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/fullGCForwarding.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/shenandoahBarrierSet.hpp"
41 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
42 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
43 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
44 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
45 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
46 #include "gc/shenandoah/shenandoahControlThread.hpp"
47 #include "gc/shenandoah/shenandoahFreeSet.hpp"
48 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
49 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
50 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
51 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
52 #include "gc/shenandoah/shenandoahInitLogger.hpp"
53 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
54 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
55 #include "gc/shenandoah/shenandoahMetrics.hpp"
56 #include "gc/shenandoah/shenandoahMonitoringSupport.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 "cds/archiveHeapWriter.hpp"
76 #include "classfile/systemDictionary.hpp"
77 #include "code/codeCache.hpp"
78 #include "memory/classLoaderMetaspace.hpp"
79 #include "memory/metaspaceUtils.hpp"
80 #include "nmt/mallocTracker.hpp"
81 #include "nmt/memTracker.hpp"
82 #include "oops/compressedOops.inline.hpp"
83 #include "prims/jvmtiTagMap.hpp"
84 #include "runtime/atomic.hpp"
85 #include "runtime/globals.hpp"
86 #include "runtime/interfaceSupport.inline.hpp"
87 #include "runtime/java.hpp"
88 #include "runtime/orderAccess.hpp"
89 #include "runtime/safepointMechanism.hpp"
90 #include "runtime/stackWatermarkSet.hpp"
91 #include "runtime/vmThread.hpp"
92 #include "utilities/events.hpp"
93 #include "utilities/powerOfTwo.hpp"
94
95 class ShenandoahPretouchHeapTask : public WorkerTask {
96 private:
97 ShenandoahRegionIterator _regions;
98 const size_t _page_size;
99 public:
100 ShenandoahPretouchHeapTask(size_t page_size) :
101 WorkerTask("Shenandoah Pretouch Heap"),
102 _page_size(page_size) {}
103
104 virtual void work(uint worker_id) {
105 ShenandoahHeapRegion* r = _regions.next();
106 while (r != nullptr) {
107 if (r->is_committed()) {
108 os::pretouch_memory(r->bottom(), r->end(), _page_size);
109 }
110 r = _regions.next();
111 }
112 }
113 };
114
115 class ShenandoahPretouchBitmapTask : public WorkerTask {
116 private:
117 ShenandoahRegionIterator _regions;
118 char* _bitmap_base;
119 const size_t _bitmap_size;
120 const size_t _page_size;
121 public:
122 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
123 WorkerTask("Shenandoah Pretouch Bitmap"),
124 _bitmap_base(bitmap_base),
125 _bitmap_size(bitmap_size),
126 _page_size(page_size) {}
127
128 virtual void work(uint worker_id) {
129 ShenandoahHeapRegion* r = _regions.next();
130 while (r != nullptr) {
131 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
132 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
133 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
134
135 if (r->is_committed()) {
136 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
137 }
138
139 r = _regions.next();
140 }
141 }
142 };
143
144 jint ShenandoahHeap::initialize() {
145 //
146 // Figure out heap sizing
147 //
148
149 size_t init_byte_size = InitialHeapSize;
150 size_t min_byte_size = MinHeapSize;
151 size_t max_byte_size = MaxHeapSize;
152 size_t heap_alignment = HeapAlignment;
153
154 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
155
156 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
157 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
158
159 _num_regions = ShenandoahHeapRegion::region_count();
160 assert(_num_regions == (max_byte_size / reg_size_bytes),
161 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
162 _num_regions, max_byte_size, reg_size_bytes);
163
164 // Now we know the number of regions, initialize the heuristics.
165 initialize_heuristics();
166
167 size_t num_committed_regions = init_byte_size / reg_size_bytes;
168 num_committed_regions = MIN2(num_committed_regions, _num_regions);
169 assert(num_committed_regions <= _num_regions, "sanity");
170 _initial_size = num_committed_regions * reg_size_bytes;
171
172 size_t num_min_regions = min_byte_size / reg_size_bytes;
173 num_min_regions = MIN2(num_min_regions, _num_regions);
174 assert(num_min_regions <= _num_regions, "sanity");
175 _minimum_size = num_min_regions * reg_size_bytes;
176
177 // Default to max heap size.
178 _soft_max_size = _num_regions * reg_size_bytes;
179
180 _committed = _initial_size;
181
182 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
183 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
184 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
185
186 //
187 // Reserve and commit memory for heap
188 //
189
190 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
191 initialize_reserved_region(heap_rs);
192 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
193 _heap_region_special = heap_rs.special();
194
195 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
196 "Misaligned heap: " PTR_FORMAT, p2i(base()));
197 os::trace_page_sizes_for_requested_size("Heap",
198 max_byte_size, heap_alignment,
199 heap_rs.base(),
200 heap_rs.size(), heap_rs.page_size());
201
202 #if SHENANDOAH_OPTIMIZED_MARKTASK
203 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
204 // Fail if we ever attempt to address more than we can.
205 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
206 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
207 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
208 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
209 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
210 vm_exit_during_initialization("Fatal Error", buf);
211 }
212 #endif
213
214 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
215 if (!_heap_region_special) {
216 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
217 "Cannot commit heap memory");
218 }
219
220 //
221 // Reserve and commit memory for bitmap(s)
222 //
223
224 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
225 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
226
227 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
228
229 guarantee(bitmap_bytes_per_region != 0,
230 "Bitmap bytes per region should not be zero");
231 guarantee(is_power_of_2(bitmap_bytes_per_region),
232 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
233
234 if (bitmap_page_size > bitmap_bytes_per_region) {
235 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
236 _bitmap_bytes_per_slice = bitmap_page_size;
237 } else {
238 _bitmap_regions_per_slice = 1;
239 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
240 }
241
242 guarantee(_bitmap_regions_per_slice >= 1,
243 "Should have at least one region per slice: " SIZE_FORMAT,
244 _bitmap_regions_per_slice);
245
246 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
247 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
248 _bitmap_bytes_per_slice, bitmap_page_size);
249
250 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
251 os::trace_page_sizes_for_requested_size("Mark Bitmap",
252 bitmap_size_orig, bitmap_page_size,
253 bitmap.base(),
254 bitmap.size(), bitmap.page_size());
255 MemTracker::record_virtual_memory_tag(bitmap.base(), mtGC);
256 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
257 _bitmap_region_special = bitmap.special();
258
259 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
260 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
261 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
262 if (!_bitmap_region_special) {
263 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
264 "Cannot commit bitmap memory");
265 }
266
267 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions, _max_workers);
268
269 if (ShenandoahVerify) {
270 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
271 os::trace_page_sizes_for_requested_size("Verify Bitmap",
272 bitmap_size_orig, bitmap_page_size,
273 verify_bitmap.base(),
274 verify_bitmap.size(), verify_bitmap.page_size());
275 if (!verify_bitmap.special()) {
276 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
277 "Cannot commit verification bitmap memory");
278 }
279 MemTracker::record_virtual_memory_tag(verify_bitmap.base(), mtGC);
280 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
281 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
282 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
283 }
284
285 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
286 size_t aux_bitmap_page_size = bitmap_page_size;
287
288 ReservedSpace aux_bitmap(_bitmap_size, aux_bitmap_page_size);
289 os::trace_page_sizes_for_requested_size("Aux Bitmap",
290 bitmap_size_orig, aux_bitmap_page_size,
291 aux_bitmap.base(),
292 aux_bitmap.size(), aux_bitmap.page_size());
293 MemTracker::record_virtual_memory_tag(aux_bitmap.base(), mtGC);
294 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
295 _aux_bitmap_region_special = aux_bitmap.special();
296 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
297
298 //
299 // Create regions and region sets
300 //
301 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
302 size_t region_storage_size_orig = region_align * _num_regions;
303 size_t region_storage_size = align_up(region_storage_size_orig,
304 MAX2(region_page_size, os::vm_allocation_granularity()));
305
306 ReservedSpace region_storage(region_storage_size, region_page_size);
307 os::trace_page_sizes_for_requested_size("Region Storage",
308 region_storage_size_orig, region_page_size,
309 region_storage.base(),
310 region_storage.size(), region_storage.page_size());
311 MemTracker::record_virtual_memory_tag(region_storage.base(), mtGC);
312 if (!region_storage.special()) {
313 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
314 "Cannot commit region memory");
315 }
316
317 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
318 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
319 // If not successful, bite a bullet and allocate at whatever address.
320 {
321 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
322 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
323 const size_t cset_page_size = os::vm_page_size();
324
325 uintptr_t min = round_up_power_of_2(cset_align);
326 uintptr_t max = (1u << 30u);
327 ReservedSpace cset_rs;
328
329 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
330 char* req_addr = (char*)addr;
331 assert(is_aligned(req_addr, cset_align), "Should be aligned");
332 cset_rs = ReservedSpace(cset_size, cset_align, cset_page_size, req_addr);
333 if (cset_rs.is_reserved()) {
334 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
335 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
336 break;
337 }
338 }
339
340 if (_collection_set == nullptr) {
341 cset_rs = ReservedSpace(cset_size, cset_align, os::vm_page_size());
342 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
343 }
344 os::trace_page_sizes_for_requested_size("Collection Set",
345 cset_size, cset_page_size,
346 cset_rs.base(),
347 cset_rs.size(), cset_rs.page_size());
348 }
349
350 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
351 _free_set = new ShenandoahFreeSet(this, _num_regions);
352
353 {
354 ShenandoahHeapLocker locker(lock());
355
356 for (size_t i = 0; i < _num_regions; i++) {
357 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
358 bool is_committed = i < num_committed_regions;
359 void* loc = region_storage.base() + i * region_align;
360
361 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
362 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
363
364 _marking_context->initialize_top_at_mark_start(r);
365 _regions[i] = r;
366 assert(!collection_set()->is_in(i), "New region should not be in collection set");
367 }
368
369 // Initialize to complete
370 _marking_context->mark_complete();
371
372 _free_set->rebuild();
373 }
374
375 if (AlwaysPreTouch) {
376 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
377 // before initialize() below zeroes it with initializing thread. For any given region,
378 // we touch the region and the corresponding bitmaps from the same thread.
