1 /*
2 * Copyright (c) 2023, 2024, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
4 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
5 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 *
7 * This code is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 only, as
9 * published by the Free Software Foundation.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27 #include "precompiled.hpp"
28 #include "memory/allocation.hpp"
29 #include "memory/universe.hpp"
30
31 #include "gc/shared/classUnloadingContext.hpp"
32 #include "gc/shared/gcArguments.hpp"
33 #include "gc/shared/gcTimer.hpp"
34 #include "gc/shared/gcTraceTime.inline.hpp"
35 #include "gc/shared/locationPrinter.inline.hpp"
36 #include "gc/shared/memAllocator.hpp"
37 #include "gc/shared/plab.hpp"
38 #include "gc/shared/tlab_globals.hpp"
39
40 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
41 #include "gc/shenandoah/heuristics/shenandoahYoungHeuristics.hpp"
42 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
43 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
44 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
45 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
46 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
47 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
48 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
49 #include "gc/shenandoah/shenandoahControlThread.hpp"
50 #include "gc/shenandoah/shenandoahFreeSet.hpp"
51 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp"
52 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
53 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
54 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
55 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
56 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
57 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
58 #include "gc/shenandoah/shenandoahInitLogger.hpp"
59 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
60 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
61 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
62 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
63 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
64 #include "gc/shenandoah/shenandoahPacer.inline.hpp"
65 #include "gc/shenandoah/shenandoahPadding.hpp"
66 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp"
67 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
68 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
69 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
70 #include "gc/shenandoah/shenandoahSTWMark.hpp"
71 #include "gc/shenandoah/shenandoahUtils.hpp"
72 #include "gc/shenandoah/shenandoahVerifier.hpp"
73 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
74 #include "gc/shenandoah/shenandoahVMOperations.hpp"
75 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
76 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
77 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
78 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
79 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp"
80 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp"
81 #include "utilities/globalDefinitions.hpp"
82
83 #if INCLUDE_JFR
84 #include "gc/shenandoah/shenandoahJfrSupport.hpp"
85 #endif
86
87 #include "cds/archiveHeapWriter.hpp"
88 #include "classfile/systemDictionary.hpp"
89 #include "code/codeCache.hpp"
90 #include "memory/classLoaderMetaspace.hpp"
91 #include "memory/metaspaceUtils.hpp"
92 #include "nmt/mallocTracker.hpp"
93 #include "nmt/memTracker.hpp"
94 #include "oops/compressedOops.inline.hpp"
95 #include "prims/jvmtiTagMap.hpp"
96 #include "runtime/atomic.hpp"
97 #include "runtime/globals.hpp"
98 #include "runtime/interfaceSupport.inline.hpp"
99 #include "runtime/java.hpp"
100 #include "runtime/orderAccess.hpp"
101 #include "runtime/safepointMechanism.hpp"
102 #include "runtime/stackWatermarkSet.hpp"
103 #include "runtime/vmThread.hpp"
104 #include "utilities/events.hpp"
105 #include "utilities/powerOfTwo.hpp"
106
107 class ShenandoahPretouchHeapTask : public WorkerTask {
108 private:
109 ShenandoahRegionIterator _regions;
110 const size_t _page_size;
111 public:
112 ShenandoahPretouchHeapTask(size_t page_size) :
113 WorkerTask("Shenandoah Pretouch Heap"),
114 _page_size(page_size) {}
115
116 virtual void work(uint worker_id) {
117 ShenandoahHeapRegion* r = _regions.next();
118 while (r != nullptr) {
119 if (r->is_committed()) {
120 os::pretouch_memory(r->bottom(), r->end(), _page_size);
121 }
122 r = _regions.next();
123 }
124 }
125 };
126
127 class ShenandoahPretouchBitmapTask : public WorkerTask {
128 private:
129 ShenandoahRegionIterator _regions;
130 char* _bitmap_base;
131 const size_t _bitmap_size;
132 const size_t _page_size;
133 public:
134 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) :
135 WorkerTask("Shenandoah Pretouch Bitmap"),
136 _bitmap_base(bitmap_base),
137 _bitmap_size(bitmap_size),
138 _page_size(page_size) {}
139
140 virtual void work(uint worker_id) {
141 ShenandoahHeapRegion* r = _regions.next();
142 while (r != nullptr) {
143 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
144 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor();
145 assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
146
147 if (r->is_committed()) {
148 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
149 }
150
151 r = _regions.next();
152 }
153 }
154 };
155
156 jint ShenandoahHeap::initialize() {
157 //
158 // Figure out heap sizing
159 //
160
161 size_t init_byte_size = InitialHeapSize;
162 size_t min_byte_size = MinHeapSize;
163 size_t max_byte_size = MaxHeapSize;
164 size_t heap_alignment = HeapAlignment;
165
166 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes();
167
168 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap");
169 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap");
170
171 _num_regions = ShenandoahHeapRegion::region_count();
172 assert(_num_regions == (max_byte_size / reg_size_bytes),
173 "Regions should cover entire heap exactly: " SIZE_FORMAT " != " SIZE_FORMAT "/" SIZE_FORMAT,
174 _num_regions, max_byte_size, reg_size_bytes);
175
176 size_t num_committed_regions = init_byte_size / reg_size_bytes;
177 num_committed_regions = MIN2(num_committed_regions, _num_regions);
178 assert(num_committed_regions <= _num_regions, "sanity");
179 _initial_size = num_committed_regions * reg_size_bytes;
180
181 size_t num_min_regions = min_byte_size / reg_size_bytes;
182 num_min_regions = MIN2(num_min_regions, _num_regions);
183 assert(num_min_regions <= _num_regions, "sanity");
184 _minimum_size = num_min_regions * reg_size_bytes;
185
186 // Default to max heap size.
187 _soft_max_size = _num_regions * reg_size_bytes;
188
189 _committed = _initial_size;
190
191 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
192 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
193 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
194
195 //
196 // Reserve and commit memory for heap
197 //
198
199 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment);
200 initialize_reserved_region(heap_rs);
201 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize);
202 _heap_region_special = heap_rs.special();
203
204 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0,
205 "Misaligned heap: " PTR_FORMAT, p2i(base()));
206 os::trace_page_sizes_for_requested_size("Heap",
207 max_byte_size, heap_alignment,
208 heap_rs.base(),
209 heap_rs.size(), heap_rs.page_size());
210
211 #if SHENANDOAH_OPTIMIZED_MARKTASK
212 // The optimized ShenandoahMarkTask takes some bits away from the full object bits.
213 // Fail if we ever attempt to address more than we can.
214 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) {
215 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n"
216 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n"
217 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).",
218 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable());
219 vm_exit_during_initialization("Fatal Error", buf);
220 }
221 #endif
222
223 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size);
224 if (!_heap_region_special) {
225 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false,
226 "Cannot commit heap memory");
227 }
228
229 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region));
230
231 // Now we know the number of regions and heap sizes, initialize the heuristics.
232 initialize_heuristics();
233
234 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table");
235
236 //
237 // Worker threads must be initialized after the barrier is configured
238 //
239 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers);
240 if (_workers == nullptr) {
241 vm_exit_during_initialization("Failed necessary allocation.");
242 } else {
243 _workers->initialize_workers();
244 }
245
246 if (ParallelGCThreads > 1) {
247 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads);
248 _safepoint_workers->initialize_workers();
249 }
250
251 //
252 // Reserve and commit memory for bitmap(s)
253 //
254
255 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size());
256 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size);
257
258 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor();
259
260 guarantee(bitmap_bytes_per_region != 0,
261 "Bitmap bytes per region should not be zero");
262 guarantee(is_power_of_2(bitmap_bytes_per_region),
263 "Bitmap bytes per region should be power of two: " SIZE_FORMAT, bitmap_bytes_per_region);
264
265 if (bitmap_page_size > bitmap_bytes_per_region) {
266 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region;
267 _bitmap_bytes_per_slice = bitmap_page_size;
268 } else {
269 _bitmap_regions_per_slice = 1;
270 _bitmap_bytes_per_slice = bitmap_bytes_per_region;
271 }
272
273 guarantee(_bitmap_regions_per_slice >= 1,
274 "Should have at least one region per slice: " SIZE_FORMAT,
275 _bitmap_regions_per_slice);
276
277 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0,
278 "Bitmap slices should be page-granular: bps = " SIZE_FORMAT ", page size = " SIZE_FORMAT,
279 _bitmap_bytes_per_slice, bitmap_page_size);
280
281 ReservedSpace bitmap(_bitmap_size, bitmap_page_size);
282 os::trace_page_sizes_for_requested_size("Mark Bitmap",
283 bitmap_size_orig, bitmap_page_size,
284 bitmap.base(),
285 bitmap.size(), bitmap.page_size());
286 MemTracker::record_virtual_memory_type(bitmap.base(), mtGC);
287 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize);
288 _bitmap_region_special = bitmap.special();
289
290 size_t bitmap_init_commit = _bitmap_bytes_per_slice *
291 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice;
292 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit);
293 if (!_bitmap_region_special) {
294 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false,
295 "Cannot commit bitmap memory");
296 }
297
298 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions);
299
300 if (ShenandoahVerify) {
301 ReservedSpace verify_bitmap(_bitmap_size, bitmap_page_size);
302 os::trace_page_sizes_for_requested_size("Verify Bitmap",
303 bitmap_size_orig, bitmap_page_size,
304 verify_bitmap.base(),
305 verify_bitmap.size(), verify_bitmap.page_size());
306 if (!verify_bitmap.special()) {
307 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false,
308 "Cannot commit verification bitmap memory");
309 }
310 MemTracker::record_virtual_memory_type(verify_bitmap.base(), mtGC);
311 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize);
312 _verification_bit_map.initialize(_heap_region, verify_bitmap_region);
313 _verifier = new ShenandoahVerifier(this, &_verification_bit_map);
314 }
315
316 // Reserve aux bitmap for use in object_iterate(). We don't commit it here.
317 size_t aux_bitmap_page_size = bitmap_page_size;
318
319 ReservedSpace aux_bitmap(_bitmap_size, aux_bitmap_page_size);
320 os::trace_page_sizes_for_requested_size("Aux Bitmap",
321 bitmap_size_orig, aux_bitmap_page_size,
322 aux_bitmap.base(),
323 aux_bitmap.size(), aux_bitmap.page_size());
324 MemTracker::record_virtual_memory_type(aux_bitmap.base(), mtGC);
325 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize);
326 _aux_bitmap_region_special = aux_bitmap.special();
327 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region);
328
329 //
330 // Create regions and region sets
331 //
332 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
333 size_t region_storage_size_orig = region_align * _num_regions;
334 size_t region_storage_size = align_up(region_storage_size_orig,
335 MAX2(region_page_size, os::vm_allocation_granularity()));
336
337 ReservedSpace region_storage(region_storage_size, region_page_size);
338 os::trace_page_sizes_for_requested_size("Region Storage",
339 region_storage_size_orig, region_page_size,
340 region_storage.base(),
341 region_storage.size(), region_storage.page_size());
342 MemTracker::record_virtual_memory_type(region_storage.base(), mtGC);
343 if (!region_storage.special()) {
344 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false,
345 "Cannot commit region memory");
346 }
347
348 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks.
349 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there.
350 // If not successful, bite a bullet and allocate at whatever address.
