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comparison: src/share/vm/memory/space.hpp

src/share/vm/memory/space.hpp

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1 /*
2 * Copyright (c) 1997, 2013, 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,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_MEMORY_SPACE_HPP
26 #define SHARE_VM_MEMORY_SPACE_HPP
27
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/macros.hpp"
38 #include "utilities/workgroup.hpp"
39 #ifdef TARGET_OS_FAMILY_linux
40 # include "os_linux.inline.hpp"
41 #endif
42 #ifdef TARGET_OS_FAMILY_solaris
43 # include "os_solaris.inline.hpp"
44 #endif
45 #ifdef TARGET_OS_FAMILY_windows
46 # include "os_windows.inline.hpp"
47 #endif
48 #ifdef TARGET_OS_FAMILY_aix
49 # include "os_aix.inline.hpp"
50 #endif
51 #ifdef TARGET_OS_FAMILY_bsd
52 # include "os_bsd.inline.hpp"
53 #endif
54
55 // A space is an abstraction for the "storage units" backing
56 // up the generation abstraction. It includes specific
57 // implementations for keeping track of free and used space,
58 // for iterating over objects and free blocks, etc.
59
60 // Here's the Space hierarchy:
61 //
62 // - Space -- an asbtract base class describing a heap area
63 // - CompactibleSpace -- a space supporting compaction
64 // - CompactibleFreeListSpace -- (used for CMS generation)
65 // - ContiguousSpace -- a compactible space in which all free space
66 // is contiguous
67 // - EdenSpace -- contiguous space used as nursery
68 // - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation
69 // - OffsetTableContigSpace -- contiguous space with a block offset array
70 // that allows "fast" block_start calls
71 // - TenuredSpace -- (used for TenuredGeneration)
72
73 // Forward decls.
74 class Space;
75 class BlockOffsetArray;
76 class BlockOffsetArrayContigSpace;
77 class Generation;
78 class CompactibleSpace;
79 class BlockOffsetTable;
80 class GenRemSet;
81 class CardTableRS;
82 class DirtyCardToOopClosure;
83
84 // An oop closure that is circumscribed by a filtering memory region.
85 class SpaceMemRegionOopsIterClosure: public ExtendedOopClosure {
86 private:
87 ExtendedOopClosure* _cl;
88 MemRegion _mr;
89 protected:
90 template <class T> void do_oop_work(T* p) {
91 if (_mr.contains(p)) {
92 _cl->do_oop(p);
93 }
94 }
95 public:
96 SpaceMemRegionOopsIterClosure(ExtendedOopClosure* cl, MemRegion mr):
97 _cl(cl), _mr(mr) {}
98 virtual void do_oop(oop* p);
99 virtual void do_oop(narrowOop* p);
100 virtual bool do_metadata() {
101 // _cl is of type ExtendedOopClosure instead of OopClosure, so that we can check this.
102 assert(!_cl->do_metadata(), "I've checked all call paths, this shouldn't happen.");
103 return false;
104 }
105 virtual void do_klass(Klass* k) { ShouldNotReachHere(); }
106 virtual void do_class_loader_data(ClassLoaderData* cld) { ShouldNotReachHere(); }
107 };
108
109 // A Space describes a heap area. Class Space is an abstract
110 // base class.
111 //
112 // Space supports allocation, size computation and GC support is provided.
113 //
114 // Invariant: bottom() and end() are on page_size boundaries and
115 // bottom() <= top() <= end()
116 // top() is inclusive and end() is exclusive.
117
118 class Space: public CHeapObj<mtGC> {
119 friend class VMStructs;
120 protected:
121 HeapWord* _bottom;
122 HeapWord* _end;
123
124 // Used in support of save_marks()
125 HeapWord* _saved_mark_word;
126
127 MemRegionClosure* _preconsumptionDirtyCardClosure;
128
129 // A sequential tasks done structure. This supports
130 // parallel GC, where we have threads dynamically
131 // claiming sub-tasks from a larger parallel task.
