1 /*
2 * Copyright (c) 2023, 2024, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/universe.hpp"
29
30 #include "gc/shared/classUnloadingContext.hpp"
31 #include "gc/shared/gcArguments.hpp"
32 #include "gc/shared/gcTimer.hpp"
33 #include "gc/shared/gcTraceTime.inline.hpp"
34 #include "gc/shared/locationPrinter.inline.hpp"
35 #include "gc/shared/memAllocator.hpp"
36 #include "gc/shared/plab.hpp"
37 #include "gc/shared/slidingForwarding.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/shenandoahOopClosures.inline.hpp"
58 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
59 #include "gc/shenandoah/shenandoahPadding.hpp"
60 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
61 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
62 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
63 #include "gc/shenandoah/shenandoahSTWMark.hpp"
64 #include "gc/shenandoah/shenandoahUtils.hpp"
65 #include "gc/shenandoah/shenandoahVerifier.hpp"
66 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
67 #include "gc/shenandoah/shenandoahVMOperations.hpp"
68 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
69 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
70 #include "gc/shenandoah/mode/shenandoahIUMode.hpp"
71 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
72 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
73 #if INCLUDE_JFR
74 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
75 #endif
76
77 #include "classfile/systemDictionary.hpp"
78 #include "code/codeCache.hpp"
79 #include "memory/classLoaderMetaspace.hpp"
80 #include "memory/metaspaceUtils.hpp"
81 #include "nmt/mallocTracker.hpp"
82 #include "nmt/memTracker.hpp"
83 #include "oops/compressedOops.inline.hpp"
84 #include "prims/jvmtiTagMap.hpp"
85 #include "runtime/atomic.hpp"
86 #include "runtime/globals.hpp"
87 #include "runtime/interfaceSupport.inline.hpp"
88 #include "runtime/java.hpp"
89 #include "runtime/orderAccess.hpp"
90 #include "runtime/safepointMechanism.hpp"
91 #include "runtime/stackWatermarkSet.hpp"
92 #include "runtime/vmThread.hpp"
93 #include "utilities/events.hpp"
94 #include "utilities/powerOfTwo.hpp"
95
96 class ShenandoahPretouchHeapTask : public WorkerTask {
97 private:
98 ShenandoahRegionIterator _regions;
99 const size_t _page_size;
100 public:
101 ShenandoahPretouchHeapTask(size_t page_size) :
102 WorkerTask("Shenandoah Pretouch Heap"),
103 _page_size(page_size) {}
104
105 virtual void work(uint worker_id) {
106 ShenandoahHeapRegion* r = _regions.next();
107 while (r != nullptr) {
108 if (r->is_committed()) {
109 os::pretouch_memory(r->bottom(), r->end(), _page_size);
110 }
111 r = _regions.next();
112 }
113 }
114 };
115
116 class ShenandoahPretouchBitmapTask : public WorkerTask {
117 private:
118 ShenandoahRegionIterator _regions;
119 char* _bitmap_base;
120 const size_t _bitmap_size;
121 const size_t _page_size;
122 public:
123 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
124 WorkerTask("Shenandoah Pretouch Bitmap"),
125 _bitmap_base(bitmap_base),
126 _bitmap_size(bitmap_size),
127 _page_size(page_size) {}
128
129 virtual void work(uint worker_id) {
130 ShenandoahHeapRegion* r = _regions.next();
131 while (r != nullptr) {
132 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
133 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
134 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
135
136 if (r->is_committed()) {
137 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
138 }
139
140 r = _regions.next();
141 }
142 }
143 };
144
145 jint ShenandoahHeap::initialize() {
146 //
147 // Figure out heap sizing
148 //
149
150 size_t init_byte_size = InitialHeapSize;
151 size_t min_byte_size = MinHeapSize;
152 size_t max_byte_size = MaxHeapSize;
153 size_t heap_alignment = HeapAlignment;
154
155 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
156
157 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
158 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
159
160 _num_regions = ShenandoahHeapRegion::region_count();
161 assert(_num_regions == (max_byte_size / reg_size_bytes),
162 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
163 _num_regions, max_byte_size, reg_size_bytes);
164
165 // Now we know the number of regions, initialize the heuristics.
166 initialize_heuristics();
167
168 size_t num_committed_regions = init_byte_size / reg_size_bytes;
169 num_committed_regions = MIN2(num_committed_regions, _num_regions);
170 assert(num_committed_regions <= _num_regions, "sanity");
171 _initial_size = num_committed_regions * reg_size_bytes;
172
173 size_t num_min_regions = min_byte_size / reg_size_bytes;
174 num_min_regions = MIN2(num_min_regions, _num_regions);
175 assert(num_min_regions <= _num_regions, "sanity");
176 _minimum_size = num_min_regions * reg_size_bytes;
177
178 // Default to max heap size.
179 _soft_max_size = _num_regions * reg_size_bytes;
180
181 _committed = _initial_size;
182
183 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
184 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
185 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
186
187 //
188 // Reserve and commit memory for heap
189 //
190
191 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
192 initialize_reserved_region(heap_rs);
193 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
194 _heap_region_special = heap_rs.special();
195
196 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
197 "Misaligned heap: " PTR_FORMAT, p2i(base()));
198 os::trace_page_sizes_for_requested_size("Heap",
199 max_byte_size, heap_alignment,
200 heap_rs.base(),
201 heap_rs.size(), heap_rs.page_size());
202
203 #if SHENANDOAH_OPTIMIZED_MARKTASK
204 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
205 // Fail if we ever attempt to address more than we can.
206 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
207 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
208 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
209 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
210 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
211 vm_exit_during_initialization("Fatal Error", buf);
212 }
213 #endif
214
215 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
216 if (!_heap_region_special) {
217 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
218 "Cannot commit heap memory");
219 }
220
221 //
222 // Reserve and commit memory for bitmap(s)
223 //
224
225 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
226 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
227
228 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
229
230 guarantee(bitmap_bytes_per_region != 0,
231 "Bitmap bytes per region should not be zero");
232 guarantee(is_power_of_2(bitmap_bytes_per_region),
233 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
234
235 if (bitmap_page_size > bitmap_bytes_per_region) {
236 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
237 _bitmap_bytes_per_slice = bitmap_page_size;
238 } else {
239 _bitmap_regions_per_slice = 1;
240 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
241 }
242
243 guarantee(_bitmap_regions_per_slice >= 1,
244 "Should have at least one region per slice: " SIZE_FORMAT,
245 _bitmap_regions_per_slice);
246
247 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
248 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
249 _bitmap_bytes_per_slice, bitmap_page_size);
250
251 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
252 os::trace_page_sizes_for_requested_size("Mark Bitmap",
253 bitmap_size_orig, bitmap_page_size,
254 bitmap.base(),
255 bitmap.size(), bitmap.page_size());
256 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
257 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
258 _bitmap_region_special = bitmap.special();
259
260 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
261 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
262 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
263 if (!_bitmap_region_special) {
264 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
265 "Cannot commit bitmap memory");
266 }
267
268 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions, _max_workers);
269
270 if (ShenandoahVerify) {
271 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
272 os::trace_page_sizes_for_requested_size("Verify Bitmap",
273 bitmap_size_orig, bitmap_page_size,
274 verify_bitmap.base(),
275 verify_bitmap.size(), verify_bitmap.page_size());
276 if (!verify_bitmap.special()) {
277 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
278 "Cannot commit verification bitmap memory");
279 }
280 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
281 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
282 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
283 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
284 }
285
286 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
287 size_t aux_bitmap_page_size = bitmap_page_size;
288 #ifdef LINUX
289 // In THP "advise" mode, we refrain from advising the system to use large pages
290 // since we know these commits will be short lived, and there is no reason to trash
291 // the THP area with this bitmap.
292 if (UseTransparentHugePages) {
293 aux_bitmap_page_size = os::vm_page_size();
294 }
295 #endif
296 ReservedSpace aux_bitmap(_bitmap_size, aux_bitmap_page_size);
297 os::trace_page_sizes_for_requested_size("Aux Bitmap",
298 bitmap_size_orig, aux_bitmap_page_size,
299 aux_bitmap.base(),
300 aux_bitmap.size(), aux_bitmap.page_size());
301 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
302 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
303 _aux_bitmap_region_special = aux_bitmap.special();
304 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
305
306 //
307 // Create regions and region sets
308 //
309 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
310 size_t region_storage_size_orig = region_align * _num_regions;
311 size_t region_storage_size = align_up(region_storage_size_orig,
312 MAX2(region_page_size, os::vm_allocation_granularity()));
313
314 ReservedSpace region_storage(region_storage_size, region_page_size);
315 os::trace_page_sizes_for_requested_size("Region Storage",
316 region_storage_size_orig, region_page_size,
317 region_storage.base(),
318 region_storage.size(), region_storage.page_size());
319 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
320 if (!region_storage.special()) {
321 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
322 "Cannot commit region memory");
323 }
324
325 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
326 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
327 // If not successful, bite a bullet and allocate at whatever address.