351 {
352 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity());
353 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align);
354 const size_t cset_page_size = os::vm_page_size();
355
356 uintptr_t min = round_up_power_of_2(cset_align);
357 uintptr_t max = (1u << 30u);
358 ReservedSpace cset_rs;
359
360 for (uintptr_t addr = min; addr <= max; addr <<= 1u) {
361 char* req_addr = (char*)addr;
362 assert(is_aligned(req_addr, cset_align), "Should be aligned");
363 cset_rs = ReservedSpace(cset_size, cset_align, cset_page_size, req_addr);
364 if (cset_rs.is_reserved()) {
365 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr);
366 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
367 break;
368 }
369 }
370
371 if (_collection_set == nullptr) {
372 cset_rs = ReservedSpace(cset_size, cset_align, os::vm_page_size());
373 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base());
374 }
375 os::trace_page_sizes_for_requested_size("Collection Set",
376 cset_size, cset_page_size,
377 cset_rs.base(),
378 cset_rs.size(), cset_rs.page_size());
379 }
380
381 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC);
382 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC);
383 _free_set = new ShenandoahFreeSet(this, _num_regions);
384
385 {
386 ShenandoahHeapLocker locker(lock());
387
388 for (size_t i = 0; i < _num_regions; i++) {
389 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i;
390 bool is_committed = i < num_committed_regions;
391 void* loc = region_storage.base() + i * region_align;
392
393 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed);
394 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity");
395
396 _marking_context->initialize_top_at_mark_start(r);
397 _regions[i] = r;
398 assert(!collection_set()->is_in(i), "New region should not be in collection set");
399
400 _affiliations[i] = ShenandoahAffiliation::FREE;
401 }
402
403 // Initialize to complete
404 _marking_context->mark_complete();
405 size_t young_cset_regions, old_cset_regions;
406
407 // We are initializing free set. We ignore cset region tallies.
408 size_t first_old, last_old, num_old;
409 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old, last_old, num_old);
410 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, num_old);
411 }
412
413 if (AlwaysPreTouch) {
414 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads,
415 // before initialize() below zeroes it with initializing thread. For any given region,
416 // we touch the region and the corresponding bitmaps from the same thread.
417 ShenandoahPushWorkerScope scope(workers(), _max_workers, false);
418
419 _pretouch_heap_page_size = heap_page_size;
420 _pretouch_bitmap_page_size = bitmap_page_size;
421
422 // OS memory managers may want to coalesce back-to-back pages. Make their jobs
423 // simpler by pre-touching continuous spaces (heap and bitmap) separately.
424
425 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size);
426 _workers->run_task(&bcl);
427
428 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size);
429 _workers->run_task(&hcl);
430 }
431
432 //
433 // Initialize the rest of GC subsystems
434 //
435
436 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC);
437 for (uint worker = 0; worker < _max_workers; worker++) {
438 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC);
439 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData));
440 }
441
442 // There should probably be Shenandoah-specific options for these,
443 // just as there are G1-specific options.
444 {
445 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set();
446 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold
447 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent
448 }
449
450 _monitoring_support = new ShenandoahMonitoringSupport(this);
451 _phase_timings = new ShenandoahPhaseTimings(max_workers());
452 ShenandoahCodeRoots::initialize();
453
454 if (ShenandoahPacing) {
455 _pacer = new ShenandoahPacer(this);
456 _pacer->setup_for_idle();
457 }
458
459 initialize_controller();
460
461 print_init_logger();
462
463 return JNI_OK;
464 }
465
466 void ShenandoahHeap::initialize_controller() {
467 _control_thread = new ShenandoahControlThread();
468 }
469
470 void ShenandoahHeap::print_init_logger() const {
471 ShenandoahInitLogger::print();
472 }
473
474 void ShenandoahHeap::initialize_mode() {
475 if (ShenandoahGCMode != nullptr) {
476 if (strcmp(ShenandoahGCMode, "satb") == 0) {
477 _gc_mode = new ShenandoahSATBMode();
478 } else if (strcmp(ShenandoahGCMode, "passive") == 0) {
479 _gc_mode = new ShenandoahPassiveMode();
480 } else if (strcmp(ShenandoahGCMode, "generational") == 0) {
481 _gc_mode = new ShenandoahGenerationalMode();
482 } else {
483 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option");
484 }
485 } else {
486 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)");
487 }
488 _gc_mode->initialize_flags();
489 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) {
490 vm_exit_during_initialization(
491 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.",
492 _gc_mode->name()));
493 }
494 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) {
495 vm_exit_during_initialization(
496 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.",
497 _gc_mode->name()));
498 }
499 }
500
501 void ShenandoahHeap::initialize_heuristics() {
502 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers(), max_capacity(), max_capacity());
503 _global_generation->initialize_heuristics(mode());
504 _evac_tracker = new ShenandoahEvacuationTracker(mode()->is_generational());
505 }
506
507 #ifdef _MSC_VER
508 #pragma warning( push )
509 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
510 #endif
511
512 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
513 CollectedHeap(),
514 _gc_generation(nullptr),
515 _active_generation(nullptr),
516 _initial_size(0),
517 _committed(0),
518 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
519 _workers(nullptr),
520 _safepoint_workers(nullptr),
521 _heap_region_special(false),
522 _num_regions(0),
523 _regions(nullptr),
524 _affiliations(nullptr),
525 _gc_state_changed(false),
526 _gc_no_progress_count(0),
527 _cancel_requested_time(0),
528 _update_refs_iterator(this),
529 _global_generation(nullptr),
530 _control_thread(nullptr),
531 _young_generation(nullptr),
532 _old_generation(nullptr),
533 _shenandoah_policy(policy),
534 _gc_mode(nullptr),
535 _free_set(nullptr),
536 _pacer(nullptr),
537 _verifier(nullptr),
538 _phase_timings(nullptr),
539 _evac_tracker(nullptr),
540 _mmu_tracker(),
541 _monitoring_support(nullptr),
542 _memory_pool(nullptr),
543 _stw_memory_manager("Shenandoah Pauses"),
544 _cycle_memory_manager("Shenandoah Cycles"),
545 _gc_timer(new ConcurrentGCTimer()),
546 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes),
547 _marking_context(nullptr),
548 _bitmap_size(0),
549 _bitmap_regions_per_slice(0),
550 _bitmap_bytes_per_slice(0),
551 _bitmap_region_special(false),
552 _aux_bitmap_region_special(false),
553 _liveness_cache(nullptr),
554 _collection_set(nullptr)
555 {
556 // Initialize GC mode early, many subsequent initialization procedures depend on it
557 initialize_mode();
558 }
559
560 #ifdef _MSC_VER
561 #pragma warning( pop )
562 #endif
563
564 void ShenandoahHeap::print_on(outputStream* st) const {
565 st->print_cr("Shenandoah Heap");
566 st->print_cr(" " SIZE_FORMAT "%s max, " SIZE_FORMAT "%s soft max, " SIZE_FORMAT "%s committed, " SIZE_FORMAT "%s used",
567 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()),
568 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()),
569 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()),
570 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
571 st->print_cr(" " SIZE_FORMAT " x " SIZE_FORMAT"%s regions",
572 num_regions(),
573 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()),
574 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes()));
575
576 st->print("Status: ");
577 if (has_forwarded_objects()) st->print("has forwarded objects, ");
578 if (is_concurrent_old_mark_in_progress()) st->print("old marking, ");
579 if (is_concurrent_young_mark_in_progress()) st->print("young marking, ");
580 if (is_evacuation_in_progress()) st->print("evacuating, ");
581 if (is_update_refs_in_progress()) st->print("updating refs, ");
582 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, ");
583 if (is_full_gc_in_progress()) st->print("full gc, ");
584 if (is_full_gc_move_in_progress()) st->print("full gc move, ");
585 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, ");
586 if (is_concurrent_strong_root_in_progress() &&
587 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, ");
588
589 if (cancelled_gc()) {
590 st->print("cancelled");
591 } else {
592 st->print("not cancelled");
593 }
594 st->cr();
595
596 st->print_cr("Reserved region:");
597 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ",
598 p2i(reserved_region().start()),
599 p2i(reserved_region().end()));
600
601 ShenandoahCollectionSet* cset = collection_set();
602 st->print_cr("Collection set:");
603 if (cset != nullptr) {
604 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address()));
605 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address()));
606 } else {
607 st->print_cr(" (null)");
608 }
609
610 st->cr();
611 MetaspaceUtils::print_on(st);
612
613 if (Verbose) {
614 st->cr();
615 print_heap_regions_on(st);
616 }
617 }
618
619 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
620 public:
621 void do_thread(Thread* thread) {
622 assert(thread != nullptr, "Sanity");
623 assert(thread->is_Worker_thread(), "Only worker thread expected");
624 ShenandoahThreadLocalData::initialize_gclab(thread);
625 }
626 };
627
628 void ShenandoahHeap::post_initialize() {
629 CollectedHeap::post_initialize();
630 _mmu_tracker.initialize();
631
632 MutexLocker ml(Threads_lock);
633
634 ShenandoahInitWorkerGCLABClosure init_gclabs;
635 _workers->threads_do(&init_gclabs);
636
637 // gclab can not be initialized early during VM startup, as it can not determinate its max_size.
638 // Now, we will let WorkerThreads to initialize gclab when new worker is created.
639 _workers->set_initialize_gclab();
640 if (_safepoint_workers != nullptr) {
641 _safepoint_workers->threads_do(&init_gclabs);
642 _safepoint_workers->set_initialize_gclab();
643 }
644
645 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();)
646 }
647
648 ShenandoahHeuristics* ShenandoahHeap::heuristics() {
649 return _global_generation->heuristics();
650 }
651
652 size_t ShenandoahHeap::used() const {
653 return global_generation()->used();
654 }
655
656 size_t ShenandoahHeap::committed() const {
657 return Atomic::load(&_committed);
658 }
659
660 void ShenandoahHeap::increase_committed(size_t bytes) {
661 shenandoah_assert_heaplocked_or_safepoint();
662 _committed += bytes;
663 }
664
665 void ShenandoahHeap::decrease_committed(size_t bytes) {
666 shenandoah_assert_heaplocked_or_safepoint();
667 _committed -= bytes;
668 }
669
670 // For tracking usage based on allocations, it should be the case that:
671 // * The sum of regions::used == heap::used
672 // * The sum of a generation's regions::used == generation::used
673 // * The sum of a generation's humongous regions::free == generation::humongous_waste
674 // These invariants are checked by the verifier on GC safepoints.
675 //
676 // Additional notes:
677 // * When a mutator's allocation request causes a region to be retired, the
678 // free memory left in that region is considered waste. It does not contribute
679 // to the usage, but it _does_ contribute to allocation rate.
680 // * The bottom of a PLAB must be aligned on card size. In some cases this will
681 // require padding in front of the PLAB (a filler object). Because this padding
682 // is included in the region's used memory we include the padding in the usage
683 // accounting as waste.
684 // * Mutator allocations are used to compute an allocation rate. They are also
685 // sent to the Pacer for those purposes.
