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1 /*
2 * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
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.
29
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
43
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;
54
55
56 // An oop closure that is circumscribed by a filtering memory region.
57 class SpaceMemRegionOopsIterClosure: public virtual OopClosure {
58 OopClosure* cl;
59 MemRegion mr;
60 public:
61 void do_oop(oop* p) {
62 if (mr.contains(p)) {
63 cl->do_oop(p);
64 }
65 }
66 SpaceMemRegionOopsIterClosure(OopClosure* _cl, MemRegion _mr): cl(_cl), mr(_mr) {}
67 };
68
69
70 // A Space describes a heap area. Class Space is an abstract
71 // base class.
72 //
73 // Space supports allocation, size computation and GC support is provided.
74 //
75 // Invariant: bottom() and end() are on page_size boundaries and
76 // bottom() <= top() <= end()
77 // top() is inclusive and end() is exclusive.
78
79 class Space: public CHeapObj {
80 friend class VMStructs;
81 protected:
82 HeapWord* _bottom;
83 HeapWord* _end;
84
85 // Used in support of save_marks()
86 HeapWord* _saved_mark_word;
87
88 MemRegionClosure* _preconsumptionDirtyCardClosure;
89
90 // A sequential tasks done structure. This supports
91 // parallel GC, where we have threads dynamically
92 // claiming sub-tasks from a larger parallel task.
93 SequentialSubTasksDone _par_seq_tasks;
94
95 Space():
96 _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { }
97
98 public:
99 // Accessors
100 HeapWord* bottom() const { return _bottom; }
101 HeapWord* end() const { return _end; }
102 virtual void set_bottom(HeapWord* value) { _bottom = value; }
103 virtual void set_end(HeapWord* value) { _end = value; }
104
105 HeapWord* saved_mark_word() const { return _saved_mark_word; }
106 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
107
108 MemRegionClosure* preconsumptionDirtyCardClosure() const {
109 return _preconsumptionDirtyCardClosure;
110 }
111 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
112 _preconsumptionDirtyCardClosure = cl;
113 }
114
115 // Returns a subregion of the space containing all the objects in
116 // the space.
117 virtual MemRegion used_region() const { return MemRegion(bottom(), end()); }
118
119 // Returns a region that is guaranteed to contain (at least) all objects
120 // allocated at the time of the last call to "save_marks". If the space
121 // initializes its DirtyCardToOopClosure's specifying the "contig" option
122 // (that is, if the space is contiguous), then this region must contain only
123 // such objects: the memregion will be from the bottom of the region to the
124 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
125 // the space must distiguish between objects in the region allocated before
126 // and after the call to save marks.
127 virtual MemRegion used_region_at_save_marks() const {
128 return MemRegion(bottom(), saved_mark_word());
129 }
130
131 // Initialization
132 virtual void initialize(MemRegion mr, bool clear_space);
133 virtual void clear();
134
135 // For detecting GC bugs. Should only be called at GC boundaries, since
136 // some unused space may be used as scratch space during GC's.
137 // Default implementation does nothing. We also call this when expanding
138 // a space to satisfy an allocation request. See bug #4668531
139 virtual void mangle_unused_area() {}
140 virtual void mangle_region(MemRegion mr) {}
141
142 // Testers
143 bool is_empty() const { return used() == 0; }
144 bool not_empty() const { return used() > 0; }
145
146 // Returns true iff the given the space contains the
147 // given address as part of an allocated object. For
148 // ceratin kinds of spaces, this might be a potentially
149 // expensive operation. To prevent performance problems
150 // on account of its inadvertent use in product jvm's,
151 // we restrict its use to assertion checks only.
152 virtual bool is_in(const void* p) const;
153
154 // Returns true iff the given reserved memory of the space contains the
155 // given address.
156 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
157
158 // Returns true iff the given block is not allocated.
159 virtual bool is_free_block(const HeapWord* p) const = 0;
160
161 // Test whether p is double-aligned
162 static bool is_aligned(void* p) {
163 return ((intptr_t)p & (sizeof(double)-1)) == 0;
164 }
165
166 // Size computations. Sizes are in bytes.
167 size_t capacity() const { return byte_size(bottom(), end()); }
168 virtual size_t used() const = 0;
169 virtual size_t free() const = 0;
170
171 // Iterate over all the ref-containing fields of all objects in the
172 // space, calling "cl.do_oop" on each. Fields in objects allocated by
173 // applications of the closure are not included in the iteration.
174 virtual void oop_iterate(OopClosure* cl);
175
176 // Same as above, restricted to the intersection of a memory region and
177 // the space. Fields in objects allocated by applications of the closure
178 // are not included in the iteration.
