1 #ifdef USE_PRAGMA_IDENT_HDR
2 #pragma ident "@(#)collectedHeap.hpp 1.58 07/09/07 10:56:50 JVM"
3 #endif
4 /*
5 * Copyright 2001-2008 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This
29 // is an abstract class: there may be many different kinds of heaps. This
30 // class defines the functions that a heap must implement, and contains
31 // infrastructure common to all heaps.
32
33 class BarrierSet;
34 class ThreadClosure;
35 class AdaptiveSizePolicy;
36 class Thread;
37
38 //
39 // CollectedHeap
40 // SharedHeap
41 // GenCollectedHeap
42 // G1CollectedHeap
43 // ParallelScavengeHeap
44 //
45 class CollectedHeap : public CHeapObj {
46 friend class VMStructs;
47 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
48
49 #ifdef ASSERT
50 static int _fire_out_of_memory_count;
51 #endif
52
53 // Used for filler objects (static, but initialized in ctor).
54 static size_t _filler_array_max_size;
55
56 protected:
57 MemRegion _reserved;
58 BarrierSet* _barrier_set;
59 bool _is_gc_active;
60 unsigned int _total_collections; // ... started
61 unsigned int _total_full_collections; // ... started
62 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
63 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
64
65 // Reason for current garbage collection. Should be set to
66 // a value reflecting no collection between collections.
67 GCCause::Cause _gc_cause;
68 GCCause::Cause _gc_lastcause;
69 PerfStringVariable* _perf_gc_cause;
70 PerfStringVariable* _perf_gc_lastcause;
71
72 // Constructor
73 CollectedHeap();
74
75 // Create a new tlab
76 virtual HeapWord* allocate_new_tlab(size_t size);
77
78 // Fix up tlabs to make the heap well-formed again,
79 // optionally retiring the tlabs.
80 virtual void fill_all_tlabs(bool retire);
81
82 // Accumulate statistics on all tlabs.
83 virtual void accumulate_statistics_all_tlabs();
84
85 // Reinitialize tlabs before resuming mutators.
86 virtual void resize_all_tlabs();
87
88 debug_only(static void check_for_valid_allocation_state();)
89
90 protected:
91 // Allocate from the current thread's TLAB, with broken-out slow path.
92 inline static HeapWord* allocate_from_tlab(Thread* thread, size_t size);
93 static HeapWord* allocate_from_tlab_slow(Thread* thread, size_t size);
94
95 // Allocate an uninitialized block of the given size, or returns NULL if
96 // this is impossible.
97 inline static HeapWord* common_mem_allocate_noinit(size_t size, bool is_noref, TRAPS);
98
99 // Like allocate_init, but the block returned by a successful allocation
100 // is guaranteed initialized to zeros.
101 inline static HeapWord* common_mem_allocate_init(size_t size, bool is_noref, TRAPS);
102
103 // Same as common_mem version, except memory is allocated in the permanent area
104 // If there is no permanent area, revert to common_mem_allocate_noinit
105 inline static HeapWord* common_permanent_mem_allocate_noinit(size_t size, TRAPS);
106
107 // Same as common_mem version, except memory is allocated in the permanent area
108 // If there is no permanent area, revert to common_mem_allocate_init
109 inline static HeapWord* common_permanent_mem_allocate_init(size_t size, TRAPS);
110
111 // Helper functions for (VM) allocation.
112 inline static void post_allocation_setup_common(KlassHandle klass,
113 HeapWord* obj, size_t size);
114 inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
115 HeapWord* objPtr,
116 size_t size);
117
118 inline static void post_allocation_setup_obj(KlassHandle klass,
119 HeapWord* obj, size_t size);
120
121 inline static void post_allocation_setup_array(KlassHandle klass,
122 HeapWord* obj, size_t size,
123 int length);
124
125 // Clears an allocated object.
126 inline static void init_obj(HeapWord* obj, size_t size);
127
128 // Filler object utilities.
129 static inline size_t filler_array_hdr_size();
130 static inline size_t filler_array_min_size();
131 static inline size_t filler_array_max_size();
132
133 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
134 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words);)
135
136 // Fill with a single array; caller must ensure filler_array_min_size() <=
137 // words <= filler_array_max_size().
138 static inline void fill_with_array(HeapWord* start, size_t words);
139
140 // Fill with a single object (either an int array or a java.lang.Object).
