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 1997-2008 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 space is an abstraction for the "storage units" backing
26 // up the generation abstraction. It includes specific
27 // implementations for keeping track of free and used space,
28 // for iterating over objects and free blocks, etc.
30 // Here's the Space hierarchy:
31 //
32 // - Space -- an asbtract base class describing a heap area
33 // - CompactibleSpace -- a space supporting compaction
34 // - CompactibleFreeListSpace -- (used for CMS generation)
35 // - ContiguousSpace -- a compactible space in which all free space
36 // is contiguous
37 // - EdenSpace -- contiguous space used as nursery
38 // - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation
39 // - OffsetTableContigSpace -- contiguous space with a block offset array
40 // that allows "fast" block_start calls
41 // - TenuredSpace -- (used for TenuredGeneration)
42 // - ContigPermSpace -- an offset table contiguous space for perm gen
44 // Forward decls.
45 class Space;
46 class BlockOffsetArray;
47 class BlockOffsetArrayContigSpace;
48 class Generation;
49 class CompactibleSpace;
50 class BlockOffsetTable;
51 class GenRemSet;
52 class CardTableRS;
53 class DirtyCardToOopClosure;
55 // An oop closure that is circumscribed by a filtering memory region.
56 class SpaceMemRegionOopsIterClosure: public OopClosure {
57 private:
58 OopClosure* _cl;
59 MemRegion _mr;
60 protected:
61 template <class T> void do_oop_work(T* p) {
62 if (_mr.contains(p)) {
63 _cl->do_oop(p);
64 }
65 }
66 public:
67 SpaceMemRegionOopsIterClosure(OopClosure* cl, MemRegion mr):
68 _cl(cl), _mr(mr) {}
69 virtual void do_oop(oop* p);
70 virtual void do_oop(narrowOop* p);
71 };
73 // A Space describes a heap area. Class Space is an abstract
74 // base class.
75 //
76 // Space supports allocation, size computation and GC support is provided.
77 //
78 // Invariant: bottom() and end() are on page_size boundaries and
79 // bottom() <= top() <= end()
80 // top() is inclusive and end() is exclusive.
82 class Space: public CHeapObj {
83 friend class VMStructs;
84 protected:
85 HeapWord* _bottom;
86 HeapWord* _end;
88 // Used in support of save_marks()
89 HeapWord* _saved_mark_word;
91 MemRegionClosure* _preconsumptionDirtyCardClosure;
93 // A sequential tasks done structure. This supports
94 // parallel GC, where we have threads dynamically
95 // claiming sub-tasks from a larger parallel task.
96 SequentialSubTasksDone _par_seq_tasks;
98 Space():
99 _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { }
101 public:
102 // Accessors
103 HeapWord* bottom() const { return _bottom; }
104 HeapWord* end() const { return _end; }
105 virtual void set_bottom(HeapWord* value) { _bottom = value; }
106 virtual void set_end(HeapWord* value) { _end = value; }
108 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
109 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
111 MemRegionClosure* preconsumptionDirtyCardClosure() const {
112 return _preconsumptionDirtyCardClosure;
113 }
114 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
115 _preconsumptionDirtyCardClosure = cl;
116 }
118 // Returns a subregion of the space containing all the objects in
119 // the space.
120 virtual MemRegion used_region() const { return MemRegion(bottom(), end()); }
122 // Returns a region that is guaranteed to contain (at least) all objects
123 // allocated at the time of the last call to "save_marks". If the space
124 // initializes its DirtyCardToOopClosure's specifying the "contig" option
125 // (that is, if the space is contiguous), then this region must contain only
126 // such objects: the memregion will be from the bottom of the region to the
127 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
128 // the space must distiguish between objects in the region allocated before
129 // and after the call to save marks.
130 virtual MemRegion used_region_at_save_marks() const {
131 return MemRegion(bottom(), saved_mark_word());
132 }
134 // Initialization.
135 // "initialize" should be called once on a space, before it is used for
136 // any purpose. The "mr" arguments gives the bounds of the space, and
137 // the "clear_space" argument should be true unless the memory in "mr" is
138 // known to be zeroed.
139 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
141 // The "clear" method must be called on a region that may have
142 // had allocation performed in it, but is now to be considered empty.
143 virtual void clear(bool mangle_space);
145 // For detecting GC bugs. Should only be called at GC boundaries, since
146 // some unused space may be used as scratch space during GC's.
147 // Default implementation does nothing. We also call this when expanding
148 // a space to satisfy an allocation request. See bug #4668531
149 virtual void mangle_unused_area() {}
150 virtual void mangle_unused_area_complete() {}
151 virtual void mangle_region(MemRegion mr) {}
153 // Testers
154 bool is_empty() const { return used() == 0; }
155 bool not_empty() const { return used() > 0; }
157 // Returns true iff the given the space contains the
158 // given address as part of an allocated object. For
159 // ceratin kinds of spaces, this might be a potentially
160 // expensive operation. To prevent performance problems
161 // on account of its inadvertent use in product jvm's,
162 // we restrict its use to assertion checks only.
