1 /* 2 * Copyright (c) 2023, 2025, 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 28 #include "cds/archiveHeapWriter.hpp" 29 #include "classfile/systemDictionary.hpp" 30 #include "gc/shared/classUnloadingContext.hpp" 31 #include "gc/shared/fullGCForwarding.inline.hpp" 32 #include "gc/shared/gcArguments.hpp" 33 #include "gc/shared/gcTimer.hpp" 34 #include "gc/shared/gcTraceTime.inline.hpp" 35 #include "gc/shared/gc_globals.hpp" 36 #include "gc/shared/locationPrinter.inline.hpp" 37 #include "gc/shared/memAllocator.hpp" 38 #include "gc/shared/plab.hpp" 39 #include "gc/shared/tlab_globals.hpp" 40 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp" 41 #include "gc/shenandoah/heuristics/shenandoahYoungHeuristics.hpp" 42 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp" 43 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp" 44 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp" 45 #include "gc/shenandoah/shenandoahAllocRequest.hpp" 46 #include "gc/shenandoah/shenandoahBarrierSet.hpp" 47 #include "gc/shenandoah/shenandoahClosures.inline.hpp" 48 #include "gc/shenandoah/shenandoahCodeRoots.hpp" 49 #include "gc/shenandoah/shenandoahCollectionSet.hpp" 50 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp" 51 #include "gc/shenandoah/shenandoahConcurrentMark.hpp" 52 #include "gc/shenandoah/shenandoahControlThread.hpp" 53 #include "gc/shenandoah/shenandoahFreeSet.hpp" 54 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp" 55 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp" 56 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp" 57 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 58 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp" 59 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp" 60 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp" 61 #include "gc/shenandoah/shenandoahInitLogger.hpp" 62 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp" 63 #include "gc/shenandoah/shenandoahMemoryPool.hpp" 64 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp" 65 #include "gc/shenandoah/shenandoahOldGeneration.hpp" 66 #include "gc/shenandoah/shenandoahPacer.inline.hpp" 67 #include "gc/shenandoah/shenandoahPadding.hpp" 68 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp" 69 #include "gc/shenandoah/shenandoahPhaseTimings.hpp" 70 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp" 71 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp" 72 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp" 73 #include "gc/shenandoah/shenandoahSTWMark.hpp" 74 #include "gc/shenandoah/shenandoahUncommitThread.hpp" 75 #include "gc/shenandoah/shenandoahUtils.hpp" 76 #include "gc/shenandoah/shenandoahVerifier.hpp" 77 #include "gc/shenandoah/shenandoahVMOperations.hpp" 78 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp" 79 #include "gc/shenandoah/shenandoahWorkGroup.hpp" 80 #include "gc/shenandoah/shenandoahYoungGeneration.hpp" 81 #include "memory/allocation.hpp" 82 #include "memory/classLoaderMetaspace.hpp" 83 #include "memory/memoryReserver.hpp" 84 #include "memory/metaspaceUtils.hpp" 85 #include "memory/universe.hpp" 86 #include "nmt/mallocTracker.hpp" 87 #include "nmt/memTracker.hpp" 88 #include "oops/compressedOops.inline.hpp" 89 #include "prims/jvmtiTagMap.hpp" 90 #include "runtime/atomic.hpp" 91 #include "runtime/globals.hpp" 92 #include "runtime/interfaceSupport.inline.hpp" 93 #include "runtime/java.hpp" 94 #include "runtime/orderAccess.hpp" 95 #include "runtime/safepointMechanism.hpp" 96 #include "runtime/stackWatermarkSet.hpp" 97 #include "runtime/threads.hpp" 98 #include "runtime/vmThread.hpp" 99 #include "utilities/events.hpp" 100 #include "utilities/globalDefinitions.hpp" 101 #include "utilities/powerOfTwo.hpp" 102 #if INCLUDE_JVMCI 103 #include "jvmci/jvmci.hpp" 104 #endif 105 #if INCLUDE_JFR 106 #include "gc/shenandoah/shenandoahJfrSupport.hpp" 107 #endif 108 109 class ShenandoahPretouchHeapTask : public WorkerTask { 110 private: 111 ShenandoahRegionIterator _regions; 112 const size_t _page_size; 113 public: 114 ShenandoahPretouchHeapTask(size_t page_size) : 115 WorkerTask("Shenandoah Pretouch Heap"), 116 _page_size(page_size) {} 117 118 virtual void work(uint worker_id) { 119 ShenandoahHeapRegion* r = _regions.next(); 120 while (r != nullptr) { 121 if (r->is_committed()) { 122 os::pretouch_memory(r->bottom(), r->end(), _page_size); 123 } 124 r = _regions.next(); 125 } 126 } 127 }; 128 129 class ShenandoahPretouchBitmapTask : public WorkerTask { 130 private: 131 ShenandoahRegionIterator _regions; 132 char* _bitmap_base; 133 const size_t _bitmap_size; 134 const size_t _page_size; 135 public: 136 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) : 137 WorkerTask("Shenandoah Pretouch Bitmap"), 138 _bitmap_base(bitmap_base), 139 _bitmap_size(bitmap_size), 140 _page_size(page_size) {} 141 142 virtual void work(uint worker_id) { 143 ShenandoahHeapRegion* r = _regions.next(); 144 while (r != nullptr) { 145 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor(); 146 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor(); 147 assert (end <= _bitmap_size, "end is sane: %zu < %zu", end, _bitmap_size); 148 149 if (r->is_committed()) { 150 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size); 151 } 152 153 r = _regions.next(); 154 } 155 } 156 }; 157 158 static ReservedSpace reserve(size_t size, size_t preferred_page_size) { 159 // When a page size is given we don't want to mix large 160 // and normal pages. If the size is not a multiple of the 161 // page size it will be aligned up to achieve this. 162 size_t alignment = os::vm_allocation_granularity(); 163 if (preferred_page_size != os::vm_page_size()) { 164 alignment = MAX2(preferred_page_size, alignment); 165 size = align_up(size, alignment); 166 } 167 168 const ReservedSpace reserved = MemoryReserver::reserve(size, alignment, preferred_page_size, mtGC); 169 if (!reserved.is_reserved()) { 170 vm_exit_during_initialization("Could not reserve space"); 171 } 172 return reserved; 173 } 174 175 jint ShenandoahHeap::initialize() { 176 // 177 // Figure out heap sizing 178 // 179 180 size_t init_byte_size = InitialHeapSize; 181 size_t min_byte_size = MinHeapSize; 182 size_t max_byte_size = MaxHeapSize; 183 size_t heap_alignment = HeapAlignment; 184 185 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes(); 186 187 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap"); 188 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap"); 189 190 _num_regions = ShenandoahHeapRegion::region_count(); 191 assert(_num_regions == (max_byte_size / reg_size_bytes), 192 "Regions should cover entire heap exactly: %zu != %zu/%zu", 193 _num_regions, max_byte_size, reg_size_bytes); 194 195 size_t num_committed_regions = init_byte_size / reg_size_bytes; 196 num_committed_regions = MIN2(num_committed_regions, _num_regions); 197 assert(num_committed_regions <= _num_regions, "sanity"); 198 _initial_size = num_committed_regions * reg_size_bytes; 199 200 size_t num_min_regions = min_byte_size / reg_size_bytes; 201 num_min_regions = MIN2(num_min_regions, _num_regions); 202 assert(num_min_regions <= _num_regions, "sanity"); 203 _minimum_size = num_min_regions * reg_size_bytes; 204 205 _soft_max_size = SoftMaxHeapSize; 206 207 _committed = _initial_size; 208 209 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 210 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 211 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 212 213 // 214 // Reserve and commit memory for heap 215 // 216 217 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment); 218 initialize_reserved_region(heap_rs); 219 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize); 220 _heap_region_special = heap_rs.special(); 221 222 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0, 223 "Misaligned heap: " PTR_FORMAT, p2i(base())); 224 os::trace_page_sizes_for_requested_size("Heap", 225 max_byte_size, heap_alignment, 226 heap_rs.base(), 227 heap_rs.size(), heap_rs.page_size()); 228 229 #if SHENANDOAH_OPTIMIZED_MARKTASK 230 // The optimized ShenandoahMarkTask takes some bits away from the full object bits. 231 // Fail if we ever attempt to address more than we can. 232 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) { 233 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n" 234 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n" 235 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).", 236 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable()); 237 vm_exit_during_initialization("Fatal Error", buf); 238 } 239 #endif 240 241 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size); 242 if (!_heap_region_special) { 243 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false, 244 "Cannot commit heap memory"); 245 } 246 247 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region)); 248 249 // Now we know the number of regions and heap sizes, initialize the heuristics. 250 initialize_heuristics(); 251 252 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table"); 253 254 // 255 // Worker threads must be initialized after the barrier is configured 256 // 257 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers); 258 if (_workers == nullptr) { 259 vm_exit_during_initialization("Failed necessary allocation."); 260 } else { 261 _workers->initialize_workers(); 262 } 263 264 if (ParallelGCThreads > 1) { 265 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads); 266 _safepoint_workers->initialize_workers(); 267 } 268 269 // 270 // Reserve and commit memory for bitmap(s) 271 // 272 273 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size()); 274 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size); 275 276 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor(); 277 278 guarantee(bitmap_bytes_per_region != 0, 279 "Bitmap bytes per region should not be zero"); 280 guarantee(is_power_of_2(bitmap_bytes_per_region), 281 "Bitmap bytes per region should be power of two: %zu", bitmap_bytes_per_region); 282 283 if (bitmap_page_size > bitmap_bytes_per_region) { 284 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region; 285 _bitmap_bytes_per_slice = bitmap_page_size; 286 } else { 287 _bitmap_regions_per_slice = 1; 288 _bitmap_bytes_per_slice = bitmap_bytes_per_region; 289 } 290 291 guarantee(_bitmap_regions_per_slice >= 1, 292 "Should have at least one region per slice: %zu", 293 _bitmap_regions_per_slice); 294 295 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0, 296 "Bitmap slices should be page-granular: bps = %zu, page size = %zu", 297 _bitmap_bytes_per_slice, bitmap_page_size); 298 299 ReservedSpace bitmap = reserve(_bitmap_size, bitmap_page_size); 300 os::trace_page_sizes_for_requested_size("Mark Bitmap", 301 bitmap_size_orig, bitmap_page_size, 302 bitmap.base(), 303 bitmap.size(), bitmap.page_size()); 304 MemTracker::record_virtual_memory_tag(bitmap, mtGC); 305 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize); 306 _bitmap_region_special = bitmap.special(); 307 308 size_t bitmap_init_commit = _bitmap_bytes_per_slice * 309 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice; 310 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit); 311 if (!_bitmap_region_special) { 312 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false, 313 "Cannot commit bitmap memory"); 314 } 315 316 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions); 317 318 if (ShenandoahVerify) { 319 ReservedSpace verify_bitmap = reserve(_bitmap_size, bitmap_page_size); 320 os::trace_page_sizes_for_requested_size("Verify Bitmap", 321 bitmap_size_orig, bitmap_page_size, 322 verify_bitmap.base(), 323 verify_bitmap.size(), verify_bitmap.page_size()); 324 if (!verify_bitmap.special()) { 325 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false, 326 "Cannot commit verification bitmap memory"); 327 } 328 MemTracker::record_virtual_memory_tag(verify_bitmap, mtGC); 329 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize); 330 _verification_bit_map.initialize(_heap_region, verify_bitmap_region); 331 _verifier = new ShenandoahVerifier(this, &_verification_bit_map); 332 } 333 334 // Reserve aux bitmap for use in object_iterate(). We don't commit it here. 335 size_t aux_bitmap_page_size = bitmap_page_size; 336 337 ReservedSpace aux_bitmap = reserve(_bitmap_size, aux_bitmap_page_size); 338 os::trace_page_sizes_for_requested_size("Aux Bitmap", 339 bitmap_size_orig, aux_bitmap_page_size, 340 aux_bitmap.base(), 341 aux_bitmap.size(), aux_bitmap.page_size()); 342 MemTracker::record_virtual_memory_tag(aux_bitmap, mtGC); 343 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize); 344 _aux_bitmap_region_special = aux_bitmap.special(); 345 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region); 346 347 // 348 // Create regions and region sets 349 // 350 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE); 351 size_t region_storage_size_orig = region_align * _num_regions; 352 size_t region_storage_size = align_up(region_storage_size_orig, 353 MAX2(region_page_size, os::vm_allocation_granularity())); 354 355 ReservedSpace region_storage = reserve(region_storage_size, region_page_size); 356 os::trace_page_sizes_for_requested_size("Region Storage", 357 region_storage_size_orig, region_page_size, 358 region_storage.base(), 359 region_storage.size(), region_storage.page_size()); 360 MemTracker::record_virtual_memory_tag(region_storage, mtGC); 361 if (!region_storage.special()) { 362 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false, 363 "Cannot commit region memory"); 364 } 365 366 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks. 367 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there. 