1 /*
2 * Copyright (c) 1997, 2009, Oracle and/or its affiliates. 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,
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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 // 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 };
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 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
109
110 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
111
112 MemRegionClosure* preconsumptionDirtyCardClosure() const {
113 return _preconsumptionDirtyCardClosure;
114 }
115 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
116 _preconsumptionDirtyCardClosure = cl;
117 }
118
119 // Returns a subregion of the space containing all the objects in
120 // the space.
121 virtual MemRegion used_region() const { return MemRegion(bottom(), end()); }
122
123 // Returns a region that is guaranteed to contain (at least) all objects
124 // allocated at the time of the last call to "save_marks". If the space
125 // initializes its DirtyCardToOopClosure's specifying the "contig" option
126 // (that is, if the space is contiguous), then this region must contain only
127 // such objects: the memregion will be from the bottom of the region to the
128 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
129 // the space must distiguish between objects in the region allocated before
130 // and after the call to save marks.
131 virtual MemRegion used_region_at_save_marks() const {
132 return MemRegion(bottom(), saved_mark_word());
133 }
134
135 // Initialization.
136 // "initialize" should be called once on a space, before it is used for
137 // any purpose. The "mr" arguments gives the bounds of the space, and
138 // the "clear_space" argument should be true unless the memory in "mr" is
139 // known to be zeroed.
140 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
141
142 // The "clear" method must be called on a region that may have
143 // had allocation performed in it, but is now to be considered empty.
144 virtual void clear(bool mangle_space);
145
146 // For detecting GC bugs. Should only be called at GC boundaries, since
147 // some unused space may be used as scratch space during GC's.
148 // Default implementation does nothing. We also call this when expanding
149 // a space to satisfy an allocation request. See bug #4668531
150 virtual void mangle_unused_area() {}
151 virtual void mangle_unused_area_complete() {}
152 virtual void mangle_region(MemRegion mr) {}
153
154 // Testers
155 bool is_empty() const { return used() == 0; }
156 bool not_empty() const { return used() > 0; }
157
158 // Returns true iff the given the space contains the
159 // given address as part of an allocated object. For
160 // ceratin kinds of spaces, this might be a potentially
161 // expensive operation. To prevent performance problems
162 // on account of its inadvertent use in product jvm's,
163 // we restrict its use to assertion checks only.
164 virtual bool is_in(const void* p) const;
165
166 // Returns true iff the given reserved memory of the space contains the
167 // given address.
168 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
169
170 // Returns true iff the given block is not allocated.
171 virtual bool is_free_block(const HeapWord* p) const = 0;
172
173 // Test whether p is double-aligned
174 static bool is_aligned(void* p) {
175 return ((intptr_t)p & (sizeof(double)-1)) == 0;
176 }
177
178 // Size computations. Sizes are in bytes.
179 size_t capacity() const { return byte_size(bottom(), end()); }
180 virtual size_t used() const = 0;
181 virtual size_t free() const = 0;
182
183 // Iterate over all the ref-containing fields of all objects in the
184 // space, calling "cl.do_oop" on each. Fields in objects allocated by
185 // applications of the closure are not included in the iteration.
186 virtual void oop_iterate(OopClosure* cl);
187
188 // Same as above, restricted to the intersection of a memory region and
189 // the space. Fields in objects allocated by applications of the closure
190 // are not included in the iteration.
191 virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0;
192
193 // Iterate over all objects in the space, calling "cl.do_object" on
194 // each. Objects allocated by applications of the closure are not
195 // included in the iteration.
196 virtual void object_iterate(ObjectClosure* blk) = 0;
197 // Similar to object_iterate() except only iterates over
198 // objects whose internal references point to objects in the space.
199 virtual void safe_object_iterate(ObjectClosure* blk) = 0;
200
201 // Iterate over all objects that intersect with mr, calling "cl->do_object"
202 // on each. There is an exception to this: if this closure has already
203 // been invoked on an object, it may skip such objects in some cases. This is
204 // Most likely to happen in an "upwards" (ascending address) iteration of
205 // MemRegions.
206 virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
207
208 // Iterate over as many initialized objects in the space as possible,
209 // calling "cl.do_object_careful" on each. Return NULL if all objects
210 // in the space (at the start of the iteration) were iterated over.
211 // Return an address indicating the extent of the iteration in the
212 // event that the iteration had to return because of finding an
213 // uninitialized object in the space, or if the closure "cl"
214 // signalled early termination.
215 virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
216 virtual HeapWord* object_iterate_careful_m(MemRegion mr,
217 ObjectClosureCareful* cl);
218
219 // Create and return a new dirty card to oop closure. Can be
220 // overriden to return the appropriate type of closure
221 // depending on the type of space in which the closure will
222 // operate. ResourceArea allocated.
