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.hpp" 32 #include "gc/shared/gcArguments.hpp" 33 #include "gc/shared/gcTimer.hpp" 34 #include "gc/shared/gcTraceTime.inline.hpp" 35 #include "gc/shared/locationPrinter.inline.hpp" 36 #include "gc/shared/memAllocator.hpp" 37 #include "gc/shared/plab.hpp" 38 #include "gc/shared/tlab_globals.hpp" 39 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp" 40 #include "gc/shenandoah/heuristics/shenandoahYoungHeuristics.hpp" 41 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp" 42 #include "gc/shenandoah/mode/shenandoahPassiveMode.hpp" 43 #include "gc/shenandoah/mode/shenandoahSATBMode.hpp" 44 #include "gc/shenandoah/shenandoahAllocRequest.hpp" 45 #include "gc/shenandoah/shenandoahBarrierSet.hpp" 46 #include "gc/shenandoah/shenandoahClosures.inline.hpp" 47 #include "gc/shenandoah/shenandoahCodeRoots.hpp" 48 #include "gc/shenandoah/shenandoahCollectionSet.hpp" 49 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp" 50 #include "gc/shenandoah/shenandoahConcurrentMark.hpp" 51 #include "gc/shenandoah/shenandoahControlThread.hpp" 52 #include "gc/shenandoah/shenandoahFreeSet.hpp" 53 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp" 54 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp" 55 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp" 56 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 57 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp" 58 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp" 59 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp" 60 #include "gc/shenandoah/shenandoahInitLogger.hpp" 61 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp" 62 #include "gc/shenandoah/shenandoahMemoryPool.hpp" 63 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp" 64 #include "gc/shenandoah/shenandoahOldGeneration.hpp" 65 #include "gc/shenandoah/shenandoahPacer.inline.hpp" 66 #include "gc/shenandoah/shenandoahPadding.hpp" 67 #include "gc/shenandoah/shenandoahParallelCleaning.inline.hpp" 68 #include "gc/shenandoah/shenandoahPhaseTimings.hpp" 69 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp" 70 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp" 71 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp" 72 #include "gc/shenandoah/shenandoahSTWMark.hpp" 73 #include "gc/shenandoah/shenandoahUncommitThread.hpp" 74 #include "gc/shenandoah/shenandoahUtils.hpp" 75 #include "gc/shenandoah/shenandoahVerifier.hpp" 76 #include "gc/shenandoah/shenandoahVMOperations.hpp" 77 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp" 78 #include "gc/shenandoah/shenandoahWorkGroup.hpp" 79 #include "gc/shenandoah/shenandoahYoungGeneration.hpp" 80 #include "memory/allocation.hpp" 81 #include "memory/classLoaderMetaspace.hpp" 82 #include "memory/memoryReserver.hpp" 83 #include "memory/metaspaceUtils.hpp" 84 #include "memory/universe.hpp" 85 #include "nmt/mallocTracker.hpp" 86 #include "nmt/memTracker.hpp" 87 #include "oops/compressedOops.inline.hpp" 88 #include "prims/jvmtiTagMap.hpp" 89 #include "runtime/atomic.hpp" 90 #include "runtime/globals.hpp" 91 #include "runtime/interfaceSupport.inline.hpp" 92 #include "runtime/java.hpp" 93 #include "runtime/orderAccess.hpp" 94 #include "runtime/safepointMechanism.hpp" 95 #include "runtime/stackWatermarkSet.hpp" 96 #include "runtime/threads.hpp" 97 #include "runtime/vmThread.hpp" 98 #include "utilities/events.hpp" 99 #include "utilities/globalDefinitions.hpp" 100 #include "utilities/powerOfTwo.hpp" 101 #if INCLUDE_JFR 102 #include "gc/shenandoah/shenandoahJfrSupport.hpp" 103 #endif 104 105 class ShenandoahPretouchHeapTask : public WorkerTask { 106 private: 107 ShenandoahRegionIterator _regions; 108 const size_t _page_size; 109 public: 110 ShenandoahPretouchHeapTask(size_t page_size) : 111 WorkerTask("Shenandoah Pretouch Heap"), 112 _page_size(page_size) {} 113 114 virtual void work(uint worker_id) { 115 ShenandoahHeapRegion* r = _regions.next(); 116 while (r != nullptr) { 117 if (r->is_committed()) { 118 os::pretouch_memory(r->bottom(), r->end(), _page_size); 119 } 120 r = _regions.next(); 121 } 122 } 123 }; 124 125 class ShenandoahPretouchBitmapTask : public WorkerTask { 126 private: 127 ShenandoahRegionIterator _regions; 128 char* _bitmap_base; 129 const size_t _bitmap_size; 130 const size_t _page_size; 131 public: 132 ShenandoahPretouchBitmapTask(char* bitmap_base, size_t bitmap_size, size_t page_size) : 133 WorkerTask("Shenandoah Pretouch Bitmap"), 134 _bitmap_base(bitmap_base), 135 _bitmap_size(bitmap_size), 136 _page_size(page_size) {} 137 138 virtual void work(uint worker_id) { 139 ShenandoahHeapRegion* r = _regions.next(); 140 while (r != nullptr) { 141 size_t start = r->index() * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor(); 142 size_t end = (r->index() + 1) * ShenandoahHeapRegion::region_size_bytes() / MarkBitMap::heap_map_factor(); 143 assert (end <= _bitmap_size, "end is sane: %zu < %zu", end, _bitmap_size); 144 145 if (r->is_committed()) { 146 os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size); 147 } 148 149 r = _regions.next(); 150 } 151 } 152 }; 153 154 static ReservedSpace reserve(size_t size, size_t preferred_page_size) { 155 // When a page size is given we don't want to mix large 156 // and normal pages. If the size is not a multiple of the 157 // page size it will be aligned up to achieve this. 158 size_t alignment = os::vm_allocation_granularity(); 159 if (preferred_page_size != os::vm_page_size()) { 160 alignment = MAX2(preferred_page_size, alignment); 161 size = align_up(size, alignment); 162 } 163 164 const ReservedSpace reserved = MemoryReserver::reserve(size, alignment, preferred_page_size, mtGC); 165 if (!reserved.is_reserved()) { 166 vm_exit_during_initialization("Could not reserve space"); 167 } 168 return reserved; 169 } 170 171 jint ShenandoahHeap::initialize() { 172 // 173 // Figure out heap sizing 174 // 175 176 size_t init_byte_size = InitialHeapSize; 177 size_t min_byte_size = MinHeapSize; 178 size_t max_byte_size = MaxHeapSize; 179 size_t heap_alignment = HeapAlignment; 180 181 size_t reg_size_bytes = ShenandoahHeapRegion::region_size_bytes(); 182 183 Universe::check_alignment(max_byte_size, reg_size_bytes, "Shenandoah heap"); 184 Universe::check_alignment(init_byte_size, reg_size_bytes, "Shenandoah heap"); 185 186 _num_regions = ShenandoahHeapRegion::region_count(); 187 assert(_num_regions == (max_byte_size / reg_size_bytes), 188 "Regions should cover entire heap exactly: %zu != %zu/%zu", 189 _num_regions, max_byte_size, reg_size_bytes); 190 191 size_t num_committed_regions = init_byte_size / reg_size_bytes; 192 num_committed_regions = MIN2(num_committed_regions, _num_regions); 193 assert(num_committed_regions <= _num_regions, "sanity"); 194 _initial_size = num_committed_regions * reg_size_bytes; 195 196 size_t num_min_regions = min_byte_size / reg_size_bytes; 197 num_min_regions = MIN2(num_min_regions, _num_regions); 198 assert(num_min_regions <= _num_regions, "sanity"); 199 _minimum_size = num_min_regions * reg_size_bytes; 200 201 // Default to max heap size. 202 _soft_max_size = _num_regions * reg_size_bytes; 203 204 _committed = _initial_size; 205 206 size_t heap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 207 size_t bitmap_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 208 size_t region_page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); 209 210 // 211 // Reserve and commit memory for heap 212 // 213 214 ReservedHeapSpace heap_rs = Universe::reserve_heap(max_byte_size, heap_alignment); 215 initialize_reserved_region(heap_rs); 216 _heap_region = MemRegion((HeapWord*)heap_rs.base(), heap_rs.size() / HeapWordSize); 217 _heap_region_special = heap_rs.special(); 218 219 assert((((size_t) base()) & ShenandoahHeapRegion::region_size_bytes_mask()) == 0, 220 "Misaligned heap: " PTR_FORMAT, p2i(base())); 221 os::trace_page_sizes_for_requested_size("Heap", 222 max_byte_size, heap_alignment, 223 heap_rs.base(), 224 heap_rs.size(), heap_rs.page_size()); 225 226 #if SHENANDOAH_OPTIMIZED_MARKTASK 227 // The optimized ShenandoahMarkTask takes some bits away from the full object bits. 228 // Fail if we ever attempt to address more than we can. 229 if ((uintptr_t)heap_rs.end() >= ShenandoahMarkTask::max_addressable()) { 230 FormatBuffer<512> buf("Shenandoah reserved [" PTR_FORMAT ", " PTR_FORMAT") for the heap, \n" 231 "but max object address is " PTR_FORMAT ". Try to reduce heap size, or try other \n" 232 "VM options that allocate heap at lower addresses (HeapBaseMinAddress, AllocateHeapAt, etc).", 233 p2i(heap_rs.base()), p2i(heap_rs.end()), ShenandoahMarkTask::max_addressable()); 234 vm_exit_during_initialization("Fatal Error", buf); 235 } 236 #endif 237 238 ReservedSpace sh_rs = heap_rs.first_part(max_byte_size); 239 if (!_heap_region_special) { 240 os::commit_memory_or_exit(sh_rs.base(), _initial_size, heap_alignment, false, 241 "Cannot commit heap memory"); 242 } 243 244 BarrierSet::set_barrier_set(new ShenandoahBarrierSet(this, _heap_region)); 245 246 // Now we know the number of regions and heap sizes, initialize the heuristics. 247 initialize_heuristics(); 248 249 assert(_heap_region.byte_size() == heap_rs.size(), "Need to know reserved size for card table"); 250 251 // 252 // Worker threads must be initialized after the barrier is configured 253 // 254 _workers = new ShenandoahWorkerThreads("Shenandoah GC Threads", _max_workers); 255 if (_workers == nullptr) { 256 vm_exit_during_initialization("Failed necessary allocation."); 257 } else { 258 _workers->initialize_workers(); 259 } 260 261 if (ParallelGCThreads > 1) { 262 _safepoint_workers = new ShenandoahWorkerThreads("Safepoint Cleanup Thread", ParallelGCThreads); 263 _safepoint_workers->initialize_workers(); 264 } 265 266 // 267 // Reserve and commit memory for bitmap(s) 268 // 269 270 size_t bitmap_size_orig = ShenandoahMarkBitMap::compute_size(heap_rs.size()); 271 _bitmap_size = align_up(bitmap_size_orig, bitmap_page_size); 272 273 size_t bitmap_bytes_per_region = reg_size_bytes / ShenandoahMarkBitMap::heap_map_factor(); 274 275 guarantee(bitmap_bytes_per_region != 0, 276 "Bitmap bytes per region should not be zero"); 277 guarantee(is_power_of_2(bitmap_bytes_per_region), 278 "Bitmap bytes per region should be power of two: %zu", bitmap_bytes_per_region); 279 280 if (bitmap_page_size > bitmap_bytes_per_region) { 281 _bitmap_regions_per_slice = bitmap_page_size / bitmap_bytes_per_region; 282 _bitmap_bytes_per_slice = bitmap_page_size; 283 } else { 284 _bitmap_regions_per_slice = 1; 285 _bitmap_bytes_per_slice = bitmap_bytes_per_region; 286 } 287 288 guarantee(_bitmap_regions_per_slice >= 1, 289 "Should have at least one region per slice: %zu", 290 _bitmap_regions_per_slice); 291 292 guarantee(((_bitmap_bytes_per_slice) % bitmap_page_size) == 0, 293 "Bitmap slices should be page-granular: bps = %zu, page size = %zu", 294 _bitmap_bytes_per_slice, bitmap_page_size); 295 296 ReservedSpace bitmap = reserve(_bitmap_size, bitmap_page_size); 297 os::trace_page_sizes_for_requested_size("Mark Bitmap", 298 bitmap_size_orig, bitmap_page_size, 299 bitmap.base(), 300 bitmap.size(), bitmap.page_size()); 301 MemTracker::record_virtual_memory_tag(bitmap, mtGC); 302 _bitmap_region = MemRegion((HeapWord*) bitmap.base(), bitmap.size() / HeapWordSize); 303 _bitmap_region_special = bitmap.special(); 304 305 size_t bitmap_init_commit = _bitmap_bytes_per_slice * 306 align_up(num_committed_regions, _bitmap_regions_per_slice) / _bitmap_regions_per_slice; 307 bitmap_init_commit = MIN2(_bitmap_size, bitmap_init_commit); 308 if (!