Thu, 24 Mar 2011 15:47:01 -0700
7029036: Card-table verification hangs with all framework collectors, except G1, even before the first GC
Summary: When verifying clean card ranges, use memory-range-bounded iteration over oops of objects overlapping that range, thus avoiding the otherwise quadratic worst-case cost of scanning large object arrays.
Reviewed-by: jmasa, jwilhelm, tonyp
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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25 #ifndef SHARE_VM_MEMORY_SPACE_HPP
26 #define SHARE_VM_MEMORY_SPACE_HPP
28 #include "memory/allocation.hpp"
29 #include "memory/blockOffsetTable.hpp"
30 #include "memory/cardTableModRefBS.hpp"
31 #include "memory/iterator.hpp"
32 #include "memory/memRegion.hpp"
33 #include "memory/watermark.hpp"
34 #include "oops/markOop.hpp"
35 #include "runtime/mutexLocker.hpp"
36 #include "runtime/prefetch.hpp"
37 #include "utilities/workgroup.hpp"
38 #ifdef TARGET_OS_FAMILY_linux
39 # include "os_linux.inline.hpp"
40 #endif
41 #ifdef TARGET_OS_FAMILY_solaris
42 # include "os_solaris.inline.hpp"
43 #endif
44 #ifdef TARGET_OS_FAMILY_windows
45 # include "os_windows.inline.hpp"
46 #endif
48 // A space is an abstraction for the "storage units" backing
49 // up the generation abstraction. It includes specific
50 // implementations for keeping track of free and used space,
51 // for iterating over objects and free blocks, etc.
53 // Here's the Space hierarchy:
54 //
55 // - Space -- an asbtract base class describing a heap area
56 // - CompactibleSpace -- a space supporting compaction
57 // - CompactibleFreeListSpace -- (used for CMS generation)
58 // - ContiguousSpace -- a compactible space in which all free space
59 // is contiguous
60 // - EdenSpace -- contiguous space used as nursery
61 // - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation
62 // - OffsetTableContigSpace -- contiguous space with a block offset array
63 // that allows "fast" block_start calls
64 // - TenuredSpace -- (used for TenuredGeneration)
65 // - ContigPermSpace -- an offset table contiguous space for perm gen
67 // Forward decls.
68 class Space;
69 class BlockOffsetArray;
70 class BlockOffsetArrayContigSpace;
71 class Generation;
72 class CompactibleSpace;
73 class BlockOffsetTable;
74 class GenRemSet;
75 class CardTableRS;
76 class DirtyCardToOopClosure;
78 // An oop closure that is circumscribed by a filtering memory region.
79 class SpaceMemRegionOopsIterClosure: public OopClosure {
80 private:
81 OopClosure* _cl;
82 MemRegion _mr;
83 protected:
84 template <class T> void do_oop_work(T* p) {
85 if (_mr.contains(p)) {
86 _cl->do_oop(p);
87 }
88 }
89 public:
90 SpaceMemRegionOopsIterClosure(OopClosure* cl, MemRegion mr):
91 _cl(cl), _mr(mr) {}
92 virtual void do_oop(oop* p);
93 virtual void do_oop(narrowOop* p);
94 };
96 // A Space describes a heap area. Class Space is an abstract
97 // base class.
98 //
99 // Space supports allocation, size computation and GC support is provided.
100 //
101 // Invariant: bottom() and end() are on page_size boundaries and
102 // bottom() <= top() <= end()
103 // top() is inclusive and end() is exclusive.
105 class Space: public CHeapObj {
106 friend class VMStructs;
107 protected:
108 HeapWord* _bottom;
109 HeapWord* _end;
111 // Used in support of save_marks()
112 HeapWord* _saved_mark_word;
114 MemRegionClosure* _preconsumptionDirtyCardClosure;
116 // A sequential tasks done structure. This supports
117 // parallel GC, where we have threads dynamically
118 // claiming sub-tasks from a larger parallel task.
119 SequentialSubTasksDone _par_seq_tasks;
121 Space():
122 _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { }
124 public:
125 // Accessors
126 HeapWord* bottom() const { return _bottom; }
127 HeapWord* end() const { return _end; }
128 virtual void set_bottom(HeapWord* value) { _bottom = value; }
129 virtual void set_end(HeapWord* value) { _end = value; }
131 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
133 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
135 MemRegionClosure* preconsumptionDirtyCardClosure() const {
136 return _preconsumptionDirtyCardClosure;
137 }
138 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
139 _preconsumptionDirtyCardClosure = cl;
140 }
142 // Returns a subregion of the space containing all the objects in
143 // the space.
144 virtual MemRegion used_region() const { return MemRegion(bottom(), end()); }
146 // Returns a region that is guaranteed to contain (at least) all objects
147 // allocated at the time of the last call to "save_marks". If the space
148 // initializes its DirtyCardToOopClosure's specifying the "contig" option
149 // (that is, if the space is contiguous), then this region must contain only
150 // such objects: the memregion will be from the bottom of the region to the
151 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
152 // the space must distiguish between objects in the region allocated before
153 // and after the call to save marks.