163 virtual bool is_in(const void* p) const;
165 // Returns true iff the given reserved memory of the space contains the
166 // given address.
167 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
169 // Returns true iff the given block is not allocated.
170 virtual bool is_free_block(const HeapWord* p) const = 0;
172 // Test whether p is double-aligned
173 static bool is_aligned(void* p) {
174 return ((intptr_t)p & (sizeof(double)-1)) == 0;
175 }
177 // Size computations. Sizes are in bytes.
178 size_t capacity() const { return byte_size(bottom(), end()); }
179 virtual size_t used() const = 0;
180 virtual size_t free() const = 0;
182 // Iterate over all the ref-containing fields of all objects in the
183 // space, calling "cl.do_oop" on each. Fields in objects allocated by
184 // applications of the closure are not included in the iteration.
185 virtual void oop_iterate(OopClosure* cl);
187 // Same as above, restricted to the intersection of a memory region and
188 // the space. Fields in objects allocated by applications of the closure
189 // are not included in the iteration.
190 virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0;
192 // Iterate over all objects in the space, calling "cl.do_object" on
193 // each. Objects allocated by applications of the closure are not
194 // included in the iteration.
195 virtual void object_iterate(ObjectClosure* blk) = 0;
197 // Iterate over all objects that intersect with mr, calling "cl->do_object"
198 // on each. There is an exception to this: if this closure has already
199 // been invoked on an object, it may skip such objects in some cases. This is
200 // Most likely to happen in an "upwards" (ascending address) iteration of
201 // MemRegions.
202 virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
204 // Iterate over as many initialized objects in the space as possible,
205 // calling "cl.do_object_careful" on each. Return NULL if all objects
206 // in the space (at the start of the iteration) were iterated over.
207 // Return an address indicating the extent of the iteration in the
208 // event that the iteration had to return because of finding an
209 // uninitialized object in the space, or if the closure "cl"
210 // signalled early termination.
211 virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
212 virtual HeapWord* object_iterate_careful_m(MemRegion mr,
213 ObjectClosureCareful* cl);
215 // Create and return a new dirty card to oop closure. Can be
216 // overriden to return the appropriate type of closure
217 // depending on the type of space in which the closure will
218 // operate. ResourceArea allocated.
219 virtual DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
220 CardTableModRefBS::PrecisionStyle precision,
221 HeapWord* boundary = NULL);
223 // If "p" is in the space, returns the address of the start of the
224 // "block" that contains "p". We say "block" instead of "object" since
225 // some heaps may not pack objects densely; a chunk may either be an
226 // object or a non-object. If "p" is not in the space, return NULL.
227 virtual HeapWord* block_start_const(const void* p) const = 0;
229 // The non-const version may have benevolent side effects on the data
230 // structure supporting these calls, possibly speeding up future calls.
231 // The default implementation, however, is simply to call the const
232 // version.
233 inline virtual HeapWord* block_start(const void* p);
235 // Requires "addr" to be the start of a chunk, and returns its size.
236 // "addr + size" is required to be the start of a new chunk, or the end
237 // of the active area of the heap.
238 virtual size_t block_size(const HeapWord* addr) const = 0;
240 // Requires "addr" to be the start of a block, and returns "TRUE" iff
241 // the block is an object.
242 virtual bool block_is_obj(const HeapWord* addr) const = 0;
244 // Requires "addr" to be the start of a block, and returns "TRUE" iff
245 // the block is an object and the object is alive.
246 virtual bool obj_is_alive(const HeapWord* addr) const;
248 // Allocation (return NULL if full). Assumes the caller has established
249 // mutually exclusive access to the space.
250 virtual HeapWord* allocate(size_t word_size) = 0;
252 // Allocation (return NULL if full). Enforces mutual exclusion internally.
253 virtual HeapWord* par_allocate(size_t word_size) = 0;
255 // Returns true if this object has been allocated since a
256 // generation's "save_marks" call.
257 virtual bool obj_allocated_since_save_marks(const oop obj) const = 0;
259 // Mark-sweep-compact support: all spaces can update pointers to objects
260 // moving as a part of compaction.
261 virtual void adjust_pointers();
263 // PrintHeapAtGC support
264 virtual void print() const;
265 virtual void print_on(outputStream* st) const;
266 virtual void print_short() const;
267 virtual void print_short_on(outputStream* st) const;
270 // Accessor for parallel sequential tasks.
271 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
273 // IF "this" is a ContiguousSpace, return it, else return NULL.