328 {
329 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
330 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
331 const size_t cset_page_size = os::vm_page_size();
332
333 uintptr_t min = round_up_power_of_2(cset_align);
334 uintptr_t max = (1u << 30u);
335 ReservedSpace cset_rs;
336
337 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
338 char* req_addr = (char*)addr;
339 assert(is_aligned(req_addr, cset_align), "Should be aligned");
340 cset_rs = ReservedSpace(cset_size, cset_align, cset_page_size, req_addr);
341 if (cset_rs.is_reserved()) {
342 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
343 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
344 break;
345 }
346 }
347
348 if (_collection_set == nullptr) {
349 cset_rs = ReservedSpace(cset_size, cset_align, os::vm_page_size());
350 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
351 }
352 os::trace_page_sizes_for_requested_size("Collection Set",
353 cset_size, cset_page_size,
354 cset_rs.base(),
355 cset_rs.size(), cset_rs.page_size());
356 }
357
358 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
359 _free_set = new ShenandoahFreeSet(this, _num_regions);
360
361 {
362 ShenandoahHeapLocker locker(lock());
363
364 for (size_t i = 0; i < _num_regions; i++) {
365 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
366 bool is_committed = i < num_committed_regions;
367 void* loc = region_storage.base() + i * region_align;
368
369 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
370 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
371
372 _marking_context->initialize_top_at_mark_start(r);
373 _regions[i] = r;
374 assert(!collection_set()->is_in(i), "New region should not be in collection set");
375 }
376
377 // Initialize to complete
378 _marking_context->mark_complete();
379
380 _free_set->rebuild();
381 }
382
383 if (AlwaysPreTouch) {
384 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
385 // before initialize() below zeroes it with initializing thread. For any given region,
386 // we touch the region and the corresponding bitmaps from the same thread.
387 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
388
389 _pretouch_heap_page_size = heap_page_size;
390 _pretouch_bitmap_page_size = bitmap_page_size;
391
392 #ifdef LINUX
393 // UseTransparentHugePages would madvise that backing memory can be coalesced into huge
394 // pages. But, the kernel needs to know that every small page is used, in order to coalesce
395 // them into huge one. Therefore, we need to pretouch with smaller pages.
396 if (UseTransparentHugePages) {
397 _pretouch_heap_page_size = (size_t)os::vm_page_size();
398 _pretouch_bitmap_page_size = (size_t)os::vm_page_size();
399 }
400 #endif
401
402 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
403 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
404
405 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
406 _workers->run_task(&bcl);
407
408 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
409 _workers->run_task(&hcl);
410 }
411
412 //
413 // Initialize the rest of GC subsystems
414 //
415
416 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
417 for (uint worker = 0; worker < _max_workers; worker++) {
418 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
419 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
420 }
421
422 // There should probably be Shenandoah-specific options for these,
423 // just as there are G1-specific options.
424 {
425 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
426 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
427 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
428 }
429
430 _monitoring_support = new ShenandoahMonitoringSupport(this);
431 _phase_timings = new ShenandoahPhaseTimings(max_workers());
432 ShenandoahCodeRoots::initialize();
433
434 if (ShenandoahPacing) {
435 _pacer = new ShenandoahPacer(this);
436 _pacer->setup_for_idle();
437 }
438
439 _control_thread = new ShenandoahControlThread();
440
441 ShenandoahInitLogger::print();
442
443 SlidingForwarding::initialize(_heap_region, ShenandoahHeapRegion::region_size_words());
444
445 return JNI_OK;
446 }
447
448 void ShenandoahHeap::initialize_mode() {
449 if (ShenandoahGCMode != nullptr) {
450 if (strcmp(ShenandoahGCMode, "satb") == 0) {
451 _gc_mode = new ShenandoahSATBMode();
452 } else if (strcmp(ShenandoahGCMode, "iu") == 0) {
453 _gc_mode = new ShenandoahIUMode();
454 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
455 _gc_mode = new ShenandoahPassiveMode();
456 } else {
457 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
458 }
459 } else {
460 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
461 }
462 _gc_mode->initialize_flags();
463 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
464 vm_exit_during_initialization(
465 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
466 _gc_mode->name()));
467 }
468 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
469 vm_exit_during_initialization(
470 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
471 _gc_mode->name()));
472 }
473 }
474
475 void ShenandoahHeap::initialize_heuristics() {
476 assert(_gc_mode != nullptr, "Must be initialized");
477 _heuristics = _gc_mode->initialize_heuristics();
478
479 if (_heuristics->is_diagnostic() && !UnlockDiagnosticVMOptions) {
480 vm_exit_during_initialization(
481 err_msg("Heuristics \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
482 _heuristics->name()));
483 }
484 if (_heuristics->is_experimental() && !UnlockExperimentalVMOptions) {
485 vm_exit_during_initialization(
486 err_msg("Heuristics \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
487 _heuristics->name()));
488 }
489 }
490
491 #ifdef _MSC_VER
492 #pragma warning( push )
493 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
494 #endif
495
496 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
497 CollectedHeap(),
498 _initial_size(0),
499 _used(0),
500 _committed(0),
501 _bytes_allocated_since_gc_start(0),
502 _max_workers(MAX2(ConcGCThreads, ParallelGCThreads)),
503 _workers(nullptr),
504 _safepoint_workers(nullptr),
505 _heap_region_special(false),
506 _num_regions(0),
507 _regions(nullptr),
508 _update_refs_iterator(this),
509 _gc_state_changed(false),
510 _gc_no_progress_count(0),
511 _control_thread(nullptr),
512 _shenandoah_policy(policy),
513 _gc_mode(nullptr),
514 _heuristics(nullptr),
515 _free_set(nullptr),
516 _pacer(nullptr),
517 _verifier(nullptr),
518 _phase_timings(nullptr),
519 _monitoring_support(nullptr),
520 _memory_pool(nullptr),
521 _stw_memory_manager("Shenandoah Pauses"),
522 _cycle_memory_manager("Shenandoah Cycles"),
523 _gc_timer(new ConcurrentGCTimer()),
524 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
525 _ref_processor(new ShenandoahReferenceProcessor(MAX2(_max_workers, 1U))),
526 _marking_context(nullptr),
527 _bitmap_size(0),
528 _bitmap_regions_per_slice(0),
529 _bitmap_bytes_per_slice(0),
530 _bitmap_region_special(false),
531 _aux_bitmap_region_special(false),
532 _liveness_cache(nullptr),
533 _collection_set(nullptr)
534 {
535 // Initialize GC mode early, so we can adjust barrier support
536 initialize_mode();
537 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this));
538
539 _max_workers = MAX2(_max_workers, 1U);
540 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
541 if (_workers == nullptr) {
542 vm_exit_during_initialization("Failed necessary allocation.");
543 } else {
544 _workers->initialize_workers();
545 }
546
547 if (ParallelGCThreads > 1) {
548 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread",
549 ParallelGCThreads);
550 _safepoint_workers->initialize_workers();
551 }
552 }
553
554 #ifdef _MSC_VER
555 #pragma warning( pop )
556 #endif
557
558 class ShenandoahResetBitmapTask : public WorkerTask {
559 private:
560 ShenandoahRegionIterator _regions;
561
562 public:
563 ShenandoahResetBitmapTask() :
564 WorkerTask("Shenandoah Reset Bitmap") {}
565
566 void work(uint worker_id) {
567 ShenandoahHeapRegion* region = _regions.next();
568 ShenandoahHeap* heap = ShenandoahHeap::heap();
569 ShenandoahMarkingContext* const ctx = heap->marking_context();
570 while (region != nullptr) {
571 if (heap->is_bitmap_slice_committed(region)) {
572 ctx->clear_bitmap(region);
573 }
574 region = _regions.next();
575 }
576 }
577 };
578
579 void ShenandoahHeap::reset_mark_bitmap() {
580 assert_gc_workers(_workers->active_workers());
581 mark_incomplete_marking_context();
582
583 ShenandoahResetBitmapTask task;
584 _workers->run_task(&task);
585 }
586
587 void ShenandoahHeap::print_on(outputStream* st) const {
588 st->print_cr("Shenandoah Heap");
589 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
590 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
591 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
592 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
593 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
594 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
595 num_regions(),
596 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
597 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
598
599 st->print("Status: ");
600 if (has_forwarded_objects()) st->print("has forwarded objects, ");
601 if (is_concurrent_mark_in_progress()) st->print("marking, ");
602 if (is_evacuation_in_progress()) st->print("evacuating, ");
603 if (is_update_refs_in_progress()) st->print("updating refs, ");
604 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
605 if (is_full_gc_in_progress()) st->print("full gc, ");
606 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
607 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
608 if (is_concurrent_strong_root_in_progress() &&
609 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
610
611 if (cancelled_gc()) {
612 st->print("cancelled");
613 } else {
614 st->print("not cancelled");
615 }
616 st->cr();
617
618 st->print_cr("Reserved region:");
619 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
620 p2i(reserved_region().start()),
621 p2i(reserved_region().end()));
622
623 ShenandoahCollectionSet* cset = collection_set();