179 virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0;
180
181 // Iterate over all objects in the space, calling "cl.do_object" on
182 // each. Objects allocated by applications of the closure are not
183 // included in the iteration.
184 virtual void object_iterate(ObjectClosure* blk) = 0;
185
186 // Iterate over all objects that intersect with mr, calling "cl->do_object"
187 // on each. There is an exception to this: if this closure has already
188 // been invoked on an object, it may skip such objects in some cases. This is
189 // Most likely to happen in an "upwards" (ascending address) iteration of
190 // MemRegions.
191 virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
192
193 // Iterate over as many initialized objects in the space as possible,
194 // calling "cl.do_object_careful" on each. Return NULL if all objects
195 // in the space (at the start of the iteration) were iterated over.
196 // Return an address indicating the extent of the iteration in the
197 // event that the iteration had to return because of finding an
198 // uninitialized object in the space, or if the closure "cl"
199 // signalled early termination.
200 virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
201 virtual HeapWord* object_iterate_careful_m(MemRegion mr,
202 ObjectClosureCareful* cl);
203
204 // Create and return a new dirty card to oop closure. Can be
205 // overriden to return the appropriate type of closure
206 // depending on the type of space in which the closure will
207 // operate. ResourceArea allocated.
208 virtual DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
209 CardTableModRefBS::PrecisionStyle precision,
210 HeapWord* boundary = NULL);
211
212 // If "p" is in the space, returns the address of the start of the
213 // "block" that contains "p". We say "block" instead of "object" since
214 // some heaps may not pack objects densely; a chunk may either be an
215 // object or a non-object. If "p" is not in the space, return NULL.
216 virtual HeapWord* block_start(const void* p) const = 0;
217
218 // Requires "addr" to be the start of a chunk, and returns its size.
219 // "addr + size" is required to be the start of a new chunk, or the end
220 // of the active area of the heap.
221 virtual size_t block_size(const HeapWord* addr) const = 0;
222
223 // Requires "addr" to be the start of a block, and returns "TRUE" iff
224 // the block is an object.
225 virtual bool block_is_obj(const HeapWord* addr) const = 0;
226
227 // Requires "addr" to be the start of a block, and returns "TRUE" iff
228 // the block is an object and the object is alive.
229 virtual bool obj_is_alive(const HeapWord* addr) const;
230
231 // Allocation (return NULL if full). Assumes the caller has established
232 // mutually exclusive access to the space.
233 virtual HeapWord* allocate(size_t word_size) = 0;
234
235 // Allocation (return NULL if full). Enforces mutual exclusion internally.
236 virtual HeapWord* par_allocate(size_t word_size) = 0;
237
238 // Returns true if this object has been allocated since a
239 // generation's "save_marks" call.
240 virtual bool obj_allocated_since_save_marks(const oop obj) const = 0;
241
242 // Mark-sweep-compact support: all spaces can update pointers to objects
243 // moving as a part of compaction.
244 virtual void adjust_pointers();
245
246 // PrintHeapAtGC support
247 virtual void print() const;
248 virtual void print_on(outputStream* st) const;
249 virtual void print_short() const;
250 virtual void print_short_on(outputStream* st) const;
251
252
253 // Accessor for parallel sequential tasks.
254 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
255
256 // IF "this" is a ContiguousSpace, return it, else return NULL.
257 virtual ContiguousSpace* toContiguousSpace() {
258 return NULL;
259 }
260
261 // Debugging
262 virtual void verify(bool allow_dirty) const = 0;
263 };
264
265 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
266 // OopClosure to (the addresses of) all the ref-containing fields that could
267 // be modified by virtue of the given MemRegion being dirty. (Note that
268 // because of the imprecise nature of the write barrier, this may iterate
269 // over oops beyond the region.)
270 // This base type for dirty card to oop closures handles memory regions
271 // in non-contiguous spaces with no boundaries, and should be sub-classed
272 // to support other space types. See ContiguousDCTOC for a sub-class
273 // that works with ContiguousSpaces.
274
275 class DirtyCardToOopClosure: public MemRegionClosureRO {
276 protected:
277 OopClosure* _cl;
278 Space* _sp;
279 CardTableModRefBS::PrecisionStyle _precision;
280 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
281 // pointing below boundary.
282 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
283 // a downwards traversal; this is the
284 // lowest location already done (or,
285 // alternatively, the lowest address that
286 // shouldn't be done again. NULL means infinity.)