274 virtual ContiguousSpace* toContiguousSpace() {
275 return NULL;
276 }
278 // Debugging
279 virtual void verify(bool allow_dirty) const = 0;
280 };
282 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
283 // OopClosure to (the addresses of) all the ref-containing fields that could
284 // be modified by virtue of the given MemRegion being dirty. (Note that
285 // because of the imprecise nature of the write barrier, this may iterate
286 // over oops beyond the region.)
287 // This base type for dirty card to oop closures handles memory regions
288 // in non-contiguous spaces with no boundaries, and should be sub-classed
289 // to support other space types. See ContiguousDCTOC for a sub-class
290 // that works with ContiguousSpaces.
292 class DirtyCardToOopClosure: public MemRegionClosureRO {
293 protected:
294 OopClosure* _cl;
295 Space* _sp;
296 CardTableModRefBS::PrecisionStyle _precision;
297 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
298 // pointing below boundary.
299 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
300 // a downwards traversal; this is the
301 // lowest location already done (or,
302 // alternatively, the lowest address that
303 // shouldn't be done again. NULL means infinity.)
304 NOT_PRODUCT(HeapWord* _last_bottom;)
305 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
307 // Get the actual top of the area on which the closure will
308 // operate, given where the top is assumed to be (the end of the
309 // memory region passed to do_MemRegion) and where the object
310 // at the top is assumed to start. For example, an object may
311 // start at the top but actually extend past the assumed top,
312 // in which case the top becomes the end of the object.
313 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
315 // Walk the given memory region from bottom to (actual) top
316 // looking for objects and applying the oop closure (_cl) to
317 // them. The base implementation of this treats the area as
318 // blocks, where a block may or may not be an object. Sub-
319 // classes should override this to provide more accurate
320 // or possibly more efficient walking.
321 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
323 public:
324 DirtyCardToOopClosure(Space* sp, OopClosure* cl,
325 CardTableModRefBS::PrecisionStyle precision,
326 HeapWord* boundary) :
327 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
328 _min_done(NULL) {
329 NOT_PRODUCT(_last_bottom = NULL);
330 NOT_PRODUCT(_last_explicit_min_done = NULL);
331 }
333 void do_MemRegion(MemRegion mr);
335 void set_min_done(HeapWord* min_done) {
336 _min_done = min_done;
337 NOT_PRODUCT(_last_explicit_min_done = _min_done);
338 }
339 #ifndef PRODUCT
340 void set_last_bottom(HeapWord* last_bottom) {
341 _last_bottom = last_bottom;
342 }
343 #endif
344 };
346 // A structure to represent a point at which objects are being copied
347 // during compaction.
348 class CompactPoint : public StackObj {
349 public:
350 Generation* gen;
351 CompactibleSpace* space;
352 HeapWord* threshold;
353 CompactPoint(Generation* _gen, CompactibleSpace* _space,
354 HeapWord* _threshold) :
355 gen(_gen), space(_space), threshold(_threshold) {}
356 };
359 // A space that supports compaction operations. This is usually, but not
360 // necessarily, a space that is normally contiguous. But, for example, a
361 // free-list-based space whose normal collection is a mark-sweep without
362 // compaction could still support compaction in full GC's.
364 class CompactibleSpace: public Space {
365 friend class VMStructs;
366 friend class CompactibleFreeListSpace;
367 friend class CompactingPermGenGen;
368 friend class CMSPermGenGen;
369 private:
370 HeapWord* _compaction_top;
371 CompactibleSpace* _next_compaction_space;
373 public:
374 CompactibleSpace() :
375 _compaction_top(NULL), _next_compaction_space(NULL) {}
377 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
378 virtual void clear(bool mangle_space);
380 // Used temporarily during a compaction phase to hold the value
381 // top should have when compaction is complete.
382 HeapWord* compaction_top() const { return _compaction_top; }
384 void set_compaction_top(HeapWord* value) {
385 assert(value == NULL || (value >= bottom() && value <= end()),
386 "should point inside space");
387 _compaction_top = value;
388 }
390 // Perform operations on the space needed after a compaction
391 // has been performed.
392 virtual void reset_after_compaction() {}
394 // Returns the next space (in the current generation) to be compacted in
395 // the global compaction order. Also is used to select the next
396 // space into which to compact.
398 virtual CompactibleSpace* next_compaction_space() const {
399 return _next_compaction_space;
400 }
402 void set_next_compaction_space(CompactibleSpace* csp) {
403 _next_compaction_space = csp;
404 }
406 // MarkSweep support phase2
408 // Start the process of compaction of the current space: compute
409 // post-compaction addresses, and insert forwarding pointers. The fields
410 // "cp->gen" and "cp->compaction_space" are the generation and space into
411 // which we are currently compacting. This call updates "cp" as necessary,
412 // and leaves the "compaction_top" of the final value of
413 // "cp->compaction_space" up-to-date. Offset tables may be updated in
414 // this phase as if the final copy had occurred; if so, "cp->threshold"
415 // indicates when the next such action should be taken.