686 // * There are three sources of waste:
687 // 1. The padding used to align a PLAB on card size
688 // 2. Region's free is less than minimum TLAB size and is retired
689 // 3. The unused portion of memory in the last region of a humongous object
690 void ShenandoahHeap::increase_used(const ShenandoahAllocRequest& req) {
691 size_t actual_bytes = req.actual_size() * HeapWordSize;
692 size_t wasted_bytes = req.waste() * HeapWordSize;
693 ShenandoahGeneration* generation = generation_for(req.affiliation());
694
695 if (req.is_gc_alloc()) {
696 assert(wasted_bytes == 0 || req.type() == ShenandoahAllocRequest::_alloc_plab, "Only PLABs have waste");
697 increase_used(generation, actual_bytes + wasted_bytes);
698 } else {
699 assert(req.is_mutator_alloc(), "Expected mutator alloc here");
700 // padding and actual size both count towards allocation counter
701 generation->increase_allocated(actual_bytes + wasted_bytes);
702
703 // only actual size counts toward usage for mutator allocations
704 increase_used(generation, actual_bytes);
705
706 // notify pacer of both actual size and waste
707 notify_mutator_alloc_words(req.actual_size(), req.waste());
708
709 if (wasted_bytes > 0 && ShenandoahHeapRegion::requires_humongous(req.actual_size())) {
710 increase_humongous_waste(generation,wasted_bytes);
711 }
712 }
713 }
714
715 void ShenandoahHeap::increase_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
716 generation->increase_humongous_waste(bytes);
717 if (!generation->is_global()) {
718 global_generation()->increase_humongous_waste(bytes);
719 }
720 }
721
722 void ShenandoahHeap::decrease_humongous_waste(ShenandoahGeneration* generation, size_t bytes) {
723 generation->decrease_humongous_waste(bytes);
724 if (!generation->is_global()) {
725 global_generation()->decrease_humongous_waste(bytes);
726 }
727 }
728
729 void ShenandoahHeap::increase_used(ShenandoahGeneration* generation, size_t bytes) {
730 generation->increase_used(bytes);
731 if (!generation->is_global()) {
732 global_generation()->increase_used(bytes);
733 }
734 }
735
736 void ShenandoahHeap::decrease_used(ShenandoahGeneration* generation, size_t bytes) {
737 generation->decrease_used(bytes);
738 if (!generation->is_global()) {
739 global_generation()->decrease_used(bytes);
740 }
741 }
742
743 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, size_t waste) {
744 if (ShenandoahPacing) {
745 control_thread()->pacing_notify_alloc(words);
746 if (waste > 0) {
747 pacer()->claim_for_alloc(waste, true);
748 }
749 }
750 }
751
752 size_t ShenandoahHeap::capacity() const {
753 return committed();
754 }
755
756 size_t ShenandoahHeap::max_capacity() const {
757 return _num_regions * ShenandoahHeapRegion::region_size_bytes();
758 }
759
760 size_t ShenandoahHeap::soft_max_capacity() const {
761 size_t v = Atomic::load(&_soft_max_size);
762 assert(min_capacity() <= v && v <= max_capacity(),
763 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
764 min_capacity(), v, max_capacity());
765 return v;
766 }
767
768 void ShenandoahHeap::set_soft_max_capacity(size_t v) {
769 assert(min_capacity() <= v && v <= max_capacity(),
770 "Should be in bounds: " SIZE_FORMAT " <= " SIZE_FORMAT " <= " SIZE_FORMAT,
771 min_capacity(), v, max_capacity());
772 Atomic::store(&_soft_max_size, v);
773 }
774
775 size_t ShenandoahHeap::min_capacity() const {
776 return _minimum_size;
777 }
778
779 size_t ShenandoahHeap::initial_capacity() const {
780 return _initial_size;
781 }
782
783 bool ShenandoahHeap::is_in(const void* p) const {
784 if (is_in_reserved(p)) {
785 if (is_full_gc_move_in_progress()) {
786 // Full GC move is running, we do not have a consistent region
787 // information yet. But we know the pointer is in heap.
788 return true;
789 }
790 // Now check if we point to a live section in active region.
791 ShenandoahHeapRegion* r = heap_region_containing(p);
792 return (r->is_active() && p < r->top());
793 } else {
794 return false;
795 }
796 }
797
798 void ShenandoahHeap::maybe_uncommit(double shrink_before, size_t shrink_until) {
799 assert (ShenandoahUncommit, "should be enabled");
800
801 // Determine if there is work to do. This avoids taking heap lock if there is
802 // no work available, avoids spamming logs with superfluous logging messages,
803 // and minimises the amount of work while locks are taken.
804
805 if (committed() <= shrink_until) return;
806
807 bool has_work = false;
808 for (size_t i = 0; i < num_regions(); i++) {
809 ShenandoahHeapRegion* r = get_region(i);
810 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
811 has_work = true;
812 break;
813 }
814 }
815
816 if (has_work) {
817 static const char* msg = "Concurrent uncommit";
818 ShenandoahConcurrentPhase gcPhase(msg, ShenandoahPhaseTimings::conc_uncommit, true /* log_heap_usage */);
819 EventMark em("%s", msg);
820
821 op_uncommit(shrink_before, shrink_until);
822 }
823 }
824
825 void ShenandoahHeap::op_uncommit(double shrink_before, size_t shrink_until) {
826 assert (ShenandoahUncommit, "should be enabled");
827
828 // Application allocates from the beginning of the heap, and GC allocates at
829 // the end of it. It is more efficient to uncommit from the end, so that applications
830 // could enjoy the near committed regions. GC allocations are much less frequent,
831 // and therefore can accept the committing costs.
832
833 size_t count = 0;
834 for (size_t i = num_regions(); i > 0; i--) { // care about size_t underflow
835 ShenandoahHeapRegion* r = get_region(i - 1);
836 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
837 ShenandoahHeapLocker locker(lock());
838 if (r->is_empty_committed()) {
839 if (committed() < shrink_until + ShenandoahHeapRegion::region_size_bytes()) {
840 break;
841 }
842
843 r->make_uncommitted();
844 count++;
845 }
846 }
847 SpinPause(); // allow allocators to take the lock
848 }
849
850 if (count > 0) {
851 notify_heap_changed();
852 }
853 }
854
855 bool ShenandoahHeap::check_soft_max_changed() {
856 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
857 size_t old_soft_max = soft_max_capacity();
858 if (new_soft_max != old_soft_max) {
859 new_soft_max = MAX2(min_capacity(), new_soft_max);
860 new_soft_max = MIN2(max_capacity(), new_soft_max);
861 if (new_soft_max != old_soft_max) {
862 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
863 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
864 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
865 );
866 set_soft_max_capacity(new_soft_max);
867 return true;
868 }
869 }
870 return false;
871 }
872
873 void ShenandoahHeap::notify_heap_changed() {
874 // Update monitoring counters when we took a new region. This amortizes the
875 // update costs on slow path.
876 monitoring_support()->notify_heap_changed();
877 _heap_changed.set();
878 }
879
880 void ShenandoahHeap::set_forced_counters_update(bool value) {
881 monitoring_support()->set_forced_counters_update(value);
882 }
883
884 void ShenandoahHeap::handle_force_counters_update() {
885 monitoring_support()->handle_force_counters_update();
886 }
887
888 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) {
889 // New object should fit the GCLAB size
890 size_t min_size = MAX2(size, PLAB::min_size());
891
892 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively.
893 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2;
894
895 new_size = MIN2(new_size, PLAB::max_size());
896 new_size = MAX2(new_size, PLAB::min_size());
897
898 // Record new heuristic value even if we take any shortcut. This captures
899 // the case when moderately-sized objects always take a shortcut. At some point,
900 // heuristics should catch up with them.
901 log_debug(gc, free)("Set new GCLAB size: " SIZE_FORMAT, new_size);
902 ShenandoahThreadLocalData::set_gclab_size(thread, new_size);
903
904 if (new_size < size) {
905 // New size still does not fit the object. Fall back to shared allocation.
906 // This avoids retiring perfectly good GCLABs, when we encounter a large object.
907 log_debug(gc, free)("New gclab size (" SIZE_FORMAT ") is too small for " SIZE_FORMAT, new_size, size);
908 return nullptr;
909 }
910
911 // Retire current GCLAB, and allocate a new one.
912 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
913 gclab->retire();
914
915 size_t actual_size = 0;
916 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size);
917 if (gclab_buf == nullptr) {
918 return nullptr;
919 }
920
921 assert (size <= actual_size, "allocation should fit");
922
923 // ...and clear or zap just allocated TLAB, if needed.
924 if (ZeroTLAB) {
925 Copy::zero_to_words(gclab_buf, actual_size);
926 } else if (ZapTLAB) {
927 // Skip mangling the space corresponding to the object header to
928 // ensure that the returned space is not considered parsable by
929 // any concurrent GC thread.
930 size_t hdr_size = oopDesc::header_size();
931 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal);
932 }
933 gclab->set_buf(gclab_buf, actual_size);
934 return gclab->allocate(size);
935 }
936
937 // Called from stubs in JIT code or interpreter
938 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
939 size_t requested_size,
940 size_t* actual_size) {
941 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size);
942 HeapWord* res = allocate_memory(req);
943 if (res != nullptr) {
944 *actual_size = req.actual_size();
945 } else {
946 *actual_size = 0;
947 }
948 return res;
949 }
950
951 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size,
952 size_t word_size,
953 size_t* actual_size) {
954 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size);
955 HeapWord* res = allocate_memory(req);
956 if (res != nullptr) {
957 *actual_size = req.actual_size();
958 } else {
959 *actual_size = 0;
960 }
961 return res;
962 }
963
964 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) {
965 intptr_t pacer_epoch = 0;
966 bool in_new_region = false;
967 HeapWord* result = nullptr;
968
969 if (req.is_mutator_alloc()) {
970 if (ShenandoahPacing) {
971 pacer()->pace_for_alloc(req.size());
972 pacer_epoch = pacer()->epoch();
973 }
974
975 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) {
976 result = allocate_memory_under_lock(req, in_new_region);
977 }
978
979 // Check that gc overhead is not exceeded.
980 //
981 // Shenandoah will grind along for quite a while allocating one
982 // object at a time using shared (non-tlab) allocations. This check
983 // is testing that the GC overhead limit has not been exceeded.
984 // This will notify the collector to start a cycle, but will raise
985 // an OOME to the mutator if the last Full GCs have not made progress.
986 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress().
987 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) {
988 control_thread()->handle_alloc_failure(req, false);
989 req.set_actual_size(0);
990 return nullptr;
991 }
992
993 if (result == nullptr) {
994 // Block until control thread reacted, then retry allocation.
995 //
996 // It might happen that one of the threads requesting allocation would unblock
997 // way later after GC happened, only to fail the second allocation, because
998 // other threads have already depleted the free storage. In this case, a better
999 // strategy is to try again, until at least one full GC has completed.
1000 //
1001 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after:
1002 // a) We experienced a GC that had good progress, or
1003 // b) We experienced at least one Full GC (whether or not it had good progress)
1004
1005 size_t original_count = shenandoah_policy()->full_gc_count();
1006 while ((result == nullptr) && (original_count == shenandoah_policy()->full_gc_count())) {
1007 control_thread()->handle_alloc_failure(req, true);
1008 result = allocate_memory_under_lock(req, in_new_region);
1009 }
1010 if (result != nullptr) {
1011 // If our allocation request has been satisifed after it initially failed, we count this as good gc progress
1012 notify_gc_progress();
1013 }
1014 if (log_develop_is_enabled(Debug, gc, alloc)) {
1015 ResourceMark rm;
1016 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: " SIZE_FORMAT
1017 ", Original: " SIZE_FORMAT ", Latest: " SIZE_FORMAT,
1018 Thread::current()->name(), p2i(result), req.type_string(), req.size(),
1019 original_count, get_gc_no_progress_count());
1020 }
1021 }
1022 } else {
1023 assert(req.is_gc_alloc(), "Can only accept GC allocs here");
1024 result = allocate_memory_under_lock(req, in_new_region);
1025 // Do not call handle_alloc_failure() here, because we cannot block.
1026 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac().
1027 }
1028
1029 if (in_new_region) {
1030 notify_heap_changed();
1031 }
1032
1033 if (result == nullptr) {
1034 req.set_actual_size(0);
1035 }
1036
1037 // This is called regardless of the outcome of the allocation to account
1038 // for any waste created by retiring regions with this request.
1039 increase_used(req);
1040
1041 if (result != nullptr) {
1042 size_t requested = req.size();
1043 size_t actual = req.actual_size();
1044
1045 assert (req.is_lab_alloc() || (requested == actual),
1046 "Only LAB allocations are elastic: %s, requested = " SIZE_FORMAT ", actual = " SIZE_FORMAT,
1047 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual);
1048
1049 if (req.is_mutator_alloc()) {
1050 // If we requested more than we were granted, give the rest back to pacer.