154 virtual MemRegion used_region_at_save_marks() const {
155 return MemRegion(bottom(), saved_mark_word());
156 }
158 // Initialization.
159 // "initialize" should be called once on a space, before it is used for
160 // any purpose. The "mr" arguments gives the bounds of the space, and
161 // the "clear_space" argument should be true unless the memory in "mr" is
162 // known to be zeroed.
163 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
165 // The "clear" method must be called on a region that may have
166 // had allocation performed in it, but is now to be considered empty.
167 virtual void clear(bool mangle_space);
169 // For detecting GC bugs. Should only be called at GC boundaries, since
170 // some unused space may be used as scratch space during GC's.
171 // Default implementation does nothing. We also call this when expanding
172 // a space to satisfy an allocation request. See bug #4668531
173 virtual void mangle_unused_area() {}
174 virtual void mangle_unused_area_complete() {}
175 virtual void mangle_region(MemRegion mr) {}
177 // Testers
178 bool is_empty() const { return used() == 0; }
179 bool not_empty() const { return used() > 0; }
181 // Returns true iff the given the space contains the
182 // given address as part of an allocated object. For
183 // ceratin kinds of spaces, this might be a potentially
184 // expensive operation. To prevent performance problems
185 // on account of its inadvertent use in product jvm's,
186 // we restrict its use to assertion checks only.
187 virtual bool is_in(const void* p) const;
189 // Returns true iff the given reserved memory of the space contains the
190 // given address.
191 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
193 // Returns true iff the given block is not allocated.
194 virtual bool is_free_block(const HeapWord* p) const = 0;
196 // Test whether p is double-aligned
197 static bool is_aligned(void* p) {
198 return ((intptr_t)p & (sizeof(double)-1)) == 0;
199 }
201 // Size computations. Sizes are in bytes.
202 size_t capacity() const { return byte_size(bottom(), end()); }
203 virtual size_t used() const = 0;
204 virtual size_t free() const = 0;
206 // Iterate over all the ref-containing fields of all objects in the
207 // space, calling "cl.do_oop" on each. Fields in objects allocated by
208 // applications of the closure are not included in the iteration.
209 virtual void oop_iterate(OopClosure* cl);
211 // Same as above, restricted to the intersection of a memory region and
212 // the space. Fields in objects allocated by applications of the closure
213 // are not included in the iteration.
214 virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0;
216 // Iterate over all objects in the space, calling "cl.do_object" on
217 // each. Objects allocated by applications of the closure are not
218 // included in the iteration.
219 virtual void object_iterate(ObjectClosure* blk) = 0;
220 // Similar to object_iterate() except only iterates over
221 // objects whose internal references point to objects in the space.
222 virtual void safe_object_iterate(ObjectClosure* blk) = 0;
224 // Iterate over all objects that intersect with mr, calling "cl->do_object"
225 // on each. There is an exception to this: if this closure has already
226 // been invoked on an object, it may skip such objects in some cases. This is
227 // Most likely to happen in an "upwards" (ascending address) iteration of
228 // MemRegions.
229 virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
231 // Iterate over as many initialized objects in the space as possible,
232 // calling "cl.do_object_careful" on each. Return NULL if all objects
233 // in the space (at the start of the iteration) were iterated over.
234 // Return an address indicating the extent of the iteration in the
235 // event that the iteration had to return because of finding an
236 // uninitialized object in the space, or if the closure "cl"
237 // signalled early termination.
238 virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
239 virtual HeapWord* object_iterate_careful_m(MemRegion mr,
240 ObjectClosureCareful* cl);
242 // Create and return a new dirty card to oop closure. Can be
243 // overriden to return the appropriate type of closure
244 // depending on the type of space in which the closure will
245 // operate. ResourceArea allocated.
246 virtual DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
247 CardTableModRefBS::PrecisionStyle precision,
248 HeapWord* boundary = NULL);
250 // If "p" is in the space, returns the address of the start of the
251 // "block" that contains "p". We say "block" instead of "object" since
252 // some heaps may not pack objects densely; a chunk may either be an
253 // object or a non-object. If "p" is not in the space, return NULL.
254 virtual HeapWord* block_start_const(const void* p) const = 0;
256 // The non-const version may have benevolent side effects on the data
257 // structure supporting these calls, possibly speeding up future calls.
258 // The default implementation, however, is simply to call the const
259 // version.
260 inline virtual HeapWord* block_start(const void* p);
262 // Requires "addr" to be the start of a chunk, and returns its size.
263 // "addr + size" is required to be the start of a new chunk, or the end
264 // of the active area of the heap.
265 virtual size_t block_size(const HeapWord* addr) const = 0;
267 // Requires "addr" to be the start of a block, and returns "TRUE" iff
268 // the block is an object.
269 virtual bool block_is_obj(const HeapWord* addr) const = 0;
271 // Requires "addr" to be the start of a block, and returns "TRUE" iff
272 // the block is an object and the object is alive.
273 virtual bool obj_is_alive(const HeapWord* addr) const;
275 // Allocation (return NULL if full). Assumes the caller has established
276 // mutually exclusive access to the space.
