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