223 virtual DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
224 CardTableModRefBS::PrecisionStyle precision,
225 HeapWord* boundary = NULL);
226
227 // If "p" is in the space, returns the address of the start of the
228 // "block" that contains "p". We say "block" instead of "object" since
229 // some heaps may not pack objects densely; a chunk may either be an
230 // object or a non-object. If "p" is not in the space, return NULL.
231 virtual HeapWord* block_start_const(const void* p) const = 0;
232
233 // The non-const version may have benevolent side effects on the data
234 // structure supporting these calls, possibly speeding up future calls.
235 // The default implementation, however, is simply to call the const
236 // version.
237 inline virtual HeapWord* block_start(const void* p);
238
239 // Requires "addr" to be the start of a chunk, and returns its size.
240 // "addr + size" is required to be the start of a new chunk, or the end
241 // of the active area of the heap.
242 virtual size_t block_size(const HeapWord* addr) const = 0;
243
244 // Requires "addr" to be the start of a block, and returns "TRUE" iff
245 // the block is an object.
246 virtual bool block_is_obj(const HeapWord* addr) const = 0;
247
248 // Requires "addr" to be the start of a block, and returns "TRUE" iff
249 // the block is an object and the object is alive.
250 virtual bool obj_is_alive(const HeapWord* addr) const;
251
252 // Allocation (return NULL if full). Assumes the caller has established
253 // mutually exclusive access to the space.
254 virtual HeapWord* allocate(size_t word_size) = 0;
255
256 // Allocation (return NULL if full). Enforces mutual exclusion internally.
257 virtual HeapWord* par_allocate(size_t word_size) = 0;
258
259 // Returns true if this object has been allocated since a
260 // generation's "save_marks" call.
261 virtual bool obj_allocated_since_save_marks(const oop obj) const = 0;
262
263 // Mark-sweep-compact support: all spaces can update pointers to objects
264 // moving as a part of compaction.
265 virtual void adjust_pointers();
266
267 // PrintHeapAtGC support
268 virtual void print() const;
269 virtual void print_on(outputStream* st) const;
270 virtual void print_short() const;
271 virtual void print_short_on(outputStream* st) const;
272
273
274 // Accessor for parallel sequential tasks.
275 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
276
277 // IF "this" is a ContiguousSpace, return it, else return NULL.
278 virtual ContiguousSpace* toContiguousSpace() {
279 return NULL;
280 }
281
282 // Debugging
283 virtual void verify(bool allow_dirty) const = 0;
284 };
285
286 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
287 // OopClosure to (the addresses of) all the ref-containing fields that could
288 // be modified by virtue of the given MemRegion being dirty. (Note that
289 // because of the imprecise nature of the write barrier, this may iterate
290 // over oops beyond the region.)
291 // This base type for dirty card to oop closures handles memory regions
292 // in non-contiguous spaces with no boundaries, and should be sub-classed
293 // to support other space types. See ContiguousDCTOC for a sub-class
294 // that works with ContiguousSpaces.
295
296 class DirtyCardToOopClosure: public MemRegionClosureRO {
297 protected:
298 OopClosure* _cl;
299 Space* _sp;
300 CardTableModRefBS::PrecisionStyle _precision;
301 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
302 // pointing below boundary.
303 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
304 // a downwards traversal; this is the
305 // lowest location already done (or,
306 // alternatively, the lowest address that
307 // shouldn't be done again. NULL means infinity.)
308 NOT_PRODUCT(HeapWord* _last_bottom;)
309 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
310
311 // Get the actual top of the area on which the closure will
312 // operate, given where the top is assumed to be (the end of the
313 // memory region passed to do_MemRegion) and where the object
314 // at the top is assumed to start. For example, an object may
315 // start at the top but actually extend past the assumed top,
316 // in which case the top becomes the end of the object.
317 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
318
319 // Walk the given memory region from bottom to (actual) top
320 // looking for objects and applying the oop closure (_cl) to
321 // them. The base implementation of this treats the area as
322 // blocks, where a block may or may not be an object. Sub-
323 // classes should override this to provide more accurate
324 // or possibly more efficient walking.