_bitmap_region_special) { 309 os::commit_memory_or_exit((char *) _bitmap_region.start(), bitmap_init_commit, bitmap_page_size, false, 310 "Cannot commit bitmap memory"); 311 } 312 313 _marking_context = new ShenandoahMarkingContext(_heap_region, _bitmap_region, _num_regions); 314 315 if (ShenandoahVerify) { 316 ReservedSpace verify_bitmap = reserve(_bitmap_size, bitmap_page_size); 317 os::trace_page_sizes_for_requested_size("Verify Bitmap", 318 bitmap_size_orig, bitmap_page_size, 319 verify_bitmap.base(), 320 verify_bitmap.size(), verify_bitmap.page_size()); 321 if (!verify_bitmap.special()) { 322 os::commit_memory_or_exit(verify_bitmap.base(), verify_bitmap.size(), bitmap_page_size, false, 323 "Cannot commit verification bitmap memory"); 324 } 325 MemTracker::record_virtual_memory_tag(verify_bitmap, mtGC); 326 MemRegion verify_bitmap_region = MemRegion((HeapWord *) verify_bitmap.base(), verify_bitmap.size() / HeapWordSize); 327 _verification_bit_map.initialize(_heap_region, verify_bitmap_region); 328 _verifier = new ShenandoahVerifier(this, &_verification_bit_map); 329 } 330 331 // Reserve aux bitmap for use in object_iterate(). We don't commit it here. 332 size_t aux_bitmap_page_size = bitmap_page_size; 333 334 ReservedSpace aux_bitmap = reserve(_bitmap_size, aux_bitmap_page_size); 335 os::trace_page_sizes_for_requested_size("Aux Bitmap", 336 bitmap_size_orig, aux_bitmap_page_size, 337 aux_bitmap.base(), 338 aux_bitmap.size(), aux_bitmap.page_size()); 339 MemTracker::record_virtual_memory_tag(aux_bitmap, mtGC); 340 _aux_bitmap_region = MemRegion((HeapWord*) aux_bitmap.base(), aux_bitmap.size() / HeapWordSize); 341 _aux_bitmap_region_special = aux_bitmap.special(); 342 _aux_bit_map.initialize(_heap_region, _aux_bitmap_region); 343 344 // 345 // Create regions and region sets 346 // 347 size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE); 348 size_t region_storage_size_orig = region_align * _num_regions; 349 size_t region_storage_size = align_up(region_storage_size_orig, 350 MAX2(region_page_size, os::vm_allocation_granularity())); 351 352 ReservedSpace region_storage = reserve(region_storage_size, region_page_size); 353 os::trace_page_sizes_for_requested_size("Region Storage", 354 region_storage_size_orig, region_page_size, 355 region_storage.base(), 356 region_storage.size(), region_storage.page_size()); 357 MemTracker::record_virtual_memory_tag(region_storage, mtGC); 358 if (!region_storage.special()) { 359 os::commit_memory_or_exit(region_storage.base(), region_storage_size, region_page_size, false, 360 "Cannot commit region memory"); 361 } 362 363 // Try to fit the collection set bitmap at lower addresses. This optimizes code generation for cset checks. 364 // Go up until a sensible limit (subject to encoding constraints) and try to reserve the space there. 365 // If not successful, bite a bullet and allocate at whatever address. 366 { 367 const size_t cset_align = MAX2<size_t>(os::vm_page_size(), os::vm_allocation_granularity()); 368 const size_t cset_size = align_up(((size_t) sh_rs.base() + sh_rs.size()) >> ShenandoahHeapRegion::region_size_bytes_shift(), cset_align); 369 const size_t cset_page_size = os::vm_page_size(); 370 371 uintptr_t min = round_up_power_of_2(cset_align); 372 uintptr_t max = (1u << 30u); 373 ReservedSpace cset_rs; 374 375 for (uintptr_t addr = min; addr <= max; addr <<= 1u) { 376 char* req_addr = (char*)addr; 377 assert(is_aligned(req_addr, cset_align), "Should be aligned"); 378 cset_rs = MemoryReserver::reserve(req_addr, cset_size, cset_align, cset_page_size, mtGC); 379 if (cset_rs.is_reserved()) { 380 assert(cset_rs.base() == req_addr, "Allocated where requested: " PTR_FORMAT ", " PTR_FORMAT, p2i(cset_rs.base()), addr); 381 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base()); 382 break; 383 } 384 } 385 386 if (_collection_set == nullptr) { 387 cset_rs = MemoryReserver::reserve(cset_size, cset_align, os::vm_page_size(), mtGC); 388 if (!cset_rs.is_reserved()) { 389 vm_exit_during_initialization("Cannot reserve memory for collection set"); 390 } 391 392 _collection_set = new ShenandoahCollectionSet(this, cset_rs, sh_rs.base()); 393 } 394 os::trace_page_sizes_for_requested_size("Collection Set", 395 cset_size, cset_page_size, 396 cset_rs.base(), 397 cset_rs.size(), cset_rs.page_size()); 398 } 399 400 _regions = NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, _num_regions, mtGC); 401 _affiliations = NEW_C_HEAP_ARRAY(uint8_t, _num_regions, mtGC); 402 _free_set = new ShenandoahFreeSet(this, _num_regions); 403 404 { 405 ShenandoahHeapLocker locker(lock()); 406 407 for (size_t i = 0; i < _num_regions; i++) { 408 HeapWord* start = (HeapWord*)sh_rs.base() + ShenandoahHeapRegion::region_size_words() * i; 409 bool is_committed = i < num_committed_regions; 410 void* loc = region_storage.base() + i * region_align; 411 412 ShenandoahHeapRegion* r = new (loc) ShenandoahHeapRegion(start, i, is_committed); 413 assert(is_aligned(r, SHENANDOAH_CACHE_LINE_SIZE), "Sanity"); 414 415 _marking_context->initialize_top_at_mark_start(r); 416 _regions[i] = r; 417 assert(!collection_set()->is_in(i), "New region should not be in collection set"); 418 419 _affiliations[i] = ShenandoahAffiliation::FREE; 420 } 421 422 size_t young_cset_regions, old_cset_regions; 423 424 // We are initializing free set. We ignore cset region tallies. 425 size_t first_old, last_old, num_old; 426 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old, last_old, num_old); 427 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, num_old); 428 } 429 430 if (AlwaysPreTouch) { 431 // For NUMA, it is important to pre-touch the storage under bitmaps with worker threads, 432 // before initialize() below zeroes it with initializing thread. For any given region, 433 // we touch the region and the corresponding bitmaps from the same thread. 434 ShenandoahPushWorkerScope scope(workers(), _max_workers, false); 435 436 _pretouch_heap_page_size = heap_page_size; 437 _pretouch_bitmap_page_size = bitmap_page_size; 438 439 // OS memory managers may want to coalesce back-to-back pages. Make their jobs 440 // simpler by pre-touching continuous spaces (heap and bitmap) separately. 441 442 ShenandoahPretouchBitmapTask bcl(bitmap.base(), _bitmap_size, _pretouch_bitmap_page_size); 443 _workers->run_task(&bcl); 444 445 ShenandoahPretouchHeapTask hcl(_pretouch_heap_page_size); 446 _workers->run_task(&hcl); 447 } 448 449 // 450 // Initialize the rest of GC subsystems 451 // 452 453 _liveness_cache = NEW_C_HEAP_ARRAY(ShenandoahLiveData*, _max_workers, mtGC); 454 for (uint worker = 0; worker < _max_workers; worker++) { 455 _liveness_cache[worker] = NEW_C_HEAP_ARRAY(ShenandoahLiveData, _num_regions, mtGC); 456 Copy::fill_to_bytes(_liveness_cache[worker], _num_regions * sizeof(ShenandoahLiveData)); 457 } 458 459 // There should probably be Shenandoah-specific options for these, 460 // just as there are G1-specific options. 461 { 462 ShenandoahSATBMarkQueueSet& satbqs = ShenandoahBarrierSet::satb_mark_queue_set(); 463 satbqs.set_process_completed_buffers_threshold(20); // G1SATBProcessCompletedThreshold 464 satbqs.set_buffer_enqueue_threshold_percentage(60); // G1SATBBufferEnqueueingThresholdPercent 465 } 466 467 _monitoring_support = new ShenandoahMonitoringSupport(this); 468 _phase_timings = new ShenandoahPhaseTimings(max_workers()); 469 ShenandoahCodeRoots::initialize(); 470 471 if (ShenandoahPacing) { 472 _pacer = new ShenandoahPacer(this); 473 _pacer->setup_for_idle(); 474 } 475 476 initialize_controller(); 477 478 if (ShenandoahUncommit) { 479 _uncommit_thread = new ShenandoahUncommitThread(this); 480 } 481 482 print_init_logger(); 483 484 FullGCForwarding::initialize(_heap_region); 485 486 return JNI_OK; 487 } 488 489 void ShenandoahHeap::initialize_controller() { 490 _control_thread = new ShenandoahControlThread(); 491 } 492 493 void ShenandoahHeap::print_init_logger() const { 494 ShenandoahInitLogger::print(); 495 } 496 497 void ShenandoahHeap::initialize_mode() { 498 if (ShenandoahGCMode != nullptr) { 499 if (strcmp(ShenandoahGCMode, "satb") == 0) { 500 _gc_mode = new ShenandoahSATBMode(); 501 } else if (strcmp(ShenandoahGCMode, "passive") == 0) { 502 _gc_mode = new ShenandoahPassiveMode(); 503 } else if (strcmp(ShenandoahGCMode, "generational") == 0) { 504 _gc_mode = new ShenandoahGenerationalMode(); 505 } else { 506 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option"); 507 } 508 } else { 509 vm_exit_during_initialization("Unknown -XX:ShenandoahGCMode option (null)"); 510 } 511 _gc_mode->initialize_flags(); 512 if (_gc_mode->is_diagnostic() && !UnlockDiagnosticVMOptions) { 513 vm_exit_during_initialization( 514 err_msg("GC mode \"%s\" is diagnostic, and must be enabled via -XX:+UnlockDiagnosticVMOptions.", 515 _gc_mode->name())); 516 } 517 if (_gc_mode->is_experimental() && !UnlockExperimentalVMOptions) { 518 vm_exit_during_initialization( 519 err_msg("GC mode \"%s\" is experimental, and must be enabled via -XX:+UnlockExperimentalVMOptions.", 520 _gc_mode->name())); 521 } 522 } 523 524 void ShenandoahHeap::initialize_heuristics() { 525 _global_generation = new ShenandoahGlobalGeneration(mode()->is_generational(), max_workers(), max_capacity(), max_capacity()); 526 _global_generation->initialize_heuristics(mode()); 527 } 528 529 #ifdef _MSC_VER 530 #pragma warning( push ) 531 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 532 #endif 533 534 ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) : 535 CollectedHeap(), 536 _gc_generation(nullptr), 537 _active_generation(nullptr), 538 _initial_size(0), 539 _committed(0), 540 _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)), 541 _workers(nullptr), 542 _safepoint_workers(nullptr), 543 _heap_region_special(false), 544 _num_regions(0), 545 _regions(nullptr), 546 _affiliations(nullptr), 547 _gc_state_changed(false), 548 _gc_no_progress_count(0), 549 _cancel_requested_time(0), 550 _update_refs_iterator(this), 551 _global_generation(nullptr), 552 _control_thread(nullptr), 553 _uncommit_thread(nullptr), 554 _young_generation(nullptr), 555 _old_generation(nullptr), 556 _shenandoah_policy(policy), 557 _gc_mode(nullptr), 558 _free_set(nullptr), 559 _pacer(nullptr), 560 _verifier(nullptr), 561 _phase_timings(nullptr), 562 _monitoring_support(nullptr), 563 _memory_pool(nullptr), 564 _stw_memory_manager("Shenandoah Pauses"), 565 _cycle_memory_manager("Shenandoah Cycles"), 566 _gc_timer(new ConcurrentGCTimer()), 567 _log_min_obj_alignment_in_bytes(LogMinObjAlignmentInBytes), 568 _marking_context(nullptr), 569 _bitmap_size(0), 570 _bitmap_regions_per_slice(0), 571 _bitmap_bytes_per_slice(0), 572 _bitmap_region_special(false), 573 _aux_bitmap_region_special(false), 574 _liveness_cache(nullptr), 575 _collection_set(nullptr) 576 { 577 // Initialize GC mode early, many subsequent initialization procedures depend on it 578 initialize_mode(); 579 _cancelled_gc.set(GCCause::_no_gc); 580 } 581 582 #ifdef _MSC_VER 583 #pragma warning( pop ) 584 #endif 585 586 void ShenandoahHeap::print_heap_on(outputStream* st) const { 587 st->print_cr("Shenandoah Heap"); 588 st->print_cr(" %zu%s max, %zu%s soft max, %zu%s committed, %zu%s used", 589 byte_size_in_proper_unit(max_capacity()), proper_unit_for_byte_size(max_capacity()), 590 byte_size_in_proper_unit(soft_max_capacity()), proper_unit_for_byte_size(soft_max_capacity()), 591 byte_size_in_proper_unit(committed()), proper_unit_for_byte_size(committed()), 592 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used())); 593 st->print_cr(" %zu x %zu %s regions", 594 num_regions(), 595 byte_size_in_proper_unit(ShenandoahHeapRegion::region_size_bytes()), 596 proper_unit_for_byte_size(ShenandoahHeapRegion::region_size_bytes())); 597 598 st->print("Status: "); 599 if (has_forwarded_objects()) st->print("has forwarded objects, "); 600 if (!mode()->is_generational()) { 601 if (is_concurrent_mark_in_progress()) st->print("marking,"); 602 } else { 603 if (is_concurrent_old_mark_in_progress()) st->print("old marking, "); 604 if (is_concurrent_young_mark_in_progress()) st->print("young marking, "); 605 } 606 if (is_evacuation_in_progress()) st->print("evacuating, "); 607 if (is_update_refs_in_progress()) st->print("updating refs, "); 608 if (is_degenerated_gc_in_progress()) st->print("degenerated gc, "); 609 if (is_full_gc_in_progress()) st->print("full gc, "); 610 if (is_full_gc_move_in_progress()) st->print("full gc move, "); 611 if (is_concurrent_weak_root_in_progress()) st->print("concurrent weak roots, "); 612 if (is_concurrent_strong_root_in_progress() && 613 !is_concurrent_weak_root_in_progress()) st->print("concurrent strong roots, "); 614 615 if (cancelled_gc()) { 616 st->print("cancelled"); 617 } else { 618 st->print("not cancelled"); 619 } 620 st->cr(); 621 622 st->print_cr("Reserved region:"); 623 st->print_cr(" - [" PTR_FORMAT ", " PTR_FORMAT ") ", 624 p2i(reserved_region().start()), 625 p2i(reserved_region().end())); 626 627 ShenandoahCollectionSet* cset = collection_set(); 628 st->print_cr("Collection set:"); 629 if (cset != nullptr) { 630 st->print_cr(" - map (vanilla): " PTR_FORMAT, p2i(cset->map_address())); 631 st->print_cr(" - map (biased): " PTR_FORMAT, p2i(cset->biased_map_address())); 632 } else { 633 st->print_cr(" (null)"); 634 } 635 636 st->cr(); 637 638 if (Verbose) { 639 st->cr(); 640 print_heap_regions_on(st); 641 } 642 } 643 644 void ShenandoahHeap::print_gc_on(outputStream* st) const { 645 print_heap_regions_on(st); 646 } 647 648 class ShenandoahInitWorkerGCLABClosure : public ThreadClosure { 649 public: 650 void do_thread(Thread* thread) { 651 assert(thread != nullptr, "Sanity"); 652 ShenandoahThreadLocalData::initialize_gclab(thread); 653 } 654 }; 655 656 void ShenandoahHeap::post_initialize() { 657 CollectedHeap::post_initialize(); 658 659 // Schedule periodic task to report on gc thread CPU utilization 660 _mmu_tracker.initialize(); 661 662 MutexLocker ml(Threads_lock); 663 664 ShenandoahInitWorkerGCLABClosure init_gclabs; 665 _workers->threads_do(&init_gclabs); 666 667 // gclab can not be initialized early during VM startup, as it can not determinate its max_size. 668 // Now, we will let WorkerThreads to initialize gclab when new worker is created. 669 _workers->set_initialize_gclab(); 670 671 // Note that the safepoint workers may require gclabs if the threads are used to create a heap dump 672 // during a concurrent evacuation phase. 673 if (_safepoint_workers != nullptr) { 674 _safepoint_workers->threads_do(&init_gclabs); 675 _safepoint_workers->set_initialize_gclab(); 676 } 677 678 JFR_ONLY(ShenandoahJFRSupport::register_jfr_type_serializers();) 679 } 680 681 ShenandoahHeuristics* ShenandoahHeap::heuristics() { 682 return _global_generation->heuristics(); 683 } 684 685 size_t ShenandoahHeap::used() const { 686 return global_generation()->used(); 687 } 688 689 size_t ShenandoahHeap::committed() const { 690 return Atomic::load(&_committed); 691 } 692 693 void ShenandoahHeap::increase_committed(size_t bytes) { 694 shenandoah_assert_heaplocked_or_safepoint(); 695 _committed += bytes; 696 } 697 698 void ShenandoahHeap::decrease_committed(size_t bytes) { 699 shenandoah_assert_heaplocked_or_safepoint(); 700 _committed -= bytes; 701 } 702 703 // For tracking usage based on allocations, it should be the case that: 704 // * The sum of regions::used == heap::used 705 // * The sum of a generation's regions::used == generation::used 706 // * The sum of a generation's humongous regions::free == generation::humongous_waste 707 // These invariants are checked by the verifier on GC safepoints. 708 // 709 // Additional notes: 710 // * When a mutator's allocation request causes a region to be retired, the 711 // free memory left in that region is considered waste. It does not contribute 712 // to the usage, but it _does_ contribute to allocation rate. 713 // * The bottom of a PLAB must be aligned on card size. In some cases this will 714 // require padding in front of the PLAB (a filler object). Because this padding 715 // is included in the region's used memory we include the padding in the usage 716 // accounting as waste. 717 // * Mutator allocations are used to compute an allocation rate. They are also 718 // sent to the Pacer for those purposes. 719 // * There are three sources of waste: 720 // 1. The padding used to align a PLAB on card size 721 // 2. Region's free is less than minimum TLAB size and is retired 722 // 3. The unused portion of memory in the last region of a humongous object 723 void ShenandoahHeap::increase_used(const ShenandoahAllocRequest& req) { 724 size_t actual_bytes = req.actual_size() * HeapWordSize; 725 size_t wasted_bytes = req.waste() * HeapWordSize; 726 ShenandoahGeneration* generation = generation_for(req.affiliation()); 727 728 if (req.is_gc_alloc()) { 729 assert(wasted_bytes == 0 || req.type() == ShenandoahAllocRequest::_alloc_plab, "Only PLABs have waste"); 730 increase_used(generation, actual_bytes + wasted_bytes); 731 } else { 732 assert(req.is_mutator_alloc(), "Expected mutator alloc here"); 733 // padding and actual size both count towards allocation counter 734 generation->increase_allocated(actual_bytes + wasted_bytes); 735 736 // only actual size counts toward usage for mutator allocations 737 increase_used(generation, actual_bytes); 738 739 // notify pacer of both actual size and waste 740 notify_mutator_alloc_words(req.actual_size(), req.waste()); 741 742 if (wasted_bytes > 0 && ShenandoahHeapRegion::requires_humongous(req.actual_size())) { 743 increase_humongous_waste(generation,wasted_bytes); 744 } 745 } 746 } 747 748 void ShenandoahHeap::increase_humongous_waste(ShenandoahGeneration* generation, size_t bytes) { 749 generation->increase_humongous_waste(bytes); 750 if (!generation->is_global()) { 751 global_generation()->increase_humongous_waste(bytes); 752 } 753 } 754 755 void ShenandoahHeap::decrease_humongous_waste(ShenandoahGeneration* generation, size_t bytes) { 756 generation->decrease_humongous_waste(bytes); 757 if (!generation->is_global()) { 758 global_generation()->decrease_humongous_waste(bytes); 759 } 760 } 761 762 void ShenandoahHeap::increase_used(ShenandoahGeneration* generation, size_t bytes) { 763 generation->increase_used(bytes); 764 if (!generation->is_global()) { 765 global_generation()->increase_used(bytes); 766 } 767 } 768 769 void ShenandoahHeap::decrease_used(ShenandoahGeneration* generation, size_t bytes) { 770 generation->decrease_used(bytes); 771 if (!generation->is_global()) { 772 global_generation()->decrease_used(bytes); 773 } 774 } 775 776 void ShenandoahHeap::notify_mutator_alloc_words(size_t words, size_t waste) { 777 if (ShenandoahPacing) { 778 control_thread()->pacing_notify_alloc(words); 779 if (waste > 0) { 780 pacer()->claim_for_alloc<true>(waste); 781 } 782 } 783 } 784 785 size_t ShenandoahHeap::capacity() const { 786 return committed(); 787 } 788 789 size_t ShenandoahHeap::max_capacity() const { 790 return _num_regions * ShenandoahHeapRegion::region_size_bytes(); 791 } 792 793 size_t ShenandoahHeap::soft_max_capacity() const { 794 size_t v = Atomic::load(&_soft_max_size); 795 assert(min_capacity() <= v && v <= max_capacity(), 796 "Should be in bounds: %zu <= %zu <= %zu", 797 min_capacity(), v, max_capacity()); 798 return v; 799 } 800 801 void ShenandoahHeap::set_soft_max_capacity(size_t v) { 802 assert(min_capacity() <= v && v <= max_capacity(), 803 "Should be in bounds: %zu <= %zu <= %zu", 804 min_capacity(), v, max_capacity()); 805 Atomic::store(&_soft_max_size, v); 806 } 807 808 size_t ShenandoahHeap::min_capacity() const { 809 return _minimum_size; 810 } 811 812 size_t ShenandoahHeap::initial_capacity() const { 813 return _initial_size; 814 } 815 816 bool ShenandoahHeap::is_in(const void* p) const { 817 if (!is_in_reserved(p)) { 818 return false; 819 } 820 821 if (is_full_gc_move_in_progress()) { 822 // Full GC move is running, we do not have a consistent region 823 // information yet. But we know the pointer is in heap. 824 return true; 825 } 826 827 // Now check if we point to a live section in active region. 