624 st->print_cr("Collection set:");
625 if (cset != nullptr) {
626 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
627 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
628 } else {
629 st->print_cr(" (null)");
630 }
631
632 st->cr();
633 MetaspaceUtils::print_on(st);
634
635 if (Verbose) {
636 st->cr();
637 print_heap_regions_on(st);
638 }
639 }
640
641 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
642 public:
643 void do_thread(Thread* thread) {
644 assert(thread != nullptr, "Sanity");
645 assert(thread->is_Worker_thread(), "Only worker thread expected");
646 ShenandoahThreadLocalData::initialize_gclab(thread);
647 }
648 };
649
650 void ShenandoahHeap::post_initialize() {
651 CollectedHeap::post_initialize();
652 MutexLocker ml(Threads_lock);
653
654 ShenandoahInitWorkerGCLABClosure init_gclabs;
655 _workers->threads_do(&init_gclabs);
656
657 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
658 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
659 _workers->set_initialize_gclab();
660 if (_safepoint_workers != nullptr) {
661 _safepoint_workers->threads_do(&init_gclabs);
662 _safepoint_workers->set_initialize_gclab();
663 }
664
665 _heuristics->initialize();
666
667 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
668 }
669
670 size_t ShenandoahHeap::used() const {
671 return Atomic::load(&_used);
672 }
673
674 size_t ShenandoahHeap::committed() const {
675 return Atomic::load(&_committed);
676 }
677
678 size_t ShenandoahHeap::available() const {
679 return free_set()->available();
680 }
681
682 void ShenandoahHeap::increase_committed(size_t bytes) {
683 shenandoah_assert_heaplocked_or_safepoint();
684 _committed += bytes;
685 }
686
687 void ShenandoahHeap::decrease_committed(size_t bytes) {
688 shenandoah_assert_heaplocked_or_safepoint();
689 _committed -= bytes;
690 }
691
692 void ShenandoahHeap::increase_used(size_t bytes) {
693 Atomic::add(&_used, bytes, memory_order_relaxed);
694 }
695
696 void ShenandoahHeap::set_used(size_t bytes) {
697 Atomic::store(&_used, bytes);
698 }
699
700 void ShenandoahHeap::decrease_used(size_t bytes) {
701 assert(used() >= bytes, "never decrease heap size by more than we've left");
702 Atomic::sub(&_used, bytes, memory_order_relaxed);
703 }
704
705 void ShenandoahHeap::increase_allocated(size_t bytes) {
706 Atomic::add(&_bytes_allocated_since_gc_start, bytes, memory_order_relaxed);
707 }
708
709 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, bool waste) {
710 size_t bytes = words * HeapWordSize;
711 if (!waste) {
712 increase_used(bytes);
713 }
714 increase_allocated(bytes);
715 if (ShenandoahPacing) {
716 control_thread()->pacing_notify_alloc(words);
717 if (waste) {
718 pacer()->claim_for_alloc(words, true);
719 }
720 }
721 }
722
723 size_t ShenandoahHeap::capacity() const {
724 return committed();
725 }
726
727 size_t ShenandoahHeap::max_capacity() const {
728 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
729 }
730
731 size_t ShenandoahHeap::soft_max_capacity() const {
732 size_t v = Atomic::load(&_soft_max_size);
733 assert(min_capacity() <= v && v <= max_capacity(),
734 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
735 min_capacity(), v, max_capacity());
736 return v;
737 }
738
739 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
740 assert(min_capacity() <= v && v <= max_capacity(),
741 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
742 min_capacity(), v, max_capacity());
743 Atomic::store(&_soft_max_size, v);
744 }
745
746 size_t ShenandoahHeap::min_capacity() const {
747 return _minimum_size;
748 }
749
750 size_t ShenandoahHeap::initial_capacity() const {
751 return _initial_size;
752 }
753
754 bool ShenandoahHeap::is_in(const void* p) const {
755 HeapWord* heap_base = (HeapWord*) base();
756 HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
757 return p >= heap_base && p < last_region_end;
758 }
759
760 void ShenandoahHeap::maybe_uncommit(double shrink_before, size_t shrink_until) {
761 assert (ShenandoahUncommit, "should be enabled");
762
763 // Determine if there is work to do. This avoids taking heap lock if there is
764 // no work available, avoids spamming logs with superfluous logging messages,
765 // and minimises the amount of work while locks are taken.
766
767 if (committed() <= shrink_until) return;
768
769 bool has_work = false;
770 for (size_t i = 0; i < num_regions(); i++) {
771 ShenandoahHeapRegion* r = get_region(i);
772 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
773 has_work = true;
774 break;
775 }
776 }
777
778 if (has_work) {
779 static const char* msg = "Concurrent uncommit";
780 ShenandoahConcurrentPhase gcPhase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
781 EventMark em("%s", msg);
782
783 op_uncommit(shrink_before, shrink_until);
784 }
785 }
786
787 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
788 assert (ShenandoahUncommit, "should be enabled");
789
790 // Application allocates from the beginning of the heap, and GC allocates at
791 // the end of it. It is more efficient to uncommit from the end, so that applications
792 // could enjoy the near committed regions. GC allocations are much less frequent,
793 // and therefore can accept the committing costs.
794
795 size_t count = 0;
796 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
797 ShenandoahHeapRegion* r = get_region(i - 1);
798 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
799 ShenandoahHeapLocker locker(lock());
800 if (r->is_empty_committed()) {
801 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
802 break;
803 }
804
805 r->make_uncommitted();
806 count++;
807 }
808 }
809 SpinPause(); // allow allocators to take the lock
810 }
811
812 if (count > 0) {
813 notify_heap_changed();
814 }
815 }
816
817 bool ShenandoahHeap::check_soft_max_changed() {
818 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
819 size_t old_soft_max = soft_max_capacity();
820 if (new_soft_max != old_soft_max) {
821 new_soft_max = MAX2(min_capacity(), new_soft_max);
822 new_soft_max = MIN2(max_capacity(), new_soft_max);
823 if (new_soft_max != old_soft_max) {
824 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
825 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
826 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
827 );
828 set_soft_max_capacity(new_soft_max);
829 return true;
830 }
831 }
832 return false;
833 }
834
835 void ShenandoahHeap::notify_heap_changed() {
836 // Update monitoring counters when we took a new region. This amortizes the
837 // update costs on slow path.
838 monitoring_support()->notify_heap_changed();
839
840 // This is called from allocation path, and thus should be fast.
841 _heap_changed.try_set();
842 }
843
844 void ShenandoahHeap::set_forced_counters_update(bool value) {
845 monitoring_support()->set_forced_counters_update(value);
846 }
847
848 void ShenandoahHeap::handle_force_counters_update() {
849 monitoring_support()->handle_force_counters_update();
850 }
851
852 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
853 // New object should fit the GCLAB size
854 size_t min_size = MAX2(size, PLAB::min_size());
855
856 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
857 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
858 new_size = MIN2(new_size, PLAB::max_size());
859 new_size = MAX2(new_size, PLAB::min_size());
860
861 // Record new heuristic value even if we take any shortcut. This captures
862 // the case when moderately-sized objects always take a shortcut. At some point,
863 // heuristics should catch up with them.
864 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
865
866 if (new_size < size) {
867 // New size still does not fit the object. Fall back to shared allocation.
868 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
869 return nullptr;
870 }
871
872 // Retire current GCLAB, and allocate a new one.
873 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
874 gclab->retire();
875
876 size_t actual_size = 0;
877 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
878 if (gclab_buf == nullptr) {
879 return nullptr;
880 }
881
882 assert (size <= actual_size, "allocation should fit");
883
884 // ...and clear or zap just allocated TLAB, if needed.
885 if (ZeroTLAB) {
886 Copy::zero_to_words(gclab_buf, actual_size);
887 } else if (ZapTLAB) {
888 // Skip mangling the space corresponding to the object header to
889 // ensure that the returned space is not considered parsable by
890 // any concurrent GC thread.
891 size_t hdr_size = oopDesc::header_size();
892 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
893 }
894 gclab->set_buf(gclab_buf, actual_size);
895 return gclab->allocate(size);
896 }
897
898 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
899 size_t requested_size,
900 size_t* actual_size) {
901 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
902 HeapWord* res = allocate_memory(req);
903 if (res != nullptr) {
904 *actual_size = req.actual_size();
905 } else {
906 *actual_size = 0;
907 }
908 return res;
909 }
910
911 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
912 size_t word_size,
913 size_t* actual_size) {
914 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
915 HeapWord* res = allocate_memory(req);
916 if (res != nullptr) {
917 *actual_size = req.actual_size();
918 } else {
919 *actual_size = 0;
920 }
921 return res;
922 }
923
924 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
925 intptr_t pacer_epoch = 0;
926 bool in_new_region = false;
927 HeapWord* result = nullptr;
928
929 if (req.is_mutator_alloc()) {
930 if (ShenandoahPacing) {
931 pacer()->pace_for_alloc(req.size());
932 pacer_epoch = pacer()->epoch();
933 }
934
935 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
936 result = allocate_memory_under_lock(req, in_new_region);
937 }
938
939 // Check that gc overhead is not exceeded.
940 //
941 // Shenandoah will grind along for quite a while allocating one
942 // object at a time using shared (non-tlab) allocations. This check
943 // is testing that the GC overhead limit has not been exceeded.
