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 // ShenandoahHeap 91 // ParallelScavengeHeap 92 // 93 class CollectedHeap : public CHeapObj<mtInternal> { 94 friend class VMStructs; 95 friend class JVMCIVMStructs; 96 friend class IsGCActiveMark; // Block structured external access to _is_gc_active 97 98 private: 99 #ifdef ASSERT 100 static int _fire_out_of_memory_count; 101 #endif 102 103 GCHeapLog* _gc_heap_log; 104 105 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 106 // or INCLUDE_JVMCI is being used 107 bool _defer_initial_card_mark; 108 109 MemRegion _reserved; 110 111 protected: 112 BarrierSet* _barrier_set; 113 bool _is_gc_active; 114 115 // Used for filler objects (static, but initialized in ctor). 116 static size_t _filler_array_max_size; 117 118 unsigned int _total_collections; // ... started 119 unsigned int _total_full_collections; // ... started 120 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;) 121 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;) 122 123 // Reason for current garbage collection. Should be set to 124 // a value reflecting no collection between collections. 125 GCCause::Cause _gc_cause; 126 GCCause::Cause _gc_lastcause; 127 PerfStringVariable* _perf_gc_cause; 128 PerfStringVariable* _perf_gc_lastcause; 129 130 // Constructor 131 CollectedHeap(); 132 133 // Do common initializations that must follow instance construction, 134 // for example, those needing virtual calls. 135 // This code could perhaps be moved into initialize() but would 136 // be slightly more awkward because we want the latter to be a 137 // pure virtual. 138 void pre_initialize(); 139 140 // Create a new tlab. All TLAB allocations must go through this. 141 virtual HeapWord* allocate_new_tlab(size_t size); 142 143 // Accumulate statistics on all tlabs. 144 virtual void accumulate_statistics_all_tlabs(); 145 146 // Reinitialize tlabs before resuming mutators. 147 virtual void resize_all_tlabs(); 148 149 // Allocate from the current thread's TLAB, with broken-out slow path. 150 inline static HeapWord* allocate_from_tlab(Klass* klass, Thread* thread, size_t size); 151 static HeapWord* allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size); 152 153 // Allocate an uninitialized block of the given size, or returns NULL if 154 // this is impossible. 155 inline static HeapWord* common_mem_allocate_noinit(Klass* klass, size_t size, TRAPS); 156 157 // Like allocate_init, but the block returned by a successful allocation 158 // is guaranteed initialized to zeros. 159 inline static HeapWord* common_mem_allocate_init(Klass* klass, size_t size, TRAPS); 160 161 // Helper functions for (VM) allocation. 162 inline static void post_allocation_setup_common(Klass* klass, HeapWord* obj); 163 inline static void post_allocation_setup_no_klass_install(Klass* klass, 164 HeapWord* objPtr); 165 166 inline static void post_allocation_setup_obj(Klass* klass, HeapWord* obj, int size); 167 168 inline static void post_allocation_setup_array(Klass* klass, 169 HeapWord* obj, int length); 170 171 inline static void post_allocation_setup_class(Klass* klass, HeapWord* obj, int size); 172 173 // Clears an allocated object. 174 inline static void init_obj(HeapWord* obj, size_t size); 175 176 // Filler object utilities. 177 static inline size_t filler_array_hdr_size(); 178 static inline size_t filler_array_min_size(); 179 180 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);) 181 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);) 182 183 // Fill with a single array; caller must ensure filler_array_min_size() <= 184 // words <= filler_array_max_size(). 185 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true); 186 187 // Fill with a single object (either an int array or a java.lang.Object). 188 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true); 189 190 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer); 191 192 // Verification functions 193 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size) 194 PRODUCT_RETURN; 195 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) 196 PRODUCT_RETURN; 197 debug_only(static void check_for_valid_allocation_state();) 198 199 public: 200 enum Name { 201 SerialHeap, 202 ParallelScavengeHeap, 203 G1CollectedHeap, 204 ShenandoahHeap, 205 CMSHeap 206 }; 207 208 static inline size_t filler_array_max_size() { 209 return _filler_array_max_size; 210 } 211 212 virtual Name kind() const = 0; 213 214 virtual HeapWord* tlab_post_allocation_setup(HeapWord* obj); 215 216 virtual const char* name() const = 0; 217 218 /** 219 * Returns JNI error code JNI_ENOMEM if memory could not be allocated, 220 * and JNI_OK on success. 