325 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
326
327 public:
328 DirtyCardToOopClosure(Space* sp, OopClosure* cl,
329 CardTableModRefBS::PrecisionStyle precision,
330 HeapWord* boundary) :
331 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
332 _min_done(NULL) {
333 NOT_PRODUCT(_last_bottom = NULL);
334 NOT_PRODUCT(_last_explicit_min_done = NULL);
335 }
336
337 void do_MemRegion(MemRegion mr);
338
339 void set_min_done(HeapWord* min_done) {
340 _min_done = min_done;
341 NOT_PRODUCT(_last_explicit_min_done = _min_done);
342 }
343 #ifndef PRODUCT
344 void set_last_bottom(HeapWord* last_bottom) {
345 _last_bottom = last_bottom;
346 }
347 #endif
348 };
349
350 // A structure to represent a point at which objects are being copied
351 // during compaction.
352 class CompactPoint : public StackObj {
353 public:
354 Generation* gen;
355 CompactibleSpace* space;
356 HeapWord* threshold;
357 CompactPoint(Generation* _gen, CompactibleSpace* _space,
358 HeapWord* _threshold) :
359 gen(_gen), space(_space), threshold(_threshold) {}
360 };
361
362
363 // A space that supports compaction operations. This is usually, but not
364 // necessarily, a space that is normally contiguous. But, for example, a
365 // free-list-based space whose normal collection is a mark-sweep without
366 // compaction could still support compaction in full GC's.
367
368 class CompactibleSpace: public Space {
369 friend class VMStructs;
370 friend class CompactibleFreeListSpace;
371 friend class CompactingPermGenGen;
372 friend class CMSPermGenGen;
373 private:
374 HeapWord* _compaction_top;
375 CompactibleSpace* _next_compaction_space;
376
377 public:
378 CompactibleSpace() :
379 _compaction_top(NULL), _next_compaction_space(NULL) {}
380
381 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
382 virtual void clear(bool mangle_space);
383
384 // Used temporarily during a compaction phase to hold the value
385 // top should have when compaction is complete.
386 HeapWord* compaction_top() const { return _compaction_top; }
387
388 void set_compaction_top(HeapWord* value) {
389 assert(value == NULL || (value >= bottom() && value <= end()),
390 "should point inside space");
391 _compaction_top = value;
392 }
393
394 // Perform operations on the space needed after a compaction
395 // has been performed.
396 virtual void reset_after_compaction() {}
397
398 // Returns the next space (in the current generation) to be compacted in
399 // the global compaction order. Also is used to select the next
400 // space into which to compact.
401
402 virtual CompactibleSpace* next_compaction_space() const {
403 return _next_compaction_space;
404 }
405
406 void set_next_compaction_space(CompactibleSpace* csp) {
407 _next_compaction_space = csp;
408 }
409
410 // MarkSweep support phase2
411
412 // Start the process of compaction of the current space: compute
413 // post-compaction addresses, and insert forwarding pointers. The fields
414 // "cp->gen" and "cp->compaction_space" are the generation and space into
415 // which we are currently compacting. This call updates "cp" as necessary,
416 // and leaves the "compaction_top" of the final value of
417 // "cp->compaction_space" up-to-date. Offset tables may be updated in
418 // this phase as if the final copy had occurred; if so, "cp->threshold"
419 // indicates when the next such action should be taken.
420 virtual void prepare_for_compaction(CompactPoint* cp);
421 // MarkSweep support phase3
422 virtual void adjust_pointers();
423 // MarkSweep support phase4
424 virtual void compact();
425
426 // The maximum percentage of objects that can be dead in the compacted
427 // live part of a compacted space ("deadwood" support.)
428 virtual size_t allowed_dead_ratio() const { return 0; };
429
430 // Some contiguous spaces may maintain some data structures that should
431 // be updated whenever an allocation crosses a boundary. This function
432 // returns the first such boundary.
433 // (The default implementation returns the end of the space, so the
434 // boundary is never crossed.)
435 virtual HeapWord* initialize_threshold() { return end(); }
436
437 // "q" is an object of the given "size" that should be forwarded;
438 // "cp" names the generation ("gen") and containing "this" (which must
439 // also equal "cp->space"). "compact_top" is where in "this" the
440 // next object should be forwarded to. If there is room in "this" for
441 // the object, insert an appropriate forwarding pointer in "q".
442 // If not, go to the next compaction space (there must
443 // be one, since compaction must succeed -- we go to the first space of
444 // the previous generation if necessary, updating "cp"), reset compact_top
445 // and then forward. In either case, returns the new value of "compact_top".
446 // If the forwarding crosses "cp->threshold", invokes the "cross_threhold"
447 // function of the then-current compaction space, and updates "cp->threshold
448 // accordingly".
449 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
450 HeapWord* compact_top);
451
452 // Return a size with adjusments as required of the space.
453 virtual size_t adjust_object_size_v(size_t size) const { return size; }
454
455 protected:
456 // Used during compaction.
457 HeapWord* _first_dead;
458 HeapWord* _end_of_live;
459
460 // Minimum size of a free block.