379 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
380
381 _pretouch_heap_page_size = heap_page_size;
382 _pretouch_bitmap_page_size = bitmap_page_size;
383
384 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
385 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
386
387 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
388 _workers->run_task(&bcl);
389
390 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
391 _workers->run_task(&hcl);
392 }
393
394 //
395 // Initialize the rest of GC subsystems
396 //
397
398 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
399 for (uint worker = 0; worker < _max_workers; worker++) {
400 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
401 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
402 }
403
404 // There should probably be Shenandoah-specific options for these,
405 // just as there are G1-specific options.
406 {
407 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
408 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
409 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
410 }
411
412 _monitoring_support = new ShenandoahMonitoringSupport(this);
413 _phase_timings = new ShenandoahPhaseTimings(max_workers());
414 ShenandoahCodeRoots::initialize();
415
416 if (ShenandoahPacing) {
417 _pacer = new ShenandoahPacer(this);
418 _pacer->setup_for_idle();
419 }
420
421 _control_thread = new ShenandoahControlThread();
422
423 ShenandoahInitLogger::print();
424
425 FullGCForwarding::initialize(_heap_region);
426
427 return JNI_OK;
428 }
429
430 void ShenandoahHeap::initialize_mode() {
431 if (ShenandoahGCMode != nullptr) {
432 if (strcmp(ShenandoahGCMode, "satb") == 0) {
433 _gc_mode = new ShenandoahSATBMode();
434 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
435 _gc_mode = new ShenandoahPassiveMode();
436 } else {
437 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
438 }
439 } else {
440 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
441 }
442 _gc_mode->initialize_flags();
443 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
444 vm_exit_during_initialization(
445 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
446 _gc_mode->name()));
447 }
448 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
449 vm_exit_during_initialization(
450 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
451 _gc_mode->name()));
452 }
453 }
454
455 void ShenandoahHeap::initialize_heuristics() {
456 assert(_gc_mode != nullptr, "Must be initialized");
457 _heuristics = _gc_mode->initialize_heuristics();
458
459 if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
460 vm_exit_during_initialization(
461 err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
462 _heuristics->name()));
463 }
464 if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
465 vm_exit_during_initialization(
466 err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
467 _heuristics->name()));
468 }
469 }
470
471 #ifdef _MSC_VER
472 #pragma warning( push )
473 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
474 #endif
475
476 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
477 CollectedHeap(),
478 _initial_size(0),
479 _used(0),
480 _committed(0),
481 _bytes_allocated_since_gc_start(0),
482 _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
483 _workers(nullptr),
484 _safepoint_workers(nullptr),
485 _heap_region_special(false),
486 _num_regions(0),
487 _regions(nullptr),
488 _update_refs_iterator(this),
489 _gc_state_changed(false),
490 _gc_no_progress_count(0),
491 _control_thread(nullptr),
492 _shenandoah_policy(policy),
493 _gc_mode(nullptr),
494 _heuristics(nullptr),
495 _free_set(nullptr),
496 _pacer(nullptr),
497 _verifier(nullptr),
498 _phase_timings(nullptr),
499 _monitoring_support(nullptr),
500 _memory_pool(nullptr),
501 _stw_memory_manager("Shenandoah Pauses"),
502 _cycle_memory_manager("Shenandoah Cycles"),
503 _gc_timer(new ConcurrentGCTimer()),
504 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
505 _ref_processor(new ShenandoahReferenceProcessor(MAX2(_max_workers, 1U))),
506 _marking_context(nullptr),
507 _bitmap_size(0),
508 _bitmap_regions_per_slice(0),
509 _bitmap_bytes_per_slice(0),
510 _bitmap_region_special(false),
511 _aux_bitmap_region_special(false),
512 _liveness_cache(nullptr),
513 _collection_set(nullptr)
514 {
515 // Initialize GC mode early, so we can adjust barrier support
516 initialize_mode();
517 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
518
519 _max_workers = MAX2(_max_workers, 1U);
520 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
521 if (_workers == nullptr) {
522 vm_exit_during_initialization("Failed necessary allocation.");
523 } else {
524 _workers->initialize_workers();
525 }
526
527 if (ParallelGCThreads > 1) {
528 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread",
529 ParallelGCThreads);
530 _safepoint_workers->initialize_workers();
531 }
532 }
533
534 #ifdef _MSC_VER
535 #pragma warning( pop )
536 #endif
537
538 class ShenandoahResetBitmapTask : public WorkerTask {
539 private:
540 ShenandoahRegionIterator _regions;
541
542 public:
543 ShenandoahResetBitmapTask() :
544 WorkerTask("Shenandoah Reset Bitmap") {}
545
546 void work(uint worker_id) {
547 ShenandoahHeapRegion* region = _regions.next();
548 ShenandoahHeap* heap = ShenandoahHeap::heap();
549 ShenandoahMarkingContext* const ctx = heap->marking_context();
550 while (region != nullptr) {
551 if (heap->is_bitmap_slice_committed(region)) {
552 ctx->clear_bitmap(region);
553 }
554 region = _regions.next();
555 }
556 }
557 };
558
559 void ShenandoahHeap::reset_mark_bitmap() {
560 assert_gc_workers(_workers->active_workers());
561 mark_incomplete_marking_context();
562
563 ShenandoahResetBitmapTask task;
564 _workers->run_task(&task);
565 }
566
567 void ShenandoahHeap::print_on(outputStream* st) const {
568 st->print_cr("Shenandoah Heap");
569 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
570 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
571 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
572 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
573 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
574 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
575 num_regions(),
576 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
577 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
578
579 st->print("Status: ");
580 if (has_forwarded_objects()) st->print("has forwarded objects, ");
581 if (is_concurrent_mark_in_progress()) st->print("marking, ");
582 if (is_evacuation_in_progress()) st->print("evacuating, ");
583 if (is_update_refs_in_progress()) st->print("updating refs, ");
584 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
585 if (is_full_gc_in_progress()) st->print("full gc, ");
586 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
587 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
588 if (is_concurrent_strong_root_in_progress() &&
589 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
590
591 if (cancelled_gc()) {
592 st->print("cancelled");
593 } else {
594 st->print("not cancelled");
595 }
596 st->cr();
597
598 st->print_cr("Reserved region:");
599 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
600 p2i(reserved_region().start()),
601 p2i(reserved_region().end()));
602
603 ShenandoahCollectionSet* cset = collection_set();
604 st->print_cr("Collection set:");
605 if (cset != nullptr) {
606 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
607 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
608 } else {
609 st->print_cr(" (null)");
610 }
611
612 st->cr();
613 MetaspaceUtils::print_on(st);
614
615 if (Verbose) {
616 st->cr();
617 print_heap_regions_on(st);
618 }
619 }
620
621 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
622 public:
623 void do_thread(Thread* thread) {
624 assert(thread != nullptr, "Sanity");
625 assert(thread->is_Worker_thread(), "Only worker thread expected");
626 ShenandoahThreadLocalData::initialize_gclab(thread);
627 }
628 };
629
630 void ShenandoahHeap::post_initialize() {
631 CollectedHeap::post_initialize();
632 MutexLocker ml(Threads_lock);
633
634 ShenandoahInitWorkerGCLABClosure init_gclabs;
635 _workers->threads_do(&init_gclabs);
636
637 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
638 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
639 _workers->set_initialize_gclab();
640 if (_safepoint_workers != nullptr) {
641 _safepoint_workers->threads_do(&init_gclabs);
642 _safepoint_workers->set_initialize_gclab();
643 }
644
645 _heuristics->initialize();
646
647 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
648 }
649
650 size_t ShenandoahHeap::used() const {
651 return Atomic::load(&_used);
652 }
653
654 size_t ShenandoahHeap::committed() const {
655 return Atomic::load(&_committed);
656 }
657
658 size_t ShenandoahHeap::available() const {
659 return free_set()->available();
660 }
661
662 void ShenandoahHeap::increase_committed(size_t bytes) {
663 shenandoah_assert_heaplocked_or_safepoint();
664 _committed += bytes;
665 }
666
667 void ShenandoahHeap::decrease_committed(size_t bytes) {
668 shenandoah_assert_heaplocked_or_safepoint();
669 _committed -= bytes;
670 }
671
672 void ShenandoahHeap::increase_used(size_t bytes) {
673 Atomic::add(&_used, bytes, memory_order_relaxed);
674 }
675
676 void ShenandoahHeap::set_used(size_t bytes) {
677 Atomic::store(&_used, bytes);
678 }
679
680 void ShenandoahHeap::decrease_used(size_t bytes) {
681 assert(used() >= bytes, "never decrease heap size by more than we've left");
682 Atomic::sub(&_used, bytes, memory_order_relaxed);
683 }
684
685 void ShenandoahHeap::increase_allocated(size_t bytes) {
686 Atomic::add(&_bytes_allocated_since_gc_start, bytes, memory_order_relaxed);
687 }
688
689 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
690 size_t bytes = words * HeapWordSize;
691 if (!waste) {
692 increase_used(bytes);
693 }
694 increase_allocated(bytes);
695 if (ShenandoahPacing) {
696 control_thread()->pacing_notify_alloc(words);
697 if (waste) {
698 pacer()->claim_for_alloc<true>(words);
699 }
700 }
701 }
702
703 size_t ShenandoahHeap::capacity() const {
704 return committed();
705 }
706
707 size_t ShenandoahHeap::max_capacity() const {
708 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
709 }
710
711 size_t ShenandoahHeap::soft_max_capacity() const {
712 size_t v = Atomic::load(&_soft_max_size);
713 assert(min_capacity() <= v && v <= max_capacity(),
714 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
715 min_capacity(), v, max_capacity());
716 return v;
717 }
718
719 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
720 assert(min_capacity() <= v && v <= max_capacity(),
721 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
722 min_capacity(), v, max_capacity());
723 Atomic::store(&_soft_max_size, v);
724 }
725
726 size_t ShenandoahHeap::min_capacity() const {
727 return _minimum_size;
728 }
729
730 size_t ShenandoahHeap::initial_capacity() const {
731 return _initial_size;
732 }
733
734 bool ShenandoahHeap::is_in(const void* p) const {
735 if (is_in_reserved(p)) {
736 if (is_full_gc_move_in_progress()) {
737 // Full GC move is running, we do not have a consistent region
738 // information yet. But we know the pointer is in heap.