277 virtual HeapWord* allocate(size_t word_size) = 0;
279 // Allocation (return NULL if full). Enforces mutual exclusion internally.
280 virtual HeapWord* par_allocate(size_t word_size) = 0;
282 // Returns true if this object has been allocated since a
283 // generation's "save_marks" call.
284 virtual bool obj_allocated_since_save_marks(const oop obj) const = 0;
286 // Mark-sweep-compact support: all spaces can update pointers to objects
287 // moving as a part of compaction.
288 virtual void adjust_pointers();
290 // PrintHeapAtGC support
291 virtual void print() const;
292 virtual void print_on(outputStream* st) const;
293 virtual void print_short() const;
294 virtual void print_short_on(outputStream* st) const;
297 // Accessor for parallel sequential tasks.
298 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
300 // IF "this" is a ContiguousSpace, return it, else return NULL.
301 virtual ContiguousSpace* toContiguousSpace() {
302 return NULL;
303 }
305 // Debugging
306 virtual void verify(bool allow_dirty) const = 0;
307 };
309 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
310 // OopClosure to (the addresses of) all the ref-containing fields that could
311 // be modified by virtue of the given MemRegion being dirty. (Note that
312 // because of the imprecise nature of the write barrier, this may iterate
313 // over oops beyond the region.)
314 // This base type for dirty card to oop closures handles memory regions
315 // in non-contiguous spaces with no boundaries, and should be sub-classed
316 // to support other space types. See ContiguousDCTOC for a sub-class
317 // that works with ContiguousSpaces.
319 class DirtyCardToOopClosure: public MemRegionClosureRO {
320 protected:
321 OopClosure* _cl;
322 Space* _sp;
323 CardTableModRefBS::PrecisionStyle _precision;
324 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
325 // pointing below boundary.
326 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
327 // a downwards traversal; this is the
328 // lowest location already done (or,
329 // alternatively, the lowest address that
330 // shouldn't be done again. NULL means infinity.)
331 NOT_PRODUCT(HeapWord* _last_bottom;)
332 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
334 // Get the actual top of the area on which the closure will
335 // operate, given where the top is assumed to be (the end of the
336 // memory region passed to do_MemRegion) and where the object
337 // at the top is assumed to start. For example, an object may
338 // start at the top but actually extend past the assumed top,
339 // in which case the top becomes the end of the object.
340 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
342 // Walk the given memory region from bottom to (actual) top
343 // looking for objects and applying the oop closure (_cl) to
344 // them. The base implementation of this treats the area as
345 // blocks, where a block may or may not be an object. Sub-
346 // classes should override this to provide more accurate
347 // or possibly more efficient walking.
348 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
350 public:
351 DirtyCardToOopClosure(Space* sp, OopClosure* cl,
352 CardTableModRefBS::PrecisionStyle precision,
353 HeapWord* boundary) :
354 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
355 _min_done(NULL) {
356 NOT_PRODUCT(_last_bottom = NULL);
357 NOT_PRODUCT(_last_explicit_min_done = NULL);
358 }
360 void do_MemRegion(MemRegion mr);
362 void set_min_done(HeapWord* min_done) {
363 _min_done = min_done;
364 NOT_PRODUCT(_last_explicit_min_done = _min_done);
365 }
366 #ifndef PRODUCT
367 void set_last_bottom(HeapWord* last_bottom) {
368 _last_bottom = last_bottom;
369 }
370 #endif
371 };
373 // A structure to represent a point at which objects are being copied
374 // during compaction.
375 class CompactPoint : public StackObj {
376 public:
377 Generation* gen;
378 CompactibleSpace* space;
379 HeapWord* threshold;
380 CompactPoint(Generation* _gen, CompactibleSpace* _space,
381 HeapWord* _threshold) :
382 gen(_gen), space(_space), threshold(_threshold) {}
383 };
386 // A space that supports compaction operations. This is usually, but not
387 // necessarily, a space that is normally contiguous. But, for example, a
388 // free-list-based space whose normal collection is a mark-sweep without
389 // compaction could still support compaction in full GC's.
391 class CompactibleSpace: public Space {
392 friend class VMStructs;
393 friend class CompactibleFreeListSpace;
394 friend class CompactingPermGenGen;
395 friend class CMSPermGenGen;
396 private:
397 HeapWord* _compaction_top;
398 CompactibleSpace* _next_compaction_space;
400 public:
401 CompactibleSpace() :
402 _compaction_top(NULL), _next_compaction_space(NULL) {}
404 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
405 virtual void clear(bool mangle_space);
407 // Used temporarily during a compaction phase to hold the value
408 // top should have when compaction is complete.
409 HeapWord* compaction_top() const { return _compaction_top; }
411 void set_compaction_top(HeapWord* value) {
412 assert(value == NULL || (value >= bottom() && value <= end()),
413 "should point inside space");
414 _compaction_top = value;
415 }
417 // Perform operations on the space needed after a compaction
418 // has been performed.
419 virtual void reset_after_compaction() {}
421 // Returns the next space (in the current generation) to be compacted in
422 // the global compaction order. Also is used to select the next
423 // space into which to compact.