461 virtual size_t minimum_free_block_size() const = 0;
462
463 // This the function is invoked when an allocation of an object covering
464 // "start" to "end occurs crosses the threshold; returns the next
465 // threshold. (The default implementation does nothing.)
466 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
467 return end();
468 }
469
470 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
471 // free block of the given "word_len", and that "q", were it an object,
472 // would not move if forwared. If the size allows, fill the free
473 // block with an object, to prevent excessive compaction. Returns "true"
474 // iff the free region was made deadspace, and modifies
475 // "allowed_deadspace_words" to reflect the number of available deadspace
476 // words remaining after this operation.
477 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
478 size_t word_len);
479 };
480
481 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) { \
482 /* Compute the new addresses for the live objects and store it in the mark \
483 * Used by universe::mark_sweep_phase2() \
484 */ \
485 HeapWord* compact_top; /* This is where we are currently compacting to. */ \
486 \
487 /* We're sure to be here before any objects are compacted into this \
488 * space, so this is a good time to initialize this: \
489 */ \
490 set_compaction_top(bottom()); \
491 \
492 if (cp->space == NULL) { \
493 assert(cp->gen != NULL, "need a generation"); \
494 assert(cp->threshold == NULL, "just checking"); \
495 assert(cp->gen->first_compaction_space() == this, "just checking"); \
496 cp->space = cp->gen->first_compaction_space(); \
497 compact_top = cp->space->bottom(); \
498 cp->space->set_compaction_top(compact_top); \
499 cp->threshold = cp->space->initialize_threshold(); \
500 } else { \
501 compact_top = cp->space->compaction_top(); \
502 } \
503 \
504 /* We allow some amount of garbage towards the bottom of the space, so \
505 * we don't start compacting before there is a significant gain to be made.\
506 * Occasionally, we want to ensure a full compaction, which is determined \
507 * by the MarkSweepAlwaysCompactCount parameter. \
508 */ \
509 int invocations = SharedHeap::heap()->perm_gen()->stat_record()->invocations;\
510 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0); \
511 \
512 size_t allowed_deadspace = 0; \
513 if (skip_dead) { \
514 const size_t ratio = allowed_dead_ratio(); \
515 allowed_deadspace = (capacity() * ratio / 100) / HeapWordSize; \
516 } \
517 \
518 HeapWord* q = bottom(); \
519 HeapWord* t = scan_limit(); \
520 \
521 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last \
522 live object. */ \
523 HeapWord* first_dead = end();/* The first dead object. */ \
524 LiveRange* liveRange = NULL; /* The current live range, recorded in the \
525 first header of preceding free area. */ \
526 _first_dead = first_dead; \
527 \
528 const intx interval = PrefetchScanIntervalInBytes; \
529 \
530 while (q < t) { \
531 assert(!block_is_obj(q) || \
532 oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() || \
533 oop(q)->mark()->has_bias_pattern(), \
534 "these are the only valid states during a mark sweep"); \
535 if (block_is_obj(q) && oop(q)->is_gc_marked()) { \
536 /* prefetch beyond q */ \
537 Prefetch::write(q, interval); \
538 /* size_t size = oop(q)->size(); changing this for cms for perm gen */\
539 size_t size = block_size(q); \
540 compact_top = cp->space->forward(oop(q), size, cp, compact_top); \
541 q += size; \
542 end_of_live = q; \
543 } else { \
544 /* run over all the contiguous dead objects */ \
545 HeapWord* end = q; \
546 do { \
547 /* prefetch beyond end */ \
548 Prefetch::write(end, interval); \
549 end += block_size(end); \
550 } while (end < t && (!block_is_obj(end) || !oop(end)->is_gc_marked()));\
551 \
552 /* see if we might want to pretend this object is alive so that \
553 * we don't have to compact quite as often. \
554 */ \
555 if (allowed_deadspace > 0 && q == compact_top) { \
556 size_t sz = pointer_delta(end, q); \
557 if (insert_deadspace(allowed_deadspace, q, sz)) { \
558 compact_top = cp->space->forward(oop(q), sz, cp, compact_top); \
559 q = end; \
560 end_of_live = end; \
561 continue; \
562 } \
563 } \
564 \
565 /* otherwise, it really is a free region. */ \
566 \
567 /* for the previous LiveRange, record the end of the live objects. */ \
568 if (liveRange) { \
569 liveRange->set_end(q); \
570 } \
571 \
572 /* record the current LiveRange object. \
573 * liveRange->start() is overlaid on the mark word. \
574 */ \
575 liveRange = (LiveRange*)q; \
576 liveRange->set_start(end); \
