num_workers),
1566 _init_ready(false),
1567 _aux_bit_map(bitmap),
1568 _heap(ShenandoahHeap::heap()) {
1569 // Initialize bitmap
1570 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1571 if (!_init_ready) {
1572 return;
1573 }
1574
1575 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1576 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1577
1578 _init_ready = prepare_worker_queues();
1579 }
1580
1581 ~ShenandoahParallelObjectIterator() {
1582 // Reclaim bitmap
1583 _heap->reclaim_aux_bitmap_for_iteration();
1584 // Reclaim queue for workers
1585 if (_task_queues!= nullptr) {
1586 for (uint i = 0; i < _num_workers; ++i) {
1587 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1588 if (q != nullptr) {
1589 delete q;
1590 _task_queues->register_queue(i, nullptr);
1591 }
1592 }
1593 delete _task_queues;
1594 _task_queues = nullptr;
1595 }
1596 }
1597
1598 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1599 if (_init_ready) {
1600 object_iterate_parallel(cl, worker_id, _task_queues);
1601 }
1602 }
1603
1604 private:
1605 // Divide global root_stack into worker queues
1606 bool prepare_worker_queues() {
1607 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1608 // Initialize queues for every workers
1609 for (uint i = 0; i < _num_workers; ++i) {
1610 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1611 _task_queues->register_queue(i, task_queue);
1612 }
1613 // Divide roots among the workers. Assume that object referencing distribution
1614 // is related with root kind, use round-robin to make every worker have same chance
1615 // to process every kind of roots
1616 size_t roots_num = _roots_stack.size();
1617 if (roots_num == 0) {
1618 // No work to do
1619 return false;
1620 }
1621
1622 for (uint j = 0; j < roots_num; j++) {
1623 uint stack_id = j % _num_workers;
1624 oop obj = _roots_stack.pop();
1625 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1626 }
1627 return true;
1628 }
1629
1630 void object_iterate_parallel(ObjectClosure* cl,
1631 uint worker_id,
1632 ShenandoahObjToScanQueueSet* queue_set) {
1633 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1634 assert(queue_set != nullptr, "task queue must not be null");
1635
1636 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1637 assert(q != nullptr, "object iterate queue must not be null");
1638
1639 ShenandoahMarkTask t;
1640 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1641
1642 // Work through the queue to traverse heap.
1643 // Steal when there is no task in queue.
1644 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1645 oop obj = t.obj();
1646 assert(oopDesc::is_oop(obj), "must be a valid oop");
1647 cl->do_object(obj);
1648 obj->oop_iterate(&oops);
1649 }
1650 assert(q->is_empty(), "should be empty");
1651 }
1652 };
1653
1654 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1655 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1656 }
1657
1658 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1659 void ShenandoahHeap::keep_alive(oop obj) {
1660 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1661 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1662 }
1663 }
1664
1665 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1666 for (size_t i = 0; i < num_regions(); i++) {
1667 ShenandoahHeapRegion* current = get_region(i);
1668 blk->heap_region_do(current);
1669 }
1670 }
1671
1672 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1673 private:
1674 ShenandoahHeap* const _heap;
1675 ShenandoahHeapRegionClosure* const _blk;
1676 size_t const _stride;
1677
1678 shenandoah_padding(0);
1679 volatile size_t _index;
1680 shenandoah_padding(1);
1681
1682 public:
1683 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
1684 WorkerTask("Shenandoah Parallel Region Operation"),
1685 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
1686
1687 void work(uint worker_id) {
1688 ShenandoahParallelWorkerSession worker_session(worker_id);
1689 size_t stride = _stride;
1690
1691 size_t max = _heap->num_regions();
1692 while (Atomic::load(&_index) < max) {
1693 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1694 size_t start = cur;
1695 size_t end = MIN2(cur + stride, max);
1696 if (start >= max) break;
1697
1698 for (size_t i = cur; i < end; i++) {
1699 ShenandoahHeapRegion* current = _heap->get_region(i);
1700 _blk->heap_region_do(current);
1701 }
1702 }
1703 }
1704 };
1705
1706 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1707 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1708 const uint active_workers = workers()->active_workers();
1709 const size_t n_regions = num_regions();
1710 size_t stride = ShenandoahParallelRegionStride;
1711 if (stride == 0 && active_workers > 1) {
1712 // Automatically derive the stride to balance the work between threads
1713 // evenly. Do not try to split work if below the reasonable threshold.