828 const ShenandoahHeapRegion* r = heap_region_containing(p); 829 if (p >= r->top()) { 830 return false; 831 } 832 833 if (r->is_active()) { 834 return true; 835 } 836 837 // The region is trash, but won't be recycled until after concurrent weak 838 // roots. We also don't allow mutators to allocate from trash regions 839 // during weak roots. Concurrent class unloading may access unmarked oops 840 // in trash regions. 841 return r->is_trash() && is_concurrent_weak_root_in_progress(); 842 } 843 844 void ShenandoahHeap::notify_soft_max_changed() { 845 if (_uncommit_thread != nullptr) { 846 _uncommit_thread->notify_soft_max_changed(); 847 } 848 } 849 850 void ShenandoahHeap::notify_explicit_gc_requested() { 851 if (_uncommit_thread != nullptr) { 852 _uncommit_thread->notify_explicit_gc_requested(); 853 } 854 } 855 856 bool ShenandoahHeap::check_soft_max_changed() { 857 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize); 858 size_t old_soft_max = soft_max_capacity(); 859 if (new_soft_max != old_soft_max) { 860 new_soft_max = MAX2(min_capacity(), new_soft_max); 861 new_soft_max = MIN2(max_capacity(), new_soft_max); 862 if (new_soft_max != old_soft_max) { 863 log_info(gc)("Soft Max Heap Size: %zu%s -> %zu%s", 864 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max), 865 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max) 866 ); 867 set_soft_max_capacity(new_soft_max); 868 return true; 869 } 870 } 871 return false; 872 } 873 874 void ShenandoahHeap::notify_heap_changed() { 875 // Update monitoring counters when we took a new region. This amortizes the 876 // update costs on slow path. 877 monitoring_support()->notify_heap_changed(); 878 _heap_changed.try_set(); 879 } 880 881 void ShenandoahHeap::set_forced_counters_update(bool value) { 882 monitoring_support()->set_forced_counters_update(value); 883 } 884 885 void ShenandoahHeap::handle_force_counters_update() { 886 monitoring_support()->handle_force_counters_update(); 887 } 888 889 HeapWord* ShenandoahHeap::allocate_from_gclab_slow(Thread* thread, size_t size) { 890 // New object should fit the GCLAB size 891 size_t min_size = MAX2(size, PLAB::min_size()); 892 893 // Figure out size of new GCLAB, looking back at heuristics. Expand aggressively. 894 size_t new_size = ShenandoahThreadLocalData::gclab_size(thread) * 2; 895 896 new_size = MIN2(new_size, PLAB::max_size()); 897 new_size = MAX2(new_size, PLAB::min_size()); 898 899 // Record new heuristic value even if we take any shortcut. This captures 900 // the case when moderately-sized objects always take a shortcut. At some point, 901 // heuristics should catch up with them. 902 log_debug(gc, free)("Set new GCLAB size: %zu", new_size); 903 ShenandoahThreadLocalData::set_gclab_size(thread, new_size); 904 905 if (new_size < size) { 906 // New size still does not fit the object. Fall back to shared allocation. 907 // This avoids retiring perfectly good GCLABs, when we encounter a large object. 908 log_debug(gc, free)("New gclab size (%zu) is too small for %zu", new_size, size); 909 return nullptr; 910 } 911 912 // Retire current GCLAB, and allocate a new one. 913 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread); 914 gclab->retire(); 915 916 size_t actual_size = 0; 917 HeapWord* gclab_buf = allocate_new_gclab(min_size, new_size, &actual_size); 918 if (gclab_buf == nullptr) { 919 return nullptr; 920 } 921 922 assert (size <= actual_size, "allocation should fit"); 923 924 // ...and clear or zap just allocated TLAB, if needed. 925 if (ZeroTLAB) { 926 Copy::zero_to_words(gclab_buf, actual_size); 927 } else if (ZapTLAB) { 928 // Skip mangling the space corresponding to the object header to 929 // ensure that the returned space is not considered parsable by 930 // any concurrent GC thread. 931 size_t hdr_size = oopDesc::header_size(); 932 Copy::fill_to_words(gclab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal); 933 } 934 gclab->set_buf(gclab_buf, actual_size); 935 return gclab->allocate(size); 936 } 937 938 // Called from stubs in JIT code or interpreter 939 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size, 940 size_t requested_size, 941 size_t* actual_size) { 942 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_tlab(min_size, requested_size); 943 HeapWord* res = allocate_memory(req); 944 if (res != nullptr) { 945 *actual_size = req.actual_size(); 946 } else { 947 *actual_size = 0; 948 } 949 return res; 950 } 951 952 HeapWord* ShenandoahHeap::allocate_new_gclab(size_t min_size, 953 size_t word_size, 954 size_t* actual_size) { 955 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_gclab(min_size, word_size); 956 HeapWord* res = allocate_memory(req); 957 if (res != nullptr) { 958 *actual_size = req.actual_size(); 959 } else { 960 *actual_size = 0; 961 } 962 return res; 963 } 964 965 HeapWord* ShenandoahHeap::allocate_memory(ShenandoahAllocRequest& req) { 966 intptr_t pacer_epoch = 0; 967 bool in_new_region = false; 968 HeapWord* result = nullptr; 969 970 if (req.is_mutator_alloc()) { 971 if (ShenandoahPacing) { 972 pacer()->pace_for_alloc(req.size()); 973 pacer_epoch = pacer()->epoch(); 974 } 975 976 if (!ShenandoahAllocFailureALot || !should_inject_alloc_failure()) { 977 result = allocate_memory_under_lock(req, in_new_region); 978 } 979 980 // Check that gc overhead is not exceeded. 981 // 982 // Shenandoah will grind along for quite a while allocating one 983 // object at a time using shared (non-tlab) allocations. This check 984 // is testing that the GC overhead limit has not been exceeded. 985 // This will notify the collector to start a cycle, but will raise 986 // an OOME to the mutator if the last Full GCs have not made progress. 987 // gc_no_progress_count is incremented following each degen or full GC that fails to achieve is_good_progress(). 988 if (result == nullptr && !req.is_lab_alloc() && get_gc_no_progress_count() > ShenandoahNoProgressThreshold) { 989 control_thread()->handle_alloc_failure(req, false); 990 req.set_actual_size(0); 991 return nullptr; 992 } 993 994 if (result == nullptr) { 995 // Block until control thread reacted, then retry allocation. 996 // 997 // It might happen that one of the threads requesting allocation would unblock 998 // way later after GC happened, only to fail the second allocation, because 999 // other threads have already depleted the free storage. In this case, a better 1000 // strategy is to try again, until at least one full GC has completed. 1001 // 1002 // Stop retrying and return nullptr to cause OOMError exception if our allocation failed even after: 1003 // a) We experienced a GC that had good progress, or 1004 // b) We experienced at least one Full GC (whether or not it had good progress) 1005 1006 const size_t original_count = shenandoah_policy()->full_gc_count(); 1007 while (result == nullptr && should_retry_allocation(original_count)) { 1008 control_thread()->handle_alloc_failure(req, true); 1009 result = allocate_memory_under_lock(req, in_new_region); 1010 } 1011 if (result != nullptr) { 1012 // If our allocation request has been satisfied after it initially failed, we count this as good gc progress 1013 notify_gc_progress(); 1014 } 1015 if (log_develop_is_enabled(Debug, gc, alloc)) { 1016 ResourceMark rm; 1017 log_debug(gc, alloc)("Thread: %s, Result: " PTR_FORMAT ", Request: %s, Size: %zu" 1018 ", Original: %zu, Latest: %zu", 1019 Thread::current()->name(), p2i(result), req.type_string(), req.size(), 1020 original_count, get_gc_no_progress_count()); 1021 } 1022 } 1023 } else { 1024 assert(req.is_gc_alloc(), "Can only accept GC allocs here"); 1025 result = allocate_memory_under_lock(req, in_new_region); 1026 // Do not call handle_alloc_failure() here, because we cannot block. 1027 // The allocation failure would be handled by the LRB slowpath with handle_alloc_failure_evac(). 1028 } 1029 1030 if (in_new_region) { 1031 notify_heap_changed(); 1032 } 1033 1034 if (result == nullptr) { 1035 req.set_actual_size(0); 1036 } 1037 1038 // This is called regardless of the outcome of the allocation to account 1039 // for any waste created by retiring regions with this request. 1040 increase_used(req); 1041 1042 if (result != nullptr) { 1043 size_t requested = req.size(); 1044 size_t actual = req.actual_size(); 1045 1046 assert (req.is_lab_alloc() || (requested == actual), 1047 "Only LAB allocations are elastic: %s, requested = %zu, actual = %zu", 1048 ShenandoahAllocRequest::alloc_type_to_string(req.type()), requested, actual); 1049 1050 if (req.is_mutator_alloc()) { 1051 // If we requested more than we were granted, give the rest back to pacer. 1052 // This only matters if we are in the same pacing epoch: do not try to unpace 1053 // over the budget for the other phase. 1054 if (ShenandoahPacing && (pacer_epoch > 0) && (requested > actual)) { 1055 pacer()->unpace_for_alloc(pacer_epoch, requested - actual); 1056 } 1057 } 1058 } 1059 1060 return result; 1061 } 1062 1063 inline bool ShenandoahHeap::should_retry_allocation(size_t original_full_gc_count) const { 1064 return shenandoah_policy()->full_gc_count() == original_full_gc_count 1065 && !shenandoah_policy()->is_at_shutdown(); 1066 } 1067 1068 HeapWord* ShenandoahHeap::allocate_memory_under_lock(ShenandoahAllocRequest& req, bool& in_new_region) { 1069 // If we are dealing with mutator allocation, then we may need to block for safepoint. 1070 // We cannot block for safepoint for GC allocations, because there is a high chance 1071 // we are already running at safepoint or from stack watermark machinery, and we cannot 1072 // block again. 1073 ShenandoahHeapLocker locker(lock(), req.is_mutator_alloc()); 1074 1075 // Make sure the old generation has room for either evacuations or promotions before trying to allocate. 1076 if (req.is_old() && !old_generation()->can_allocate(req)) { 1077 return nullptr; 1078 } 1079 1080 // If TLAB request size is greater than available, allocate() will attempt to downsize request to fit within available 1081 // memory. 