1 #ifdef USE_PRAGMA_IDENT_HDR
2 #pragma ident "@(#)space.hpp 1.149 07/05/29 09:44:14 JVM"
3 #endif
4 /*
5 * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 // A space is an abstraction for the "storage units" backing
29 // up the generation abstraction. It includes specific
30 // implementations for keeping track of free and used space,
31 // for iterating over objects and free blocks, etc.
32
33 // Here's the Space hierarchy:
34 //
35 // - Space -- an asbtract base class describing a heap area
36 // - CompactibleSpace -- a space supporting compaction
37 // - CompactibleFreeListSpace -- (used for CMS generation)
38 // - ContiguousSpace -- a compactible space in which all free space
39 // is contiguous
40 // - EdenSpace -- contiguous space used as nursery
41 // - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation
42 // - OffsetTableContigSpace -- contiguous space with a block offset array
43 // that allows "fast" block_start calls
44 // - TenuredSpace -- (used for TenuredGeneration)
45 // - ContigPermSpace -- an offset table contiguous space for perm gen
46
47 // Forward decls.
48 class Space;
49 class BlockOffsetArray;
50 class BlockOffsetArrayContigSpace;
51 class Generation;
52 class CompactibleSpace;
53 class BlockOffsetTable;
54 class GenRemSet;
55 class CardTableRS;
56 class DirtyCardToOopClosure;
57
58
59 // An oop closure that is circumscribed by a filtering memory region.
60 class SpaceMemRegionOopsIterClosure: public virtual OopClosure {
61 OopClosure* cl;
62 MemRegion mr;
63 public:
64 void do_oop(oop* p) {
65 if (mr.contains(p)) {
66 cl->do_oop(p);
67 }
68 }
69 SpaceMemRegionOopsIterClosure(OopClosure* _cl, MemRegion _mr): cl(_cl), mr(_mr) {}
70 };
71
72
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.
81
82 class Space: public CHeapObj {
83 friend class VMStructs;
84 protected:
85 HeapWord* _bottom;
86 HeapWord* _end;
87
88 // Used in support of save_marks()
89 HeapWord* _saved_mark_word;
90
91 MemRegionClosure* _preconsumptionDirtyCardClosure;
92
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;
97
98 Space():
99 _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { }
100
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; }
107
108 HeapWord* saved_mark_word() const { return _saved_mark_word; }
109 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
110
111 MemRegionClosure* preconsumptionDirtyCardClosure() const {
112 return _preconsumptionDirtyCardClosure;
113 }
114 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
115 _preconsumptionDirtyCardClosure = cl;
116 }
117
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()); }
121
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 }
133
134 // Initialization
135 virtual void initialize(MemRegion mr, bool clear_space);
136 virtual void clear();
137
138 // For detecting GC bugs. Should only be called at GC boundaries, since
139 // some unused space may be used as scratch space during GC's.
140 // Default implementation does nothing. We also call this when expanding
141 // a space to satisfy an allocation request. See bug #4668531
142 virtual void mangle_unused_area() {}
143 virtual void mangle_region(MemRegion mr) {}
144
145 // Testers
146 bool is_empty() const { return used() == 0; }
147 bool not_empty() const { return used() > 0; }
148
149 // Returns true iff the given the space contains the
150 // given address as part of an allocated object. For
151 // ceratin kinds of spaces, this might be a potentially
152 // expensive operation. To prevent performance problems
153 // on account of its inadvertent use in product jvm's,
154 // we restrict its use to assertion checks only.
155 virtual bool is_in(const void* p) const;
156
157 // Returns true iff the given reserved memory of the space contains the
158 // given address.
159 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
160
161 // Returns true iff the given block is not allocated.
162 virtual bool is_free_block(const HeapWord* p) const = 0;
163
164 // Test whether p is double-aligned
165 static bool is_aligned(void* p) {
166 return ((intptr_t)p & (sizeof(double)-1)) == 0;
167 }
168
169 // Size computations. Sizes are in bytes.
170 size_t capacity() const { return byte_size(bottom(), end()); }
171 virtual size_t used() const = 0;
172 virtual size_t free() const = 0;
173
174 // Iterate over all the ref-containing fields of all objects in the
175 // space, calling "cl.do_oop" on each. Fields in objects allocated by
176 // applications of the closure are not included in the iteration.
177 virtual void oop_iterate(OopClosure* cl);
178
179 // Same as above, restricted to the intersection of a memory region and
180 // the space. Fields in objects allocated by applications of the closure
181 // are not included in the iteration.