1714 constexpr size_t threshold = 4096;
1715 stride = n_regions <= threshold ?
1716 threshold :
1717 (n_regions + active_workers - 1) / active_workers;
1718 }
1719
1720 if (n_regions > stride && active_workers > 1) {
1721 ShenandoahParallelHeapRegionTask task(blk, stride);
1722 workers()->run_task(&task);
1723 } else {
1724 heap_region_iterate(blk);
1725 }
1726 }
1727
1728 class ShenandoahRendezvousClosure : public HandshakeClosure {
1729 public:
1730 inline ShenandoahRendezvousClosure(const char* name) : HandshakeClosure(name) {}
1731 inline void do_thread(Thread* thread) {}
1732 };
1733
1734 void ShenandoahHeap::rendezvous_threads(const char* name) {
1735 ShenandoahRendezvousClosure cl(name);
1736 Handshake::execute(&cl);
1737 }
1738
1739 void ShenandoahHeap::recycle_trash() {
1740 free_set()->recycle_trash();
1741 }
1742
1743 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1744 private:
1745 ShenandoahMarkingContext* const _ctx;
1746 public:
1747 ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1748
1749 void heap_region_do(ShenandoahHeapRegion* r) {
1750 if (r->is_active()) {
1751 // Reset live data and set TAMS optimistically. We would recheck these under the pause
1752 // anyway to capture any updates that happened since now.
1753 r->clear_live_data();
1754 _ctx->capture_top_at_mark_start(r);
1755 }
1756 }
1757
1758 bool is_thread_safe() { return true; }
1759 };
1760
1761 void ShenandoahHeap::prepare_gc() {
1762 reset_mark_bitmap();
1763
1764 ShenandoahResetUpdateRegionStateClosure cl;
1765 parallel_heap_region_iterate(&cl);
1766 }
1767
1768 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1769 private:
1770 ShenandoahMarkingContext* const _ctx;
1771 ShenandoahHeapLock* const _lock;
1772
1773 public:
1774 ShenandoahFinalMarkUpdateRegionStateClosure() :
1775 _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1776
1777 void heap_region_do(ShenandoahHeapRegion* r) {
1778 if (r->is_active()) {
1779 // All allocations past TAMS are implicitly live, adjust the region data.
1780 // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1781 HeapWord *tams = _ctx->top_at_mark_start(r);
1782 HeapWord *top = r->top();
1783 if (top > tams) {
1784 r->increase_live_data_alloc_words(pointer_delta(top, tams));
1785 }
1786
1787 // We are about to select the collection set, make sure it knows about
1788 // current pinning status. Also, this allows trashing more regions that
1789 // now have their pinning status dropped.
1790 if (r->is_pinned()) {
1791 if (r->pin_count() == 0) {
1792 ShenandoahHeapLocker locker(_lock);
1793 r->make_unpinned();
1794 }
1795 } else {
1796 if (r->pin_count() > 0) {
1797 ShenandoahHeapLocker locker(_lock);
1798 r->make_pinned();
1799 }
1800 }
1801
1802 // Remember limit for updating refs. It's guaranteed that we get no
1803 // from-space-refs written from here on.