425 virtual CompactibleSpace* next_compaction_space() const {
426 return _next_compaction_space;
427 }
429 void set_next_compaction_space(CompactibleSpace* csp) {
430 _next_compaction_space = csp;
431 }
433 // MarkSweep support phase2
435 // Start the process of compaction of the current space: compute
436 // post-compaction addresses, and insert forwarding pointers. The fields
437 // "cp->gen" and "cp->compaction_space" are the generation and space into
438 // which we are currently compacting. This call updates "cp" as necessary,
439 // and leaves the "compaction_top" of the final value of
440 // "cp->compaction_space" up-to-date. Offset tables may be updated in
441 // this phase as if the final copy had occurred; if so, "cp->threshold"
442 // indicates when the next such action should be taken.
443 virtual void prepare_for_compaction(CompactPoint* cp);
444 // MarkSweep support phase3
445 virtual void adjust_pointers();
446 // MarkSweep support phase4
447 virtual void compact();
449 // The maximum percentage of objects that can be dead in the compacted
450 // live part of a compacted space ("deadwood" support.)
451 virtual size_t allowed_dead_ratio() const { return 0; };
453 // Some contiguous spaces may maintain some data structures that should
454 // be updated whenever an allocation crosses a boundary. This function
455 // returns the first such boundary.
456 // (The default implementation returns the end of the space, so the
457 // boundary is never crossed.)
458 virtual HeapWord* initialize_threshold() { return end(); }
460 // "q" is an object of the given "size" that should be forwarded;
461 // "cp" names the generation ("gen") and containing "this" (which must
462 // also equal "cp->space"). "compact_top" is where in "this" the
463 // next object should be forwarded to. If there is room in "this" for
464 // the object, insert an appropriate forwarding pointer in "q".
465 // If not, go to the next compaction space (there must
466 // be one, since compaction must succeed -- we go to the first space of
467 // the previous generation if necessary, updating "cp"), reset compact_top
468 // and then forward. In either case, returns the new value of "compact_top".
469 // If the forwarding crosses "cp->threshold", invokes the "cross_threhold"
470 // function of the then-current compaction space, and updates "cp->threshold
471 // accordingly".
472 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
473 HeapWord* compact_top);
475 // Return a size with adjusments as required of the space.
476 virtual size_t adjust_object_size_v(size_t size) const { return size; }
478 protected:
479 // Used during compaction.
480 HeapWord* _first_dead;
481 HeapWord* _end_of_live;
483 // Minimum size of a free block.
484 virtual size_t minimum_free_block_size() const = 0;
486 // This the function is invoked when an allocation of an object covering
487 // "start" to "end occurs crosses the threshold; returns the next
488 // threshold. (The default implementation does nothing.)
489 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
490 return end();
491 }
493 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
494 // free block of the given "word_len", and that "q", were it an object,
495 // would not move if forwared. If the size allows, fill the free
496 // block with an object, to prevent excessive compaction. Returns "true"
497 // iff the free region was made deadspace, and modifies
498 // "allowed_deadspace_words" to reflect the number of available deadspace
499 // words remaining after this operation.
500 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
501 size_t word_len);
502 };
504 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) { \
505 /* Compute the new addresses for the live objects and store it in the mark \
506 * Used by universe::mark_sweep_phase2() \
507 */ \
508 HeapWord* compact_top; /* This is where we are currently compacting to. */ \
509 \
510 /* We're sure to be here before any objects are compacted into this \
511 * space, so this is a good time to initialize this: \
512 */ \
513 set_compaction_top(bottom()); \
514 \
515 if (cp->space == NULL) { \
516 assert(cp->gen != NULL, "need a generation"); \
517 assert(cp->threshold == NULL, "just checking"); \
518 assert(cp->gen->first_compaction_space() == this, "just checking"); \
519 cp->space = cp->gen->first_compaction_space(); \
520 compact_top = cp->space->bottom(); \
521 cp->space->set_compaction_top(compact_top); \
522 cp->threshold = cp->space->initialize_threshold(); \
523 } else { \
524 compact_top = cp->space->compaction_top(); \
525 } \
526 \
527 /* We allow some amount of garbage towards the bottom of the space, so \
528 * we don't start compacting before there is a significant gain to be made.\
529 * Occasionally, we want to ensure a full compaction, which is determined \
530 * by the MarkSweepAlwaysCompactCount parameter. \
531 */ \
532 int invocations = SharedHeap::heap()->perm_gen()->stat_record()->invocations;\
533 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0); \
534 \
535 size_t allowed_deadspace = 0; \
536 if (skip_dead) { \
537 const size_t ratio = allowed_dead_ratio(); \