221 */ 222 virtual jint initialize() = 0; 223 224 // In many heaps, there will be a need to perform some initialization activities 225 // after the Universe is fully formed, but before general heap allocation is allowed. 226 // This is the correct place to place such initialization methods. 227 virtual void post_initialize(); 228 229 // Stop any onging concurrent work and prepare for exit. 230 virtual void stop() {} 231 232 // Stop and resume concurrent GC threads interfering with safepoint operations 233 virtual void safepoint_synchronize_begin() {} 234 virtual void safepoint_synchronize_end() {} 235 236 void initialize_reserved_region(HeapWord *start, HeapWord *end); 237 MemRegion reserved_region() const { return _reserved; } 238 address base() const { return (address)reserved_region().start(); } 239 240 virtual size_t capacity() const = 0; 241 virtual size_t used() const = 0; 242 243 // Return "true" if the part of the heap that allocates Java 244 // objects has reached the maximal committed limit that it can 245 // reach, without a garbage collection. 246 virtual bool is_maximal_no_gc() const = 0; 247 248 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of 249 // memory that the vm could make available for storing 'normal' java objects. 250 // This is based on the reserved address space, but should not include space 251 // that the vm uses internally for bookkeeping or temporary storage 252 // (e.g., in the case of the young gen, one of the survivor 253 // spaces). 254 virtual size_t max_capacity() const = 0; 255 256 // Returns "TRUE" if "p" points into the reserved area of the heap. 257 bool is_in_reserved(const void* p) const { 258 return _reserved.contains(p); 259 } 260 261 bool is_in_reserved_or_null(const void* p) const { 262 return p == NULL || is_in_reserved(p); 263 } 264 265 // Returns "TRUE" iff "p" points into the committed areas of the heap. 266 // This method can be expensive so avoid using it in performance critical 267 // code. 268 virtual bool is_in(const void* p) const = 0; 269 270 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); }) 271 272 // Let's define some terms: a "closed" subset of a heap is one that 273 // 274 // 1) contains all currently-allocated objects, and 275 // 276 // 2) is closed under reference: no object in the closed subset 277 // references one outside the closed subset. 278 // 279 // Membership in a heap's closed subset is useful for assertions. 280 // Clearly, the entire heap is a closed subset, so the default 281 // implementation is to use "is_in_reserved". But this may not be too 282 // liberal to perform useful checking. Also, the "is_in" predicate 283 // defines a closed subset, but may be too expensive, since "is_in" 284 // verifies that its argument points to an object head. The 285 // "closed_subset" method allows a heap to define an intermediate 286 // predicate, allowing more precise checking than "is_in_reserved" at 287 // lower cost than "is_in." 288 289 // One important case is a heap composed of disjoint contiguous spaces, 290 // such as the Garbage-First collector. Such heaps have a convenient 291 // closed subset consisting of the allocated portions of those 292 // contiguous spaces. 293 294 // Return "TRUE" iff the given pointer points into the heap's defined 295 // closed subset (which defaults to the entire heap). 296 virtual bool is_in_closed_subset(const void* p) const { 297 return is_in_reserved(p); 298 } 299 300 bool is_in_closed_subset_or_null(const void* p) const { 301 return p == NULL || is_in_closed_subset(p); 302 } 303 304 void set_gc_cause(GCCause::Cause v) { 305 if (UsePerfData) { 306 _gc_lastcause = _gc_cause; 307 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause)); 308 _perf_gc_cause->set_value(GCCause::to_string(v)); 309 } 310 _gc_cause = v; 311 } 312 GCCause::Cause gc_cause() { return _gc_cause; } 313 314 // General obj/array allocation facilities. 