287 NOT_PRODUCT(HeapWord* _last_bottom;)
288
289 // Get the actual top of the area on which the closure will
290 // operate, given where the top is assumed to be (the end of the
291 // memory region passed to do_MemRegion) and where the object
292 // at the top is assumed to start. For example, an object may
293 // start at the top but actually extend past the assumed top,
294 // in which case the top becomes the end of the object.
295 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
296
297 // Walk the given memory region from bottom to (actual) top
298 // looking for objects and applying the oop closure (_cl) to
299 // them. The base implementation of this treats the area as
300 // blocks, where a block may or may not be an object. Sub-
301 // classes should override this to provide more accurate
302 // or possibly more efficient walking.
303 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
304
305 public:
306 DirtyCardToOopClosure(Space* sp, OopClosure* cl,
307 CardTableModRefBS::PrecisionStyle precision,
308 HeapWord* boundary) :
309 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
310 _min_done(NULL) {
311 NOT_PRODUCT(_last_bottom = NULL;)
312 }
313
314 void do_MemRegion(MemRegion mr);
315
316 void set_min_done(HeapWord* min_done) {
317 _min_done = min_done;
318 }
319 #ifndef PRODUCT
320 void set_last_bottom(HeapWord* last_bottom) {
321 _last_bottom = last_bottom;
322 }
323 #endif
324 };
325
326 // A structure to represent a point at which objects are being copied
327 // during compaction.
328 class CompactPoint : public StackObj {
329 public:
330 Generation* gen;
331 CompactibleSpace* space;
332 HeapWord* threshold;
333 CompactPoint(Generation* _gen, CompactibleSpace* _space,
334 HeapWord* _threshold) :
335 gen(_gen), space(_space), threshold(_threshold) {}
336 };
337
338
339 // A space that supports compaction operations. This is usually, but not
340 // necessarily, a space that is normally contiguous. But, for example, a
341 // free-list-based space whose normal collection is a mark-sweep without
342 // compaction could still support compaction in full GC's.
343
344 class CompactibleSpace: public Space {
345 friend class VMStructs;
346 friend class CompactibleFreeListSpace;
347 friend class CompactingPermGenGen;
348 friend class CMSPermGenGen;
349 private:
350 HeapWord* _compaction_top;
351 CompactibleSpace* _next_compaction_space;
352
353 public:
354 virtual void initialize(MemRegion mr, bool clear_space);
355
356 // Used temporarily during a compaction phase to hold the value
357 // top should have when compaction is complete.
358 HeapWord* compaction_top() const { return _compaction_top; }
359
360 void set_compaction_top(HeapWord* value) {
361 assert(value == NULL || (value >= bottom() && value <= end()),
362 "should point inside space");
363 _compaction_top = value;
364 }
365
366 // Perform operations on the space needed after a compaction
367 // has been performed.
368 virtual void reset_after_compaction() {}
369
370 // Returns the next space (in the current generation) to be compacted in
371 // the global compaction order. Also is used to select the next
372 // space into which to compact.
373
374 virtual CompactibleSpace* next_compaction_space() const {
375 return _next_compaction_space;
376 }
377
378 void set_next_compaction_space(CompactibleSpace* csp) {
379 _next_compaction_space = csp;
380 }
381
382 // MarkSweep support phase2
383
384 // Start the process of compaction of the current space: compute
385 // post-compaction addresses, and insert forwarding pointers. The fields
386 // "cp->gen" and "cp->compaction_space" are the generation and space into
387 // which we are currently compacting. This call updates "cp" as necessary,
388 // and leaves the "compaction_top" of the final value of
389 // "cp->compaction_space" up-to-date. Offset tables may be updated in
390 // this phase as if the final copy had occurred; if so, "cp->threshold"
391 // indicates when the next such action should be taken.
392 virtual void prepare_for_compaction(CompactPoint* cp);
393 // MarkSweep support phase3
394 virtual void adjust_pointers();
395 // MarkSweep support phase4
396 virtual void compact();
397
398 // The maximum percentage of objects that can be dead in the compacted
399 // live part of a compacted space ("deadwood" support.)
400 virtual int allowed_dead_ratio() const { return 0; };
401
402 // Some contiguous spaces may maintain some data structures that should
403 // be updated whenever an allocation crosses a boundary. This function
404 // returns the first such boundary.
405 // (The default implementation returns the end of the space, so the
406 // boundary is never crossed.)
407 virtual HeapWord* initialize_threshold() { return end(); }
408
409 // "q" is an object of the given "size" that should be forwarded;
410 // "cp" names the generation ("gen") and containing "this" (which must
411 // also equal "cp->space"). "compact_top" is where in "this" the
412 // next object should be forwarded to. If there is room in "this" for
413 // the object, insert an appropriate forwarding pointer in "q".