416 virtual void prepare_for_compaction(CompactPoint* cp);
417 // MarkSweep support phase3
418 virtual void adjust_pointers();
419 // MarkSweep support phase4
420 virtual void compact();
422 // The maximum percentage of objects that can be dead in the compacted
423 // live part of a compacted space ("deadwood" support.)
424 virtual size_t allowed_dead_ratio() const { return 0; };
426 // Some contiguous spaces may maintain some data structures that should
427 // be updated whenever an allocation crosses a boundary. This function
428 // returns the first such boundary.
429 // (The default implementation returns the end of the space, so the
430 // boundary is never crossed.)
431 virtual HeapWord* initialize_threshold() { return end(); }
433 // "q" is an object of the given "size" that should be forwarded;
434 // "cp" names the generation ("gen") and containing "this" (which must
435 // also equal "cp->space"). "compact_top" is where in "this" the
436 // next object should be forwarded to. If there is room in "this" for
437 // the object, insert an appropriate forwarding pointer in "q".
438 // If not, go to the next compaction space (there must
439 // be one, since compaction must succeed -- we go to the first space of
440 // the previous generation if necessary, updating "cp"), reset compact_top
441 // and then forward. In either case, returns the new value of "compact_top".
442 // If the forwarding crosses "cp->threshold", invokes the "cross_threhold"
443 // function of the then-current compaction space, and updates "cp->threshold
444 // accordingly".
445 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
446 HeapWord* compact_top);
448 // Return a size with adjusments as required of the space.
449 virtual size_t adjust_object_size_v(size_t size) const { return size; }
451 protected:
452 // Used during compaction.
453 HeapWord* _first_dead;
454 HeapWord* _end_of_live;
456 // Minimum size of a free block.
457 virtual size_t minimum_free_block_size() const = 0;
459 // This the function is invoked when an allocation of an object covering
460 // "start" to "end occurs crosses the threshold; returns the next
461 // threshold. (The default implementation does nothing.)
462 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
463 return end();
464 }
466 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
467 // free block of the given "word_len", and that "q", were it an object,
468 // would not move if forwared. If the size allows, fill the free
469 // block with an object, to prevent excessive compaction. Returns "true"
470 // iff the free region was made deadspace, and modifies
471 // "allowed_deadspace_words" to reflect the number of available deadspace
472 // words remaining after this operation.
473 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
474 size_t word_len);
475 };
477 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) { \
478 /* Compute the new addresses for the live objects and store it in the mark \
479 * Used by universe::mark_sweep_phase2() \
480 */ \
481 HeapWord* compact_top; /* This is where we are currently compacting to. */ \
482 \
483 /* We're sure to be here before any objects are compacted into this \
484 * space, so this is a good time to initialize this: \
485 */ \
486 set_compaction_top(bottom()); \
487 \
488 if (cp->space == NULL) { \
489 assert(cp->gen != NULL, "need a generation"); \
490 assert(cp->threshold == NULL, "just checking"); \
491 assert(cp->gen->first_compaction_space() == this, "just checking"); \
492 cp->space = cp->gen->first_compaction_space(); \
493 compact_top = cp->space->bottom(); \
494 cp->space->set_compaction_top(compact_top); \
495 cp->threshold = cp->space->initialize_threshold(); \
496 } else { \
497 compact_top = cp->space->compaction_top(); \
498 } \
499 \
500 /* We allow some amount of garbage towards the bottom of the space, so \
501 * we don't start compacting before there is a significant gain to be made.\
502 * Occasionally, we want to ensure a full compaction, which is determined \
503 * by the MarkSweepAlwaysCompactCount parameter. \
504 */ \
505 int invocations = SharedHeap::heap()->perm_gen()->stat_record()->invocations;\
506 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0); \
507 \
508 size_t allowed_deadspace = 0; \
509 if (skip_dead) { \
510 const size_t ratio = allowed_dead_ratio(); \
511 allowed_deadspace = (capacity() * ratio / 100) / HeapWordSize; \
512 } \
513 \
514 HeapWord* q = bottom(); \
515 HeapWord* t = scan_limit(); \
516 \
517 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last \
518 live object. */ \
519 HeapWord* first_dead = end();/* The first dead object. */ \
520 LiveRange* liveRange = NULL; /* The current live range, recorded in the \
521 first header of preceding free area. */ \
522 _first_dead = first_dead; \
523 \
524 const intx interval = PrefetchScanIntervalInBytes; \
525 \
526 while (q < t) { \
527 assert(!block_is_obj(q) || \