1051 // This only matters if we are in the same pacing epoch: do not try to unpace
1052 // over the budget for the other phase.
1053 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) {
1054 pacer()->unpace_for_alloc(pacer_epoch, requested - actual);
1055 }
1056 }
1057 }
1058
1059 return result;
1060 }
1061
1062 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) {
1063 // If we are dealing with mutator allocation, then we may need to block for safepoint.
1064 // We cannot block for safepoint for GC allocations, because there is a high chance
1065 // we are already running at safepoint or from stack watermark machinery, and we cannot
1066 // block again.
1067 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc());
1068
1069 // Make sure the old generation has room for either evacuations or promotions before trying to allocate.
1070 if (req.is_old() && !old_generation()->can_allocate(req)) {
1071 return nullptr;
1072 }
1073
1074 // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available
1075 // memory.
1076 HeapWord* result = _free_set->allocate(req, in_new_region);
1077
1078 // Record the plab configuration for this result and register the object.
1079 if (result != nullptr && req.is_old()) {
1080 old_generation()->configure_plab_for_current_thread(req);
1081 if (req.type() == ShenandoahAllocRequest::_alloc_shared_gc) {
1082 // Register the newly allocated object while we're holding the global lock since there's no synchronization
1083 // built in to the implementation of register_object(). There are potential races when multiple independent
1084 // threads are allocating objects, some of which might span the same card region. For example, consider
1085 // a card table's memory region within which three objects are being allocated by three different threads:
1086 //
1087 // objects being "concurrently" allocated:
1088 // [-----a------][-----b-----][--------------c------------------]
1089 // [---- card table memory range --------------]
1090 //
1091 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a
1092 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region.
1093 // Allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region.
1094 // Allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this
1095 // card region.
1096 //
1097 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as
1098 // last-start representing object b while first-start represents object c. This is why we need to require all
1099 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range.
1100 old_generation()->card_scan()->register_object(result);
1101 }
1102 }
1103
1104 return result;
1105 }
1106
1107 HeapWord* ShenandoahHeap::mem_allocate(size_t size,
1108 bool* gc_overhead_limit_was_exceeded) {
1109 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
1110 return allocate_memory(req);
1111 }
1112
1113 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
1114 size_t size,
1115 Metaspace::MetadataType mdtype) {
1116 MetaWord* result;
1117
1118 // Inform metaspace OOM to GC heuristics if class unloading is possible.
1119 ShenandoahHeuristics* h = global_generation()->heuristics();
1120 if (h->can_unload_classes()) {
1121 h->record_metaspace_oom();
1122 }
1123
1124 // Expand and retry allocation
1125 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1126 if (result != nullptr) {
1127 return result;
1128 }
1129
1130 // Start full GC
1131 collect(GCCause::_metadata_GC_clear_soft_refs);
1132
1133 // Retry allocation
1134 result = loader_data->metaspace_non_null()->allocate(size, mdtype);
1135 if (result != nullptr) {
1136 return result;
1137 }
1138
1139 // Expand and retry allocation
1140 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype);
1141 if (result != nullptr) {
1142 return result;
1143 }
1144
1145 // Out of memory
1146 return nullptr;
1147 }
1148
1149 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure {
1150 private:
1151 ShenandoahHeap* const _heap;
1152 Thread* const _thread;
1153 public:
1154 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) :
1155 _heap(heap), _thread(Thread::current()) {}
1156
1157 void do_object(oop p) {
1158 shenandoah_assert_marked(nullptr, p);
1159 if (!p->is_forwarded()) {
1160 _heap->evacuate_object(p, _thread);
1161 }
1162 }
1163 };
1164
1165 class ShenandoahEvacuationTask : public WorkerTask {
1166 private:
1167 ShenandoahHeap* const _sh;
1168 ShenandoahCollectionSet* const _cs;
1169 bool _concurrent;
1170 public:
1171 ShenandoahEvacuationTask(ShenandoahHeap* sh,
1172 ShenandoahCollectionSet* cs,
1173 bool concurrent) :
1174 WorkerTask("Shenandoah Evacuation"),
1175 _sh(sh),
1176 _cs(cs),
1177 _concurrent(concurrent)
1178 {}
1179
1180 void work(uint worker_id) {
1181 if (_concurrent) {
1182 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1183 ShenandoahSuspendibleThreadSetJoiner stsj;
1184 ShenandoahEvacOOMScope oom_evac_scope;
1185 do_work();
1186 } else {
1187 ShenandoahParallelWorkerSession worker_session(worker_id);
1188 ShenandoahEvacOOMScope oom_evac_scope;
1189 do_work();
1190 }
1191 }
1192
1193 private:
1194 void do_work() {
1195 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh);
1196 ShenandoahHeapRegion* r;
1197 while ((r =_cs->claim_next()) != nullptr) {
1198 assert(r->has_live(), "Region " SIZE_FORMAT " should have been reclaimed early", r->index());
1199 _sh->marked_object_iterate(r, &cl);
1200
1201 if (ShenandoahPacing) {
1202 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize);
1203 }
1204
1205 if (_sh->check_cancelled_gc_and_yield(_concurrent)) {
1206 break;
1207 }
1208 }
1209 }
1210 };
1211
1212 void ShenandoahHeap::evacuate_collection_set(bool concurrent) {
1213 if (mode()->is_generational()) {
1214 ShenandoahRegionIterator regions;
1215 ShenandoahGenerationalEvacuationTask task(ShenandoahGenerationalHeap::heap(), ®ions, concurrent);
1216 workers()->run_task(&task);
1217 } else {
1218 ShenandoahEvacuationTask task(this, _collection_set, concurrent);
1219 workers()->run_task(&task);
1220 }
1221 }
1222
1223 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
1224 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
1225 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
1226 // This thread went through the OOM during evac protocol. It is safe to return
1227 // the forward pointer. It must not attempt to evacuate any other objects.
1228 return ShenandoahBarrierSet::resolve_forwarded(p);
1229 }
1230
1231 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
1232
1233 ShenandoahHeapRegion* r = heap_region_containing(p);
1234 assert(!r->is_humongous(), "never evacuate humongous objects");
1235
1236 ShenandoahAffiliation target_gen = r->affiliation();
1237 return try_evacuate_object(p, thread, r, target_gen);
1238 }
1239
1240 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
1241 ShenandoahAffiliation target_gen) {
1242 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode");
1243 assert(from_region->is_young(), "Only expect evacuations from young in this mode");
1244 bool alloc_from_lab = true;
1245 HeapWord* copy = nullptr;
1246 size_t size = p->size();
1247
1248 #ifdef ASSERT
1249 if (ShenandoahOOMDuringEvacALot &&
1250 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
1251 copy = nullptr;
1252 } else {
1253 #endif
1254 if (UseTLAB) {
1255 copy = allocate_from_gclab(thread, size);
1256 if ((copy == nullptr) && (size < ShenandoahThreadLocalData::gclab_size(thread))) {
1257 // GCLAB allocation failed because we are bumping up against the limit on young evacuation reserve. Try resetting
1258 // the desired GCLAB size and retry GCLAB allocation to avoid cascading of shared memory allocations.
1259 ShenandoahThreadLocalData::set_gclab_size(thread, PLAB::min_size());
1260 copy = allocate_from_gclab(thread, size);
1261 // If we still get nullptr, we'll try a shared allocation below.
1262 }
1263 }
1264
1265 if (copy == nullptr) {
1266 // If we failed to allocate in LAB, we'll try a shared allocation.
1267 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
1268 copy = allocate_memory(req);
1269 alloc_from_lab = false;
1270 }
1271 #ifdef ASSERT
1272 }
1273 #endif
1274
1275 if (copy == nullptr) {
1276 control_thread()->handle_alloc_failure_evac(size);
1277
1278 _oom_evac_handler.handle_out_of_memory_during_evacuation();
1279
1280 return ShenandoahBarrierSet::resolve_forwarded(p);
1281 }
1282
1283 // Copy the object:
1284 _evac_tracker->begin_evacuation(thread, size * HeapWordSize);
1285 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
1286
1287 // Try to install the new forwarding pointer.
1288 oop copy_val = cast_to_oop(copy);
1289 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
1290 if (result == copy_val) {
1291 // Successfully evacuated. Our copy is now the public one!
1292 ContinuationGCSupport::relativize_stack_chunk(copy_val);
1293 _evac_tracker->end_evacuation(thread, size * HeapWordSize);
1294 shenandoah_assert_correct(nullptr, copy_val);
1295 return copy_val;
1296 } else {
1297 // Failed to evacuate. We need to deal with the object that is left behind. Since this
1298 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
1299 // But if it happens to contain references to evacuated regions, those references would
1300 // not get updated for this stale copy during this cycle, and we will crash while scanning
1301 // it the next cycle.
1302 if (alloc_from_lab) {
1303 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
1304 // object will overwrite this stale copy, or the filler object on LAB retirement will
1305 // do this.
1306 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
1307 } else {
1308 // For non-LAB allocations, we have no way to retract the allocation, and
1309 // have to explicitly overwrite the copy with the filler object. With that overwrite,
1310 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
1311 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
1312 fill_with_object(copy, size);
1313 shenandoah_assert_correct(nullptr, copy_val);
1314 // For non-LAB allocations, the object has already been registered
1315 }
1316 shenandoah_assert_correct(nullptr, result);
1317 return result;
1318 }
1319 }
1320
1321 void ShenandoahHeap::trash_cset_regions() {
1322 ShenandoahHeapLocker locker(lock());
1323
1324 ShenandoahCollectionSet* set = collection_set();
1325 ShenandoahHeapRegion* r;
1326 set->clear_current_index();
1327 while ((r = set->next()) != nullptr) {
1328 r->make_trash();
1329 }
1330 collection_set()->clear();
1331 }
1332
1333 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const {
1334 st->print_cr("Heap Regions:");
1335 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start");
1336 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set");
1337 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start");
1338 st->print_cr("UWM=update watermark, U=used");
1339 st->print_cr("T=TLAB allocs, G=GCLAB allocs");
1340 st->print_cr("S=shared allocs, L=live data");
1341 st->print_cr("CP=critical pins");
1342
1343 for (size_t i = 0; i < num_regions(); i++) {
1344 get_region(i)->print_on(st);
1345 }
1346 }
1347
1348 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) {
1349 assert(start->is_humongous_start(), "reclaim regions starting with the first one");
1350
1351 oop humongous_obj = cast_to_oop(start->bottom());
1352 size_t size = humongous_obj->size();
1353 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
1354 size_t index = start->index() + required_regions - 1;
1355
1356 assert(!start->has_live(), "liveness must be zero");
1357
1358 for(size_t i = 0; i < required_regions; i++) {
1359 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log,
1360 // as it expects that every region belongs to a humongous region starting with a humongous start region.
1361 ShenandoahHeapRegion* region = get_region(index --);
1362
1363 assert(region->is_humongous(), "expect correct humongous start or continuation");
1364 assert(!region->is_cset(), "Humongous region should not be in collection set");
1365
1366 region->make_trash_immediate();
1367 }
1368 return required_regions;
1369 }
1370
1371 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure {
1372 public:
1373 ShenandoahCheckCleanGCLABClosure() {}
1374 void do_thread(Thread* thread) {
1375 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1376 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1377 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement");
1378
1379 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1380 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1381 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1382 assert(plab->words_remaining() == 0, "PLAB should not need retirement");
1383 }
1384 }
1385 };
1386
1387 class ShenandoahRetireGCLABClosure : public ThreadClosure {
1388 private:
1389 bool const _resize;
1390 public:
1391 ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {}
1392 void do_thread(Thread* thread) {
1393 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
1394 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name());
1395 gclab->retire();
1396 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) {
1397 ShenandoahThreadLocalData::set_gclab_size(thread, 0);
1398 }
1399
1400 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1401 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
1402 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name());
1403
1404 // There are two reasons to retire all plabs between old-gen evacuation passes.