414 // If not, go to the next compaction space (there must
415 // be one, since compaction must succeed -- we go to the first space of
416 // the previous generation if necessary, updating "cp"), reset compact_top
417 // and then forward. In either case, returns the new value of "compact_top".
418 // If the forwarding crosses "cp->threshold", invokes the "cross_threhold"
419 // function of the then-current compaction space, and updates "cp->threshold
420 // accordingly".
421 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
422 HeapWord* compact_top);
423
424 // Return a size with adjusments as required of the space.
425 virtual size_t adjust_object_size_v(size_t size) const { return size; }
426
427 protected:
428 // Used during compaction.
429 HeapWord* _first_dead;
430 HeapWord* _end_of_live;
431
432 // Minimum size of a free block.
433 virtual size_t minimum_free_block_size() const = 0;
434
435 // This the function is invoked when an allocation of an object covering
436 // "start" to "end occurs crosses the threshold; returns the next
437 // threshold. (The default implementation does nothing.)
438 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
439 return end();
440 }
441
442 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
443 // free block of the given "word_len", and that "q", were it an object,
444 // would not move if forwared. If the size allows, fill the free
445 // block with an object, to prevent excessive compaction. Returns "true"
446 // iff the free region was made deadspace, and modifies
447 // "allowed_deadspace_words" to reflect the number of available deadspace
448 // words remaining after this operation.
449 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
450 size_t word_len);
451 };
452
453 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) { \
454 /* Compute the new addresses for the live objects and store it in the mark \
455 * Used by universe::mark_sweep_phase2() \
456 */ \
457 HeapWord* compact_top; /* This is where we are currently compacting to. */ \
458 \
459 /* We're sure to be here before any objects are compacted into this \
460 * space, so this is a good time to initialize this: \
461 */ \
462 set_compaction_top(bottom()); \
463 \
464 if (cp->space == NULL) { \
465 assert(cp->gen != NULL, "need a generation"); \
466 assert(cp->threshold == NULL, "just checking"); \
467 assert(cp->gen->first_compaction_space() == this, "just checking"); \
468 cp->space = cp->gen->first_compaction_space(); \
469 compact_top = cp->space->bottom(); \
470 cp->space->set_compaction_top(compact_top); \
471 cp->threshold = cp->space->initialize_threshold(); \
472 } else { \
473 compact_top = cp->space->compaction_top(); \
474 } \
475 \
476 /* We allow some amount of garbage towards the bottom of the space, so \
477 * we don't start compacting before there is a significant gain to be made.\
478 * Occasionally, we want to ensure a full compaction, which is determined \
479 * by the MarkSweepAlwaysCompactCount parameter. \
480 */ \
481 int invocations = SharedHeap::heap()->perm_gen()->stat_record()->invocations;\
482 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0); \
483 \
484 size_t allowed_deadspace = 0; \
485 if (skip_dead) { \
486 int ratio = allowed_dead_ratio(); \
487 allowed_deadspace = (capacity() * ratio / 100) / HeapWordSize; \
488 } \
489 \
490 HeapWord* q = bottom(); \
491 HeapWord* t = scan_limit(); \
492 \
493 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last \
494 live object. */ \
495 HeapWord* first_dead = end();/* The first dead object. */ \
496 LiveRange* liveRange = NULL; /* The current live range, recorded in the \
497 first header of preceding free area. */ \
498 _first_dead = first_dead; \
499 \
500 const intx interval = PrefetchScanIntervalInBytes; \
501 \
502 while (q < t) { \
503 assert(!block_is_obj(q) || \
504 oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() || \
505 oop(q)->mark()->has_bias_pattern(), \
506 "these are the only valid states during a mark sweep"); \
507 if (block_is_obj(q) && oop(q)->is_gc_marked()) { \
508 /* prefetch beyond q */ \
509 Prefetch::write(q, interval); \
510 /* size_t size = oop(q)->size(); changing this for cms for perm gen */\
511 size_t size = block_size(q); \
512 compact_top = cp->space->forward(oop(q), size, cp, compact_top); \
513 q += size; \
514 end_of_live = q; \
515 } else { \