944 // This will notify the collector to start a cycle, but will raise
945 // an OOME to the mutator if the last Full GCs have not made progress.
946 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
947 control_thread()->handle_alloc_failure(req, false);
948 return nullptr;
949 }
950
951 // Block until control thread reacted, then retry allocation.
952 //
953 // It might happen that one of the threads requesting allocation would unblock
954 // way later after GC happened, only to fail the second allocation, because
955 // other threads have already depleted the free storage. In this case, a better
956 // strategy is to try again, as long as GC makes progress (or until at least
957 // one full GC has completed).
958 size_t original_count = shenandoah_policy()->full_gc_count();
959 while (result == nullptr
960 && (get_gc_no_progress_count() == 0 || original_count == shenandoah_policy()->full_gc_count())) {
961 control_thread()->handle_alloc_failure(req, true);
962 result = allocate_memory_under_lock(req, in_new_region);
963 }
964
965 if (log_is_enabled(Debug, gc, alloc)) {
966 ResourceMark rm;
967 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: " SIZE_FORMAT ", Original: " SIZE_FORMAT ", Latest: " SIZE_FORMAT,
968 Thread::current()->name(), p2i(result), req.type_string(), req.size(), original_count, get_gc_no_progress_count());
969 }
970 } else {
971 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
972 result = allocate_memory_under_lock(req, in_new_region);
973 // Do not call handle_alloc_failure() here, because we cannot block.
974 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
975 }
976
977 if (in_new_region) {
978 notify_heap_changed();
979 }
980
981 if (result != nullptr) {
982 size_t requested = req.size();
983 size_t actual = req.actual_size();
984
985 assert (req.is_lab_alloc() || (requested == actual),
986 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
987 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
988
989 if (req.is_mutator_alloc()) {
990 notify_mutator_alloc_words(actual, false);
991
992 // If we requested more than we were granted, give the rest back to pacer.
993 // This only matters if we are in the same pacing epoch: do not try to unpace
994 // over the budget for the other phase.
995 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
996 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
997 }
998 } else {
999 increase_used(actual*HeapWordSize);
1000 }
1001 }
1002
1003 return result;
1004 }
1005
1006 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1007 // If we are dealing with mutator allocation, then we may need to block for safepoint.
1008 // We cannot block for safepoint for GC allocations, because there is a high chance
1009 // we are already running at safepoint or from stack watermark machinery, and we cannot
1010 // block again.
1011 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1012 return _free_set->allocate(req, in_new_region);
1013 }
1014
1015 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1016 bool* gc_overhead_limit_was_exceeded) {
1017 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1018 return allocate_memory(req);
1019 }
1020
1021 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1022 size_t size,
1023 Metaspace::MetadataType mdtype) {
1024 MetaWord* result;
1025
1026 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1027 if (heuristics()->can_unload_classes()) {
1028 ShenandoahHeuristics* h = heuristics();
1029 h->record_metaspace_oom();
1030 }
1031
1032 // Expand and retry allocation
1033 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1034 if (result != nullptr) {
1035 return result;
1036 }
1037
1038 // Start full GC
1039 collect(GCCause::_metadata_GC_clear_soft_refs);
1040
1041 // Retry allocation
1042 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1043 if (result != nullptr) {
1044 return result;
1045 }
1046
1047 // Expand and retry allocation
1048 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1049 if (result != nullptr) {
1050 return result;
1051 }
1052
1053 // Out of memory
1054 return nullptr;
1055 }
1056
1057 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1058 private:
1059 ShenandoahHeap* const _heap;
1060 Thread* const _thread;
1061 public:
1062 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1063 _heap(heap), _thread(Thread::current()) {}
1064
1065 void do_object(oop p) {
1066 shenandoah_assert_marked(nullptr, p);
1067 if (!p->is_forwarded()) {
1068 _heap->evacuate_object(p, _thread);
1069 }
1070 }
1071 };
1072
1073 class ShenandoahEvacuationTask : public WorkerTask {
1074 private:
1075 ShenandoahHeap* const _sh;
1076 ShenandoahCollectionSet* const _cs;
1077 bool _concurrent;
1078 public:
1079 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1080 ShenandoahCollectionSet* cs,
1081 bool concurrent) :
1082 WorkerTask("Shenandoah Evacuation"),
1083 _sh(sh),
1084 _cs(cs),
1085 _concurrent(concurrent)
1086 {}
1087
1088 void work(uint worker_id) {
1089 if (_concurrent) {
1090 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1091 ShenandoahSuspendibleThreadSetJoiner stsj;
1092 ShenandoahEvacOOMScope oom_evac_scope;
1093 do_work();
1094 } else {
1095 ShenandoahParallelWorkerSession worker_session(worker_id);
1096 ShenandoahEvacOOMScope oom_evac_scope;
1097 do_work();
1098 }
1099 }
1100
1101 private:
1102 void do_work() {
1103 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1104 ShenandoahHeapRegion* r;
1105 while ((r =_cs->claim_next()) != nullptr) {
1106 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1107 _sh->marked_object_iterate(r, &cl);
1108
1109 if (ShenandoahPacing) {
1110 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1111 }
1112
1113 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1114 break;
1115 }
1116 }
1117 }
1118 };
1119
1120 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1121 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1122 workers()->run_task(&task);
1123 }
1124
1125 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1126 if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
1127 // This thread went through the OOM during evac protocol and it is safe to return
1128 // the forward pointer. It must not attempt to evacuate any more.
1129 return ShenandoahBarrierSet::resolve_forwarded(p);
1130 }
1131
1132 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1133
1134 size_t size = p->forward_safe_size();
1135
1136 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
1137
1138 bool alloc_from_gclab = true;
1139 HeapWord* copy = nullptr;
1140
1141 #ifdef ASSERT
1142 if (ShenandoahOOMDuringEvacALot &&
1143 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1144 copy = nullptr;
1145 } else {
1146 #endif
1147 if (UseTLAB) {
1148 copy = allocate_from_gclab(thread, size);
1149 }
1150 if (copy == nullptr) {
1151 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
1152 copy = allocate_memory(req);
1153 alloc_from_gclab = false;
1154 }
1155 #ifdef ASSERT
1156 }
1157 #endif
1158
1159 if (copy == nullptr) {
1160 control_thread()->handle_alloc_failure_evac(size);
1161
1162 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1163
1164 return ShenandoahBarrierSet::resolve_forwarded(p);
1165 }
1166
1167 // Copy the object:
1168 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1169 oop copy_val = cast_to_oop(copy);
1170
1171 if (UseCompactObjectHeaders) {
1172 // The copy above is not atomic. Make sure we have seen the proper mark
1173 // and re-install it into the copy, so that Klass* is guaranteed to be correct.
1174 markWord mark = copy_val->mark();
1175 if (!mark.is_marked()) {
1176 copy_val->set_mark(mark);
1177 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1178 } else {
1179 // If we copied a mark-word that indicates 'forwarded' state, the object
1180 // installation would not succeed. We cannot access Klass* anymore either.
1181 // Skip the transformation.
1182 }
1183 } else {
1184 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1185 }
1186
1187 // Try to install the new forwarding pointer.
1188 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1189 if (result == copy_val) {
1190 // Successfully evacuated. Our copy is now the public one!
1191 shenandoah_assert_correct(nullptr, copy_val);
1192 return copy_val;
1193 } else {
1194 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1195 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1196 // But if it happens to contain references to evacuated regions, those references would
1197 // not get updated for this stale copy during this cycle, and we will crash while scanning
1198 // it the next cycle.