528 oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() || \
529 oop(q)->mark()->has_bias_pattern(), \
530 "these are the only valid states during a mark sweep"); \
531 if (block_is_obj(q) && oop(q)->is_gc_marked()) { \
532 /* prefetch beyond q */ \
533 Prefetch::write(q, interval); \
534 /* size_t size = oop(q)->size(); changing this for cms for perm gen */\
535 size_t size = block_size(q); \
536 compact_top = cp->space->forward(oop(q), size, cp, compact_top); \
537 q += size; \
538 end_of_live = q; \
539 } else { \
540 /* run over all the contiguous dead objects */ \
541 HeapWord* end = q; \
542 do { \
543 /* prefetch beyond end */ \
544 Prefetch::write(end, interval); \
545 end += block_size(end); \
546 } while (end < t && (!block_is_obj(end) || !oop(end)->is_gc_marked()));\
547 \
548 /* see if we might want to pretend this object is alive so that \
549 * we don't have to compact quite as often. \
550 */ \
551 if (allowed_deadspace > 0 && q == compact_top) { \
552 size_t sz = pointer_delta(end, q); \
553 if (insert_deadspace(allowed_deadspace, q, sz)) { \
554 compact_top = cp->space->forward(oop(q), sz, cp, compact_top); \
555 q = end; \
556 end_of_live = end; \
557 continue; \
558 } \
559 } \
560 \
561 /* otherwise, it really is a free region. */ \
562 \
563 /* for the previous LiveRange, record the end of the live objects. */ \
564 if (liveRange) { \
565 liveRange->set_end(q); \
566 } \
567 \
568 /* record the current LiveRange object. \
569 * liveRange->start() is overlaid on the mark word. \
570 */ \
571 liveRange = (LiveRange*)q; \
572 liveRange->set_start(end); \
573 liveRange->set_end(end); \
574 \
575 /* see if this is the first dead region. */ \
576 if (q < first_dead) { \
577 first_dead = q; \
578 } \
579 \
580 /* move on to the next object */ \
581 q = end; \
582 } \
583 } \
584 \
585 assert(q == t, "just checking"); \
586 if (liveRange != NULL) { \
587 liveRange->set_end(q); \
588 } \
589 _end_of_live = end_of_live; \
590 if (end_of_live < first_dead) { \
591 first_dead = end_of_live; \
592 } \
593 _first_dead = first_dead; \
594 \
595 /* save the compaction_top of the compaction space. */ \
596 cp->space->set_compaction_top(compact_top); \
597 }
599 #define SCAN_AND_ADJUST_POINTERS(adjust_obj_size) { \
600 /* adjust all the interior pointers to point at the new locations of objects \
601 * Used by MarkSweep::mark_sweep_phase3() */ \
602 \
603 HeapWord* q = bottom(); \
604 HeapWord* t = _end_of_live; /* Established by "prepare_for_compaction". */ \
605 \
606 assert(_first_dead <= _end_of_live, "Stands to reason, no?"); \
607 \
608 if (q < t && _first_dead > q && \
609 !oop(q)->is_gc_marked()) { \
610 /* we have a chunk of the space which hasn't moved and we've \
611 * reinitialized the mark word during the previous pass, so we can't \
612 * use is_gc_marked for the traversal. */ \
613 HeapWord* end = _first_dead; \
614 \
615 while (q < end) { \
616 /* I originally tried to conjoin "block_start(q) == q" to the \
617 * assertion below, but that doesn't work, because you can't \
618 * accurately traverse previous objects to get to the current one \
619 * after their pointers (including pointers into permGen) have been \
620 * updated, until the actual compaction is done. dld, 4/00 */ \
621 assert(block_is_obj(q), \
622 "should be at block boundaries, and should be looking at objs"); \
623 \
624 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q))); \
625 \
626 /* point all the oops to the new location */ \
627 size_t size = oop(q)->adjust_pointers(); \
628 size = adjust_obj_size(size); \
629 \
630 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers()); \
631 \
632 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size)); \
633 \
634 q += size; \
635 } \
636 \
637 if (_first_dead == t) { \
638 q = t; \
639 } else { \
640 /* $$$ This is funky. Using this to read the previously written \
641 * LiveRange. See also use below. */ \
642 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer(); \
643 } \
644 } \
645 \
646 const intx interval = PrefetchScanIntervalInBytes; \
647 \
648 debug_only(HeapWord* prev_q = NULL); \
649 while (q < t) { \
650 /* prefetch beyond q */ \
651 Prefetch::write(q, interval); \
652 if (oop(q)->is_gc_marked()) { \
653 /* q is alive */ \
654 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q))); \
655 /* point all the oops to the new location */ \
656 size_t size = oop(q)->adjust_pointers(); \
657 size = adjust_obj_size(size); \
658 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers()); \
659 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size)); \
660 debug_only(prev_q = q); \
661 q += size; \
662 } else { \
663 /* q is not a live object, so its mark should point at the next \
664 * live object */ \
665 debug_only(prev_q = q); \
666 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
667 assert(q > prev_q, "we should be moving forward through memory"); \
668 } \
669 } \
670 \
671 assert(q == t, "just checking"); \
672 }