368 // If not successful, bite a bullet and allocate at whatever address. 369 { 370 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity()); 371 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align); 372 const size_t cset_page_size = os::vm_page_size(); 373 374 uintptr_t min = round_up_power_of_2(cset_align); 375 uintptr_t max = (1u << 30u); 376 ReservedSpace cset_rs; 377 378 for (uintptr_t addr = min; addr <= max; addr <<= 1u) { 379 char* req_addr = (char*)addr; 380 assert(is_aligned(req_addr, cset_align), "Should be aligned"); 381 cset_rs = MemoryReserver::reserve(req_addr, cset_size, cset_align, cset_page_size, mtGC); 382 if (cset_rs.is_reserved()) { 383 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr); 384 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base()); 385 break; 386 } 387 } 388 389 if (_collection_set == nullptr) { 390 cset_rs = MemoryReserver::reserve(cset_size, cset_align, os::vm_page_size(), mtGC); 391 if (!cset_rs.is_reserved()) { 392 vm_exit_during_initialization("Cannot reserve memory for collection set"); 393 } 394 395 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base()); 396 } 397 os::trace_page_sizes_for_requested_size("Collection Set", 398 cset_size, cset_page_size, 399 cset_rs.base(), 400 cset_rs.size(), cset_rs.page_size()); 401 } 402 403 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC); 404 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC); 405 406 { 407 ShenandoahHeapLocker locker(lock()); 408 _free_set = new ShenandoahFreeSet(this, _num_regions); 409 for (size_t i = 0; i < _num_regions; i++) { 410 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i; 411 bool is_committed = i < num_committed_regions; 412 void* loc = region_storage.base() + i * region_align; 413 414 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed); 415 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity"); 416 417 _marking_context->initialize_top_at_mark_start(r); 418 _regions[i] = r; 419 assert(!collection_set()->is_in(i), "New region should not be in collection set"); 420 421 _affiliations[i] = ShenandoahAffiliation::FREE; 422 } 423 424 size_t young_cset_regions, old_cset_regions; 425 426 // We are initializing free set. We ignore cset region tallies. 427 size_t first_old, last_old, num_old; 428 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old, last_old, num_old); 429 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, num_old); 430 } 431 432 if (AlwaysPreTouch) { 433 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads, 434 // before initialize() below zeroes it with initializing thread. For any given region, 435 // we touch the region and the corresponding bitmaps from the same thread. 436 ShenandoahPushWorkerScope scope(workers(), _max_workers, false); 437 438 _pretouch_heap_page_size = heap_page_size; 439 _pretouch_bitmap_page_size = bitmap_page_size; 440 441 // OS memory managers may want to coalesce back-to-back pages. Make their jobs 442 // simpler by pre-touching continuous spaces (heap and bitmap) separately. 443 444 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size); 445 _workers->run_task(&bcl); 446 447 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size); 448 _workers->run_task(&hcl); 449 } 450 451 // 452 // Initialize the rest of GC subsystems 453 // 454 455 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC); 456 for (uint worker = 0; worker < _max_workers; worker++) { 457 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC); 458 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData)); 459 } 460 461 // There should probably be Shenandoah-specific options for these, 462 // just as there are G1-specific options. 463 { 464 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set(); 465 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold 466 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent 467 } 468 469 _monitoring_support = new ShenandoahMonitoringSupport(this); 470 _phase_timings = new ShenandoahPhaseTimings(max_workers()); 471 ShenandoahCodeRoots::initialize(); 472 473 if (ShenandoahPacing) { 474 _pacer = new ShenandoahPacer(this); 475 _pacer->setup_for_idle(); 476 } 477 478 initialize_controller(); 479 480 if (ShenandoahUncommit) { 481 _uncommit_thread = new ShenandoahUncommitThread(this); 482 } 483 484 print_init_logger(); 485 486 FullGCForwarding::initialize(_heap_region); 487 488 return JNI_OK; 489 } 490 491 void ShenandoahHeap::initialize_controller() { 492 _control_thread = new ShenandoahControlThread(); 493 } 494 495 void ShenandoahHeap::print_init_logger() const { 496 ShenandoahInitLogger::print(); 497 } 498 499 void ShenandoahHeap::initialize_mode() { 500 if (ShenandoahGCMode != nullptr) { 501 if (strcmp(ShenandoahGCMode, "satb") == 0) { 502 _gc_mode = new ShenandoahSATBMode(); 503 } else if (strcmp(ShenandoahGCMode, "passive") == 0) { 504 _gc_mode = new ShenandoahPassiveMode(); 505 } else if (strcmp(ShenandoahGCMode, "generational") == 0) { 506 _gc_mode = new ShenandoahGenerationalMode(); 507 } else { 508 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option"); 509 } 510 } else { 511 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)"); 512 } 513 _gc_mode->initialize_flags(); 514 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) { 515 vm_exit_during_initialization( 516 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.", 517 _gc_mode->name())); 518 } 519 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) { 520 vm_exit_during_initialization( 521 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.", 522 _gc_mode->name())); 523 } 524 } 525 526 void ShenandoahHeap::initialize_heuristics() { 527 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers(), max_capacity()); 528 _global_generation->initialize_heuristics(mode()); 529 } 530 531 #ifdef _MSC_VER 532 #pragma warning( push ) 533 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 534 #endif 535 536 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) : 537 CollectedHeap(), 538 _gc_generation(nullptr), 539 _active_generation(nullptr), 540 _initial_size(0), 541 _committed(0), 542 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)), 543 _workers(nullptr), 544 _safepoint_workers(nullptr), 545 _heap_region_special(false), 546 _num_regions(0), 547 _regions(nullptr), 548 _affiliations(nullptr), 549 _gc_state_changed(false), 550 _gc_no_progress_count(0), 551 _cancel_requested_time(0), 552 _update_refs_iterator(this), 553 _global_generation(nullptr), 554 _control_thread(nullptr), 555 _uncommit_thread(nullptr), 556 _young_generation(nullptr), 557 _old_generation(nullptr), 558 _shenandoah_policy(policy), 559 _gc_mode(nullptr), 560 _free_set(nullptr), 561 _pacer(nullptr), 562 _verifier(nullptr), 563 _phase_timings(nullptr), 564 _monitoring_support(nullptr), 565 _memory_pool(nullptr), 566 _stw_memory_manager("Shenandoah Pauses"), 567 _cycle_memory_manager("Shenandoah Cycles"), 568 _gc_timer(new ConcurrentGCTimer()), 569 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes), 570 _marking_context(nullptr), 571 _bitmap_size(0), 572 _bitmap_regions_per_slice(0), 573 _bitmap_bytes_per_slice(0), 574 _bitmap_region_special(false), 575 _aux_bitmap_region_special(false), 576 _liveness_cache(nullptr), 577 _collection_set(nullptr) 578 { 579 // Initialize GC mode early, many subsequent initialization procedures depend on it 580 initialize_mode(); 581 _cancelled_gc.set(GCCause::_no_gc); 582 } 583 584 #ifdef _MSC_VER 585 #pragma warning( pop ) 586 #endif 587 588 void ShenandoahHeap::print_heap_on(outputStream* st) const { 589 st->print_cr("Shenandoah Heap"); 590 st->print_cr(" %zu%s max, %zu%s soft max, %zu%s committed, %zu%s used", 591 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()), 592 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()), 593 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()), 594 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used())); 595 st->print_cr(" %zu x %zu %s regions", 596 num_regions(), 597 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()), 598 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes())); 599 600 st->print("Status: "); 601 if (has_forwarded_objects()) st->print("has forwarded objects, "); 602 if (!mode()->is_generational()) { 603 if (is_concurrent_mark_in_progress()) st->print("marking,"); 604 } else { 605 if (is_concurrent_old_mark_in_progress()) st->print("old marking, "); 606 if (is_concurrent_young_mark_in_progress()) st->print("young marking, "); 607 } 608 if (is_evacuation_in_progress()) st->print("evacuating, "); 609 if (is_update_refs_in_progress()) st->print("updating refs, "); 610 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, "); 611 if (is_full_gc_in_progress()) st->print("full gc, "); 612 if (is_full_gc_move_in_progress()) st->print("full gc move, "); 613 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, "); 614 if (is_concurrent_strong_root_in_progress() && 615 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, "); 616 617 if (cancelled_gc()) { 618 st->print("cancelled"); 619 } else { 620 st->print("not cancelled"); 621 } 622 st->cr(); 623 624 st->print_cr("Reserved region:"); 625 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ", 626 p2i(reserved_region().start()), 627 p2i(reserved_region().end())); 628 629 ShenandoahCollectionSet* cset = collection_set(); 630 st->print_cr("Collection set:"); 631 if (cset != nullptr) { 632 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address())); 633 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address())); 634 } else { 635 st->print_cr(" (null)"); 636 } 637 638 st->cr(); 639 640 if (Verbose) { 641 st->cr(); 642 print_heap_regions_on(st); 643 } 644 } 645 646 void ShenandoahHeap::print_gc_on(outputStream* st) const { 647 print_heap_regions_on(st); 648 } 649 650 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure { 651 public: 652 void do_thread(Thread* thread) { 653 assert(thread != nullptr, "Sanity"); 654 ShenandoahThreadLocalData::initialize_gclab(thread); 655 } 656 }; 657 658 void ShenandoahHeap::post_initialize() { 659 CollectedHeap::post_initialize(); 660 661 // Schedule periodic task to report on gc thread CPU utilization 662 _mmu_tracker.initialize(); 663 664 MutexLocker ml(Threads_lock); 665 666 ShenandoahInitWorkerGCLABClosure init_gclabs; 667 _workers->threads_do(&init_gclabs); 668 669 // gclab can not be initialized early during VM startup, as it can not determinate its max_size. 670 // Now, we will let WorkerThreads to initialize gclab when new worker is created. 671 _workers->set_initialize_gclab(); 672 673 // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump 674 // during a concurrent evacuation phase. 675 if (_safepoint_workers != nullptr) { 676 _safepoint_workers->threads_do(&init_gclabs); 677 _safepoint_workers->set_initialize_gclab(); 678 } 679 680 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();) 681 } 682 683 ShenandoahHeuristics* ShenandoahHeap::heuristics() { 684 return _global_generation->heuristics(); 685 } 686 687 size_t ShenandoahHeap::used() const { 688 return global_generation()->used(); 689 } 690 691 size_t ShenandoahHeap::committed() const { 692 return Atomic::load(&_committed); 693 } 694 695 void ShenandoahHeap::increase_committed(size_t bytes) { 696 shenandoah_assert_heaplocked_or_safepoint(); 697 _committed += bytes; 698 } 699 700 void ShenandoahHeap::decrease_committed(size_t bytes) { 701 shenandoah_assert_heaplocked_or_safepoint(); 702 _committed -= bytes; 703 } 704 705 // For tracking usage based on allocations, it should be the case that: 706 // * The sum of regions::used == heap::used 707 // * The sum of a generation's regions::used == generation::used 708 // * The sum of a generation's humongous regions::free == generation::humongous_waste 709 // These invariants are checked by the verifier on GC safepoints. 710 // 711 // Additional notes: 712 // * When a mutator's allocation request causes a region to be retired, the 713 // free memory left in that region is considered waste. It does not contribute 714 // to the usage, but it _does_ contribute to allocation rate. 715 // * The bottom of a PLAB must be aligned on card size. In some cases this will 716 // require padding in front of the PLAB (a filler object). Because this padding 717 // is included in the region's used memory we include the padding in the usage 718 // accounting as waste. 719 // * Mutator allocations are used to compute an allocation rate. They are also 720 // sent to the Pacer for those purposes. 