141 static inline void fill_with_object_impl(HeapWord* start, size_t words);
142
143 // Verification functions
144 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
145 PRODUCT_RETURN;
146 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
147 PRODUCT_RETURN;
148
149 public:
150 enum Name {
151 Abstract,
152 SharedHeap,
153 GenCollectedHeap,
154 ParallelScavengeHeap,
155 G1CollectedHeap
156 };
157
158 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
159
160 /**
161 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
162 * and JNI_OK on success.
163 */
164 virtual jint initialize() = 0;
165
166 // In many heaps, there will be a need to perform some initialization activities
167 // after the Universe is fully formed, but before general heap allocation is allowed.
168 // This is the correct place to place such initialization methods.
169 virtual void post_initialize() = 0;
170
171 MemRegion reserved_region() const { return _reserved; }
172 address base() const { return (address)reserved_region().start(); }
173
174 // Future cleanup here. The following functions should specify bytes or
175 // heapwords as part of their signature.
176 virtual size_t capacity() const = 0;
177 virtual size_t used() const = 0;
178
179 // Return "true" if the part of the heap that allocates Java
180 // objects has reached the maximal committed limit that it can
181 // reach, without a garbage collection.
182 virtual bool is_maximal_no_gc() const = 0;
183
184 virtual size_t permanent_capacity() const = 0;
185 virtual size_t permanent_used() const = 0;
186
187 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
188 // memory that the vm could make available for storing 'normal' java objects.
189 // This is based on the reserved address space, but should not include space
190 // that the vm uses internally for bookkeeping or temporary storage (e.g.,
191 // perm gen space or, in the case of the young gen, one of the survivor
192 // spaces).
193 virtual size_t max_capacity() const = 0;
194
195 // Returns "TRUE" if "p" points into the reserved area of the heap.
196 bool is_in_reserved(const void* p) const {
197 return _reserved.contains(p);
198 }
199
200 bool is_in_reserved_or_null(const void* p) const {
201 return p == NULL || is_in_reserved(p);
202 }
203
204 // Returns "TRUE" if "p" points to the head of an allocated object in the
205 // heap. Since this method can be expensive in general, we restrict its
206 // use to assertion checking only.
207 virtual bool is_in(const void* p) const = 0;
208
209 bool is_in_or_null(const void* p) const {
210 return p == NULL || is_in(p);
211 }
212
213 // Let's define some terms: a "closed" subset of a heap is one that
214 //
215 // 1) contains all currently-allocated objects, and
216 //
217 // 2) is closed under reference: no object in the closed subset
218 // references one outside the closed subset.
219 //
220 // Membership in a heap's closed subset is useful for assertions.
221 // Clearly, the entire heap is a closed subset, so the default
222 // implementation is to use "is_in_reserved". But this may not be too
223 // liberal to perform useful checking. Also, the "is_in" predicate
224 // defines a closed subset, but may be too expensive, since "is_in"
225 // verifies that its argument points to an object head. The
226 // "closed_subset" method allows a heap to define an intermediate
227 // predicate, allowing more precise checking than "is_in_reserved" at
228 // lower cost than "is_in."
229
230 // One important case is a heap composed of disjoint contiguous spaces,
231 // such as the Garbage-First collector. Such heaps have a convenient
232 // closed subset consisting of the allocated portions of those
233 // contiguous spaces.
234
235 // Return "TRUE" iff the given pointer points into the heap's defined
236 // closed subset (which defaults to the entire heap).
237 virtual bool is_in_closed_subset(const void* p) const {
238 return is_in_reserved(p);
239 }
240
241 bool is_in_closed_subset_or_null(const void* p) const {
242 return p == NULL || is_in_closed_subset(p);
243 }
244
245 // Returns "TRUE" if "p" is allocated as "permanent" data.
246 // If the heap does not use "permanent" data, returns the same
247 // value is_in_reserved() would return.
248 // NOTE: this actually returns true if "p" is in reserved space
249 // for the space not that it is actually allocated (i.e. in committed
250 // space). If you need the more conservative answer use is_permanent().
251 virtual bool is_in_permanent(const void *p) const = 0;
252
253 // Returns "TRUE" if "p" is in the committed area of "permanent" data.
254 // If the heap does not use "permanent" data, returns the same
255 // value is_in() would return.
256 virtual bool is_permanent(const void *p) const = 0;
257
258 bool is_in_permanent_or_null(const void *p) const {
259 return p == NULL || is_in_permanent(p);
260 }
261
262 // Returns "TRUE" if "p" is a method oop in the
263 // current heap, with high probability. This predicate
264 // is not stable, in general.
265 bool is_valid_method(oop p) const;
266
267 void set_gc_cause(GCCause::Cause v) {
268 if (UsePerfData) {
269 _gc_lastcause = _gc_cause;
270 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
271 _perf_gc_cause->set_value(GCCause::to_string(v));
272 }
273 _gc_cause = v;
274 }
275 GCCause::Cause gc_cause() { return _gc_cause; }
276
277 // Preload classes into the shared portion of the heap, and then dump
278 // that data to a file so that it can be loaded directly by another
279 // VM (then terminate).
280 virtual void preload_and_dump(TRAPS) { ShouldNotReachHere(); }
281
282 // General obj/array allocation facilities.
283 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
284 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
285 inline static oop large_typearray_allocate(KlassHandle klass, int size, int length, TRAPS);
286
287 // Special obj/array allocation facilities.
288 // Some heaps may want to manage "permanent" data uniquely. These default
289 // to the general routines if the heap does not support such handling.
290 inline static oop permanent_obj_allocate(KlassHandle klass, int size, TRAPS);
291 // permanent_obj_allocate_no_klass_install() does not do the installation of
292 // the klass pointer in the newly created object (as permanent_obj_allocate()
293 // above does). This allows for a delay in the installation of the klass
294 // pointer that is needed during the create of klassKlass's. The
295 // method post_allocation_install_obj_klass() is used to install the
296 // klass pointer.
297 inline static oop permanent_obj_allocate_no_klass_install(KlassHandle klass,
298 int size,
299 TRAPS);
300 inline static void post_allocation_install_obj_klass(KlassHandle klass,
301 oop obj,
302 int size);
303 inline static oop permanent_array_allocate(KlassHandle klass, int size, int length, TRAPS);
304
305 // Raw memory allocation facilities
306 // The obj and array allocate methods are covers for these methods.
307 // The permanent allocation method should default to mem_allocate if
308 // permanent memory isn't supported.
309 virtual HeapWord* mem_allocate(size_t size,
310 bool is_noref,
311 bool is_tlab,
312 bool* gc_overhead_limit_was_exceeded) = 0;
313 virtual HeapWord* permanent_mem_allocate(size_t size) = 0;
314
315 // The boundary between a "large" and "small" array of primitives, in words.
316 virtual size_t large_typearray_limit() = 0;
317
318 // Utilities for turning raw memory into filler objects.
319 //
320 // min_fill_size() is the smallest region that can be filled.
321 // fill_with_objects() can fill arbitrary-sized regions of the heap using
322 // multiple objects. fill_with_object() is for regions known to be smaller
323 // than the largest array of integers; it uses a single object to fill the
324 // region and has slightly less overhead.
325 static size_t min_fill_size() {
326 return size_t(align_object_size(oopDesc::header_size()));
327 }
328
329 static void fill_with_objects(HeapWord* start, size_t words);
330
331 static void fill_with_object(HeapWord* start, size_t words);
332 static void fill_with_object(MemRegion region) {
333 fill_with_object(region.start(), region.word_size());
334 }
335 static void fill_with_object(HeapWord* start, HeapWord* end) {
336 fill_with_object(start, pointer_delta(end, start));
337 }
338
339 // Some heaps may offer a contiguous region for shared non-blocking
340 // allocation, via inlined code (by exporting the address of the top and
341 // end fields defining the extent of the contiguous allocation region.)
342
343 // This function returns "true" iff the heap supports this kind of
344 // allocation. (Default is "no".)
345 virtual bool supports_inline_contig_alloc() const {
346 return false;
347 }
348 // These functions return the addresses of the fields that define the
349 // boundaries of the contiguous allocation area. (These fields should be
350 // physically near to one another.)
351 virtual HeapWord** top_addr() const {
352 guarantee(false, "inline contiguous allocation not supported");
353 return NULL;
354 }
355 virtual HeapWord** end_addr() const {
356 guarantee(false, "inline contiguous allocation not supported");
357 return NULL;
358 }
359
360 // Some heaps may be in an unparseable state at certain times between
361 // collections. This may be necessary for efficient implementation of
362 // certain allocation-related activities. Calling this function before
363 // attempting to parse a heap ensures that the heap is in a parsable
364 // state (provided other concurrent activity does not introduce
365 // unparsability). It is normally expected, therefore, that this
366 // method is invoked with the world stopped.
367 // NOTE: if you override this method, make sure you call
368 // super::ensure_parsability so that the non-generational
369 // part of the work gets done. See implementation of
370 // CollectedHeap::ensure_parsability and, for instance,
371 // that of GenCollectedHeap::ensure_parsability().
372 // The argument "retire_tlabs" controls whether existing TLABs
373 // are merely filled or also retired, thus preventing further
374 // allocation from them and necessitating allocation of new TLABs.
375 virtual void ensure_parsability(bool retire_tlabs);
376
377 // Return an estimate of the maximum allocation that could be performed
378 // without triggering any collection or expansion activity. In a
379 // generational collector, for example, this is probably the largest
380 // allocation that could be supported (without expansion) in the youngest
381 // generation. It is "unsafe" because no locks are taken; the result
382 // should be treated as an approximation, not a guarantee, for use in
383 // heuristic resizing decisions.
384 virtual size_t unsafe_max_alloc() = 0;
385
386 // Section on thread-local allocation buffers (TLABs)
387 // If the heap supports thread-local allocation buffers, it should override
388 // the following methods:
389 // Returns "true" iff the heap supports thread-local allocation buffers.
390 // The default is "no".
391 virtual bool supports_tlab_allocation() const {
392 return false;
393 }
394 // The amount of space available for thread-local allocation buffers.
395 virtual size_t tlab_capacity(Thread *thr) const {
396 guarantee(false, "thread-local allocation buffers not supported");
397 return 0;
398 }
399 // An estimate of the maximum allocation that could be performed
400 // for thread-local allocation buffers without triggering any
401 // collection or expansion activity.
402 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
403 guarantee(false, "thread-local allocation buffers not supported");
404 return 0;
405 }
406 // Can a compiler initialize a new object without store barriers?
407 // This permission only extends from the creation of a new object
408 // via a TLAB up to the first subsequent safepoint.
409 virtual bool can_elide_tlab_store_barriers() const = 0;
410
411 // If a compiler is eliding store barriers for TLAB-allocated objects,
412 // there is probably a corresponding slow path which can produce
413 // an object allocated anywhere. The compiler's runtime support
414 // promises to call this function on such a slow-path-allocated
415 // object before performing initializations that have elided
416 // store barriers. Returns new_obj, or maybe a safer copy thereof.
417 virtual oop new_store_barrier(oop new_obj);
418
419 // Can a compiler elide a store barrier when it writes
420 // a permanent oop into the heap? Applies when the compiler
421 // is storing x to the heap, where x->is_perm() is true.
422 virtual bool can_elide_permanent_oop_store_barriers() const = 0;
423
424 // Does this heap support heap inspection (+PrintClassHistogram?)
425 virtual bool supports_heap_inspection() const = 0;
426
427 // Perform a collection of the heap; intended for use in implementing
428 // "System.gc". This probably implies as full a collection as the
429 // "CollectedHeap" supports.
430 virtual void collect(GCCause::Cause cause) = 0;
431
432 // This interface assumes that it's being called by the
433 // vm thread. It collects the heap assuming that the
434 // heap lock is already held and that we are executing in
435 // the context of the vm thread.
436 virtual void collect_as_vm_thread(GCCause::Cause cause) = 0;
437
438 // Returns the barrier set for this heap
439 BarrierSet* barrier_set() { return _barrier_set; }
440
441 // Returns "true" iff there is a stop-world GC in progress. (I assume
442 // that it should answer "false" for the concurrent part of a concurrent
443 // collector -- dld).
444 bool is_gc_active() const { return _is_gc_active; }
445
446 // Total number of GC collections (started)
447 unsigned int total_collections() const { return _total_collections; }
448 unsigned int total_full_collections() const { return _total_full_collections;}
449
450 // Increment total number of GC collections (started)
451 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
452 void increment_total_collections(bool full = false) {
453 _total_collections++;
454 if (full) {
455 increment_total_full_collections();
456 }
457 }
458
459 void increment_total_full_collections() { _total_full_collections++; }
460
461 // Return the AdaptiveSizePolicy for the heap.
462 virtual AdaptiveSizePolicy* size_policy() = 0;
463
464 // Iterate over all the ref-containing fields of all objects, calling
465 // "cl.do_oop" on each. This includes objects in permanent memory.