315 inline static oop obj_allocate(Klass* klass, int size, TRAPS); 316 inline static oop array_allocate(Klass* klass, int size, int length, TRAPS); 317 inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS); 318 inline static oop class_allocate(Klass* klass, int size, TRAPS); 319 320 virtual uint oop_extra_words(); 321 322 #ifndef CC_INTERP 323 virtual void compile_prepare_oop(MacroAssembler* masm, Register obj); 324 #endif 325 326 // Raw memory allocation facilities 327 // The obj and array allocate methods are covers for these methods. 328 // mem_allocate() should never be 329 // called to allocate TLABs, only individual objects. 330 virtual HeapWord* mem_allocate(size_t size, 331 bool* gc_overhead_limit_was_exceeded) = 0; 332 333 // Utilities for turning raw memory into filler objects. 334 // 335 // min_fill_size() is the smallest region that can be filled. 336 // fill_with_objects() can fill arbitrary-sized regions of the heap using 337 // multiple objects. fill_with_object() is for regions known to be smaller 338 // than the largest array of integers; it uses a single object to fill the 339 // region and has slightly less overhead. 340 static size_t min_fill_size() { 341 return size_t(align_object_size(oopDesc::header_size())); 342 } 343 344 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true); 345 346 static void fill_with_object(HeapWord* start, size_t words, bool zap = true); 347 static void fill_with_object(MemRegion region, bool zap = true) { 348 fill_with_object(region.start(), region.word_size(), zap); 349 } 350 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) { 351 fill_with_object(start, pointer_delta(end, start), zap); 352 } 353 354 // Return the address "addr" aligned by "alignment_in_bytes" if such 355 // an address is below "end". Return NULL otherwise. 356 inline static HeapWord* align_allocation_or_fail(HeapWord* addr, 357 HeapWord* end, 358 unsigned short alignment_in_bytes); 359 360 // Some heaps may offer a contiguous region for shared non-blocking 361 // allocation, via inlined code (by exporting the address of the top and 362 // end fields defining the extent of the contiguous allocation region.) 363 364 // This function returns "true" iff the heap supports this kind of 365 // allocation. (Default is "no".) 366 virtual bool supports_inline_contig_alloc() const { 367 return false; 368 } 369 // These functions return the addresses of the fields that define the 370 // boundaries of the contiguous allocation area. (These fields should be 371 // physically near to one another.) 372 virtual HeapWord* volatile* top_addr() const { 373 guarantee(false, "inline contiguous allocation not supported"); 374 return NULL; 375 } 376 virtual HeapWord** end_addr() const { 377 guarantee(false, "inline contiguous allocation not supported"); 378 return NULL; 379 } 380 381 // Some heaps may be in an unparseable state at certain times between 382 // collections. This may be necessary for efficient implementation of 383 // certain allocation-related activities. Calling this function before 384 // attempting to parse a heap ensures that the heap is in a parsable 385 // state (provided other concurrent activity does not introduce 386 // unparsability). It is normally expected, therefore, that this 387 // method is invoked with the world stopped. 388 // NOTE: if you override this method, make sure you call 389 // super::ensure_parsability so that the non-generational 390 // part of the work gets done. See implementation of 391 // CollectedHeap::ensure_parsability and, for instance, 392 // that of GenCollectedHeap::ensure_parsability(). 393 // The argument "retire_tlabs" controls whether existing TLABs 394 // are merely filled or also retired, thus preventing further 395 // allocation from them and necessitating allocation of new TLABs. 396 virtual void ensure_parsability(bool retire_tlabs); 397 398 // Section on thread-local allocation buffers (TLABs) 399 // If the heap supports thread-local allocation buffers, it should override 400 // the following methods: 401 // Returns "true" iff the heap supports thread-local allocation buffers. 402 // The default is "no". 403 virtual bool supports_tlab_allocation() const = 0; 404 405 // The amount of space available for thread-local allocation buffers. 406 virtual size_t tlab_capacity(Thread *thr) const = 0; 407 408 // The amount of used space for thread-local allocation buffers for the given thread. 