721 // * There are three sources of waste: 722 // 1. The padding used to align a PLAB on card size 723 // 2. Region's free is less than minimum TLAB size and is retired 724 // 3. The unused portion of memory in the last region of a humongous object 725 void ShenandoahHeap::increase_used(const ShenandoahAllocRequest& req) { 726 size_t actual_bytes = req.actual_size() * HeapWordSize; 727 size_t wasted_bytes = req.waste() * HeapWordSize; 728 ShenandoahGeneration* generation = generation_for(req.affiliation()); 729 730 if (req.is_gc_alloc()) { 731 assert(wasted_bytes == 0 || req.type() == ShenandoahAllocRequest::_alloc_plab, "Only PLABs have waste"); 732 increase_used(generation, actual_bytes + wasted_bytes); 733 } else { 734 assert(req.is_mutator_alloc(), "Expected mutator alloc here"); 735 // padding and actual size both count towards allocation counter 736 generation->increase_allocated(actual_bytes + wasted_bytes); 737 738 // only actual size counts toward usage for mutator allocations 739 increase_used(generation, actual_bytes); 740 741 // notify pacer of both actual size and waste 742 notify_mutator_alloc_words(req.actual_size(), req.waste()); 743 744 if (wasted_bytes > 0 && ShenandoahHeapRegion::requires_humongous(req.actual_size())) { 745 increase_humongous_waste(generation,wasted_bytes); 746 } 747 } 748 } 749 750 void ShenandoahHeap::increase_humongous_waste(ShenandoahGeneration* generation, size_t bytes) { 751 generation->increase_humongous_waste(bytes); 752 if (!generation->is_global()) { 753 global_generation()->increase_humongous_waste(bytes); 754 } 755 } 756 757 void ShenandoahHeap::decrease_humongous_waste(ShenandoahGeneration* generation, size_t bytes) { 758 generation->decrease_humongous_waste(bytes); 759 if (!generation->is_global()) { 760 global_generation()->decrease_humongous_waste(bytes); 761 } 762 } 763 764 void ShenandoahHeap::increase_used(ShenandoahGeneration* generation, size_t bytes) { 765 generation->increase_used(bytes); 766 if (!generation->is_global()) { 767 global_generation()->increase_used(bytes); 768 } 769 } 770 771 void ShenandoahHeap::decrease_used(ShenandoahGeneration* generation, size_t bytes) { 772 generation->decrease_used(bytes); 773 if (!generation->is_global()) { 774 global_generation()->decrease_used(bytes); 775 } 776 } 777 778 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, size_t waste) { 779 if (ShenandoahPacing) { 780 control_thread()->pacing_notify_alloc(words); 781 if (waste > 0) { 782 pacer()->claim_for_alloc<true>(waste); 783 } 784 } 785 } 786 787 size_t ShenandoahHeap::capacity() const { 788 return committed(); 789 } 790 791 size_t ShenandoahHeap::max_capacity() const { 792 return _num_regions * ShenandoahHeapRegion::region_size_bytes(); 793 } 794 795 size_t ShenandoahHeap::soft_max_capacity() const { 796 size_t v = Atomic::load(&_soft_max_size); 797 assert(min_capacity() <= v && v <= max_capacity(), 798 "Should be in bounds: %zu <= %zu <= %zu", 799 min_capacity(), v, max_capacity()); 800 return v; 801 } 802 803 void ShenandoahHeap::set_soft_max_capacity(size_t v) { 804 assert(min_capacity() <= v && v <= max_capacity(), 805 "Should be in bounds: %zu <= %zu <= %zu", 806 min_capacity(), v, max_capacity()); 807 Atomic::store(&_soft_max_size, v); 808 } 809 810 size_t ShenandoahHeap::min_capacity() const { 811 return _minimum_size; 812 } 813 814 size_t ShenandoahHeap::initial_capacity() const { 815 return _initial_size; 816 } 817 818 bool ShenandoahHeap::is_in(const void* p) const { 819 if (!is_in_reserved(p)) { 820 return false; 821 } 822 823 if (is_full_gc_move_in_progress()) { 824 // Full GC move is running, we do not have a consistent region 825 // information yet. But we know the pointer is in heap. 826 return true; 827 } 828 829 // Now check if we point to a live section in active region. 830 const ShenandoahHeapRegion* r = heap_region_containing(p); 831 if (p >= r->top()) { 832 return false; 833 } 834 835 if (r->is_active()) { 836 return true; 837 } 838 839 // The region is trash, but won't be recycled until after concurrent weak 840 // roots. We also don't allow mutators to allocate from trash regions 841 // during weak roots. Concurrent class unloading may access unmarked oops 842 // in trash regions. 843 return r->is_trash() && is_concurrent_weak_root_in_progress(); 844 } 845 846 void ShenandoahHeap::notify_soft_max_changed() { 847 if (_uncommit_thread != nullptr) { 848 _uncommit_thread->notify_soft_max_changed(); 849 } 850 } 851 852 void ShenandoahHeap::notify_explicit_gc_requested() { 853 if (_uncommit_thread != nullptr) { 854 _uncommit_thread->notify_explicit_gc_requested(); 855 } 856 } 857 858 bool ShenandoahHeap::check_soft_max_changed() { 859 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize); 860 size_t old_soft_max = soft_max_capacity(); 861 if (new_soft_max != old_soft_max) { 862 new_soft_max = MAX2(min_capacity(), new_soft_max); 863 new_soft_max = MIN2(max_capacity(), new_soft_max); 864 if (new_soft_max != old_soft_max) { 865 log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s", 866 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max), 867 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max) 868 ); 869 set_soft_max_capacity(new_soft_max); 870 return true; 871 } 872 } 873 return false; 874 } 875 876 void ShenandoahHeap::notify_heap_changed() { 877 // Update monitoring counters when we took a new region. This amortizes the 878 // update costs on slow path. 879 monitoring_support()->notify_heap_changed(); 880 _heap_changed.try_set(); 881 } 882 883 void ShenandoahHeap::set_forced_counters_update(bool value) { 884 monitoring_support()->set_forced_counters_update(value); 885 } 886 887 void ShenandoahHeap::handle_force_counters_update() { 888 monitoring_support()->handle_force_counters_update(); 889 } 890 891 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) { 892 // New object should fit the GCLAB size 893 size_t min_size = MAX2(size, PLAB::min_size()); 894 895 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively. 896 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2; 897 898 new_size = MIN2(new_size, PLAB::max_size()); 899 new_size = MAX2(new_size, PLAB::min_size()); 900 901 // Record new heuristic value even if we take any shortcut. This captures 902 // the case when moderately-sized objects always take a shortcut. At some point, 903 // heuristics should catch up with them. 904 log_debug(gc, free)("Set new GCLAB size: %zu", new_size); 905 ShenandoahThreadLocalData::set_gclab_size(thread, new_size); 906 907 if (new_size < size) { 908 // New size still does not fit the object. Fall back to shared allocation. 909 // This avoids retiring perfectly good GCLABs, when we encounter a large object. 910 log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size); 911 return nullptr; 912 } 913 914 // Retire current GCLAB, and allocate a new one. 915 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread); 916 gclab->retire(); 917 918 size_t actual_size = 0; 919 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size); 920 if (gclab_buf == nullptr) { 921 return nullptr; 922 } 923 924 assert (size <= actual_size, "allocation should fit"); 925 926 // ...and clear or zap just allocated TLAB, if needed. 927 if (ZeroTLAB) { 928 Copy::zero_to_words(gclab_buf, actual_size); 929 } else if (ZapTLAB) { 930 // Skip mangling the space corresponding to the object header to 931 // ensure that the returned space is not considered parsable by 932 // any concurrent GC thread. 933 size_t hdr_size = oopDesc::header_size(); 934 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal); 935 } 936 gclab->set_buf(gclab_buf, actual_size); 937 return gclab->allocate(size); 938 } 939 940 // Called from stubs in JIT code or interpreter 941 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size, 942 size_t requested_size, 943 size_t* actual_size) { 944 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size); 945 HeapWord* res = allocate_memory(req); 946 if (res != nullptr) { 947 *actual_size = req.actual_size(); 948 } else { 949 *actual_size = 0; 950 } 951 return res; 952 } 953 954 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size, 955 size_t word_size, 956 size_t* actual_size) { 957 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size); 958 HeapWord* res = allocate_memory(req); 959 if (res != nullptr) { 960 *actual_size = req.actual_size(); 961 } else { 962 *actual_size = 0; 963 } 964 return res; 965 } 966 967 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) { 968 intptr_t pacer_epoch = 0; 969 bool in_new_region = false; 970 HeapWord* result = nullptr; 971 972 if (req.is_mutator_alloc()) { 973 if (ShenandoahPacing) { 974 pacer()->pace_for_alloc(req.size()); 975 pacer_epoch = pacer()->epoch(); 976 } 977 978 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) { 979 result = allocate_memory_under_lock(req, in_new_region); 980 } 981 982 // Check that gc overhead is not exceeded. 983 // 984 // Shenandoah will grind along for quite a while allocating one 985 // object at a time using shared (non-tlab) allocations. This check 986 // is testing that the GC overhead limit has not been exceeded. 987 // This will notify the collector to start a cycle, but will raise 988 // an OOME to the mutator if the last Full GCs have not made progress. 989 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress(). 990 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) { 991 control_thread()->handle_alloc_failure(req, false); 992 req.set_actual_size(0); 993 return nullptr; 994 } 995 996 if (result == nullptr) { 997 // Block until control thread reacted, then retry allocation. 998 // 999 // It might happen that one of the threads requesting allocation would unblock 1000 // way later after GC happened, only to fail the second allocation, because 1001 // other threads have already depleted the free storage. In this case, a better 1002 // strategy is to try again, until at least one full GC has completed. 1003 // 1004 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after: 1005 // a) We experienced a GC that had good progress, or 1006 // b) We experienced at least one Full GC (whether or not it had good progress) 1007 1008 const size_t original_count = shenandoah_policy()->full_gc_count(); 1009 while (result == nullptr && should_retry_allocation(original_count)) { 1010 control_thread()->handle_alloc_failure(req, true); 1011 result = allocate_memory_under_lock(req, in_new_region); 1012 } 1013 if (result != nullptr) { 1014 // If our allocation request has been satisfied after it initially failed, we count this as good gc progress 1015 notify_gc_progress(); 1016 } 1017 if (log_develop_is_enabled(Debug, gc, alloc)) { 1018 ResourceMark rm; 1019 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu" 1020 ", Original: %zu, Latest: %zu", 1021 Thread::current()->name(), p2i(result), req.type_string(), req.size(), 1022 original_count, get_gc_no_progress_count()); 1023 } 1024 } 1025 } else { 1026 assert(req.is_gc_alloc(), "Can only accept GC allocs here"); 1027 result = allocate_memory_under_lock(req, in_new_region); 1028 // Do not call handle_alloc_failure() here, because we cannot block. 1029 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac(). 1030 } 1031 1032 if (in_new_region) { 1033 notify_heap_changed(); 1034 } 1035 1036 if (result == nullptr) { 1037 req.set_actual_size(0); 1038 } 1039 1040 // This is called regardless of the outcome of the allocation to account 1041 // for any waste created by retiring regions with this request. 1042 increase_used(req); 1043 1044 if (result != nullptr) { 1045 size_t requested = req.size(); 1046 size_t actual = req.actual_size(); 1047 1048 assert (req.is_lab_alloc() || (requested == actual), 1049 "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu", 1050 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual); 1051 1052 if (req.is_mutator_alloc()) { 1053 // If we requested more than we were granted, give the rest back to pacer. 1054 // This only matters if we are in the same pacing epoch: do not try to unpace 1055 // over the budget for the other phase. 1056 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) { 1057 pacer()->unpace_for_alloc(pacer_epoch, requested - actual); 1058 } 1059 } 1060 } 1061 1062 return result; 1063 } 1064 1065 inline bool ShenandoahHeap::should_retry_allocation(size_t original_full_gc_count) const { 1066 return shenandoah_policy()->full_gc_count() == original_full_gc_count 1067 && !shenandoah_policy()->is_at_shutdown(); 1068 } 1069 1070 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) { 1071 // If we are dealing with mutator allocation, then we may need to block for safepoint. 1072 // We cannot block for safepoint for GC allocations, because there is a high chance 1073 // we are already running at safepoint or from stack watermark machinery, and we cannot 1074 // block again. 1075 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc()); 1076 1077 // Make sure the old generation has room for either evacuations or promotions before trying to allocate. 1078 if (req.is_old() && !old_generation()->can_allocate(req)) { 1079 return nullptr; 1080 } 1081 1082 // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available 1083 // memory. 1084 HeapWord* result = _free_set->allocate(req, in_new_region); 1085 1086 // Record the plab configuration for this result and register the object. 