1804 r->set_update_watermark_at_safepoint(r->top());
1805 } else {
1806 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1807 assert(_ctx->top_at_mark_start(r) == r->top(),
1808 "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1809 }
1810 }
1811
1812 bool is_thread_safe() { return true; }
1813 };
1814
1815 void ShenandoahHeap::prepare_regions_and_collection_set(bool concurrent) {
1816 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
1817 {
1818 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states :
1819 ShenandoahPhaseTimings::degen_gc_final_update_region_states);
1820 ShenandoahFinalMarkUpdateRegionStateClosure cl;
1821 parallel_heap_region_iterate(&cl);
1822
1823 assert_pinned_region_status();
1824 }
1825
1826 {
1827 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset :
1828 ShenandoahPhaseTimings::degen_gc_choose_cset);
1829 ShenandoahHeapLocker locker(lock());
1830 _collection_set->clear();
1831 heuristics()->choose_collection_set(_collection_set);
1832 }
1833
1834 {
1835 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset :
1836 ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
1837 ShenandoahHeapLocker locker(lock());
1838 _free_set->rebuild();
1839 }
1840 }
1841
1842 void ShenandoahHeap::do_class_unloading() {
1843 _unloader.unload();
1844 }
1845
1846 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1847 // Weak refs processing
1848 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1849 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1850 ShenandoahTimingsTracker t(phase);
1851 ShenandoahGCWorkerPhase worker_phase(phase);
1852 ref_processor()->process_references(phase, workers(), false /* concurrent */);
1853 }
1854
1855 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1856 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1857
1858 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1859 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1860 // for future GCLABs here.
1861 if (UseTLAB) {
1862 ShenandoahGCPhase phase(concurrent ?
1863 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1864 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1865 gclabs_retire(ResizeTLAB);
1866 }
1867
1868 _update_refs_iterator.reset();
1869 }
1870
1871 void ShenandoahHeap::propagate_gc_state_to_java_threads() {
1872 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1873 if (_gc_state_changed) {
1874 _gc_state_changed = false;
1875 char state = gc_state();
1876 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1877 ShenandoahThreadLocalData::set_gc_state(t, state);
1878 }
1879 }
1880 }
1881
1882 void ShenandoahHeap::set_gc_state(uint mask, bool value) {
1883 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1884 _gc_state.set_cond(mask, value);
1885 _gc_state_changed = true;
1886 }
1887
1888 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1889 assert(!has_forwarded_objects(), "Not expected before/after mark phase");
1890 set_gc_state(MARKING, in_progress);
1891 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1892 }
1893
1894 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1895 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1896 set_gc_state(EVACUATION, in_progress);
1897 }
1898
1899 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
1900 if (in_progress) {
1901 _concurrent_strong_root_in_progress.set();
1902 } else {
1903 _concurrent_strong_root_in_progress.unset();
1904 }
1905 }
1906
1907 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
1908 set_gc_state(WEAK_ROOTS, cond);
1909 }
1910
1911 GCTracer* ShenandoahHeap::tracer() {
1912 return shenandoah_policy()->tracer();
1913 }
1914
1915 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1916 return _free_set->used();
1917 }
1918
1919 bool ShenandoahHeap::try_cancel_gc() {
1920 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1921 return prev == CANCELLABLE;
1922 }
1923
1924 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1925 if (try_cancel_gc()) {
1926 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1927 log_info(gc)("%s", msg.buffer());
1928 Events::log(Thread::current(), "%s", msg.buffer());
1929 }
1930 }
1931
1932 uint ShenandoahHeap::max_workers() {
1933 return _max_workers;
1934 }
1935
1936 void ShenandoahHeap::stop() {
1937 // The shutdown sequence should be able to terminate when GC is running.
1938
1939 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
1940 _shenandoah_policy->record_shutdown();
1941
1942 // Step 1. Notify control thread that we are in shutdown.
1943 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1944 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1945 control_thread()->prepare_for_graceful_shutdown();
1946
1947 // Step 2. Notify GC workers that we are cancelling GC.
1948 cancel_gc(GCCause::_shenandoah_stop_vm);
1949
1950 // Step 3. Wait until GC worker exits normally.