674 #define SCAN_AND_COMPACT(obj_size) { \
675 /* Copy all live objects to their new location \
676 * Used by MarkSweep::mark_sweep_phase4() */ \
677 \
678 HeapWord* q = bottom(); \
679 HeapWord* const t = _end_of_live; \
680 debug_only(HeapWord* prev_q = NULL); \
681 \
682 if (q < t && _first_dead > q && \
683 !oop(q)->is_gc_marked()) { \
684 debug_only( \
685 /* we have a chunk of the space which hasn't moved and we've reinitialized \
686 * the mark word during the previous pass, so we can't use is_gc_marked for \
687 * the traversal. */ \
688 HeapWord* const end = _first_dead; \
689 \
690 while (q < end) { \
691 size_t size = obj_size(q); \
692 assert(!oop(q)->is_gc_marked(), \
693 "should be unmarked (special dense prefix handling)"); \
694 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, q)); \
695 debug_only(prev_q = q); \
696 q += size; \
697 } \
698 ) /* debug_only */ \
699 \
700 if (_first_dead == t) { \
701 q = t; \
702 } else { \
703 /* $$$ Funky */ \
704 q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer(); \
705 } \
706 } \
707 \
708 const intx scan_interval = PrefetchScanIntervalInBytes; \
709 const intx copy_interval = PrefetchCopyIntervalInBytes; \
710 while (q < t) { \
711 if (!oop(q)->is_gc_marked()) { \
712 /* mark is pointer to next marked oop */ \
713 debug_only(prev_q = q); \
714 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
715 assert(q > prev_q, "we should be moving forward through memory"); \
716 } else { \
717 /* prefetch beyond q */ \
718 Prefetch::read(q, scan_interval); \
719 \
720 /* size and destination */ \
721 size_t size = obj_size(q); \
722 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee(); \
723 \
724 /* prefetch beyond compaction_top */ \
725 Prefetch::write(compaction_top, copy_interval); \
726 \
727 /* copy object and reinit its mark */ \
728 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, \
729 compaction_top)); \
730 assert(q != compaction_top, "everything in this pass should be moving"); \
731 Copy::aligned_conjoint_words(q, compaction_top, size); \
732 oop(compaction_top)->init_mark(); \
733 assert(oop(compaction_top)->klass() != NULL, "should have a class"); \
734 \
735 debug_only(prev_q = q); \
736 q += size; \
737 } \
738 } \
739 \
740 /* Let's remember if we were empty before we did the compaction. */ \
741 bool was_empty = used_region().is_empty(); \
742 /* Reset space after compaction is complete */ \
743 reset_after_compaction(); \
744 /* We do this clear, below, since it has overloaded meanings for some */ \
745 /* space subtypes. For example, OffsetTableContigSpace's that were */ \
746 /* compacted into will have had their offset table thresholds updated */ \
747 /* continuously, but those that weren't need to have their thresholds */ \
748 /* re-initialized. Also mangles unused area for debugging. */ \
749 if (used_region().is_empty()) { \
750 if (!was_empty) clear(SpaceDecorator::Mangle); \
751 } else { \
752 if (ZapUnusedHeapArea) mangle_unused_area(); \
753 } \
754 }
756 class GenSpaceMangler;
758 // A space in which the free area is contiguous. It therefore supports
759 // faster allocation, and compaction.
760 class ContiguousSpace: public CompactibleSpace {
761 friend class OneContigSpaceCardGeneration;
762 friend class VMStructs;
763 protected:
764 HeapWord* _top;
765 HeapWord* _concurrent_iteration_safe_limit;
766 // A helper for mangling the unused area of the space in debug builds.
767 GenSpaceMangler* _mangler;
769 GenSpaceMangler* mangler() { return _mangler; }
771 // Allocation helpers (return NULL if full).
772 inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
773 inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
775 public:
776 ContiguousSpace();
777 ~ContiguousSpace();
779 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
780 virtual void clear(bool mangle_space);
782 // Accessors
783 HeapWord* top() const { return _top; }
784 void set_top(HeapWord* value) { _top = value; }
786 virtual void set_saved_mark() { _saved_mark_word = top(); }
787 void reset_saved_mark() { _saved_mark_word = bottom(); }
789 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
790 WaterMark top_mark() { return WaterMark(this, top()); }
791 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
792 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
794 // In debug mode mangle (write it with a particular bit
795 // pattern) the unused part of a space.
797 // Used to save the an address in a space for later use during mangling.
798 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
799 // Used to save the space's current top for later use during mangling.
800 void set_top_for_allocations() PRODUCT_RETURN;
802 // Mangle regions in the space from the current top up to the
803 // previously mangled part of the space.
804 void mangle_unused_area() PRODUCT_RETURN;
805 // Mangle [top, end)
806 void mangle_unused_area_complete() PRODUCT_RETURN;
807 // Mangle the given MemRegion.