1087 if (result != nullptr && req.is_old()) { 1088 old_generation()->configure_plab_for_current_thread(req); 1089 if (req.type() == ShenandoahAllocRequest::_alloc_shared_gc) { 1090 // Register the newly allocated object while we're holding the global lock since there's no synchronization 1091 // built in to the implementation of register_object(). There are potential races when multiple independent 1092 // threads are allocating objects, some of which might span the same card region. For example, consider 1093 // a card table's memory region within which three objects are being allocated by three different threads: 1094 // 1095 // objects being "concurrently" allocated: 1096 // [-----a------][-----b-----][--------------c------------------] 1097 // [---- card table memory range --------------] 1098 // 1099 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a 1100 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region. 1101 // Allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region. 1102 // Allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this 1103 // card region. 1104 // 1105 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as 1106 // last-start representing object b while first-start represents object c. This is why we need to require all 1107 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range. 1108 old_generation()->card_scan()->register_object(result); 1109 } 1110 } 1111 1112 return result; 1113 } 1114 1115 HeapWord* ShenandoahHeap::mem_allocate(size_t size, 1116 bool* gc_overhead_limit_was_exceeded) { 1117 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size); 1118 return allocate_memory(req); 1119 } 1120 1121 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data, 1122 size_t size, 1123 Metaspace::MetadataType mdtype) { 1124 MetaWord* result; 1125 1126 // Inform metaspace OOM to GC heuristics if class unloading is possible. 1127 ShenandoahHeuristics* h = global_generation()->heuristics(); 1128 if (h->can_unload_classes()) { 1129 h->record_metaspace_oom(); 1130 } 1131 1132 // Expand and retry allocation 1133 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype); 1134 if (result != nullptr) { 1135 return result; 1136 } 1137 1138 // Start full GC 1139 collect(GCCause::_metadata_GC_clear_soft_refs); 1140 1141 // Retry allocation 1142 result = loader_data->metaspace_non_null()->allocate(size, mdtype); 1143 if (result != nullptr) { 1144 return result; 1145 } 1146 1147 // Expand and retry allocation 1148 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype); 1149 if (result != nullptr) { 1150 return result; 1151 } 1152 1153 // Out of memory 1154 return nullptr; 1155 } 1156 1157 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure { 1158 private: 1159 ShenandoahHeap* const _heap; 1160 Thread* const _thread; 1161 public: 1162 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) : 1163 _heap(heap), _thread(Thread::current()) {} 1164 1165 void do_object(oop p) { 1166 shenandoah_assert_marked(nullptr, p); 1167 if (!p->is_forwarded()) { 1168 _heap->evacuate_object(p, _thread); 1169 } 1170 } 1171 }; 1172 1173 class ShenandoahEvacuationTask : public WorkerTask { 1174 private: 1175 ShenandoahHeap* const _sh; 1176 ShenandoahCollectionSet* const _cs; 1177 bool _concurrent; 1178 public: 1179 ShenandoahEvacuationTask(ShenandoahHeap* sh, 1180 ShenandoahCollectionSet* cs, 1181 bool concurrent) : 1182 WorkerTask("Shenandoah Evacuation"), 1183 _sh(sh), 1184 _cs(cs), 1185 _concurrent(concurrent) 1186 {} 1187 1188 void work(uint worker_id) { 1189 if (_concurrent) { 1190 ShenandoahConcurrentWorkerSession worker_session(worker_id); 1191 ShenandoahSuspendibleThreadSetJoiner stsj; 1192 ShenandoahEvacOOMScope oom_evac_scope; 1193 do_work(); 1194 } else { 1195 ShenandoahParallelWorkerSession worker_session(worker_id); 1196 ShenandoahEvacOOMScope oom_evac_scope; 1197 do_work(); 1198 } 1199 } 1200 1201 private: 1202 void do_work() { 1203 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh); 1204 ShenandoahHeapRegion* r; 1205 while ((r =_cs->claim_next()) != nullptr) { 1206 assert(r->has_live(), "Region %zu should have been reclaimed early", r->index()); 1207 _sh->marked_object_iterate(r, &cl); 1208 1209 if (ShenandoahPacing) { 1210 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize); 1211 } 1212 1213 if (_sh->check_cancelled_gc_and_yield(_concurrent)) { 1214 break; 1215 } 1216 } 1217 } 1218 }; 1219 1220 class ShenandoahRetireGCLABClosure : public ThreadClosure { 1221 private: 1222 bool const _resize; 1223 public: 1224 explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {} 1225 void do_thread(Thread* thread) override { 1226 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread); 1227 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name()); 1228 gclab->retire(); 1229 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) { 1230 ShenandoahThreadLocalData::set_gclab_size(thread, 0); 1231 } 1232 1233 if (ShenandoahHeap::heap()->mode()->is_generational()) { 1234 PLAB* plab = ShenandoahThreadLocalData::plab(thread); 1235 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name()); 1236 1237 // There are two reasons to retire all plabs between old-gen evacuation passes. 1238 // 1. We need to make the plab memory parsable by remembered-set scanning. 1239 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region 1240 ShenandoahGenerationalHeap::heap()->retire_plab(plab, thread); 1241 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) { 1242 ShenandoahThreadLocalData::set_plab_size(thread, 0); 1243 } 1244 } 1245 } 1246 }; 1247 1248 class ShenandoahGCStatePropagatorHandshakeClosure : public HandshakeClosure { 1249 public: 1250 explicit ShenandoahGCStatePropagatorHandshakeClosure(char gc_state) : 1251 HandshakeClosure("Shenandoah GC State Change"), 1252 _gc_state(gc_state) {} 1253 1254 void do_thread(Thread* thread) override { 1255 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state); 1256 } 1257 private: 1258 char _gc_state; 1259 }; 1260 1261 class ShenandoahPrepareForUpdateRefsHandshakeClosure : public HandshakeClosure { 1262 public: 1263 explicit ShenandoahPrepareForUpdateRefsHandshakeClosure(char gc_state) : 1264 HandshakeClosure("Shenandoah Prepare for Update Refs"), 1265 _retire(ResizeTLAB), _propagator(gc_state) {} 1266 1267 void do_thread(Thread* thread) override { 1268 _propagator.do_thread(thread); 1269 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) { 1270 _retire.do_thread(thread); 1271 } 1272 } 1273 private: 1274 ShenandoahRetireGCLABClosure _retire; 1275 ShenandoahGCStatePropagatorHandshakeClosure _propagator; 1276 }; 1277 1278 void ShenandoahHeap::evacuate_collection_set(bool concurrent) { 1279 ShenandoahEvacuationTask task(this, _collection_set, concurrent); 1280 workers()->run_task(&task); 1281 } 1282 1283 void ShenandoahHeap::concurrent_prepare_for_update_refs() { 1284 { 1285 // Java threads take this lock while they are being attached and added to the list of thread. 1286 // If another thread holds this lock before we update the gc state, it will receive a stale 1287 // gc state, but they will have been added to the list of java threads and so will be corrected 1288 // by the following handshake. 1289 MutexLocker lock(Threads_lock); 1290 1291 // A cancellation at this point means the degenerated cycle must resume from update-refs. 1292 set_gc_state_concurrent(EVACUATION, false); 1293 set_gc_state_concurrent(WEAK_ROOTS, false); 1294 set_gc_state_concurrent(UPDATE_REFS, true); 1295 } 1296 1297 // This will propagate the gc state and retire gclabs and plabs for threads that require it. 1298 ShenandoahPrepareForUpdateRefsHandshakeClosure prepare_for_update_refs(_gc_state.raw_value()); 1299 1300 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately. 1301 Threads::non_java_threads_do(&prepare_for_update_refs); 1302 1303 // Now retire gclabs and plabs and propagate gc_state for mutator threads 1304 Handshake::execute(&prepare_for_update_refs); 1305 1306 _update_refs_iterator.reset(); 1307 } 1308 1309 class ShenandoahCompositeHandshakeClosure : public HandshakeClosure { 1310 HandshakeClosure* _handshake_1; 1311 HandshakeClosure* _handshake_2; 1312 public: 1313 ShenandoahCompositeHandshakeClosure(HandshakeClosure* handshake_1, HandshakeClosure* handshake_2) : 1314 HandshakeClosure(handshake_2->name()), 1315 _handshake_1(handshake_1), _handshake_2(handshake_2) {} 1316 1317 void do_thread(Thread* thread) override { 1318 _handshake_1->do_thread(thread); 1319 _handshake_2->do_thread(thread); 1320 } 1321 }; 1322 1323 void ShenandoahHeap::concurrent_final_roots(HandshakeClosure* handshake_closure) { 1324 { 1325 assert(!is_evacuation_in_progress(), "Should not evacuate for abbreviated or old cycles"); 1326 MutexLocker lock(Threads_lock); 1327 set_gc_state_concurrent(WEAK_ROOTS, false); 1328 } 1329 1330 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value()); 1331 Threads::non_java_threads_do(&propagator); 1332 if (handshake_closure == nullptr) { 1333 Handshake::execute(&propagator); 1334 } else { 1335 ShenandoahCompositeHandshakeClosure composite(&propagator, handshake_closure); 1336 Handshake::execute(&composite); 1337 } 1338 } 1339 1340 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) { 1341 assert(thread == Thread::current(), "Expected thread parameter to be current thread."); 1342 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) { 1343 // This thread went through the OOM during evac protocol. It is safe to return 1344 // the forward pointer. It must not attempt to evacuate any other objects. 1345 return ShenandoahBarrierSet::resolve_forwarded(p); 1346 } 1347 1348 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope"); 1349 1350 ShenandoahHeapRegion* r = heap_region_containing(p); 1351 assert(!r->is_humongous(), "never evacuate humongous objects"); 1352 1353 ShenandoahAffiliation target_gen = r->affiliation(); 1354 return try_evacuate_object(p, thread, r, target_gen); 1355 } 1356 1357 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region, 1358 ShenandoahAffiliation target_gen) { 1359 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode"); 1360 assert(from_region->is_young(), "Only expect evacuations from young in this mode"); 1361 bool alloc_from_lab = true; 1362 HeapWord* copy = nullptr; 1363 1364 markWord mark = p->mark(); 1365 if (ShenandoahForwarding::is_forwarded(mark)) { 1366 return ShenandoahForwarding::get_forwardee(p); 1367 } 1368 size_t old_size = ShenandoahForwarding::size(p); 1369 size_t size = p->copy_size(old_size, mark); 1370 1371 #ifdef ASSERT 1372 if (ShenandoahOOMDuringEvacALot && 1373 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call 1374 copy = nullptr; 1375 } else { 1376 #endif 1377 if (UseTLAB) { 1378 copy = allocate_from_gclab(thread, size); 1379 } 1380 if (copy == nullptr) { 1381 // If we failed to allocate in LAB, we'll try a shared allocation. 1382 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen); 1383 copy = allocate_memory(req); 1384 alloc_from_lab = false; 1385 } 1386 #ifdef ASSERT 1387 } 1388 #endif 1389 1390 if (copy == nullptr) { 1391 control_thread()->handle_alloc_failure_evac(size); 1392 1393 _oom_evac_handler.handle_out_of_memory_during_evacuation(); 1394 1395 return ShenandoahBarrierSet::resolve_forwarded(p); 1396 } 1397 1398 // Copy the object: 1399 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, old_size); 1400 1401 // Try to install the new forwarding pointer. 1402 oop copy_val = cast_to_oop(copy); 1403 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val); 1404 if (result == copy_val) { 1405 // Successfully evacuated. Our copy is now the public one! 1406 copy_val->initialize_hash_if_necessary(p); 1407 ContinuationGCSupport::relativize_stack_chunk(copy_val); 1408 shenandoah_assert_correct(nullptr, copy_val); 1409 return copy_val; 1410 } else { 1411 // Failed to evacuate. We need to deal with the object that is left behind. Since this 1412 // new allocation is certainly after TAMS, it will be considered live in the next cycle. 1413 // But if it happens to contain references to evacuated regions, those references would 1414 // not get updated for this stale copy during this cycle, and we will crash while scanning 1415 // it the next cycle. 1416 if (alloc_from_lab) { 1417 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next 1418 // object will overwrite this stale copy, or the filler object on LAB retirement will 1419 // do this. 1420 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size); 1421 } else { 1422 // For non-LAB allocations, we have no way to retract the allocation, and 1423 // have to explicitly overwrite the copy with the filler object. With that overwrite, 1424 // we have to keep the fwdptr initialized and pointing to our (stale) copy. 1425 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size"); 1426 fill_with_object(copy, size); 1427 shenandoah_assert_correct(nullptr, copy_val); 1428 // For non-LAB allocations, the object has already been registered 1429 } 1430 shenandoah_assert_correct(nullptr, result); 1431 return result; 1432 } 1433 } 1434 1435 void ShenandoahHeap::trash_cset_regions() { 1436 ShenandoahHeapLocker locker(lock()); 1437 1438 ShenandoahCollectionSet* set = collection_set(); 1439 ShenandoahHeapRegion* r; 1440 set->clear_current_index(); 1441 while ((r = set->next()) != nullptr) { 1442 r->make_trash(); 1443 } 1444 collection_set()->clear(); 1445 } 1446 1447 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const { 1448 st->print_cr("Heap Regions:"); 1449 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start"); 1450 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set"); 1451 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start"); 1452 st->print_cr("UWM=update watermark, U=used"); 1453 st->print_cr("T=TLAB allocs, G=GCLAB allocs"); 1454 st->print_cr("S=shared allocs, L=live data"); 1455 st->print_cr("CP=critical pins"); 1456 1457 for (size_t i = 0; i < num_regions(); i++) { 1458 get_region(i)->print_on(st); 1459 } 1460 } 1461 1462 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) const { 1463 assert(start->is_humongous_start(), "reclaim regions starting with the first one"); 1464 assert(!start->has_live(), "liveness must be zero"); 1465 1466 // Do not try to get the size of this humongous object. STW collections will 1467 // have already unloaded classes, so an unmarked object may have a bad klass pointer. 