739 return true;
740 }
741 // Now check if we point to a live section in active region.
742 ShenandoahHeapRegion* r = heap_region_containing(p);
743 return (r->is_active() && p < r->top());
744 } else {
745 return false;
746 }
747 }
748
749 void ShenandoahHeap::maybe_uncommit(double shrink_before, size_t shrink_until) {
750 assert (ShenandoahUncommit, "should be enabled");
751
752 // Determine if there is work to do. This avoids taking heap lock if there is
753 // no work available, avoids spamming logs with superfluous logging messages,
754 // and minimises the amount of work while locks are taken.
755
756 if (committed() <= shrink_until) return;
757
758 bool has_work = false;
759 for (size_t i = 0; i < num_regions(); i++) {
760 ShenandoahHeapRegion* r = get_region(i);
761 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
762 has_work = true;
763 break;
764 }
765 }
766
767 if (has_work) {
768 static const char* msg = "Concurrent uncommit";
769 ShenandoahConcurrentPhase gcPhase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
770 EventMark em("%s", msg);
771
772 op_uncommit(shrink_before, shrink_until);
773 }
774 }
775
776 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
777 assert (ShenandoahUncommit, "should be enabled");
778
779 // Application allocates from the beginning of the heap, and GC allocates at
780 // the end of it. It is more efficient to uncommit from the end, so that applications
781 // could enjoy the near committed regions. GC allocations are much less frequent,
782 // and therefore can accept the committing costs.
783
784 size_t count = 0;
785 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
786 ShenandoahHeapRegion* r = get_region(i - 1);
787 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
788 ShenandoahHeapLocker locker(lock());
789 if (r->is_empty_committed()) {
790 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
791 break;
792 }
793
794 r->make_uncommitted();
795 count++;
796 }
797 }
798 SpinPause(); // allow allocators to take the lock
799 }
800
801 if (count > 0) {
802 notify_heap_changed();
803 }
804 }
805
806 bool ShenandoahHeap::check_soft_max_changed() {
807 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
808 size_t old_soft_max = soft_max_capacity();
809 if (new_soft_max != old_soft_max) {
810 new_soft_max = MAX2(min_capacity(), new_soft_max);
811 new_soft_max = MIN2(max_capacity(), new_soft_max);
812 if (new_soft_max != old_soft_max) {
813 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
814 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
815 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
816 );
817 set_soft_max_capacity(new_soft_max);
818 return true;
819 }
820 }
821 return false;
822 }
823
824 void ShenandoahHeap::notify_heap_changed() {
825 // Update monitoring counters when we took a new region. This amortizes the
826 // update costs on slow path.
827 monitoring_support()->notify_heap_changed();
828
829 // This is called from allocation path, and thus should be fast.
830 _heap_changed.try_set();
831 }
832
833 void ShenandoahHeap::set_forced_counters_update(bool value) {
834 monitoring_support()->set_forced_counters_update(value);
835 }
836
837 void ShenandoahHeap::handle_force_counters_update() {
838 monitoring_support()->handle_force_counters_update();
839 }
840
841 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
842 // New object should fit the GCLAB size
843 size_t min_size = MAX2(size, PLAB::min_size());
844
845 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
846 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
847 new_size = MIN2(new_size, PLAB::max_size());
848 new_size = MAX2(new_size, PLAB::min_size());
849
850 // Record new heuristic value even if we take any shortcut. This captures
851 // the case when moderately-sized objects always take a shortcut. At some point,
852 // heuristics should catch up with them.
853 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
854
855 if (new_size < size) {
856 // New size still does not fit the object. Fall back to shared allocation.
857 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
858 return nullptr;
859 }
860
861 // Retire current GCLAB, and allocate a new one.
862 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
863 gclab->retire();
864
865 size_t actual_size = 0;
866 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
867 if (gclab_buf == nullptr) {
868 return nullptr;
869 }
870
871 assert (size <= actual_size, "allocation should fit");
872
873 // ...and clear or zap just allocated TLAB, if needed.
874 if (ZeroTLAB) {
875 Copy::zero_to_words(gclab_buf, actual_size);
876 } else if (ZapTLAB) {
877 // Skip mangling the space corresponding to the object header to
878 // ensure that the returned space is not considered parsable by
879 // any concurrent GC thread.
880 size_t hdr_size = oopDesc::header_size();
881 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
882 }
883 gclab->set_buf(gclab_buf, actual_size);
884 return gclab->allocate(size);
885 }
886
887 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
888 size_t requested_size,
889 size_t* actual_size) {
890 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
891 HeapWord* res = allocate_memory(req);
892 if (res != nullptr) {
893 *actual_size = req.actual_size();
894 } else {
895 *actual_size = 0;
896 }
897 return res;
898 }
899
900 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
901 size_t word_size,
902 size_t* actual_size) {
903 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
904 HeapWord* res = allocate_memory(req);
905 if (res != nullptr) {
906 *actual_size = req.actual_size();
907 } else {
908 *actual_size = 0;
909 }
910 return res;
911 }
912
913 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
914 intptr_t pacer_epoch = 0;
915 bool in_new_region = false;
916 HeapWord* result = nullptr;
917
918 if (req.is_mutator_alloc()) {
919 if (ShenandoahPacing) {
920 pacer()->pace_for_alloc(req.size());
921 pacer_epoch = pacer()->epoch();
922 }
923
924 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
925 result = allocate_memory_under_lock(req, in_new_region);
926 }
927
928 // Check that gc overhead is not exceeded.
929 //
930 // Shenandoah will grind along for quite a while allocating one
931 // object at a time using shared (non-tlab) allocations. This check
932 // is testing that the GC overhead limit has not been exceeded.
933 // This will notify the collector to start a cycle, but will raise
934 // an OOME to the mutator if the last Full GCs have not made progress.
935 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
936 control_thread()->handle_alloc_failure(req, false);
937 return nullptr;
938 }
939
940 if (result == nullptr) {
941 // Block until control thread reacted, then retry allocation.
942 //
943 // It might happen that one of the threads requesting allocation would unblock
944 // way later after GC happened, only to fail the second allocation, because
945 // other threads have already depleted the free storage. In this case, a better
946 // strategy is to try again, until at least one full GC has completed.
947 //
948 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
949 // a) We experienced a GC that had good progress, or
950 // b) We experienced at least one Full GC (whether or not it had good progress)
951 //
952 // TODO: Consider GLOBAL GC rather than Full GC to remediate OOM condition: https://bugs.openjdk.org/browse/JDK-8335910
953
954 size_t original_count = shenandoah_policy()->full_gc_count();
955 while ((result == nullptr) && (original_count == shenandoah_policy()->full_gc_count())) {
956 control_thread()->handle_alloc_failure(req, true);
957 result = allocate_memory_under_lock(req, in_new_region);
958 }
959 if (result != nullptr) {
960 // If our allocation request has been satisifed after it initially failed, we count this as good gc progress
961 notify_gc_progress();
962 }
963 if (log_is_enabled(Debug, gc, alloc)) {
964 ResourceMark rm;
965 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: " SIZE_FORMAT
966 ", Original: " SIZE_FORMAT ", Latest: " SIZE_FORMAT,
967 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
968 original_count, get_gc_no_progress_count());
969 }
970 }
971 } else {
972 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
973 result = allocate_memory_under_lock(req, in_new_region);
974 // Do not call handle_alloc_failure() here, because we cannot block.