132 SequentialSubTasksDone _par_seq_tasks;
133
134 Space():
135 _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { }
136
137 public:
138 // Accessors
139 HeapWord* bottom() const { return _bottom; }
140 HeapWord* end() const { return _end; }
141 virtual void set_bottom(HeapWord* value) { _bottom = value; }
142 virtual void set_end(HeapWord* value) { _end = value; }
143
144 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
145
146 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
147
148 MemRegionClosure* preconsumptionDirtyCardClosure() const {
149 return _preconsumptionDirtyCardClosure;
150 }
151 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
152 _preconsumptionDirtyCardClosure = cl;
153 }
154
155 // Returns a subregion of the space containing all the objects in
156 // the space.
157 virtual MemRegion used_region() const { return MemRegion(bottom(), end()); }
158
159 // Returns a region that is guaranteed to contain (at least) all objects
160 // allocated at the time of the last call to "save_marks". If the space
161 // initializes its DirtyCardToOopClosure's specifying the "contig" option
162 // (that is, if the space is contiguous), then this region must contain only
163 // such objects: the memregion will be from the bottom of the region to the
164 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
165 // the space must distiguish between objects in the region allocated before
166 // and after the call to save marks.
167 virtual MemRegion used_region_at_save_marks() const {
168 return MemRegion(bottom(), saved_mark_word());
169 }
170
171 // Initialization.
172 // "initialize" should be called once on a space, before it is used for
173 // any purpose. The "mr" arguments gives the bounds of the space, and
174 // the "clear_space" argument should be true unless the memory in "mr" is
175 // known to be zeroed.
176 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
177
178 // The "clear" method must be called on a region that may have
179 // had allocation performed in it, but is now to be considered empty.
180 virtual void clear(bool mangle_space);
181
182 // For detecting GC bugs. Should only be called at GC boundaries, since
183 // some unused space may be used as scratch space during GC's.
184 // Default implementation does nothing. We also call this when expanding
185 // a space to satisfy an allocation request. See bug #4668531
186 virtual void mangle_unused_area() {}
187 virtual void mangle_unused_area_complete() {}
188 virtual void mangle_region(MemRegion mr) {}
189
190 // Testers
191 bool is_empty() const { return used() == 0; }
192 bool not_empty() const { return used() > 0; }
193
194 // Returns true iff the given the space contains the
195 // given address as part of an allocated object. For
196 // ceratin kinds of spaces, this might be a potentially
197 // expensive operation. To prevent performance problems
198 // on account of its inadvertent use in product jvm's,
199 // we restrict its use to assertion checks only.
200 virtual bool is_in(const void* p) const = 0;
201
202 // Returns true iff the given reserved memory of the space contains the
203 // given address.
204 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
205
206 // Returns true iff the given block is not allocated.
207 virtual bool is_free_block(const HeapWord* p) const = 0;
208
209 // Test whether p is double-aligned
210 static bool is_aligned(void* p) {
211 return ((intptr_t)p & (sizeof(double)-1)) == 0;
212 }
213
214 // Size computations. Sizes are in bytes.
215 size_t capacity() const { return byte_size(bottom(), end()); }
216 virtual size_t used() const = 0;
217 virtual size_t free() const = 0;
218
219 // Iterate over all the ref-containing fields of all objects in the
220 // space, calling "cl.do_oop" on each. Fields in objects allocated by
221 // applications of the closure are not included in the iteration.
222 virtual void oop_iterate(ExtendedOopClosure* cl);
223
224 // Same as above, restricted to the intersection of a memory region and
225 // the space. Fields in objects allocated by applications of the closure
226 // are not included in the iteration.
227 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl) = 0;
228
229 // Iterate over all objects in the space, calling "cl.do_object" on
230 // each. Objects allocated by applications of the closure are not
231 // included in the iteration.
232 virtual void object_iterate(ObjectClosure* blk) = 0;
233 // Similar to object_iterate() except only iterates over
234 // objects whose internal references point to objects in the space.
235 virtual void safe_object_iterate(ObjectClosure* blk) = 0;
236
237 // Iterate over all objects that intersect with mr, calling "cl->do_object"
238 // on each. There is an exception to this: if this closure has already
239 // been invoked on an object, it may skip such objects in some cases. This is
240 // Most likely to happen in an "upwards" (ascending address) iteration of
241 // MemRegions.