538 allowed_deadspace = (capacity() * ratio / 100) / HeapWordSize; \
539 } \
540 \
541 HeapWord* q = bottom(); \
542 HeapWord* t = scan_limit(); \
543 \
544 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last \
545 live object. */ \
546 HeapWord* first_dead = end();/* The first dead object. */ \
547 LiveRange* liveRange = NULL; /* The current live range, recorded in the \
548 first header of preceding free area. */ \
549 _first_dead = first_dead; \
550 \
551 const intx interval = PrefetchScanIntervalInBytes; \
552 \
553 while (q < t) { \
554 assert(!block_is_obj(q) || \
555 oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() || \
556 oop(q)->mark()->has_bias_pattern(), \
557 "these are the only valid states during a mark sweep"); \
558 if (block_is_obj(q) && oop(q)->is_gc_marked()) { \
559 /* prefetch beyond q */ \
560 Prefetch::write(q, interval); \
561 /* size_t size = oop(q)->size(); changing this for cms for perm gen */\
562 size_t size = block_size(q); \
563 compact_top = cp->space->forward(oop(q), size, cp, compact_top); \
564 q += size; \
565 end_of_live = q; \
566 } else { \
567 /* run over all the contiguous dead objects */ \
568 HeapWord* end = q; \
569 do { \
570 /* prefetch beyond end */ \
571 Prefetch::write(end, interval); \
572 end += block_size(end); \
573 } while (end < t && (!block_is_obj(end) || !oop(end)->is_gc_marked()));\
574 \
575 /* see if we might want to pretend this object is alive so that \
576 * we don't have to compact quite as often. \
577 */ \
578 if (allowed_deadspace > 0 && q == compact_top) { \
579 size_t sz = pointer_delta(end, q); \
580 if (insert_deadspace(allowed_deadspace, q, sz)) { \
581 compact_top = cp->space->forward(oop(q), sz, cp, compact_top); \
582 q = end; \
583 end_of_live = end; \
584 continue; \
585 } \
586 } \
587 \
588 /* otherwise, it really is a free region. */ \
589 \
590 /* for the previous LiveRange, record the end of the live objects. */ \
591 if (liveRange) { \
592 liveRange->set_end(q); \
593 } \
594 \
595 /* record the current LiveRange object. \
596 * liveRange->start() is overlaid on the mark word. \
597 */ \
598 liveRange = (LiveRange*)q; \
599 liveRange->set_start(end); \
600 liveRange->set_end(end); \
601 \
602 /* see if this is the first dead region. */ \
603 if (q < first_dead) { \
604 first_dead = q; \
605 } \
606 \
607 /* move on to the next object */ \
608 q = end; \
609 } \
610 } \
611 \
612 assert(q == t, "just checking"); \
613 if (liveRange != NULL) { \
614 liveRange->set_end(q); \
615 } \
616 _end_of_live = end_of_live; \
617 if (end_of_live < first_dead) { \
618 first_dead = end_of_live; \
619 } \
620 _first_dead = first_dead; \
621 \
622 /* save the compaction_top of the compaction space. */ \
623 cp->space->set_compaction_top(compact_top); \
624 }
626 #define SCAN_AND_ADJUST_POINTERS(adjust_obj_size) { \
627 /* adjust all the interior pointers to point at the new locations of objects \
628 * Used by MarkSweep::mark_sweep_phase3() */ \
629 \
630 HeapWord* q = bottom(); \
631 HeapWord* t = _end_of_live; /* Established by "prepare_for_compaction". */ \
632 \
633 assert(_first_dead <= _end_of_live, "Stands to reason, no?"); \
634 \
635 if (q < t && _first_dead > q && \
636 !oop(q)->is_gc_marked()) { \
637 /* we have a chunk of the space which hasn't moved and we've \
638 * reinitialized the mark word during the previous pass, so we can't \
639 * use is_gc_marked for the traversal. */ \
640 HeapWord* end = _first_dead; \
641 \
642 while (q < end) { \
643 /* I originally tried to conjoin "block_start(q) == q" to the \
644 * assertion below, but that doesn't work, because you can't \
645 * accurately traverse previous objects to get to the current one \
646 * after their pointers (including pointers into permGen) have been \
647 * updated, until the actual compaction is done. dld, 4/00 */ \
648 assert(block_is_obj(q), \
649 "should be at block boundaries, and should be looking at objs"); \
650 \
651 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q))); \
652 \
653 /* point all the oops to the new location */ \
654 size_t size = oop(q)->adjust_pointers(); \
655 size = adjust_obj_size(size); \
656 \
657 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers()); \
658 \
659 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size)); \
660 \
661 q += size; \
662 } \
663 \
664 if (_first_dead == t) { \
665 q = t; \
666 } else { \
667 /* $$$ This is funky. Using this to read the previously written \
668 * LiveRange. See also use below. */ \
669 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer(); \
670 } \
671 } \
672 \
673 const intx interval = PrefetchScanIntervalInBytes; \
674 \
675 debug_only(HeapWord* prev_q = NULL); \
676 while (q < t) { \
677 /* prefetch beyond q */ \
678 Prefetch::write(q, interval); \
679 if (oop(q)->is_gc_marked()) { \
680 /* q is alive */ \
681 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q))); \
682 /* point all the oops to the new location */ \
683 size_t size = oop(q)->adjust_pointers(); \
684 size = adjust_obj_size(size); \
685 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers()); \
686 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size)); \