516 /* run over all the contiguous dead objects */ \
517 HeapWord* end = q; \
518 do { \
519 /* prefetch beyond end */ \
520 Prefetch::write(end, interval); \
521 end += block_size(end); \
522 } while (end < t && (!block_is_obj(end) || !oop(end)->is_gc_marked()));\
523 \
524 /* see if we might want to pretend this object is alive so that \
525 * we don't have to compact quite as often. \
526 */ \
527 if (allowed_deadspace > 0 && q == compact_top) { \
528 size_t sz = pointer_delta(end, q); \
529 if (insert_deadspace(allowed_deadspace, q, sz)) { \
530 compact_top = cp->space->forward(oop(q), sz, cp, compact_top); \
531 q = end; \
532 end_of_live = end; \
533 continue; \
534 } \
535 } \
536 \
537 /* otherwise, it really is a free region. */ \
538 \
539 /* for the previous LiveRange, record the end of the live objects. */ \
540 if (liveRange) { \
541 liveRange->set_end(q); \
542 } \
543 \
544 /* record the current LiveRange object. \
545 * liveRange->start() is overlaid on the mark word. \
546 */ \
547 liveRange = (LiveRange*)q; \
548 liveRange->set_start(end); \
549 liveRange->set_end(end); \
550 \
551 /* see if this is the first dead region. */ \
552 if (q < first_dead) { \
553 first_dead = q; \
554 } \
555 \
556 /* move on to the next object */ \
557 q = end; \
558 } \
559 } \
560 \
561 assert(q == t, "just checking"); \
562 if (liveRange != NULL) { \
563 liveRange->set_end(q); \
564 } \
565 _end_of_live = end_of_live; \
566 if (end_of_live < first_dead) { \
567 first_dead = end_of_live; \
568 } \
569 _first_dead = first_dead; \
570 \
571 /* save the compaction_top of the compaction space. */ \
572 cp->space->set_compaction_top(compact_top); \
573 }
574
575 #define SCAN_AND_ADJUST_POINTERS(adjust_obj_size) { \
576 /* adjust all the interior pointers to point at the new locations of objects \
577 * Used by MarkSweep::mark_sweep_phase3() */ \
578 \
579 HeapWord* q = bottom(); \
580 HeapWord* t = _end_of_live; /* Established by "prepare_for_compaction". */ \
581 \
582 assert(_first_dead <= _end_of_live, "Stands to reason, no?"); \
583 \
584 if (q < t && _first_dead > q && \
585 !oop(q)->is_gc_marked()) { \
586 /* we have a chunk of the space which hasn't moved and we've \
587 * reinitialized the mark word during the previous pass, so we can't \
588 * use is_gc_marked for the traversal. */ \
589 HeapWord* end = _first_dead; \
590 \
591 while (q < end) { \
592 /* I originally tried to conjoin "block_start(q) == q" to the \
593 * assertion below, but that doesn't work, because you can't \
594 * accurately traverse previous objects to get to the current one \
595 * after their pointers (including pointers into permGen) have been \
596 * updated, until the actual compaction is done. dld, 4/00 */ \
597 assert(block_is_obj(q), \
598 "should be at block boundaries, and should be looking at objs"); \
599 \
600 debug_only(MarkSweep::track_interior_pointers(oop(q))); \
601 \
602 /* point all the oops to the new location */ \
603 size_t size = oop(q)->adjust_pointers(); \
604 size = adjust_obj_size(size); \
605 \
606 debug_only(MarkSweep::check_interior_pointers()); \
607 \
608 debug_only(MarkSweep::validate_live_oop(oop(q), size)); \
609 \
610 q += size; \
611 } \
612 \
613 if (_first_dead == t) { \
614 q = t; \
615 } else { \
616 /* $$$ This is funky. Using this to read the previously written \
617 * LiveRange. See also use below. */ \
618 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer(); \
619 } \
620 } \
621 \
622 const intx interval = PrefetchScanIntervalInBytes; \
623 \
624 debug_only(HeapWord* prev_q = NULL); \
625 while (q < t) { \
626 /* prefetch beyond q */ \
627 Prefetch::write(q, interval); \
628 if (oop(q)->is_gc_marked()) { \
629 /* q is alive */ \
630 debug_only(MarkSweep::track_interior_pointers(oop(q))); \
631 /* point all the oops to the new location */ \
632 size_t size = oop(q)->adjust_pointers(); \
633 size = adjust_obj_size(size); \
634 debug_only(MarkSweep::check_interior_pointers()); \
635 debug_only(MarkSweep::validate_live_oop(oop(q), size)); \
636 debug_only(prev_q = q); \
637 q += size; \
638 } else { \
639 /* q is not a live object, so its mark should point at the next \
640 * live object */ \
641 debug_only(prev_q = q); \
642 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
643 assert(q > prev_q, "we should be moving forward through memory"); \
644 } \
645 } \
646 \
647 assert(q == t, "just checking"); \
648 }
649