1082 HeapWord* result = _free_set->allocate(req, in_new_region); 1083 1084 // Record the plab configuration for this result and register the object. 1085 if (result != nullptr && req.is_old()) { 1086 old_generation()->configure_plab_for_current_thread(req); 1087 if (req.type() == ShenandoahAllocRequest::_alloc_shared_gc) { 1088 // Register the newly allocated object while we're holding the global lock since there's no synchronization 1089 // built in to the implementation of register_object(). There are potential races when multiple independent 1090 // threads are allocating objects, some of which might span the same card region. For example, consider 1091 // a card table's memory region within which three objects are being allocated by three different threads: 1092 // 1093 // objects being "concurrently" allocated: 1094 // [-----a------][-----b-----][--------------c------------------] 1095 // [---- card table memory range --------------] 1096 // 1097 // Before any objects are allocated, this card's memory range holds no objects. Note that allocation of object a 1098 // wants to set the starts-object, first-start, and last-start attributes of the preceding card region. 1099 // Allocation of object b wants to set the starts-object, first-start, and last-start attributes of this card region. 1100 // Allocation of object c also wants to set the starts-object, first-start, and last-start attributes of this 1101 // card region. 1102 // 1103 // The thread allocating b and the thread allocating c can "race" in various ways, resulting in confusion, such as 1104 // last-start representing object b while first-start represents object c. This is why we need to require all 1105 // register_object() invocations to be "mutually exclusive" with respect to each card's memory range. 1106 old_generation()->card_scan()->register_object(result); 1107 } 1108 } 1109 1110 return result; 1111 } 1112 1113 HeapWord* ShenandoahHeap::mem_allocate(size_t size, 1114 bool* gc_overhead_limit_was_exceeded) { 1115 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size); 1116 return allocate_memory(req); 1117 } 1118 1119 MetaWord* ShenandoahHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data, 1120 size_t size, 1121 Metaspace::MetadataType mdtype) { 1122 MetaWord* result; 1123 1124 // Inform metaspace OOM to GC heuristics if class unloading is possible. 1125 ShenandoahHeuristics* h = global_generation()->heuristics(); 1126 if (h->can_unload_classes()) { 1127 h->record_metaspace_oom(); 1128 } 1129 1130 // Expand and retry allocation 1131 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype); 1132 if (result != nullptr) { 1133 return result; 1134 } 1135 1136 // Start full GC 1137 collect(GCCause::_metadata_GC_clear_soft_refs); 1138 1139 // Retry allocation 1140 result = loader_data->metaspace_non_null()->allocate(size, mdtype); 1141 if (result != nullptr) { 1142 return result; 1143 } 1144 1145 // Expand and retry allocation 1146 result = loader_data->metaspace_non_null()->expand_and_allocate(size, mdtype); 1147 if (result != nullptr) { 1148 return result; 1149 } 1150 1151 // Out of memory 1152 return nullptr; 1153 } 1154 1155 class ShenandoahConcurrentEvacuateRegionObjectClosure : public ObjectClosure { 1156 private: 1157 ShenandoahHeap* const _heap; 1158 Thread* const _thread; 1159 public: 1160 ShenandoahConcurrentEvacuateRegionObjectClosure(ShenandoahHeap* heap) : 1161 _heap(heap), _thread(Thread::current()) {} 1162 1163 void do_object(oop p) { 1164 shenandoah_assert_marked(nullptr, p); 1165 if (!p->is_forwarded()) { 1166 _heap->evacuate_object(p, _thread); 1167 } 1168 } 1169 }; 1170 1171 class ShenandoahEvacuationTask : public WorkerTask { 1172 private: 1173 ShenandoahHeap* const _sh; 1174 ShenandoahCollectionSet* const _cs; 1175 bool _concurrent; 1176 public: 1177 ShenandoahEvacuationTask(ShenandoahHeap* sh, 1178 ShenandoahCollectionSet* cs, 1179 bool concurrent) : 1180 WorkerTask("Shenandoah Evacuation"), 1181 _sh(sh), 1182 _cs(cs), 1183 _concurrent(concurrent) 1184 {} 1185 1186 void work(uint worker_id) { 1187 if (_concurrent) { 1188 ShenandoahConcurrentWorkerSession worker_session(worker_id); 1189 ShenandoahSuspendibleThreadSetJoiner stsj; 1190 ShenandoahEvacOOMScope oom_evac_scope; 1191 do_work(); 1192 } else { 1193 ShenandoahParallelWorkerSession worker_session(worker_id); 1194 ShenandoahEvacOOMScope oom_evac_scope; 1195 do_work(); 1196 } 1197 } 1198 1199 private: 1200 void do_work() { 1201 ShenandoahConcurrentEvacuateRegionObjectClosure cl(_sh); 1202 ShenandoahHeapRegion* r; 1203 while ((r =_cs->claim_next()) != nullptr) { 1204 assert(r->has_live(), "Region %zu should have been reclaimed early", r->index()); 1205 _sh->marked_object_iterate(r, &cl); 1206 1207 if (ShenandoahPacing) { 1208 _sh->pacer()->report_evac(r->used() >> LogHeapWordSize); 1209 } 1210 1211 if (_sh->check_cancelled_gc_and_yield(_concurrent)) { 1212 break; 1213 } 1214 } 1215 } 1216 }; 1217 1218 class ShenandoahRetireGCLABClosure : public ThreadClosure { 1219 private: 1220 bool const _resize; 1221 public: 1222 explicit ShenandoahRetireGCLABClosure(bool resize) : _resize(resize) {} 1223 void do_thread(Thread* thread) override { 1224 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread); 1225 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name()); 1226 gclab->retire(); 1227 if (_resize && ShenandoahThreadLocalData::gclab_size(thread) > 0) { 1228 ShenandoahThreadLocalData::set_gclab_size(thread, 0); 1229 } 1230 1231 if (ShenandoahHeap::heap()->mode()->is_generational()) { 1232 PLAB* plab = ShenandoahThreadLocalData::plab(thread); 1233 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name()); 1234 1235 // There are two reasons to retire all plabs between old-gen evacuation passes. 1236 // 1. We need to make the plab memory parsable by remembered-set scanning. 1237 // 2. We need to establish a trustworthy UpdateWaterMark value within each old-gen heap region 1238 ShenandoahGenerationalHeap::heap()->retire_plab(plab, thread); 1239 if (_resize && ShenandoahThreadLocalData::plab_size(thread) > 0) { 1240 ShenandoahThreadLocalData::set_plab_size(thread, 0); 1241 } 1242 } 1243 } 1244 }; 1245 1246 class ShenandoahGCStatePropagator : public HandshakeClosure { 1247 public: 1248 explicit ShenandoahGCStatePropagator(char gc_state) : 1249 HandshakeClosure("Shenandoah GC State Change"), 1250 _gc_state(gc_state) {} 1251 1252 void do_thread(Thread* thread) override { 1253 ShenandoahThreadLocalData::set_gc_state(thread, _gc_state); 1254 } 1255 private: 1256 char _gc_state; 1257 }; 1258 1259 class ShenandoahPrepareForUpdateRefs : public HandshakeClosure { 1260 public: 1261 explicit ShenandoahPrepareForUpdateRefs(char gc_state) : 1262 HandshakeClosure("Shenandoah Prepare for Update Refs"), 1263 _retire(ResizeTLAB), _propagator(gc_state) {} 1264 1265 void do_thread(Thread* thread) override { 1266 _propagator.do_thread(thread); 1267 if (ShenandoahThreadLocalData::gclab(thread) != nullptr) { 1268 _retire.do_thread(thread); 1269 } 1270 } 1271 private: 1272 ShenandoahRetireGCLABClosure _retire; 1273 ShenandoahGCStatePropagator _propagator; 1274 }; 1275 1276 void ShenandoahHeap::evacuate_collection_set(bool concurrent) { 1277 ShenandoahEvacuationTask task(this, _collection_set, concurrent); 1278 workers()->run_task(&task); 1279 } 1280 1281 void ShenandoahHeap::concurrent_prepare_for_update_refs() { 1282 { 1283 // Java threads take this lock while they are being attached and added to the list of thread. 1284 // If another thread holds this lock before we update the gc state, it will receive a stale 1285 // gc state, but they will have been added to the list of java threads and so will be corrected 1286 // by the following handshake. 1287 MutexLocker lock(Threads_lock); 1288 1289 // A cancellation at this point means the degenerated cycle must resume from update-refs. 1290 set_gc_state_concurrent(EVACUATION, false); 1291 set_gc_state_concurrent(WEAK_ROOTS, false); 1292 set_gc_state_concurrent(UPDATE_REFS, true); 1293 } 1294 1295 // This will propagate the gc state and retire gclabs and plabs for threads that require it. 1296 ShenandoahPrepareForUpdateRefs prepare_for_update_refs(_gc_state.raw_value()); 1297 1298 // The handshake won't touch worker threads (or control thread, or VM thread), so do those separately. 1299 Threads::non_java_threads_do(&prepare_for_update_refs); 1300 1301 // Now retire gclabs and plabs and propagate gc_state for mutator threads 1302 Handshake::execute(&prepare_for_update_refs); 1303 1304 _update_refs_iterator.reset(); 1305 } 1306 1307 class ShenandoahCompositeHandshakeClosure : public HandshakeClosure { 1308 HandshakeClosure* _handshake_1; 1309 HandshakeClosure* _handshake_2; 1310 public: 1311 ShenandoahCompositeHandshakeClosure(HandshakeClosure* handshake_1, HandshakeClosure* handshake_2) : 1312 HandshakeClosure(handshake_2->name()), 1313 _handshake_1(handshake_1), _handshake_2(handshake_2) {} 1314 1315 void do_thread(Thread* thread) override { 1316 _handshake_1->do_thread(thread); 1317 _handshake_2->do_thread(thread); 1318 } 1319 }; 1320 1321 void ShenandoahHeap::concurrent_final_roots(HandshakeClosure* handshake_closure) { 1322 { 1323 assert(!is_evacuation_in_progress(), "Should not evacuate for abbreviated or old cycles"); 1324 MutexLocker lock(Threads_lock); 1325 set_gc_state_concurrent(WEAK_ROOTS, false); 1326 } 1327 1328 ShenandoahGCStatePropagator propagator(_gc_state.raw_value()); 1329 Threads::non_java_threads_do(&propagator); 1330 if (handshake_closure == nullptr) { 1331 Handshake::execute(&propagator); 1332 } else { 1333 ShenandoahCompositeHandshakeClosure composite(&propagator, handshake_closure); 1334 Handshake::execute(&composite); 1335 } 1336 } 1337 1338 oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) { 1339 assert(thread == Thread::current(), "Expected thread parameter to be current thread."); 1340 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) { 1341 // This thread went through the OOM during evac protocol. It is safe to return 1342 // the forward pointer. It must not attempt to evacuate any other objects. 