687 debug_only(prev_q = q); \
688 q += size; \
689 } else { \
690 /* q is not a live object, so its mark should point at the next \
691 * live object */ \
692 debug_only(prev_q = q); \
693 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
694 assert(q > prev_q, "we should be moving forward through memory"); \
695 } \
696 } \
697 \
698 assert(q == t, "just checking"); \
699 }
701 #define SCAN_AND_COMPACT(obj_size) { \
702 /* Copy all live objects to their new location \
703 * Used by MarkSweep::mark_sweep_phase4() */ \
704 \
705 HeapWord* q = bottom(); \
706 HeapWord* const t = _end_of_live; \
707 debug_only(HeapWord* prev_q = NULL); \
708 \
709 if (q < t && _first_dead > q && \
710 !oop(q)->is_gc_marked()) { \
711 debug_only( \
712 /* we have a chunk of the space which hasn't moved and we've reinitialized \
713 * the mark word during the previous pass, so we can't use is_gc_marked for \
714 * the traversal. */ \
715 HeapWord* const end = _first_dead; \
716 \
717 while (q < end) { \
718 size_t size = obj_size(q); \
719 assert(!oop(q)->is_gc_marked(), \
720 "should be unmarked (special dense prefix handling)"); \
721 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, q)); \
722 debug_only(prev_q = q); \
723 q += size; \
724 } \
725 ) /* debug_only */ \
726 \
727 if (_first_dead == t) { \
728 q = t; \
729 } else { \
730 /* $$$ Funky */ \
731 q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer(); \
732 } \
733 } \
734 \
735 const intx scan_interval = PrefetchScanIntervalInBytes; \
736 const intx copy_interval = PrefetchCopyIntervalInBytes; \
737 while (q < t) { \
738 if (!oop(q)->is_gc_marked()) { \
739 /* mark is pointer to next marked oop */ \
740 debug_only(prev_q = q); \
741 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
742 assert(q > prev_q, "we should be moving forward through memory"); \
743 } else { \
744 /* prefetch beyond q */ \
745 Prefetch::read(q, scan_interval); \
746 \
747 /* size and destination */ \
748 size_t size = obj_size(q); \
749 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee(); \
750 \
751 /* prefetch beyond compaction_top */ \
752 Prefetch::write(compaction_top, copy_interval); \
753 \
754 /* copy object and reinit its mark */ \
755 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, \
756 compaction_top)); \
757 assert(q != compaction_top, "everything in this pass should be moving"); \
758 Copy::aligned_conjoint_words(q, compaction_top, size); \
759 oop(compaction_top)->init_mark(); \
760 assert(oop(compaction_top)->klass() != NULL, "should have a class"); \
761 \
762 debug_only(prev_q = q); \
763 q += size; \
764 } \
765 } \
766 \
767 /* Let's remember if we were empty before we did the compaction. */ \
768 bool was_empty = used_region().is_empty(); \
769 /* Reset space after compaction is complete */ \
770 reset_after_compaction(); \
771 /* We do this clear, below, since it has overloaded meanings for some */ \
772 /* space subtypes. For example, OffsetTableContigSpace's that were */ \
773 /* compacted into will have had their offset table thresholds updated */ \
774 /* continuously, but those that weren't need to have their thresholds */ \
775 /* re-initialized. Also mangles unused area for debugging. */ \
776 if (used_region().is_empty()) { \
777 if (!was_empty) clear(SpaceDecorator::Mangle); \
778 } else { \
779 if (ZapUnusedHeapArea) mangle_unused_area(); \
780 } \
781 }
783 class GenSpaceMangler;
785 // A space in which the free area is contiguous. It therefore supports
786 // faster allocation, and compaction.
787 class ContiguousSpace: public CompactibleSpace {
788 friend class OneContigSpaceCardGeneration;
789 friend class VMStructs;
790 protected:
791 HeapWord* _top;
792 HeapWord* _concurrent_iteration_safe_limit;
793 // A helper for mangling the unused area of the space in debug builds.
794 GenSpaceMangler* _mangler;
796 GenSpaceMangler* mangler() { return _mangler; }
798 // Allocation helpers (return NULL if full).
799 inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
800 inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
802 public:
803 ContiguousSpace();
804 ~ContiguousSpace();
806 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
807 virtual void clear(bool mangle_space);
809 // Accessors
810 HeapWord* top() const { return _top; }
811 void set_top(HeapWord* value) { _top = value; }
813 virtual void set_saved_mark() { _saved_mark_word = top(); }
814 void reset_saved_mark() { _saved_mark_word = bottom(); }
816 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
817 WaterMark top_mark() { return WaterMark(this, top()); }
818 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
819 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
821 // In debug mode mangle (write it with a particular bit
822 // pattern) the unused part of a space.
824 // Used to save the an address in a space for later use during mangling.
825 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
826 // Used to save the space's current top for later use during mangling.
827 void set_top_for_allocations() PRODUCT_RETURN;
829 // Mangle regions in the space from the current top up to the
830 // previously mangled part of the space.