650 #define SCAN_AND_COMPACT(obj_size) { \
651 /* Copy all live objects to their new location \
652 * Used by MarkSweep::mark_sweep_phase4() */ \
653 \
654 HeapWord* q = bottom(); \
655 HeapWord* const t = _end_of_live; \
656 debug_only(HeapWord* prev_q = NULL); \
657 \
658 if (q < t && _first_dead > q && \
659 !oop(q)->is_gc_marked()) { \
660 debug_only( \
661 /* we have a chunk of the space which hasn't moved and we've reinitialized the \
662 * mark word during the previous pass, so we can't use is_gc_marked for the \
663 * traversal. */ \
664 HeapWord* const end = _first_dead; \
665 \
666 while (q < end) { \
667 size_t size = obj_size(q); \
668 assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)"); \
669 debug_only(MarkSweep::live_oop_moved_to(q, size, q)); \
670 debug_only(prev_q = q); \
671 q += size; \
672 } \
673 ) /* debug_only */ \
674 \
675 if (_first_dead == t) { \
676 q = t; \
677 } else { \
678 /* $$$ Funky */ \
679 q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer(); \
680 } \
681 } \
682 \
683 const intx scan_interval = PrefetchScanIntervalInBytes; \
684 const intx copy_interval = PrefetchCopyIntervalInBytes; \
685 while (q < t) { \
686 if (!oop(q)->is_gc_marked()) { \
687 /* mark is pointer to next marked oop */ \
688 debug_only(prev_q = q); \
689 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
690 assert(q > prev_q, "we should be moving forward through memory"); \
691 } else { \
692 /* prefetch beyond q */ \
693 Prefetch::read(q, scan_interval); \
694 \
695 /* size and destination */ \
696 size_t size = obj_size(q); \
697 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee(); \
698 \
699 /* prefetch beyond compaction_top */ \
700 Prefetch::write(compaction_top, copy_interval); \
701 \
702 /* copy object and reinit its mark */ \
703 debug_only(MarkSweep::live_oop_moved_to(q, size, compaction_top)); \
704 assert(q != compaction_top, "everything in this pass should be moving"); \
705 Copy::aligned_conjoint_words(q, compaction_top, size); \
706 oop(compaction_top)->init_mark(); \
707 assert(oop(compaction_top)->klass() != NULL, "should have a class"); \
708 \
709 debug_only(prev_q = q); \
710 q += size; \
711 } \
712 } \
713 \
714 /* Reset space after compaction is complete */ \
715 reset_after_compaction(); \
716 /* We do this clear, below, since it has overloaded meanings for some */ \
717 /* space subtypes. For example, OffsetTableContigSpace's that were */ \
718 /* compacted into will have had their offset table thresholds updated */ \
719 /* continuously, but those that weren't need to have their thresholds */ \
720 /* re-initialized. Also mangles unused area for debugging. */ \
721 if (is_empty()) { \
722 clear(); \
723 } else { \
724 if (ZapUnusedHeapArea) mangle_unused_area(); \
725 } \
726 }
727
728 // A space in which the free area is contiguous. It therefore supports
729 // faster allocation, and compaction.
730 class ContiguousSpace: public CompactibleSpace {
731 friend class OneContigSpaceCardGeneration;
732 friend class VMStructs;
733 protected:
734 HeapWord* _top;
735 HeapWord* _concurrent_iteration_safe_limit;
736
737 // Allocation helpers (return NULL if full).
738 inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
739 inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
740
741 public:
742 virtual void initialize(MemRegion mr, bool clear_space);
743
744 // Accessors
745 HeapWord* top() const { return _top; }
746 void set_top(HeapWord* value) { _top = value; }
747
748 void set_saved_mark() { _saved_mark_word = top(); }
749 void reset_saved_mark() { _saved_mark_word = bottom(); }
750
751 virtual void clear();
752
753 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
754 WaterMark top_mark() { return WaterMark(this, top()); }
755 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
756 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
757
758 void mangle_unused_area();
759 void mangle_region(MemRegion mr);
760
761 // Size computations: sizes in bytes.
762 size_t capacity() const { return byte_size(bottom(), end()); }
763 size_t used() const { return byte_size(bottom(), top()); }
764 size_t free() const { return byte_size(top(), end()); }
765
766 // Override from space.
767 bool is_in(const void* p) const;
768
769 virtual bool is_free_block(const HeapWord* p) const;
770
771 // In a contiguous space we have a more obvious bound on what parts
772 // contain objects.