242 virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
243
244 // Iterate over as many initialized objects in the space as possible,
245 // calling "cl.do_object_careful" on each. Return NULL if all objects
246 // in the space (at the start of the iteration) were iterated over.
247 // Return an address indicating the extent of the iteration in the
248 // event that the iteration had to return because of finding an
249 // uninitialized object in the space, or if the closure "cl"
250 // signalled early termination.
251 virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
252 virtual HeapWord* object_iterate_careful_m(MemRegion mr,
253 ObjectClosureCareful* cl);
254
255 // Create and return a new dirty card to oop closure. Can be
256 // overriden to return the appropriate type of closure
257 // depending on the type of space in which the closure will
258 // operate. ResourceArea allocated.
259 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
260 CardTableModRefBS::PrecisionStyle precision,
261 HeapWord* boundary = NULL);
262
263 // If "p" is in the space, returns the address of the start of the
264 // "block" that contains "p". We say "block" instead of "object" since
265 // some heaps may not pack objects densely; a chunk may either be an
266 // object or a non-object. If "p" is not in the space, return NULL.
267 virtual HeapWord* block_start_const(const void* p) const = 0;
268
269 // The non-const version may have benevolent side effects on the data
270 // structure supporting these calls, possibly speeding up future calls.
271 // The default implementation, however, is simply to call the const
272 // version.
273 inline virtual HeapWord* block_start(const void* p);
274
275 // Requires "addr" to be the start of a chunk, and returns its size.
276 // "addr + size" is required to be the start of a new chunk, or the end
277 // of the active area of the heap.
278 virtual size_t block_size(const HeapWord* addr) const = 0;
279
280 // Requires "addr" to be the start of a block, and returns "TRUE" iff
281 // the block is an object.
282 virtual bool block_is_obj(const HeapWord* addr) const = 0;
283
284 // Requires "addr" to be the start of a block, and returns "TRUE" iff
285 // the block is an object and the object is alive.
286 virtual bool obj_is_alive(const HeapWord* addr) const;
287
288 // Allocation (return NULL if full). Assumes the caller has established
289 // mutually exclusive access to the space.
290 virtual HeapWord* allocate(size_t word_size) = 0;
291
292 // Allocation (return NULL if full). Enforces mutual exclusion internally.
293 virtual HeapWord* par_allocate(size_t word_size) = 0;
294
295 // Returns true if this object has been allocated since a
296 // generation's "save_marks" call.
297 virtual bool obj_allocated_since_save_marks(const oop obj) const = 0;
298
299 // Mark-sweep-compact support: all spaces can update pointers to objects
300 // moving as a part of compaction.
301 virtual void adjust_pointers();
302
303 // PrintHeapAtGC support
304 virtual void print() const;
305 virtual void print_on(outputStream* st) const;
306 virtual void print_short() const;
307 virtual void print_short_on(outputStream* st) const;
308
309
310 // Accessor for parallel sequential tasks.
311 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
312
313 // IF "this" is a ContiguousSpace, return it, else return NULL.
314 virtual ContiguousSpace* toContiguousSpace() {
315 return NULL;
316 }
317
318 // Debugging
319 virtual void verify() const = 0;
320 };
321
322 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
323 // OopClosure to (the addresses of) all the ref-containing fields that could
324 // be modified by virtue of the given MemRegion being dirty. (Note that
325 // because of the imprecise nature of the write barrier, this may iterate
326 // over oops beyond the region.)
327 // This base type for dirty card to oop closures handles memory regions
328 // in non-contiguous spaces with no boundaries, and should be sub-classed
329 // to support other space types. See ContiguousDCTOC for a sub-class
330 // that works with ContiguousSpaces.
331
332 class DirtyCardToOopClosure: public MemRegionClosureRO {
333 protected:
334 ExtendedOopClosure* _cl;
335 Space* _sp;
336 CardTableModRefBS::PrecisionStyle _precision;
337 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
338 // pointing below boundary.
339 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
340 // a downwards traversal; this is the
341 // lowest location already done (or,
342 // alternatively, the lowest address that
343 // shouldn't be done again. NULL means infinity.)
