1 /* 2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP 27 28 #include "gc/shared/gcCause.hpp" 29 #include "gc/shared/gcWhen.hpp" 30 #include "memory/allocation.hpp" 31 #include "runtime/handles.hpp" 32 #include "runtime/perfData.hpp" 33 #include "runtime/safepoint.hpp" 34 #include "utilities/debug.hpp" 35 #include "utilities/events.hpp" 36 #include "utilities/formatBuffer.hpp" 37 #include "utilities/growableArray.hpp" 38 39 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This 40 // is an abstract class: there may be many different kinds of heaps. This 41 // class defines the functions that a heap must implement, and contains 42 // infrastructure common to all heaps. 43 44 class AdaptiveSizePolicy; 45 class BarrierSet; 46 class CollectorPolicy; 47 class GCHeapSummary; 48 class GCTimer; 49 class GCTracer; 50 class GCMemoryManager; 51 class MemoryPool; 52 class MetaspaceSummary; 53 class Thread; 54 class ThreadClosure; 55 class VirtualSpaceSummary; 56 class WorkGang; 57 class nmethod; 58 59 class GCMessage : public FormatBuffer<1024> { 60 public: 61 bool is_before; 62 63 public: 64 GCMessage() {} 65 }; 66 67 class CollectedHeap; 68 69 class GCHeapLog : public EventLogBase<GCMessage> { 70 private: 71 void log_heap(CollectedHeap* heap, bool before); 72 73 public: 74 GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {} 75 76 void log_heap_before(CollectedHeap* heap) { 77 log_heap(heap, true); 78 } 79 void log_heap_after(CollectedHeap* heap) { 80 log_heap(heap, false); 81 } 82 }; 83 84 // 85 // CollectedHeap 86 // GenCollectedHeap 87 // SerialHeap 88 // CMSHeap 89 // G1CollectedHeap 90 // ParallelScavengeHeap 91 // 92 class CollectedHeap : public CHeapObj<mtInternal> { 93 friend class VMStructs; 94 friend class JVMCIVMStructs; 95 friend class IsGCActiveMark; // Block structured external access to _is_gc_active 96 97 private: 98 #ifdef ASSERT 99 static int _fire_out_of_memory_count; 100 #endif 101 102 GCHeapLog* _gc_heap_log; 103 104 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 105 // or INCLUDE_JVMCI is being used 106 bool _defer_initial_card_mark; 107 108 MemRegion _reserved; 109 110 protected: 111 BarrierSet* _barrier_set; 112 bool _is_gc_active; 113 114 // Used for filler objects (static, but initialized in ctor). 115 static size_t _filler_array_max_size; 116 117 unsigned int _total_collections; // ... started 118 unsigned int _total_full_collections; // ... started 119 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;) 120 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;) 121 122 // Reason for current garbage collection. Should be set to 123 // a value reflecting no collection between collections. 124 GCCause::Cause _gc_cause; 125 GCCause::Cause _gc_lastcause; 126 PerfStringVariable* _perf_gc_cause; 127 PerfStringVariable* _perf_gc_lastcause; 128 129 // Constructor 130 CollectedHeap(); 131 132 // Do common initializations that must follow instance construction, 133 // for example, those needing virtual calls. 134 // This code could perhaps be moved into initialize() but would 135 // be slightly more awkward because we want the latter to be a 136 // pure virtual. 137 void pre_initialize(); 138 139 // Create a new tlab. All TLAB allocations must go through this. 140 virtual HeapWord* allocate_new_tlab(size_t size); 141 142 // Accumulate statistics on all tlabs. 143 virtual void accumulate_statistics_all_tlabs(); 144 145 // Reinitialize tlabs before resuming mutators. 146 virtual void resize_all_tlabs(); 147 148 // Allocate from the current thread's TLAB, with broken-out slow path. 149 inline static HeapWord* allocate_from_tlab(Klass* klass, Thread* thread, size_t size); 150 static HeapWord* allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size); 151 152 // Sample the allocation via HeapMonitoring. 153 // overflowed_words represents the number of HeapWords that went past the 154 // sampling boundary. This is used to fix the next sampling rate. 155 static void sample_allocation(Thread* thread, HeapWord* obj, size_t size, 156 size_t overflowed_words = 0); 157 // Try to allocate the object we want to sample in this tlab, returns NULL if 158 // fails to allocate. 159 static HeapWord* allocate_sampled_object(Thread* thread, size_t size); 160 161 // Allocate an uninitialized block of the given size, or returns NULL if 162 // this is impossible. 163 inline static HeapWord* common_mem_allocate_noinit(Klass* klass, size_t size, TRAPS); 164 165 // Like allocate_init, but the block returned by a successful allocation 166 // is guaranteed initialized to zeros. 