1199 //
1200 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
1201 // object will overwrite this stale copy, or the filler object on LAB retirement will
1202 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
1203 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1204 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1205 if (alloc_from_gclab) {
1206 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1207 } else {
1208 fill_with_object(copy, size);
1209 shenandoah_assert_correct(nullptr, copy_val);
1210 }
1211 shenandoah_assert_correct(nullptr, result);
1212 return result;
1213 }
1214 }
1215
1216 void ShenandoahHeap::trash_cset_regions() {
1217 ShenandoahHeapLocker locker(lock());
1218
1219 ShenandoahCollectionSet* set = collection_set();
1220 ShenandoahHeapRegion* r;
1221 set->clear_current_index();
1222 while ((r = set->next()) != nullptr) {
1223 r->make_trash();
1224 }
1225 collection_set()->clear();
1226 }
1227
1228 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1229 st->print_cr("Heap Regions:");
1230 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1231 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1232 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1233 st->print_cr("UWM=update watermark, U=used");
1234 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1235 st->print_cr("S=shared allocs, L=live data");
1236 st->print_cr("CP=critical pins");
1237
1238 for (size_t i = 0; i < num_regions(); i++) {
1239 get_region(i)->print_on(st);
1240 }
1241 }
1242
1243 void ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1244 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1245
1246 oop humongous_obj = cast_to_oop(start->bottom());
1247 size_t size = humongous_obj->size();
1248 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1249 size_t index = start->index() + required_regions - 1;
1250
1251 assert(!start->has_live(), "liveness must be zero");
1252
1253 for(size_t i = 0; i < required_regions; i++) {
1254 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1255 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1256 ShenandoahHeapRegion* region = get_region(index --);
1257
1258 assert(region->is_humongous(), "expect correct humongous start or continuation");
1259 assert(!region->is_cset(), "Humongous region should not be in collection set");
1260
1261 region->make_trash_immediate();
1262 }
1263 }
1264
1265 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1266 public:
1267 ShenandoahCheckCleanGCLABClosure() {}
1268 void do_thread(Thread* thread) {
1269 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1270 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1271 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1272 }
1273 };
1274
1275 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1276 private:
1277 bool const _resize;
1278 public:
1279 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1280 void do_thread(Thread* thread) {
1281 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1282 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1283 gclab->retire();
1284 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1285 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1286 }
1287 }
1288 };
1289
1290 void ShenandoahHeap::labs_make_parsable() {
1291 assert(UseTLAB, "Only call with UseTLAB");
1292
1293 ShenandoahRetireGCLABClosure cl(false);
1294
1295 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1296 ThreadLocalAllocBuffer& tlab = t->tlab();
1297 tlab.make_parsable();
1298 cl.do_thread(t);
1299 }
1300
1301 workers()->threads_do(&cl);
1302 }
1303
1304 void ShenandoahHeap::tlabs_retire(bool resize) {
1305 assert(UseTLAB, "Only call with UseTLAB");
1306 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1307
1308 ThreadLocalAllocStats stats;
1309
1310 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1311 ThreadLocalAllocBuffer& tlab = t->tlab();
1312 tlab.retire(&stats);
1313 if (resize) {
1314 tlab.resize();
1315 }
1316 }
1317
1318 stats.publish();
1319
1320 #ifdef ASSERT
1321 ShenandoahCheckCleanGCLABClosure cl;
1322 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1323 cl.do_thread(t);
1324 }
1325 workers()->threads_do(&cl);
1326 #endif
1327 }
1328
1329 void ShenandoahHeap::gclabs_retire(bool resize) {
1330 assert(UseTLAB, "Only call with UseTLAB");
1331 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1332
1333 ShenandoahRetireGCLABClosure cl(resize);
1334 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1335 cl.do_thread(t);
1336 }
1337 workers()->threads_do(&cl);
1338
1339 if (safepoint_workers() != nullptr) {
1340 safepoint_workers()->threads_do(&cl);
1341 }
1342 }
1343
1344 // Returns size in bytes
1345 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1346 // Return the max allowed size, and let the allocation path
1347 // figure out the safe size for current allocation.
1348 return ShenandoahHeapRegion::max_tlab_size_bytes();
1349 }
1350
1351 size_t ShenandoahHeap::max_tlab_size() const {
1352 // Returns size in words
1353 return ShenandoahHeapRegion::max_tlab_size_words();
1354 }
1355
1356 void ShenandoahHeap::collect(GCCause::Cause cause) {
1357 control_thread()->request_gc(cause);
1358 }
1359
1360 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1361 //assert(false, "Shouldn't need to do full collections");
1362 }
1363
1364 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1365 ShenandoahHeapRegion* r = heap_region_containing(addr);
1366 if (r != nullptr) {
1367 return r->block_start(addr);
1368 }
1369 return nullptr;
1370 }
1371
1372 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1373 ShenandoahHeapRegion* r = heap_region_containing(addr);
1374 return r->block_is_obj(addr);
1375 }
1376
1377 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1378 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1379 }
1380
1381 void ShenandoahHeap::prepare_for_verify() {
1382 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1383 labs_make_parsable();
1384 }
1385 }
1386
1387 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1388 if (_shenandoah_policy->is_at_shutdown()) {
1389 return;
1390 }
1391
1392 if (_control_thread != nullptr) {
1393 tcl->do_thread(_control_thread);
1394 }
1395
1396 workers()->threads_do(tcl);
1397 if (_safepoint_workers != nullptr) {
1398 _safepoint_workers->threads_do(tcl);
1399 }
1400 }
1401
1402 void ShenandoahHeap::print_tracing_info() const {
1403 LogTarget(Info, gc, stats) lt;
1404 if (lt.is_enabled()) {
1405 ResourceMark rm;
1406 LogStream ls(lt);
1407
1408 phase_timings()->print_global_on(&ls);
1409
1410 ls.cr();
1411 ls.cr();
1412
1413 shenandoah_policy()->print_gc_stats(&ls);
1414
1415 ls.cr();
1416 ls.cr();
1417 }
1418 }
1419
1420 void ShenandoahHeap::verify(VerifyOption vo) {
1421 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1422 if (ShenandoahVerify) {
1423 verifier()->verify_generic(vo);
1424 } else {
1425 // TODO: Consider allocating verification bitmaps on demand,
1426 // and turn this on unconditionally.
1427 }
1428 }
1429 }
1430 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1431 return _free_set->capacity();
1432 }
1433
1434 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1435 private:
1436 MarkBitMap* _bitmap;
1437 ShenandoahScanObjectStack* _oop_stack;
1438 ShenandoahHeap* const _heap;
1439 ShenandoahMarkingContext* const _marking_context;
1440
1441 template <class T>
1442 void do_oop_work(T* p) {
1443 T o = RawAccess<>::oop_load(p);
1444 if (!CompressedOops::is_null(o)) {
1445 oop obj = CompressedOops::decode_not_null(o);
1446 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1447 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1448 return;
1449 }
1450 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1451
1452 assert(oopDesc::is_oop(obj), "must be a valid oop");
1453 if (!_bitmap->is_marked(obj)) {
1454 _bitmap->mark(obj);
1455 _oop_stack->push(obj);
1456 }
1457 }
1458 }
1459 public:
1460 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1461 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1462 _marking_context(_heap->marking_context()) {}
1463 void do_oop(oop* p) { do_oop_work(p); }
1464 void do_oop(narrowOop* p) { do_oop_work(p); }
1465 };
1466
1467 /*
1468 * This is public API, used in preparation of object_iterate().
1469 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1470 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1471 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1472 */
1473 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1474 // No-op.
1475 }
1476
1477 /*
1478 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1479 *
1480 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1481 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1482 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1483 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1484 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1485 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1486 * wiped the bitmap in preparation for next marking).
1487 *
1488 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1489 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1490 * is allowed to report dead objects, but is not required to do so.
1491 */
1492 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1493 // Reset bitmap
1494 if (!prepare_aux_bitmap_for_iteration())
1495 return;
1496
1497 ShenandoahScanObjectStack oop_stack;
1498 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1499 // Seed the stack with root scan
1500 scan_roots_for_iteration(&oop_stack, &oops);
1501
1502 // Work through the oop stack to traverse heap
1503 while (! oop_stack.is_empty()) {
1504 oop obj = oop_stack.pop();
1505 assert(oopDesc::is_oop(obj), "must be a valid oop");
1506 cl->do_object(obj);
1507 obj->oop_iterate(&oops);
1508 }
1509
1510 assert(oop_stack.is_empty(), "should be empty");
1511 // Reclaim bitmap
1512 reclaim_aux_bitmap_for_iteration();
1513 }
1514
1515 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1516 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1517
1518 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1519 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1520 return false;
1521 }
1522 // Reset bitmap
1523 _aux_bit_map.clear();
1524 return true;
1525 }
1526
1527 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1528 // Process GC roots according to current GC cycle
1529 // This populates the work stack with initial objects
1530 // It is important to relinquish the associated locks before diving
1531 // into heap dumper
1532 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1533 ShenandoahHeapIterationRootScanner rp(n_workers);
1534 rp.roots_do(oops);
1535 }
1536
1537 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1538 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1539 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1540 }
1541 }
1542
1543 // Closure for parallelly iterate objects
1544 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1545 private:
1546 MarkBitMap* _bitmap;
1547 ShenandoahObjToScanQueue* _queue;
1548 ShenandoahHeap* const _heap;
1549 ShenandoahMarkingContext* const _marking_context;
1550
1551 template <class T>
1552 void do_oop_work(T* p) {
1553 T o = RawAccess<>::oop_load(p);
1554 if (!CompressedOops::is_null(o)) {
1555 oop obj = CompressedOops::decode_not_null(o);
1556 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1557 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1558 return;
1559 }
1560 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1561
1562 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1563 if (_bitmap->par_mark(obj)) {
1564 _queue->push(ShenandoahMarkTask(obj));
1565 }
1566 }
1567 }
1568 public:
1569 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1570 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1571 _marking_context(_heap->marking_context()) {}
1572 void do_oop(oop* p) { do_oop_work(p); }
1573 void do_oop(narrowOop* p) { do_oop_work(p); }
1574 };
1575
1576 // Object iterator for parallel heap iteraion.
1577 // The root scanning phase happenes in construction as a preparation of
1578 // parallel marking queues.
1579 // Every worker processes it's own marking queue. work-stealing is used
1580 // to balance workload.
