Thu, 05 Jun 2008 15:57:56 -0700
6711316: Open source the Garbage-First garbage collector
Summary: First mercurial integration of the code for the Garbage-First garbage collector.
Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr
1 /*
2 * Copyright 2001-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This
26 // is an abstract class: there may be many different kinds of heaps. This
27 // class defines the functions that a heap must implement, and contains
28 // infrastructure common to all heaps.
30 class BarrierSet;
31 class ThreadClosure;
32 class AdaptiveSizePolicy;
33 class Thread;
35 //
36 // CollectedHeap
37 // SharedHeap
38 // GenCollectedHeap
39 // G1CollectedHeap
40 // ParallelScavengeHeap
41 //
42 class CollectedHeap : public CHeapObj {
43 friend class VMStructs;
44 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
46 #ifdef ASSERT
47 static int _fire_out_of_memory_count;
48 #endif
50 protected:
51 MemRegion _reserved;
52 BarrierSet* _barrier_set;
53 bool _is_gc_active;
54 unsigned int _total_collections; // ... started
55 unsigned int _total_full_collections; // ... started
56 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
57 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
59 // Reason for current garbage collection. Should be set to
60 // a value reflecting no collection between collections.
61 GCCause::Cause _gc_cause;
62 GCCause::Cause _gc_lastcause;
63 PerfStringVariable* _perf_gc_cause;
64 PerfStringVariable* _perf_gc_lastcause;
66 // Constructor
67 CollectedHeap();
69 // Create a new tlab
70 virtual HeapWord* allocate_new_tlab(size_t size);
72 // Fix up tlabs to make the heap well-formed again,
73 // optionally retiring the tlabs.
74 virtual void fill_all_tlabs(bool retire);
76 // Accumulate statistics on all tlabs.
77 virtual void accumulate_statistics_all_tlabs();
79 // Reinitialize tlabs before resuming mutators.
80 virtual void resize_all_tlabs();
82 debug_only(static void check_for_valid_allocation_state();)
84 protected:
85 // Allocate from the current thread's TLAB, with broken-out slow path.
86 inline static HeapWord* allocate_from_tlab(Thread* thread, size_t size);
87 static HeapWord* allocate_from_tlab_slow(Thread* thread, size_t size);
89 // Allocate an uninitialized block of the given size, or returns NULL if
90 // this is impossible.
91 inline static HeapWord* common_mem_allocate_noinit(size_t size, bool is_noref, TRAPS);
93 // Like allocate_init, but the block returned by a successful allocation
94 // is guaranteed initialized to zeros.
95 inline static HeapWord* common_mem_allocate_init(size_t size, bool is_noref, TRAPS);
97 // Same as common_mem version, except memory is allocated in the permanent area
98 // If there is no permanent area, revert to common_mem_allocate_noinit
99 inline static HeapWord* common_permanent_mem_allocate_noinit(size_t size, TRAPS);
101 // Same as common_mem version, except memory is allocated in the permanent area
102 // If there is no permanent area, revert to common_mem_allocate_init
103 inline static HeapWord* common_permanent_mem_allocate_init(size_t size, TRAPS);
105 // Helper functions for (VM) allocation.
106 inline static void post_allocation_setup_common(KlassHandle klass,
107 HeapWord* obj, size_t size);
108 inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
109 HeapWord* objPtr,
110 size_t size);
112 inline static void post_allocation_setup_obj(KlassHandle klass,
113 HeapWord* obj, size_t size);
115 inline static void post_allocation_setup_array(KlassHandle klass,
116 HeapWord* obj, size_t size,
117 int length);
119 // Clears an allocated object.
120 inline static void init_obj(HeapWord* obj, size_t size);
122 // Verification functions
123 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
124 PRODUCT_RETURN;
125 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
126 PRODUCT_RETURN;
128 public:
129 enum Name {
130 Abstract,
131 SharedHeap,
132 GenCollectedHeap,
133 ParallelScavengeHeap,
134 G1CollectedHeap
135 };
137 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
139 /**
140 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
141 * and JNI_OK on success.