409 virtual size_t tlab_used(Thread *thr) const = 0; 410 411 virtual size_t max_tlab_size() const; 412 413 // An estimate of the maximum allocation that could be performed 414 // for thread-local allocation buffers without triggering any 415 // collection or expansion activity. 416 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const { 417 guarantee(false, "thread-local allocation buffers not supported"); 418 return 0; 419 } 420 421 // Can a compiler initialize a new object without store barriers? 422 // This permission only extends from the creation of a new object 423 // via a TLAB up to the first subsequent safepoint. If such permission 424 // is granted for this heap type, the compiler promises to call 425 // defer_store_barrier() below on any slow path allocation of 426 // a new object for which such initializing store barriers will 427 // have been elided. 428 virtual bool can_elide_tlab_store_barriers() const = 0; 429 430 // If a compiler is eliding store barriers for TLAB-allocated objects, 431 // there is probably a corresponding slow path which can produce 432 // an object allocated anywhere. The compiler's runtime support 433 // promises to call this function on such a slow-path-allocated 434 // object before performing initializations that have elided 435 // store barriers. Returns new_obj, or maybe a safer copy thereof. 436 virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj); 437 438 // Answers whether an initializing store to a new object currently 439 // allocated at the given address doesn't need a store 440 // barrier. Returns "true" if it doesn't need an initializing 441 // store barrier; answers "false" if it does. 442 virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0; 443 444 // If a compiler is eliding store barriers for TLAB-allocated objects, 445 // we will be informed of a slow-path allocation by a call 446 // to new_store_pre_barrier() above. Such a call precedes the 447 // initialization of the object itself, and no post-store-barriers will 448 // be issued. Some heap types require that the barrier strictly follows 449 // the initializing stores. (This is currently implemented by deferring the 450 // barrier until the next slow-path allocation or gc-related safepoint.) 451 // This interface answers whether a particular heap type needs the card 452 // mark to be thus strictly sequenced after the stores. 453 virtual bool card_mark_must_follow_store() const = 0; 454 455 // If the CollectedHeap was asked to defer a store barrier above, 456 // this informs it to flush such a deferred store barrier to the 457 // remembered set. 458 virtual void flush_deferred_store_barrier(JavaThread* thread); 459 460 // Perform a collection of the heap; intended for use in implementing 461 // "System.gc". This probably implies as full a collection as the 462 // "CollectedHeap" supports. 463 virtual void collect(GCCause::Cause cause) = 0; 464 465 // Perform a full collection 466 virtual void do_full_collection(bool clear_all_soft_refs) = 0; 467 468 // This interface assumes that it's being called by the 469 // vm thread. It collects the heap assuming that the 470 // heap lock is already held and that we are executing in 471 // the context of the vm thread. 472 virtual void collect_as_vm_thread(GCCause::Cause cause); 473 474 // Returns the barrier set for this heap 475 BarrierSet* barrier_set() { return _barrier_set; } 476 void set_barrier_set(BarrierSet* barrier_set); 477 478 // Returns "true" iff there is a stop-world GC in progress. (I assume 479 // that it should answer "false" for the concurrent part of a concurrent 480 // collector -- dld). 481 bool is_gc_active() const { return _is_gc_active; } 482 483 // Total number of GC collections (started) 484 unsigned int total_collections() const { return _total_collections; } 485 unsigned int total_full_collections() const { return _total_full_collections;} 486 487 // Increment total number of GC collections (started) 488 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2 489 void increment_total_collections(bool full = false) { 490 _total_collections++; 491 if (full) { 492 increment_total_full_collections(); 493 } 494 } 495 496 void increment_total_full_collections() { _total_full_collections++; } 497 498 // Return the CollectorPolicy for the heap 499 virtual CollectorPolicy* collector_policy() const = 0; 500 501 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0; 502 virtual GrowableArray<MemoryPool*> memory_pools() = 0; 503 504 // Iterate over all objects, calling "cl.do_object" on each. 505 virtual void object_iterate(ObjectClosure* cl) = 0; 506 507 // Similar to object_iterate() except iterates only 508 // over live objects. 