167 inline static HeapWord* common_mem_allocate_init(Klass* klass, size_t size, TRAPS); 168 169 // Helper functions for (VM) allocation. 170 inline static void post_allocation_setup_common(Klass* klass, HeapWord* obj); 171 inline static void post_allocation_setup_no_klass_install(Klass* klass, 172 HeapWord* objPtr); 173 174 inline static void post_allocation_setup_obj(Klass* klass, HeapWord* obj, int size); 175 176 inline static void post_allocation_setup_array(Klass* klass, 177 HeapWord* obj, int length); 178 179 inline static void post_allocation_setup_class(Klass* klass, HeapWord* obj, int size); 180 181 // Clears an allocated object. 182 inline static void init_obj(HeapWord* obj, size_t size); 183 184 // Filler object utilities. 185 static inline size_t filler_array_hdr_size(); 186 static inline size_t filler_array_min_size(); 187 188 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);) 189 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);) 190 191 // Fill with a single array; caller must ensure filler_array_min_size() <= 192 // words <= filler_array_max_size(). 193 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true); 194 195 // Fill with a single object (either an int array or a java.lang.Object). 196 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true); 197 198 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer); 199 200 // Verification functions 201 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size) 202 PRODUCT_RETURN; 203 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) 204 PRODUCT_RETURN; 205 debug_only(static void check_for_valid_allocation_state();) 206 207 public: 208 enum Name { 209 SerialHeap, 210 ParallelScavengeHeap, 211 G1CollectedHeap, 212 CMSHeap 213 }; 214 215 static inline size_t filler_array_max_size() { 216 return _filler_array_max_size; 217 } 218 219 virtual Name kind() const = 0; 220 221 virtual const char* name() const = 0; 222 223 /** 224 * Returns JNI error code JNI_ENOMEM if memory could not be allocated, 225 * and JNI_OK on success. 226 */ 227 virtual jint initialize() = 0; 228 229 // In many heaps, there will be a need to perform some initialization activities 230 // after the Universe is fully formed, but before general heap allocation is allowed. 231 // This is the correct place to place such initialization methods. 232 virtual void post_initialize(); 233 234 // Stop any onging concurrent work and prepare for exit. 235 virtual void stop() {} 236 237 // Stop and resume concurrent GC threads interfering with safepoint operations 238 virtual void safepoint_synchronize_begin() {} 239 virtual void safepoint_synchronize_end() {} 240 241 void initialize_reserved_region(HeapWord *start, HeapWord *end); 242 MemRegion reserved_region() const { return _reserved; } 243 address base() const { return (address)reserved_region().start(); } 244 245 virtual size_t capacity() const = 0; 246 virtual size_t used() const = 0; 247 248 // Return "true" if the part of the heap that allocates Java 249 // objects has reached the maximal committed limit that it can 250 // reach, without a garbage collection. 251 virtual bool is_maximal_no_gc() const = 0; 252 253 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of 254 // memory that the vm could make available for storing 'normal' java objects. 255 // This is based on the reserved address space, but should not include space 256 // that the vm uses internally for bookkeeping or temporary storage 257 // (e.g., in the case of the young gen, one of the survivor 258 // spaces). 259 virtual size_t max_capacity() const = 0; 260 261 // Returns "TRUE" if "p" points into the reserved area of the heap. 262 bool is_in_reserved(const void* p) const { 263 return _reserved.contains(p); 264 } 265 266 bool is_in_reserved_or_null(const void* p) const { 267 return p == NULL || is_in_reserved(p); 268 } 269 270 // Returns "TRUE" iff "p" points into the committed areas of the heap. 271 // This method can be expensive so avoid using it in performance critical 272 // code. 273 virtual bool is_in(const void* p) const = 0; 274 275 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); }) 276 277 // Let's define some terms: a "closed" subset of a heap is one that 278 // 279 // 1) contains all currently-allocated objects, and 280 // 281 // 2) is closed under reference: no object in the closed subset 282 // references one outside the closed subset. 283 // 284 // Membership in a heap's closed subset is useful for assertions. 