1343 return ShenandoahBarrierSet::resolve_forwarded(p); 1344 } 1345 1346 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope"); 1347 1348 ShenandoahHeapRegion* r = heap_region_containing(p); 1349 assert(!r->is_humongous(), "never evacuate humongous objects"); 1350 1351 ShenandoahAffiliation target_gen = r->affiliation(); 1352 return try_evacuate_object(p, thread, r, target_gen); 1353 } 1354 1355 oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region, 1356 ShenandoahAffiliation target_gen) { 1357 assert(target_gen == YOUNG_GENERATION, "Only expect evacuations to young in this mode"); 1358 assert(from_region->is_young(), "Only expect evacuations from young in this mode"); 1359 bool alloc_from_lab = true; 1360 HeapWord* copy = nullptr; 1361 1362 markWord mark = p->mark(); 1363 if (ShenandoahForwarding::is_forwarded(mark)) { 1364 return ShenandoahForwarding::get_forwardee(p); 1365 } 1366 size_t old_size = ShenandoahForwarding::size(p); 1367 size_t size = p->copy_size(old_size, mark); 1368 1369 #ifdef ASSERT 1370 if (ShenandoahOOMDuringEvacALot && 1371 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call 1372 copy = nullptr; 1373 } else { 1374 #endif 1375 if (UseTLAB) { 1376 copy = allocate_from_gclab(thread, size); 1377 } 1378 if (copy == nullptr) { 1379 // If we failed to allocate in LAB, we'll try a shared allocation. 1380 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen); 1381 copy = allocate_memory(req); 1382 alloc_from_lab = false; 1383 } 1384 #ifdef ASSERT 1385 } 1386 #endif 1387 1388 if (copy == nullptr) { 1389 control_thread()->handle_alloc_failure_evac(size); 1390 1391 _oom_evac_handler.handle_out_of_memory_during_evacuation(); 1392 1393 return ShenandoahBarrierSet::resolve_forwarded(p); 1394 } 1395 1396 // Copy the object: 1397 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, old_size); 1398 1399 // Try to install the new forwarding pointer. 1400 oop copy_val = cast_to_oop(copy); 1401 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val); 1402 if (result == copy_val) { 1403 // Successfully evacuated. Our copy is now the public one! 1404 copy_val->initialize_hash_if_necessary(p); 1405 ContinuationGCSupport::relativize_stack_chunk(copy_val); 1406 shenandoah_assert_correct(nullptr, copy_val); 1407 return copy_val; 1408 } else { 1409 // Failed to evacuate. We need to deal with the object that is left behind. Since this 1410 // new allocation is certainly after TAMS, it will be considered live in the next cycle. 1411 // But if it happens to contain references to evacuated regions, those references would 1412 // not get updated for this stale copy during this cycle, and we will crash while scanning 1413 // it the next cycle. 1414 if (alloc_from_lab) { 1415 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next 1416 // object will overwrite this stale copy, or the filler object on LAB retirement will 1417 // do this. 1418 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size); 1419 } else { 1420 // For non-LAB allocations, we have no way to retract the allocation, and 1421 // have to explicitly overwrite the copy with the filler object. With that overwrite, 1422 // we have to keep the fwdptr initialized and pointing to our (stale) copy. 1423 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size"); 1424 fill_with_object(copy, size); 1425 shenandoah_assert_correct(nullptr, copy_val); 1426 // For non-LAB allocations, the object has already been registered 1427 } 1428 shenandoah_assert_correct(nullptr, result); 1429 return result; 1430 } 1431 } 1432 1433 void ShenandoahHeap::trash_cset_regions() { 1434 ShenandoahHeapLocker locker(lock()); 1435 1436 ShenandoahCollectionSet* set = collection_set(); 1437 ShenandoahHeapRegion* r; 1438 set->clear_current_index(); 1439 while ((r = set->next()) != nullptr) { 1440 r->make_trash(); 1441 } 1442 collection_set()->clear(); 1443 } 1444 1445 void ShenandoahHeap::print_heap_regions_on(outputStream* st) const { 1446 st->print_cr("Heap Regions:"); 1447 st->print_cr("Region state: EU=empty-uncommitted, EC=empty-committed, R=regular, H=humongous start, HP=pinned humongous start"); 1448 st->print_cr(" HC=humongous continuation, CS=collection set, TR=trash, P=pinned, CSP=pinned collection set"); 1449 st->print_cr("BTE=bottom/top/end, TAMS=top-at-mark-start"); 1450 st->print_cr("UWM=update watermark, U=used"); 1451 st->print_cr("T=TLAB allocs, G=GCLAB allocs"); 1452 st->print_cr("S=shared allocs, L=live data"); 1453 st->print_cr("CP=critical pins"); 1454 1455 for (size_t i = 0; i < num_regions(); i++) { 1456 get_region(i)->print_on(st); 1457 } 1458 } 1459 1460 size_t ShenandoahHeap::trash_humongous_region_at(ShenandoahHeapRegion* start) { 1461 assert(start->is_humongous_start(), "reclaim regions starting with the first one"); 1462 1463 oop humongous_obj = cast_to_oop(start->bottom()); 1464 size_t size = humongous_obj->size(); 1465 size_t required_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize); 1466 size_t index = start->index() + required_regions - 1; 1467 1468 assert(!start->has_live(), "liveness must be zero"); 1469 1470 for(size_t i = 0; i < required_regions; i++) { 1471 // Reclaim from tail. Otherwise, assertion fails when printing region to trace log, 1472 // as it expects that every region belongs to a humongous region starting with a humongous start region. 1473 ShenandoahHeapRegion* region = get_region(index --); 1474 1475 assert(region->is_humongous(), "expect correct humongous start or continuation"); 1476 assert(!region->is_cset(), "Humongous region should not be in collection set"); 1477 1478 region->make_trash_immediate(); 1479 } 1480 return required_regions; 1481 } 1482 1483 class ShenandoahCheckCleanGCLABClosure : public ThreadClosure { 1484 public: 1485 ShenandoahCheckCleanGCLABClosure() {} 1486 void do_thread(Thread* thread) { 1487 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread); 1488 assert(gclab != nullptr, "GCLAB should be initialized for %s", thread->name()); 1489 assert(gclab->words_remaining() == 0, "GCLAB should not need retirement"); 1490 1491 if (ShenandoahHeap::heap()->mode()->is_generational()) { 1492 PLAB* plab = ShenandoahThreadLocalData::plab(thread); 1493 assert(plab != nullptr, "PLAB should be initialized for %s", thread->name()); 1494 assert(plab->words_remaining() == 0, "PLAB should not need retirement"); 1495 } 1496 } 1497 }; 1498 1499 void ShenandoahHeap::labs_make_parsable() { 1500 assert(UseTLAB, "Only call with UseTLAB"); 1501 1502 ShenandoahRetireGCLABClosure cl(false); 1503 1504 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 1505 ThreadLocalAllocBuffer& tlab = t->tlab(); 1506 tlab.make_parsable(); 1507 cl.do_thread(t); 1508 } 1509 1510 workers()->threads_do(&cl); 1511 1512 if (safepoint_workers() != nullptr) { 1513 safepoint_workers()->threads_do(&cl); 1514 } 1515 } 1516 1517 void ShenandoahHeap::tlabs_retire(bool resize) { 1518 assert(UseTLAB, "Only call with UseTLAB"); 1519 assert(!resize || ResizeTLAB, "Only call for resize when ResizeTLAB is enabled"); 1520 1521 ThreadLocalAllocStats stats; 1522 1523 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 1524 ThreadLocalAllocBuffer& tlab = t->tlab(); 1525 tlab.retire(&stats); 1526 if (resize) { 1527 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 ShenandoahRendezvousClosure : public HandshakeClosure { 2027 public: 2028 inline ShenandoahRendezvousClosure(const char* name) : HandshakeClosure(name) {} 2029 inline void do_thread(Thread* thread) {} 2030 }; 2031 2032 void ShenandoahHeap::rendezvous_threads(const char* name) { 2033 ShenandoahRendezvousClosure 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 ShenandoahGCStatePropagator 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 uint num_workers = _workers->active_workers(); 2244 ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred); 2245 _workers->run_task(&unlink_task); 2246 } 2247 // Release unloaded nmethods's memory. 2248 ClassUnloadingContext::context()->purge_and_free_nmethods(); 2249 } 2250 2251 { 2252 ShenandoahGCPhase phase(full_gc ? 2253 ShenandoahPhaseTimings::full_gc_purge_cldg : 2254 ShenandoahPhaseTimings::degen_gc_purge_cldg); 2255 ClassLoaderDataGraph::purge(true /* at_safepoint */); 2256 } 2257 // Resize and verify metaspace 2258 MetaspaceGC::compute_new_size(); 2259 DEBUG_ONLY(MetaspaceUtils::verify();) 2260 } 2261 2262 // Weak roots are either pre-evacuated (final mark) or updated (final update refs), 2263 // so they should not have forwarded oops. 2264 // However, we do need to "null" dead oops in the roots, if can not be done 2265 // in concurrent cycles. 2266 void ShenandoahHeap::stw_process_weak_roots(bool full_gc) { 2267 uint num_workers = _workers->active_workers(); 2268 ShenandoahPhaseTimings::Phase timing_phase = full_gc ? 2269 ShenandoahPhaseTimings::full_gc_purge_weak_par : 2270 ShenandoahPhaseTimings::degen_gc_purge_weak_par; 2271 ShenandoahGCPhase phase(timing_phase); 2272 ShenandoahGCWorkerPhase worker_phase(timing_phase); 2273 // Cleanup weak roots 2274 if (has_forwarded_objects()) { 2275 ShenandoahForwardedIsAliveClosure is_alive; 2276 ShenandoahNonConcUpdateRefsClosure keep_alive; 2277 ShenandoahParallelWeakRootsCleaningTask<ShenandoahForwardedIsAliveClosure, ShenandoahNonConcUpdateRefsClosure> 2278 cleaning_task(timing_phase, &is_alive, &keep_alive, num_workers); 2279 _workers->run_task(&cleaning_task); 2280 } else { 2281 ShenandoahIsAliveClosure is_alive; 2282 #ifdef ASSERT 2283 ShenandoahAssertNotForwardedClosure verify_cl; 2284 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, ShenandoahAssertNotForwardedClosure> 2285 cleaning_task(timing_phase, &is_alive, &verify_cl, num_workers); 2286 #else 2287 ShenandoahParallelWeakRootsCleaningTask<ShenandoahIsAliveClosure, DoNothingClosure> 2288 cleaning_task(timing_phase, &is_alive, &do_nothing_cl, num_workers); 2289 #endif 2290 _workers->run_task(&cleaning_task); 2291 } 2292 } 2293 2294 void ShenandoahHeap::parallel_cleaning(bool full_gc) { 2295 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint"); 2296 assert(is_stw_gc_in_progress(), "Only for Degenerated and Full GC"); 2297 ShenandoahGCPhase phase(full_gc ? 