1405 // 1. We need to make the plab memory parsable by remembered-set scanning.
1406 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region
1407 ShenandoahGenerationalHeap::heap()->retire_plab(plab, thread);
1408 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) {
1409 ShenandoahThreadLocalData::set_plab_size(thread, 0);
1410 }
1411 }
1412 }
1413 };
1414
1415 void ShenandoahHeap::labs_make_parsable() {
1416 assert(UseTLAB, "Only call with UseTLAB");
1417
1418 ShenandoahRetireGCLABClosure cl(false);
1419
1420 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1421 ThreadLocalAllocBuffer& tlab = t->tlab();
1422 tlab.make_parsable();
1423 cl.do_thread(t);
1424 }
1425
1426 workers()->threads_do(&cl);
1427 }
1428
1429 void ShenandoahHeap::tlabs_retire(bool resize) {
1430 assert(UseTLAB, "Only call with UseTLAB");
1431 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1432
1433 ThreadLocalAllocStats stats;
1434
1435 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1436 ThreadLocalAllocBuffer& tlab = t->tlab();
1437 tlab.retire(&stats);
1438 if (resize) {
1439 tlab.resize();
1440 }
1441 }
1442
1443 stats.publish();
1444
1445 #ifdef ASSERT
1446 ShenandoahCheckCleanGCLABClosure cl;
1447 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1448 cl.do_thread(t);
1449 }
1450 workers()->threads_do(&cl);
1451 #endif
1452 }
1453
1454 void ShenandoahHeap::gclabs_retire(bool resize) {
1455 assert(UseTLAB, "Only call with UseTLAB");
1456 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled");
1457
1458 ShenandoahRetireGCLABClosure cl(resize);
1459 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1460 cl.do_thread(t);
1461 }
1462 workers()->threads_do(&cl);
1463
1464 if (safepoint_workers() != nullptr) {
1465 safepoint_workers()->threads_do(&cl);
1466 }
1467 }
1468
1469 // Returns size in bytes
1470 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
1471 // Return the max allowed size, and let the allocation path
1472 // figure out the safe size for current allocation.
1473 return ShenandoahHeapRegion::max_tlab_size_bytes();
1474 }
1475
1476 size_t ShenandoahHeap::max_tlab_size() const {
1477 // Returns size in words
1478 return ShenandoahHeapRegion::max_tlab_size_words();
1479 }
1480
1481 void ShenandoahHeap::collect(GCCause::Cause cause) {
1482 control_thread()->request_gc(cause);
1483 }
1484
1485 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) {
1486 //assert(false, "Shouldn't need to do full collections");
1487 }
1488
1489 HeapWord* ShenandoahHeap::block_start(const void* addr) const {
1490 ShenandoahHeapRegion* r = heap_region_containing(addr);
1491 if (r != nullptr) {
1492 return r->block_start(addr);
1493 }
1494 return nullptr;
1495 }
1496
1497 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const {
1498 ShenandoahHeapRegion* r = heap_region_containing(addr);
1499 return r->block_is_obj(addr);
1500 }
1501
1502 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const {
1503 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr);
1504 }
1505
1506 void ShenandoahHeap::prepare_for_verify() {
1507 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) {
1508 labs_make_parsable();
1509 }
1510 }
1511
1512 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
1513 if (_shenandoah_policy->is_at_shutdown()) {
1514 return;
1515 }
1516
1517 if (_control_thread != nullptr) {
1518 tcl->do_thread(_control_thread);
1519 }
1520
1521 workers()->threads_do(tcl);
1522 if (_safepoint_workers != nullptr) {
1523 _safepoint_workers->threads_do(tcl);
1524 }
1525 }
1526
1527 void ShenandoahHeap::print_tracing_info() const {
1528 LogTarget(Info, gc, stats) lt;
1529 if (lt.is_enabled()) {
1530 ResourceMark rm;
1531 LogStream ls(lt);
1532
1533 phase_timings()->print_global_on(&ls);
1534
1535 ls.cr();
1536 ls.cr();
1537
1538 shenandoah_policy()->print_gc_stats(&ls);
1539
1540 ls.cr();
1541
1542 evac_tracker()->print_global_on(&ls);
1543
1544 ls.cr();
1545 ls.cr();
1546 }
1547 }
1548
1549 void ShenandoahHeap::set_gc_generation(ShenandoahGeneration* generation) {
1550 shenandoah_assert_control_or_vm_thread_at_safepoint();
1551 _gc_generation = generation;
1552 }
1553
1554 // Active generation may only be set by the VM thread at a safepoint.
1555 void ShenandoahHeap::set_active_generation() {
1556 assert(Thread::current()->is_VM_thread(), "Only the VM Thread");
1557 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!");
1558 assert(_gc_generation != nullptr, "Will set _active_generation to nullptr");
1559 _active_generation = _gc_generation;
1560 }
1561
1562 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
1563 shenandoah_policy()->record_collection_cause(cause);
1564
1565 assert(gc_cause() == GCCause::_no_gc, "Over-writing cause");
1566 assert(_gc_generation == nullptr, "Over-writing _gc_generation");
1567
1568 set_gc_cause(cause);
1569 set_gc_generation(generation);
1570
1571 generation->heuristics()->record_cycle_start();
1572 }
1573
1574 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
1575 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set");
1576 assert(_gc_generation != nullptr, "_gc_generation wasn't set");
1577
1578 generation->heuristics()->record_cycle_end();
1579 if (mode()->is_generational() && generation->is_global()) {
1580 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
1581 young_generation()->heuristics()->record_cycle_end();
1582 old_generation()->heuristics()->record_cycle_end();
1583 }
1584
1585 set_gc_generation(nullptr);
1586 set_gc_cause(GCCause::_no_gc);
1587 }
1588
1589 void ShenandoahHeap::verify(VerifyOption vo) {
1590 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
1591 if (ShenandoahVerify) {
1592 verifier()->verify_generic(vo);
1593 } else {
1594 // TODO: Consider allocating verification bitmaps on demand,
1595 // and turn this on unconditionally.
1596 }
1597 }
1598 }
1599 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const {
1600 return _free_set->capacity();
1601 }
1602
1603 class ObjectIterateScanRootClosure : public BasicOopIterateClosure {
1604 private:
1605 MarkBitMap* _bitmap;
1606 ShenandoahScanObjectStack* _oop_stack;
1607 ShenandoahHeap* const _heap;
1608 ShenandoahMarkingContext* const _marking_context;
1609
1610 template <class T>
1611 void do_oop_work(T* p) {
1612 T o = RawAccess<>::oop_load(p);
1613 if (!CompressedOops::is_null(o)) {
1614 oop obj = CompressedOops::decode_not_null(o);
1615 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1616 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1617 return;
1618 }
1619 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1620
1621 assert(oopDesc::is_oop(obj), "must be a valid oop");
1622 if (!_bitmap->is_marked(obj)) {
1623 _bitmap->mark(obj);
1624 _oop_stack->push(obj);
1625 }
1626 }
1627 }
1628 public:
1629 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) :
1630 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()),
1631 _marking_context(_heap->marking_context()) {}
1632 void do_oop(oop* p) { do_oop_work(p); }
1633 void do_oop(narrowOop* p) { do_oop_work(p); }
1634 };
1635
1636 /*
1637 * This is public API, used in preparation of object_iterate().
1638 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't
1639 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can
1640 * control, we call SH::tlabs_retire, SH::gclabs_retire.
1641 */
1642 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) {
1643 // No-op.
1644 }
1645
1646 /*
1647 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping.
1648 *
1649 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear
1650 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g.
1651 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear
1652 * scanning therefore depends on having a valid marking bitmap to support it. However, we only
1653 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid
1654 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just
1655 * wiped the bitmap in preparation for next marking).
1656 *
1657 * For all those reasons, we implement object iteration as a single marking traversal, reporting
1658 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap
1659 * is allowed to report dead objects, but is not required to do so.
1660 */
1661 void ShenandoahHeap::object_iterate(ObjectClosure* cl) {
1662 // Reset bitmap
1663 if (!prepare_aux_bitmap_for_iteration())
1664 return;
1665
1666 ShenandoahScanObjectStack oop_stack;
1667 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack);
1668 // Seed the stack with root scan
1669 scan_roots_for_iteration(&oop_stack, &oops);
1670
1671 // Work through the oop stack to traverse heap
1672 while (! oop_stack.is_empty()) {
1673 oop obj = oop_stack.pop();
1674 assert(oopDesc::is_oop(obj), "must be a valid oop");
1675 cl->do_object(obj);
1676 obj->oop_iterate(&oops);
1677 }
1678
1679 assert(oop_stack.is_empty(), "should be empty");
1680 // Reclaim bitmap
1681 reclaim_aux_bitmap_for_iteration();
1682 }
1683
1684 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() {
1685 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1686
1687 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) {
1688 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration");
1689 return false;
1690 }
1691 // Reset bitmap
1692 _aux_bit_map.clear();
1693 return true;
1694 }
1695
1696 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) {
1697 // Process GC roots according to current GC cycle
1698 // This populates the work stack with initial objects
1699 // It is important to relinquish the associated locks before diving
1700 // into heap dumper
1701 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1;
1702 ShenandoahHeapIterationRootScanner rp(n_workers);
1703 rp.roots_do(oops);
1704 }
1705
1706 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() {
1707 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) {
1708 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration");
1709 }
1710 }
1711
1712 // Closure for parallelly iterate objects
1713 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure {
1714 private:
1715 MarkBitMap* _bitmap;
1716 ShenandoahObjToScanQueue* _queue;
1717 ShenandoahHeap* const _heap;
1718 ShenandoahMarkingContext* const _marking_context;
1719
1720 template <class T>
1721 void do_oop_work(T* p) {
1722 T o = RawAccess<>::oop_load(p);
1723 if (!CompressedOops::is_null(o)) {
1724 oop obj = CompressedOops::decode_not_null(o);
1725 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) {
1726 // There may be dead oops in weak roots in concurrent root phase, do not touch them.
1727 return;
1728 }
1729 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
1730
1731 assert(oopDesc::is_oop(obj), "Must be a valid oop");
1732 if (_bitmap->par_mark(obj)) {
1733 _queue->push(ShenandoahMarkTask(obj));
1734 }
1735 }
1736 }
1737 public:
1738 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) :
1739 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()),
1740 _marking_context(_heap->marking_context()) {}
1741 void do_oop(oop* p) { do_oop_work(p); }
1742 void do_oop(narrowOop* p) { do_oop_work(p); }
1743 };
1744
1745 // Object iterator for parallel heap iteraion.
1746 // The root scanning phase happenes in construction as a preparation of
1747 // parallel marking queues.
1748 // Every worker processes it's own marking queue. work-stealing is used
1749 // to balance workload.