466 virtual void oop_iterate(OopClosure* cl) = 0;
467
468 // Iterate over all objects, calling "cl.do_object" on each.
469 // This includes objects in permanent memory.
470 virtual void object_iterate(ObjectClosure* cl) = 0;
471
472 // Behaves the same as oop_iterate, except only traverses
473 // interior pointers contained in permanent memory. If there
474 // is no permanent memory, does nothing.
475 virtual void permanent_oop_iterate(OopClosure* cl) = 0;
476
477 // Behaves the same as object_iterate, except only traverses
478 // object contained in permanent memory. If there is no
479 // permanent memory, does nothing.
480 virtual void permanent_object_iterate(ObjectClosure* cl) = 0;
481
482 // NOTE! There is no requirement that a collector implement these
483 // functions.
484 //
485 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
486 // each address in the (reserved) heap is a member of exactly
487 // one block. The defining characteristic of a block is that it is
488 // possible to find its size, and thus to progress forward to the next
489 // block. (Blocks may be of different sizes.) Thus, blocks may
490 // represent Java objects, or they might be free blocks in a
491 // free-list-based heap (or subheap), as long as the two kinds are
492 // distinguishable and the size of each is determinable.
493
494 // Returns the address of the start of the "block" that contains the
495 // address "addr". We say "blocks" instead of "object" since some heaps
496 // may not pack objects densely; a chunk may either be an object or a
497 // non-object.
498 virtual HeapWord* block_start(const void* addr) const = 0;
499
500 // Requires "addr" to be the start of a chunk, and returns its size.
501 // "addr + size" is required to be the start of a new chunk, or the end
502 // of the active area of the heap.
503 virtual size_t block_size(const HeapWord* addr) const = 0;
504
505 // Requires "addr" to be the start of a block, and returns "TRUE" iff
506 // the block is an object.
507 virtual bool block_is_obj(const HeapWord* addr) const = 0;
508
509 // Returns the longest time (in ms) that has elapsed since the last
510 // time that any part of the heap was examined by a garbage collection.
511 virtual jlong millis_since_last_gc() = 0;
512
513 // Perform any cleanup actions necessary before allowing a verification.
514 virtual void prepare_for_verify() = 0;
515
516 virtual void print() const = 0;
517 virtual void print_on(outputStream* st) const = 0;
518
519 // Print all GC threads (other than the VM thread)
520 // used by this heap.
521 virtual void print_gc_threads_on(outputStream* st) const = 0;
522 void print_gc_threads() { print_gc_threads_on(tty); }
523 // Iterator for all GC threads (other than VM thread)
524 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
525
526 // Print any relevant tracing info that flags imply.
527 // Default implementation does nothing.
528 virtual void print_tracing_info() const = 0;
529
530 // Heap verification
531 virtual void verify(bool allow_dirty, bool silent) = 0;
532
533 // Non product verification and debugging.
534 #ifndef PRODUCT
535 // Support for PromotionFailureALot. Return true if it's time to cause a
536 // promotion failure. The no-argument version uses
537 // this->_promotion_failure_alot_count as the counter.
538 inline bool promotion_should_fail(volatile size_t* count);
539 inline bool promotion_should_fail();
540
541 // Reset the PromotionFailureALot counters. Should be called at the end of a
542 // GC in which promotion failure ocurred.
543 inline void reset_promotion_should_fail(volatile size_t* count);
544 inline void reset_promotion_should_fail();
545 #endif // #ifndef PRODUCT
546
547 #ifdef ASSERT
548 static int fired_fake_oom() {
549 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
550 }
551 #endif
552 };
553
554 // Class to set and reset the GC cause for a CollectedHeap.
555
556 class GCCauseSetter : StackObj {
557 CollectedHeap* _heap;
558 GCCause::Cause _previous_cause;
559 public:
560 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
561 assert(SafepointSynchronize::is_at_safepoint(),
562 "This method manipulates heap state without locking");
563 _heap = heap;
564 _previous_cause = _heap->gc_cause();
565 _heap->set_gc_cause(cause);
566 }
567
568 ~GCCauseSetter() {
569 assert(SafepointSynchronize::is_at_safepoint(),
570 "This method manipulates heap state without locking");
571 _heap->set_gc_cause(_previous_cause);
572 }
573 };