1468 ShenandoahHeapRegion* region = start; 1469 size_t index = region->index(); 1470 do { 1471 assert(region->is_humongous(), "Expect correct humongous start or continuation"); 1472 assert(!region->is_cset(), "Humongous region should not be in collection set"); 1473 region->make_trash_immediate(); 1474 region = get_region(++index); 1475 } while (region != nullptr && region->is_humongous_continuation()); 1476 1477 // Return number of regions trashed 1478 return index - start->index(); 1479 } 1480 1481 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure { 1482 public: 1483 ShenandoahCheckCleanGCLABClosure() {} 1484 void do_thread(Thread* thread) { 1485 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread); 1486 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name()); 1487 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement"); 1488 1489 if (ShenandoahHeap::heap()->mode()->is_generational()) { 1490 PLAB* plab = ShenandoahThreadLocalData::plab(thread); 1491 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name()); 1492 assert(plab->words_remaining() == 0, "PLAB should not need retirement"); 1493 } 1494 } 1495 }; 1496 1497 void ShenandoahHeap::labs_make_parsable() { 1498 assert(UseTLAB, "Only call with UseTLAB"); 1499 1500 ShenandoahRetireGCLABClosure cl(false); 1501 1502 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 1503 ThreadLocalAllocBuffer& tlab = t->tlab(); 1504 tlab.make_parsable(); 1505 if (ZeroTLAB) { 1506 t->retire_tlab(); 1507 } 1508 cl.do_thread(t); 1509 } 1510 1511 workers()->threads_do(&cl); 1512 1513 if (safepoint_workers() != nullptr) { 1514 safepoint_workers()->threads_do(&cl); 1515 } 1516 } 1517 1518 void ShenandoahHeap::tlabs_retire(bool resize) { 1519 assert(UseTLAB, "Only call with UseTLAB"); 1520 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled"); 1521 1522 ThreadLocalAllocStats stats; 1523 1524 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 1525 t->retire_tlab(&stats); 1526 if (resize) { 1527 t->tlab().resize(); 1528 } 1529 } 1530 1531 stats.publish(); 1532 1533 #ifdef ASSERT 1534 ShenandoahCheckCleanGCLABClosure cl; 1535 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 1536 cl.do_thread(t); 1537 } 1538 workers()->threads_do(&cl); 1539 #endif 1540 } 1541 1542 void ShenandoahHeap::gclabs_retire(bool resize) { 1543 assert(UseTLAB, "Only call with UseTLAB"); 1544 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled"); 1545 1546 ShenandoahRetireGCLABClosure cl(resize); 1547 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 1548 cl.do_thread(t); 1549 } 1550 1551 workers()->threads_do(&cl); 1552 1553 if (safepoint_workers() != nullptr) { 1554 safepoint_workers()->threads_do(&cl); 1555 } 1556 } 1557 1558 // Returns size in bytes 1559 size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const { 1560 // Return the max allowed size, and let the allocation path 1561 // figure out the safe size for current allocation. 1562 return ShenandoahHeapRegion::max_tlab_size_bytes(); 1563 } 1564 1565 size_t ShenandoahHeap::max_tlab_size() const { 1566 // Returns size in words 1567 return ShenandoahHeapRegion::max_tlab_size_words(); 1568 } 1569 1570 void ShenandoahHeap::collect_as_vm_thread(GCCause::Cause cause) { 1571 // These requests are ignored because we can't easily have Shenandoah jump into 1572 // a synchronous (degenerated or full) cycle while it is in the middle of a concurrent 1573 // cycle. We _could_ cancel the concurrent cycle and then try to run a cycle directly 1574 // on the VM thread, but this would confuse the control thread mightily and doesn't 1575 // seem worth the trouble. Instead, we will have the caller thread run (and wait for) a 1576 // concurrent cycle in the prologue of the heap inspect/dump operation. This is how 1577 // other concurrent collectors in the JVM handle this scenario as well. 1578 assert(Thread::current()->is_VM_thread(), "Should be the VM thread"); 1579 guarantee(cause == GCCause::_heap_dump || cause == GCCause::_heap_inspection, "Invalid cause"); 1580 } 1581 1582 void ShenandoahHeap::collect(GCCause::Cause cause) { 1583 control_thread()->request_gc(cause); 1584 } 1585 1586 void ShenandoahHeap::do_full_collection(bool clear_all_soft_refs) { 1587 //assert(false, "Shouldn't need to do full collections"); 1588 } 1589 1590 HeapWord* ShenandoahHeap::block_start(const void* addr) const { 1591 ShenandoahHeapRegion* r = heap_region_containing(addr); 1592 if (r != nullptr) { 1593 return r->block_start(addr); 1594 } 1595 return nullptr; 1596 } 1597 1598 bool ShenandoahHeap::block_is_obj(const HeapWord* addr) const { 1599 ShenandoahHeapRegion* r = heap_region_containing(addr); 1600 return r->block_is_obj(addr); 1601 } 1602 1603 bool ShenandoahHeap::print_location(outputStream* st, void* addr) const { 1604 return BlockLocationPrinter<ShenandoahHeap>::print_location(st, addr); 1605 } 1606 1607 void ShenandoahHeap::prepare_for_verify() { 1608 if (SafepointSynchronize::is_at_safepoint() && UseTLAB) { 1609 labs_make_parsable(); 1610 } 1611 } 1612 1613 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const { 1614 if (_shenandoah_policy->is_at_shutdown()) { 1615 return; 1616 } 1617 1618 if (_control_thread != nullptr) { 1619 tcl->do_thread(_control_thread); 1620 } 1621 1622 if (_uncommit_thread != nullptr) { 1623 tcl->do_thread(_uncommit_thread); 1624 } 1625 1626 workers()->threads_do(tcl); 1627 if (_safepoint_workers != nullptr) { 1628 _safepoint_workers->threads_do(tcl); 1629 } 1630 } 1631 1632 void ShenandoahHeap::print_tracing_info() const { 1633 LogTarget(Info, gc, stats) lt; 1634 if (lt.is_enabled()) { 1635 ResourceMark rm; 1636 LogStream ls(lt); 1637 1638 phase_timings()->print_global_on(&ls); 1639 1640 ls.cr(); 1641 ls.cr(); 1642 1643 shenandoah_policy()->print_gc_stats(&ls); 1644 1645 ls.cr(); 1646 ls.cr(); 1647 } 1648 } 1649 1650 void ShenandoahHeap::set_gc_generation(ShenandoahGeneration* generation) { 1651 shenandoah_assert_control_or_vm_thread_at_safepoint(); 1652 _gc_generation = generation; 1653 } 1654 1655 // Active generation may only be set by the VM thread at a safepoint. 1656 void ShenandoahHeap::set_active_generation() { 1657 assert(Thread::current()->is_VM_thread(), "Only the VM Thread"); 1658 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint!"); 1659 assert(_gc_generation != nullptr, "Will set _active_generation to nullptr"); 1660 _active_generation = _gc_generation; 1661 } 1662 1663 void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) { 1664 shenandoah_policy()->record_collection_cause(cause); 1665 1666 const GCCause::Cause current = gc_cause(); 1667 assert(current == GCCause::_no_gc, "Over-writing cause: %s, with: %s", 1668 GCCause::to_string(current), GCCause::to_string(cause)); 1669 assert(_gc_generation == nullptr, "Over-writing _gc_generation"); 1670 1671 set_gc_cause(cause); 1672 set_gc_generation(generation); 1673 1674 generation->heuristics()->record_cycle_start(); 1675 } 1676 1677 void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) { 1678 assert(gc_cause() != GCCause::_no_gc, "cause wasn't set"); 1679 assert(_gc_generation != nullptr, "_gc_generation wasn't set"); 1680 1681 generation->heuristics()->record_cycle_end(); 1682 if (mode()->is_generational() && generation->is_global()) { 1683 // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well 1684 young_generation()->heuristics()->record_cycle_end(); 1685 old_generation()->heuristics()->record_cycle_end(); 1686 } 1687 1688 set_gc_generation(nullptr); 1689 set_gc_cause(GCCause::_no_gc); 1690 } 1691 1692 void ShenandoahHeap::verify(VerifyOption vo) { 1693 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) { 1694 if (ShenandoahVerify) { 1695 verifier()->verify_generic(vo); 1696 } else { 1697 // TODO: Consider allocating verification bitmaps on demand, 1698 // and turn this on unconditionally. 1699 } 1700 } 1701 } 1702 size_t ShenandoahHeap::tlab_capacity(Thread *thr) const { 1703 return _free_set->capacity(); 1704 } 1705 1706 class ObjectIterateScanRootClosure : public BasicOopIterateClosure { 1707 private: 1708 MarkBitMap* _bitmap; 1709 ShenandoahScanObjectStack* _oop_stack; 1710 ShenandoahHeap* const _heap; 1711 ShenandoahMarkingContext* const _marking_context; 1712 1713 template <class T> 1714 void do_oop_work(T* p) { 1715 T o = RawAccess<>::oop_load(p); 1716 if (!CompressedOops::is_null(o)) { 1717 oop obj = CompressedOops::decode_not_null(o); 1718 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) { 1719 // There may be dead oops in weak roots in concurrent root phase, do not touch them. 1720 return; 1721 } 1722 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj); 1723 1724 assert(oopDesc::is_oop(obj), "must be a valid oop"); 1725 if (!_bitmap->is_marked(obj)) { 1726 _bitmap->mark(obj); 1727 _oop_stack->push(obj); 1728 } 1729 } 1730 } 1731 public: 1732 ObjectIterateScanRootClosure(MarkBitMap* bitmap, ShenandoahScanObjectStack* oop_stack) : 1733 _bitmap(bitmap), _oop_stack(oop_stack), _heap(ShenandoahHeap::heap()), 1734 _marking_context(_heap->marking_context()) {} 1735 void do_oop(oop* p) { do_oop_work(p); } 1736 void do_oop(narrowOop* p) { do_oop_work(p); } 1737 }; 1738 1739 /* 1740 * This is public API, used in preparation of object_iterate(). 1741 * Since we don't do linear scan of heap in object_iterate() (see comment below), we don't 1742 * need to make the heap parsable. For Shenandoah-internal linear heap scans that we can 1743 * control, we call SH::tlabs_retire, SH::gclabs_retire. 1744 */ 1745 void ShenandoahHeap::ensure_parsability(bool retire_tlabs) { 1746 // No-op. 1747 } 1748 1749 /* 1750 * Iterates objects in the heap. This is public API, used for, e.g., heap dumping. 1751 * 1752 * We cannot safely iterate objects by doing a linear scan at random points in time. Linear 1753 * scanning needs to deal with dead objects, which may have dead Klass* pointers (e.g. 1754 * calling oopDesc::size() would crash) or dangling reference fields (crashes) etc. Linear 1755 * scanning therefore depends on having a valid marking bitmap to support it. However, we only 1756 * have a valid marking bitmap after successful marking. In particular, we *don't* have a valid 1757 * marking bitmap during marking, after aborted marking or during/after cleanup (when we just 1758 * wiped the bitmap in preparation for next marking). 1759 * 1760 * For all those reasons, we implement object iteration as a single marking traversal, reporting 1761 * objects as we mark+traverse through the heap, starting from GC roots. JVMTI IterateThroughHeap 1762 * is allowed to report dead objects, but is not required to do so. 1763 */ 1764 void ShenandoahHeap::object_iterate(ObjectClosure* cl) { 1765 // Reset bitmap 1766 if (!prepare_aux_bitmap_for_iteration()) 1767 return; 1768 1769 ShenandoahScanObjectStack oop_stack; 1770 ObjectIterateScanRootClosure oops(&_aux_bit_map, &oop_stack); 1771 // Seed the stack with root scan 1772 scan_roots_for_iteration(&oop_stack, &oops); 1773 1774 // Work through the oop stack to traverse heap 1775 while (! oop_stack.is_empty()) { 1776 oop obj = oop_stack.pop(); 1777 assert(oopDesc::is_oop(obj), "must be a valid oop"); 1778 cl->do_object(obj); 1779 obj->oop_iterate(&oops); 1780 } 1781 1782 assert(oop_stack.is_empty(), "should be empty"); 1783 // Reclaim bitmap 1784 reclaim_aux_bitmap_for_iteration(); 1785 } 1786 1787 bool ShenandoahHeap::prepare_aux_bitmap_for_iteration() { 1788 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints"); 1789 1790 if (!_aux_bitmap_region_special && !os::commit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size(), false)) { 1791 log_warning(gc)("Could not commit native memory for auxiliary marking bitmap for heap iteration"); 1792 return false; 1793 } 1794 // Reset bitmap 1795 _aux_bit_map.clear(); 1796 return true; 1797 } 1798 1799 void ShenandoahHeap::scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops) { 1800 // Process GC roots according to current GC cycle 1801 // This populates the work stack with initial objects 1802 // It is important to relinquish the associated locks before diving 1803 // into heap dumper 1804 uint n_workers = safepoint_workers() != nullptr ? safepoint_workers()->active_workers() : 1; 1805 ShenandoahHeapIterationRootScanner rp(n_workers); 1806 rp.roots_do(oops); 1807 } 1808 1809 void ShenandoahHeap::reclaim_aux_bitmap_for_iteration() { 1810 if (!