577 liveRange->set_end(end); \
578 \
579 /* see if this is the first dead region. */ \
580 if (q < first_dead) { \
581 first_dead = q; \
582 } \
583 \
584 /* move on to the next object */ \
585 q = end; \
586 } \
587 } \
588 \
589 assert(q == t, "just checking"); \
590 if (liveRange != NULL) { \
591 liveRange->set_end(q); \
592 } \
593 _end_of_live = end_of_live; \
594 if (end_of_live < first_dead) { \
595 first_dead = end_of_live; \
596 } \
597 _first_dead = first_dead; \
598 \
599 /* save the compaction_top of the compaction space. */ \
600 cp->space->set_compaction_top(compact_top); \
601 }
602
603 #define SCAN_AND_ADJUST_POINTERS(adjust_obj_size) { \
604 /* adjust all the interior pointers to point at the new locations of objects \
605 * Used by MarkSweep::mark_sweep_phase3() */ \
606 \
607 HeapWord* q = bottom(); \
608 HeapWord* t = _end_of_live; /* Established by "prepare_for_compaction". */ \
609 \
610 assert(_first_dead <= _end_of_live, "Stands to reason, no?"); \
611 \
612 if (q < t && _first_dead > q && \
613 !oop(q)->is_gc_marked()) { \
614 /* we have a chunk of the space which hasn't moved and we've \
615 * reinitialized the mark word during the previous pass, so we can't \
616 * use is_gc_marked for the traversal. */ \
617 HeapWord* end = _first_dead; \
618 \
619 while (q < end) { \
620 /* I originally tried to conjoin "block_start(q) == q" to the \
621 * assertion below, but that doesn't work, because you can't \
622 * accurately traverse previous objects to get to the current one \
623 * after their pointers (including pointers into permGen) have been \
624 * updated, until the actual compaction is done. dld, 4/00 */ \
625 assert(block_is_obj(q), \
626 "should be at block boundaries, and should be looking at objs"); \
627 \
628 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q))); \
629 \
630 /* point all the oops to the new location */ \
631 size_t size = oop(q)->adjust_pointers(); \
632 size = adjust_obj_size(size); \
633 \
634 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers()); \
635 \
636 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size)); \
637 \
638 q += size; \
639 } \
640 \
641 if (_first_dead == t) { \
642 q = t; \
643 } else { \
644 /* $$$ This is funky. Using this to read the previously written \
645 * LiveRange. See also use below. */ \
646 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer(); \
647 } \
648 } \
649 \
650 const intx interval = PrefetchScanIntervalInBytes; \
651 \
652 debug_only(HeapWord* prev_q = NULL); \
653 while (q < t) { \
654 /* prefetch beyond q */ \
655 Prefetch::write(q, interval); \
656 if (oop(q)->is_gc_marked()) { \
657 /* q is alive */ \
658 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q))); \
659 /* point all the oops to the new location */ \
660 size_t size = oop(q)->adjust_pointers(); \
661 size = adjust_obj_size(size); \
662 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers()); \
663 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size)); \
664 debug_only(prev_q = q); \
665 q += size; \
666 } else { \
667 /* q is not a live object, so its mark should point at the next \
668 * live object */ \
669 debug_only(prev_q = q); \
670 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
671 assert(q > prev_q, "we should be moving forward through memory"); \
672 } \
673 } \
674 \
675 assert(q == t, "just checking"); \
676 }
677
678 #define SCAN_AND_COMPACT(obj_size) { \
679 /* Copy all live objects to their new location \
680 * Used by MarkSweep::mark_sweep_phase4() */ \
681 \
682 HeapWord* q = bottom(); \
683 HeapWord* const t = _end_of_live; \
684 debug_only(HeapWord* prev_q = NULL); \
685 \
686 if (q < t && _first_dead > q && \
687 !oop(q)->is_gc_marked()) { \
688 debug_only( \
689 /* we have a chunk of the space which hasn't moved and we've reinitialized \
690 * the mark word during the previous pass, so we can't use is_gc_marked for \
691 * the traversal. */ \
692 HeapWord* const end = _first_dead; \
693 \
694 while (q < end) { \
695 size_t size = obj_size(q); \
696 assert(!oop(q)->is_gc_marked(), \
697 "should be unmarked (special dense prefix handling)"); \
698 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, q)); \
699 debug_only(prev_q = q); \
700 q += size; \
701 } \
702 ) /* debug_only */ \
703 \
704 if (_first_dead == t) { \
705 q = t; \
706 } else { \
707 /* $$$ Funky */ \
708 q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer(); \
709 } \
710 } \
711 \
712 const intx scan_interval = PrefetchScanIntervalInBytes; \
713 const intx copy_interval = PrefetchCopyIntervalInBytes; \
714 while (q < t) { \
715 if (!oop(q)->is_gc_marked()) { \