1951 control_thread()->stop();
1952 }
1953
1954 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1955 if (!unload_classes()) return;
1956 ClassUnloadingContext ctx(_workers->active_workers(),
1957 true /* unregister_nmethods_during_purge */,
1958 false /* lock_nmethod_free_separately */);
1959
1960 // Unload classes and purge SystemDictionary.
1961 {
1962 ShenandoahPhaseTimings::Phase phase = full_gc ?
1963 ShenandoahPhaseTimings::full_gc_purge_class_unload :
1964 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
1965 ShenandoahIsAliveSelector is_alive;
1966 {
1967 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
1968 ShenandoahGCPhase gc_phase(phase);
1969 ShenandoahGCWorkerPhase worker_phase(phase);
1970 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
1971
1972 uint num_workers = _workers->active_workers();
1973 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
1974 _workers->run_task(&unlink_task);
1975 }
1976 // Release unloaded nmethods's memory.
1977 ClassUnloadingContext::context()->purge_and_free_nmethods();
1978 }
1979
1980 {
1981 ShenandoahGCPhase phase(full_gc ?
1982 ShenandoahPhaseTimings::full_gc_purge_cldg :
1983 ShenandoahPhaseTimings::degen_gc_purge_cldg);
1984 ClassLoaderDataGraph::purge(true /* at_safepoint */);
1985 }
1986 // Resize and verify metaspace
1987 MetaspaceGC::compute_new_size();
1988 DEBUG_ONLY(MetaspaceUtils::verify();)
1989 }
1990
1991 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
1992 // so they should not have forwarded oops.
1993 // However, we do need to "null" dead oops in the roots, if can not be done
1994 // in concurrent cycles.
1995 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
1996 uint num_workers = _workers->active_workers();
1997 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
1998 ShenandoahPhaseTimings::full_gc_purge_weak_par :
1999 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2000 ShenandoahGCPhase phase(timing_phase);
2001 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2002 // Cleanup weak roots
2003 if (has_forwarded_objects()) {
2004 ShenandoahForwardedIsAliveClosure is_alive;
2005 ShenandoahUpdateRefsClosure keep_alive;
2006 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
2007 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2008 _workers->run_task(&cleaning_task);
2009 } else {
2010 ShenandoahIsAliveClosure is_alive;
2011 #ifdef ASSERT
2012 ShenandoahAssertNotForwardedClosure verify_cl;
2013 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2014 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2015 #else
2016 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2017 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2018 #endif
2019 _workers->run_task(&cleaning_task);
2020 }
2021 }
2022
2023 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2024 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2025 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2026 ShenandoahGCPhase phase(full_gc ?
2027 ShenandoahPhaseTimings::full_gc_purge :
2028 ShenandoahPhaseTimings::degen_gc_purge);
2029 stw_weak_refs(full_gc);
2030 stw_process_weak_roots(full_gc);
2031 stw_unload_classes(full_gc);
2032 }
2033
2034 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2035 set_gc_state(HAS_FORWARDED, cond);
2036 }
2037
2038 void ShenandoahHeap::set_unload_classes(bool uc) {
2039 _unload_classes.set_cond(uc);
2040 }
2041
2042 bool ShenandoahHeap::unload_classes() const {
2043 return _unload_classes.is_set();
2044 }
2045
2046 address ShenandoahHeap::in_cset_fast_test_addr() {
2047 ShenandoahHeap* heap = ShenandoahHeap::heap();
2048 assert(heap->collection_set() != nullptr, "Sanity");
2049 return (address) heap->collection_set()->biased_map_address();
2050 }
2051
2052 size_t ShenandoahHeap::bytes_allocated_since_gc_start() const {
2053 return Atomic::load(&_bytes_allocated_since_gc_start);
2054 }
2055
2056 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2057 Atomic::store(&_bytes_allocated_since_gc_start, (size_t)0);
2058 }
2059
2060 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2061 _degenerated_gc_in_progress.set_cond(in_progress);
2062 }
2063
2064 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2065 _full_gc_in_progress.set_cond(in_progress);
2066 }
2067
2068 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2069 assert (is_full_gc_in_progress(), "should be");
2070 _full_gc_move_in_progress.set_cond(in_progress);
2071 }
2072
2073 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2074 set_gc_state(UPDATEREFS, in_progress);
2075 }
2076
2077 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2078 ShenandoahCodeRoots::register_nmethod(nm);
2079 }
2080
2081 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2082 ShenandoahCodeRoots::unregister_nmethod(nm);
2083 }
2084
2085 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2086 heap_region_containing(o)->record_pin();
2087 }
2088
2089 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2090 ShenandoahHeapRegion* r = heap_region_containing(o);