1581 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1582 private:
1583 uint _num_workers;
1584 bool _init_ready;
1585 MarkBitMap* _aux_bit_map;
1586 ShenandoahHeap* _heap;
1587 ShenandoahScanObjectStack _roots_stack; // global roots stack
1588 ShenandoahObjToScanQueueSet* _task_queues;
1589 public:
1590 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1591 _num_workers(num_workers),
1592 _init_ready(false),
1593 _aux_bit_map(bitmap),
1594 _heap(ShenandoahHeap::heap()) {
1595 // Initialize bitmap
1596 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1597 if (!_init_ready) {
1598 return;
1599 }
1600
1601 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1602 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1603
1604 _init_ready = prepare_worker_queues();
1605 }
1606
1607 ~ShenandoahParallelObjectIterator() {
1608 // Reclaim bitmap
1609 _heap->reclaim_aux_bitmap_for_iteration();
1610 // Reclaim queue for workers
1611 if (_task_queues!= nullptr) {
1612 for (uint i = 0; i < _num_workers; ++i) {
1613 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1614 if (q != nullptr) {
1615 delete q;
1616 _task_queues->register_queue(i, nullptr);
1617 }
1618 }
1619 delete _task_queues;
1620 _task_queues = nullptr;
1621 }
1622 }
1623
1624 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1625 if (_init_ready) {
1626 object_iterate_parallel(cl, worker_id, _task_queues);
1627 }
1628 }
1629
1630 private:
1631 // Divide global root_stack into worker queues
1632 bool prepare_worker_queues() {
1633 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1634 // Initialize queues for every workers
1635 for (uint i = 0; i < _num_workers; ++i) {
1636 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1637 _task_queues->register_queue(i, task_queue);
1638 }
1639 // Divide roots among the workers. Assume that object referencing distribution
1640 // is related with root kind, use round-robin to make every worker have same chance
1641 // to process every kind of roots
1642 size_t roots_num = _roots_stack.size();
1643 if (roots_num == 0) {
1644 // No work to do
1645 return false;
1646 }
1647
1648 for (uint j = 0; j < roots_num; j++) {
1649 uint stack_id = j % _num_workers;
1650 oop obj = _roots_stack.pop();
1651 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1652 }
1653 return true;
1654 }
1655
1656 void object_iterate_parallel(ObjectClosure* cl,
1657 uint worker_id,
1658 ShenandoahObjToScanQueueSet* queue_set) {
1659 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1660 assert(queue_set != nullptr, "task queue must not be null");
1661
1662 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1663 assert(q != nullptr, "object iterate queue must not be null");
1664
1665 ShenandoahMarkTask t;
1666 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1667
1668 // Work through the queue to traverse heap.
1669 // Steal when there is no task in queue.
1670 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1671 oop obj = t.obj();
1672 assert(oopDesc::is_oop(obj), "must be a valid oop");
1673 cl->do_object(obj);
1674 obj->oop_iterate(&oops);
1675 }
1676 assert(q->is_empty(), "should be empty");
1677 }
1678 };
1679
1680 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1681 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1682 }
1683
1684 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1685 void ShenandoahHeap::keep_alive(oop obj) {
1686 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1687 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1688 }
1689 }
1690
1691 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1692 for (size_t i = 0; i < num_regions(); i++) {
1693 ShenandoahHeapRegion* current = get_region(i);
1694 blk->heap_region_do(current);
1695 }
1696 }
1697
1698 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1699 private:
1700 ShenandoahHeap* const _heap;
1701 ShenandoahHeapRegionClosure* const _blk;
1702
1703 shenandoah_padding(0);
1704 volatile size_t _index;
1705 shenandoah_padding(1);
1706
1707 public:
1708 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk) :
1709 WorkerTask("Shenandoah Parallel Region Operation"),
1710 _heap(ShenandoahHeap::heap()), _blk(blk), _index(0) {}
1711
1712 void work(uint worker_id) {
1713 ShenandoahParallelWorkerSession worker_session(worker_id);
1714 size_t stride = ShenandoahParallelRegionStride;
1715
1716 size_t max = _heap->num_regions();
1717 while (Atomic::load(&_index) < max) {
1718 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1719 size_t start = cur;
1720 size_t end = MIN2(cur + stride, max);
1721 if (start >= max) break;
1722
1723 for (size_t i = cur; i < end; i++) {
1724 ShenandoahHeapRegion* current = _heap->get_region(i);
1725 _blk->heap_region_do(current);
1726 }
1727 }
1728 }
1729 };
1730
1731 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1732 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1733 if (num_regions() > ShenandoahParallelRegionStride) {
1734 ShenandoahParallelHeapRegionTask task(blk);
1735 workers()->run_task(&task);
1736 } else {
1737 heap_region_iterate(blk);
1738 }
1739 }
1740
1741 class ShenandoahRendezvousClosure : public HandshakeClosure {
1742 public:
1743 inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
1744 inline void do_thread(Thread* thread) {}
1745 };
1746
1747 void ShenandoahHeap::rendezvous_threads() {
1748 ShenandoahRendezvousClosure cl;
1749 Handshake::execute(&cl);
1750 }
1751
1752 void ShenandoahHeap::recycle_trash() {
1753 free_set()->recycle_trash();
1754 }
1755
1756 class ShenandoahResetUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1757 private:
1758 ShenandoahMarkingContext* const _ctx;
1759 public:
1760 ShenandoahResetUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
1761
1762 void heap_region_do(ShenandoahHeapRegion* r) {
1763 if (r->is_active()) {
1764 // Reset live data and set TAMS optimistically. We would recheck these under the pause
1765 // anyway to capture any updates that happened since now.
1766 r->clear_live_data();
1767 _ctx->capture_top_at_mark_start(r);
1768 }
1769 }
1770
1771 bool is_thread_safe() { return true; }
1772 };
1773
1774 void ShenandoahHeap::prepare_gc() {
1775 reset_mark_bitmap();
1776
1777 ShenandoahResetUpdateRegionStateClosure cl;
1778 parallel_heap_region_iterate(&cl);
1779 }
1780
1781 class ShenandoahFinalMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
1782 private:
1783 ShenandoahMarkingContext* const _ctx;
1784 ShenandoahHeapLock* const _lock;
1785
1786 public:
1787 ShenandoahFinalMarkUpdateRegionStateClosure() :
1788 _ctx(ShenandoahHeap::heap()->complete_marking_context()), _lock(ShenandoahHeap::heap()->lock()) {}
1789
1790 void heap_region_do(ShenandoahHeapRegion* r) {
1791 if (r->is_active()) {
1792 // All allocations past TAMS are implicitly live, adjust the region data.
1793 // Bitmaps/TAMS are swapped at this point, so we need to poll complete bitmap.
1794 HeapWord *tams = _ctx->top_at_mark_start(r);
1795 HeapWord *top = r->top();
1796 if (top > tams) {
1797 r->increase_live_data_alloc_words(pointer_delta(top, tams));
1798 }
1799
1800 // We are about to select the collection set, make sure it knows about
1801 // current pinning status. Also, this allows trashing more regions that
1802 // now have their pinning status dropped.
1803 if (r->is_pinned()) {
1804 if (r->pin_count() == 0) {
1805 ShenandoahHeapLocker locker(_lock);
1806 r->make_unpinned();
1807 }
1808 } else {
1809 if (r->pin_count() > 0) {
1810 ShenandoahHeapLocker locker(_lock);
1811 r->make_pinned();
1812 }
1813 }
1814
1815 // Remember limit for updating refs. It's guaranteed that we get no
1816 // from-space-refs written from here on.
1817 r->set_update_watermark_at_safepoint(r->top());
1818 } else {
1819 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
1820 assert(_ctx->top_at_mark_start(r) == r->top(),
1821 "Region " SIZE_FORMAT " should have correct TAMS", r->index());
1822 }
1823 }
1824
1825 bool is_thread_safe() { return true; }
1826 };
1827
1828 void ShenandoahHeap::prepare_regions_and_collection_set(bool concurrent) {
1829 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
1830 {
1831 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states :
1832 ShenandoahPhaseTimings::degen_gc_final_update_region_states);
1833 ShenandoahFinalMarkUpdateRegionStateClosure cl;
1834 parallel_heap_region_iterate(&cl);
1835
1836 assert_pinned_region_status();
1837 }
1838
1839 {
1840 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset :
1841 ShenandoahPhaseTimings::degen_gc_choose_cset);
1842 ShenandoahHeapLocker locker(lock());
1843 _collection_set->clear();
1844 heuristics()->choose_collection_set(_collection_set);
1845 }
1846
1847 {
1848 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset :
1849 ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
1850 ShenandoahHeapLocker locker(lock());
1851 _free_set->rebuild();
1852 }
1853 }
1854
1855 void ShenandoahHeap::do_class_unloading() {
1856 _unloader.unload();
1857 }
1858
1859 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1860 // Weak refs processing
1861 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1862 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1863 ShenandoahTimingsTracker t(phase);
1864 ShenandoahGCWorkerPhase worker_phase(phase);
1865 ref_processor()->process_references(phase, workers(), false /* concurrent */);
1866 }
1867
1868 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1869 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1870
1871 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1872 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1873 // for future GCLABs here.