975 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
976 }
977
978 if (in_new_region) {
979 notify_heap_changed();
980 }
981
982 if (result != nullptr) {
983 size_t requested = req.size();
984 size_t actual = req.actual_size();
985
986 assert (req.is_lab_alloc() || (requested == actual),
987 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
988 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
989
990 if (req.is_mutator_alloc()) {
991 notify_mutator_alloc_words(actual, false);
992
993 // If we requested more than we were granted, give the rest back to pacer.
994 // This only matters if we are in the same pacing epoch: do not try to unpace
995 // over the budget for the other phase.
996 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
997 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
998 }
999 } else {
1000 increase_used(actual*HeapWordSize);
1001 }
1002 }
1003
1004 return result;
1005 }
1006
1007 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1008 // If we are dealing with mutator allocation, then we may need to block for safepoint.
1009 // We cannot block for safepoint for GC allocations, because there is a high chance
1010 // we are already running at safepoint or from stack watermark machinery, and we cannot
1011 // block again.
1012 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1013 return _free_set->allocate(req, in_new_region);
1014 }
1015
1016 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1017 bool* gc_overhead_limit_was_exceeded) {
1018 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1019 return allocate_memory(req);
1020 }
1021
1022 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1023 size_t size,
1024 Metaspace::MetadataType mdtype) {
1025 MetaWord* result;
1026
1027 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1028 if (heuristics()->can_unload_classes()) {
1029 ShenandoahHeuristics* h = heuristics();
1030 h->record_metaspace_oom();
1031 }
1032
1033 // Expand and retry allocation
1034 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1035 if (result != nullptr) {
1036 return result;
1037 }
1038
1039 // Start full GC
1040 collect(GCCause::_metadata_GC_clear_soft_refs);
1041
1042 // Retry allocation
1043 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1044 if (result != nullptr) {
1045 return result;
1046 }
1047
1048 // Expand and retry allocation
1049 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1050 if (result != nullptr) {
1051 return result;
1052 }
1053
1054 // Out of memory
1055 return nullptr;
1056 }
1057
1058 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1059 private:
1060 ShenandoahHeap* const _heap;
1061 Thread* const _thread;
1062 public:
1063 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1064 _heap(heap), _thread(Thread::current()) {}
1065
1066 void do_object(oop p) {
1067 shenandoah_assert_marked(nullptr, p);
1068 if (!p->is_forwarded()) {
1069 _heap->evacuate_object(p, _thread);
1070 }
1071 }
1072 };
1073
1074 class ShenandoahEvacuationTask : public WorkerTask {
1075 private:
1076 ShenandoahHeap* const _sh;
1077 ShenandoahCollectionSet* const _cs;
1078 bool _concurrent;
1079 public:
1080 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1081 ShenandoahCollectionSet* cs,
1082 bool concurrent) :
1083 WorkerTask("Shenandoah Evacuation"),
1084 _sh(sh),
1085 _cs(cs),
1086 _concurrent(concurrent)
1087 {}
1088
1089 void work(uint worker_id) {
1090 if (_concurrent) {
1091 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1092 ShenandoahSuspendibleThreadSetJoiner stsj;
1093 ShenandoahEvacOOMScope oom_evac_scope;
1094 do_work();
1095 } else {
1096 ShenandoahParallelWorkerSession worker_session(worker_id);
1097 ShenandoahEvacOOMScope oom_evac_scope;
1098 do_work();
1099 }
1100 }
1101
1102 private:
1103 void do_work() {
1104 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1105 ShenandoahHeapRegion* r;
1106 while ((r =_cs->claim_next()) != nullptr) {
1107 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1108 _sh->marked_object_iterate(r, &cl);
1109
1110 if (ShenandoahPacing) {
1111 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1112 }
1113
1114 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1115 break;
1116 }
1117 }
1118 }
1119 };
1120
1121 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1122 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1123 workers()->run_task(&task);
1124 }
1125
1126 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1127 if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
1128 // This thread went through the OOM during evac protocol and it is safe to return
1129 // the forward pointer. It must not attempt to evacuate any more.
1130 return ShenandoahBarrierSet::resolve_forwarded(p);
1131 }
1132
1133 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1134
1135 size_t size = ShenandoahForwarding::size(p);
1136
1137 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
1138
1139 bool alloc_from_gclab = true;
1140 HeapWord* copy = nullptr;
1141
1142 #ifdef ASSERT
1143 if (ShenandoahOOMDuringEvacALot &&
1144 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1145 copy = nullptr;
1146 } else {
1147 #endif
1148 if (UseTLAB) {
1149 copy = allocate_from_gclab(thread, size);
1150 }
1151 if (copy == nullptr) {
1152 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
1153 copy = allocate_memory(req);
1154 alloc_from_gclab = false;
1155 }
1156 #ifdef ASSERT
1157 }
1158 #endif
1159
1160 if (copy == nullptr) {
1161 control_thread()->handle_alloc_failure_evac(size);
1162
1163 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1164
1165 return ShenandoahBarrierSet::resolve_forwarded(p);
1166 }
1167
1168 // Copy the object:
1169 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1170
1171 // Try to install the new forwarding pointer.
1172 oop copy_val = cast_to_oop(copy);
1173 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1174 if (result == copy_val) {
1175 // Successfully evacuated. Our copy is now the public one!
1176 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1177 shenandoah_assert_correct(nullptr, copy_val);
1178 return copy_val;
1179 } else {
1180 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1181 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1182 // But if it happens to contain references to evacuated regions, those references would
1183 // not get updated for this stale copy during this cycle, and we will crash while scanning
1184 // it the next cycle.
1185 //
1186 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
1187 // object will overwrite this stale copy, or the filler object on LAB retirement will
1188 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
1189 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1190 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1191 if (alloc_from_gclab) {
1192 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1193 } else {
1194 fill_with_object(copy, size);
1195 shenandoah_assert_correct(nullptr, copy_val);
1196 }
1197 shenandoah_assert_correct(nullptr, result);
1198 return result;
1199 }
1200 }
1201
1202 void ShenandoahHeap::trash_cset_regions() {
1203 ShenandoahHeapLocker locker(lock());
1204
1205 ShenandoahCollectionSet* set = collection_set();
1206 ShenandoahHeapRegion* r;
1207 set->clear_current_index();
1208 while ((r = set->next()) != nullptr) {
1209 r->make_trash();
1210 }
1211 collection_set()->clear();
1212 }
1213
1214 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1215 st->print_cr("Heap Regions:");
1216 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1217 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1218 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1219 st->print_cr("UWM=update watermark, U=used");
1220 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1221 st->print_cr("S=shared allocs, L=live data");
1222 st->print_cr("CP=critical pins");
1223
1224 for (size_t i = 0; i < num_regions(); i++) {
1225 get_region(i)->print_on(st);
1226 }
1227 }
1228
1229 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1230 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1231
1232 oop humongous_obj = cast_to_oop(start->bottom());
1233 size_t size = humongous_obj->size();
1234 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1235 size_t index = start->index() + required_regions - 1;
1236
1237 assert(!start->has_live(), "liveness must be zero");
1238
1239 for(size_t i = 0; i < required_regions; i++) {
1240 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1241 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1242 ShenandoahHeapRegion* region = get_region(index --);
1243
1244 assert(region->is_humongous(), "expect correct humongous start or continuation");
1245 assert(!region->is_cset(), "Humongous region should not be in collection set");
1246
1247 region->make_trash_immediate();
1248 }
1249 }
1250
1251 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1252 public:
1253 ShenandoahCheckCleanGCLABClosure() {}
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 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1258 }
1259 };
1260
1261 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1262 private:
1263 bool const _resize;
1264 public:
1265 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1266 void do_thread(Thread* thread) {
1267 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1268 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1269 gclab->retire();
1270 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1271 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1272 }
1273 }
1274 };
1275
1276 void ShenandoahHeap::labs_make_parsable() {
1277 assert(UseTLAB, "Only call with UseTLAB");
1278
1279 ShenandoahRetireGCLABClosure cl(false);
1280
1281 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1282 ThreadLocalAllocBuffer& tlab = t->tlab();
1283 tlab.make_parsable();
1284 cl.do_thread(t);
1285 }
1286
1287 workers()->threads_do(&cl);
1288 }
1289
1290 void ShenandoahHeap::tlabs_retire(bool resize) {
1291 assert(UseTLAB, "Only call with UseTLAB");
1292 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1293
1294 ThreadLocalAllocStats stats;
1295
1296 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1297 ThreadLocalAllocBuffer& tlab = t->tlab();
1298 tlab.retire(&stats);
1299 if (resize) {
1300 tlab.resize();
1301 }
1302 }
1303
1304 stats.publish();
1305
1306 #ifdef ASSERT
1307 ShenandoahCheckCleanGCLABClosure cl;
1308 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1309 cl.do_thread(t);
1310 }
1311 workers()->threads_do(&cl);
1312 #endif
1313 }
1314
1315 void ShenandoahHeap::gclabs_retire(bool resize) {
1316 assert(UseTLAB, "Only call with UseTLAB");
1317 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1318
1319 ShenandoahRetireGCLABClosure cl(resize);
1320 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1321 cl.do_thread(t);
1322 }
1323 workers()->threads_do(&cl);
1324
1325 if (safepoint_workers() != nullptr) {
1326 safepoint_workers()->threads_do(&cl);
1327 }
1328 }
1329
1330 // Returns size in bytes
1331 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1332 // Return the max allowed size, and let the allocation path
1333 // figure out the safe size for current allocation.