1750 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl {
1751 private:
1752 uint _num_workers;
1753 bool _init_ready;
1754 MarkBitMap* _aux_bit_map;
1755 ShenandoahHeap* _heap;
1756 ShenandoahScanObjectStack _roots_stack; // global roots stack
1757 ShenandoahObjToScanQueueSet* _task_queues;
1758 public:
1759 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) :
1760 _num_workers(num_workers),
1761 _init_ready(false),
1762 _aux_bit_map(bitmap),
1763 _heap(ShenandoahHeap::heap()) {
1764 // Initialize bitmap
1765 _init_ready = _heap->prepare_aux_bitmap_for_iteration();
1766 if (!_init_ready) {
1767 return;
1768 }
1769
1770 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack);
1771 _heap->scan_roots_for_iteration(&_roots_stack, &oops);
1772
1773 _init_ready = prepare_worker_queues();
1774 }
1775
1776 ~ShenandoahParallelObjectIterator() {
1777 // Reclaim bitmap
1778 _heap->reclaim_aux_bitmap_for_iteration();
1779 // Reclaim queue for workers
1780 if (_task_queues!= nullptr) {
1781 for (uint i = 0; i < _num_workers; ++i) {
1782 ShenandoahObjToScanQueue* q = _task_queues->queue(i);
1783 if (q != nullptr) {
1784 delete q;
1785 _task_queues->register_queue(i, nullptr);
1786 }
1787 }
1788 delete _task_queues;
1789 _task_queues = nullptr;
1790 }
1791 }
1792
1793 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1794 if (_init_ready) {
1795 object_iterate_parallel(cl, worker_id, _task_queues);
1796 }
1797 }
1798
1799 private:
1800 // Divide global root_stack into worker queues
1801 bool prepare_worker_queues() {
1802 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers);
1803 // Initialize queues for every workers
1804 for (uint i = 0; i < _num_workers; ++i) {
1805 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
1806 _task_queues->register_queue(i, task_queue);
1807 }
1808 // Divide roots among the workers. Assume that object referencing distribution
1809 // is related with root kind, use round-robin to make every worker have same chance
1810 // to process every kind of roots
1811 size_t roots_num = _roots_stack.size();
1812 if (roots_num == 0) {
1813 // No work to do
1814 return false;
1815 }
1816
1817 for (uint j = 0; j < roots_num; j++) {
1818 uint stack_id = j % _num_workers;
1819 oop obj = _roots_stack.pop();
1820 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj));
1821 }
1822 return true;
1823 }
1824
1825 void object_iterate_parallel(ObjectClosure* cl,
1826 uint worker_id,
1827 ShenandoahObjToScanQueueSet* queue_set) {
1828 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints");
1829 assert(queue_set != nullptr, "task queue must not be null");
1830
1831 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id);
1832 assert(q != nullptr, "object iterate queue must not be null");
1833
1834 ShenandoahMarkTask t;
1835 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q);
1836
1837 // Work through the queue to traverse heap.
1838 // Steal when there is no task in queue.
1839 while (q->pop(t) || queue_set->steal(worker_id, t)) {
1840 oop obj = t.obj();
1841 assert(oopDesc::is_oop(obj), "must be a valid oop");
1842 cl->do_object(obj);
1843 obj->oop_iterate(&oops);
1844 }
1845 assert(q->is_empty(), "should be empty");
1846 }
1847 };
1848
1849 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) {
1850 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map);
1851 }
1852
1853 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
1854 void ShenandoahHeap::keep_alive(oop obj) {
1855 if (is_concurrent_mark_in_progress() && (obj != nullptr)) {
1856 ShenandoahBarrierSet::barrier_set()->enqueue(obj);
1857 }
1858 }
1859
1860 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1861 for (size_t i = 0; i < num_regions(); i++) {
1862 ShenandoahHeapRegion* current = get_region(i);
1863 blk->heap_region_do(current);
1864 }
1865 }
1866
1867 class ShenandoahParallelHeapRegionTask : public WorkerTask {
1868 private:
1869 ShenandoahHeap* const _heap;
1870 ShenandoahHeapRegionClosure* const _blk;
1871 size_t const _stride;
1872
1873 shenandoah_padding(0);
1874 volatile size_t _index;
1875 shenandoah_padding(1);
1876
1877 public:
1878 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) :
1879 WorkerTask("Shenandoah Parallel Region Operation"),
1880 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {}
1881
1882 void work(uint worker_id) {
1883 ShenandoahParallelWorkerSession worker_session(worker_id);
1884 size_t stride = _stride;
1885
1886 size_t max = _heap->num_regions();
1887 while (Atomic::load(&_index) < max) {
1888 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed);
1889 size_t start = cur;
1890 size_t end = MIN2(cur + stride, max);
1891 if (start >= max) break;
1892
1893 for (size_t i = cur; i < end; i++) {
1894 ShenandoahHeapRegion* current = _heap->get_region(i);
1895 _blk->heap_region_do(current);
1896 }
1897 }
1898 }
1899 };
1900
1901 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const {
1902 assert(blk->is_thread_safe(), "Only thread-safe closures here");
1903 const uint active_workers = workers()->active_workers();
1904 const size_t n_regions = num_regions();
1905 size_t stride = ShenandoahParallelRegionStride;
1906 if (stride == 0 && active_workers > 1) {
1907 // Automatically derive the stride to balance the work between threads
1908 // evenly. Do not try to split work if below the reasonable threshold.
1909 constexpr size_t threshold = 4096;
1910 stride = n_regions <= threshold ?
1911 threshold :
1912 (n_regions + active_workers - 1) / active_workers;
1913 }
1914
1915 if (n_regions > stride && active_workers > 1) {
1916 ShenandoahParallelHeapRegionTask task(blk, stride);
1917 workers()->run_task(&task);
1918 } else {
1919 heap_region_iterate(blk);
1920 }
1921 }
1922
1923 class ShenandoahRendezvousClosure : public HandshakeClosure {
1924 public:
1925 inline ShenandoahRendezvousClosure(const char* name) : HandshakeClosure(name) {}
1926 inline void do_thread(Thread* thread) {}
1927 };
1928
1929 void ShenandoahHeap::rendezvous_threads(const char* name) {
1930 ShenandoahRendezvousClosure cl(name);
1931 Handshake::execute(&cl);
1932 }
1933
1934 void ShenandoahHeap::recycle_trash() {
1935 free_set()->recycle_trash();
1936 }
1937
1938 void ShenandoahHeap::do_class_unloading() {
1939 _unloader.unload();
1940 if (mode()->is_generational()) {
1941 old_generation()->set_parsable(false);
1942 }
1943 }
1944
1945 void ShenandoahHeap::stw_weak_refs(bool full_gc) {
1946 // Weak refs processing
1947 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs
1948 : ShenandoahPhaseTimings::degen_gc_weakrefs;
1949 ShenandoahTimingsTracker t(phase);
1950 ShenandoahGCWorkerPhase worker_phase(phase);
1951 shenandoah_assert_generations_reconciled();
1952 gc_generation()->ref_processor()->process_references(phase, workers(), false /* concurrent */);
1953 }
1954
1955 void ShenandoahHeap::prepare_update_heap_references(bool concurrent) {
1956 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1957
1958 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to
1959 // make them parsable for update code to work correctly. Plus, we can compute new sizes
1960 // for future GCLABs here.
1961 if (UseTLAB) {
1962 ShenandoahGCPhase phase(concurrent ?
1963 ShenandoahPhaseTimings::init_update_refs_manage_gclabs :
1964 ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs);
1965 gclabs_retire(ResizeTLAB);
1966 }
1967
1968 _update_refs_iterator.reset();
1969 }
1970
1971 void ShenandoahHeap::propagate_gc_state_to_java_threads() {
1972 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1973 if (_gc_state_changed) {
1974 _gc_state_changed = false;
1975 char state = gc_state();
1976 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
1977 ShenandoahThreadLocalData::set_gc_state(t, state);
1978 }
1979 }
1980 }
1981
1982 void ShenandoahHeap::set_gc_state(uint mask, bool value) {
1983 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint");
1984 _gc_state.set_cond(mask, value);
1985 _gc_state_changed = true;
1986 // Check that if concurrent weak root is set then active_gen isn't null
1987 assert(!is_concurrent_weak_root_in_progress() || active_generation() != nullptr, "Error");
1988 shenandoah_assert_generations_reconciled();
1989 }
1990
1991 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) {
1992 uint mask;
1993 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation");
1994 if (!in_progress && is_concurrent_old_mark_in_progress()) {
1995 assert(mode()->is_generational(), "Only generational GC has old marking");
1996 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING");
1997 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on
1998 mask = YOUNG_MARKING;
1999 } else {
2000 mask = MARKING | YOUNG_MARKING;
2001 }
2002 set_gc_state(mask, in_progress);
2003 manage_satb_barrier(in_progress);
2004 }
2005
2006 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) {
2007 #ifdef ASSERT
2008 // has_forwarded_objects() iff UPDATEREFS or EVACUATION
2009 bool has_forwarded = has_forwarded_objects();
2010 bool updating_or_evacuating = _gc_state.is_set(UPDATEREFS | EVACUATION);
2011 bool evacuating = _gc_state.is_set(EVACUATION);
2012 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()),
2013 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding");
2014 #endif
2015 if (!in_progress && is_concurrent_young_mark_in_progress()) {
2016 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on
2017 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING");
2018 set_gc_state(OLD_MARKING, in_progress);
2019 } else {
2020 set_gc_state(MARKING | OLD_MARKING, in_progress);
2021 }
2022 manage_satb_barrier(in_progress);
2023 }
2024
2025 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
2026 return old_generation()->is_preparing_for_mark();
2027 }
2028
2029 void ShenandoahHeap::manage_satb_barrier(bool active) {
2030 if (is_concurrent_mark_in_progress()) {
2031 // Ignore request to deactivate barrier while concurrent mark is in progress.
2032 // Do not attempt to re-activate the barrier if it is already active.
2033 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2034 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2035 }
2036 } else {
2037 // No concurrent marking is in progress so honor request to deactivate,
2038 // but only if the barrier is already active.
2039 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) {
2040 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active);
2041 }
2042 }
2043 }
2044
2045 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) {
2046 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint");
2047 set_gc_state(EVACUATION, in_progress);
2048 }
2049
2050 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) {
2051 if (in_progress) {
2052 _concurrent_strong_root_in_progress.set();
2053 } else {
2054 _concurrent_strong_root_in_progress.unset();
2055 }
2056 }
2057
2058 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) {
2059 set_gc_state(WEAK_ROOTS, cond);
2060 }
2061
2062 GCTracer* ShenandoahHeap::tracer() {
2063 return shenandoah_policy()->tracer();
2064 }
2065
2066 size_t ShenandoahHeap::tlab_used(Thread* thread) const {
2067 return _free_set->used();
2068 }
2069
2070 bool ShenandoahHeap::try_cancel_gc() {
2071 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
2072 return prev == CANCELLABLE;
2073 }
2074
2075 void ShenandoahHeap::cancel_concurrent_mark() {
2076 if (mode()->is_generational()) {
2077 young_generation()->cancel_marking();
2078 old_generation()->cancel_marking();
2079 }
2080
2081 global_generation()->cancel_marking();
2082
2083 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
2084 }
2085
2086 void ShenandoahHeap::cancel_gc(GCCause::Cause cause) {
2087 if (try_cancel_gc()) {
2088 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause));
2089 log_info(gc)("%s", msg.buffer());
2090 Events::log(Thread::current(), "%s", msg.buffer());
2091 _cancel_requested_time = os::elapsedTime();
2092 }
2093 }
2094
2095 uint ShenandoahHeap::max_workers() {
2096 return _max_workers;
2097 }
2098
2099 void ShenandoahHeap::stop() {
2100 // The shutdown sequence should be able to terminate when GC is running.
2101
2102 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown
2103 _shenandoah_policy->record_shutdown();
2104
2105 // Step 1. Notify control thread that we are in shutdown.
2106 // Note that we cannot do that with stop(), because stop() is blocking and waits for the actual shutdown.
2107 // Doing stop() here would wait for the normal GC cycle to complete, never falling through to cancel below.
2108 control_thread()->prepare_for_graceful_shutdown();
2109
2110 // Step 2. Notify GC workers that we are cancelling GC.
2111 cancel_gc(GCCause::_shenandoah_stop_vm);
2112
2113 // Step 3. Wait until GC worker exits normally.