182 virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0;
183
184 // Iterate over all objects in the space, calling "cl.do_object" on
185 // each. Objects allocated by applications of the closure are not
186 // included in the iteration.
187 virtual void object_iterate(ObjectClosure* blk) = 0;
188
189 // Iterate over all objects that intersect with mr, calling "cl->do_object"
190 // on each. There is an exception to this: if this closure has already
191 // been invoked on an object, it may skip such objects in some cases. This is
192 // Most likely to happen in an "upwards" (ascending address) iteration of
193 // MemRegions.
194 virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
195
196 // Iterate over as many initialized objects in the space as possible,
197 // calling "cl.do_object_careful" on each. Return NULL if all objects
198 // in the space (at the start of the iteration) were iterated over.
199 // Return an address indicating the extent of the iteration in the
200 // event that the iteration had to return because of finding an
201 // uninitialized object in the space, or if the closure "cl"
202 // signalled early termination.
203 virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
204 virtual HeapWord* object_iterate_careful_m(MemRegion mr,
205 ObjectClosureCareful* cl);
206
207 // Create and return a new dirty card to oop closure. Can be
208 // overriden to return the appropriate type of closure
209 // depending on the type of space in which the closure will
210 // operate. ResourceArea allocated.
211 virtual DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
212 CardTableModRefBS::PrecisionStyle precision,
213 HeapWord* boundary = NULL);
214
215 // If "p" is in the space, returns the address of the start of the
216 // "block" that contains "p". We say "block" instead of "object" since
217 // some heaps may not pack objects densely; a chunk may either be an
218 // object or a non-object. If "p" is not in the space, return NULL.
219 virtual HeapWord* block_start(const void* p) const = 0;
220
221 // Requires "addr" to be the start of a chunk, and returns its size.
222 // "addr + size" is required to be the start of a new chunk, or the end
223 // of the active area of the heap.
224 virtual size_t block_size(const HeapWord* addr) const = 0;
225
226 // Requires "addr" to be the start of a block, and returns "TRUE" iff
227 // the block is an object.
228 virtual bool block_is_obj(const HeapWord* addr) const = 0;
229
230 // Requires "addr" to be the start of a block, and returns "TRUE" iff
231 // the block is an object and the object is alive.
232 virtual bool obj_is_alive(const HeapWord* addr) const;
233
234 // Allocation (return NULL if full). Assumes the caller has established
235 // mutually exclusive access to the space.
236 virtual HeapWord* allocate(size_t word_size) = 0;
237
238 // Allocation (return NULL if full). Enforces mutual exclusion internally.
239 virtual HeapWord* par_allocate(size_t word_size) = 0;
240
241 // Returns true if this object has been allocated since a
242 // generation's "save_marks" call.
243 virtual bool obj_allocated_since_save_marks(const oop obj) const = 0;
244
245 // Mark-sweep-compact support: all spaces can update pointers to objects
246 // moving as a part of compaction.
247 virtual void adjust_pointers();
248
249 // PrintHeapAtGC support
250 virtual void print() const;
251 virtual void print_on(outputStream* st) const;
252 virtual void print_short() const;
253 virtual void print_short_on(outputStream* st) const;
254
255
256 // Accessor for parallel sequential tasks.
257 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
258
259 // IF "this" is a ContiguousSpace, return it, else return NULL.
260 virtual ContiguousSpace* toContiguousSpace() {
261 return NULL;
262 }
263
264 // Debugging
265 virtual void verify(bool allow_dirty) const = 0;
266 };
267
268 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
269 // OopClosure to (the addresses of) all the ref-containing fields that could
270 // be modified by virtue of the given MemRegion being dirty. (Note that
271 // because of the imprecise nature of the write barrier, this may iterate
272 // over oops beyond the region.)
273 // This base type for dirty card to oop closures handles memory regions
274 // in non-contiguous spaces with no boundaries, and should be sub-classed
275 // to support other space types. See ContiguousDCTOC for a sub-class
276 // that works with ContiguousSpaces.
277
278 class DirtyCardToOopClosure: public MemRegionClosureRO {
279 protected:
280 OopClosure* _cl;
281 Space* _sp;
282 CardTableModRefBS::PrecisionStyle _precision;
283 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
284 // pointing below boundary.
285 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
286 // a downwards traversal; this is the
287 // lowest location already done (or,
288 // alternatively, the lowest address that
289 // shouldn't be done again. NULL means infinity.)