808 void mangle_region(MemRegion mr) PRODUCT_RETURN;
810 // Do some sparse checking on the area that should have been mangled.
811 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
812 // Check the complete area that should have been mangled.
813 // This code may be NULL depending on the macro DEBUG_MANGLING.
814 void check_mangled_unused_area_complete() PRODUCT_RETURN;
816 // Size computations: sizes in bytes.
817 size_t capacity() const { return byte_size(bottom(), end()); }
818 size_t used() const { return byte_size(bottom(), top()); }
819 size_t free() const { return byte_size(top(), end()); }
821 // Override from space.
822 bool is_in(const void* p) const;
824 virtual bool is_free_block(const HeapWord* p) const;
826 // In a contiguous space we have a more obvious bound on what parts
827 // contain objects.
828 MemRegion used_region() const { return MemRegion(bottom(), top()); }
830 MemRegion used_region_at_save_marks() const {
831 return MemRegion(bottom(), saved_mark_word());
832 }
834 // Allocation (return NULL if full)
835 virtual HeapWord* allocate(size_t word_size);
836 virtual HeapWord* par_allocate(size_t word_size);
838 virtual bool obj_allocated_since_save_marks(const oop obj) const {
839 return (HeapWord*)obj >= saved_mark_word();
840 }
842 // Iteration
843 void oop_iterate(OopClosure* cl);
844 void oop_iterate(MemRegion mr, OopClosure* cl);
845 void object_iterate(ObjectClosure* blk);
846 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
847 // iterates on objects up to the safe limit
848 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
849 inline HeapWord* concurrent_iteration_safe_limit();
850 // changes the safe limit, all objects from bottom() to the new
851 // limit should be properly initialized
852 inline void set_concurrent_iteration_safe_limit(HeapWord* new_limit);
854 #ifndef SERIALGC
855 // In support of parallel oop_iterate.
856 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
857 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
859 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
860 #undef ContigSpace_PAR_OOP_ITERATE_DECL
861 #endif // SERIALGC
863 // Compaction support
864 virtual void reset_after_compaction() {
865 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
866 set_top(compaction_top());
867 // set new iteration safe limit
868 set_concurrent_iteration_safe_limit(compaction_top());
869 }
870 virtual size_t minimum_free_block_size() const { return 0; }
872 // Override.
873 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
874 CardTableModRefBS::PrecisionStyle precision,
875 HeapWord* boundary = NULL);
877 // Apply "blk->do_oop" to the addresses of all reference fields in objects
878 // starting with the _saved_mark_word, which was noted during a generation's
879 // save_marks and is required to denote the head of an object.
880 // Fields in objects allocated by applications of the closure
881 // *are* included in the iteration.
882 // Updates _saved_mark_word to point to just after the last object
883 // iterated over.
884 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
885 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
887 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
888 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
890 // Same as object_iterate, but starting from "mark", which is required
891 // to denote the start of an object. Objects allocated by
892 // applications of the closure *are* included in the iteration.
893 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
895 // Very inefficient implementation.
896 virtual HeapWord* block_start_const(const void* p) const;
897 size_t block_size(const HeapWord* p) const;
898 // If a block is in the allocated area, it is an object.
899 bool block_is_obj(const HeapWord* p) const { return p < top(); }
901 // Addresses for inlined allocation
902 HeapWord** top_addr() { return &_top; }
903 HeapWord** end_addr() { return &_end; }
905 // Overrides for more efficient compaction support.
906 void prepare_for_compaction(CompactPoint* cp);
908 // PrintHeapAtGC support.
909 virtual void print_on(outputStream* st) const;
911 // Checked dynamic downcasts.
912 virtual ContiguousSpace* toContiguousSpace() {
913 return this;
914 }
916 // Debugging
917 virtual void verify(bool allow_dirty) const;
919 // Used to increase collection frequency. "factor" of 0 means entire
920 // space.
921 void allocate_temporary_filler(int factor);
923 };
926 // A dirty card to oop closure that does filtering.
927 // It knows how to filter out objects that are outside of the _boundary.
928 class Filtering_DCTOC : public DirtyCardToOopClosure {
929 protected:
930 // Override.
931 void walk_mem_region(MemRegion mr,
932 HeapWord* bottom, HeapWord* top);
934 // Walk the given memory region, from bottom to top, applying
935 // the given oop closure to (possibly) all objects found. The
936 // given oop closure may or may not be the same as the oop
937 // closure with which this closure was created, as it may
938 // be a filtering closure which makes use of the _boundary.
939 // We offer two signatures, so the FilteringClosure static type is
940 // apparent.