344 NOT_PRODUCT(HeapWord* _last_bottom;)
345 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
346
347 // Get the actual top of the area on which the closure will
348 // operate, given where the top is assumed to be (the end of the
349 // memory region passed to do_MemRegion) and where the object
350 // at the top is assumed to start. For example, an object may
351 // start at the top but actually extend past the assumed top,
352 // in which case the top becomes the end of the object.
353 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
354
355 // Walk the given memory region from bottom to (actual) top
356 // looking for objects and applying the oop closure (_cl) to
357 // them. The base implementation of this treats the area as
358 // blocks, where a block may or may not be an object. Sub-
359 // classes should override this to provide more accurate
360 // or possibly more efficient walking.
361 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
362
363 public:
364 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl,
365 CardTableModRefBS::PrecisionStyle precision,
366 HeapWord* boundary) :
367 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
368 _min_done(NULL) {
369 NOT_PRODUCT(_last_bottom = NULL);
370 NOT_PRODUCT(_last_explicit_min_done = NULL);
371 }
372
373 void do_MemRegion(MemRegion mr);
374
375 void set_min_done(HeapWord* min_done) {
376 _min_done = min_done;
377 NOT_PRODUCT(_last_explicit_min_done = _min_done);
378 }
379 #ifndef PRODUCT
380 void set_last_bottom(HeapWord* last_bottom) {
381 _last_bottom = last_bottom;
382 }
383 #endif
384 };
385
386 // A structure to represent a point at which objects are being copied
387 // during compaction.
388 class CompactPoint : public StackObj {
389 public:
390 Generation* gen;
391 CompactibleSpace* space;
392 HeapWord* threshold;
393 CompactPoint(Generation* _gen, CompactibleSpace* _space,
394 HeapWord* _threshold) :
395 gen(_gen), space(_space), threshold(_threshold) {}
396 };
397
398
399 // A space that supports compaction operations. This is usually, but not
400 // necessarily, a space that is normally contiguous. But, for example, a
401 // free-list-based space whose normal collection is a mark-sweep without
402 // compaction could still support compaction in full GC's.
403
404 class CompactibleSpace: public Space {
405 friend class VMStructs;
406 friend class CompactibleFreeListSpace;
407 private:
408 HeapWord* _compaction_top;
409 CompactibleSpace* _next_compaction_space;
410
411 public:
412 CompactibleSpace() :
413 _compaction_top(NULL), _next_compaction_space(NULL) {}
414
415 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
416 virtual void clear(bool mangle_space);
417
418 // Used temporarily during a compaction phase to hold the value
419 // top should have when compaction is complete.
420 HeapWord* compaction_top() const { return _compaction_top; }
421
422 void set_compaction_top(HeapWord* value) {
423 assert(value == NULL || (value >= bottom() && value <= end()),
424 "should point inside space");
425 _compaction_top = value;
426 }
427
428 // Perform operations on the space needed after a compaction
429 // has been performed.
430 virtual void reset_after_compaction() {}
431
432 // Returns the next space (in the current generation) to be compacted in
433 // the global compaction order. Also is used to select the next
434 // space into which to compact.
435
436 virtual CompactibleSpace* next_compaction_space() const {
437 return _next_compaction_space;
438 }
439
440 void set_next_compaction_space(CompactibleSpace* csp) {
441 _next_compaction_space = csp;
442 }
443
444 // MarkSweep support phase2
445
446 // Start the process of compaction of the current space: compute
447 // post-compaction addresses, and insert forwarding pointers. The fields
448 // "cp->gen" and "cp->compaction_space" are the generation and space into
449 // which we are currently compacting. This call updates "cp" as necessary,
450 // and leaves the "compaction_top" of the final value of
451 // "cp->compaction_space" up-to-date. Offset tables may be updated in
452 // this phase as if the final copy had occurred; if so, "cp->threshold"
453 // indicates when the next such action should be taken.
454 virtual void prepare_for_compaction(CompactPoint* cp);
455 // MarkSweep support phase3
456 virtual void adjust_pointers();
457 // MarkSweep support phase4
458 virtual void compact();
459
460 // The maximum percentage of objects that can be dead in the compacted
461 // live part of a compacted space ("deadwood" support.)