290 NOT_PRODUCT(HeapWord* _last_bottom;)
291
292 // Get the actual top of the area on which the closure will
293 // operate, given where the top is assumed to be (the end of the
294 // memory region passed to do_MemRegion) and where the object
295 // at the top is assumed to start. For example, an object may
296 // start at the top but actually extend past the assumed top,
297 // in which case the top becomes the end of the object.
298 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
299
300 // Walk the given memory region from bottom to (actual) top
301 // looking for objects and applying the oop closure (_cl) to
302 // them. The base implementation of this treats the area as
303 // blocks, where a block may or may not be an object. Sub-
304 // classes should override this to provide more accurate
305 // or possibly more efficient walking.
306 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
307
308 public:
309 DirtyCardToOopClosure(Space* sp, OopClosure* cl,
310 CardTableModRefBS::PrecisionStyle precision,
311 HeapWord* boundary) :
312 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
313 _min_done(NULL) {
314 NOT_PRODUCT(_last_bottom = NULL;)
315 }
316
317 void do_MemRegion(MemRegion mr);
318
319 void set_min_done(HeapWord* min_done) {
320 _min_done = min_done;
321 }
322 #ifndef PRODUCT
323 void set_last_bottom(HeapWord* last_bottom) {
324 _last_bottom = last_bottom;
325 }
326 #endif
327 };
328
329 // A structure to represent a point at which objects are being copied
330 // during compaction.
331 class CompactPoint : public StackObj {
332 public:
333 Generation* gen;
334 CompactibleSpace* space;
335 HeapWord* threshold;
336 CompactPoint(Generation* _gen, CompactibleSpace* _space,
337 HeapWord* _threshold) :
338 gen(_gen), space(_space), threshold(_threshold) {}
339 };
340
341
342 // A space that supports compaction operations. This is usually, but not
343 // necessarily, a space that is normally contiguous. But, for example, a
344 // free-list-based space whose normal collection is a mark-sweep without
345 // compaction could still support compaction in full GC's.
346
347 class CompactibleSpace: public Space {
348 friend class VMStructs;
349 friend class CompactibleFreeListSpace;
350 friend class CompactingPermGenGen;
351 friend class CMSPermGenGen;
352 private:
353 HeapWord* _compaction_top;
354 CompactibleSpace* _next_compaction_space;
355
356 public:
357 virtual void initialize(MemRegion mr, bool clear_space);
358
359 // Used temporarily during a compaction phase to hold the value
360 // top should have when compaction is complete.
361 HeapWord* compaction_top() const { return _compaction_top; }
362
363 void set_compaction_top(HeapWord* value) {
364 assert(value == NULL || (value >= bottom() && value <= end()),
365 "should point inside space");
366 _compaction_top = value;
367 }
368
369 // Perform operations on the space needed after a compaction
370 // has been performed.
371 virtual void reset_after_compaction() {}
372
373 // Returns the next space (in the current generation) to be compacted in
374 // the global compaction order. Also is used to select the next
375 // space into which to compact.
376
377 virtual CompactibleSpace* next_compaction_space() const {
378 return _next_compaction_space;
379 }
380
381 void set_next_compaction_space(CompactibleSpace* csp) {
382 _next_compaction_space = csp;
383 }
384
385 // MarkSweep support phase2
386
387 // Start the process of compaction of the current space: compute
388 // post-compaction addresses, and insert forwarding pointers. The fields
389 // "cp->gen" and "cp->compaction_space" are the generation and space into
390 // which we are currently compacting. This call updates "cp" as necessary,
391 // and leaves the "compaction_top" of the final value of
392 // "cp->compaction_space" up-to-date. Offset tables may be updated in
393 // this phase as if the final copy had occurred; if so, "cp->threshold"
394 // indicates when the next such action should be taken.
395 virtual void prepare_for_compaction(CompactPoint* cp);
396 // MarkSweep support phase3
397 virtual void adjust_pointers();
398 // MarkSweep support phase4
399 virtual void compact();
400
401 // The maximum percentage of objects that can be dead in the compacted
402 // live part of a compacted space ("deadwood" support.)
403 virtual int allowed_dead_ratio() const { return 0; };
404
405 // Some contiguous spaces may maintain some data structures that should
406 // be updated whenever an allocation crosses a boundary. This function
407 // returns the first such boundary.
408 // (The default implementation returns the end of the space, so the
409 // boundary is never crossed.)
410 virtual HeapWord* initialize_threshold() { return end(); }
411
412 // "q" is an object of the given "size" that should be forwarded;
413 // "cp" names the generation ("gen") and containing "this" (which must
414 // also equal "cp->space"). "compact_top" is where in "this" the
415 // next object should be forwarded to. If there is room in "this" for
416 // the object, insert an appropriate forwarding pointer in "q".