1874 if (UseTLAB) {
1875 ShenandoahGCPhase phase(concurrent ?
1876 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1877 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1878 gclabs_retire(ResizeTLAB);
1879 }
1880
1881 _update_refs_iterator.reset();
1882 }
1883
1884 void ShenandoahHeap::propagate_gc_state_to_java_threads() {
1885 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1886 if (_gc_state_changed) {
1887 _gc_state_changed = false;
1888 char state = gc_state();
1889 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1890 ShenandoahThreadLocalData::set_gc_state(t, state);
1891 }
1892 }
1893 }
1894
1895 void ShenandoahHeap::set_gc_state(uint mask, bool value) {
1896 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1897 _gc_state.set_cond(mask, value);
1898 _gc_state_changed = true;
1899 }
1900
1901 void ShenandoahHeap::set_concurrent_mark_in_progress(bool in_progress) {
1902 assert(!has_forwarded_objects(), "Not expected before/after mark phase");
1903 set_gc_state(MARKING, in_progress);
1904 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(in_progress, !in_progress);
1905 }
1906
1907 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
1908 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
1909 set_gc_state(EVACUATION, in_progress);
1910 }
1911
1912 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
1913 if (in_progress) {
1914 _concurrent_strong_root_in_progress.set();
1915 } else {
1916 _concurrent_strong_root_in_progress.unset();
1917 }
1918 }
1919
1920 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
1921 set_gc_state(WEAK_ROOTS, cond);
1922 }
1923
1924 GCTracer* ShenandoahHeap::tracer() {
1925 return shenandoah_policy()->tracer();
1926 }
1927
1928 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
1929 return _free_set->used();
1930 }
1931
1932 bool ShenandoahHeap::try_cancel_gc() {
1933 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
1934 return prev == CANCELLABLE;
1935 }
1936
1937 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
1938 if (try_cancel_gc()) {
1939 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
1940 log_info(gc)("%s", msg.buffer());
1941 Events::log(Thread::current(), "%s", msg.buffer());
1942 }
1943 }
1944
1945 uint ShenandoahHeap::max_workers() {
1946 return _max_workers;
1947 }
1948
1949 void ShenandoahHeap::stop() {
1950 // The shutdown sequence should be able to terminate when GC is running.
1951
1952 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
1953 _shenandoah_policy->record_shutdown();
1954
1955 // Step 1. Notify control thread that we are in shutdown.
1956 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
1957 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
1958 control_thread()->prepare_for_graceful_shutdown();
1959
1960 // Step 2. Notify GC workers that we are cancelling GC.
1961 cancel_gc(GCCause::_shenandoah_stop_vm);
1962
1963 // Step 3. Wait until GC worker exits normally.
1964 control_thread()->stop();
1965 }
1966
1967 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
1968 if (!unload_classes()) return;
1969 ClassUnloadingContext ctx(_workers->active_workers(),
1970 true /* unregister_nmethods_during_purge */,
1971 false /* lock_nmethod_free_separately */);
1972
1973 // Unload classes and purge SystemDictionary.
1974 {
1975 ShenandoahPhaseTimings::Phase phase = full_gc ?
1976 ShenandoahPhaseTimings::full_gc_purge_class_unload :
1977 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
1978 ShenandoahIsAliveSelector is_alive;
1979 {
1980 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
1981 ShenandoahGCPhase gc_phase(phase);
1982 ShenandoahGCWorkerPhase worker_phase(phase);
1983 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
1984
1985 uint num_workers = _workers->active_workers();
1986 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
1987 _workers->run_task(&unlink_task);
1988 }
1989 // Release unloaded nmethods's memory.
1990 ClassUnloadingContext::context()->purge_and_free_nmethods();
1991 }
1992
1993 {
1994 ShenandoahGCPhase phase(full_gc ?
1995 ShenandoahPhaseTimings::full_gc_purge_cldg :
1996 ShenandoahPhaseTimings::degen_gc_purge_cldg);
1997 ClassLoaderDataGraph::purge(true /* at_safepoint */);
1998 }
1999 // Resize and verify metaspace
2000 MetaspaceGC::compute_new_size();
2001 DEBUG_ONLY(MetaspaceUtils::verify();)
2002 }
2003
2004 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
2005 // so they should not have forwarded oops.
2006 // However, we do need to "null" dead oops in the roots, if can not be done
2007 // in concurrent cycles.
2008 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2009 uint num_workers = _workers->active_workers();
2010 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2011 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2012 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2013 ShenandoahGCPhase phase(timing_phase);
2014 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2015 // Cleanup weak roots
2016 if (has_forwarded_objects()) {
2017 ShenandoahForwardedIsAliveClosure is_alive;
2018 ShenandoahUpdateRefsClosure keep_alive;
2019 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
2020 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2021 _workers->run_task(&cleaning_task);
2022 } else {
2023 ShenandoahIsAliveClosure is_alive;
2024 #ifdef ASSERT
2025 ShenandoahAssertNotForwardedClosure verify_cl;
2026 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2027 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2028 #else
2029 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2030 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2031 #endif
2032 _workers->run_task(&cleaning_task);
2033 }
2034 }
2035
2036 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2037 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2038 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2039 ShenandoahGCPhase phase(full_gc ?
2040 ShenandoahPhaseTimings::full_gc_purge :
2041 ShenandoahPhaseTimings::degen_gc_purge);
2042 stw_weak_refs(full_gc);
2043 stw_process_weak_roots(full_gc);
2044 stw_unload_classes(full_gc);
2045 }
2046
2047 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2048 set_gc_state(HAS_FORWARDED, cond);
2049 }
2050
2051 void ShenandoahHeap::set_unload_classes(bool uc) {
2052 _unload_classes.set_cond(uc);
2053 }
2054
2055 bool ShenandoahHeap::unload_classes() const {
2056 return _unload_classes.is_set();
2057 }
2058
2059 address ShenandoahHeap::in_cset_fast_test_addr() {
2060 ShenandoahHeap* heap = ShenandoahHeap::heap();
2061 assert(heap->collection_set() != nullptr, "Sanity");
2062 return (address) heap->collection_set()->biased_map_address();
2063 }
2064
2065 size_t ShenandoahHeap::bytes_allocated_since_gc_start() const {
2066 return Atomic::load(&_bytes_allocated_since_gc_start);
2067 }
2068
2069 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2070 Atomic::store(&_bytes_allocated_since_gc_start, (size_t)0);
2071 }
2072
2073 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2074 _degenerated_gc_in_progress.set_cond(in_progress);
2075 }
2076
2077 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2078 _full_gc_in_progress.set_cond(in_progress);
2079 }
2080
2081 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2082 assert (is_full_gc_in_progress(), "should be");
2083 _full_gc_move_in_progress.set_cond(in_progress);
2084 }
2085
2086 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2087 set_gc_state(UPDATEREFS, in_progress);
2088 }
2089
2090 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2091 ShenandoahCodeRoots::register_nmethod(nm);
2092 }
2093
2094 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2095 ShenandoahCodeRoots::unregister_nmethod(nm);
2096 }
2097
2098 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2099 heap_region_containing(o)->record_pin();
2100 }
2101
2102 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2103 ShenandoahHeapRegion* r = heap_region_containing(o);
2104 assert(r != nullptr, "Sanity");
2105 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
2106 r->record_unpin();
2107 }
2108
2109 void ShenandoahHeap::sync_pinned_region_status() {
2110 ShenandoahHeapLocker locker(lock());
2111
2112 for (size_t i = 0; i < num_regions(); i++) {
2113 ShenandoahHeapRegion *r = get_region(i);
2114 if (r->is_active()) {
2115 if (r->is_pinned()) {
2116 if (r->pin_count() == 0) {
2117 r->make_unpinned();
2118 }
2119 } else {
2120 if (r->pin_count() > 0) {
2121 r->make_pinned();
2122 }
2123 }
2124 }
2125 }
2126
2127 assert_pinned_region_status();
2128 }
2129
2130 #ifdef ASSERT
2131 void ShenandoahHeap::assert_pinned_region_status() {
2132 for (size_t i = 0; i < num_regions(); i++) {
2133 ShenandoahHeapRegion* r = get_region(i);
2134 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2135 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2136 }
2137 }
2138 #endif
2139
2140 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2141 return _gc_timer;
2142 }
2143
2144 void ShenandoahHeap::prepare_concurrent_roots() {
2145 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2146 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2147 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2148 set_concurrent_weak_root_in_progress(true);
2149 if (unload_classes()) {
2150 _unloader.prepare();
2151 }
2152 }
2153
2154 void ShenandoahHeap::finish_concurrent_roots() {
2155 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2156 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2157 if (unload_classes()) {
2158 _unloader.finish();
2159 }
2160 }
2161
2162 #ifdef ASSERT
2163 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2164 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2165
2166 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2167 // Use ParallelGCThreads inside safepoints
2168 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2169 ParallelGCThreads, nworkers);
2170 } else {
2171 // Use ConcGCThreads outside safepoints
2172 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2173 ConcGCThreads, nworkers);
2174 }
2175 }
2176 #endif
2177
2178 ShenandoahVerifier* ShenandoahHeap::verifier() {
2179 guarantee(ShenandoahVerify, "Should be enabled");
2180 assert (_verifier != nullptr, "sanity");
2181 return _verifier;
2182 }
2183
2184 template<bool CONCURRENT>
2185 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2186 private:
2187 ShenandoahHeap* _heap;
2188 ShenandoahRegionIterator* _regions;
2189 public:
2190 ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2191 WorkerTask("Shenandoah Update References"),
2192 _heap(ShenandoahHeap::heap()),
2193 _regions(regions) {
2194 }
2195
2196 void work(uint worker_id) {
2197 if (CONCURRENT) {
2198 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2199 ShenandoahSuspendibleThreadSetJoiner stsj;
2200 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2201 } else {
2202 ShenandoahParallelWorkerSession worker_session(worker_id);
2203 do_work<ShenandoahSTWUpdateRefsClosure>(worker_id);
2204 }
2205 }
2206
2207 private:
2208 template<class T>
2209 void do_work(uint worker_id) {
2210 T cl;
2211 if (CONCURRENT && (worker_id == 0)) {
2212 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2213 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2214 size_t cset_regions = _heap->collection_set()->count();
2215 // We cannot transfer any more regions than will be reclaimed when the existing collection set is recycled because
2216 // we need the reclaimed collection set regions to replenish the collector reserves
2217 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2218 }
2219 // If !CONCURRENT, there's no value in expanding Mutator free set
2220
2221 ShenandoahHeapRegion* r = _regions->next();
2222 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
2223 while (r != nullptr) {
2224 HeapWord* update_watermark = r->get_update_watermark();
2225 assert (update_watermark >= r->bottom(), "sanity");
2226 if (r->is_active() && !r->is_cset()) {
2227 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2228 }
2229 if (ShenandoahPacing) {
2230 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2231 }
2232 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2233 return;
2234 }
2235 r = _regions->next();
2236 }
2237 }
2238 };
2239
2240 void ShenandoahHeap::update_heap_references(bool concurrent) {
2241 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2242
2243 if (concurrent) {
2244 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2245 workers()->run_task(&task);
2246 } else {
2247 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2248 workers()->run_task(&task);
2249 }
2250 }
2251
2252
2253 class ShenandoahFinalUpdateRefsUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
2254 private:
2255 ShenandoahHeapLock* const _lock;
2256
2257 public:
2258 ShenandoahFinalUpdateRefsUpdateRegionStateClosure() : _lock(ShenandoahHeap::heap()->lock()) {}
2259
2260 void heap_region_do(ShenandoahHeapRegion* r) {
2261 // Drop unnecessary "pinned" state from regions that does not have CP marks
2262 // anymore, as this would allow trashing them.