462 virtual size_t allowed_dead_ratio() const { return 0; };
463
464 // Some contiguous spaces may maintain some data structures that should
465 // be updated whenever an allocation crosses a boundary. This function
466 // returns the first such boundary.
467 // (The default implementation returns the end of the space, so the
468 // boundary is never crossed.)
469 virtual HeapWord* initialize_threshold() { return end(); }
470
471 // "q" is an object of the given "size" that should be forwarded;
472 // "cp" names the generation ("gen") and containing "this" (which must
473 // also equal "cp->space"). "compact_top" is where in "this" the
474 // next object should be forwarded to. If there is room in "this" for
475 // the object, insert an appropriate forwarding pointer in "q".
476 // If not, go to the next compaction space (there must
477 // be one, since compaction must succeed -- we go to the first space of
478 // the previous generation if necessary, updating "cp"), reset compact_top
479 // and then forward. In either case, returns the new value of "compact_top".
480 // If the forwarding crosses "cp->threshold", invokes the "cross_threhold"
481 // function of the then-current compaction space, and updates "cp->threshold
482 // accordingly".
483 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
484 HeapWord* compact_top);
485
486 // Return a size with adjusments as required of the space.
487 virtual size_t adjust_object_size_v(size_t size) const { return size; }
488
489 protected:
490 // Used during compaction.
491 HeapWord* _first_dead;
492 HeapWord* _end_of_live;
493
494 // Minimum size of a free block.
495 virtual size_t minimum_free_block_size() const = 0;
496
497 // This the function is invoked when an allocation of an object covering
498 // "start" to "end occurs crosses the threshold; returns the next
499 // threshold. (The default implementation does nothing.)
500 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
501 return end();
502 }
503
504 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
505 // free block of the given "word_len", and that "q", were it an object,
506 // would not move if forwared. If the size allows, fill the free
507 // block with an object, to prevent excessive compaction. Returns "true"
508 // iff the free region was made deadspace, and modifies
509 // "allowed_deadspace_words" to reflect the number of available deadspace
510 // words remaining after this operation.
511 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
512 size_t word_len);
513 };
514
515 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) { \
516 /* Compute the new addresses for the live objects and store it in the mark \
517 * Used by universe::mark_sweep_phase2() \
518 */ \
519 HeapWord* compact_top; /* This is where we are currently compacting to. */ \
520 \
521 /* We're sure to be here before any objects are compacted into this \
522 * space, so this is a good time to initialize this: \
523 */ \
524 set_compaction_top(bottom()); \
525 \
526 if (cp->space == NULL) { \
527 assert(cp->gen != NULL, "need a generation"); \
528 assert(cp->threshold == NULL, "just checking"); \
529 assert(cp->gen->first_compaction_space() == this, "just checking"); \
530 cp->space = cp->gen->first_compaction_space(); \
531 compact_top = cp->space->bottom(); \
532 cp->space->set_compaction_top(compact_top); \
533 cp->threshold = cp->space->initialize_threshold(); \
534 } else { \
535 compact_top = cp->space->compaction_top(); \
536 } \
537 \
538 /* We allow some amount of garbage towards the bottom of the space, so \
539 * we don't start compacting before there is a significant gain to be made.\
540 * Occasionally, we want to ensure a full compaction, which is determined \
541 * by the MarkSweepAlwaysCompactCount parameter. \
542 */ \
543 uint invocations = MarkSweep::total_invocations(); \
544 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0); \
545 \
546 size_t allowed_deadspace = 0; \
547 if (skip_dead) { \
548 const size_t ratio = allowed_dead_ratio(); \
549 allowed_deadspace = (capacity() * ratio / 100) / HeapWordSize; \