417 // If not, go to the next compaction space (there must
418 // be one, since compaction must succeed -- we go to the first space of
419 // the previous generation if necessary, updating "cp"), reset compact_top
420 // and then forward. In either case, returns the new value of "compact_top".
421 // If the forwarding crosses "cp->threshold", invokes the "cross_threhold"
422 // function of the then-current compaction space, and updates "cp->threshold
423 // accordingly".
424 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
425 HeapWord* compact_top);
426
427 // Return a size with adjusments as required of the space.
428 virtual size_t adjust_object_size_v(size_t size) const { return size; }
429
430 protected:
431 // Used during compaction.
432 HeapWord* _first_dead;
433 HeapWord* _end_of_live;
434
435 // Minimum size of a free block.
436 virtual size_t minimum_free_block_size() const = 0;
437
438 // This the function is invoked when an allocation of an object covering
439 // "start" to "end occurs crosses the threshold; returns the next
440 // threshold. (The default implementation does nothing.)
441 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
442 return end();
443 }
444
445 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
446 // free block of the given "word_len", and that "q", were it an object,
447 // would not move if forwared. If the size allows, fill the free
448 // block with an object, to prevent excessive compaction. Returns "true"
449 // iff the free region was made deadspace, and modifies
450 // "allowed_deadspace_words" to reflect the number of available deadspace
451 // words remaining after this operation.
452 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
453 size_t word_len);
454 };
455
456 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) { \
457 /* Compute the new addresses for the live objects and store it in the mark \
458 * Used by universe::mark_sweep_phase2() \
459 */ \
460 HeapWord* compact_top; /* This is where we are currently compacting to. */ \
461 \
462 /* We're sure to be here before any objects are compacted into this \
463 * space, so this is a good time to initialize this: \
464 */ \
465 set_compaction_top(bottom()); \
466 \
467 if (cp->space == NULL) { \
468 assert(cp->gen != NULL, "need a generation"); \
469 assert(cp->threshold == NULL, "just checking"); \
470 assert(cp->gen->first_compaction_space() == this, "just checking"); \
471 cp->space = cp->gen->first_compaction_space(); \
472 compact_top = cp->space->bottom(); \
473 cp->space->set_compaction_top(compact_top); \
474 cp->threshold = cp->space->initialize_threshold(); \
475 } else { \
476 compact_top = cp->space->compaction_top(); \
477 } \
478 \
479 /* We allow some amount of garbage towards the bottom of the space, so \
480 * we don't start compacting before there is a significant gain to be made.\
481 * Occasionally, we want to ensure a full compaction, which is determined \
482 * by the MarkSweepAlwaysCompactCount parameter. \
483 */ \
484 int invocations = SharedHeap::heap()->perm_gen()->stat_record()->invocations;\
485 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0); \
486 \
487 size_t allowed_deadspace = 0; \
488 if (skip_dead) { \
489 int ratio = allowed_dead_ratio(); \
490 allowed_deadspace = (capacity() * ratio / 100) / HeapWordSize; \
491 } \
492 \
493 HeapWord* q = bottom(); \
494 HeapWord* t = scan_limit(); \
495 \
496 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last \
497 live object. */ \
498 HeapWord* first_dead = end();/* The first dead object. */ \
499 LiveRange* liveRange = NULL; /* The current live range, recorded in the \
500 first header of preceding free area. */ \
501 _first_dead = first_dead; \
502 \
503 const intx interval = PrefetchScanIntervalInBytes; \
504 \
505 while (q < t) { \
506 assert(!block_is_obj(q) || \
507 oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() || \
508 oop(q)->mark()->has_bias_pattern(), \
509 "these are the only valid states during a mark sweep"); \
510 if (block_is_obj(q) && oop(q)->is_gc_marked()) { \
511 /* prefetch beyond q */ \
512 Prefetch::write(q, interval); \
513 /* size_t size = oop(q)->size(); changing this for cms for perm gen */\
514 size_t size = block_size(q); \
515 compact_top = cp->space->forward(oop(q), size, cp, compact_top); \
516 q += size; \
517 end_of_live = q; \
518 } else { \