1334 return ShenandoahHeapRegion::max_tlab_size_bytes();
1335 }
1336
1337 size_t ShenandoahHeap::max_tlab_size() const {
1338 // Returns size in words
1339 return ShenandoahHeapRegion::max_tlab_size_words();
1340 }
1341
1342 void ShenandoahHeap::collect(GCCause::Cause cause) {
1343 control_thread()->request_gc(cause);
1344 }
1345
1346 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1347 //assert(false, "Shouldn't need to do full collections");
1348 }
1349
1350 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1351 ShenandoahHeapRegion* r = heap_region_containing(addr);
1352 if (r != nullptr) {
1353 return r->block_start(addr);
1354 }
1355 return nullptr;
1356 }
1357
1358 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1359 ShenandoahHeapRegion* r = heap_region_containing(addr);
1360 return r->block_is_obj(addr);
1361 }
1362
1363 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1364 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1365 }
1366
1367 void ShenandoahHeap::prepare_for_verify() {
1368 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1369 labs_make_parsable();
1370 }
1371 }
1372
1373 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1374 if (_shenandoah_policy->is_at_shutdown()) {
1375 return;
1376 }
1377
1378 if (_control_thread != nullptr) {
1379 tcl->do_thread(_control_thread);
1380 }
1381
1382 workers()->threads_do(tcl);
1383 if (_safepoint_workers != nullptr) {
1384 _safepoint_workers->threads_do(tcl);
1385 }
1386 }
1387
1388 void ShenandoahHeap::print_tracing_info() const {
1389 LogTarget(Info, gc, stats) lt;
1390 if (lt.is_enabled()) {
1391 ResourceMark rm;
1392 LogStream ls(lt);
1393
1394 phase_timings()->print_global_on(&ls);
1395
1396 ls.cr();
1397 ls.cr();
1398
1399 shenandoah_policy()->print_gc_stats(&ls);
1400
1401 ls.cr();
1402 ls.cr();
1403 }
1404 }
1405
1406 void ShenandoahHeap::verify(VerifyOption vo) {
1407 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1408 if (ShenandoahVerify) {
1409 verifier()->verify_generic(vo);
1410 } else {
1411 // TODO: Consider allocating verification bitmaps on demand,
1412 // and turn this on unconditionally.
1413 }
1414 }
1415 }
1416 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1417 return _free_set->capacity();
1418 }
1419
1420 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1421 private:
1422 MarkBitMap* _bitmap;
1423 ShenandoahScanObjectStack* _oop_stack;
1424 ShenandoahHeap* const _heap;
1425 ShenandoahMarkingContext* const _marking_context;
1426
1427 template <class T>
1428 void do_oop_work(T* p) {
1429 T o = RawAccess<>::oop_load(p);
1430 if (!CompressedOops::is_null(o)) {
1431 oop obj = CompressedOops::decode_not_null(o);
1432 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1433 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1434 return;
1435 }
1436 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1437
1438 assert(oopDesc::is_oop(obj), "must be a valid oop");
1439 if (!_bitmap->is_marked(obj)) {
1440 _bitmap->mark(obj);
1441 _oop_stack->push(obj);
1442 }
1443 }
1444 }
1445 public:
1446 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1447 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1448 _marking_context(_heap->marking_context()) {}
1449 void do_oop(oop* p) { do_oop_work(p); }
1450 void do_oop(narrowOop* p) { do_oop_work(p); }
1451 };
1452
1453 /*
1454 * This is public API, used in preparation of object_iterate().
1455 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1456 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1457 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1458 */
1459 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1460 // No-op.
1461 }
1462
1463 /*
1464 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1465 *
1466 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1467 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1468 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1469 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1470 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1471 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1472 * wiped the bitmap in preparation for next marking).
1473 *
1474 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1475 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1476 * is allowed to report dead objects, but is not required to do so.
1477 */
1478 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1479 // Reset bitmap
1480 if (!prepare_aux_bitmap_for_iteration())
1481 return;
1482
1483 ShenandoahScanObjectStack oop_stack;
1484 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1485 // Seed the stack with root scan
1486 scan_roots_for_iteration(&oop_stack, &oops);
1487
1488 // Work through the oop stack to traverse heap
1489 while (! oop_stack.is_empty()) {
1490 oop obj = oop_stack.pop();
1491 assert(oopDesc::is_oop(obj), "must be a valid oop");
1492 cl->do_object(obj);
1493 obj->oop_iterate(&oops);
1494 }
1495
1496 assert(oop_stack.is_empty(), "should be empty");
1497 // Reclaim bitmap
1498 reclaim_aux_bitmap_for_iteration();
1499 }
1500
1501 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1502 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1503
1504 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1505 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1506 return false;
1507 }
1508 // Reset bitmap
1509 _aux_bit_map.clear();
1510 return true;
1511 }
1512
1513 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1514 // Process GC roots according to current GC cycle
1515 // This populates the work stack with initial objects
1516 // It is important to relinquish the associated locks before diving
1517 // into heap dumper
1518 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1519 ShenandoahHeapIterationRootScanner rp(n_workers);
1520 rp.roots_do(oops);
1521 }
1522
1523 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1524 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1525 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1526 }
1527 }
1528
1529 // Closure for parallelly iterate objects
1530 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1531 private:
1532 MarkBitMap* _bitmap;
1533 ShenandoahObjToScanQueue* _queue;
1534 ShenandoahHeap* const _heap;
1535 ShenandoahMarkingContext* const _marking_context;
1536
1537 template <class T>
1538 void do_oop_work(T* p) {
1539 T o = RawAccess<>::oop_load(p);
1540 if (!CompressedOops::is_null(o)) {
1541 oop obj = CompressedOops::decode_not_null(o);
1542 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1543 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1544 return;
1545 }
1546 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1547
1548 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1549 if (_bitmap->par_mark(obj)) {
1550 _queue->push(ShenandoahMarkTask(obj));
1551 }
1552 }
1553 }
1554 public:
1555 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1556 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1557 _marking_context(_heap->marking_context()) {}
1558 void do_oop(oop* p) { do_oop_work(p); }
1559 void do_oop(narrowOop* p) { do_oop_work(p); }
1560 };
1561
1562 // Object iterator for parallel heap iteraion.
1563 // The root scanning phase happenes in construction as a preparation of
1564 // parallel marking queues.
1565 // Every worker processes it's own marking queue. work-stealing is used
1566 // to balance workload.
1567 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1568 private:
1569 uint _num_workers;
1570 bool _init_ready;
1571 MarkBitMap* _aux_bit_map;
1572 ShenandoahHeap* _heap;
1573 ShenandoahScanObjectStack _roots_stack; // global roots stack
1574 ShenandoahObjToScanQueueSet* _task_queues;
1575 public:
1576 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1577 _num_workers(num_workers),
1578 _init_ready(false),
1579 _aux_bit_map(bitmap),
1580 _heap(ShenandoahHeap::heap()) {
1581 // Initialize bitmap
1582 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1583 if (!_init_ready) {
1584 return;
1585 }
1586
1587 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1588 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1589
1590 _init_ready = prepare_worker_queues();
1591 }
1592
1593 ~ShenandoahParallelObjectIterator() {
1594 // Reclaim bitmap
1595 _heap->reclaim_aux_bitmap_for_iteration();
1596 // Reclaim queue for workers
1597 if (_task_queues!= nullptr) {
1598 for (uint i = 0; i < _num_workers; ++i) {
1599 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1600 if (q != nullptr) {
1601 delete q;
1602 _task_queues->register_queue(i, nullptr);
1603 }
1604 }
1605 delete _task_queues;
1606 _task_queues = nullptr;
1607 }
1608 }
1609
1610 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1611 if (_init_ready) {
1612 object_iterate_parallel(cl, worker_id, _task_queues);
1613 }
1614 }
1615
1616 private:
1617 // Divide global root_stack into worker queues
1618 bool prepare_worker_queues() {
1619 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1620 // Initialize queues for every workers
1621 for (uint i = 0; i < _num_workers; ++i) {
1622 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1623 _task_queues->register_queue(i, task_queue);
1624 }
1625 // Divide roots among the workers. Assume that object referencing distribution
1626 // is related with root kind, use round-robin to make every worker have same chance
1627 // to process every kind of roots
1628 size_t roots_num = _roots_stack.size();
1629 if (roots_num == 0) {
1630 // No work to do
1631 return false;
1632 }
1633
1634 for (uint j = 0; j < roots_num; j++) {
1635 uint stack_id = j % _num_workers;
1636 oop obj = _roots_stack.pop();
1637 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1638 }
1639 return true;
1640 }
1641
1642 void object_iterate_parallel(ObjectClosure* cl,
1643 uint worker_id,
1644 ShenandoahObjToScanQueueSet* queue_set) {
1645 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1646 assert(queue_set != nullptr, "task queue must not be null");
1647
1648 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1649 assert(q != nullptr, "object iterate queue must not be null");
1650
1651 ShenandoahMarkTask t;
1652 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1653
1654 // Work through the queue to traverse heap.
1655 // Steal when there is no task in queue.
1656 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1657 oop obj = t.obj();
1658 assert(oopDesc::is_oop(obj), "must be a valid oop");
1659 cl->do_object(obj);
1660 obj->oop_iterate(&oops);
1661 }
1662 assert(q->is_empty(), "should be empty");
1663 }
1664 };
1665
1666 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1667 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1668 }
1669
1670 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1671 void ShenandoahHeap::keep_alive(oop obj) {
1672 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1673 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1674 }
1675 }
1676
1677 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1678 for (size_t i = 0; i < num_regions(); i++) {
1679 ShenandoahHeapRegion* current = get_region(i);
1680 blk->heap_region_do(current);
1681 }
1682 }
1683
1684 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1685 private:
1686 ShenandoahHeap* const _heap;
1687 ShenandoahHeapRegionClosure* const _blk;
1688 size_t const _stride;
1689
1690 shenandoah_padding(0);
1691 volatile size_t _index;
1692 shenandoah_padding(1);
1693
1694 public:
1695 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
1696 WorkerTask("Shenandoah Parallel Region Operation"),
1697 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
1698
1699 void work(uint worker_id) {
1700 ShenandoahParallelWorkerSession worker_session(worker_id);
1701 size_t stride = _stride;
1702
1703 size_t max = _heap->num_regions();
1704 while (Atomic::load(&_index) < max) {
1705 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1706 size_t start = cur;
1707 size_t end = MIN2(cur + stride, max);
1708 if (start >= max) break;
1709
1710 for (size_t i = cur; i < end; i++) {
1711 ShenandoahHeapRegion* current = _heap->get_region(i);
1712 _blk->heap_region_do(current);
1713 }
1714 }
1715 }
1716 };
1717
1718 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1719 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1720 const uint active_workers = workers()->active_workers();
1721 const size_t n_regions = num_regions();
1722 size_t stride = ShenandoahParallelRegionStride;
1723 if (stride == 0 && active_workers > 1) {
1724 // Automatically derive the stride to balance the work between threads
1725 // evenly. Do not try to split work if below the reasonable threshold.
1726 constexpr size_t threshold = 4096;
1727 stride = n_regions <= threshold ?
1728 threshold :
1729 (n_regions + active_workers - 1) / active_workers;
1730 }
1731
1732 if (n_regions > stride && active_workers > 1) {
1733 ShenandoahParallelHeapRegionTask task(blk, stride);
1734 workers()->run_task(&task);
1735 } else {
1736 heap_region_iterate(blk);
1737 }
1738 }
1739
1740 class ShenandoahRendezvousClosure : public HandshakeClosure {
1741 public:
1742 inline ShenandoahRendezvousClosure(const char* name) : HandshakeClosure(name) {}
1743 inline void do_thread(Thread* thread) {}
1744 };
1745
1746 void ShenandoahHeap::rendezvous_threads(const char* name) {
1747 ShenandoahRendezvousClosure cl(name);
1748 Handshake::execute(&cl);
1749 }
1750
1751 void ShenandoahHeap::recycle_trash() {
1752 free_set()->recycle_trash();
1753 }
1754
1755 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1756 private:
1757 ShenandoahMarkingContext* const _ctx;
1758 public:
1759 ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1760
1761 void heap_region_do(ShenandoahHeapRegion* r) {
1762 if (r->is_active()) {
1763 // Reset live data and set TAMS optimistically. We would recheck these under the pause
1764 // anyway to capture any updates that happened since now.
1765 r->clear_live_data();
1766 _ctx->capture_top_at_mark_start(r);
1767 }
1768 }
1769
1770 bool is_thread_safe() { return true; }
1771 };
1772
1773 void ShenandoahHeap::prepare_gc() {
1774 reset_mark_bitmap();
1775
1776 ShenandoahResetUpdateRegionStateClosure cl;
1777 parallel_heap_region_iterate(&cl);
1778 }
1779
1780 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1781 private:
1782 ShenandoahMarkingContext* const _ctx;
1783 ShenandoahHeapLock* const _lock;
1784
1785 public:
1786 ShenandoahFinalMarkUpdateRegionStateClosure() :
1787 _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1788
1789 void heap_region_do(ShenandoahHeapRegion* r) {
1790 if (r->is_active()) {
1791 // All allocations past TAMS are implicitly live, adjust the region data.
1792 // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1793 HeapWord *tams = _ctx->top_at_mark_start(r);
1794 HeapWord *top = r->top();
1795 if (top > tams) {
1796 r->increase_live_data_alloc_words(pointer_delta(top, tams));
1797 }
1798
1799 // We are about to select the collection set, make sure it knows about
1800 // current pinning status. Also, this allows trashing more regions that
1801 // now have their pinning status dropped.
1802 if (r->is_pinned()) {
1803 if (r->pin_count() == 0) {
1804 ShenandoahHeapLocker locker(_lock);
1805 r->make_unpinned();
1806 }
1807 } else {
1808 if (r->pin_count() > 0) {
1809 ShenandoahHeapLocker locker(_lock);
1810 r->make_pinned();
1811 }
1812 }
1813
1814 // Remember limit for updating refs. It's guaranteed that we get no
1815 // from-space-refs written from here on.
1816 r->set_update_watermark_at_safepoint(r->top());
1817 } else {
1818 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1819 assert(_ctx->top_at_mark_start(r) == r->top(),
1820 "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1821 }
1822 }
1823
1824 bool is_thread_safe() { return true; }
1825 };
1826
1827 void ShenandoahHeap::prepare_regions_and_collection_set(bool concurrent) {
1828 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
1829 {
1830 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states :
1831 ShenandoahPhaseTimings::degen_gc_final_update_region_states);
1832 ShenandoahFinalMarkUpdateRegionStateClosure cl;
1833 parallel_heap_region_iterate(&cl);
1834
1835 assert_pinned_region_status();
1836 }
1837
1838 {
1839 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset :
1840 ShenandoahPhaseTimings::degen_gc_choose_cset);
1841 ShenandoahHeapLocker locker(lock());
1842 _collection_set->clear();
1843 heuristics()->choose_collection_set(_collection_set);
1844 }
1845
1846 {
1847 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset :
1848 ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
1849 ShenandoahHeapLocker locker(lock());
1850 _free_set->rebuild();
1851 }
1852 }
1853
1854 void ShenandoahHeap::do_class_unloading() {
1855 _unloader.unload();
1856 }
1857
1858 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1859 // Weak refs processing
1860 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1861 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1862 ShenandoahTimingsTracker t(phase);
1863 ShenandoahGCWorkerPhase worker_phase(phase);
1864 ref_processor()->process_references(phase, workers(), false /* concurrent */);
1865 }
1866
1867 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1868 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1869
1870 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1871 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1872 // for future GCLABs here.
1873 if (UseTLAB) {
1874 ShenandoahGCPhase phase(concurrent ?
1875 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1876 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1877 gclabs_retire(ResizeTLAB);
1878 }
1879
1880 _update_refs_iterator.reset();
1881 }
1882
1883 void ShenandoahHeap::propagate_gc_state_to_java_threads() {
1884 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1885 if (_gc_state_changed) {
1886 _gc_state_changed = false;
1887 char state = gc_state();
1888 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1889 ShenandoahThreadLocalData::set_gc_state(t, state);
1890 }
1891 }
1892 }
1893
1894 void ShenandoahHeap::set_gc_state(uint mask, bool value) {
1895 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1896 _gc_state.set_cond(mask, value);
1897 _gc_state_changed = true;
1898 }
1899
1900 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1901 assert(!has_forwarded_objects(), "Not expected before/after mark phase");
1902 set_gc_state(MARKING, in_progress);
1903 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1904 }
1905
1906 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1907 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1908 set_gc_state(EVACUATION, in_progress);
1909 }
1910
1911 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
1912 if (in_progress) {
1913 _concurrent_strong_root_in_progress.set();
1914 } else {
1915 _concurrent_strong_root_in_progress.unset();
1916 }
1917 }
1918
1919 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
1920 set_gc_state(WEAK_ROOTS, cond);
1921 }
1922
1923 GCTracer* ShenandoahHeap::tracer() {
1924 return shenandoah_policy()->tracer();
1925 }
1926
1927 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1928 return _free_set->used();
1929 }
1930
1931 bool ShenandoahHeap::try_cancel_gc() {
1932 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1933 return prev == CANCELLABLE;
1934 }
1935
1936 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1937 if (try_cancel_gc()) {
1938 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1939 log_info(gc)("%s", msg.buffer());
1940 Events::log(Thread::current(), "%s", msg.buffer());
1941 }
1942 }
1943
1944 uint ShenandoahHeap::max_workers() {
1945 return _max_workers;
1946 }
1947
1948 void ShenandoahHeap::stop() {
1949 // The shutdown sequence should be able to terminate when GC is running.
1950
1951 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
1952 _shenandoah_policy->record_shutdown();
1953
1954 // Step 1. Notify control thread that we are in shutdown.
1955 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1956 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1957 control_thread()->prepare_for_graceful_shutdown();
1958
1959 // Step 2. Notify GC workers that we are cancelling GC.
1960 cancel_gc(GCCause::_shenandoah_stop_vm);
1961
1962 // Step 3. Wait until GC worker exits normally.
1963 control_thread()->stop();
1964 }
1965
1966 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1967 if (!unload_classes()) return;
1968 ClassUnloadingContext ctx(_workers->active_workers(),
1969 true /* unregister_nmethods_during_purge */,
1970 false /* lock_nmethod_free_separately */);
1971
1972 // Unload classes and purge SystemDictionary.
1973 {
1974 ShenandoahPhaseTimings::Phase phase = full_gc ?
1975 ShenandoahPhaseTimings::full_gc_purge_class_unload :
1976 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
1977 ShenandoahIsAliveSelector is_alive;
1978 {
1979 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
1980 ShenandoahGCPhase gc_phase(phase);
1981 ShenandoahGCWorkerPhase worker_phase(phase);
1982 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
1983
1984 uint num_workers = _workers->active_workers();
1985 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
1986 _workers->run_task(&unlink_task);
1987 }
1988 // Release unloaded nmethods's memory.
1989 ClassUnloadingContext::context()->purge_and_free_nmethods();
1990 }
1991
1992 {
1993 ShenandoahGCPhase phase(full_gc ?
1994 ShenandoahPhaseTimings::full_gc_purge_cldg :
1995 ShenandoahPhaseTimings::degen_gc_purge_cldg);
1996 ClassLoaderDataGraph::purge(true /* at_safepoint */);
1997 }
1998 // Resize and verify metaspace
1999 MetaspaceGC::compute_new_size();
2000 DEBUG_ONLY(MetaspaceUtils::verify();)
2001 }
2002
2003 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
2004 // so they should not have forwarded oops.
2005 // However, we do need to "null" dead oops in the roots, if can not be done
2006 // in concurrent cycles.
2007 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2008 uint num_workers = _workers->active_workers();
2009 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2010 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2011 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2012 ShenandoahGCPhase phase(timing_phase);
2013 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2014 // Cleanup weak roots
2015 if (has_forwarded_objects()) {
2016 ShenandoahForwardedIsAliveClosure is_alive;
2017 ShenandoahNonConcUpdateRefsClosure keep_alive;
2018 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure>
2019 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2020 _workers->run_task(&cleaning_task);
2021 } else {
2022 ShenandoahIsAliveClosure is_alive;
2023 #ifdef ASSERT
2024 ShenandoahAssertNotForwardedClosure verify_cl;
2025 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2026 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2027 #else
2028 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2029 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2030 #endif
2031 _workers->run_task(&cleaning_task);
2032 }
2033 }
2034
2035 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2036 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2037 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2038 ShenandoahGCPhase phase(full_gc ?
2039 ShenandoahPhaseTimings::full_gc_purge :
2040 ShenandoahPhaseTimings::degen_gc_purge);
2041 stw_weak_refs(full_gc);
2042 stw_process_weak_roots(full_gc);
2043 stw_unload_classes(full_gc);
2044 }
2045
2046 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2047 set_gc_state(HAS_FORWARDED, cond);
2048 }
2049
2050 void ShenandoahHeap::set_unload_classes(bool uc) {
2051 _unload_classes.set_cond(uc);
2052 }
2053
2054 bool ShenandoahHeap::unload_classes() const {
2055 return _unload_classes.is_set();
2056 }
2057
2058 address ShenandoahHeap::in_cset_fast_test_addr() {
2059 ShenandoahHeap* heap = ShenandoahHeap::heap();
2060 assert(heap->collection_set() != nullptr, "Sanity");
2061 return (address) heap->collection_set()->biased_map_address();
2062 }
2063
2064 size_t ShenandoahHeap::bytes_allocated_since_gc_start() const {
2065 return Atomic::load(&_bytes_allocated_since_gc_start);
2066 }
2067
2068 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2069 Atomic::store(&_bytes_allocated_since_gc_start, (size_t)0);
2070 }
2071
2072 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2073 _degenerated_gc_in_progress.set_cond(in_progress);
2074 }
2075
2076 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2077 _full_gc_in_progress.set_cond(in_progress);
2078 }
2079
2080 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2081 assert (is_full_gc_in_progress(), "should be");
2082 _full_gc_move_in_progress.set_cond(in_progress);
2083 }
2084
2085 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2086 set_gc_state(UPDATEREFS, in_progress);
2087 }
2088
2089 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2090 ShenandoahCodeRoots::register_nmethod(nm);
2091 }
2092
2093 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2094 ShenandoahCodeRoots::unregister_nmethod(nm);
2095 }
2096
2097 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2098 heap_region_containing(o)->record_pin();
2099 }
2100
2101 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2102 ShenandoahHeapRegion* r = heap_region_containing(o);
2103 assert(r != nullptr, "Sanity");
2104 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
2105 r->record_unpin();
2106 }
2107
2108 void ShenandoahHeap::sync_pinned_region_status() {
2109 ShenandoahHeapLocker locker(lock());
2110
2111 for (size_t i = 0; i < num_regions(); i++) {
2112 ShenandoahHeapRegion *r = get_region(i);
2113 if (r->is_active()) {
2114 if (r->is_pinned()) {
2115 if (r->pin_count() == 0) {
2116 r->make_unpinned();
2117 }
2118 } else {
2119 if (r->pin_count() > 0) {
2120 r->make_pinned();
2121 }
2122 }
2123 }
2124 }
2125
2126 assert_pinned_region_status();
2127 }
2128
2129 #ifdef ASSERT
2130 void ShenandoahHeap::assert_pinned_region_status() {
2131 for (size_t i = 0; i < num_regions(); i++) {
2132 ShenandoahHeapRegion* r = get_region(i);
2133 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2134 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2135 }
2136 }
2137 #endif
2138
2139 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2140 return _gc_timer;
2141 }
2142
2143 void ShenandoahHeap::prepare_concurrent_roots() {
2144 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2145 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2146 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2147 set_concurrent_weak_root_in_progress(true);
2148 if (unload_classes()) {
2149 _unloader.prepare();
2150 }
2151 }
2152
2153 void ShenandoahHeap::finish_concurrent_roots() {
2154 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2155 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2156 if (unload_classes()) {
2157 _unloader.finish();
2158 }
2159 }
2160
2161 #ifdef ASSERT
2162 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2163 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2164
2165 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2166 // Use ParallelGCThreads inside safepoints
2167 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2168 ParallelGCThreads, nworkers);
2169 } else {
2170 // Use ConcGCThreads outside safepoints
2171 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2172 ConcGCThreads, nworkers);
2173 }
2174 }
2175 #endif
2176
2177 ShenandoahVerifier* ShenandoahHeap::verifier() {
2178 guarantee(ShenandoahVerify, "Should be enabled");
2179 assert (_verifier != nullptr, "sanity");
2180 return _verifier;
2181 }
2182
2183 template<bool CONCURRENT>
2184 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2185 private:
2186 ShenandoahHeap* _heap;
2187 ShenandoahRegionIterator* _regions;
2188 public:
2189 ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2190 WorkerTask("Shenandoah Update References"),
2191 _heap(ShenandoahHeap::heap()),
2192 _regions(regions) {
2193 }
2194
2195 void work(uint worker_id) {
2196 if (CONCURRENT) {
2197 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2198 ShenandoahSuspendibleThreadSetJoiner stsj;
2199 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2200 } else {
2201 ShenandoahParallelWorkerSession worker_session(worker_id);
2202 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
2203 }
2204 }
2205
2206 private:
2207 template<class T>
2208 void do_work(uint worker_id) {
2209 T cl;
2210 if (CONCURRENT && (worker_id == 0)) {
2211 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2212 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2213 size_t cset_regions = _heap->collection_set()->count();
2214 // We cannot transfer any more regions than will be reclaimed when the existing collection set is recycled because
2215 // we need the reclaimed collection set regions to replenish the collector reserves
2216 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2217 }
2218 // If !CONCURRENT, there's no value in expanding Mutator free set
2219
2220 ShenandoahHeapRegion* r = _regions->next();
2221 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2222 while (r != nullptr) {
2223 HeapWord* update_watermark = r->get_update_watermark();
2224 assert (update_watermark >= r->bottom(), "sanity");
2225 if (r->is_active() && !r->is_cset()) {
2226 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2227 }
2228 if (ShenandoahPacing) {
2229 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2230 }
2231 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2232 return;
2233 }
2234 r = _regions->next();
2235 }
2236 }
2237 };
2238
2239 void ShenandoahHeap::update_heap_references(bool concurrent) {
2240 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2241
2242 if (concurrent) {
2243 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2244 workers()->run_task(&task);
2245 } else {
2246 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2247 workers()->run_task(&task);
2248 }
2249 }
2250
2251
2252 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2253 private:
2254 ShenandoahHeapLock* const _lock;
2255
2256 public:
2257 ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2258
2259 void heap_region_do(ShenandoahHeapRegion* r) {
2260 // Drop unnecessary "pinned" state from regions that does not have CP marks
2261 // anymore, as this would allow trashing them.