716 /* mark is pointer to next marked oop */ \
717 debug_only(prev_q = q); \
718 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
719 assert(q > prev_q, "we should be moving forward through memory"); \
720 } else { \
721 /* prefetch beyond q */ \
722 Prefetch::read(q, scan_interval); \
723 \
724 /* size and destination */ \
725 size_t size = obj_size(q); \
726 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee(); \
727 \
728 /* prefetch beyond compaction_top */ \
729 Prefetch::write(compaction_top, copy_interval); \
730 \
731 /* copy object and reinit its mark */ \
732 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, \
733 compaction_top)); \
734 assert(q != compaction_top, "everything in this pass should be moving"); \
735 Copy::aligned_conjoint_words(q, compaction_top, size); \
736 oop(compaction_top)->init_mark(); \
737 assert(oop(compaction_top)->klass() != NULL, "should have a class"); \
738 \
739 debug_only(prev_q = q); \
740 q += size; \
741 } \
742 } \
743 \
744 /* Let's remember if we were empty before we did the compaction. */ \
745 bool was_empty = used_region().is_empty(); \
746 /* Reset space after compaction is complete */ \
747 reset_after_compaction(); \
748 /* We do this clear, below, since it has overloaded meanings for some */ \
749 /* space subtypes. For example, OffsetTableContigSpace's that were */ \
750 /* compacted into will have had their offset table thresholds updated */ \
751 /* continuously, but those that weren't need to have their thresholds */ \
752 /* re-initialized. Also mangles unused area for debugging. */ \
753 if (used_region().is_empty()) { \
754 if (!was_empty) clear(SpaceDecorator::Mangle); \
755 } else { \
756 if (ZapUnusedHeapArea) mangle_unused_area(); \
757 } \
758 }
759
760 class GenSpaceMangler;
761
762 // A space in which the free area is contiguous. It therefore supports
763 // faster allocation, and compaction.
764 class ContiguousSpace: public CompactibleSpace {
765 friend class OneContigSpaceCardGeneration;
766 friend class VMStructs;
767 protected:
768 HeapWord* _top;
769 HeapWord* _concurrent_iteration_safe_limit;
770 // A helper for mangling the unused area of the space in debug builds.
771 GenSpaceMangler* _mangler;
772
773 GenSpaceMangler* mangler() { return _mangler; }
774
775 // Allocation helpers (return NULL if full).
776 inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
777 inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
778
779 public:
780 ContiguousSpace();
781 ~ContiguousSpace();
782
783 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
784 virtual void clear(bool mangle_space);
785
786 // Accessors
787 HeapWord* top() const { return _top; }
788 void set_top(HeapWord* value) { _top = value; }
789
790 virtual void set_saved_mark() { _saved_mark_word = top(); }
791 void reset_saved_mark() { _saved_mark_word = bottom(); }
792
793 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
794 WaterMark top_mark() { return WaterMark(this, top()); }
795 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
796 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
797
798 // In debug mode mangle (write it with a particular bit
799 // pattern) the unused part of a space.
800
801 // Used to save the an address in a space for later use during mangling.
802 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
803 // Used to save the space's current top for later use during mangling.
804 void set_top_for_allocations() PRODUCT_RETURN;
805
806 // Mangle regions in the space from the current top up to the
807 // previously mangled part of the space.
808 void mangle_unused_area() PRODUCT_RETURN;
809 // Mangle [top, end)
810 void mangle_unused_area_complete() PRODUCT_RETURN;
811 // Mangle the given MemRegion.
812 void mangle_region(MemRegion mr) PRODUCT_RETURN;
813
814 // Do some sparse checking on the area that should have been mangled.
815 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
816 // Check the complete area that should have been mangled.
817 // This code may be NULL depending on the macro DEBUG_MANGLING.
818 void check_mangled_unused_area_complete() PRODUCT_RETURN;
819
820 // Size computations: sizes in bytes.
821 size_t capacity() const { return byte_size(bottom(), end()); }
822 size_t used() const { return byte_size(bottom(), top()); }
823 size_t free() const { return byte_size(top(), end()); }
824
825 // Override from space.
826 bool is_in(const void* p) const;
827
828 virtual bool is_free_block(const HeapWord* p) const;
829
830 // In a contiguous space we have a more obvious bound on what parts
831 // contain objects.