519 /* run over all the contiguous dead objects */ \
520 HeapWord* end = q; \
521 do { \
522 /* prefetch beyond end */ \
523 Prefetch::write(end, interval); \
524 end += block_size(end); \
525 } while (end < t && (!block_is_obj(end) || !oop(end)->is_gc_marked()));\
526 \
527 /* see if we might want to pretend this object is alive so that \
528 * we don't have to compact quite as often. \
529 */ \
530 if (allowed_deadspace > 0 && q == compact_top) { \
531 size_t sz = pointer_delta(end, q); \
532 if (insert_deadspace(allowed_deadspace, q, sz)) { \
533 compact_top = cp->space->forward(oop(q), sz, cp, compact_top); \
534 q = end; \
535 end_of_live = end; \
536 continue; \
537 } \
538 } \
539 \
540 /* otherwise, it really is a free region. */ \
541 \
542 /* for the previous LiveRange, record the end of the live objects. */ \
543 if (liveRange) { \
544 liveRange->set_end(q); \
545 } \
546 \
547 /* record the current LiveRange object. \
548 * liveRange->start() is overlaid on the mark word. \
549 */ \
550 liveRange = (LiveRange*)q; \
551 liveRange->set_start(end); \
552 liveRange->set_end(end); \
553 \
554 /* see if this is the first dead region. */ \
555 if (q < first_dead) { \
556 first_dead = q; \
557 } \
558 \
559 /* move on to the next object */ \
560 q = end; \
561 } \
562 } \
563 \
564 assert(q == t, "just checking"); \
565 if (liveRange != NULL) { \
566 liveRange->set_end(q); \
567 } \
568 _end_of_live = end_of_live; \
569 if (end_of_live < first_dead) { \
570 first_dead = end_of_live; \
571 } \
572 _first_dead = first_dead; \
573 \
574 /* save the compaction_top of the compaction space. */ \
575 cp->space->set_compaction_top(compact_top); \
576 }
577
578 #define SCAN_AND_ADJUST_POINTERS(adjust_obj_size) { \
579 /* adjust all the interior pointers to point at the new locations of objects \
580 * Used by MarkSweep::mark_sweep_phase3() */ \
581 \
582 HeapWord* q = bottom(); \
583 HeapWord* t = _end_of_live; /* Established by "prepare_for_compaction". */ \
584 \
585 assert(_first_dead <= _end_of_live, "Stands to reason, no?"); \
586 \
587 if (q < t && _first_dead > q && \
588 !oop(q)->is_gc_marked()) { \
589 /* we have a chunk of the space which hasn't moved and we've \
590 * reinitialized the mark word during the previous pass, so we can't \
591 * use is_gc_marked for the traversal. */ \
592 HeapWord* end = _first_dead; \
593 \
594 while (q < end) { \
595 /* I originally tried to conjoin "block_start(q) == q" to the \
596 * assertion below, but that doesn't work, because you can't \
597 * accurately traverse previous objects to get to the current one \
598 * after their pointers (including pointers into permGen) have been \
599 * updated, until the actual compaction is done. dld, 4/00 */ \
600 assert(block_is_obj(q), \
601 "should be at block boundaries, and should be looking at objs"); \
602 \
603 debug_only(MarkSweep::track_interior_pointers(oop(q))); \
604 \
605 /* point all the oops to the new location */ \
606 size_t size = oop(q)->adjust_pointers(); \
607 size = adjust_obj_size(size); \
608 \
609 debug_only(MarkSweep::check_interior_pointers()); \
610 \
611 debug_only(MarkSweep::validate_live_oop(oop(q), size)); \
612 \
613 q += size; \
614 } \
615 \
616 if (_first_dead == t) { \
617 q = t; \
618 } else { \
619 /* $$$ This is funky. Using this to read the previously written \
620 * LiveRange. See also use below. */ \
621 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer(); \
622 } \
623 } \
624 \
625 const intx interval = PrefetchScanIntervalInBytes; \
626 \
627 debug_only(HeapWord* prev_q = NULL); \
628 while (q < t) { \
629 /* prefetch beyond q */ \
630 Prefetch::write(q, interval); \
631 if (oop(q)->is_gc_marked()) { \
632 /* q is alive */ \
633 debug_only(MarkSweep::track_interior_pointers(oop(q))); \
634 /* point all the oops to the new location */ \
635 size_t size = oop(q)->adjust_pointers(); \
636 size = adjust_obj_size(size); \
637 debug_only(MarkSweep::check_interior_pointers()); \
638 debug_only(MarkSweep::validate_live_oop(oop(q), size)); \
639 debug_only(prev_q = q); \
640 q += size; \
641 } else { \
642 /* q is not a live object, so its mark should point at the next \
643 * live object */ \
644 debug_only(prev_q = q); \
645 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
646 assert(q > prev_q, "we should be moving forward through memory"); \
647 } \
648 } \
649 \
650 assert(q == t, "just checking"); \
651 }
652