509 virtual void safe_object_iterate(ObjectClosure* cl) = 0; 510 511 // NOTE! There is no requirement that a collector implement these 512 // functions. 513 // 514 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 515 // each address in the (reserved) heap is a member of exactly 516 // one block. The defining characteristic of a block is that it is 517 // possible to find its size, and thus to progress forward to the next 518 // block. (Blocks may be of different sizes.) Thus, blocks may 519 // represent Java objects, or they might be free blocks in a 520 // free-list-based heap (or subheap), as long as the two kinds are 521 // distinguishable and the size of each is determinable. 522 523 // Returns the address of the start of the "block" that contains the 524 // address "addr". We say "blocks" instead of "object" since some heaps 525 // may not pack objects densely; a chunk may either be an object or a 526 // non-object. 527 virtual HeapWord* block_start(const void* addr) const = 0; 528 529 // Requires "addr" to be the start of a chunk, and returns its size. 530 // "addr + size" is required to be the start of a new chunk, or the end 531 // of the active area of the heap. 532 virtual size_t block_size(const HeapWord* addr) const = 0; 533 534 // Requires "addr" to be the start of a block, and returns "TRUE" iff 535 // the block is an object. 536 virtual bool block_is_obj(const HeapWord* addr) const = 0; 537 538 // Returns the longest time (in ms) that has elapsed since the last 539 // time that any part of the heap was examined by a garbage collection. 540 virtual jlong millis_since_last_gc() = 0; 541 542 // Perform any cleanup actions necessary before allowing a verification. 543 virtual void prepare_for_verify() = 0; 544 545 // Generate any dumps preceding or following a full gc 546 private: 547 void full_gc_dump(GCTimer* timer, bool before); 548 549 virtual void initialize_serviceability() = 0; 550 551 public: 552 void pre_full_gc_dump(GCTimer* timer); 553 void post_full_gc_dump(GCTimer* timer); 554 555 VirtualSpaceSummary create_heap_space_summary(); 556 GCHeapSummary create_heap_summary(); 557 558 MetaspaceSummary create_metaspace_summary(); 559 560 // Print heap information on the given outputStream. 561 virtual void print_on(outputStream* st) const = 0; 562 // The default behavior is to call print_on() on tty. 563 virtual void print() const { 564 print_on(tty); 565 } 566 // Print more detailed heap information on the given 567 // outputStream. The default behavior is to call print_on(). It is 568 // up to each subclass to override it and add any additional output 569 // it needs. 570 virtual void print_extended_on(outputStream* st) const { 571 print_on(st); 572 } 573 574 virtual void print_on_error(outputStream* st) const; 575 576 // Print all GC threads (other than the VM thread) 577 // used by this heap. 578 virtual void print_gc_threads_on(outputStream* st) const = 0; 579 // The default behavior is to call print_gc_threads_on() on tty. 580 void print_gc_threads() { 581 print_gc_threads_on(tty); 582 } 583 // Iterator for all GC threads (other than VM thread) 584 virtual void gc_threads_do(ThreadClosure* tc) const = 0; 585 586 // Print any relevant tracing info that flags imply. 587 // Default implementation does nothing. 588 virtual void print_tracing_info() const = 0; 589 590 void print_heap_before_gc(); 591 void print_heap_after_gc(); 592 593 // An object is scavengable if its location may move during a scavenge. 594 // (A scavenge is a GC which is not a full GC.) 595 virtual bool is_scavengable(oop obj) = 0; 596 // Registering and unregistering an nmethod (compiled code) with the heap. 597 // Override with specific mechanism for each specialized heap type. 598 virtual void register_nmethod(nmethod* nm) {} 599 virtual void unregister_nmethod(nmethod* nm) {} 600 virtual void verify_nmethod(nmethod* nmethod) {} 601 602 void trace_heap_before_gc(const GCTracer* gc_tracer); 603 void trace_heap_after_gc(const GCTracer* gc_tracer); 604 605 // Heap verification 606 virtual void verify(VerifyOption option) = 0; 607 608 // Return true if concurrent phase control (via 609 // request_concurrent_phase_control) is supported by this collector. 