142 */
143 virtual jint initialize() = 0;
145 // In many heaps, there will be a need to perform some initialization activities
146 // after the Universe is fully formed, but before general heap allocation is allowed.
147 // This is the correct place to place such initialization methods.
148 virtual void post_initialize() = 0;
150 MemRegion reserved_region() const { return _reserved; }
151 address base() const { return (address)reserved_region().start(); }
153 // Future cleanup here. The following functions should specify bytes or
154 // heapwords as part of their signature.
155 virtual size_t capacity() const = 0;
156 virtual size_t used() const = 0;
158 // Return "true" if the part of the heap that allocates Java
159 // objects has reached the maximal committed limit that it can
160 // reach, without a garbage collection.
161 virtual bool is_maximal_no_gc() const = 0;
163 virtual size_t permanent_capacity() const = 0;
164 virtual size_t permanent_used() const = 0;
166 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
167 // memory that the vm could make available for storing 'normal' java objects.
168 // This is based on the reserved address space, but should not include space
169 // that the vm uses internally for bookkeeping or temporary storage (e.g.,
170 // perm gen space or, in the case of the young gen, one of the survivor
171 // spaces).
172 virtual size_t max_capacity() const = 0;
174 // Returns "TRUE" if "p" points into the reserved area of the heap.
175 bool is_in_reserved(const void* p) const {
176 return _reserved.contains(p);
177 }
179 bool is_in_reserved_or_null(const void* p) const {
180 return p == NULL || is_in_reserved(p);
181 }
183 // Returns "TRUE" if "p" points to the head of an allocated object in the
184 // heap. Since this method can be expensive in general, we restrict its
185 // use to assertion checking only.
186 virtual bool is_in(const void* p) const = 0;
188 bool is_in_or_null(const void* p) const {
189 return p == NULL || is_in(p);
190 }
192 // Let's define some terms: a "closed" subset of a heap is one that
193 //
194 // 1) contains all currently-allocated objects, and
195 //
196 // 2) is closed under reference: no object in the closed subset
197 // references one outside the closed subset.
198 //
199 // Membership in a heap's closed subset is useful for assertions.
200 // Clearly, the entire heap is a closed subset, so the default
201 // implementation is to use "is_in_reserved". But this may not be too
202 // liberal to perform useful checking. Also, the "is_in" predicate
203 // defines a closed subset, but may be too expensive, since "is_in"
204 // verifies that its argument points to an object head. The
205 // "closed_subset" method allows a heap to define an intermediate
206 // predicate, allowing more precise checking than "is_in_reserved" at
207 // lower cost than "is_in."
209 // One important case is a heap composed of disjoint contiguous spaces,
210 // such as the Garbage-First collector. Such heaps have a convenient
211 // closed subset consisting of the allocated portions of those
212 // contiguous spaces.
214 // Return "TRUE" iff the given pointer points into the heap's defined
215 // closed subset (which defaults to the entire heap).
216 virtual bool is_in_closed_subset(const void* p) const {
217 return is_in_reserved(p);
218 }
220 bool is_in_closed_subset_or_null(const void* p) const {
221 return p == NULL || is_in_closed_subset(p);
222 }
224 // Returns "TRUE" if "p" is allocated as "permanent" data.
225 // If the heap does not use "permanent" data, returns the same
226 // value is_in_reserved() would return.
227 // NOTE: this actually returns true if "p" is in reserved space
228 // for the space not that it is actually allocated (i.e. in committed
229 // space). If you need the more conservative answer use is_permanent().
230 virtual bool is_in_permanent(const void *p) const = 0;
232 // Returns "TRUE" if "p" is in the committed area of "permanent" data.
233 // If the heap does not use "permanent" data, returns the same
234 // value is_in() would return.
235 virtual bool is_permanent(const void *p) const = 0;
237 bool is_in_permanent_or_null(const void *p) const {
238 return p == NULL || is_in_permanent(p);
239 }
241 // Returns "TRUE" if "p" is a method oop in the
242 // current heap, with high probability. This predicate
243 // is not stable, in general.