2298 ShenandoahPhaseTimings::full_gc_purge : 2299 ShenandoahPhaseTimings::degen_gc_purge); 2300 stw_weak_refs(full_gc); 2301 stw_process_weak_roots(full_gc); 2302 stw_unload_classes(full_gc); 2303 } 2304 2305 void ShenandoahHeap::set_has_forwarded_objects(bool cond) { 2306 set_gc_state_at_safepoint(HAS_FORWARDED, cond); 2307 } 2308 2309 void ShenandoahHeap::set_unload_classes(bool uc) { 2310 _unload_classes.set_cond(uc); 2311 } 2312 2313 bool ShenandoahHeap::unload_classes() const { 2314 return _unload_classes.is_set(); 2315 } 2316 2317 address ShenandoahHeap::in_cset_fast_test_addr() { 2318 ShenandoahHeap* heap = ShenandoahHeap::heap(); 2319 assert(heap->collection_set() != nullptr, "Sanity"); 2320 return (address) heap->collection_set()->biased_map_address(); 2321 } 2322 2323 void ShenandoahHeap::reset_bytes_allocated_since_gc_start() { 2324 if (mode()->is_generational()) { 2325 young_generation()->reset_bytes_allocated_since_gc_start(); 2326 old_generation()->reset_bytes_allocated_since_gc_start(); 2327 } 2328 2329 global_generation()->reset_bytes_allocated_since_gc_start(); 2330 } 2331 2332 void ShenandoahHeap::set_degenerated_gc_in_progress(bool in_progress) { 2333 _degenerated_gc_in_progress.set_cond(in_progress); 2334 } 2335 2336 void ShenandoahHeap::set_full_gc_in_progress(bool in_progress) { 2337 _full_gc_in_progress.set_cond(in_progress); 2338 } 2339 2340 void ShenandoahHeap::set_full_gc_move_in_progress(bool in_progress) { 2341 assert (is_full_gc_in_progress(), "should be"); 2342 _full_gc_move_in_progress.set_cond(in_progress); 2343 } 2344 2345 void ShenandoahHeap::set_update_refs_in_progress(bool in_progress) { 2346 set_gc_state_at_safepoint(UPDATE_REFS, in_progress); 2347 } 2348 2349 void ShenandoahHeap::register_nmethod(nmethod* nm) { 2350 ShenandoahCodeRoots::register_nmethod(nm); 2351 } 2352 2353 void ShenandoahHeap::unregister_nmethod(nmethod* nm) { 2354 ShenandoahCodeRoots::unregister_nmethod(nm); 2355 } 2356 2357 void ShenandoahHeap::pin_object(JavaThread* thr, oop o) { 2358 heap_region_containing(o)->record_pin(); 2359 } 2360 2361 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) { 2362 ShenandoahHeapRegion* r = heap_region_containing(o); 2363 assert(r != nullptr, "Sanity"); 2364 assert(r->pin_count() > 0, "Region %zu should have non-zero pins", r->index()); 2365 r->record_unpin(); 2366 } 2367 2368 void ShenandoahHeap::sync_pinned_region_status() { 2369 ShenandoahHeapLocker locker(lock()); 2370 2371 for (size_t i = 0; i < num_regions(); i++) { 2372 ShenandoahHeapRegion *r = get_region(i); 2373 if (r->is_active()) { 2374 if (r->is_pinned()) { 2375 if (r->pin_count() == 0) { 2376 r->make_unpinned(); 2377 } 2378 } else { 2379 if (r->pin_count() > 0) { 2380 r->make_pinned(); 2381 } 2382 } 2383 } 2384 } 2385 2386 assert_pinned_region_status(); 2387 } 2388 2389 #ifdef ASSERT 2390 void ShenandoahHeap::assert_pinned_region_status() { 2391 for (size_t i = 0; i < num_regions(); i++) { 2392 ShenandoahHeapRegion* r = get_region(i); 2393 shenandoah_assert_generations_reconciled(); 2394 if (gc_generation()->contains(r)) { 2395 assert((r->is_pinned() && r->pin_count() > 0) || (!r->is_pinned() && r->pin_count() == 0), 2396 "Region %zu pinning status is inconsistent", i); 2397 } 2398 } 2399 } 2400 #endif 2401 2402 ConcurrentGCTimer* ShenandoahHeap::gc_timer() const { 2403 return _gc_timer; 2404 } 2405 2406 void ShenandoahHeap::prepare_concurrent_roots() { 2407 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint"); 2408 assert(!is_stw_gc_in_progress(), "Only concurrent GC"); 2409 set_concurrent_strong_root_in_progress(!collection_set()->is_empty()); 2410 set_concurrent_weak_root_in_progress(true); 2411 if (unload_classes()) { 2412 _unloader.prepare(); 2413 } 2414 } 2415 2416 void ShenandoahHeap::finish_concurrent_roots() { 2417 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint"); 2418 assert(!is_stw_gc_in_progress(), "Only concurrent GC"); 2419 if (unload_classes()) { 2420 _unloader.finish(); 2421 } 2422 } 2423 2424 #ifdef ASSERT 2425 void ShenandoahHeap::assert_gc_workers(uint nworkers) { 2426 assert(nworkers > 0 && nworkers <= max_workers(), "Sanity"); 2427 2428 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) { 2429 // Use ParallelGCThreads inside safepoints 2430 assert(nworkers == ParallelGCThreads, "Use ParallelGCThreads (%u) within safepoint, not %u", 2431 ParallelGCThreads, nworkers); 2432 } else { 2433 // Use ConcGCThreads outside safepoints 2434 assert(nworkers == ConcGCThreads, "Use ConcGCThreads (%u) outside safepoints, %u", 2435 ConcGCThreads, nworkers); 2436 } 2437 } 2438 #endif 2439 2440 ShenandoahVerifier* ShenandoahHeap::verifier() { 2441 guarantee(ShenandoahVerify, "Should be enabled"); 2442 assert (_verifier != nullptr, "sanity"); 2443 return _verifier; 2444 } 2445 2446 template<bool CONCURRENT> 2447 class ShenandoahUpdateHeapRefsTask : public WorkerTask { 2448 private: 2449 ShenandoahHeap* _heap; 2450 ShenandoahRegionIterator* _regions; 2451 public: 2452 explicit ShenandoahUpdateHeapRefsTask(ShenandoahRegionIterator* regions) : 2453 WorkerTask("Shenandoah Update References"), 2454 _heap(ShenandoahHeap::heap()), 2455 _regions(regions) { 2456 } 2457 2458 void work(uint worker_id) { 2459 if (CONCURRENT) { 2460 ShenandoahConcurrentWorkerSession worker_session(worker_id); 2461 ShenandoahSuspendibleThreadSetJoiner stsj; 2462 do_work<ShenandoahConcUpdateRefsClosure>(worker_id); 2463 } else { 2464 ShenandoahParallelWorkerSession worker_session(worker_id); 2465 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id); 2466 } 2467 } 2468 2469 private: 2470 template<class T> 2471 void do_work(uint worker_id) { 2472 if (CONCURRENT && (worker_id == 0)) { 2473 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the 2474 // results of evacuation. These reserves are no longer necessary because evacuation has completed. 2475 size_t cset_regions = _heap->collection_set()->count(); 2476 2477 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation 2478 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from 2479 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the 2480 // next GC cycle. 2481 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions); 2482 } 2483 // If !CONCURRENT, there's no value in expanding Mutator free set 2484 T cl; 2485 ShenandoahHeapRegion* r = _regions->next(); 2486 while (r != nullptr) { 2487 HeapWord* update_watermark = r->get_update_watermark(); 2488 assert (update_watermark >= r->bottom(), "sanity"); 2489 if (r->is_active() && !r->is_cset()) { 2490 _heap->marked_object_oop_iterate(r, &cl, update_watermark); 2491 if (ShenandoahPacing) { 2492 _heap->pacer()->report_update_refs(pointer_delta(update_watermark, r->bottom())); 2493 } 2494 } 2495 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) { 2496 return; 2497 } 2498 r = _regions->next(); 2499 } 2500 } 2501 }; 2502 2503 void ShenandoahHeap::update_heap_references(bool concurrent) { 2504 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC"); 2505 2506 if (concurrent) { 2507 ShenandoahUpdateHeapRefsTask<true> task(&_update_refs_iterator); 2508 workers()->run_task(&task); 2509 } else { 2510 ShenandoahUpdateHeapRefsTask<false> task(&_update_refs_iterator); 2511 workers()->run_task(&task); 2512 } 2513 } 2514 2515 void ShenandoahHeap::update_heap_region_states(bool concurrent) { 2516 assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint"); 2517 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC"); 2518 2519 { 2520 ShenandoahGCPhase phase(concurrent ? 2521 ShenandoahPhaseTimings::final_update_refs_update_region_states : 2522 ShenandoahPhaseTimings::degen_gc_final_update_refs_update_region_states); 2523 2524 final_update_refs_update_region_states(); 2525 2526 assert_pinned_region_status(); 2527 } 2528 2529 { 2530 ShenandoahGCPhase phase(concurrent ? 2531 ShenandoahPhaseTimings::final_update_refs_trash_cset : 2532 ShenandoahPhaseTimings::degen_gc_final_update_refs_trash_cset); 2533 trash_cset_regions(); 2534 } 2535 } 2536 2537 void ShenandoahHeap::final_update_refs_update_region_states() { 2538 ShenandoahSynchronizePinnedRegionStates cl; 2539 parallel_heap_region_iterate(&cl); 2540 } 2541 2542 void ShenandoahHeap::rebuild_free_set(bool concurrent) { 2543 ShenandoahGCPhase phase(concurrent ? 2544 ShenandoahPhaseTimings::final_update_refs_rebuild_freeset : 2545 ShenandoahPhaseTimings::degen_gc_final_update_refs_rebuild_freeset); 2546 ShenandoahHeapLocker locker(lock()); 2547 size_t young_cset_regions, old_cset_regions; 2548 size_t first_old_region, last_old_region, old_region_count; 2549 _free_set->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count); 2550 // If there are no old regions, first_old_region will be greater than last_old_region 2551 assert((first_old_region > last_old_region) || 2552 ((last_old_region + 1 - first_old_region >= old_region_count) && 2553 get_region(first_old_region)->is_old() && get_region(last_old_region)->is_old()), 2554 "sanity: old_region_count: %zu, first_old_region: %zu, last_old_region: %zu", 2555 old_region_count, first_old_region, last_old_region); 2556 2557 if (mode()->is_generational()) { 2558 #ifdef ASSERT 2559 if (ShenandoahVerify) { 2560 verifier()->verify_before_rebuilding_free_set(); 2561 } 2562 #endif 2563 2564 // The computation of bytes_of_allocation_runway_before_gc_trigger is quite conservative so consider all of this 2565 // available for transfer to old. Note that transfer of humongous regions does not impact available. 2566 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap(); 2567 size_t allocation_runway = gen_heap->young_generation()->heuristics()->bytes_of_allocation_runway_before_gc_trigger(young_cset_regions); 2568 gen_heap->compute_old_generation_balance(allocation_runway, old_cset_regions); 2569 2570 // Total old_available may have been expanded to hold anticipated promotions. We trigger if the fragmented available 2571 // memory represents more than 16 regions worth of data. Note that fragmentation may increase when we promote regular 2572 // regions in place when many of these regular regions have an abundant amount of available memory within them. Fragmentation 2573 // will decrease as promote-by-copy consumes the available memory within these partially consumed regions. 2574 // 2575 // We consider old-gen to have excessive fragmentation if more than 12.5% of old-gen is free memory that resides 2576 // within partially consumed regions of memory. 2577 } 2578 // Rebuild free set based on adjusted generation sizes. 