2114 control_thread()->stop();
2115 }
2116
2117 void ShenandoahHeap::stw_unload_classes(bool full_gc) {
2118 if (!unload_classes()) return;
2119 ClassUnloadingContext ctx(_workers->active_workers(),
2120 true /* unregister_nmethods_during_purge */,
2121 false /* lock_nmethod_free_separately */);
2122
2123 // Unload classes and purge SystemDictionary.
2124 {
2125 ShenandoahPhaseTimings::Phase phase = full_gc ?
2126 ShenandoahPhaseTimings::full_gc_purge_class_unload :
2127 ShenandoahPhaseTimings::degen_gc_purge_class_unload;
2128 ShenandoahIsAliveSelector is_alive;
2129 {
2130 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure());
2131 ShenandoahGCPhase gc_phase(phase);
2132 ShenandoahGCWorkerPhase worker_phase(phase);
2133 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
2134
2135 uint num_workers = _workers->active_workers();
2136 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
2137 _workers->run_task(&unlink_task);
2138 }
2139 // Release unloaded nmethods's memory.
2140 ClassUnloadingContext::context()->purge_and_free_nmethods();
2141 }
2142
2143 {
2144 ShenandoahGCPhase phase(full_gc ?
2145 ShenandoahPhaseTimings::full_gc_purge_cldg :
2146 ShenandoahPhaseTimings::degen_gc_purge_cldg);
2147 ClassLoaderDataGraph::purge(true /* at_safepoint */);
2148 }
2149 // Resize and verify metaspace
2150 MetaspaceGC::compute_new_size();
2151 DEBUG_ONLY(MetaspaceUtils::verify();)
2152 }
2153
2154 // Weak roots are either pre-evacuated (final mark) or updated (final updaterefs),
2155 // so they should not have forwarded oops.
2156 // However, we do need to "null" dead oops in the roots, if can not be done
2157 // in concurrent cycles.
2158 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) {
2159 uint num_workers = _workers->active_workers();
2160 ShenandoahPhaseTimings::Phase timing_phase = full_gc ?
2161 ShenandoahPhaseTimings::full_gc_purge_weak_par :
2162 ShenandoahPhaseTimings::degen_gc_purge_weak_par;
2163 ShenandoahGCPhase phase(timing_phase);
2164 ShenandoahGCWorkerPhase worker_phase(timing_phase);
2165 // Cleanup weak roots
2166 if (has_forwarded_objects()) {
2167 ShenandoahForwardedIsAliveClosure is_alive;
2168 ShenandoahUpdateRefsClosure keep_alive;
2169 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahUpdateRefsClosure>
2170 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers);
2171 _workers->run_task(&cleaning_task);
2172 } else {
2173 ShenandoahIsAliveClosure is_alive;
2174 #ifdef ASSERT
2175 ShenandoahAssertNotForwardedClosure verify_cl;
2176 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure>
2177 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers);
2178 #else
2179 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure>
2180 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers);
2181 #endif
2182 _workers->run_task(&cleaning_task);
2183 }
2184 }
2185
2186 void ShenandoahHeap::parallel_cleaning(bool full_gc) {
2187 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2188 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC");
2189 ShenandoahGCPhase phase(full_gc ?
2190 ShenandoahPhaseTimings::full_gc_purge :
2191 ShenandoahPhaseTimings::degen_gc_purge);
2192 stw_weak_refs(full_gc);
2193 stw_process_weak_roots(full_gc);
2194 stw_unload_classes(full_gc);
2195 }
2196
2197 void ShenandoahHeap::set_has_forwarded_objects(bool cond) {
2198 set_gc_state(HAS_FORWARDED, cond);
2199 }
2200
2201 void ShenandoahHeap::set_unload_classes(bool uc) {
2202 _unload_classes.set_cond(uc);
2203 }
2204
2205 bool ShenandoahHeap::unload_classes() const {
2206 return _unload_classes.is_set();
2207 }
2208
2209 address ShenandoahHeap::in_cset_fast_test_addr() {
2210 ShenandoahHeap* heap = ShenandoahHeap::heap();
2211 assert(heap->collection_set() != nullptr, "Sanity");
2212 return (address) heap->collection_set()->biased_map_address();
2213 }
2214
2215 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() {
2216 if (mode()->is_generational()) {
2217 young_generation()->reset_bytes_allocated_since_gc_start();
2218 old_generation()->reset_bytes_allocated_since_gc_start();
2219 }
2220
2221 global_generation()->reset_bytes_allocated_since_gc_start();
2222 }
2223
2224 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) {
2225 _degenerated_gc_in_progress.set_cond(in_progress);
2226 }
2227
2228 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) {
2229 _full_gc_in_progress.set_cond(in_progress);
2230 }
2231
2232 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) {
2233 assert (is_full_gc_in_progress(), "should be");
2234 _full_gc_move_in_progress.set_cond(in_progress);
2235 }
2236
2237 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) {
2238 set_gc_state(UPDATEREFS, in_progress);
2239 }
2240
2241 void ShenandoahHeap::register_nmethod(nmethod* nm) {
2242 ShenandoahCodeRoots::register_nmethod(nm);
2243 }
2244
2245 void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
2246 ShenandoahCodeRoots::unregister_nmethod(nm);
2247 }
2248
2249 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
2250 heap_region_containing(o)->record_pin();
2251 }
2252
2253 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {
2254 ShenandoahHeapRegion* r = heap_region_containing(o);
2255 assert(r != nullptr, "Sanity");
2256 assert(r->pin_count() > 0, "Region " SIZE_FORMAT " should have non-zero pins", r->index());
2257 r->record_unpin();
2258 }
2259
2260 void ShenandoahHeap::sync_pinned_region_status() {
2261 ShenandoahHeapLocker locker(lock());
2262
2263 for (size_t i = 0; i < num_regions(); i++) {
2264 ShenandoahHeapRegion *r = get_region(i);
2265 if (r->is_active()) {
2266 if (r->is_pinned()) {
2267 if (r->pin_count() == 0) {
2268 r->make_unpinned();
2269 }
2270 } else {
2271 if (r->pin_count() > 0) {
2272 r->make_pinned();
2273 }
2274 }
2275 }
2276 }
2277
2278 assert_pinned_region_status();
2279 }
2280
2281 #ifdef ASSERT
2282 void ShenandoahHeap::assert_pinned_region_status() {
2283 for (size_t i = 0; i < num_regions(); i++) {
2284 ShenandoahHeapRegion* r = get_region(i);
2285 shenandoah_assert_generations_reconciled();
2286 if (gc_generation()->contains(r)) {
2287 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0),
2288 "Region " SIZE_FORMAT " pinning status is inconsistent", i);
2289 }
2290 }
2291 }
2292 #endif
2293
2294 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const {
2295 return _gc_timer;
2296 }
2297
2298 void ShenandoahHeap::prepare_concurrent_roots() {
2299 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2300 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2301 set_concurrent_strong_root_in_progress(!collection_set()->is_empty());
2302 set_concurrent_weak_root_in_progress(true);
2303 if (unload_classes()) {
2304 _unloader.prepare();
2305 }
2306 }
2307
2308 void ShenandoahHeap::finish_concurrent_roots() {
2309 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2310 assert(!is_stw_gc_in_progress(), "Only concurrent GC");
2311 if (unload_classes()) {
2312 _unloader.finish();
2313 }
2314 }
2315
2316 #ifdef ASSERT
2317 void ShenandoahHeap::assert_gc_workers(uint nworkers) {
2318 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity");
2319
2320 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
2321 // Use ParallelGCThreads inside safepoints
2322 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u",
2323 ParallelGCThreads, nworkers);
2324 } else {
2325 // Use ConcGCThreads outside safepoints
2326 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u",
2327 ConcGCThreads, nworkers);
2328 }
2329 }
2330 #endif
2331
2332 ShenandoahVerifier* ShenandoahHeap::verifier() {
2333 guarantee(ShenandoahVerify, "Should be enabled");
2334 assert (_verifier != nullptr, "sanity");
2335 return _verifier;
2336 }
2337
2338 template<bool CONCURRENT>
2339 class ShenandoahUpdateHeapRefsTask : public WorkerTask {
2340 private:
2341 ShenandoahHeap* _heap;
2342 ShenandoahRegionIterator* _regions;
2343 public:
2344 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) :
2345 WorkerTask("Shenandoah Update References"),
2346 _heap(ShenandoahHeap::heap()),
2347 _regions(regions) {
2348 }
2349
2350 void work(uint worker_id) {
2351 if (CONCURRENT) {
2352 ShenandoahConcurrentWorkerSession worker_session(worker_id);
2353 ShenandoahSuspendibleThreadSetJoiner stsj;
2354 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
2355 } else {
2356 ShenandoahParallelWorkerSession worker_session(worker_id);
2357 do_work<ShenandoahSTWUpdateRefsClosure>(worker_id);
2358 }
2359 }
2360
2361 private:
2362 template<class T>
2363 void do_work(uint worker_id) {
2364 if (CONCURRENT && (worker_id == 0)) {
2365 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
2366 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
2367 size_t cset_regions = _heap->collection_set()->count();
2368
2369 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
2370 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
2371 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
2372 // next GC cycle.
2373 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
2374 }
2375 // If !CONCURRENT, there's no value in expanding Mutator free set
2376 T cl;
2377 ShenandoahHeapRegion* r = _regions->next();
2378 while (r != nullptr) {
2379 HeapWord* update_watermark = r->get_update_watermark();
2380 assert (update_watermark >= r->bottom(), "sanity");
2381 if (r->is_active() && !r->is_cset()) {
2382 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
2383 if (ShenandoahPacing) {
2384 _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
2385 }
2386 }
2387 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
2388 return;
2389 }
2390 r = _regions->next();
2391 }
2392 }
2393 };
2394
2395 void ShenandoahHeap::update_heap_references(bool concurrent) {
2396 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2397
2398 if (concurrent) {
2399 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator);
2400 workers()->run_task(&task);
2401 } else {
2402 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator);
2403 workers()->run_task(&task);
2404 }
2405 }
2406
2407 ShenandoahSynchronizePinnedRegionStates::ShenandoahSynchronizePinnedRegionStates() : _lock(ShenandoahHeap::heap()->lock()) { }
2408
2409 void ShenandoahSynchronizePinnedRegionStates::heap_region_do(ShenandoahHeapRegion* r) {
2410 // Drop "pinned" state from regions that no longer have a pinned count. Put
2411 // regions with a pinned count into the "pinned" state.
2412 if (r->is_active()) {
2413 if (r->is_pinned()) {
2414 if (r->pin_count() == 0) {
2415 ShenandoahHeapLocker locker(_lock);
2416 r->make_unpinned();
2417 }
2418 } else {
2419 if (r->pin_count() > 0) {
2420 ShenandoahHeapLocker locker(_lock);
2421 r->make_pinned();
2422 }
2423 }
2424 }
2425 }
2426
2427 void ShenandoahHeap::update_heap_region_states(bool concurrent) {
2428 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
2429 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
2430
2431 {
2432 ShenandoahGCPhase phase(concurrent ?
2433 ShenandoahPhaseTimings::final_update_refs_update_region_states :
2434 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states);
2435
2436 final_update_refs_update_region_states();
2437
2438 assert_pinned_region_status();
2439 }
2440
2441 {
2442 ShenandoahGCPhase phase(concurrent ?
2443 ShenandoahPhaseTimings::final_update_refs_trash_cset :
2444 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset);
2445 trash_cset_regions();
2446 }
2447 }
2448
2449 void ShenandoahHeap::final_update_refs_update_region_states() {
2450 ShenandoahSynchronizePinnedRegionStates cl;
2451 parallel_heap_region_iterate(&cl);
2452 }
2453
2454 void ShenandoahHeap::rebuild_free_set(bool concurrent) {
2455 ShenandoahGCPhase phase(concurrent ?
2456 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset :
2457 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset);
2458 ShenandoahHeapLocker locker(lock());
2459 size_t young_cset_regions, old_cset_regions;
2460 size_t first_old_region, last_old_region, old_region_count;
2461 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count);
2462 // If there are no old regions, first_old_region will be greater than last_old_region
2463 assert((first_old_region > last_old_region) ||
2464 ((last_old_region + 1 - first_old_region >= old_region_count) &&
2465 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()),
2466 "sanity: old_region_count: " SIZE_FORMAT ", first_old_region: " SIZE_FORMAT ", last_old_region: " SIZE_FORMAT,
2467 old_region_count, first_old_region, last_old_region);
2468
2469 if (mode()->is_generational()) {
2470 #ifdef ASSERT
2471 if (ShenandoahVerify) {
2472 verifier()->verify_before_rebuilding_free_set();
2473 }
2474 #endif
2475
2476 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this
2477 // available for transfer to old. Note that transfer of humongous regions does not impact available.