2262
2263 if (r->is_active()) {
2264 if (r->is_pinned()) {
2265 if (r->pin_count() == 0) {
2266 ShenandoahHeapLocker locker(_lock);
2267 r->make_unpinned();
2268 }
2269 } else {
2270 if (r->pin_count() > 0) {
2271 ShenandoahHeapLocker locker(_lock);
2272 r->make_pinned();
2273 }
2274 }
2275 }
2276 }
2277
2278 bool is_thread_safe() { return true; }
2279 };
2280
2281 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2282 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2283 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2284
2285 {
2286 ShenandoahGCPhase phase(concurrent ?
2287 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2288 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2289 ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2290 parallel_heap_region_iterate(&cl);
2291
2292 assert_pinned_region_status();
2293 }
2294
2295 {
2296 ShenandoahGCPhase phase(concurrent ?
2297 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2298 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2299 trash_cset_regions();
2300 }
2301 }
2302
2303 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2304 {
2305 ShenandoahGCPhase phase(concurrent ?
2306 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2307 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2308 ShenandoahHeapLocker locker(lock());
2309 _free_set->rebuild();
2310 }
2311 }
2312
2313 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2314 print_on(st);
2315 st->cr();
2316 print_heap_regions_on(st);
2317 }
2318
2319 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2320 size_t slice = r->index() / _bitmap_regions_per_slice;
2321
2322 size_t regions_from = _bitmap_regions_per_slice * slice;
2323 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2324 for (size_t g = regions_from; g < regions_to; g++) {
2325 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2326 if (skip_self && g == r->index()) continue;
2327 if (get_region(g)->is_committed()) {
2328 return true;
2329 }
2330 }
2331 return false;
2332 }
2333
2334 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2335 shenandoah_assert_heaplocked();
2336
2337 // Bitmaps in special regions do not need commits
2338 if (_bitmap_region_special) {
2339 return true;
2340 }
2341
2342 if (is_bitmap_slice_committed(r, true)) {
2343 // Some other region from the group is already committed, meaning the bitmap
2344 // slice is already committed, we exit right away.
2345 return true;
2346 }
2347
2348 // Commit the bitmap slice:
2349 size_t slice = r->index() / _bitmap_regions_per_slice;
2350 size_t off = _bitmap_bytes_per_slice * slice;
2351 size_t len = _bitmap_bytes_per_slice;
2352 char* start = (char*) _bitmap_region.start() + off;
2353
2354 if (!os::commit_memory(start, len, false)) {
2355 return false;
2356 }
2357
2358 if (AlwaysPreTouch) {
2359 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2360 }
2361
2362 return true;
2363 }
2364
2365 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2366 shenandoah_assert_heaplocked();
2367
2368 // Bitmaps in special regions do not need uncommits
2369 if (_bitmap_region_special) {
2370 return true;
2371 }
2372
2373 if (is_bitmap_slice_committed(r, true)) {
2374 // Some other region from the group is still committed, meaning the bitmap
2375 // slice is should stay committed, exit right away.
2376 return true;
2377 }
2378
2379 // Uncommit the bitmap slice:
2380 size_t slice = r->index() / _bitmap_regions_per_slice;
2381 size_t off = _bitmap_bytes_per_slice * slice;
2382 size_t len = _bitmap_bytes_per_slice;
2383 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2384 return false;
2385 }
2386 return true;
2387 }
2388
2389 void ShenandoahHeap::safepoint_synchronize_begin() {
2390 StackWatermarkSet::safepoint_synchronize_begin();
2391 SuspendibleThreadSet::synchronize();
2392 }
2393
2394 void ShenandoahHeap::safepoint_synchronize_end() {
2395 SuspendibleThreadSet::desynchronize();
2396 }
2397
2398 void ShenandoahHeap::try_inject_alloc_failure() {
2399 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2400 _inject_alloc_failure.set();
2401 os::naked_short_sleep(1);
2402 if (cancelled_gc()) {
2403 log_info(gc)("Allocation failure was successfully injected");
2404 }
2405 }
2406 }
2407
2408 bool ShenandoahHeap::should_inject_alloc_failure() {
2409 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2410 }
2411
2412 void ShenandoahHeap::initialize_serviceability() {
2413 _memory_pool = new ShenandoahMemoryPool(this);
2414 _cycle_memory_manager.add_pool(_memory_pool);
2415 _stw_memory_manager.add_pool(_memory_pool);
2416 }
2417
2418 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2419 GrowableArray<GCMemoryManager*> memory_managers(2);
2420 memory_managers.append(&_cycle_memory_manager);
2421 memory_managers.append(&_stw_memory_manager);
2422 return memory_managers;
2423 }
2424
2425 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2426 GrowableArray<MemoryPool*> memory_pools(1);
2427 memory_pools.append(_memory_pool);
2428 return memory_pools;
2429 }
2430
2431 MemoryUsage ShenandoahHeap::memory_usage() {
2432 return _memory_pool->get_memory_usage();
2433 }
2434
2435 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2436 _heap(ShenandoahHeap::heap()),
2437 _index(0) {}
2438
2439 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2440 _heap(heap),
2441 _index(0) {}
2442
2443 void ShenandoahRegionIterator::reset() {
2444 _index = 0;
2445 }
2446
2447 bool ShenandoahRegionIterator::has_next() const {
2448 return _index < _heap->num_regions();
2449 }
2450
2451 char ShenandoahHeap::gc_state() const {
2452 return _gc_state.raw_value();
2453 }
2454
2455 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2456 #ifdef ASSERT
2457 assert(_liveness_cache != nullptr, "sanity");
2458 assert(worker_id < _max_workers, "sanity");
2459 for (uint i = 0; i < num_regions(); i++) {
2460 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2461 }
2462 #endif
2463 return _liveness_cache[worker_id];
2464 }
2465
2466 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2467 assert(worker_id < _max_workers, "sanity");
2468 assert(_liveness_cache != nullptr, "sanity");
2469 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2470 for (uint i = 0; i < num_regions(); i++) {
2471 ShenandoahLiveData live = ld[i];
2472 if (live > 0) {
2473 ShenandoahHeapRegion* r = get_region(i);
2474 r->increase_live_data_gc_words(live);
2475 ld[i] = 0;
2476 }
2477 }
2478 }
2479
2480 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2481 if (is_idle()) return false;
2482
2483 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2484 // marking phase.
2485 if (is_concurrent_mark_in_progress() &&
2486 !marking_context()->allocated_after_mark_start(obj)) {
2487 return true;
2488 }
2489
2490 // Can not guarantee obj is deeply good.
2491 if (has_forwarded_objects()) {
2492 return true;
2493 }
2494
2495 return false;
2496 }
2497
2498 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2499 #if INCLUDE_CDS_JAVA_HEAP
2500 // CDS wants a continuous memory range to load a bunch of objects.
2501 // This effectively bypasses normal allocation paths, and requires
2502 // a bit of massaging to unbreak GC invariants.
2503
2504 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
2505
2506 // Easy case: a single regular region, no further adjustments needed.
2507 if (!ShenandoahHeapRegion::requires_humongous(size)) {
2508 return allocate_memory(req);
2509 }
2510
2511 // Hard case: the requested size would cause a humongous allocation.
2512 // We need to make sure it looks like regular allocation to the rest of GC.
2513
2514 // CDS code would guarantee no objects straddle multiple regions, as long as
2515 // regions are as large as MIN_GC_REGION_ALIGNMENT. It is impractical at this
2516 // point to deal with case when Shenandoah runs with smaller regions.
2517 // TODO: This check can be dropped once MIN_GC_REGION_ALIGNMENT agrees more with Shenandoah.
2518 if (ShenandoahHeapRegion::region_size_bytes() < ArchiveHeapWriter::MIN_GC_REGION_ALIGNMENT) {
2519 return nullptr;
2520 }
2521
2522 HeapWord* mem = allocate_memory(req);
2523 size_t start_idx = heap_region_index_containing(mem);
2524 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
2525
2526 // Flip humongous -> regular.
2527 {
2528 ShenandoahHeapLocker locker(lock(), false);
2529 for (size_t c = start_idx; c < start_idx + num_regions; c++) {
2530 get_region(c)->make_regular_bypass();
2531 }
2532 }
2533
2534 return mem;
2535 #else
2536 assert(false, "Archive heap loader should not be available, should not be here");
2537 return nullptr;
2538 #endif // INCLUDE_CDS_JAVA_HEAP
2539 }
2540
2541 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2542 // Nothing to do here, except checking that heap looks fine.
2543 #ifdef ASSERT
2544 HeapWord* start = archive_space.start();
2545 HeapWord* end = archive_space.end();
2546
2547 // No unclaimed space between the objects.
2548 // Objects are properly allocated in correct regions.
2549 HeapWord* cur = start;
2550 while (cur < end) {
2551 oop oop = cast_to_oop(cur);
2552 shenandoah_assert_in_correct_region(nullptr, oop);
2553 cur += oop->size();
2554 }
2555
2556 // No unclaimed tail at the end of archive space.
2557 assert(cur == end,
2558 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2559 p2i(cur), p2i(end));
2560
2561 // Region bounds are good.
2562 ShenandoahHeapRegion* begin_reg = heap_region_containing(start);
2563 ShenandoahHeapRegion* end_reg = heap_region_containing(end);
2564 assert(begin_reg->is_regular(), "Must be");
2565 assert(end_reg->is_regular(), "Must be");
2566 assert(begin_reg->bottom() == start,
2567 "Must agree: archive-space-start: " PTR_FORMAT ", begin-region-bottom: " PTR_FORMAT,
2568 p2i(start), p2i(begin_reg->bottom()));
2569 assert(end_reg->top() == end,
2570 "Must agree: archive-space-end: " PTR_FORMAT ", end-region-top: " PTR_FORMAT,
2571 p2i(end), p2i(end_reg->top()));
2572 #endif
2573 }