285 // Clearly, the entire heap is a closed subset, so the default 286 // implementation is to use "is_in_reserved". But this may not be too 287 // liberal to perform useful checking. Also, the "is_in" predicate 288 // defines a closed subset, but may be too expensive, since "is_in" 289 // verifies that its argument points to an object head. The 290 // "closed_subset" method allows a heap to define an intermediate 291 // predicate, allowing more precise checking than "is_in_reserved" at 292 // lower cost than "is_in." 293 294 // One important case is a heap composed of disjoint contiguous spaces, 295 // such as the Garbage-First collector. Such heaps have a convenient 296 // closed subset consisting of the allocated portions of those 297 // contiguous spaces. 298 299 // Return "TRUE" iff the given pointer points into the heap's defined 300 // closed subset (which defaults to the entire heap). 301 virtual bool is_in_closed_subset(const void* p) const { 302 return is_in_reserved(p); 303 } 304 305 bool is_in_closed_subset_or_null(const void* p) const { 306 return p == NULL || is_in_closed_subset(p); 307 } 308 309 void set_gc_cause(GCCause::Cause v) { 310 if (UsePerfData) { 311 _gc_lastcause = _gc_cause; 312 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause)); 313 _perf_gc_cause->set_value(GCCause::to_string(v)); 314 } 315 _gc_cause = v; 316 } 317 GCCause::Cause gc_cause() { return _gc_cause; } 318 319 // General obj/array allocation facilities. 320 inline static oop obj_allocate(Klass* klass, int size, TRAPS); 321 inline static oop array_allocate(Klass* klass, int size, int length, TRAPS); 322 inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS); 323 inline static oop class_allocate(Klass* klass, int size, TRAPS); 324 325 // Raw memory allocation facilities 326 // The obj and array allocate methods are covers for these methods. 327 // mem_allocate() should never be 328 // called to allocate TLABs, only individual objects. 329 virtual HeapWord* mem_allocate(size_t size, 330 bool* gc_overhead_limit_was_exceeded) = 0; 331 332 // Utilities for turning raw memory into filler objects. 333 // 334 // min_fill_size() is the smallest region that can be filled. 335 // fill_with_objects() can fill arbitrary-sized regions of the heap using 336 // multiple objects. fill_with_object() is for regions known to be smaller 337 // than the largest array of integers; it uses a single object to fill the 338 // region and has slightly less overhead. 339 static size_t min_fill_size() { 340 return size_t(align_object_size(oopDesc::header_size())); 341 } 342 343 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true); 344 345 static void fill_with_object(HeapWord* start, size_t words, bool zap = true); 346 static void fill_with_object(MemRegion region, bool zap = true) { 347 fill_with_object(region.start(), region.word_size(), zap); 348 } 349 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) { 350 fill_with_object(start, pointer_delta(end, start), zap); 351 } 352 353 // Return the address "addr" aligned by "alignment_in_bytes" if such 354 // an address is below "end". Return NULL otherwise. 355 inline static HeapWord* align_allocation_or_fail(HeapWord* addr, 356 HeapWord* end, 357 unsigned short alignment_in_bytes); 358 359 // Some heaps may offer a contiguous region for shared non-blocking 360 // allocation, via inlined code (by exporting the address of the top and 361 // end fields defining the extent of the contiguous allocation region.) 362 363 // This function returns "true" iff the heap supports this kind of 364 // allocation. (Default is "no".) 365 virtual bool supports_inline_contig_alloc() const { 366 return false; 367 } 368 // These functions return the addresses of the fields that define the 369 // boundaries of the contiguous allocation area. (These fields should be 370 // physically near to one another.) 371 virtual HeapWord* volatile* top_addr() const { 372 guarantee(false, "inline contiguous allocation not supported"); 373 return NULL; 374 } 375 virtual HeapWord** end_addr() const { 376 guarantee(false, "inline contiguous allocation not supported"); 377 return NULL; 378 } 379 380 // Some heaps may be in an unparseable state at certain times between 381 // collections. This may be necessary for efficient implementation of 382 // certain allocation-related activities. Calling this function before 383 // attempting to parse a heap ensures that the heap is in a parsable 384 // state (provided other concurrent activity does not introduce 385 // unparsability). It is normally expected, therefore, that this 386 // method is invoked with the world stopped. 387 // NOTE: if you override this method, make sure you call 388 // super::ensure_parsability so that the non-generational 389 // part of the work gets done. See implementation of 390 // CollectedHeap::ensure_parsability and, for instance, 391 // that of GenCollectedHeap::ensure_parsability(). 392 // The argument "retire_tlabs" controls whether existing TLABs 393 // are merely filled or also retired, thus preventing further 394 // allocation from them and necessitating allocation of new TLABs. 395 virtual void ensure_parsability(bool retire_tlabs); 396 397 // Section on thread-local allocation buffers (TLABs) 398 // If the heap supports thread-local allocation buffers, it should override 399 // the following methods: 400 // Returns "true" iff the heap supports thread-local allocation buffers. 401 // The default is "no". 402 virtual bool supports_tlab_allocation() const = 0; 403 404 // The amount of space available for thread-local allocation buffers. 405 virtual size_t tlab_capacity(Thread *thr) const = 0; 406 407 // The amount of used space for thread-local allocation buffers for the given thread. 408 virtual size_t tlab_used(Thread *thr) const = 0; 409 410 virtual size_t max_tlab_size() const; 411 412 // An estimate of the maximum allocation that could be performed 413 // for thread-local allocation buffers without triggering any 414 // collection or expansion activity. 415 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const { 416 guarantee(false, "thread-local allocation buffers not supported"); 417 return 0; 418 } 419 420 // Can a compiler initialize a new object without store barriers? 421 // This permission only extends from the creation of a new object 422 // via a TLAB up to the first subsequent safepoint. If such permission 423 // is granted for this heap type, the compiler promises to call 424 // defer_store_barrier() below on any slow path allocation of 425 // a new object for which such initializing store barriers will 426 // have been elided. 427 virtual bool can_elide_tlab_store_barriers() const = 0; 428 429 // If a compiler is eliding store barriers for TLAB-allocated objects, 430 // there is probably a corresponding slow path which can produce 431 // an object allocated anywhere. The compiler's runtime support 432 // promises to call this function on such a slow-path-allocated 433 // object before performing initializations that have elided 434 // store barriers. Returns new_obj, or maybe a safer copy thereof. 435 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj); 436 437 // Answers whether an initializing store to a new object currently 438 // allocated at the given address doesn't need a store 439 // barrier. Returns "true" if it doesn't need an initializing 440 // store barrier; answers "false" if it does. 441 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0; 442 443 // If a compiler is eliding store barriers for TLAB-allocated objects, 444 // we will be informed of a slow-path allocation by a call 445 // to new_store_pre_barrier() above. Such a call precedes the 446 // initialization of the object itself, and no post-store-barriers will 447 // be issued. Some heap types require that the barrier strictly follows 448 // the initializing stores. (This is currently implemented by deferring the 449 // barrier until the next slow-path allocation or gc-related safepoint.) 450 // This interface answers whether a particular heap type needs the card 451 // mark to be thus strictly sequenced after the stores. 452 virtual bool card_mark_must_follow_store() const = 0; 453 454 // If the CollectedHeap was asked to defer a store barrier above, 455 // this informs it to flush such a deferred store barrier to the 456 // remembered set. 457 virtual void flush_deferred_store_barrier(JavaThread* thread); 458 459 // Perform a collection of the heap; intended for use in implementing 460 // "System.gc". This probably implies as full a collection as the 461 // "CollectedHeap" supports. 462 virtual void collect(GCCause::Cause cause) = 0; 463 464 // Perform a full collection 465 virtual void do_full_collection(bool clear_all_soft_refs) = 0; 466 467 // This interface assumes that it's being called by the 468 // vm thread. It collects the heap assuming that the 469 // heap lock is already held and that we are executing in 470 // the context of the vm thread. 471 virtual void collect_as_vm_thread(GCCause::Cause cause); 472 473 // Returns the barrier set for this heap 474 BarrierSet* barrier_set() { return _barrier_set; } 475 void set_barrier_set(BarrierSet* barrier_set); 476 477 // Returns "true" iff there is a stop-world GC in progress. (I assume 478 // that it should answer "false" for the concurrent part of a concurrent 479 // collector -- dld). 480 bool is_gc_active() const { return _is_gc_active; } 481 482 // Total number of GC collections (started) 483 unsigned int total_collections() const { return _total_collections; } 484 unsigned int total_full_collections() const { return _total_full_collections;} 485 486 // Increment total number of GC collections (started) 487 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2 488 void increment_total_collections(bool full = false) { 489 _total_collections++; 490 if (full) { 491 increment_total_full_collections(); 492 } 493 } 494 495 void increment_total_full_collections() { _total_full_collections++; } 496 497 // Return the CollectorPolicy for the heap 498 virtual CollectorPolicy* collector_policy() const = 0; 499 500 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0; 501 virtual GrowableArray<MemoryPool*> memory_pools() = 0; 502 503 // Iterate over all objects, calling "cl.do_object" on each. 504 virtual void object_iterate(ObjectClosure* cl) = 0; 505 506 // Similar to object_iterate() except iterates only 507 // over live objects. 508 virtual void safe_object_iterate(ObjectClosure* cl) = 0; 509 510 // NOTE! There is no requirement that a collector implement these 511 // functions. 512 // 513 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 514 // each address in the (reserved) heap is a member of exactly 515 // one block. The defining characteristic of a block is that it is 516 // possible to find its size, and thus to progress forward to the next 517 // block. (Blocks may be of different sizes.) Thus, blocks may 518 // represent Java objects, or they might be free blocks in a 519 // free-list-based heap (or subheap), as long as the two kinds are 520 // distinguishable and the size of each is determinable. 521 522 // Returns the address of the start of the "block" that contains the 523 // address "addr". We say "blocks" instead of "object" since some heaps 524 // may not pack objects densely; a chunk may either be an object or a 525 // non-object. 526 virtual HeapWord* block_start(const void* addr) const = 0; 527 528 // Requires "addr" to be the start of a chunk, and returns its size. 529 // "addr + size" is required to be the start of a new chunk, or the end 530 // of the active area of the heap. 531 virtual size_t block_size(const HeapWord* addr) const = 0; 532 533 // Requires "addr" to be the start of a block, and returns "TRUE" iff 534 // the block is an object. 535 virtual bool block_is_obj(const HeapWord* addr) const = 0; 536 537 // Returns the longest time (in ms) that has elapsed since the last 538 // time that any part of the heap was examined by a garbage collection. 539 virtual jlong millis_since_last_gc() = 0; 540 541 // Perform any cleanup actions necessary before allowing a verification. 542 virtual void prepare_for_verify() = 0; 543 544 // Generate any dumps preceding or following a full gc 545 private: 546 void full_gc_dump(GCTimer* timer, bool before); 547 548 virtual void initialize_serviceability() = 0; 549 550 public: 551 void pre_full_gc_dump(GCTimer* timer); 552 void post_full_gc_dump(GCTimer* timer); 553 554 VirtualSpaceSummary create_heap_space_summary(); 555 GCHeapSummary create_heap_summary(); 556 557 MetaspaceSummary create_metaspace_summary(); 558 559 // Print heap information on the given outputStream. 560 virtual void print_on(outputStream* st) const = 0; 561 // The default behavior is to call print_on() on tty. 562 virtual void print() const { 563 print_on(tty); 564 } 565 // Print more detailed heap information on the given 566 // outputStream. The default behavior is to call print_on(). It is 567 // up to each subclass to override it and add any additional output 568 // it needs. 569 virtual void print_extended_on(outputStream* st) const { 570 print_on(st); 571 } 572 573 virtual void print_on_error(outputStream* st) const; 574 575 // Print all GC threads (other than the VM thread) 576 // used by this heap. 577 virtual void print_gc_threads_on(outputStream* st) const = 0; 578 // The default behavior is to call print_gc_threads_on() on tty. 579 void print_gc_threads() { 580 print_gc_threads_on(tty); 581 } 582 // Iterator for all GC threads (other than VM thread) 583 virtual void gc_threads_do(ThreadClosure* tc) const = 0; 584 585 // Print any relevant tracing info that flags imply. 586 // Default implementation does nothing. 587 virtual void print_tracing_info() const = 0; 588 589 void print_heap_before_gc(); 590 void print_heap_after_gc(); 591 592 // An object is scavengable if its location may move during a scavenge. 593 // (A scavenge is a GC which is not a full GC.) 594 virtual bool is_scavengable(oop obj) = 0; 595 // Registering and unregistering an nmethod (compiled code) with the heap. 596 // Override with specific mechanism for each specialized heap type. 597 virtual void register_nmethod(nmethod* nm) {} 598 virtual void unregister_nmethod(nmethod* nm) {} 599 virtual void verify_nmethod(nmethod* nmethod) {} 600 601 void trace_heap_before_gc(const GCTracer* gc_tracer); 602 void trace_heap_after_gc(const GCTracer* gc_tracer); 603 604 // Heap verification 605 virtual void verify(VerifyOption option) = 0; 606 607 // Return true if concurrent phase control (via 608 // request_concurrent_phase_control) is supported by this collector. 609 // The default implementation returns false. 610 virtual bool supports_concurrent_phase_control() const; 611 612 // Return a NULL terminated array of concurrent phase names provided 613 // by this collector. Supports Whitebox testing. These are the 614 // names recognized by request_concurrent_phase(). The default 615 // implementation returns an array of one NULL element. 616 virtual const char* const* concurrent_phases() const; 617 618 // Request the collector enter the indicated concurrent phase, and 619 // wait until it does so. Supports WhiteBox testing. Only one 620 // request may be active at a time. Phases are designated by name; 621 // the set of names and their meaning is GC-specific. Once the 622 // requested phase has been reached, the collector will attempt to 623 // avoid transitioning to a new phase until a new request is made. 624 // [Note: A collector might not be able to remain in a given phase. 625 // For example, a full collection might cancel an in-progress 626 // concurrent collection.] 627 // 628 // Returns true when the phase is reached. Returns false for an 629 // unknown phase. The default implementation returns false. 630 virtual bool request_concurrent_phase(const char* phase); 631 632 // Provides a thread pool to SafepointSynchronize to use 633 // for parallel safepoint cleanup. 634 // GCs that use a GC worker thread pool may want to share 635 // it for use during safepoint cleanup. This is only possible 636 // if the GC can pause and resume concurrent work (e.g. G1 637 // concurrent marking) for an intermittent non-GC safepoint. 638 // If this method returns NULL, SafepointSynchronize will 639 // perform cleanup tasks serially in the VMThread. 640 virtual WorkGang* get_safepoint_workers() { return NULL; } 641 642 // Non product verification and debugging. 643 #ifndef PRODUCT 644 // Support for PromotionFailureALot. Return true if it's time to cause a 645 // promotion failure. The no-argument version uses 646 // this->_promotion_failure_alot_count as the counter. 647 inline bool promotion_should_fail(volatile size_t* count); 648 inline bool promotion_should_fail(); 649 650 // Reset the PromotionFailureALot counters. Should be called at the end of a 651 // GC in which promotion failure occurred. 652 inline void reset_promotion_should_fail(volatile size_t* count); 653 inline void reset_promotion_should_fail(); 654 #endif // #ifndef PRODUCT 655 656 #ifdef ASSERT 657 static int fired_fake_oom() { 658 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt); 659 } 660 #endif 661 662 public: 663 // Copy the current allocation context statistics for the specified contexts. 664 // For each context in contexts, set the corresponding entries in the totals 665 // and accuracy arrays to the current values held by the statistics. Each 666 // array should be of length len. 667 // Returns true if there are more stats available. 668 virtual bool copy_allocation_context_stats(const jint* contexts, 669 jlong* totals, 670 jbyte* accuracy, 671 jint len) { 672 return false; 673 } 674 675 }; 676 677 // Class to set and reset the GC cause for a CollectedHeap. 678 679 class GCCauseSetter : StackObj { 680 CollectedHeap* _heap; 681 GCCause::Cause _previous_cause; 682 public: 683 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) { 684 assert(SafepointSynchronize::is_at_safepoint(), 685 "This method manipulates heap state without locking"); 686 _heap = heap; 687 _previous_cause = _heap->gc_cause(); 688 _heap->set_gc_cause(cause); 689 } 690 691 ~GCCauseSetter() { 692 assert(SafepointSynchronize::is_at_safepoint(), 693 "This method manipulates heap state without locking"); 694 _heap->set_gc_cause(_previous_cause); 695 } 696 }; 697 698 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP