Thu, 11 Dec 2008 12:05:08 -0800
6578152: fill_region_with_object has usability and safety issues
Reviewed-by: apetrusenko, ysr
1 /*
2 * Copyright 2001-2008 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 // Used for filler objects (static, but initialized in ctor).
51 static size_t _filler_array_max_size;
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 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
60 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
62 // Reason for current garbage collection. Should be set to
63 // a value reflecting no collection between collections.
64 GCCause::Cause _gc_cause;
65 GCCause::Cause _gc_lastcause;
66 PerfStringVariable* _perf_gc_cause;
67 PerfStringVariable* _perf_gc_lastcause;
69 // Constructor
70 CollectedHeap();
72 // Create a new tlab
73 virtual HeapWord* allocate_new_tlab(size_t size);
75 // Fix up tlabs to make the heap well-formed again,
76 // optionally retiring the tlabs.
77 virtual void fill_all_tlabs(bool retire);
79 // Accumulate statistics on all tlabs.
80 virtual void accumulate_statistics_all_tlabs();
82 // Reinitialize tlabs before resuming mutators.
83 virtual void resize_all_tlabs();
85 debug_only(static void check_for_valid_allocation_state();)
87 protected:
88 // Allocate from the current thread's TLAB, with broken-out slow path.
89 inline static HeapWord* allocate_from_tlab(Thread* thread, size_t size);
90 static HeapWord* allocate_from_tlab_slow(Thread* thread, size_t size);
92 // Allocate an uninitialized block of the given size, or returns NULL if
93 // this is impossible.
94 inline static HeapWord* common_mem_allocate_noinit(size_t size, bool is_noref, TRAPS);
96 // Like allocate_init, but the block returned by a successful allocation
97 // is guaranteed initialized to zeros.
98 inline static HeapWord* common_mem_allocate_init(size_t size, bool is_noref, TRAPS);
100 // Same as common_mem version, except memory is allocated in the permanent area
101 // If there is no permanent area, revert to common_mem_allocate_noinit
102 inline static HeapWord* common_permanent_mem_allocate_noinit(size_t size, TRAPS);
104 // Same as common_mem version, except memory is allocated in the permanent area
105 // If there is no permanent area, revert to common_mem_allocate_init
106 inline static HeapWord* common_permanent_mem_allocate_init(size_t size, TRAPS);
108 // Helper functions for (VM) allocation.
109 inline static void post_allocation_setup_common(KlassHandle klass,
110 HeapWord* obj, size_t size);
111 inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
112 HeapWord* objPtr,
113 size_t size);
115 inline static void post_allocation_setup_obj(KlassHandle klass,
116 HeapWord* obj, size_t size);
118 inline static void post_allocation_setup_array(KlassHandle klass,
119 HeapWord* obj, size_t size,
120 int length);
122 // Clears an allocated object.
123 inline static void init_obj(HeapWord* obj, size_t size);
125 // Filler object utilities.
126 static inline size_t filler_array_hdr_size();
127 static inline size_t filler_array_min_size();
128 static inline size_t filler_array_max_size();
130 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
131 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words);)
133 // Fill with a single array; caller must ensure filler_array_min_size() <=
134 // words <= filler_array_max_size().
135 static inline void fill_with_array(HeapWord* start, size_t words);
137 // Fill with a single object (either an int array or a java.lang.Object).
138 static inline void fill_with_object_impl(HeapWord* start, size_t words);
140 // Verification functions
141 virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
142 PRODUCT_RETURN;
143 virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
144 PRODUCT_RETURN;
146 public:
147 enum Name {
148 Abstract,
149 SharedHeap,
150 GenCollectedHeap,
151 ParallelScavengeHeap,
152 G1CollectedHeap
153 };
155 virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
157 /**
158 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
159 * and JNI_OK on success.
160 */
161 virtual jint initialize() = 0;
163 // In many heaps, there will be a need to perform some initialization activities
164 // after the Universe is fully formed, but before general heap allocation is allowed.
165 // This is the correct place to place such initialization methods.
166 virtual void post_initialize() = 0;
168 MemRegion reserved_region() const { return _reserved; }
169 address base() const { return (address)reserved_region().start(); }
171 // Future cleanup here. The following functions should specify bytes or
172 // heapwords as part of their signature.
173 virtual size_t capacity() const = 0;
174 virtual size_t used() const = 0;
176 // Return "true" if the part of the heap that allocates Java
177 // objects has reached the maximal committed limit that it can
178 // reach, without a garbage collection.
179 virtual bool is_maximal_no_gc() const = 0;
181 virtual size_t permanent_capacity() const = 0;
182 virtual size_t permanent_used() const = 0;
184 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
185 // memory that the vm could make available for storing 'normal' java objects.
186 // This is based on the reserved address space, but should not include space
187 // that the vm uses internally for bookkeeping or temporary storage (e.g.,
188 // perm gen space or, in the case of the young gen, one of the survivor
189 // spaces).
190 virtual size_t max_capacity() const = 0;
192 // Returns "TRUE" if "p" points into the reserved area of the heap.
193 bool is_in_reserved(const void* p) const {
194 return _reserved.contains(p);
195 }
197 bool is_in_reserved_or_null(const void* p) const {
198 return p == NULL || is_in_reserved(p);
199 }
201 // Returns "TRUE" if "p" points to the head of an allocated object in the
202 // heap. Since this method can be expensive in general, we restrict its
203 // use to assertion checking only.
204 virtual bool is_in(const void* p) const = 0;
206 bool is_in_or_null(const void* p) const {
207 return p == NULL || is_in(p);
208 }
210 // Let's define some terms: a "closed" subset of a heap is one that
211 //
212 // 1) contains all currently-allocated objects, and
213 //
214 // 2) is closed under reference: no object in the closed subset
215 // references one outside the closed subset.
216 //
217 // Membership in a heap's closed subset is useful for assertions.
218 // Clearly, the entire heap is a closed subset, so the default
219 // implementation is to use "is_in_reserved". But this may not be too
220 // liberal to perform useful checking. Also, the "is_in" predicate
221 // defines a closed subset, but may be too expensive, since "is_in"
222 // verifies that its argument points to an object head. The
223 // "closed_subset" method allows a heap to define an intermediate
224 // predicate, allowing more precise checking than "is_in_reserved" at
225 // lower cost than "is_in."
227 // One important case is a heap composed of disjoint contiguous spaces,
228 // such as the Garbage-First collector. Such heaps have a convenient
229 // closed subset consisting of the allocated portions of those
230 // contiguous spaces.
232 // Return "TRUE" iff the given pointer points into the heap's defined
233 // closed subset (which defaults to the entire heap).
234 virtual bool is_in_closed_subset(const void* p) const {
235 return is_in_reserved(p);
236 }
238 bool is_in_closed_subset_or_null(const void* p) const {
239 return p == NULL || is_in_closed_subset(p);
240 }
242 // Returns "TRUE" if "p" is allocated as "permanent" data.
243 // If the heap does not use "permanent" data, returns the same
244 // value is_in_reserved() would return.
245 // NOTE: this actually returns true if "p" is in reserved space
246 // for the space not that it is actually allocated (i.e. in committed
247 // space). If you need the more conservative answer use is_permanent().
248 virtual bool is_in_permanent(const void *p) const = 0;
250 // Returns "TRUE" if "p" is in the committed area of "permanent" data.
251 // If the heap does not use "permanent" data, returns the same
252 // value is_in() would return.
253 virtual bool is_permanent(const void *p) const = 0;
255 bool is_in_permanent_or_null(const void *p) const {
256 return p == NULL || is_in_permanent(p);
257 }
259 // Returns "TRUE" if "p" is a method oop in the
260 // current heap, with high probability. This predicate
261 // is not stable, in general.
262 bool is_valid_method(oop p) const;
264 void set_gc_cause(GCCause::Cause v) {
265 if (UsePerfData) {
266 _gc_lastcause = _gc_cause;
267 _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
268 _perf_gc_cause->set_value(GCCause::to_string(v));
269 }
270 _gc_cause = v;
271 }
272 GCCause::Cause gc_cause() { return _gc_cause; }
274 // Preload classes into the shared portion of the heap, and then dump
275 // that data to a file so that it can be loaded directly by another
276 // VM (then terminate).
277 virtual void preload_and_dump(TRAPS) { ShouldNotReachHere(); }
279 // General obj/array allocation facilities.
280 inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
281 inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
282 inline static oop large_typearray_allocate(KlassHandle klass, int size, int length, TRAPS);
284 // Special obj/array allocation facilities.
285 // Some heaps may want to manage "permanent" data uniquely. These default
286 // to the general routines if the heap does not support such handling.
287 inline static oop permanent_obj_allocate(KlassHandle klass, int size, TRAPS);
288 // permanent_obj_allocate_no_klass_install() does not do the installation of
289 // the klass pointer in the newly created object (as permanent_obj_allocate()
290 // above does). This allows for a delay in the installation of the klass
291 // pointer that is needed during the create of klassKlass's. The
292 // method post_allocation_install_obj_klass() is used to install the
293 // klass pointer.
294 inline static oop permanent_obj_allocate_no_klass_install(KlassHandle klass,
295 int size,
296 TRAPS);
297 inline static void post_allocation_install_obj_klass(KlassHandle klass,
298 oop obj,
299 int size);
300 inline static oop permanent_array_allocate(KlassHandle klass, int size, int length, TRAPS);
302 // Raw memory allocation facilities
303 // The obj and array allocate methods are covers for these methods.
304 // The permanent allocation method should default to mem_allocate if
305 // permanent memory isn't supported.
306 virtual HeapWord* mem_allocate(size_t size,
307 bool is_noref,
308 bool is_tlab,
309 bool* gc_overhead_limit_was_exceeded) = 0;
310 virtual HeapWord* permanent_mem_allocate(size_t size) = 0;
312 // The boundary between a "large" and "small" array of primitives, in words.
313 virtual size_t large_typearray_limit() = 0;
315 // Utilities for turning raw memory into filler objects.
316 //
317 // min_fill_size() is the smallest region that can be filled.
318 // fill_with_objects() can fill arbitrary-sized regions of the heap using
319 // multiple objects. fill_with_object() is for regions known to be smaller
320 // than the largest array of integers; it uses a single object to fill the
321 // region and has slightly less overhead.
322 static size_t min_fill_size() {
323 return size_t(align_object_size(oopDesc::header_size()));
324 }
326 static void fill_with_objects(HeapWord* start, size_t words);
328 static void fill_with_object(HeapWord* start, size_t words);
329 static void fill_with_object(MemRegion region) {
330 fill_with_object(region.start(), region.word_size());
331 }
332 static void fill_with_object(HeapWord* start, HeapWord* end) {
333 fill_with_object(start, pointer_delta(end, start));
334 }
336 // Some heaps may offer a contiguous region for shared non-blocking
337 // allocation, via inlined code (by exporting the address of the top and
338 // end fields defining the extent of the contiguous allocation region.)
340 // This function returns "true" iff the heap supports this kind of
341 // allocation. (Default is "no".)
342 virtual bool supports_inline_contig_alloc() const {
343 return false;
344 }
345 // These functions return the addresses of the fields that define the
346 // boundaries of the contiguous allocation area. (These fields should be
347 // physically near to one another.)
348 virtual HeapWord** top_addr() const {
349 guarantee(false, "inline contiguous allocation not supported");
350 return NULL;
351 }
352 virtual HeapWord** end_addr() const {
353 guarantee(false, "inline contiguous allocation not supported");
354 return NULL;
355 }
357 // Some heaps may be in an unparseable state at certain times between
358 // collections. This may be necessary for efficient implementation of
359 // certain allocation-related activities. Calling this function before
360 // attempting to parse a heap ensures that the heap is in a parsable
361 // state (provided other concurrent activity does not introduce
362 // unparsability). It is normally expected, therefore, that this
363 // method is invoked with the world stopped.
364 // NOTE: if you override this method, make sure you call
365 // super::ensure_parsability so that the non-generational
366 // part of the work gets done. See implementation of
367 // CollectedHeap::ensure_parsability and, for instance,
368 // that of GenCollectedHeap::ensure_parsability().
369 // The argument "retire_tlabs" controls whether existing TLABs
370 // are merely filled or also retired, thus preventing further
371 // allocation from them and necessitating allocation of new TLABs.
372 virtual void ensure_parsability(bool retire_tlabs);
374 // Return an estimate of the maximum allocation that could be performed
375 // without triggering any collection or expansion activity. In a
376 // generational collector, for example, this is probably the largest
377 // allocation that could be supported (without expansion) in the youngest
378 // generation. It is "unsafe" because no locks are taken; the result
379 // should be treated as an approximation, not a guarantee, for use in
380 // heuristic resizing decisions.
381 virtual size_t unsafe_max_alloc() = 0;
383 // Section on thread-local allocation buffers (TLABs)
384 // If the heap supports thread-local allocation buffers, it should override
385 // the following methods:
386 // Returns "true" iff the heap supports thread-local allocation buffers.
387 // The default is "no".
388 virtual bool supports_tlab_allocation() const {
389 return false;
390 }
391 // The amount of space available for thread-local allocation buffers.
392 virtual size_t tlab_capacity(Thread *thr) const {
393 guarantee(false, "thread-local allocation buffers not supported");
394 return 0;
395 }
396 // An estimate of the maximum allocation that could be performed
397 // for thread-local allocation buffers without triggering any
398 // collection or expansion activity.
399 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
400 guarantee(false, "thread-local allocation buffers not supported");
401 return 0;
402 }
403 // Can a compiler initialize a new object without store barriers?
404 // This permission only extends from the creation of a new object
405 // via a TLAB up to the first subsequent safepoint.
406 virtual bool can_elide_tlab_store_barriers() const = 0;
408 // If a compiler is eliding store barriers for TLAB-allocated objects,
409 // there is probably a corresponding slow path which can produce
410 // an object allocated anywhere. The compiler's runtime support
411 // promises to call this function on such a slow-path-allocated
412 // object before performing initializations that have elided
413 // store barriers. Returns new_obj, or maybe a safer copy thereof.
414 virtual oop new_store_barrier(oop new_obj);
416 // Can a compiler elide a store barrier when it writes
417 // a permanent oop into the heap? Applies when the compiler
418 // is storing x to the heap, where x->is_perm() is true.
419 virtual bool can_elide_permanent_oop_store_barriers() const = 0;
421 // Does this heap support heap inspection (+PrintClassHistogram?)
422 virtual bool supports_heap_inspection() const = 0;
424 // Perform a collection of the heap; intended for use in implementing
425 // "System.gc". This probably implies as full a collection as the
426 // "CollectedHeap" supports.
427 virtual void collect(GCCause::Cause cause) = 0;
429 // This interface assumes that it's being called by the
430 // vm thread. It collects the heap assuming that the
431 // heap lock is already held and that we are executing in
432 // the context of the vm thread.
433 virtual void collect_as_vm_thread(GCCause::Cause cause) = 0;
435 // Returns the barrier set for this heap
436 BarrierSet* barrier_set() { return _barrier_set; }
438 // Returns "true" iff there is a stop-world GC in progress. (I assume
439 // that it should answer "false" for the concurrent part of a concurrent
440 // collector -- dld).
441 bool is_gc_active() const { return _is_gc_active; }
443 // Total number of GC collections (started)
444 unsigned int total_collections() const { return _total_collections; }
445 unsigned int total_full_collections() const { return _total_full_collections;}
447 // Increment total number of GC collections (started)
448 // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
449 void increment_total_collections(bool full = false) {
450 _total_collections++;
451 if (full) {
452 increment_total_full_collections();
453 }
454 }
456 void increment_total_full_collections() { _total_full_collections++; }
458 // Return the AdaptiveSizePolicy for the heap.
459 virtual AdaptiveSizePolicy* size_policy() = 0;
461 // Iterate over all the ref-containing fields of all objects, calling
462 // "cl.do_oop" on each. This includes objects in permanent memory.
463 virtual void oop_iterate(OopClosure* cl) = 0;
465 // Iterate over all objects, calling "cl.do_object" on each.