2579 _free_set->finish_rebuild(young_cset_regions, old_cset_regions, old_region_count); 2580 2581 if (mode()->is_generational()) { 2582 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap(); 2583 ShenandoahOldGeneration* old_gen = gen_heap->old_generation(); 2584 old_gen->heuristics()->evaluate_triggers(first_old_region, last_old_region, old_region_count, num_regions()); 2585 } 2586 } 2587 2588 bool ShenandoahHeap::is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self) { 2589 size_t slice = r->index() / _bitmap_regions_per_slice; 2590 2591 size_t regions_from = _bitmap_regions_per_slice * slice; 2592 size_t regions_to = MIN2(num_regions(), _bitmap_regions_per_slice * (slice + 1)); 2593 for (size_t g = regions_from; g < regions_to; g++) { 2594 assert (g / _bitmap_regions_per_slice == slice, "same slice"); 2595 if (skip_self && g == r->index()) continue; 2596 if (get_region(g)->is_committed()) { 2597 return true; 2598 } 2599 } 2600 return false; 2601 } 2602 2603 bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) { 2604 shenandoah_assert_heaplocked(); 2605 2606 // Bitmaps in special regions do not need commits 2607 if (_bitmap_region_special) { 2608 return true; 2609 } 2610 2611 if (is_bitmap_slice_committed(r, true)) { 2612 // Some other region from the group is already committed, meaning the bitmap 2613 // slice is already committed, we exit right away. 2614 return true; 2615 } 2616 2617 // Commit the bitmap slice: 2618 size_t slice = r->index() / _bitmap_regions_per_slice; 2619 size_t off = _bitmap_bytes_per_slice * slice; 2620 size_t len = _bitmap_bytes_per_slice; 2621 char* start = (char*) _bitmap_region.start() + off; 2622 2623 if (!os::commit_memory(start, len, false)) { 2624 return false; 2625 } 2626 2627 if (AlwaysPreTouch) { 2628 os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size); 2629 } 2630 2631 return true; 2632 } 2633 2634 bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) { 2635 shenandoah_assert_heaplocked(); 2636 2637 // Bitmaps in special regions do not need uncommits 2638 if (_bitmap_region_special) { 2639 return true; 2640 } 2641 2642 if (is_bitmap_slice_committed(r, true)) { 2643 // Some other region from the group is still committed, meaning the bitmap 2644 // slice should stay committed, exit right away. 2645 return true; 2646 } 2647 2648 // Uncommit the bitmap slice: 2649 size_t slice = r->index() / _bitmap_regions_per_slice; 2650 size_t off = _bitmap_bytes_per_slice * slice; 2651 size_t len = _bitmap_bytes_per_slice; 2652 if (!os::uncommit_memory((char*)_bitmap_region.start() + off, len)) { 2653 return false; 2654 } 2655 return true; 2656 } 2657 2658 void ShenandoahHeap::forbid_uncommit() { 2659 if (_uncommit_thread != nullptr) { 2660 _uncommit_thread->forbid_uncommit(); 2661 } 2662 } 2663 2664 void ShenandoahHeap::allow_uncommit() { 2665 if (_uncommit_thread != nullptr) { 2666 _uncommit_thread->allow_uncommit(); 2667 } 2668 } 2669 2670 #ifdef ASSERT 2671 bool ShenandoahHeap::is_uncommit_in_progress() { 2672 if (_uncommit_thread != nullptr) { 2673 return _uncommit_thread->is_uncommit_in_progress(); 2674 } 2675 return false; 2676 } 2677 #endif 2678 2679 void ShenandoahHeap::safepoint_synchronize_begin() { 2680 StackWatermarkSet::safepoint_synchronize_begin(); 2681 SuspendibleThreadSet::synchronize(); 2682 } 2683 2684 void ShenandoahHeap::safepoint_synchronize_end() { 2685 SuspendibleThreadSet::desynchronize(); 2686 } 2687 2688 void ShenandoahHeap::try_inject_alloc_failure() { 2689 if (ShenandoahAllocFailureALot && !cancelled_gc() && ((os::random() % 1000) > 950)) { 2690 _inject_alloc_failure.set(); 2691 os::naked_short_sleep(1); 2692 if (cancelled_gc()) { 2693 log_info(gc)("Allocation failure was successfully injected"); 2694 } 2695 } 2696 } 2697 2698 bool ShenandoahHeap::should_inject_alloc_failure() { 2699 return _inject_alloc_failure.is_set() && _inject_alloc_failure.try_unset(); 2700 } 2701 2702 void ShenandoahHeap::initialize_serviceability() { 2703 _memory_pool = new ShenandoahMemoryPool(this); 2704 _cycle_memory_manager.add_pool(_memory_pool); 2705 _stw_memory_manager.add_pool(_memory_pool); 2706 } 2707 2708 GrowableArray<GCMemoryManager*> ShenandoahHeap::memory_managers() { 2709 GrowableArray<GCMemoryManager*> memory_managers(2); 2710 memory_managers.append(&_cycle_memory_manager); 2711 memory_managers.append(&_stw_memory_manager); 2712 return memory_managers; 2713 } 2714 2715 GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() { 2716 GrowableArray<MemoryPool*> memory_pools(1); 2717 memory_pools.append(_memory_pool); 2718 return memory_pools; 2719 } 2720 2721 MemoryUsage ShenandoahHeap::memory_usage() { 2722 return MemoryUsage(_initial_size, used(), committed(), max_capacity()); 2723 } 2724 2725 ShenandoahRegionIterator::ShenandoahRegionIterator() : 2726 _heap(ShenandoahHeap::heap()), 2727 _index(0) {} 2728 2729 ShenandoahRegionIterator::ShenandoahRegionIterator(ShenandoahHeap* heap) : 2730 _heap(heap), 2731 _index(0) {} 2732 2733 void ShenandoahRegionIterator::reset() { 2734 _index = 0; 2735 } 2736 2737 bool ShenandoahRegionIterator::has_next() const { 2738 return _index < _heap->num_regions(); 2739 } 2740 2741 char ShenandoahHeap::gc_state() const { 2742 return _gc_state.raw_value(); 2743 } 2744 2745 bool ShenandoahHeap::is_gc_state(GCState state) const { 2746 // If the global gc state has been changed, but hasn't yet been propagated to all threads, then 2747 // the global gc state is the correct value. Once the gc state has been synchronized with all threads, 2748 // _gc_state_changed will be toggled to false and we need to use the thread local state. 2749 return _gc_state_changed ? _gc_state.is_set(state) : ShenandoahThreadLocalData::is_gc_state(state); 2750 } 2751 2752 2753 ShenandoahLiveData* ShenandoahHeap::get_liveness_cache(uint worker_id) { 2754 #ifdef ASSERT 2755 assert(_liveness_cache != nullptr, "sanity"); 2756 assert(worker_id < _max_workers, "sanity"); 2757 for (uint i = 0; i < num_regions(); i++) { 2758 assert(_liveness_cache[worker_id][i] == 0, "liveness cache should be empty"); 2759 } 2760 #endif 2761 return _liveness_cache[worker_id]; 2762 } 2763 2764 void ShenandoahHeap::flush_liveness_cache(uint worker_id) { 2765 assert(worker_id < _max_workers, "sanity"); 2766 assert(_liveness_cache != nullptr, "sanity"); 2767 ShenandoahLiveData* ld = _liveness_cache[worker_id]; 2768 for (uint i = 0; i < num_regions(); i++) { 2769 ShenandoahLiveData live = ld[i]; 2770 if (live > 0) { 2771 ShenandoahHeapRegion* r = get_region(i); 2772 r->increase_live_data_gc_words(live); 2773 ld[i] = 0; 2774 } 2775 } 2776 } 2777 2778 bool ShenandoahHeap::requires_barriers(stackChunkOop obj) const { 2779 if (is_idle()) return false; 2780 2781 // Objects allocated after marking start are implicitly alive, don't need any barriers during 2782 // marking phase. 2783 if (is_concurrent_mark_in_progress() && 2784 !marking_context()->allocated_after_mark_start(obj)) { 2785 return true; 2786 } 2787 2788 // Can not guarantee obj is deeply good. 2789 if (has_forwarded_objects()) { 2790 return true; 2791 } 2792 2793 return false; 2794 } 2795 2796 HeapWord* ShenandoahHeap::allocate_loaded_archive_space(size_t size) { 2797 #if INCLUDE_CDS_JAVA_HEAP 2798 // CDS wants a continuous memory range to load a bunch of objects. 2799 // This effectively bypasses normal allocation paths, and requires 2800 // a bit of massaging to unbreak GC invariants. 2801 2802 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared(size); 2803 2804 // Easy case: a single regular region, no further adjustments needed. 2805 if (!ShenandoahHeapRegion::requires_humongous(size)) { 2806 return allocate_memory(req); 2807 } 2808 2809 // Hard case: the requested size would cause a humongous allocation. 2810 // We need to make sure it looks like regular allocation to the rest of GC. 2811 2812 // CDS code would guarantee no objects straddle multiple regions, as long as 2813 // regions are as large as MIN_GC_REGION_ALIGNMENT. It is impractical at this 2814 // point to deal with case when Shenandoah runs with smaller regions. 2815 // TODO: This check can be dropped once MIN_GC_REGION_ALIGNMENT agrees more with Shenandoah. 2816 if (ShenandoahHeapRegion::region_size_bytes() < ArchiveHeapWriter::MIN_GC_REGION_ALIGNMENT) { 2817 return nullptr; 2818 } 2819 2820 HeapWord* mem = allocate_memory(req); 2821 size_t start_idx = heap_region_index_containing(mem); 2822 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize); 2823 2824 // Flip humongous -> regular. 2825 { 2826 ShenandoahHeapLocker locker(lock(), false); 2827 for (size_t c = start_idx; c < start_idx + num_regions; c++) { 2828 get_region(c)->make_regular_bypass(); 2829 } 2830 } 2831 2832 return mem; 2833 #else 2834 assert(false, "Archive heap loader should not be available, should not be here"); 2835 return nullptr; 2836 #endif // INCLUDE_CDS_JAVA_HEAP 2837 } 2838 2839 void ShenandoahHeap::complete_loaded_archive_space(MemRegion archive_space) { 2840 // Nothing to do here, except checking that heap looks fine. 2841 #ifdef ASSERT 2842 HeapWord* start = archive_space.start(); 2843 HeapWord* end = archive_space.end(); 2844 2845 // No unclaimed space between the objects. 2846 // Objects are properly allocated in correct regions. 2847 HeapWord* cur = start; 2848 while (cur < end) { 2849 oop oop = cast_to_oop(cur); 2850 shenandoah_assert_in_correct_region(nullptr, oop); 2851 cur += oop->size(); 2852 } 2853 2854 // No unclaimed tail at the end of archive space. 2855 assert(cur == end, 2856 "Archive space should be fully used: " PTR_FORMAT " " PTR_FORMAT, 2857 p2i(cur), p2i(end)); 2858 2859 // Region bounds are good. 2860 ShenandoahHeapRegion* begin_reg = heap_region_containing(start); 2861 ShenandoahHeapRegion* end_reg = heap_region_containing(end); 2862 assert(begin_reg->is_regular(), "Must be"); 2863 assert(end_reg->is_regular(), "Must be"); 2864 assert(begin_reg->bottom() == start, 2865 "Must agree: archive-space-start: " PTR_FORMAT ", begin-region-bottom: " PTR_FORMAT, 2866 p2i(start), p2i(begin_reg->bottom())); 2867 assert(end_reg->top() == end, 2868 "Must agree: archive-space-end: " PTR_FORMAT ", end-region-top: " PTR_FORMAT, 2869 p2i(end), p2i(end_reg->top())); 2870 #endif 2871 } 2872 2873 ShenandoahGeneration* ShenandoahHeap::generation_for(ShenandoahAffiliation affiliation) const { 2874 if (!mode()->is_generational()) { 2875 return global_generation(); 2876 } else if (affiliation == YOUNG_GENERATION) { 2877 return young_generation(); 2878 } else if (affiliation == OLD_GENERATION) { 2879 return old_generation(); 2880 } 2881 2882 ShouldNotReachHere(); 2883 return nullptr; 2884 } 2885 2886 void ShenandoahHeap::log_heap_status(const char* msg) const { 2887 if (mode()->is_generational()) { 2888 young_generation()->log_status(msg); 2889 old_generation()->log_status(msg); 2890 } else { 2891 global_generation()->log_status(msg); 2892 } 2893 }