773 MemRegion used_region() const { return MemRegion(bottom(), top()); }
774
775 MemRegion used_region_at_save_marks() const {
776 return MemRegion(bottom(), saved_mark_word());
777 }
778
779 // Allocation (return NULL if full)
780 virtual HeapWord* allocate(size_t word_size);
781 virtual HeapWord* par_allocate(size_t word_size);
782
783 virtual bool obj_allocated_since_save_marks(const oop obj) const {
784 return (HeapWord*)obj >= saved_mark_word();
785 }
786
787 // Iteration
788 void oop_iterate(OopClosure* cl);
789 void oop_iterate(MemRegion mr, OopClosure* cl);
790 void object_iterate(ObjectClosure* blk);
791 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
792 // iterates on objects up to the safe limit
793 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
794 inline HeapWord* concurrent_iteration_safe_limit();
795 // changes the safe limit, all objects from bottom() to the new
796 // limit should be properly initialized
797 inline void set_concurrent_iteration_safe_limit(HeapWord* new_limit);
798
799 #ifndef SERIALGC
800 // In support of parallel oop_iterate.
801 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
802 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
803
804 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
805 #undef ContigSpace_PAR_OOP_ITERATE_DECL
806 #endif // SERIALGC
807
808 // Compaction support
809 virtual void reset_after_compaction() {
810 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
811 set_top(compaction_top());
812 // set new iteration safe limit
813 set_concurrent_iteration_safe_limit(compaction_top());
814 }
815 virtual size_t minimum_free_block_size() const { return 0; }
816
817 // Override.
818 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
819 CardTableModRefBS::PrecisionStyle precision,
820 HeapWord* boundary = NULL);
821
822 // Apply "blk->do_oop" to the addresses of all reference fields in objects
823 // starting with the _saved_mark_word, which was noted during a generation's
824 // save_marks and is required to denote the head of an object.
825 // Fields in objects allocated by applications of the closure
826 // *are* included in the iteration.
827 // Updates _saved_mark_word to point to just after the last object
828 // iterated over.
829 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
830 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
831
832 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
833 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
834
835 // Same as object_iterate, but starting from "mark", which is required
836 // to denote the start of an object. Objects allocated by
837 // applications of the closure *are* included in the iteration.
838 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
839
840 // Very inefficient implementation.
841 virtual HeapWord* block_start(const void* p) const;
842 size_t block_size(const HeapWord* p) const;
843 // If a block is in the allocated area, it is an object.
844 bool block_is_obj(const HeapWord* p) const { return p < top(); }
845
846 // Addresses for inlined allocation
847 HeapWord** top_addr() { return &_top; }
848 HeapWord** end_addr() { return &_end; }
849
850 // Overrides for more efficient compaction support.
851 void prepare_for_compaction(CompactPoint* cp);
852
853 // PrintHeapAtGC support.
854 virtual void print_on(outputStream* st) const;
855
856 // Checked dynamic downcasts.
857 virtual ContiguousSpace* toContiguousSpace() {
858 return this;
859 }
860
861 // Debugging
862 virtual void verify(bool allow_dirty) const;
863
864 // Used to increase collection frequency. "factor" of 0 means entire
865 // space.
866 void allocate_temporary_filler(int factor);
867
868 };
869
870
871 // A dirty card to oop closure that does filtering.
872 // It knows how to filter out objects that are outside of the _boundary.
873 class Filtering_DCTOC : public DirtyCardToOopClosure {
874 protected:
875 // Override.
876 void walk_mem_region(MemRegion mr,
877 HeapWord* bottom, HeapWord* top);
878
879 // Walk the given memory region, from bottom to top, applying
880 // the given oop closure to (possibly) all objects found. The
881 // given oop closure may or may not be the same as the oop
882 // closure with which this closure was created, as it may
883 // be a filtering closure which makes use of the _boundary.
884 // We offer two signatures, so the FilteringClosure static type is
885 // apparent.
886 virtual void walk_mem_region_with_cl(MemRegion mr,
887 HeapWord* bottom, HeapWord* top,
888 OopClosure* cl) = 0;
889 virtual void walk_mem_region_with_cl(MemRegion mr,
890 HeapWord* bottom, HeapWord* top,
891 FilteringClosure* cl) = 0;
892
893 public:
894 Filtering_DCTOC(Space* sp, OopClosure* cl,
895 CardTableModRefBS::PrecisionStyle precision,
896 HeapWord* boundary) :
897 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
898 };
899
900 // A dirty card to oop closure for contiguous spaces
901 // (ContiguousSpace and sub-classes).