244 bool is_valid_method(oop p) const;
246 void set_gc_cause(GCCause::Cause v) {
247 if (UsePerfData) {
248 _gc_lastcause = _gc_cause;
249 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
250 _perf_gc_cause->set_value(GCCause::to_string(v));
251 }
252 _gc_cause = v;
253 }
254 GCCause::Cause gc_cause() { return _gc_cause; }
256 // Preload classes into the shared portion of the heap, and then dump
257 // that data to a file so that it can be loaded directly by another
258 // VM (then terminate).
259 virtual void preload_and_dump(TRAPS) { ShouldNotReachHere(); }
261 // General obj/array allocation facilities.
262 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
263 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
264 inline static oop large_typearray_allocate(KlassHandle klass, int size, int length, TRAPS);
266 // Special obj/array allocation facilities.
267 // Some heaps may want to manage "permanent" data uniquely. These default
268 // to the general routines if the heap does not support such handling.
269 inline static oop permanent_obj_allocate(KlassHandle klass, int size, TRAPS);
270 // permanent_obj_allocate_no_klass_install() does not do the installation of
271 // the klass pointer in the newly created object (as permanent_obj_allocate()
272 // above does). This allows for a delay in the installation of the klass
273 // pointer that is needed during the create of klassKlass's. The
274 // method post_allocation_install_obj_klass() is used to install the
275 // klass pointer.
276 inline static oop permanent_obj_allocate_no_klass_install(KlassHandle klass,
277 int size,
278 TRAPS);
279 inline static void post_allocation_install_obj_klass(KlassHandle klass,
280 oop obj,
281 int size);
282 inline static oop permanent_array_allocate(KlassHandle klass, int size, int length, TRAPS);
284 // Raw memory allocation facilities
285 // The obj and array allocate methods are covers for these methods.
286 // The permanent allocation method should default to mem_allocate if
287 // permanent memory isn't supported.
288 virtual HeapWord* mem_allocate(size_t size,
289 bool is_noref,
290 bool is_tlab,
291 bool* gc_overhead_limit_was_exceeded) = 0;
292 virtual HeapWord* permanent_mem_allocate(size_t size) = 0;
294 // The boundary between a "large" and "small" array of primitives, in words.
295 virtual size_t large_typearray_limit() = 0;
297 // Some heaps may offer a contiguous region for shared non-blocking
298 // allocation, via inlined code (by exporting the address of the top and
299 // end fields defining the extent of the contiguous allocation region.)
301 // This function returns "true" iff the heap supports this kind of
302 // allocation. (Default is "no".)
303 virtual bool supports_inline_contig_alloc() const {
304 return false;
305 }
306 // These functions return the addresses of the fields that define the
307 // boundaries of the contiguous allocation area. (These fields should be
308 // physically near to one another.)
309 virtual HeapWord** top_addr() const {
310 guarantee(false, "inline contiguous allocation not supported");
311 return NULL;
312 }
313 virtual HeapWord** end_addr() const {
314 guarantee(false, "inline contiguous allocation not supported");
315 return NULL;
316 }
318 // Some heaps may be in an unparseable state at certain times between
319 // collections. This may be necessary for efficient implementation of
320 // certain allocation-related activities. Calling this function before
321 // attempting to parse a heap ensures that the heap is in a parsable
322 // state (provided other concurrent activity does not introduce
323 // unparsability). It is normally expected, therefore, that this
324 // method is invoked with the world stopped.
325 // NOTE: if you override this method, make sure you call
326 // super::ensure_parsability so that the non-generational
327 // part of the work gets done. See implementation of
328 // CollectedHeap::ensure_parsability and, for instance,
329 // that of GenCollectedHeap::ensure_parsability().
330 // The argument "retire_tlabs" controls whether existing TLABs
331 // are merely filled or also retired, thus preventing further
332 // allocation from them and necessitating allocation of new TLABs.
333 virtual void ensure_parsability(bool retire_tlabs);
335 // Return an estimate of the maximum allocation that could be performed
336 // without triggering any collection or expansion activity. In a
337 // generational collector, for example, this is probably the largest
338 // allocation that could be supported (without expansion) in the youngest
339 // generation. It is "unsafe" because no locks are taken; the result
340 // should be treated as an approximation, not a guarantee, for use in
341 // heuristic resizing decisions.
342 virtual size_t unsafe_max_alloc() = 0;
344 // Section on thread-local allocation buffers (TLABs)
345 // If the heap supports thread-local allocation buffers, it should override
346 // the following methods:
347 // Returns "true" iff the heap supports thread-local allocation buffers.
348 // The default is "no".
349 virtual bool supports_tlab_allocation() const {
350 return false;
351 }
352 // The amount of space available for thread-local allocation buffers.
353 virtual size_t tlab_capacity(Thread *thr) const {
354 guarantee(false, "thread-local allocation buffers not supported");
355 return 0;
356 }
357 // An estimate of the maximum allocation that could be performed
358 // for thread-local allocation buffers without triggering any
359 // collection or expansion activity.
360 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
361 guarantee(false, "thread-local allocation buffers not supported");
362 return 0;
363 }
364 // Can a compiler initialize a new object without store barriers?
365 // This permission only extends from the creation of a new object
366 // via a TLAB up to the first subsequent safepoint.
367 virtual bool can_elide_tlab_store_barriers() const = 0;
369 // If a compiler is eliding store barriers for TLAB-allocated objects,
370 // there is probably a corresponding slow path which can produce
371 // an object allocated anywhere. The compiler's runtime support
372 // promises to call this function on such a slow-path-allocated
373 // object before performing initializations that have elided
374 // store barriers. Returns new_obj, or maybe a safer copy thereof.
375 virtual oop new_store_barrier(oop new_obj);
377 // Can a compiler elide a store barrier when it writes
378 // a permanent oop into the heap? Applies when the compiler
379 // is storing x to the heap, where x->is_perm() is true.
380 virtual bool can_elide_permanent_oop_store_barriers() const = 0;
382 // Does this heap support heap inspection (+PrintClassHistogram?)
383 virtual bool supports_heap_inspection() const = 0;
385 // Perform a collection of the heap; intended for use in implementing
386 // "System.gc". This probably implies as full a collection as the
387 // "CollectedHeap" supports.
388 virtual void collect(GCCause::Cause cause) = 0;
390 // This interface assumes that it's being called by the
391 // vm thread. It collects the heap assuming that the
392 // heap lock is already held and that we are executing in
393 // the context of the vm thread.
394 virtual void collect_as_vm_thread(GCCause::Cause cause) = 0;
396 // Returns the barrier set for this heap
397 BarrierSet* barrier_set() { return _barrier_set; }
399 // Returns "true" iff there is a stop-world GC in progress. (I assume
400 // that it should answer "false" for the concurrent part of a concurrent
401 // collector -- dld).
402 bool is_gc_active() const { return _is_gc_active; }
404 // Total number of GC collections (started)
405 unsigned int total_collections() const { return _total_collections; }
406 unsigned int total_full_collections() const { return _total_full_collections;}
408 // Increment total number of GC collections (started)
409 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
410 void increment_total_collections(bool full = false) {
411 _total_collections++;
412 if (full) {
413 increment_total_full_collections();
414 }
415 }
417 void increment_total_full_collections() { _total_full_collections++; }
419 // Return the AdaptiveSizePolicy for the heap.
420 virtual AdaptiveSizePolicy* size_policy() = 0;
422 // Iterate over all the ref-containing fields of all objects, calling
423 // "cl.do_oop" on each. This includes objects in permanent memory.
424 virtual void oop_iterate(OopClosure* cl) = 0;
426 // Iterate over all objects, calling "cl.do_object" on each.
427 // This includes objects in permanent memory.
428 virtual void object_iterate(ObjectClosure* cl) = 0;
430 // Behaves the same as oop_iterate, except only traverses
431 // interior pointers contained in permanent memory. If there
432 // is no permanent memory, does nothing.
433 virtual void permanent_oop_iterate(OopClosure* cl) = 0;
435 // Behaves the same as object_iterate, except only traverses
436 // object contained in permanent memory. If there is no
437 // permanent memory, does nothing.
438 virtual void permanent_object_iterate(ObjectClosure* cl) = 0;
440 // NOTE! There is no requirement that a collector implement these
441 // functions.
442 //
443 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
444 // each address in the (reserved) heap is a member of exactly
445 // one block. The defining characteristic of a block is that it is
446 // possible to find its size, and thus to progress forward to the next
447 // block. (Blocks may be of different sizes.) Thus, blocks may
448 // represent Java objects, or they might be free blocks in a
449 // free-list-based heap (or subheap), as long as the two kinds are
450 // distinguishable and the size of each is determinable.
452 // Returns the address of the start of the "block" that contains the
453 // address "addr". We say "blocks" instead of "object" since some heaps
454 // may not pack objects densely; a chunk may either be an object or a
455 // non-object.
456 virtual HeapWord* block_start(const void* addr) const = 0;
458 // Requires "addr" to be the start of a chunk, and returns its size.
459 // "addr + size" is required to be the start of a new chunk, or the end
460 // of the active area of the heap.
461 virtual size_t block_size(const HeapWord* addr) const = 0;
463 // Requires "addr" to be the start of a block, and returns "TRUE" iff
464 // the block is an object.
465 virtual bool block_is_obj(const HeapWord* addr) const = 0;
467 // Returns the longest time (in ms) that has elapsed since the last
468 // time that any part of the heap was examined by a garbage collection.
469 virtual jlong millis_since_last_gc() = 0;
471 // Perform any cleanup actions necessary before allowing a verification.
472 virtual void prepare_for_verify() = 0;
474 virtual void print() const = 0;
475 virtual void print_on(outputStream* st) const = 0;
477 // Print all GC threads (other than the VM thread)
478 // used by this heap.
479 virtual void print_gc_threads_on(outputStream* st) const = 0;
480 void print_gc_threads() { print_gc_threads_on(tty); }
481 // Iterator for all GC threads (other than VM thread)
482 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
484 // Print any relevant tracing info that flags imply.
485 // Default implementation does nothing.
486 virtual void print_tracing_info() const = 0;
488 // Heap verification
489 virtual void verify(bool allow_dirty, bool silent) = 0;
491 // Non product verification and debugging.
492 #ifndef PRODUCT
493 // Support for PromotionFailureALot. Return true if it's time to cause a
494 // promotion failure. The no-argument version uses
495 // this->_promotion_failure_alot_count as the counter.
496 inline bool promotion_should_fail(volatile size_t* count);
497 inline bool promotion_should_fail();
499 // Reset the PromotionFailureALot counters. Should be called at the end of a
500 // GC in which promotion failure ocurred.
501 inline void reset_promotion_should_fail(volatile size_t* count);
502 inline void reset_promotion_should_fail();
503 #endif // #ifndef PRODUCT
505 #ifdef ASSERT
506 static int fired_fake_oom() {
507 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
508 }
509 #endif
510 };
512 // Class to set and reset the GC cause for a CollectedHeap.
514 class GCCauseSetter : StackObj {
515 CollectedHeap* _heap;
516 GCCause::Cause _previous_cause;
517 public:
518 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
519 assert(SafepointSynchronize::is_at_safepoint(),
520 "This method manipulates heap state without locking");
521 _heap = heap;
522 _previous_cause = _heap->gc_cause();
523 _heap->set_gc_cause(cause);
524 }
526 ~GCCauseSetter() {
527 assert(SafepointSynchronize::is_at_safepoint(),
528 "This method manipulates heap state without locking");
529 _heap->set_gc_cause(_previous_cause);
530 }
531 };