610 // The default implementation returns false. 611 virtual bool supports_concurrent_phase_control() const; 612 613 // Return a NULL terminated array of concurrent phase names provided 614 // by this collector. Supports Whitebox testing. These are the 615 // names recognized by request_concurrent_phase(). The default 616 // implementation returns an array of one NULL element. 617 virtual const char* const* concurrent_phases() const; 618 619 // Request the collector enter the indicated concurrent phase, and 620 // wait until it does so. Supports WhiteBox testing. Only one 621 // request may be active at a time. Phases are designated by name; 622 // the set of names and their meaning is GC-specific. Once the 623 // requested phase has been reached, the collector will attempt to 624 // avoid transitioning to a new phase until a new request is made. 625 // [Note: A collector might not be able to remain in a given phase. 626 // For example, a full collection might cancel an in-progress 627 // concurrent collection.] 628 // 629 // Returns true when the phase is reached. Returns false for an 630 // unknown phase. The default implementation returns false. 631 virtual bool request_concurrent_phase(const char* phase); 632 633 // Provides a thread pool to SafepointSynchronize to use 634 // for parallel safepoint cleanup. 635 // GCs that use a GC worker thread pool may want to share 636 // it for use during safepoint cleanup. This is only possible 637 // if the GC can pause and resume concurrent work (e.g. G1 638 // concurrent marking) for an intermittent non-GC safepoint. 639 // If this method returns NULL, SafepointSynchronize will 640 // perform cleanup tasks serially in the VMThread. 641 virtual WorkGang* get_safepoint_workers() { return NULL; } 642 643 // Accumulate additional statistics from GCLABs. 644 virtual void accumulate_statistics_all_gclabs(); 645 646 // Support for object pinning. This is used by JNI Get*Critical() 647 // and Release*Critical() family of functions. If supported, the GC 648 // must guarantee that pinned objects never move. 649 virtual bool supports_object_pinning() const; 650 virtual oop pin_object(JavaThread* thread, oop obj); 651 virtual void unpin_object(JavaThread* thread, oop obj); 652 653 // Non product verification and debugging. 654 #ifndef PRODUCT 655 // Support for PromotionFailureALot. Return true if it's time to cause a 656 // promotion failure. The no-argument version uses 657 // this->_promotion_failure_alot_count as the counter. 658 inline bool promotion_should_fail(volatile size_t* count); 659 inline bool promotion_should_fail(); 660 661 // Reset the PromotionFailureALot counters. Should be called at the end of a 662 // GC in which promotion failure occurred. 663 inline void reset_promotion_should_fail(volatile size_t* count); 664 inline void reset_promotion_should_fail(); 665 #endif // #ifndef PRODUCT 666 667 #ifdef ASSERT 668 static int fired_fake_oom() { 669 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt); 670 } 671 #endif 672 673 public: 674 // Copy the current allocation context statistics for the specified contexts. 675 // For each context in contexts, set the corresponding entries in the totals 676 // and accuracy arrays to the current values held by the statistics. Each 677 // array should be of length len. 678 // Returns true if there are more stats available. 679 virtual bool copy_allocation_context_stats(const jint* contexts, 680 jlong* totals, 681 jbyte* accuracy, 682 jint len) { 683 return false; 684 } 685 686 }; 687 688 // Class to set and reset the GC cause for a CollectedHeap. 689 690 class GCCauseSetter : StackObj { 691 CollectedHeap* _heap; 692 GCCause::Cause _previous_cause; 693 public: 694 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) { 695 assert(SafepointSynchronize::is_at_safepoint(), 696 "This method manipulates heap state without locking"); 697 _heap = heap; 698 _previous_cause = _heap->gc_cause(); 699 _heap->set_gc_cause(cause); 700 } 701 702 ~GCCauseSetter() { 703 assert(SafepointSynchronize::is_at_safepoint(), 704 "This method manipulates heap state without locking"); 705 _heap->set_gc_cause(_previous_cause); 706 } 707 }; 708 709 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP