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 2001-2007 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 protected:
54 MemRegion _reserved;
55 BarrierSet* _barrier_set;
56 bool _is_gc_active;
57 unsigned int _total_collections; // ... started
58 unsigned int _total_full_collections; // ... started
59 size_t _max_heap_capacity;
60 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
61 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
62
63 // Reason for current garbage collection. Should be set to
64 // a value reflecting no collection between collections.
65 GCCause::Cause _gc_cause;
66 GCCause::Cause _gc_lastcause;
67 PerfStringVariable* _perf_gc_cause;
68 PerfStringVariable* _perf_gc_lastcause;
69
70 // Constructor
71 CollectedHeap();
72
73 // Create a new tlab
74 virtual HeapWord* allocate_new_tlab(size_t size);
75
76 // Fix up tlabs to make the heap well-formed again,
77 // optionally retiring the tlabs.
78 virtual void fill_all_tlabs(bool retire);
79
80 // Accumulate statistics on all tlabs.
81 virtual void accumulate_statistics_all_tlabs();
82
83 // Reinitialize tlabs before resuming mutators.
84 virtual void resize_all_tlabs();
85
86 debug_only(static void check_for_valid_allocation_state();)
87
88 protected:
89 // Allocate from the current thread's TLAB, with broken-out slow path.
90 inline static HeapWord* allocate_from_tlab(Thread* thread, size_t size);
91 static HeapWord* allocate_from_tlab_slow(Thread* thread, size_t size);
92
93 // Allocate an uninitialized block of the given size, or returns NULL if
94 // this is impossible.
95 inline static HeapWord* common_mem_allocate_noinit(size_t size, bool is_noref, TRAPS);
96
97 // Like allocate_init, but the block returned by a successful allocation
98 // is guaranteed initialized to zeros.
99 inline static HeapWord* common_mem_allocate_init(size_t size, bool is_noref, TRAPS);
100
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_noinit
103 inline static HeapWord* common_permanent_mem_allocate_noinit(size_t size, TRAPS);
104
105 // Same as common_mem version, except memory is allocated in the permanent area
106 // If there is no permanent area, revert to common_mem_allocate_init
107 inline static HeapWord* common_permanent_mem_allocate_init(size_t size, TRAPS);
108
109 // Helper functions for (VM) allocation.
110 inline static void post_allocation_setup_common(KlassHandle klass,
111 HeapWord* obj, size_t size);
112 inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
113 HeapWord* objPtr,
114 size_t size);
115
116 inline static void post_allocation_setup_obj(KlassHandle klass,
117 HeapWord* obj, size_t size);
118
119 inline static void post_allocation_setup_array(KlassHandle klass,
120 HeapWord* obj, size_t size,
121 int length);
122
123 // Clears an allocated object.
124 inline static void init_obj(HeapWord* obj, size_t size);
125
126 // Verification functions
127 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
128 PRODUCT_RETURN;
129 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
130 PRODUCT_RETURN;
131
132 public:
133 enum Name {
134 Abstract,
135 SharedHeap,
136 GenCollectedHeap,
137 ParallelScavengeHeap,
138 G1CollectedHeap
139 };
140
141 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
142
143 /**
144 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
145 * and JNI_OK on success.
146 */
147 virtual jint initialize() = 0;
148
149 // In many heaps, there will be a need to perform some initialization activities
150 // after the Universe is fully formed, but before general heap allocation is allowed.
151 // This is the correct place to place such initialization methods.
152 virtual void post_initialize() = 0;
153
154 MemRegion reserved_region() const { return _reserved; }
155
156 // Return the number of bytes currently reserved, committed, and used,
157 // respectively, for holding objects.
158 size_t reserved_obj_bytes() const { return _reserved.byte_size(); }
159
160 // Future cleanup here. The following functions should specify bytes or
161 // heapwords as part of their signature.
162 virtual size_t capacity() const = 0;
163 virtual size_t used() const = 0;
164
165 // Return "true" if the part of the heap that allocates Java
166 // objects has reached the maximal committed limit that it can
167 // reach, without a garbage collection.
168 virtual bool is_maximal_no_gc() const = 0;
169
170 virtual size_t permanent_capacity() const = 0;
171 virtual size_t permanent_used() const = 0;
172
173 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
174 // memory that the vm could make available for storing 'normal' java objects.
175 // This is based on the reserved address space, but should not include space
176 // that the vm uses internally for bookkeeping or temporary storage (e.g.,
177 // perm gen space or, in the case of the young gen, one of the survivor
178 // spaces).
179 virtual size_t max_capacity() const = 0;
180
181 // Returns "TRUE" if "p" points into the reserved area of the heap.
182 bool is_in_reserved(const void* p) const {
183 return _reserved.contains(p);
184 }
185
186 bool is_in_reserved_or_null(const void* p) const {
187 return p == NULL || is_in_reserved(p);
188 }
189
190 // Returns "TRUE" if "p" points to the head of an allocated object in the
191 // heap. Since this method can be expensive in general, we restrict its
192 // use to assertion checking only.
193 virtual bool is_in(const void* p) const = 0;
194
195 bool is_in_or_null(const void* p) const {
196 return p == NULL || is_in(p);
197 }
198
199 // Let's define some terms: a "closed" subset of a heap is one that
200 //
201 // 1) contains all currently-allocated objects, and
202 //
203 // 2) is closed under reference: no object in the closed subset
204 // references one outside the closed subset.
205 //
206 // Membership in a heap's closed subset is useful for assertions.
207 // Clearly, the entire heap is a closed subset, so the default
208 // implementation is to use "is_in_reserved". But this may not be too
209 // liberal to perform useful checking. Also, the "is_in" predicate
210 // defines a closed subset, but may be too expensive, since "is_in"
211 // verifies that its argument points to an object head. The
212 // "closed_subset" method allows a heap to define an intermediate
213 // predicate, allowing more precise checking than "is_in_reserved" at
214 // lower cost than "is_in."
215
216 // One important case is a heap composed of disjoint contiguous spaces,
217 // such as the Garbage-First collector. Such heaps have a convenient
218 // closed subset consisting of the allocated portions of those
219 // contiguous spaces.
220
221 // Return "TRUE" iff the given pointer points into the heap's defined
222 // closed subset (which defaults to the entire heap).
223 virtual bool is_in_closed_subset(const void* p) const {
224 return is_in_reserved(p);
225 }
226
227 bool is_in_closed_subset_or_null(const void* p) const {
228 return p == NULL || is_in_closed_subset(p);
229 }
230
231 // Returns "TRUE" if "p" is allocated as "permanent" data.
232 // If the heap does not use "permanent" data, returns the same
233 // value is_in_reserved() would return.
234 // NOTE: this actually returns true if "p" is in reserved space
235 // for the space not that it is actually allocated (i.e. in committed
236 // space). If you need the more conservative answer use is_permanent().
237 virtual bool is_in_permanent(const void *p) const = 0;
238
239 // Returns "TRUE" if "p" is in the committed area of "permanent" data.
240 // If the heap does not use "permanent" data, returns the same
241 // value is_in() would return.
242 virtual bool is_permanent(const void *p) const = 0;
243
244 bool is_in_permanent_or_null(const void *p) const {
245 return p == NULL || is_in_permanent(p);
246 }
247
248 // Returns "TRUE" if "p" is a method oop in the
249 // current heap, with high probability. This predicate
250 // is not stable, in general.
251 bool is_valid_method(oop p) const;
252
253 void set_gc_cause(GCCause::Cause v) {
254 if (UsePerfData) {
255 _gc_lastcause = _gc_cause;
256 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
257 _perf_gc_cause->set_value(GCCause::to_string(v));
258 }
259 _gc_cause = v;
260 }
261 GCCause::Cause gc_cause() { return _gc_cause; }
262
263 // Preload classes into the shared portion of the heap, and then dump
264 // that data to a file so that it can be loaded directly by another
265 // VM (then terminate).
266 virtual void preload_and_dump(TRAPS) { ShouldNotReachHere(); }
267
268 // General obj/array allocation facilities.
269 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
270 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
271 inline static oop large_typearray_allocate(KlassHandle klass, int size, int length, TRAPS);
272
273 // Special obj/array allocation facilities.
274 // Some heaps may want to manage "permanent" data uniquely. These default
275 // to the general routines if the heap does not support such handling.
276 inline static oop permanent_obj_allocate(KlassHandle klass, int size, TRAPS);
277 // permanent_obj_allocate_no_klass_install() does not do the installation of
278 // the klass pointer in the newly created object (as permanent_obj_allocate()
279 // above does). This allows for a delay in the installation of the klass
280 // pointer that is needed during the create of klassKlass's. The
281 // method post_allocation_install_obj_klass() is used to install the
282 // klass pointer.
283 inline static oop permanent_obj_allocate_no_klass_install(KlassHandle klass,
284 int size,
285 TRAPS);
286 inline static void post_allocation_install_obj_klass(KlassHandle klass,
287 oop obj,
288 int size);
289 inline static oop permanent_array_allocate(KlassHandle klass, int size, int length, TRAPS);
290
291 // Raw memory allocation facilities
292 // The obj and array allocate methods are covers for these methods.
293 // The permanent allocation method should default to mem_allocate if
294 // permanent memory isn't supported.
295 virtual HeapWord* mem_allocate(size_t size,
296 bool is_noref,
297 bool is_tlab,
298 bool* gc_overhead_limit_was_exceeded) = 0;
299 virtual HeapWord* permanent_mem_allocate(size_t size) = 0;
300
301 // The boundary between a "large" and "small" array of primitives, in words.
302 virtual size_t large_typearray_limit() = 0;
303
304 // Some heaps may offer a contiguous region for shared non-blocking
305 // allocation, via inlined code (by exporting the address of the top and
306 // end fields defining the extent of the contiguous allocation region.)
307
308 // This function returns "true" iff the heap supports this kind of
309 // allocation. (Default is "no".)
310 virtual bool supports_inline_contig_alloc() const {
311 return false;
312 }
313 // These functions return the addresses of the fields that define the
314 // boundaries of the contiguous allocation area. (These fields should be
315 // physically near to one another.)
316 virtual HeapWord** top_addr() const {
317 guarantee(false, "inline contiguous allocation not supported");
318 return NULL;
319 }
320 virtual HeapWord** end_addr() const {
321 guarantee(false, "inline contiguous allocation not supported");
322 return NULL;
323 }
324
325 // Some heaps may be in an unparseable state at certain times between
326 // collections. This may be necessary for efficient implementation of
327 // certain allocation-related activities. Calling this function before
328 // attempting to parse a heap ensures that the heap is in a parsable
329 // state (provided other concurrent activity does not introduce
330 // unparsability). It is normally expected, therefore, that this
331 // method is invoked with the world stopped.
332 // NOTE: if you override this method, make sure you call
333 // super::ensure_parsability so that the non-generational
334 // part of the work gets done. See implementation of
335 // CollectedHeap::ensure_parsability and, for instance,
336 // that of GenCollectedHeap::ensure_parsability().
337 // The argument "retire_tlabs" controls whether existing TLABs
338 // are merely filled or also retired, thus preventing further
339 // allocation from them and necessitating allocation of new TLABs.
340 virtual void ensure_parsability(bool retire_tlabs);
341
342 // Return an estimate of the maximum allocation that could be performed
343 // without triggering any collection or expansion activity. In a
344 // generational collector, for example, this is probably the largest
345 // allocation that could be supported (without expansion) in the youngest
346 // generation. It is "unsafe" because no locks are taken; the result
347 // should be treated as an approximation, not a guarantee, for use in
348 // heuristic resizing decisions.
349 virtual size_t unsafe_max_alloc() = 0;
350
351 // Section on thread-local allocation buffers (TLABs)
352 // If the heap supports thread-local allocation buffers, it should override
353 // the following methods:
354 // Returns "true" iff the heap supports thread-local allocation buffers.
355 // The default is "no".
356 virtual bool supports_tlab_allocation() const {
357 return false;
358 }
359 // The amount of space available for thread-local allocation buffers.
360 virtual size_t tlab_capacity(Thread *thr) const {
361 guarantee(false, "thread-local allocation buffers not supported");
362 return 0;
363 }
364 // An estimate of the maximum allocation that could be performed
365 // for thread-local allocation buffers without triggering any
366 // collection or expansion activity.
367 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
368 guarantee(false, "thread-local allocation buffers not supported");
369 return 0;
370 }
371 // Can a compiler initialize a new object without store barriers?
372 // This permission only extends from the creation of a new object
373 // via a TLAB up to the first subsequent safepoint.
374 virtual bool can_elide_tlab_store_barriers() const {
375 guarantee(kind() < CollectedHeap::G1CollectedHeap, "else change or refactor this");
376 return true;
377 }
378 // If a compiler is eliding store barriers for TLAB-allocated objects,
379 // there is probably a corresponding slow path which can produce
380 // an object allocated anywhere. The compiler's runtime support
381 // promises to call this function on such a slow-path-allocated
382 // object before performing initializations that have elided
383 // store barriers. Returns new_obj, or maybe a safer copy thereof.
384 virtual oop new_store_barrier(oop new_obj);
385
386 // Can a compiler elide a store barrier when it writes
387 // a permanent oop into the heap? Applies when the compiler
388 // is storing x to the heap, where x->is_perm() is true.
389 virtual bool can_elide_permanent_oop_store_barriers() const;
390
391 // Does this heap support heap inspection (+PrintClassHistogram?)
392 virtual bool supports_heap_inspection() const {
393 return false; // Until RFE 5023697 is implemented
394 }
395
396 // Perform a collection of the heap; intended for use in implementing
397 // "System.gc". This probably implies as full a collection as the
398 // "CollectedHeap" supports.
399 virtual void collect(GCCause::Cause cause) = 0;
400
401 // This interface assumes that it's being called by the
402 // vm thread. It collects the heap assuming that the
403 // heap lock is already held and that we are executing in
404 // the context of the vm thread.
405 virtual void collect_as_vm_thread(GCCause::Cause cause) = 0;
406
407 // Returns the barrier set for this heap
408 BarrierSet* barrier_set() { return _barrier_set; }
409
410 // Returns "true" iff there is a stop-world GC in progress. (I assume
411 // that it should answer "false" for the concurrent part of a concurrent
412 // collector -- dld).
413 bool is_gc_active() const { return _is_gc_active; }
414
415 // Total number of GC collections (started)
416 unsigned int total_collections() const { return _total_collections; }
417 unsigned int total_full_collections() const { return _total_full_collections;}
418
419 // Increment total number of GC collections (started)
420 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
421 void increment_total_collections(bool full = false) {
422 _total_collections++;
423 if (full) {
424 increment_total_full_collections();
425 }
426 }
427
428 void increment_total_full_collections() { _total_full_collections++; }
429
430 // Return the AdaptiveSizePolicy for the heap.
431 virtual AdaptiveSizePolicy* size_policy() = 0;
432
433 // Iterate over all the ref-containing fields of all objects, calling
434 // "cl.do_oop" on each. This includes objects in permanent memory.
435 virtual void oop_iterate(OopClosure* cl) = 0;
436
437 // Iterate over all objects, calling "cl.do_object" on each.
438 // This includes objects in permanent memory.
439 virtual void object_iterate(ObjectClosure* cl) = 0;
440
441 // Behaves the same as oop_iterate, except only traverses
442 // interior pointers contained in permanent memory. If there
443 // is no permanent memory, does nothing.
444 virtual void permanent_oop_iterate(OopClosure* cl) = 0;
445
446 // Behaves the same as object_iterate, except only traverses
447 // object contained in permanent memory. If there is no
448 // permanent memory, does nothing.
449 virtual void permanent_object_iterate(ObjectClosure* cl) = 0;
450
451 // NOTE! There is no requirement that a collector implement these
452 // functions.
453 //
454 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
455 // each address in the (reserved) heap is a member of exactly
456 // one block. The defining characteristic of a block is that it is
457 // possible to find its size, and thus to progress forward to the next
458 // block. (Blocks may be of different sizes.) Thus, blocks may
459 // represent Java objects, or they might be free blocks in a
460 // free-list-based heap (or subheap), as long as the two kinds are
461 // distinguishable and the size of each is determinable.
462
463 // Returns the address of the start of the "block" that contains the
464 // address "addr". We say "blocks" instead of "object" since some heaps
465 // may not pack objects densely; a chunk may either be an object or a
466 // non-object.
467 virtual HeapWord* block_start(const void* addr) const = 0;
468
469 // Requires "addr" to be the start of a chunk, and returns its size.
470 // "addr + size" is required to be the start of a new chunk, or the end
471 // of the active area of the heap.
472 virtual size_t block_size(const HeapWord* addr) const = 0;
473
474 // Requires "addr" to be the start of a block, and returns "TRUE" iff
475 // the block is an object.
476 virtual bool block_is_obj(const HeapWord* addr) const = 0;
477
478 // Returns the longest time (in ms) that has elapsed since the last
479 // time that any part of the heap was examined by a garbage collection.
480 virtual jlong millis_since_last_gc() = 0;
481
482 // Perform any cleanup actions necessary before allowing a verification.
483 virtual void prepare_for_verify() = 0;
484
485 virtual void print() const = 0;
486 virtual void print_on(outputStream* st) const = 0;
487
488 // Print all GC threads (other than the VM thread)
489 // used by this heap.
490 virtual void print_gc_threads_on(outputStream* st) const = 0;
491 void print_gc_threads() { print_gc_threads_on(tty); }
492 // Iterator for all GC threads (other than VM thread)
493 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
494
495 // Print any relevant tracing info that flags imply.
496 // Default implementation does nothing.
497 virtual void print_tracing_info() const = 0;
498
499 // Heap verification
500 virtual void verify(bool allow_dirty, bool silent) = 0;
501
502 // Non product verification and debugging.
503 #ifndef PRODUCT
504 // Support for PromotionFailureALot. Return true if it's time to cause a
505 // promotion failure. The no-argument version uses
506 // this->_promotion_failure_alot_count as the counter.
507 inline bool promotion_should_fail(volatile size_t* count);
508 inline bool promotion_should_fail();
509
510 // Reset the PromotionFailureALot counters. Should be called at the end of a
511 // GC in which promotion failure ocurred.
512 inline void reset_promotion_should_fail(volatile size_t* count);
513 inline void reset_promotion_should_fail();
514 #endif // #ifndef PRODUCT
515
516 #ifdef ASSERT
517 static int fired_fake_oom() {
518 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
519 }
520 #endif
521 };
522
523 // Class to set and reset the GC cause for a CollectedHeap.
524
525 class GCCauseSetter : StackObj {
526 CollectedHeap* _heap;
527 GCCause::Cause _previous_cause;
528 public:
529 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
530 assert(SafepointSynchronize::is_at_safepoint(),
531 "This method manipulates heap state without locking");
532 _heap = heap;
533 _previous_cause = _heap->gc_cause();
534 _heap->set_gc_cause(cause);
535 }
536
537 ~GCCauseSetter() {
538 assert(SafepointSynchronize::is_at_safepoint(),
539 "This method manipulates heap state without locking");
540 _heap->set_gc_cause(_previous_cause);
541 }
542 };