_aux_bitmap_region_special && !os::uncommit_memory((char*)_aux_bitmap_region.start(), _aux_bitmap_region.byte_size())) { 1811 log_warning(gc)("Could not uncommit native memory for auxiliary marking bitmap for heap iteration"); 1812 } 1813 } 1814 1815 // Closure for parallelly iterate objects 1816 class ShenandoahObjectIterateParScanClosure : public BasicOopIterateClosure { 1817 private: 1818 MarkBitMap* _bitmap; 1819 ShenandoahObjToScanQueue* _queue; 1820 ShenandoahHeap* const _heap; 1821 ShenandoahMarkingContext* const _marking_context; 1822 1823 template <class T> 1824 void do_oop_work(T* p) { 1825 T o = RawAccess<>::oop_load(p); 1826 if (!CompressedOops::is_null(o)) { 1827 oop obj = CompressedOops::decode_not_null(o); 1828 if (_heap->is_concurrent_weak_root_in_progress() && !_marking_context->is_marked(obj)) { 1829 // There may be dead oops in weak roots in concurrent root phase, do not touch them. 1830 return; 1831 } 1832 obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj); 1833 1834 assert(oopDesc::is_oop(obj), "Must be a valid oop"); 1835 if (_bitmap->par_mark(obj)) { 1836 _queue->push(ShenandoahMarkTask(obj)); 1837 } 1838 } 1839 } 1840 public: 1841 ShenandoahObjectIterateParScanClosure(MarkBitMap* bitmap, ShenandoahObjToScanQueue* q) : 1842 _bitmap(bitmap), _queue(q), _heap(ShenandoahHeap::heap()), 1843 _marking_context(_heap->marking_context()) {} 1844 void do_oop(oop* p) { do_oop_work(p); } 1845 void do_oop(narrowOop* p) { do_oop_work(p); } 1846 }; 1847 1848 // Object iterator for parallel heap iteraion. 1849 // The root scanning phase happenes in construction as a preparation of 1850 // parallel marking queues. 1851 // Every worker processes it's own marking queue. work-stealing is used 1852 // to balance workload. 1853 class ShenandoahParallelObjectIterator : public ParallelObjectIteratorImpl { 1854 private: 1855 uint _num_workers; 1856 bool _init_ready; 1857 MarkBitMap* _aux_bit_map; 1858 ShenandoahHeap* _heap; 1859 ShenandoahScanObjectStack _roots_stack; // global roots stack 1860 ShenandoahObjToScanQueueSet* _task_queues; 1861 public: 1862 ShenandoahParallelObjectIterator(uint num_workers, MarkBitMap* bitmap) : 1863 _num_workers(num_workers), 1864 _init_ready(false), 1865 _aux_bit_map(bitmap), 1866 _heap(ShenandoahHeap::heap()) { 1867 // Initialize bitmap 1868 _init_ready = _heap->prepare_aux_bitmap_for_iteration(); 1869 if (!_init_ready) { 1870 return; 1871 } 1872 1873 ObjectIterateScanRootClosure oops(_aux_bit_map, &_roots_stack); 1874 _heap->scan_roots_for_iteration(&_roots_stack, &oops); 1875 1876 _init_ready = prepare_worker_queues(); 1877 } 1878 1879 ~ShenandoahParallelObjectIterator() { 1880 // Reclaim bitmap 1881 _heap->reclaim_aux_bitmap_for_iteration(); 1882 // Reclaim queue for workers 1883 if (_task_queues!= nullptr) { 1884 for (uint i = 0; i < _num_workers; ++i) { 1885 ShenandoahObjToScanQueue* q = _task_queues->queue(i); 1886 if (q != nullptr) { 1887 delete q; 1888 _task_queues->register_queue(i, nullptr); 1889 } 1890 } 1891 delete _task_queues; 1892 _task_queues = nullptr; 1893 } 1894 } 1895 1896 virtual void object_iterate(ObjectClosure* cl, uint worker_id) { 1897 if (_init_ready) { 1898 object_iterate_parallel(cl, worker_id, _task_queues); 1899 } 1900 } 1901 1902 private: 1903 // Divide global root_stack into worker queues 1904 bool prepare_worker_queues() { 1905 _task_queues = new ShenandoahObjToScanQueueSet((int) _num_workers); 1906 // Initialize queues for every workers 1907 for (uint i = 0; i < _num_workers; ++i) { 1908 ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue(); 1909 _task_queues->register_queue(i, task_queue); 1910 } 1911 // Divide roots among the workers. Assume that object referencing distribution 1912 // is related with root kind, use round-robin to make every worker have same chance 1913 // to process every kind of roots 1914 size_t roots_num = _roots_stack.size(); 1915 if (roots_num == 0) { 1916 // No work to do 1917 return false; 1918 } 1919 1920 for (uint j = 0; j < roots_num; j++) { 1921 uint stack_id = j % _num_workers; 1922 oop obj = _roots_stack.pop(); 1923 _task_queues->queue(stack_id)->push(ShenandoahMarkTask(obj)); 1924 } 1925 return true; 1926 } 1927 1928 void object_iterate_parallel(ObjectClosure* cl, 1929 uint worker_id, 1930 ShenandoahObjToScanQueueSet* queue_set) { 1931 assert(SafepointSynchronize::is_at_safepoint(), "safe iteration is only available during safepoints"); 1932 assert(queue_set != nullptr, "task queue must not be null"); 1933 1934 ShenandoahObjToScanQueue* q = queue_set->queue(worker_id); 1935 assert(q != nullptr, "object iterate queue must not be null"); 1936 1937 ShenandoahMarkTask t; 1938 ShenandoahObjectIterateParScanClosure oops(_aux_bit_map, q); 1939 1940 // Work through the queue to traverse heap. 1941 // Steal when there is no task in queue. 1942 while (q->pop(t) || queue_set->steal(worker_id, t)) { 1943 oop obj = t.obj(); 1944 assert(oopDesc::is_oop(obj), "must be a valid oop"); 1945 cl->do_object(obj); 1946 obj->oop_iterate(&oops); 1947 } 1948 assert(q->is_empty(), "should be empty"); 1949 } 1950 }; 1951 1952 ParallelObjectIteratorImpl* ShenandoahHeap::parallel_object_iterator(uint workers) { 1953 return new ShenandoahParallelObjectIterator(workers, &_aux_bit_map); 1954 } 1955 1956 // Keep alive an object that was loaded with AS_NO_KEEPALIVE. 1957 void ShenandoahHeap::keep_alive(oop obj) { 1958 if (is_concurrent_mark_in_progress() && (obj != nullptr)) { 1959 ShenandoahBarrierSet::barrier_set()->enqueue(obj); 1960 } 1961 } 1962 1963 void ShenandoahHeap::heap_region_iterate(ShenandoahHeapRegionClosure* blk) const { 1964 for (size_t i = 0; i < num_regions(); i++) { 1965 ShenandoahHeapRegion* current = get_region(i); 1966 blk->heap_region_do(current); 1967 } 1968 } 1969 1970 class ShenandoahParallelHeapRegionTask : public WorkerTask { 1971 private: 1972 ShenandoahHeap* const _heap; 1973 ShenandoahHeapRegionClosure* const _blk; 1974 size_t const _stride; 1975 1976 shenandoah_padding(0); 1977 volatile size_t _index; 1978 shenandoah_padding(1); 1979 1980 public: 1981 ShenandoahParallelHeapRegionTask(ShenandoahHeapRegionClosure* blk, size_t stride) : 1982 WorkerTask("Shenandoah Parallel Region Operation"), 1983 _heap(ShenandoahHeap::heap()), _blk(blk), _stride(stride), _index(0) {} 1984 1985 void work(uint worker_id) { 1986 ShenandoahParallelWorkerSession worker_session(worker_id); 1987 size_t stride = _stride; 1988 1989 size_t max = _heap->num_regions(); 1990 while (Atomic::load(&_index) < max) { 1991 size_t cur = Atomic::fetch_then_add(&_index, stride, memory_order_relaxed); 1992 size_t start = cur; 1993 size_t end = MIN2(cur + stride, max); 1994 if (start >= max) break; 1995 1996 for (size_t i = cur; i < end; i++) { 1997 ShenandoahHeapRegion* current = _heap->get_region(i); 1998 _blk->heap_region_do(current); 1999 } 2000 } 2001 } 2002 }; 2003 2004 void ShenandoahHeap::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const { 2005 assert(blk->is_thread_safe(), "Only thread-safe closures here"); 2006 const uint active_workers = workers()->active_workers(); 2007 const size_t n_regions = num_regions(); 2008 size_t stride = ShenandoahParallelRegionStride; 2009 if (stride == 0 && active_workers > 1) { 2010 // Automatically derive the stride to balance the work between threads 2011 // evenly. Do not try to split work if below the reasonable threshold. 2012 constexpr size_t threshold = 4096; 2013 stride = n_regions <= threshold ? 2014 threshold : 2015 (n_regions + active_workers - 1) / active_workers; 2016 } 2017 2018 if (n_regions > stride && active_workers > 1) { 2019 ShenandoahParallelHeapRegionTask task(blk, stride); 2020 workers()->run_task(&task); 2021 } else { 2022 heap_region_iterate(blk); 2023 } 2024 } 2025 2026 class ShenandoahRendezvousHandshakeClosure : public HandshakeClosure { 2027 public: 2028 inline ShenandoahRendezvousHandshakeClosure(const char* name) : HandshakeClosure(name) {} 2029 inline void do_thread(Thread* thread) {} 2030 }; 2031 2032 void ShenandoahHeap::rendezvous_threads(const char* name) { 2033 ShenandoahRendezvousHandshakeClosure cl(name); 2034 Handshake::execute(&cl); 2035 } 2036 2037 void ShenandoahHeap::recycle_trash() { 2038 free_set()->recycle_trash(); 2039 } 2040 2041 void ShenandoahHeap::do_class_unloading() { 2042 _unloader.unload(); 2043 if (mode()->is_generational()) { 2044 old_generation()->set_parsable(false); 2045 } 2046 } 2047 2048 void ShenandoahHeap::stw_weak_refs(bool full_gc) { 2049 // Weak refs processing 2050 ShenandoahPhaseTimings::Phase phase = full_gc ? ShenandoahPhaseTimings::full_gc_weakrefs 2051 : ShenandoahPhaseTimings::degen_gc_weakrefs; 2052 ShenandoahTimingsTracker t(phase); 2053 ShenandoahGCWorkerPhase worker_phase(phase); 2054 shenandoah_assert_generations_reconciled(); 2055 gc_generation()->ref_processor()->process_references(phase, workers(), false /* concurrent */); 2056 } 2057 2058 void ShenandoahHeap::prepare_update_heap_references() { 2059 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint"); 2060 2061 // Evacuation is over, no GCLABs are needed anymore. GCLABs are under URWM, so we need to 2062 // make them parsable for update code to work correctly. Plus, we can compute new sizes 2063 // for future GCLABs here. 2064 if (UseTLAB) { 2065 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_init_update_refs_manage_gclabs); 2066 gclabs_retire(ResizeTLAB); 2067 } 2068 2069 _update_refs_iterator.reset(); 2070 } 2071 2072 void ShenandoahHeap::propagate_gc_state_to_all_threads() { 2073 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint"); 2074 if (_gc_state_changed) { 2075 ShenandoahGCStatePropagatorHandshakeClosure propagator(_gc_state.raw_value()); 2076 Threads::threads_do(&propagator); 2077 _gc_state_changed = false; 2078 } 2079 } 2080 2081 void ShenandoahHeap::set_gc_state_at_safepoint(uint mask, bool value) { 2082 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at Shenandoah safepoint"); 2083 _gc_state.set_cond(mask, value); 2084 _gc_state_changed = true; 2085 } 2086 2087 void ShenandoahHeap::set_gc_state_concurrent(uint mask, bool value) { 2088 // Holding the thread lock here assures that any thread created after we change the gc 2089 // state will have the correct state. It also prevents attaching threads from seeing 2090 // an inconsistent state. See ShenandoahBarrierSet::on_thread_attach for reference. Established 2091 // threads will use their thread local copy of the gc state (changed by a handshake, or on a 2092 // safepoint). 2093 assert(Threads_lock->is_locked(), "Must hold thread lock for concurrent gc state change"); 2094 _gc_state.set_cond(mask, value); 2095 } 2096 2097 void ShenandoahHeap::set_concurrent_young_mark_in_progress(bool in_progress) { 2098 uint mask; 2099 assert(!has_forwarded_objects(), "Young marking is not concurrent with evacuation"); 2100 if (!in_progress && is_concurrent_old_mark_in_progress()) { 2101 assert(mode()->is_generational(), "Only generational GC has old marking"); 2102 assert(_gc_state.is_set(MARKING), "concurrent_old_marking_in_progress implies MARKING"); 2103 // If old-marking is in progress when we turn off YOUNG_MARKING, leave MARKING (and OLD_MARKING) on 2104 mask = YOUNG_MARKING; 2105 } else { 2106 mask = MARKING | YOUNG_MARKING; 2107 } 2108 set_gc_state_at_safepoint(mask, in_progress); 2109 manage_satb_barrier(in_progress); 2110 } 2111 2112 void ShenandoahHeap::set_concurrent_old_mark_in_progress(bool in_progress) { 2113 #ifdef ASSERT 2114 // has_forwarded_objects() iff UPDATE_REFS or EVACUATION 2115 bool has_forwarded = has_forwarded_objects(); 2116 bool updating_or_evacuating = _gc_state.is_set(UPDATE_REFS | EVACUATION); 2117 bool evacuating = _gc_state.is_set(EVACUATION); 2118 assert ((has_forwarded == updating_or_evacuating) || (evacuating && !has_forwarded && collection_set()->is_empty()), 2119 "Updating or evacuating iff has forwarded objects, or if evacuation phase is promoting in place without forwarding"); 2120 #endif 2121 if (!in_progress && is_concurrent_young_mark_in_progress()) { 2122 // If young-marking is in progress when we turn off OLD_MARKING, leave MARKING (and YOUNG_MARKING) on 2123 assert(_gc_state.is_set(MARKING), "concurrent_young_marking_in_progress implies MARKING"); 2124 set_gc_state_at_safepoint(OLD_MARKING, in_progress); 2125 } else { 2126 set_gc_state_at_safepoint(MARKING | OLD_MARKING, in_progress); 2127 } 2128 manage_satb_barrier(in_progress); 2129 } 2130 2131 bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const { 2132 return old_generation()->is_preparing_for_mark(); 2133 } 2134 2135 void ShenandoahHeap::manage_satb_barrier(bool active) { 2136 if (is_concurrent_mark_in_progress()) { 2137 // Ignore request to deactivate barrier while concurrent mark is in progress. 2138 // Do not attempt to re-activate the barrier if it is already active. 2139 if (active && !ShenandoahBarrierSet::satb_mark_queue_set().is_active()) { 2140 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active); 2141 } 2142 } else { 2143 // No concurrent marking is in progress so honor request to deactivate, 2144 // but only if the barrier is already active. 