466 // This includes objects in permanent memory.
467 virtual void object_iterate(ObjectClosure* cl) = 0;
469 // Behaves the same as oop_iterate, except only traverses
470 // interior pointers contained in permanent memory. If there
471 // is no permanent memory, does nothing.
472 virtual void permanent_oop_iterate(OopClosure* cl) = 0;
474 // Behaves the same as object_iterate, except only traverses
475 // object contained in permanent memory. If there is no
476 // permanent memory, does nothing.
477 virtual void permanent_object_iterate(ObjectClosure* cl) = 0;
479 // NOTE! There is no requirement that a collector implement these
480 // functions.
481 //
482 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
483 // each address in the (reserved) heap is a member of exactly
484 // one block. The defining characteristic of a block is that it is
485 // possible to find its size, and thus to progress forward to the next
486 // block. (Blocks may be of different sizes.) Thus, blocks may
487 // represent Java objects, or they might be free blocks in a
488 // free-list-based heap (or subheap), as long as the two kinds are
489 // distinguishable and the size of each is determinable.
491 // Returns the address of the start of the "block" that contains the
492 // address "addr". We say "blocks" instead of "object" since some heaps
493 // may not pack objects densely; a chunk may either be an object or a
494 // non-object.
495 virtual HeapWord* block_start(const void* addr) const = 0;
497 // Requires "addr" to be the start of a chunk, and returns its size.
498 // "addr + size" is required to be the start of a new chunk, or the end
499 // of the active area of the heap.
500 virtual size_t block_size(const HeapWord* addr) const = 0;
502 // Requires "addr" to be the start of a block, and returns "TRUE" iff
503 // the block is an object.
504 virtual bool block_is_obj(const HeapWord* addr) const = 0;
506 // Returns the longest time (in ms) that has elapsed since the last
507 // time that any part of the heap was examined by a garbage collection.
508 virtual jlong millis_since_last_gc() = 0;
510 // Perform any cleanup actions necessary before allowing a verification.
511 virtual void prepare_for_verify() = 0;
513 virtual void print() const = 0;
514 virtual void print_on(outputStream* st) const = 0;
516 // Print all GC threads (other than the VM thread)
517 // used by this heap.
518 virtual void print_gc_threads_on(outputStream* st) const = 0;
519 void print_gc_threads() { print_gc_threads_on(tty); }
520 // Iterator for all GC threads (other than VM thread)
521 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
523 // Print any relevant tracing info that flags imply.
524 // Default implementation does nothing.
525 virtual void print_tracing_info() const = 0;
527 // Heap verification
528 virtual void verify(bool allow_dirty, bool silent) = 0;
530 // Non product verification and debugging.
531 #ifndef PRODUCT
532 // Support for PromotionFailureALot. Return true if it's time to cause a
533 // promotion failure. The no-argument version uses
534 // this->_promotion_failure_alot_count as the counter.
535 inline bool promotion_should_fail(volatile size_t* count);
536 inline bool promotion_should_fail();
538 // Reset the PromotionFailureALot counters. Should be called at the end of a
539 // GC in which promotion failure ocurred.
540 inline void reset_promotion_should_fail(volatile size_t* count);
541 inline void reset_promotion_should_fail();
542 #endif // #ifndef PRODUCT
544 #ifdef ASSERT
545 static int fired_fake_oom() {
546 return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
547 }
548 #endif
549 };
551 // Class to set and reset the GC cause for a CollectedHeap.
553 class GCCauseSetter : StackObj {
554 CollectedHeap* _heap;
555 GCCause::Cause _previous_cause;
556 public:
557 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
558 assert(SafepointSynchronize::is_at_safepoint(),
559 "This method manipulates heap state without locking");
560 _heap = heap;
561 _previous_cause = _heap->gc_cause();
562 _heap->set_gc_cause(cause);
563 }
565 ~GCCauseSetter() {
566 assert(SafepointSynchronize::is_at_safepoint(),
567 "This method manipulates heap state without locking");
568 _heap->set_gc_cause(_previous_cause);
569 }
570 };