831 void mangle_unused_area() PRODUCT_RETURN;
832 // Mangle [top, end)
833 void mangle_unused_area_complete() PRODUCT_RETURN;
834 // Mangle the given MemRegion.
835 void mangle_region(MemRegion mr) PRODUCT_RETURN;
837 // Do some sparse checking on the area that should have been mangled.
838 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
839 // Check the complete area that should have been mangled.
840 // This code may be NULL depending on the macro DEBUG_MANGLING.
841 void check_mangled_unused_area_complete() PRODUCT_RETURN;
843 // Size computations: sizes in bytes.
844 size_t capacity() const { return byte_size(bottom(), end()); }
845 size_t used() const { return byte_size(bottom(), top()); }
846 size_t free() const { return byte_size(top(), end()); }
848 // Override from space.
849 bool is_in(const void* p) const;
851 virtual bool is_free_block(const HeapWord* p) const;
853 // In a contiguous space we have a more obvious bound on what parts
854 // contain objects.
855 MemRegion used_region() const { return MemRegion(bottom(), top()); }
857 MemRegion used_region_at_save_marks() const {
858 return MemRegion(bottom(), saved_mark_word());
859 }
861 // Allocation (return NULL if full)
862 virtual HeapWord* allocate(size_t word_size);
863 virtual HeapWord* par_allocate(size_t word_size);
865 virtual bool obj_allocated_since_save_marks(const oop obj) const {
866 return (HeapWord*)obj >= saved_mark_word();
867 }
869 // Iteration
870 void oop_iterate(OopClosure* cl);
871 void oop_iterate(MemRegion mr, OopClosure* cl);
872 void object_iterate(ObjectClosure* blk);
873 // For contiguous spaces this method will iterate safely over objects
874 // in the space (i.e., between bottom and top) when at a safepoint.
875 void safe_object_iterate(ObjectClosure* blk);
876 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
877 // iterates on objects up to the safe limit
878 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
879 inline HeapWord* concurrent_iteration_safe_limit();
880 // changes the safe limit, all objects from bottom() to the new
881 // limit should be properly initialized
882 inline void set_concurrent_iteration_safe_limit(HeapWord* new_limit);
884 #ifndef SERIALGC
885 // In support of parallel oop_iterate.
886 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
887 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
889 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
890 #undef ContigSpace_PAR_OOP_ITERATE_DECL
891 #endif // SERIALGC
893 // Compaction support
894 virtual void reset_after_compaction() {
895 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
896 set_top(compaction_top());
897 // set new iteration safe limit
898 set_concurrent_iteration_safe_limit(compaction_top());
899 }
900 virtual size_t minimum_free_block_size() const { return 0; }
902 // Override.
903 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
904 CardTableModRefBS::PrecisionStyle precision,
905 HeapWord* boundary = NULL);
907 // Apply "blk->do_oop" to the addresses of all reference fields in objects
908 // starting with the _saved_mark_word, which was noted during a generation's
909 // save_marks and is required to denote the head of an object.
910 // Fields in objects allocated by applications of the closure
911 // *are* included in the iteration.
912 // Updates _saved_mark_word to point to just after the last object
913 // iterated over.
914 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
915 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
917 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
918 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
920 // Same as object_iterate, but starting from "mark", which is required
921 // to denote the start of an object. Objects allocated by
922 // applications of the closure *are* included in the iteration.
923 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
925 // Very inefficient implementation.
926 virtual HeapWord* block_start_const(const void* p) const;
927 size_t block_size(const HeapWord* p) const;
928 // If a block is in the allocated area, it is an object.
929 bool block_is_obj(const HeapWord* p) const { return p < top(); }
931 // Addresses for inlined allocation
932 HeapWord** top_addr() { return &_top; }
933 HeapWord** end_addr() { return &_end; }
935 // Overrides for more efficient compaction support.
936 void prepare_for_compaction(CompactPoint* cp);
938 // PrintHeapAtGC support.
939 virtual void print_on(outputStream* st) const;
941 // Checked dynamic downcasts.
942 virtual ContiguousSpace* toContiguousSpace() {
943 return this;
944 }
946 // Debugging
947 virtual void verify(bool allow_dirty) const;
949 // Used to increase collection frequency. "factor" of 0 means entire
950 // space.
951 void allocate_temporary_filler(int factor);
953 };
956 // A dirty card to oop closure that does filtering.
957 // It knows how to filter out objects that are outside of the _boundary.
958 class Filtering_DCTOC : public DirtyCardToOopClosure {
959 protected:
960 // Override.
961 void walk_mem_region(MemRegion mr,
962 HeapWord* bottom, HeapWord* top);
964 // Walk the given memory region, from bottom to top, applying
965 // the given oop closure to (possibly) all objects found. The
966 // given oop closure may or may not be the same as the oop
967 // closure with which this closure was created, as it may
968 // be a filtering closure which makes use of the _boundary.
969 // We offer two signatures, so the FilteringClosure static type is
970 // apparent.