941 virtual void walk_mem_region_with_cl(MemRegion mr,
942 HeapWord* bottom, HeapWord* top,
943 OopClosure* cl) = 0;
944 virtual void walk_mem_region_with_cl(MemRegion mr,
945 HeapWord* bottom, HeapWord* top,
946 FilteringClosure* cl) = 0;
948 public:
949 Filtering_DCTOC(Space* sp, OopClosure* cl,
950 CardTableModRefBS::PrecisionStyle precision,
951 HeapWord* boundary) :
952 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
953 };
955 // A dirty card to oop closure for contiguous spaces
956 // (ContiguousSpace and sub-classes).
957 // It is a FilteringClosure, as defined above, and it knows:
958 //
959 // 1. That the actual top of any area in a memory region
960 // contained by the space is bounded by the end of the contiguous
961 // region of the space.
962 // 2. That the space is really made up of objects and not just
963 // blocks.
965 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
966 protected:
967 // Overrides.
968 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
970 virtual void walk_mem_region_with_cl(MemRegion mr,
971 HeapWord* bottom, HeapWord* top,
972 OopClosure* cl);
973 virtual void walk_mem_region_with_cl(MemRegion mr,
974 HeapWord* bottom, HeapWord* top,
975 FilteringClosure* cl);
977 public:
978 ContiguousSpaceDCTOC(ContiguousSpace* sp, OopClosure* cl,
979 CardTableModRefBS::PrecisionStyle precision,
980 HeapWord* boundary) :
981 Filtering_DCTOC(sp, cl, precision, boundary)
982 {}
983 };
986 // Class EdenSpace describes eden-space in new generation.
988 class DefNewGeneration;
990 class EdenSpace : public ContiguousSpace {
991 friend class VMStructs;
992 private:
993 DefNewGeneration* _gen;
995 // _soft_end is used as a soft limit on allocation. As soft limits are
996 // reached, the slow-path allocation code can invoke other actions and then
997 // adjust _soft_end up to a new soft limit or to end().
998 HeapWord* _soft_end;
1000 public:
1001 EdenSpace(DefNewGeneration* gen) :
1002 _gen(gen), _soft_end(NULL) {}
1004 // Get/set just the 'soft' limit.
1005 HeapWord* soft_end() { return _soft_end; }
1006 HeapWord** soft_end_addr() { return &_soft_end; }
1007 void set_soft_end(HeapWord* value) { _soft_end = value; }
1009 // Override.
1010 void clear(bool mangle_space);
1012 // Set both the 'hard' and 'soft' limits (_end and _soft_end).
1013 void set_end(HeapWord* value) {
1014 set_soft_end(value);
1015 ContiguousSpace::set_end(value);
1016 }
1018 // Allocation (return NULL if full)
1019 HeapWord* allocate(size_t word_size);
1020 HeapWord* par_allocate(size_t word_size);
1021 };
1023 // Class ConcEdenSpace extends EdenSpace for the sake of safe
1024 // allocation while soft-end is being modified concurrently
1026 class ConcEdenSpace : public EdenSpace {
1027 public:
1028 ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
1030 // Allocation (return NULL if full)
1031 HeapWord* par_allocate(size_t word_size);
1032 };
1035 // A ContigSpace that Supports an efficient "block_start" operation via
1036 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
1037 // other spaces.) This is the abstract base class for old generation
1038 // (tenured, perm) spaces.
1040 class OffsetTableContigSpace: public ContiguousSpace {
1041 friend class VMStructs;
1042 protected:
1043 BlockOffsetArrayContigSpace _offsets;
1044 Mutex _par_alloc_lock;
1046 public:
1047 // Constructor
1048 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
1049 MemRegion mr);
1051 void set_bottom(HeapWord* value);
1052 void set_end(HeapWord* value);
1054 void clear(bool mangle_space);
1056 inline HeapWord* block_start_const(const void* p) const;
1058 // Add offset table update.
1059 virtual inline HeapWord* allocate(size_t word_size);
1060 inline HeapWord* par_allocate(size_t word_size);
1062 // MarkSweep support phase3
1063 virtual HeapWord* initialize_threshold();
1064 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
1066 virtual void print_on(outputStream* st) const;
1068 // Debugging
1069 void verify(bool allow_dirty) const;
1071 // Shared space support
1072 void serialize_block_offset_array_offsets(SerializeOopClosure* soc);
1073 };
1076 // Class TenuredSpace is used by TenuredGeneration
1078 class TenuredSpace: public OffsetTableContigSpace {
1079 friend class VMStructs;
1080 protected:
1081 // Mark sweep support
1082 size_t allowed_dead_ratio() const;
1083 public:
1084 // Constructor
1085 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
1086 MemRegion mr) :
1087 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1088 };
1091 // Class ContigPermSpace is used by CompactingPermGen
1093 class ContigPermSpace: public OffsetTableContigSpace {
1094 friend class VMStructs;
1095 protected:
1096 // Mark sweep support
1097 size_t allowed_dead_ratio() const;
1098 public:
1099 // Constructor
1100 ContigPermSpace(BlockOffsetSharedArray* sharedOffsetArray, MemRegion mr) :
1101 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1102 };