2091 assert(r != nullptr, "Sanity");
2092 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
2093 r->record_unpin();
2094 }
2095
2096 void ShenandoahHeap::sync_pinned_region_status() {
2097 ShenandoahHeapLocker locker(lock());
2098
2099 for (size_t i = 0; i < num_regions(); i++) {
2100 ShenandoahHeapRegion *r = get_region(i);
2101 if (r->is_active()) {
2102 if (r->is_pinned()) {
2103 if (r->pin_count() == 0) {
2104 r->make_unpinned();
2105 }
2106 } else {
2107 if (r->pin_count() > 0) {
2108 r->make_pinned();
2109 }
2110 }
2111 }
2112 }
2113
2114 assert_pinned_region_status();
2115 }
2116
2117 #ifdef ASSERT
2118 void ShenandoahHeap::assert_pinned_region_status() {
2119 for (size_t i = 0; i < num_regions(); i++) {
2120 ShenandoahHeapRegion* r = get_region(i);
2121 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2122 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2123 }
2124 }
2125 #endif
2126
2127 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2128 return _gc_timer;
2129 }
2130
2131 void ShenandoahHeap::prepare_concurrent_roots() {
2132 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2133 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2134 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2135 set_concurrent_weak_root_in_progress(true);
2136 if (unload_classes()) {
2137 _unloader.prepare();
2138 }
2139 }
2140
2141 void ShenandoahHeap::finish_concurrent_roots() {
2142 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2143 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2144 if (unload_classes()) {
2145 _unloader.finish();
2146 }
2147 }
2148
2149 #ifdef ASSERT
2150 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2151 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2152
2153 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2154 // Use ParallelGCThreads inside safepoints
2155 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2156 ParallelGCThreads, nworkers);
2157 } else {
2158 // Use ConcGCThreads outside safepoints
2159 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2160 ConcGCThreads, nworkers);
2161 }
2162 }
2163 #endif
2164
2165 ShenandoahVerifier* ShenandoahHeap::verifier() {
2166 guarantee(ShenandoahVerify, "Should be enabled");
2167 assert (_verifier != nullptr, "sanity");
2168 return _verifier;
2169 }
2170
2171 template<bool CONCURRENT>
2172 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2173 private:
2174 ShenandoahHeap* _heap;
2175 ShenandoahRegionIterator* _regions;
2176 public:
2177 ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2178 WorkerTask("Shenandoah Update References"),
2179 _heap(ShenandoahHeap::heap()),
2180 _regions(regions) {
2181 }
2182
2183 void work(uint worker_id) {
2184 if (CONCURRENT) {
2185 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2186 ShenandoahSuspendibleThreadSetJoiner stsj;
2187 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2188 } else {
2189 ShenandoahParallelWorkerSession worker_session(worker_id);
2190 do_work<ShenandoahSTWUpdateRefsClosure>(worker_id);
2191 }
2192 }
2193
2194 private:
2195 template<class T>
2196 void do_work(uint worker_id) {
2197 T cl;
2198 if (CONCURRENT && (worker_id == 0)) {
2199 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2200 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2201 size_t cset_regions = _heap->collection_set()->count();
2202 // We cannot transfer any more regions than will be reclaimed when the existing collection set is recycled because
2203 // we need the reclaimed collection set regions to replenish the collector reserves
2204 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2205 }
2206 // If !CONCURRENT, there's no value in expanding Mutator free set
2207
2208 ShenandoahHeapRegion* r = _regions->next();
2209 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2210 while (r != nullptr) {
2211 HeapWord* update_watermark = r->get_update_watermark();
2212 assert (update_watermark >= r->bottom(), "sanity");
2213 if (r->is_active() && !r->is_cset()) {
2214 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2215 }
2216 if (ShenandoahPacing) {
2217 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2218 }
2219 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2220 return;
2221 }
2222 r = _regions->next();
2223 }
2224 }
2225 };
2226
2227 void ShenandoahHeap::update_heap_references(bool concurrent) {
2228 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2229
2230 if (concurrent) {
2231 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2232 workers()->run_task(&task);
2233 } else {
2234 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2235 workers()->run_task(&task);
2236 }
2237 }
2238
2239
2240 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2241 private:
2242 ShenandoahHeapLock* const _lock;
2243
2244 public:
2245 ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2246
2247 void heap_region_do(ShenandoahHeapRegion* r) {
2248 // Drop unnecessary "pinned" state from regions that does not have CP marks
2249 // anymore, as this would allow trashing them.