832 MemRegion used_region() const { return MemRegion(bottom(), top()); }
833
834 MemRegion used_region_at_save_marks() const {
835 return MemRegion(bottom(), saved_mark_word());
836 }
837
838 // Allocation (return NULL if full)
839 virtual HeapWord* allocate(size_t word_size);
840 virtual HeapWord* par_allocate(size_t word_size);
841
842 virtual bool obj_allocated_since_save_marks(const oop obj) const {
843 return (HeapWord*)obj >= saved_mark_word();
844 }
845
846 // Iteration
847 void oop_iterate(OopClosure* cl);
848 void oop_iterate(MemRegion mr, OopClosure* cl);
849 void object_iterate(ObjectClosure* blk);
850 // For contiguous spaces this method will iterate safely over objects
851 // in the space (i.e., between bottom and top) when at a safepoint.
852 void safe_object_iterate(ObjectClosure* blk);
853 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
854 // iterates on objects up to the safe limit
855 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
856 inline HeapWord* concurrent_iteration_safe_limit();
857 // changes the safe limit, all objects from bottom() to the new
858 // limit should be properly initialized
859 inline void set_concurrent_iteration_safe_limit(HeapWord* new_limit);
860
861 #ifndef SERIALGC
862 // In support of parallel oop_iterate.
863 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
864 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
865
866 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
867 #undef ContigSpace_PAR_OOP_ITERATE_DECL
868 #endif // SERIALGC
869
870 // Compaction support
871 virtual void reset_after_compaction() {
872 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
873 set_top(compaction_top());
874 // set new iteration safe limit
875 set_concurrent_iteration_safe_limit(compaction_top());
876 }
877 virtual size_t minimum_free_block_size() const { return 0; }
878
879 // Override.
880 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
881 CardTableModRefBS::PrecisionStyle precision,
882 HeapWord* boundary = NULL);
883
884 // Apply "blk->do_oop" to the addresses of all reference fields in objects
885 // starting with the _saved_mark_word, which was noted during a generation's
886 // save_marks and is required to denote the head of an object.
887 // Fields in objects allocated by applications of the closure
888 // *are* included in the iteration.
889 // Updates _saved_mark_word to point to just after the last object
890 // iterated over.
891 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
892 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
893
894 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
895 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
896
897 // Same as object_iterate, but starting from "mark", which is required
898 // to denote the start of an object. Objects allocated by
899 // applications of the closure *are* included in the iteration.
900 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
901
902 // Very inefficient implementation.
903 virtual HeapWord* block_start_const(const void* p) const;
904 size_t block_size(const HeapWord* p) const;
905 // If a block is in the allocated area, it is an object.
906 bool block_is_obj(const HeapWord* p) const { return p < top(); }
907
908 // Addresses for inlined allocation
909 HeapWord** top_addr() { return &_top; }
910 HeapWord** end_addr() { return &_end; }
911
912 // Overrides for more efficient compaction support.
913 void prepare_for_compaction(CompactPoint* cp);
914
915 // PrintHeapAtGC support.
916 virtual void print_on(outputStream* st) const;
917
918 // Checked dynamic downcasts.
919 virtual ContiguousSpace* toContiguousSpace() {
920 return this;
921 }
922
923 // Debugging
924 virtual void verify(bool allow_dirty) const;
925
926 // Used to increase collection frequency. "factor" of 0 means entire
927 // space.
928 void allocate_temporary_filler(int factor);
929
930 };
931
932
933 // A dirty card to oop closure that does filtering.
934 // It knows how to filter out objects that are outside of the _boundary.
935 class Filtering_DCTOC : public DirtyCardToOopClosure {
936 protected:
937 // Override.
938 void walk_mem_region(MemRegion mr,
939 HeapWord* bottom, HeapWord* top);
940
941 // Walk the given memory region, from bottom to top, applying
942 // the given oop closure to (possibly) all objects found. The
943 // given oop closure may or may not be the same as the oop
944 // closure with which this closure was created, as it may
945 // be a filtering closure which makes use of the _boundary.
946 // We offer two signatures, so the FilteringClosure static type is
947 // apparent.
948 virtual void walk_mem_region_with_cl(MemRegion mr,
949 HeapWord* bottom, HeapWord* top,
950 OopClosure* cl) = 0;
951 virtual void walk_mem_region_with_cl(MemRegion mr,
952 HeapWord* bottom, HeapWord* top,
953 FilteringClosure* cl) = 0;
954
955 public:
956 Filtering_DCTOC(Space* sp, OopClosure* cl,
957 CardTableModRefBS::PrecisionStyle precision,
958 HeapWord* boundary) :
959 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
960 };
961
962 // A dirty card to oop closure for contiguous spaces
963 // (ContiguousSpace and sub-classes).
964 // It is a FilteringClosure, as defined above, and it knows:
965 //
966 // 1. That the actual top of any area in a memory region
967 // contained by the space is bounded by the end of the contiguous
968 // region of the space.