2478 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2479 size_t allocation_runway = gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions);
2480 gen_heap->compute_old_generation_balance(allocation_runway, old_cset_regions);
2481
2482 // Total old_available may have been expanded to hold anticipated promotions. We trigger if the fragmented available
2483 // memory represents more than 16 regions worth of data. Note that fragmentation may increase when we promote regular
2484 // regions in place when many of these regular regions have an abundant amount of available memory within them. Fragmentation
2485 // will decrease as promote-by-copy consumes the available memory within these partially consumed regions.
2486 //
2487 // We consider old-gen to have excessive fragmentation if more than 12.5% of old-gen is free memory that resides
2488 // within partially consumed regions of memory.
2489 }
2490 // Rebuild free set based on adjusted generation sizes.
2491 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, old_region_count);
2492
2493 if (mode()->is_generational()) {
2494 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
2495 ShenandoahOldGeneration* old_gen = gen_heap->old_generation();
2496 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions());
2497 }
2498 }
2499
2500 void ShenandoahHeap::print_extended_on(outputStream *st) const {
2501 print_on(st);
2502 st->cr();
2503 print_heap_regions_on(st);
2504 }
2505
2506 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) {
2507 size_t slice = r->index() / _bitmap_regions_per_slice;
2508
2509 size_t regions_from = _bitmap_regions_per_slice * slice;
2510 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1));
2511 for (size_t g = regions_from; g < regions_to; g++) {
2512 assert (g / _bitmap_regions_per_slice == slice, "same slice");
2513 if (skip_self && g == r->index()) continue;
2514 if (get_region(g)->is_committed()) {
2515 return true;
2516 }
2517 }
2518 return false;
2519 }
2520
2521 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
2522 shenandoah_assert_heaplocked();
2523
2524 // Bitmaps in special regions do not need commits
2525 if (_bitmap_region_special) {
2526 return true;
2527 }
2528
2529 if (is_bitmap_slice_committed(r, true)) {
2530 // Some other region from the group is already committed, meaning the bitmap
2531 // slice is already committed, we exit right away.
2532 return true;
2533 }
2534
2535 // Commit the bitmap slice:
2536 size_t slice = r->index() / _bitmap_regions_per_slice;
2537 size_t off = _bitmap_bytes_per_slice * slice;
2538 size_t len = _bitmap_bytes_per_slice;
2539 char* start = (char*) _bitmap_region.start() + off;
2540
2541 if (!os::commit_memory(start, len, false)) {
2542 return false;
2543 }
2544
2545 if (AlwaysPreTouch) {
2546 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
2547 }
2548
2549 return true;
2550 }
2551
2552 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
2553 shenandoah_assert_heaplocked();
2554
2555 // Bitmaps in special regions do not need uncommits
2556 if (_bitmap_region_special) {
2557 return true;
2558 }
2559
2560 if (is_bitmap_slice_committed(r, true)) {
2561 // Some other region from the group is still committed, meaning the bitmap
2562 // slice is should stay committed, exit right away.
2563 return true;
2564 }
2565
2566 // Uncommit the bitmap slice:
2567 size_t slice = r->index() / _bitmap_regions_per_slice;
2568 size_t off = _bitmap_bytes_per_slice * slice;
2569 size_t len = _bitmap_bytes_per_slice;
2570 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) {
2571 return false;
2572 }
2573 return true;
2574 }
2575
2576 void ShenandoahHeap::safepoint_synchronize_begin() {
2577 StackWatermarkSet::safepoint_synchronize_begin();
2578 SuspendibleThreadSet::synchronize();
2579 }
2580
2581 void ShenandoahHeap::safepoint_synchronize_end() {
2582 SuspendibleThreadSet::desynchronize();
2583 }
2584
2585 void ShenandoahHeap::try_inject_alloc_failure() {
2586 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) {
2587 _inject_alloc_failure.set();
2588 os::naked_short_sleep(1);
2589 if (cancelled_gc()) {
2590 log_info(gc)("Allocation failure was successfully injected");
2591 }
2592 }
2593 }
2594
2595 bool ShenandoahHeap::should_inject_alloc_failure() {
2596 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset();
2597 }
2598
2599 void ShenandoahHeap::initialize_serviceability() {
2600 _memory_pool = new ShenandoahMemoryPool(this);
2601 _cycle_memory_manager.add_pool(_memory_pool);
2602 _stw_memory_manager.add_pool(_memory_pool);
2603 }
2604
2605 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() {
2606 GrowableArray<GCMemoryManager*> memory_managers(2);
2607 memory_managers.append(&_cycle_memory_manager);
2608 memory_managers.append(&_stw_memory_manager);
2609 return memory_managers;
2610 }
2611
2612 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
2613 GrowableArray<MemoryPool*> memory_pools(1);
2614 memory_pools.append(_memory_pool);
2615 return memory_pools;
2616 }
2617
2618 MemoryUsage ShenandoahHeap::memory_usage() {
2619 return MemoryUsage(_initial_size, used(), committed(), max_capacity());
2620 }
2621
2622 ShenandoahRegionIterator::ShenandoahRegionIterator() :
2623 _heap(ShenandoahHeap::heap()),
2624 _index(0) {}
2625
2626 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) :
2627 _heap(heap),
2628 _index(0) {}
2629
2630 void ShenandoahRegionIterator::reset() {
2631 _index = 0;
2632 }
2633
2634 bool ShenandoahRegionIterator::has_next() const {
2635 return _index < _heap->num_regions();
2636 }
2637
2638 char ShenandoahHeap::gc_state() const {
2639 return _gc_state.raw_value();
2640 }
2641
2642 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) {
2643 #ifdef ASSERT
2644 assert(_liveness_cache != nullptr, "sanity");
2645 assert(worker_id < _max_workers, "sanity");
2646 for (uint i = 0; i < num_regions(); i++) {
2647 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty");
2648 }
2649 #endif
2650 return _liveness_cache[worker_id];
2651 }
2652
2653 void ShenandoahHeap::flush_liveness_cache(uint worker_id) {
2654 assert(worker_id < _max_workers, "sanity");
2655 assert(_liveness_cache != nullptr, "sanity");
2656 ShenandoahLiveData* ld = _liveness_cache[worker_id];
2657 for (uint i = 0; i < num_regions(); i++) {
2658 ShenandoahLiveData live = ld[i];
2659 if (live > 0) {
2660 ShenandoahHeapRegion* r = get_region(i);
2661 r->increase_live_data_gc_words(live);
2662 ld[i] = 0;
2663 }
2664 }
2665 }
2666
2667 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const {
2668 if (is_idle()) return false;
2669
2670 // Objects allocated after marking start are implicitly alive, don't need any barriers during
2671 // marking phase.
2672 if (is_concurrent_mark_in_progress() &&
2673 !marking_context()->allocated_after_mark_start(obj)) {
2674 return true;
2675 }
2676
2677 // Can not guarantee obj is deeply good.
2678 if (has_forwarded_objects()) {
2679 return true;
2680 }
2681
2682 return false;
2683 }
2684
2685 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) {
2686 #if INCLUDE_CDS_JAVA_HEAP
2687 // CDS wants a continuous memory range to load a bunch of objects.
2688 // This effectively bypasses normal allocation paths, and requires
2689 // a bit of massaging to unbreak GC invariants.
2690
2691 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size);
2692
2693 // Easy case: a single regular region, no further adjustments needed.
2694 if (!ShenandoahHeapRegion::requires_humongous(size)) {
2695 return allocate_memory(req);
2696 }
2697
2698 // Hard case: the requested size would cause a humongous allocation.
2699 // We need to make sure it looks like regular allocation to the rest of GC.
2700
2701 // CDS code would guarantee no objects straddle multiple regions, as long as
2702 // regions are as large as MIN_GC_REGION_ALIGNMENT. It is impractical at this
2703 // point to deal with case when Shenandoah runs with smaller regions.
2704 // TODO: This check can be dropped once MIN_GC_REGION_ALIGNMENT agrees more with Shenandoah.
2705 if (ShenandoahHeapRegion::region_size_bytes() < ArchiveHeapWriter::MIN_GC_REGION_ALIGNMENT) {
2706 return nullptr;
2707 }
2708
2709 HeapWord* mem = allocate_memory(req);
2710 size_t start_idx = heap_region_index_containing(mem);
2711 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
2712
2713 // Flip humongous -> regular.
2714 {
2715 ShenandoahHeapLocker locker(lock(), false);
2716 for (size_t c = start_idx; c < start_idx + num_regions; c++) {
2717 get_region(c)->make_regular_bypass();
2718 }
2719 }
2720
2721 return mem;
2722 #else
2723 assert(false, "Archive heap loader should not be available, should not be here");
2724 return nullptr;
2725 #endif // INCLUDE_CDS_JAVA_HEAP
2726 }
2727
2728 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) {
2729 // Nothing to do here, except checking that heap looks fine.
2730 #ifdef ASSERT
2731 HeapWord* start = archive_space.start();
2732 HeapWord* end = archive_space.end();
2733
2734 // No unclaimed space between the objects.
2735 // Objects are properly allocated in correct regions.
2736 HeapWord* cur = start;
2737 while (cur < end) {
2738 oop oop = cast_to_oop(cur);
2739 shenandoah_assert_in_correct_region(nullptr, oop);
2740 cur += oop->size();
2741 }
2742
2743 // No unclaimed tail at the end of archive space.
2744 assert(cur == end,
2745 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT,
2746 p2i(cur), p2i(end));
2747
2748 // Region bounds are good.
2749 ShenandoahHeapRegion* begin_reg = heap_region_containing(start);
2750 ShenandoahHeapRegion* end_reg = heap_region_containing(end);
2751 assert(begin_reg->is_regular(), "Must be");
2752 assert(end_reg->is_regular(), "Must be");
2753 assert(begin_reg->bottom() == start,
2754 "Must agree: archive-space-start: " PTR_FORMAT ", begin-region-bottom: " PTR_FORMAT,
2755 p2i(start), p2i(begin_reg->bottom()));
2756 assert(end_reg->top() == end,
2757 "Must agree: archive-space-end: " PTR_FORMAT ", end-region-top: " PTR_FORMAT,
2758 p2i(end), p2i(end_reg->top()));
2759 #endif
2760 }
2761
2762 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const {
2763 if (!mode()->is_generational()) {
2764 return global_generation();
2765 } else if (affiliation == YOUNG_GENERATION) {
2766 return young_generation();
2767 } else if (affiliation == OLD_GENERATION) {
2768 return old_generation();
2769 }
2770
2771 ShouldNotReachHere();
2772 return nullptr;
2773 }
2774
2775 void ShenandoahHeap::log_heap_status(const char* msg) const {
2776 if (mode()->is_generational()) {
2777 young_generation()->log_status(msg);
2778 old_generation()->log_status(msg);
2779 } else {
2780 global_generation()->log_status(msg);
2781 }
2782 }
2783