2145 if (!active && ShenandoahBarrierSet::satb_mark_queue_set().is_active()) { 2146 ShenandoahBarrierSet::satb_mark_queue_set().set_active_all_threads(active, !active); 2147 } 2148 } 2149 } 2150 2151 void ShenandoahHeap::set_evacuation_in_progress(bool in_progress) { 2152 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Only call this at safepoint"); 2153 set_gc_state_at_safepoint(EVACUATION, in_progress); 2154 } 2155 2156 void ShenandoahHeap::set_concurrent_strong_root_in_progress(bool in_progress) { 2157 if (in_progress) { 2158 _concurrent_strong_root_in_progress.set(); 2159 } else { 2160 _concurrent_strong_root_in_progress.unset(); 2161 } 2162 } 2163 2164 void ShenandoahHeap::set_concurrent_weak_root_in_progress(bool cond) { 2165 set_gc_state_at_safepoint(WEAK_ROOTS, cond); 2166 } 2167 2168 GCTracer* ShenandoahHeap::tracer() { 2169 return shenandoah_policy()->tracer(); 2170 } 2171 2172 size_t ShenandoahHeap::tlab_used(Thread* thread) const { 2173 return _free_set->used(); 2174 } 2175 2176 bool ShenandoahHeap::try_cancel_gc(GCCause::Cause cause) { 2177 const GCCause::Cause prev = _cancelled_gc.xchg(cause); 2178 return prev == GCCause::_no_gc || prev == GCCause::_shenandoah_concurrent_gc; 2179 } 2180 2181 void ShenandoahHeap::cancel_concurrent_mark() { 2182 if (mode()->is_generational()) { 2183 young_generation()->cancel_marking(); 2184 old_generation()->cancel_marking(); 2185 } 2186 2187 global_generation()->cancel_marking(); 2188 2189 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking(); 2190 } 2191 2192 bool ShenandoahHeap::cancel_gc(GCCause::Cause cause) { 2193 if (try_cancel_gc(cause)) { 2194 FormatBuffer<> msg("Cancelling GC: %s", GCCause::to_string(cause)); 2195 log_info(gc,thread)("%s", msg.buffer()); 2196 Events::log(Thread::current(), "%s", msg.buffer()); 2197 _cancel_requested_time = os::elapsedTime(); 2198 return true; 2199 } 2200 return false; 2201 } 2202 2203 uint ShenandoahHeap::max_workers() { 2204 return _max_workers; 2205 } 2206 2207 void ShenandoahHeap::stop() { 2208 // The shutdown sequence should be able to terminate when GC is running. 2209 2210 // Step 0. Notify policy to disable event recording and prevent visiting gc threads during shutdown 2211 _shenandoah_policy->record_shutdown(); 2212 2213 // Step 1. Stop reporting on gc thread cpu utilization 2214 mmu_tracker()->stop(); 2215 2216 // Step 2. Wait until GC worker exits normally (this will cancel any ongoing GC). 2217 control_thread()->stop(); 2218 2219 // Stop 4. Shutdown uncommit thread. 2220 if (_uncommit_thread != nullptr) { 2221 _uncommit_thread->stop(); 2222 } 2223 } 2224 2225 void ShenandoahHeap::stw_unload_classes(bool full_gc) { 2226 if (!unload_classes()) return; 2227 ClassUnloadingContext ctx(_workers->active_workers(), 2228 true /* unregister_nmethods_during_purge */, 2229 false /* lock_nmethod_free_separately */); 2230 2231 // Unload classes and purge SystemDictionary. 2232 { 2233 ShenandoahPhaseTimings::Phase phase = full_gc ? 2234 ShenandoahPhaseTimings::full_gc_purge_class_unload : 2235 ShenandoahPhaseTimings::degen_gc_purge_class_unload; 2236 ShenandoahIsAliveSelector is_alive; 2237 { 2238 CodeCache::UnlinkingScope scope(is_alive.is_alive_closure()); 2239 ShenandoahGCPhase gc_phase(phase); 2240 ShenandoahGCWorkerPhase worker_phase(phase); 2241 bool unloading_occurred = SystemDictionary::do_unloading(gc_timer()); 2242 2243 // Clean JVMCI metadata handles. 2244 JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred)); 2245 2246 uint num_workers = _workers->active_workers(); 2247 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred); 2248 _workers->run_task(&unlink_task); 2249 } 2250 // Release unloaded nmethods's memory. 2251 ClassUnloadingContext::context()->purge_and_free_nmethods(); 2252 } 2253 2254 { 2255 ShenandoahGCPhase phase(full_gc ? 2256 ShenandoahPhaseTimings::full_gc_purge_cldg : 2257 ShenandoahPhaseTimings::degen_gc_purge_cldg); 2258 ClassLoaderDataGraph::purge(true /* at_safepoint */); 2259 } 2260 // Resize and verify metaspace 2261 MetaspaceGC::compute_new_size(); 2262 DEBUG_ONLY(MetaspaceUtils::verify();) 2263 } 2264 2265 // Weak roots are either pre-evacuated (final mark) or updated (final update refs), 2266 // so they should not have forwarded oops. 2267 // However, we do need to "null" dead oops in the roots, if can not be done 2268 // in concurrent cycles. 2269 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) { 2270 uint num_workers = _workers->active_workers(); 2271 ShenandoahPhaseTimings::Phase timing_phase = full_gc ? 2272 ShenandoahPhaseTimings::full_gc_purge_weak_par : 2273 ShenandoahPhaseTimings::degen_gc_purge_weak_par; 2274 ShenandoahGCPhase phase(timing_phase); 2275 ShenandoahGCWorkerPhase worker_phase(timing_phase); 2276 // Cleanup weak roots 2277 if (has_forwarded_objects()) { 2278 ShenandoahForwardedIsAliveClosure is_alive; 2279 ShenandoahNonConcUpdateRefsClosure keep_alive; 2280 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure> 2281 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers); 2282 _workers->run_task(&cleaning_task); 2283 } else { 2284 ShenandoahIsAliveClosure is_alive; 2285 #ifdef ASSERT 2286 ShenandoahAssertNotForwardedClosure verify_cl; 2287 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure> 2288 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers); 2289 #else 2290 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure> 2291 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers); 2292 #endif 2293 _workers->run_task(&cleaning_task); 2294 } 2295 } 2296 2297 void ShenandoahHeap::parallel_cleaning(bool full_gc) { 2298 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint"); 2299 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC"); 2300 ShenandoahGCPhase phase(full_gc ? 2301 ShenandoahPhaseTimings::full_gc_purge : 2302 ShenandoahPhaseTimings::degen_gc_purge); 2303 stw_weak_refs(full_gc); 2304 stw_process_weak_roots(full_gc); 2305 stw_unload_classes(full_gc); 2306 } 2307 2308 void ShenandoahHeap::set_has_forwarded_objects(bool cond) { 2309 set_gc_state_at_safepoint(HAS_FORWARDED, cond); 2310 } 2311 2312 void ShenandoahHeap::set_unload_classes(bool uc) { 2313 _unload_classes.set_cond(uc); 2314 } 2315 2316 bool ShenandoahHeap::unload_classes() const { 2317 return _unload_classes.is_set(); 2318 } 2319 2320 address ShenandoahHeap::in_cset_fast_test_addr() { 2321 ShenandoahHeap* heap = ShenandoahHeap::heap(); 2322 assert(heap->collection_set() != nullptr, "Sanity"); 2323 return (address) heap->collection_set()->biased_map_address(); 2324 } 2325 2326 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() { 2327 if (mode()->is_generational()) { 2328 young_generation()->reset_bytes_allocated_since_gc_start(); 2329 old_generation()->reset_bytes_allocated_since_gc_start(); 2330 } 2331 2332 global_generation()->reset_bytes_allocated_since_gc_start(); 2333 } 2334 2335 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) { 2336 _degenerated_gc_in_progress.set_cond(in_progress); 2337 } 2338 2339 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) { 2340 _full_gc_in_progress.set_cond(in_progress); 2341 } 2342 2343 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) { 2344 assert (is_full_gc_in_progress(), "should be"); 2345 _full_gc_move_in_progress.set_cond(in_progress); 2346 } 2347 2348 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) { 2349 set_gc_state_at_safepoint(UPDATE_REFS, in_progress); 2350 } 2351 2352 void ShenandoahHeap::register_nmethod(nmethod* nm) { 2353 ShenandoahCodeRoots::register_nmethod(nm); 2354 } 2355 2356 void ShenandoahHeap::unregister_nmethod(nmethod* nm) { 2357 ShenandoahCodeRoots::unregister_nmethod(nm); 2358 } 2359 2360 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) { 2361 heap_region_containing(o)->record_pin(); 2362 } 2363 2364 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) { 2365 ShenandoahHeapRegion* r = heap_region_containing(o); 2366 assert(r != nullptr, "Sanity"); 2367 assert(r->pin_count() > 0, "Region %zu should have non-zero pins", r->index()); 2368 r->record_unpin(); 2369 } 2370 2371 void ShenandoahHeap::sync_pinned_region_status() { 2372 ShenandoahHeapLocker locker(lock()); 2373 2374 for (size_t i = 0; i < num_regions(); i++) { 2375 ShenandoahHeapRegion *r = get_region(i); 2376 if (r->is_active()) { 2377 if (r->is_pinned()) { 2378 if (r->pin_count() == 0) { 2379 r->make_unpinned(); 2380 } 2381 } else { 2382 if (r->pin_count() > 0) { 2383 r->make_pinned(); 2384 } 2385 } 2386 } 2387 } 2388 2389 assert_pinned_region_status(); 2390 } 2391 2392 #ifdef ASSERT 2393 void ShenandoahHeap::assert_pinned_region_status() { 2394 for (size_t i = 0; i < num_regions(); i++) { 2395 ShenandoahHeapRegion* r = get_region(i); 2396 shenandoah_assert_generations_reconciled(); 2397 if (gc_generation()->contains(r)) { 2398 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0), 2399 "Region %zu pinning status is inconsistent", i); 2400 } 2401 } 2402 } 2403 #endif 2404 2405 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const { 2406 return _gc_timer; 2407 } 2408 2409 void ShenandoahHeap::prepare_concurrent_roots() { 2410 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint"); 2411 assert(!is_stw_gc_in_progress(), "Only concurrent GC"); 2412 set_concurrent_strong_root_in_progress(!collection_set()->is_empty()); 2413 set_concurrent_weak_root_in_progress(true); 2414 if (unload_classes()) { 2415 _unloader.prepare(); 2416 } 2417 } 2418 2419 void ShenandoahHeap::finish_concurrent_roots() { 2420 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint"); 2421 assert(!is_stw_gc_in_progress(), "Only concurrent GC"); 2422 if (unload_classes()) { 2423 _unloader.finish(); 2424 } 2425 } 2426 2427 #ifdef ASSERT 2428 void ShenandoahHeap::assert_gc_workers(uint nworkers) { 2429 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity"); 2430 2431 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) { 2432 // Use ParallelGCThreads inside safepoints 2433 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u", 2434 ParallelGCThreads, nworkers); 2435 } else { 2436 // Use ConcGCThreads outside safepoints 2437 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u", 2438 ConcGCThreads, nworkers); 2439 } 2440 } 2441 #endif 2442 2443 ShenandoahVerifier* ShenandoahHeap::verifier() { 2444 guarantee(ShenandoahVerify, "Should be enabled"); 2445 assert (_verifier != nullptr, "sanity"); 2446 return _verifier; 2447 } 2448 2449 template<bool CONCURRENT> 2450 class ShenandoahUpdateHeapRefsTask : public WorkerTask { 2451 private: 2452 ShenandoahHeap* _heap; 2453 ShenandoahRegionIterator* _regions; 2454 public: 2455 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) : 2456 WorkerTask("Shenandoah Update References"), 2457 _heap(ShenandoahHeap::heap()), 2458 _regions(regions) { 2459 } 2460 2461 void work(uint worker_id) { 2462 if (CONCURRENT) { 2463 ShenandoahConcurrentWorkerSession worker_session(worker_id); 2464 ShenandoahSuspendibleThreadSetJoiner stsj; 2465 do_work<ShenandoahConcUpdateRefsClosure>(worker_id); 2466 } else { 2467 ShenandoahParallelWorkerSession worker_session(worker_id); 2468 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id); 2469 } 2470 } 2471 2472 private: 2473 template<class T> 2474 void do_work(uint worker_id) { 2475 if (CONCURRENT && (worker_id == 0)) { 2476 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the 2477 // results of evacuation. These reserves are no longer necessary because evacuation has completed. 2478 size_t cset_regions = _heap->collection_set()->count(); 2479 2480 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation 2481 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from 2482 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the 2483 // next GC cycle. 2484 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions); 2485 } 2486 // If !CONCURRENT, there's no value in expanding Mutator free set 2487 T cl; 2488 ShenandoahHeapRegion* r = _regions->next(); 2489 while (r != nullptr) { 2490 HeapWord* update_watermark = r->get_update_watermark(); 2491 assert (update_watermark >= r->bottom(), "sanity"); 2492 if (r->is_active() && !r->is_cset()) { 2493 _heap->marked_object_oop_iterate(r, &cl, update_watermark); 2494 if (ShenandoahPacing) { 2495 _heap->pacer()->report_update_refs(pointer_delta(update_watermark, r->bottom())); 2496 } 2497 } 2498 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) { 2499 return; 2500 } 2501 r = _regions->next(); 2502 } 2503 } 2504 }; 2505 2506 void ShenandoahHeap::update_heap_references(bool concurrent) { 2507 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC"); 2508 2509 if (concurrent) { 2510 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator); 2511 workers()->run_task(&task); 2512 } else { 2513 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator); 2514 workers()->run_task(&task); 2515 } 2516 } 2517 2518 void ShenandoahHeap::update_heap_region_states(bool concurrent) { 2519 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint"); 2520 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC"); 2521 2522 { 2523 ShenandoahGCPhase phase(concurrent ? 