902 // It is a FilteringClosure, as defined above, and it knows:
903 //
904 // 1. That the actual top of any area in a memory region
905 // contained by the space is bounded by the end of the contiguous
906 // region of the space.
907 // 2. That the space is really made up of objects and not just
908 // blocks.
909
910 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
911 protected:
912 // Overrides.
913 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
914
915 virtual void walk_mem_region_with_cl(MemRegion mr,
916 HeapWord* bottom, HeapWord* top,
917 OopClosure* cl);
918 virtual void walk_mem_region_with_cl(MemRegion mr,
919 HeapWord* bottom, HeapWord* top,
920 FilteringClosure* cl);
921
922 public:
923 ContiguousSpaceDCTOC(ContiguousSpace* sp, OopClosure* cl,
924 CardTableModRefBS::PrecisionStyle precision,
925 HeapWord* boundary) :
926 Filtering_DCTOC(sp, cl, precision, boundary)
927 {}
928 };
929
930
931 // Class EdenSpace describes eden-space in new generation.
932
933 class DefNewGeneration;
934
935 class EdenSpace : public ContiguousSpace {
936 friend class VMStructs;
937 private:
938 DefNewGeneration* _gen;
939
940 // _soft_end is used as a soft limit on allocation. As soft limits are
941 // reached, the slow-path allocation code can invoke other actions and then
942 // adjust _soft_end up to a new soft limit or to end().
943 HeapWord* _soft_end;
944
945 public:
946 EdenSpace(DefNewGeneration* gen) : _gen(gen) { _soft_end = NULL; }
947
948 // Get/set just the 'soft' limit.
949 HeapWord* soft_end() { return _soft_end; }
950 HeapWord** soft_end_addr() { return &_soft_end; }
951 void set_soft_end(HeapWord* value) { _soft_end = value; }
952
953 // Override.
954 void clear();
955
956 // Set both the 'hard' and 'soft' limits (_end and _soft_end).
957 void set_end(HeapWord* value) {
958 set_soft_end(value);
959 ContiguousSpace::set_end(value);
960 }
961
962 // Allocation (return NULL if full)
963 HeapWord* allocate(size_t word_size);
964 HeapWord* par_allocate(size_t word_size);
965 };
966
967 // Class ConcEdenSpace extends EdenSpace for the sake of safe
968 // allocation while soft-end is being modified concurrently
969
970 class ConcEdenSpace : public EdenSpace {
971 public:
972 ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
973
974 // Allocation (return NULL if full)
975 HeapWord* par_allocate(size_t word_size);
976 };
977
978
979 // A ContigSpace that Supports an efficient "block_start" operation via
980 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
981 // other spaces.) This is the abstract base class for old generation
982 // (tenured, perm) spaces.
983
984 class OffsetTableContigSpace: public ContiguousSpace {
985 friend class VMStructs;
986 protected:
987 BlockOffsetArrayContigSpace _offsets;
988 Mutex _par_alloc_lock;
989
990 public:
991 // Constructor
992 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
993 MemRegion mr);
994
995 void set_bottom(HeapWord* value);
996 void set_end(HeapWord* value);
997
998 void clear();
999
1000 inline HeapWord* block_start(const void* p) const;
1001
1002 // Add offset table update.
1003 virtual inline HeapWord* allocate(size_t word_size);
1004 inline HeapWord* par_allocate(size_t word_size);
1005
1006 // MarkSweep support phase3
1007 virtual HeapWord* initialize_threshold();
1008 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
1009
1010 virtual void print_on(outputStream* st) const;
1011
1012 // Debugging
1013 void verify(bool allow_dirty) const;
1014
1015 // Shared space support
1016 void serialize_block_offset_array_offsets(SerializeOopClosure* soc);
1017 };
1018
1019
1020 // Class TenuredSpace is used by TenuredGeneration
1021
1022 class TenuredSpace: public OffsetTableContigSpace {
1023 friend class VMStructs;
1024 protected:
1025 // Mark sweep support
1026 int allowed_dead_ratio() const;
1027 public:
1028 // Constructor
1029 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
1030 MemRegion mr) :
1031 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1032 };
1033
1034
1035 // Class ContigPermSpace is used by CompactingPermGen
1036
1037 class ContigPermSpace: public OffsetTableContigSpace {
1038 friend class VMStructs;
1039 protected:
1040 // Mark sweep support
1041 int allowed_dead_ratio() const;
1042 public:
1043 // Constructor
1044 ContigPermSpace(BlockOffsetSharedArray* sharedOffsetArray, MemRegion mr) :
1045 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1046 };