653 #define SCAN_AND_COMPACT(obj_size) { \
654 /* Copy all live objects to their new location \
655 * Used by MarkSweep::mark_sweep_phase4() */ \
656 \
657 HeapWord* q = bottom(); \
658 HeapWord* const t = _end_of_live; \
659 debug_only(HeapWord* prev_q = NULL); \
660 \
661 if (q < t && _first_dead > q && \
662 !oop(q)->is_gc_marked()) { \
663 debug_only( \
664 /* we have a chunk of the space which hasn't moved and we've reinitialized the \
665 * mark word during the previous pass, so we can't use is_gc_marked for the \
666 * traversal. */ \
667 HeapWord* const end = _first_dead; \
668 \
669 while (q < end) { \
670 size_t size = obj_size(q); \
671 assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)"); \
672 debug_only(MarkSweep::live_oop_moved_to(q, size, q)); \
673 debug_only(prev_q = q); \
674 q += size; \
675 } \
676 ) /* debug_only */ \
677 \
678 if (_first_dead == t) { \
679 q = t; \
680 } else { \
681 /* $$$ Funky */ \
682 q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer(); \
683 } \
684 } \
685 \
686 const intx scan_interval = PrefetchScanIntervalInBytes; \
687 const intx copy_interval = PrefetchCopyIntervalInBytes; \
688 while (q < t) { \
689 if (!oop(q)->is_gc_marked()) { \
690 /* mark is pointer to next marked oop */ \
691 debug_only(prev_q = q); \
692 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
693 assert(q > prev_q, "we should be moving forward through memory"); \
694 } else { \
695 /* prefetch beyond q */ \
696 Prefetch::read(q, scan_interval); \
697 \
698 /* size and destination */ \
699 size_t size = obj_size(q); \
700 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee(); \
701 \
702 /* prefetch beyond compaction_top */ \
703 Prefetch::write(compaction_top, copy_interval); \
704 \
705 /* copy object and reinit its mark */ \
706 debug_only(MarkSweep::live_oop_moved_to(q, size, compaction_top)); \
707 assert(q != compaction_top, "everything in this pass should be moving"); \
708 Copy::aligned_conjoint_words(q, compaction_top, size); \
709 oop(compaction_top)->init_mark(); \
710 assert(oop(compaction_top)->klass() != NULL, "should have a class"); \
711 \
712 debug_only(prev_q = q); \
713 q += size; \
714 } \
715 } \
716 \
717 /* Reset space after compaction is complete */ \
718 reset_after_compaction(); \
719 /* We do this clear, below, since it has overloaded meanings for some */ \
720 /* space subtypes. For example, OffsetTableContigSpace's that were */ \
721 /* compacted into will have had their offset table thresholds updated */ \
722 /* continuously, but those that weren't need to have their thresholds */ \
723 /* re-initialized. Also mangles unused area for debugging. */ \
724 if (is_empty()) { \
725 clear(); \
726 } else { \
727 if (ZapUnusedHeapArea) mangle_unused_area(); \
728 } \
729 }
730
731 // A space in which the free area is contiguous. It therefore supports
732 // faster allocation, and compaction.
733 class ContiguousSpace: public CompactibleSpace {
734 friend class OneContigSpaceCardGeneration;
735 friend class VMStructs;
736 protected:
737 HeapWord* _top;
738 HeapWord* _concurrent_iteration_safe_limit;
739
740 // Allocation helpers (return NULL if full).
741 inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
742 inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
743
744 public:
745 virtual void initialize(MemRegion mr, bool clear_space);
746
747 // Accessors
748 HeapWord* top() const { return _top; }
749 void set_top(HeapWord* value) { _top = value; }
750
751 void set_saved_mark() { _saved_mark_word = top(); }
752 void reset_saved_mark() { _saved_mark_word = bottom(); }
753
754 virtual void clear();
755
756 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
757 WaterMark top_mark() { return WaterMark(this, top()); }
758 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
759 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
760
761 void mangle_unused_area();
762 void mangle_region(MemRegion mr);
763
764 // Size computations: sizes in bytes.
765 size_t capacity() const { return byte_size(bottom(), end()); }
766 size_t used() const { return byte_size(bottom(), top()); }
767 size_t free() const { return byte_size(top(), end()); }
768
769 // Override from space.
770 bool is_in(const void* p) const;
771
772 virtual bool is_free_block(const HeapWord* p) const;
773
774 // In a contiguous space we have a more obvious bound on what parts
775 // contain objects.