2250
2251 if (r->is_active()) {
2252 if (r->is_pinned()) {
2253 if (r->pin_count() == 0) {
2254 ShenandoahHeapLocker locker(_lock);
2255 r->make_unpinned();
2256 }
2257 } else {
2258 if (r->pin_count() > 0) {
2259 ShenandoahHeapLocker locker(_lock);
2260 r->make_pinned();
2261 }
2262 }
2263 }
2264 }
2265
2266 bool is_thread_safe() { return true; }
2267 };
2268
2269 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2270 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2271 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2272
2273 {
2274 ShenandoahGCPhase phase(concurrent ?
2275 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2276 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2277 ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2278 parallel_heap_region_iterate(&cl);
2279
2280 assert_pinned_region_status();
2281 }
2282
2283 {
2284 ShenandoahGCPhase phase(concurrent ?
2285 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2286 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2287 trash_cset_regions();
2288 }
2289 }
2290
2291 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2292 {
2293 ShenandoahGCPhase phase(concurrent ?
2294 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2295 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2296 ShenandoahHeapLocker locker(lock());
2297 _free_set->rebuild();
2298 }
2299 }
2300
2301 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2302 print_on(st);
2303 st->cr();
2304 print_heap_regions_on(st);
2305 }
2306
2307 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2308 size_t slice = r->index() / _bitmap_regions_per_slice;
2309
2310 size_t regions_from = _bitmap_regions_per_slice * slice;
2311 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2312 for (size_t g = regions_from; g < regions_to; g++) {
2313 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2314 if (skip_self && g == r->index()) continue;
2315 if (get_region(g)->is_committed()) {
2316 return true;
2317 }
2318 }
2319 return false;
2320 }
2321
2322 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2323 shenandoah_assert_heaplocked();
2324
2325 // Bitmaps in special regions do not need commits
2326 if (_bitmap_region_special) {
2327 return true;
2328 }
2329
2330 if (is_bitmap_slice_committed(r, true)) {
2331 // Some other region from the group is already committed, meaning the bitmap
2332 // slice is already committed, we exit right away.
2333 return true;
2334 }
2335
2336 // Commit the bitmap slice:
2337 size_t slice = r->index() / _bitmap_regions_per_slice;
2338 size_t off = _bitmap_bytes_per_slice * slice;
2339 size_t len = _bitmap_bytes_per_slice;
2340 char* start = (char*) _bitmap_region.start() + off;
2341
2342 if (!os::commit_memory(start, len, false)) {
2343 return false;
2344 }
2345
2346 if (AlwaysPreTouch) {
2347 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2348 }
2349
2350 return true;
2351 }
2352
2353 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2354 shenandoah_assert_heaplocked();
2355
2356 // Bitmaps in special regions do not need uncommits
2357 if (_bitmap_region_special) {
2358 return true;
2359 }
2360
2361 if (is_bitmap_slice_committed(r, true)) {
2362 // Some other region from the group is still committed, meaning the bitmap
2363 // slice is should stay committed, exit right away.