971 virtual void walk_mem_region_with_cl(MemRegion mr,
972 HeapWord* bottom, HeapWord* top,
973 OopClosure* cl) = 0;
974 virtual void walk_mem_region_with_cl(MemRegion mr,
975 HeapWord* bottom, HeapWord* top,
976 FilteringClosure* cl) = 0;
978 public:
979 Filtering_DCTOC(Space* sp, OopClosure* cl,
980 CardTableModRefBS::PrecisionStyle precision,
981 HeapWord* boundary) :
982 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
983 };
985 // A dirty card to oop closure for contiguous spaces
986 // (ContiguousSpace and sub-classes).
987 // It is a FilteringClosure, as defined above, and it knows:
988 //
989 // 1. That the actual top of any area in a memory region
990 // contained by the space is bounded by the end of the contiguous
991 // region of the space.
992 // 2. That the space is really made up of objects and not just
993 // blocks.
995 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
996 protected:
997 // Overrides.
998 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
1000 virtual void walk_mem_region_with_cl(MemRegion mr,
1001 HeapWord* bottom, HeapWord* top,
1002 OopClosure* cl);
1003 virtual void walk_mem_region_with_cl(MemRegion mr,
1004 HeapWord* bottom, HeapWord* top,
1005 FilteringClosure* cl);
1007 public:
1008 ContiguousSpaceDCTOC(ContiguousSpace* sp, OopClosure* cl,
1009 CardTableModRefBS::PrecisionStyle precision,
1010 HeapWord* boundary) :
1011 Filtering_DCTOC(sp, cl, precision, boundary)
1012 {}
1013 };
1016 // Class EdenSpace describes eden-space in new generation.
1018 class DefNewGeneration;
1020 class EdenSpace : public ContiguousSpace {
1021 friend class VMStructs;
1022 private:
1023 DefNewGeneration* _gen;
1025 // _soft_end is used as a soft limit on allocation. As soft limits are
1026 // reached, the slow-path allocation code can invoke other actions and then
1027 // adjust _soft_end up to a new soft limit or to end().
1028 HeapWord* _soft_end;
1030 public:
1031 EdenSpace(DefNewGeneration* gen) :
1032 _gen(gen), _soft_end(NULL) {}
1034 // Get/set just the 'soft' limit.
1035 HeapWord* soft_end() { return _soft_end; }
1036 HeapWord** soft_end_addr() { return &_soft_end; }
1037 void set_soft_end(HeapWord* value) { _soft_end = value; }
1039 // Override.
1040 void clear(bool mangle_space);
1042 // Set both the 'hard' and 'soft' limits (_end and _soft_end).
1043 void set_end(HeapWord* value) {
1044 set_soft_end(value);
1045 ContiguousSpace::set_end(value);
1046 }
1048 // Allocation (return NULL if full)
1049 HeapWord* allocate(size_t word_size);
1050 HeapWord* par_allocate(size_t word_size);
1051 };
1053 // Class ConcEdenSpace extends EdenSpace for the sake of safe
1054 // allocation while soft-end is being modified concurrently
1056 class ConcEdenSpace : public EdenSpace {
1057 public:
1058 ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
1060 // Allocation (return NULL if full)
1061 HeapWord* par_allocate(size_t word_size);
1062 };
1065 // A ContigSpace that Supports an efficient "block_start" operation via
1066 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
1067 // other spaces.) This is the abstract base class for old generation
1068 // (tenured, perm) spaces.
1070 class OffsetTableContigSpace: public ContiguousSpace {
1071 friend class VMStructs;
1072 protected:
1073 BlockOffsetArrayContigSpace _offsets;
1074 Mutex _par_alloc_lock;
1076 public:
1077 // Constructor
1078 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
1079 MemRegion mr);
1081 void set_bottom(HeapWord* value);
1082 void set_end(HeapWord* value);
1084 void clear(bool mangle_space);
1086 inline HeapWord* block_start_const(const void* p) const;
1088 // Add offset table update.
1089 virtual inline HeapWord* allocate(size_t word_size);
1090 inline HeapWord* par_allocate(size_t word_size);
1092 // MarkSweep support phase3
1093 virtual HeapWord* initialize_threshold();
1094 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
1096 virtual void print_on(outputStream* st) const;
1098 // Debugging
1099 void verify(bool allow_dirty) const;
1101 // Shared space support
1102 void serialize_block_offset_array_offsets(SerializeOopClosure* soc);
1103 };
1106 // Class TenuredSpace is used by TenuredGeneration
1108 class TenuredSpace: public OffsetTableContigSpace {
1109 friend class VMStructs;
1110 protected:
1111 // Mark sweep support
1112 size_t allowed_dead_ratio() const;
1113 public:
1114 // Constructor
1115 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
1116 MemRegion mr) :
1117 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1118 };
1121 // Class ContigPermSpace is used by CompactingPermGen
1123 class ContigPermSpace: public OffsetTableContigSpace {
1124 friend class VMStructs;
1125 protected:
1126 // Mark sweep support
1127 size_t allowed_dead_ratio() const;
1128 public:
1129 // Constructor
1130 ContigPermSpace(BlockOffsetSharedArray* sharedOffsetArray, MemRegion mr) :
1131 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1132 };
1134 #endif // SHARE_VM_MEMORY_SPACE_HPP