776 MemRegion used_region() const { return MemRegion(bottom(), top()); }
777
778 MemRegion used_region_at_save_marks() const {
779 return MemRegion(bottom(), saved_mark_word());
780 }
781
782 // Allocation (return NULL if full)
783 virtual HeapWord* allocate(size_t word_size);
784 virtual HeapWord* par_allocate(size_t word_size);
785
786 virtual bool obj_allocated_since_save_marks(const oop obj) const {
787 return (HeapWord*)obj >= saved_mark_word();
788 }
789
790 // Iteration
791 void oop_iterate(OopClosure* cl);
792 void oop_iterate(MemRegion mr, OopClosure* cl);
793 void object_iterate(ObjectClosure* blk);
794 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
795 // iterates on objects up to the safe limit
796 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
797 inline HeapWord* concurrent_iteration_safe_limit();
798 // changes the safe limit, all objects from bottom() to the new
799 // limit should be properly initialized
800 inline void set_concurrent_iteration_safe_limit(HeapWord* new_limit);
801
802 #ifndef SERIALGC
803 // In support of parallel oop_iterate.
804 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
805 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
806
807 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
808 #undef ContigSpace_PAR_OOP_ITERATE_DECL
809 #endif // SERIALGC
810
811 // Compaction support
812 virtual void reset_after_compaction() {
813 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
814 set_top(compaction_top());
815 // set new iteration safe limit
816 set_concurrent_iteration_safe_limit(compaction_top());
817 }
818 virtual size_t minimum_free_block_size() const { return 0; }
819
820 // Override.
821 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
822 CardTableModRefBS::PrecisionStyle precision,
823 HeapWord* boundary = NULL);
824
825 // Apply "blk->do_oop" to the addresses of all reference fields in objects
826 // starting with the _saved_mark_word, which was noted during a generation's
827 // save_marks and is required to denote the head of an object.
828 // Fields in objects allocated by applications of the closure
829 // *are* included in the iteration.
830 // Updates _saved_mark_word to point to just after the last object
831 // iterated over.
832 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
833 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
834
835 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
836 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
837
838 // Same as object_iterate, but starting from "mark", which is required
839 // to denote the start of an object. Objects allocated by
840 // applications of the closure *are* included in the iteration.
841 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
842
843 // Very inefficient implementation.
844 virtual HeapWord* block_start(const void* p) const;
845 size_t block_size(const HeapWord* p) const;
846 // If a block is in the allocated area, it is an object.
847 bool block_is_obj(const HeapWord* p) const { return p < top(); }
848
849 // Addresses for inlined allocation
850 HeapWord** top_addr() { return &_top; }
851 HeapWord** end_addr() { return &_end; }
852
853 // Overrides for more efficient compaction support.
854 void prepare_for_compaction(CompactPoint* cp);
855
856 // PrintHeapAtGC support.
857 virtual void print_on(outputStream* st) const;
858
859 // Checked dynamic downcasts.
860 virtual ContiguousSpace* toContiguousSpace() {
861 return this;
862 }
863
864 // Debugging
865 virtual void verify(bool allow_dirty) const;
866
867 // Used to increase collection frequency. "factor" of 0 means entire
868 // space.
869 void allocate_temporary_filler(int factor);
870
871 };
872
873
874 // A dirty card to oop closure that does filtering.
875 // It knows how to filter out objects that are outside of the _boundary.
876 class Filtering_DCTOC : public DirtyCardToOopClosure {
877 protected:
878 // Override.
879 void walk_mem_region(MemRegion mr,
880 HeapWord* bottom, HeapWord* top);
881
882 // Walk the given memory region, from bottom to top, applying
883 // the given oop closure to (possibly) all objects found. The
884 // given oop closure may or may not be the same as the oop
885 // closure with which this closure was created, as it may
886 // be a filtering closure which makes use of the _boundary.
887 // We offer two signatures, so the FilteringClosure static type is
888 // apparent.
889 virtual void walk_mem_region_with_cl(MemRegion mr,
890 HeapWord* bottom, HeapWord* top,
891 OopClosure* cl) = 0;
892 virtual void walk_mem_region_with_cl(MemRegion mr,
893 HeapWord* bottom, HeapWord* top,
894 FilteringClosure* cl) = 0;
895
896 public:
897 Filtering_DCTOC(Space* sp, OopClosure* cl,
898 CardTableModRefBS::PrecisionStyle precision,
899 HeapWord* boundary) :
900 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
901 };
902
903 // A dirty card to oop closure for contiguous spaces
904 // (ContiguousSpace and sub-classes).