969 // 2. That the space is really made up of objects and not just
970 // blocks.
971
972 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
973 protected:
974 // Overrides.
975 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
976
977 virtual void walk_mem_region_with_cl(MemRegion mr,
978 HeapWord* bottom, HeapWord* top,
979 OopClosure* cl);
980 virtual void walk_mem_region_with_cl(MemRegion mr,
981 HeapWord* bottom, HeapWord* top,
982 FilteringClosure* cl);
983
984 public:
985 ContiguousSpaceDCTOC(ContiguousSpace* sp, OopClosure* cl,
986 CardTableModRefBS::PrecisionStyle precision,
987 HeapWord* boundary) :
988 Filtering_DCTOC(sp, cl, precision, boundary)
989 {}
990 };
991
992
993 // Class EdenSpace describes eden-space in new generation.
994
995 class DefNewGeneration;
996
997 class EdenSpace : public ContiguousSpace {
998 friend class VMStructs;
999 private:
1000 DefNewGeneration* _gen;
1001
1002 // _soft_end is used as a soft limit on allocation. As soft limits are
1003 // reached, the slow-path allocation code can invoke other actions and then
1004 // adjust _soft_end up to a new soft limit or to end().
1005 HeapWord* _soft_end;
1006
1007 public:
1008 EdenSpace(DefNewGeneration* gen) :
1009 _gen(gen), _soft_end(NULL) {}
1010
1011 // Get/set just the 'soft' limit.
1012 HeapWord* soft_end() { return _soft_end; }
1013 HeapWord** soft_end_addr() { return &_soft_end; }
1014 void set_soft_end(HeapWord* value) { _soft_end = value; }
1015
1016 // Override.
1017 void clear(bool mangle_space);
1018
1019 // Set both the 'hard' and 'soft' limits (_end and _soft_end).
1020 void set_end(HeapWord* value) {
1021 set_soft_end(value);
1022 ContiguousSpace::set_end(value);
1023 }
1024
1025 // Allocation (return NULL if full)
1026 HeapWord* allocate(size_t word_size);
1027 HeapWord* par_allocate(size_t word_size);
1028 };
1029
1030 // Class ConcEdenSpace extends EdenSpace for the sake of safe
1031 // allocation while soft-end is being modified concurrently
1032
1033 class ConcEdenSpace : public EdenSpace {
1034 public:
1035 ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
1036
1037 // Allocation (return NULL if full)
1038 HeapWord* par_allocate(size_t word_size);
1039 };
1040
1041
1042 // A ContigSpace that Supports an efficient "block_start" operation via
1043 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
1044 // other spaces.) This is the abstract base class for old generation
1045 // (tenured, perm) spaces.
1046
1047 class OffsetTableContigSpace: public ContiguousSpace {
1048 friend class VMStructs;
1049 protected:
1050 BlockOffsetArrayContigSpace _offsets;
1051 Mutex _par_alloc_lock;
1052
1053 public:
1054 // Constructor
1055 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
1056 MemRegion mr);
1057
1058 void set_bottom(HeapWord* value);
1059 void set_end(HeapWord* value);
1060
1061 void clear(bool mangle_space);
1062
1063 inline HeapWord* block_start_const(const void* p) const;
1064
1065 // Add offset table update.
1066 virtual inline HeapWord* allocate(size_t word_size);
1067 inline HeapWord* par_allocate(size_t word_size);
1068
1069 // MarkSweep support phase3
1070 virtual HeapWord* initialize_threshold();
1071 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
1072
1073 virtual void print_on(outputStream* st) const;
1074
1075 // Debugging
1076 void verify(bool allow_dirty) const;
1077
1078 // Shared space support
1079 void serialize_block_offset_array_offsets(SerializeOopClosure* soc);
1080 };
1081
1082
1083 // Class TenuredSpace is used by TenuredGeneration
1084
1085 class TenuredSpace: public OffsetTableContigSpace {
1086 friend class VMStructs;
1087 protected:
1088 // Mark sweep support
1089 size_t allowed_dead_ratio() const;
1090 public:
1091 // Constructor
1092 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
1093 MemRegion mr) :
1094 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1095 };
1096
1097
1098 // Class ContigPermSpace is used by CompactingPermGen
1099
1100 class ContigPermSpace: public OffsetTableContigSpace {
1101 friend class VMStructs;
1102 protected:
1103 // Mark sweep support
1104 size_t allowed_dead_ratio() const;
1105 public:
1106 // Constructor
1107 ContigPermSpace(BlockOffsetSharedArray* sharedOffsetArray, MemRegion mr) :
1108 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1109 };