2524 ShenandoahPhaseTimings::final_update_refs_update_region_states : 2525 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states); 2526 2527 final_update_refs_update_region_states(); 2528 2529 assert_pinned_region_status(); 2530 } 2531 2532 { 2533 ShenandoahGCPhase phase(concurrent ? 2534 ShenandoahPhaseTimings::final_update_refs_trash_cset : 2535 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset); 2536 trash_cset_regions(); 2537 } 2538 } 2539 2540 void ShenandoahHeap::final_update_refs_update_region_states() { 2541 ShenandoahSynchronizePinnedRegionStates cl; 2542 parallel_heap_region_iterate(&cl); 2543 } 2544 2545 void ShenandoahHeap::rebuild_free_set(bool concurrent) { 2546 ShenandoahGCPhase phase(concurrent ? 2547 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset : 2548 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset); 2549 ShenandoahHeapLocker locker(lock()); 2550 size_t young_cset_regions, old_cset_regions; 2551 size_t first_old_region, last_old_region, old_region_count; 2552 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count); 2553 // If there are no old regions, first_old_region will be greater than last_old_region 2554 assert((first_old_region > last_old_region) || 2555 ((last_old_region + 1 - first_old_region >= old_region_count) && 2556 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()), 2557 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu", 2558 old_region_count, first_old_region, last_old_region); 2559 2560 if (mode()->is_generational()) { 2561 #ifdef ASSERT 2562 if (ShenandoahVerify) { 2563 verifier()->verify_before_rebuilding_free_set(); 2564 } 2565 #endif 2566 2567 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this 2568 // available for transfer to old. Note that transfer of humongous regions does not impact available. 2569 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap(); 2570 size_t allocation_runway = gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions); 2571 gen_heap->compute_old_generation_balance(allocation_runway, old_cset_regions); 2572 2573 // Total old_available may have been expanded to hold anticipated promotions. We trigger if the fragmented available 2574 // memory represents more than 16 regions worth of data. Note that fragmentation may increase when we promote regular 2575 // regions in place when many of these regular regions have an abundant amount of available memory within them. Fragmentation 2576 // will decrease as promote-by-copy consumes the available memory within these partially consumed regions. 2577 // 2578 // We consider old-gen to have excessive fragmentation if more than 12.5% of old-gen is free memory that resides 2579 // within partially consumed regions of memory. 2580 } 2581 // Rebuild free set based on adjusted generation sizes. 2582 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, old_region_count); 2583 2584 if (mode()->is_generational()) { 2585 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap(); 2586 ShenandoahOldGeneration* old_gen = gen_heap->old_generation(); 2587 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions()); 2588 } 2589 } 2590 2591 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) { 2592 size_t slice = r->index() / _bitmap_regions_per_slice; 2593 2594 size_t regions_from = _bitmap_regions_per_slice * slice; 2595 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1)); 2596 for (size_t g = regions_from; g < regions_to; g++) { 2597 assert (g / _bitmap_regions_per_slice == slice, "same slice"); 2598 if (skip_self && g == r->index()) continue; 2599 if (get_region(g)->is_committed()) { 2600 return true; 2601 } 2602 } 2603 return false; 2604 } 2605 2606 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) { 2607 shenandoah_assert_heaplocked(); 2608 2609 // Bitmaps in special regions do not need commits 2610 if (_bitmap_region_special) { 2611 return true; 2612 } 2613 2614 if (is_bitmap_slice_committed(r, true)) { 2615 // Some other region from the group is already committed, meaning the bitmap 2616 // slice is already committed, we exit right away. 2617 return true; 2618 } 2619 2620 // Commit the bitmap slice: 2621 size_t slice = r->index() / _bitmap_regions_per_slice; 2622 size_t off = _bitmap_bytes_per_slice * slice; 2623 size_t len = _bitmap_bytes_per_slice; 2624 char* start = (char*) _bitmap_region.start() + off; 2625 2626 if (!os::commit_memory(start, len, false)) { 2627 return false; 2628 } 2629 2630 if (AlwaysPreTouch) { 2631 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size); 2632 } 2633 2634 return true; 2635 } 2636 2637 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) { 2638 shenandoah_assert_heaplocked(); 2639 2640 // Bitmaps in special regions do not need uncommits 2641 if (_bitmap_region_special) { 2642 return true; 2643 } 2644 2645 if (is_bitmap_slice_committed(r, true)) { 2646 // Some other region from the group is still committed, meaning the bitmap 2647 // slice should stay committed, exit right away. 2648 return true; 2649 } 2650 2651 // Uncommit the bitmap slice: 2652 size_t slice = r->index() / _bitmap_regions_per_slice; 2653 size_t off = _bitmap_bytes_per_slice * slice; 2654 size_t len = _bitmap_bytes_per_slice; 2655 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) { 2656 return false; 2657 } 2658 return true; 2659 } 2660 2661 void ShenandoahHeap::forbid_uncommit() { 2662 if (_uncommit_thread != nullptr) { 2663 _uncommit_thread->forbid_uncommit(); 2664 } 2665 } 2666 2667 void ShenandoahHeap::allow_uncommit() { 2668 if (_uncommit_thread != nullptr) { 2669 _uncommit_thread->allow_uncommit(); 2670 } 2671 } 2672 2673 #ifdef ASSERT 2674 bool ShenandoahHeap::is_uncommit_in_progress() { 2675 if (_uncommit_thread != nullptr) { 2676 return _uncommit_thread->is_uncommit_in_progress(); 2677 } 2678 return false; 2679 } 2680 #endif 2681 2682 void ShenandoahHeap::safepoint_synchronize_begin() { 2683 StackWatermarkSet::safepoint_synchronize_begin(); 2684 SuspendibleThreadSet::synchronize(); 2685 } 2686 2687 void ShenandoahHeap::safepoint_synchronize_end() { 2688 SuspendibleThreadSet::desynchronize(); 2689 } 2690 2691 void ShenandoahHeap::try_inject_alloc_failure() { 2692 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) { 2693 _inject_alloc_failure.set(); 2694 os::naked_short_sleep(1); 2695 if (cancelled_gc()) { 2696 log_info(gc)("Allocation failure was successfully injected"); 2697 } 2698 } 2699 } 2700 2701 bool ShenandoahHeap::should_inject_alloc_failure() { 2702 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset(); 2703 } 2704 2705 void ShenandoahHeap::initialize_serviceability() { 2706 _memory_pool = new ShenandoahMemoryPool(this); 2707 _cycle_memory_manager.add_pool(_memory_pool); 2708 _stw_memory_manager.add_pool(_memory_pool); 2709 } 2710 2711 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() { 2712 GrowableArray<GCMemoryManager*> memory_managers(2); 2713 memory_managers.append(&_cycle_memory_manager); 2714 memory_managers.append(&_stw_memory_manager); 2715 return memory_managers; 2716 } 2717 2718 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() { 2719 GrowableArray<MemoryPool*> memory_pools(1); 2720 memory_pools.append(_memory_pool); 2721 return memory_pools; 2722 } 2723 2724 MemoryUsage ShenandoahHeap::memory_usage() { 2725 return MemoryUsage(_initial_size, used(), committed(), max_capacity()); 2726 } 2727 2728 ShenandoahRegionIterator::ShenandoahRegionIterator() : 2729 _heap(ShenandoahHeap::heap()), 2730 _index(0) {} 2731 2732 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) : 2733 _heap(heap), 2734 _index(0) {} 2735 2736 void ShenandoahRegionIterator::reset() { 2737 _index = 0; 2738 } 2739 2740 bool ShenandoahRegionIterator::has_next() const { 2741 return _index < _heap->num_regions(); 2742 } 2743 2744 char ShenandoahHeap::gc_state() const { 2745 return _gc_state.raw_value(); 2746 } 2747 2748 bool ShenandoahHeap::is_gc_state(GCState state) const { 2749 // If the global gc state has been changed, but hasn't yet been propagated to all threads, then 2750 // the global gc state is the correct value. Once the gc state has been synchronized with all threads, 2751 // _gc_state_changed will be toggled to false and we need to use the thread local state. 2752 return _gc_state_changed ? _gc_state.is_set(state) : ShenandoahThreadLocalData::is_gc_state(state); 2753 } 2754 2755 2756 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) { 2757 #ifdef ASSERT 2758 assert(_liveness_cache != nullptr, "sanity"); 2759 assert(worker_id < _max_workers, "sanity"); 2760 for (uint i = 0; i < num_regions(); i++) { 2761 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty"); 2762 } 2763 #endif 2764 return _liveness_cache[worker_id]; 2765 } 2766 2767 void ShenandoahHeap::flush_liveness_cache(uint worker_id) { 2768 assert(worker_id < _max_workers, "sanity"); 2769 assert(_liveness_cache != nullptr, "sanity"); 2770 ShenandoahLiveData* ld = _liveness_cache[worker_id]; 2771 for (uint i = 0; i < num_regions(); i++) { 2772 ShenandoahLiveData live = ld[i]; 2773 if (live > 0) { 2774 ShenandoahHeapRegion* r = get_region(i); 2775 r->increase_live_data_gc_words(live); 2776 ld[i] = 0; 2777 } 2778 } 2779 } 2780 2781 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const { 2782 if (is_idle()) return false; 2783 2784 // Objects allocated after marking start are implicitly alive, don't need any barriers during 2785 // marking phase. 2786 if (is_concurrent_mark_in_progress() && 2787 !marking_context()->allocated_after_mark_start(obj)) { 2788 return true; 2789 } 2790 2791 // Can not guarantee obj is deeply good. 2792 if (has_forwarded_objects()) { 2793 return true; 2794 } 2795 2796 return false; 2797 } 2798 2799 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) { 2800 #if INCLUDE_CDS_JAVA_HEAP 2801 // CDS wants a continuous memory range to load a bunch of objects. 2802 // This effectively bypasses normal allocation paths, and requires 2803 // a bit of massaging to unbreak GC invariants. 2804 2805 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size); 2806 2807 // Easy case: a single regular region, no further adjustments needed. 2808 if (!ShenandoahHeapRegion::requires_humongous(size)) { 2809 return allocate_memory(req); 2810 } 2811 2812 // Hard case: the requested size would cause a humongous allocation. 2813 // We need to make sure it looks like regular allocation to the rest of GC. 2814 2815 // CDS code would guarantee no objects straddle multiple regions, as long as 2816 // regions are as large as MIN_GC_REGION_ALIGNMENT. It is impractical at this 2817 // point to deal with case when Shenandoah runs with smaller regions. 2818 // TODO: This check can be dropped once MIN_GC_REGION_ALIGNMENT agrees more with Shenandoah. 2819 if (ShenandoahHeapRegion::region_size_bytes() < ArchiveHeapWriter::MIN_GC_REGION_ALIGNMENT) { 2820 return nullptr; 2821 } 2822 2823 HeapWord* mem = allocate_memory(req); 2824 size_t start_idx = heap_region_index_containing(mem); 2825 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize); 2826 2827 // Flip humongous -> regular. 2828 { 2829 ShenandoahHeapLocker locker(lock(), false); 2830 for (size_t c = start_idx; c < start_idx + num_regions; c++) { 2831 get_region(c)->make_regular_bypass(); 2832 } 2833 } 2834 2835 return mem; 2836 #else 2837 assert(false, "Archive heap loader should not be available, should not be here"); 2838 return nullptr; 2839 #endif // INCLUDE_CDS_JAVA_HEAP 2840 } 2841 2842 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) { 2843 // Nothing to do here, except checking that heap looks fine. 2844 #ifdef ASSERT 2845 HeapWord* start = archive_space.start(); 2846 HeapWord* end = archive_space.end(); 2847 2848 // No unclaimed space between the objects. 2849 // Objects are properly allocated in correct regions. 2850 HeapWord* cur = start; 2851 while (cur < end) { 2852 oop oop = cast_to_oop(cur); 2853 shenandoah_assert_in_correct_region(nullptr, oop); 2854 cur += oop->size(); 2855 } 2856 2857 // No unclaimed tail at the end of archive space. 2858 assert(cur == end, 2859 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT, 2860 p2i(cur), p2i(end)); 2861 2862 // Region bounds are good. 2863 ShenandoahHeapRegion* begin_reg = heap_region_containing(start); 2864 ShenandoahHeapRegion* end_reg = heap_region_containing(end); 2865 assert(begin_reg->is_regular(), "Must be"); 2866 assert(end_reg->is_regular(), "Must be"); 2867 assert(begin_reg->bottom() == start, 2868 "Must agree: archive-space-start: " PTR_FORMAT ", begin-region-bottom: " PTR_FORMAT, 2869 p2i(start), p2i(begin_reg->bottom())); 2870 assert(end_reg->top() == end, 2871 "Must agree: archive-space-end: " PTR_FORMAT ", end-region-top: " PTR_FORMAT, 2872 p2i(end), p2i(end_reg->top())); 2873 #endif 2874 } 2875 2876 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const { 2877 if (!mode()->is_generational()) { 2878 return global_generation(); 2879 } else if (affiliation == YOUNG_GENERATION) { 2880 return young_generation(); 2881 } else if (affiliation == OLD_GENERATION) { 2882 return old_generation(); 2883 } 2884 2885 ShouldNotReachHere(); 2886 return nullptr; 2887 } 2888 2889 void ShenandoahHeap::log_heap_status(const char* msg) const { 2890 if (mode()->is_generational()) { 2891 young_generation()->log_status(msg); 2892 old_generation()->log_status(msg); 2893 } else { 2894 global_generation()->log_status(msg); 2895 } 2896 }