905 // It is a FilteringClosure, as defined above, and it knows:
906 //
907 // 1. That the actual top of any area in a memory region
908 // contained by the space is bounded by the end of the contiguous
909 // region of the space.
910 // 2. That the space is really made up of objects and not just
911 // blocks.
912
913 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
914 protected:
915 // Overrides.
916 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
917
918 virtual void walk_mem_region_with_cl(MemRegion mr,
919 HeapWord* bottom, HeapWord* top,
920 OopClosure* cl);
921 virtual void walk_mem_region_with_cl(MemRegion mr,
922 HeapWord* bottom, HeapWord* top,
923 FilteringClosure* cl);
924
925 public:
926 ContiguousSpaceDCTOC(ContiguousSpace* sp, OopClosure* cl,
927 CardTableModRefBS::PrecisionStyle precision,
928 HeapWord* boundary) :
929 Filtering_DCTOC(sp, cl, precision, boundary)
930 {}
931 };
932
933
934 // Class EdenSpace describes eden-space in new generation.
935
936 class DefNewGeneration;
937
938 class EdenSpace : public ContiguousSpace {
939 friend class VMStructs;
940 private:
941 DefNewGeneration* _gen;
942
943 // _soft_end is used as a soft limit on allocation. As soft limits are
944 // reached, the slow-path allocation code can invoke other actions and then
945 // adjust _soft_end up to a new soft limit or to end().
946 HeapWord* _soft_end;
947
948 public:
949 EdenSpace(DefNewGeneration* gen) : _gen(gen) { _soft_end = NULL; }
950
951 // Get/set just the 'soft' limit.
952 HeapWord* soft_end() { return _soft_end; }
953 HeapWord** soft_end_addr() { return &_soft_end; }
954 void set_soft_end(HeapWord* value) { _soft_end = value; }
955
956 // Override.
957 void clear();
958
959 // Set both the 'hard' and 'soft' limits (_end and _soft_end).
960 void set_end(HeapWord* value) {
961 set_soft_end(value);
962 ContiguousSpace::set_end(value);
963 }
964
965 // Allocation (return NULL if full)
966 HeapWord* allocate(size_t word_size);
967 HeapWord* par_allocate(size_t word_size);
968 };
969
970 // Class ConcEdenSpace extends EdenSpace for the sake of safe
971 // allocation while soft-end is being modified concurrently
972
973 class ConcEdenSpace : public EdenSpace {
974 public:
975 ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
976
977 // Allocation (return NULL if full)
978 HeapWord* par_allocate(size_t word_size);
979 };
980
981
982 // A ContigSpace that Supports an efficient "block_start" operation via
983 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
984 // other spaces.) This is the abstract base class for old generation
985 // (tenured, perm) spaces.
986
987 class OffsetTableContigSpace: public ContiguousSpace {
988 friend class VMStructs;
989 protected:
990 BlockOffsetArrayContigSpace _offsets;
991 Mutex _par_alloc_lock;
992
993 public:
994 // Constructor
995 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
996 MemRegion mr);
997
998 void set_bottom(HeapWord* value);
999 void set_end(HeapWord* value);
1000
1001 void clear();
1002
1003 inline HeapWord* block_start(const void* p) const;
1004
1005 // Add offset table update.
1006 virtual inline HeapWord* allocate(size_t word_size);
1007 inline HeapWord* par_allocate(size_t word_size);
1008
1009 // MarkSweep support phase3
1010 virtual HeapWord* initialize_threshold();
1011 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
1012
1013 virtual void print_on(outputStream* st) const;
1014
1015 // Debugging
1016 void verify(bool allow_dirty) const;
1017
1018 // Shared space support
1019 void serialize_block_offset_array_offsets(SerializeOopClosure* soc);
1020 };
1021
1022
1023 // Class TenuredSpace is used by TenuredGeneration
1024
1025 class TenuredSpace: public OffsetTableContigSpace {
1026 friend class VMStructs;
1027 protected:
1028 // Mark sweep support
1029 int allowed_dead_ratio() const;
1030 public:
1031 // Constructor
1032 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
1033 MemRegion mr) :
1034 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1035 };
1036
1037
1038 // Class ContigPermSpace is used by CompactingPermGen
1039
1040 class ContigPermSpace: public OffsetTableContigSpace {
1041 friend class VMStructs;
1042 protected:
1043 // Mark sweep support
1044 int allowed_dead_ratio() const;
1045 public:
1046 // Constructor
1047 ContigPermSpace(BlockOffsetSharedArray* sharedOffsetArray, MemRegion mr) :
1048 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1049 };