2364 return true;
2365 }
2366
2367 // Uncommit the bitmap slice:
2368 size_t slice = r->index() / _bitmap_regions_per_slice;
2369 size_t off = _bitmap_bytes_per_slice * slice;
2370 size_t len = _bitmap_bytes_per_slice;
2371 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2372 return false;
2373 }
2374 return true;
2375 }
2376
2377 void ShenandoahHeap::safepoint_synchronize_begin() {
2378 StackWatermarkSet::safepoint_synchronize_begin();
2379 SuspendibleThreadSet::synchronize();
2380 }
2381
2382 void ShenandoahHeap::safepoint_synchronize_end() {
2383 SuspendibleThreadSet::desynchronize();
2384 }
2385
2386 void ShenandoahHeap::try_inject_alloc_failure() {
2387 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2388 _inject_alloc_failure.set();
2389 os::naked_short_sleep(1);
2390 if (cancelled_gc()) {
2391 log_info(gc)("Allocation failure was successfully injected");
2392 }
2393 }
2394 }
2395
2396 bool ShenandoahHeap::should_inject_alloc_failure() {
2397 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2398 }
2399
2400 void ShenandoahHeap::initialize_serviceability() {
2401 _memory_pool = new ShenandoahMemoryPool(this);
2402 _cycle_memory_manager.add_pool(_memory_pool);
2403 _stw_memory_manager.add_pool(_memory_pool);
2404 }
2405
2406 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2407 GrowableArray<GCMemoryManager*> memory_managers(2);
2408 memory_managers.append(&_cycle_memory_manager);
2409 memory_managers.append(&_stw_memory_manager);
2410 return memory_managers;
2411 }
2412
2413 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2414 GrowableArray<MemoryPool*> memory_pools(1);
2415 memory_pools.append(_memory_pool);
2416 return memory_pools;
2417 }
2418
2419 MemoryUsage ShenandoahHeap::memory_usage() {
2420 return _memory_pool->get_memory_usage();
2421 }
2422
2423 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2424 _heap(ShenandoahHeap::heap()),
2425 _index(0) {}
2426
2427 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2428 _heap(heap),
2429 _index(0) {}
2430
2431 void ShenandoahRegionIterator::reset() {
2432 _index = 0;
2433 }
2434
2435 bool ShenandoahRegionIterator::has_next() const {
2436 return _index < _heap->num_regions();
2437 }
2438
2439 char ShenandoahHeap::gc_state() const {
2440 return _gc_state.raw_value();
2441 }
2442
2443 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2444 #ifdef ASSERT
2445 assert(_liveness_cache != nullptr, "sanity");
2446 assert(worker_id < _max_workers, "sanity");
2447 for (uint i = 0; i < num_regions(); i++) {
2448 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2449 }
2450 #endif
2451 return _liveness_cache[worker_id];
2452 }
2453
2454 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2455 assert(worker_id < _max_workers, "sanity");
2456 assert(_liveness_cache != nullptr, "sanity");
2457 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2458 for (uint i = 0; i < num_regions(); i++) {
2459 ShenandoahLiveData live = ld[i];
2460 if (live > 0) {
2461 ShenandoahHeapRegion* r = get_region(i);
2462 r->increase_live_data_gc_words(live);
2463 ld[i] = 0;
2464 }
2465 }
2466 }
2467
2468 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2469 if (is_idle()) return false;
2470
2471 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2472 // marking phase.
2473 if (is_concurrent_mark_in_progress() &&
2474 !marking_context()->allocated_after_mark_start(obj)) {
2475 return true;
2476 }
2477
2478 // Can not guarantee obj is deeply good.
2479 if (has_forwarded_objects()) {
2480 return true;
2481 }
2482
2483 return false;
2484 }