2263
2264 if (r->is_active()) {
2265 if (r->is_pinned()) {
2266 if (r->pin_count() == 0) {
2267 ShenandoahHeapLocker locker(_lock);
2268 r->make_unpinned();
2269 }
2270 } else {
2271 if (r->pin_count() > 0) {
2272 ShenandoahHeapLocker locker(_lock);
2273 r->make_pinned();
2274 }
2275 }
2276 }
2277 }
2278
2279 bool is_thread_safe() { return true; }
2280 };
2281
2282 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2283 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2284 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2285
2286 {
2287 ShenandoahGCPhase phase(concurrent ?
2288 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2289 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2290 ShenandoahFinalUpdateRefsUpdateRegionStateClosure cl;
2291 parallel_heap_region_iterate(&cl);
2292
2293 assert_pinned_region_status();
2294 }
2295
2296 {
2297 ShenandoahGCPhase phase(concurrent ?
2298 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2299 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2300 trash_cset_regions();
2301 }
2302 }
2303
2304 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2305 {
2306 ShenandoahGCPhase phase(concurrent ?
2307 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2308 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2309 ShenandoahHeapLocker locker(lock());
2310 _free_set->rebuild();
2311 }
2312 }
2313
2314 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2315 print_on(st);
2316 st->cr();
2317 print_heap_regions_on(st);
2318 }
2319
2320 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2321 size_t slice = r->index() / _bitmap_regions_per_slice;
2322
2323 size_t regions_from = _bitmap_regions_per_slice * slice;
2324 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2325 for (size_t g = regions_from; g < regions_to; g++) {
2326 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2327 if (skip_self && g == r->index()) continue;
2328 if (get_region(g)->is_committed()) {
2329 return true;
2330 }
2331 }
2332 return false;
2333 }
2334
2335 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2336 shenandoah_assert_heaplocked();
2337
2338 // Bitmaps in special regions do not need commits
2339 if (_bitmap_region_special) {
2340 return true;
2341 }
2342
2343 if (is_bitmap_slice_committed(r, true)) {
2344 // Some other region from the group is already committed, meaning the bitmap
2345 // slice is already committed, we exit right away.
2346 return true;
2347 }
2348
2349 // Commit the bitmap slice:
2350 size_t slice = r->index() / _bitmap_regions_per_slice;
2351 size_t off = _bitmap_bytes_per_slice * slice;
2352 size_t len = _bitmap_bytes_per_slice;
2353 char* start = (char*) _bitmap_region.start() + off;
2354
2355 if (!os::commit_memory(start, len, false)) {
2356 return false;
2357 }
2358
2359 if (AlwaysPreTouch) {
2360 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2361 }
2362
2363 return true;
2364 }
2365
2366 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2367 shenandoah_assert_heaplocked();
2368
2369 // Bitmaps in special regions do not need uncommits
2370 if (_bitmap_region_special) {
2371 return true;
2372 }
2373
2374 if (is_bitmap_slice_committed(r, true)) {
2375 // Some other region from the group is still committed, meaning the bitmap
2376 // slice is should stay committed, exit right away.
2377 return true;
2378 }
2379
2380 // Uncommit the bitmap slice:
2381 size_t slice = r->index() / _bitmap_regions_per_slice;
2382 size_t off = _bitmap_bytes_per_slice * slice;
2383 size_t len = _bitmap_bytes_per_slice;
2384 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2385 return false;
2386 }
2387 return true;
2388 }
2389
2390 void ShenandoahHeap::safepoint_synchronize_begin() {
2391 StackWatermarkSet::safepoint_synchronize_begin();
2392 SuspendibleThreadSet::synchronize();
2393 }
2394
2395 void ShenandoahHeap::safepoint_synchronize_end() {
2396 SuspendibleThreadSet::desynchronize();
2397 }
2398
2399 void ShenandoahHeap::try_inject_alloc_failure() {
2400 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2401 _inject_alloc_failure.set();
2402 os::naked_short_sleep(1);
2403 if (cancelled_gc()) {
2404 log_info(gc)("Allocation failure was successfully injected");
2405 }
2406 }
2407 }
2408
2409 bool ShenandoahHeap::should_inject_alloc_failure() {
2410 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2411 }
2412
2413 void ShenandoahHeap::initialize_serviceability() {
2414 _memory_pool = new ShenandoahMemoryPool(this);
2415 _cycle_memory_manager.add_pool(_memory_pool);
2416 _stw_memory_manager.add_pool(_memory_pool);
2417 }
2418
2419 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2420 GrowableArray<GCMemoryManager*> memory_managers(2);
2421 memory_managers.append(&_cycle_memory_manager);
2422 memory_managers.append(&_stw_memory_manager);
2423 return memory_managers;
2424 }
2425
2426 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2427 GrowableArray<MemoryPool*> memory_pools(1);
2428 memory_pools.append(_memory_pool);
2429 return memory_pools;
2430 }
2431
2432 MemoryUsage ShenandoahHeap::memory_usage() {
2433 return _memory_pool->get_memory_usage();
2434 }
2435
2436 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2437 _heap(ShenandoahHeap::heap()),
2438 _index(0) {}
2439
2440 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2441 _heap(heap),
2442 _index(0) {}
2443
2444 void ShenandoahRegionIterator::reset() {
2445 _index = 0;
2446 }
2447
2448 bool ShenandoahRegionIterator::has_next() const {
2449 return _index < _heap->num_regions();
2450 }
2451
2452 char ShenandoahHeap::gc_state() const {
2453 return _gc_state.raw_value();
2454 }
2455
2456 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2457 #ifdef ASSERT
2458 assert(_liveness_cache != nullptr, "sanity");
2459 assert(worker_id < _max_workers, "sanity");
2460 for (uint i = 0; i < num_regions(); i++) {
2461 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2462 }
2463 #endif
2464 return _liveness_cache[worker_id];
2465 }
2466
2467 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2468 assert(worker_id < _max_workers, "sanity");
2469 assert(_liveness_cache != nullptr, "sanity");
2470 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2471 for (uint i = 0; i < num_regions(); i++) {
2472 ShenandoahLiveData live = ld[i];
2473 if (live > 0) {
2474 ShenandoahHeapRegion* r = get_region(i);
2475 r->increase_live_data_gc_words(live);
2476 ld[i] = 0;
2477 }
2478 }
2479 }
2480
2481 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2482 if (is_idle()) return false;
2483
2484 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2485 // marking phase.
2486 if (is_concurrent_mark_in_progress() &&
2487 !marking_context()->allocated_after_mark_start(obj)) {
2488 return true;
2489 }
2490
2491 // Can not guarantee obj is deeply good.
2492 if (has_forwarded_objects()) {
2493 return true;
2494 }
2495
2496 return false;
2497 }