550 } \
551 \
552 HeapWord* q = bottom(); \
553 HeapWord* t = scan_limit(); \
554 \
555 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last \
556 live object. */ \
557 HeapWord* first_dead = end();/* The first dead object. */ \
558 LiveRange* liveRange = NULL; /* The current live range, recorded in the \
559 first header of preceding free area. */ \
560 _first_dead = first_dead; \
561 \
562 const intx interval = PrefetchScanIntervalInBytes; \
563 \
564 while (q < t) { \
565 assert(!block_is_obj(q) || \
566 oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() || \
567 oop(q)->mark()->has_bias_pattern(), \
568 "these are the only valid states during a mark sweep"); \
569 if (block_is_obj(q) && oop(q)->is_gc_marked()) { \
570 /* prefetch beyond q */ \
571 Prefetch::write(q, interval); \
572 size_t size = block_size(q); \
573 compact_top = cp->space->forward(oop(q), size, cp, compact_top); \
574 q += size; \
575 end_of_live = q; \
576 } else { \
577 /* run over all the contiguous dead objects */ \
578 HeapWord* end = q; \
579 do { \
580 /* prefetch beyond end */ \
581 Prefetch::write(end, interval); \
582 end += block_size(end); \
583 } while (end < t && (!block_is_obj(end) || !oop(end)->is_gc_marked()));\
584 \
585 /* see if we might want to pretend this object is alive so that \
586 * we don't have to compact quite as often. \
587 */ \
588 if (allowed_deadspace > 0 && q == compact_top) { \
589 size_t sz = pointer_delta(end, q); \
590 if (insert_deadspace(allowed_deadspace, q, sz)) { \
591 compact_top = cp->space->forward(oop(q), sz, cp, compact_top); \
592 q = end; \
593 end_of_live = end; \
594 continue; \
595 } \
596 } \
597 \
598 /* otherwise, it really is a free region. */ \
599 \
600 /* for the previous LiveRange, record the end of the live objects. */ \
601 if (liveRange) { \
602 liveRange->set_end(q); \
603 } \
604 \
605 /* record the current LiveRange object. \
606 * liveRange->start() is overlaid on the mark word. \
607 */ \
608 liveRange = (LiveRange*)q; \
609 liveRange->set_start(end); \
610 liveRange->set_end(end); \
611 \
612 /* see if this is the first dead region. */ \
613 if (q < first_dead) { \
614 first_dead = q; \
615 } \
616 \
617 /* move on to the next object */ \
618 q = end; \
619 } \
620 } \
621 \
622 assert(q == t, "just checking"); \
623 if (liveRange != NULL) { \
624 liveRange->set_end(q); \
625 } \
626 _end_of_live = end_of_live; \
627 if (end_of_live < first_dead) { \
628 first_dead = end_of_live; \
629 } \
630 _first_dead = first_dead; \
631 \
632 /* save the compaction_top of the compaction space. */ \
633 cp->space->set_compaction_top(compact_top); \
634 }
635
636 #define SCAN_AND_ADJUST_POINTERS(adjust_obj_size) { \
637 /* adjust all the interior pointers to point at the new locations of objects \
638 * Used by MarkSweep::mark_sweep_phase3() */ \
639 \
640 HeapWord* q = bottom(); \
641 HeapWord* t = _end_of_live; /* Established by "prepare_for_compaction". */ \
642 \
643 assert(_first_dead <= _end_of_live, "Stands to reason, no?"); \
644 \
645 if (q < t && _first_dead > q && \
646 !oop(q)->is_gc_marked()) { \
647 /* we have a chunk of the space which hasn't moved and we've \
648 * reinitialized the mark word during the previous pass, so we can't \
649 * use is_gc_marked for the traversal. */ \
650 HeapWord* end = _first_dead; \
651 \
652 while (q < end) { \
653 /* I originally tried to conjoin "block_start(q) == q" to the \
654 * assertion below, but that doesn't work, because you can't \
655 * accurately traverse previous objects to get to the current one \
656 * after their pointers have been \
657 * updated, until the actual compaction is done. dld, 4/00 */ \
658 assert(block_is_obj(q), \
659 "should be at block boundaries, and should be looking at objs"); \
660 \
661 /* point all the oops to the new location */ \
662 size_t size = oop(q)->adjust_pointers(); \
663 size = adjust_obj_size(size); \
664 \
665 q += size; \
666 } \
667 \
668 if (_first_dead == t) { \
669 q = t; \
670 } else { \
671 /* $$$ This is funky. Using this to read the previously written \
672 * LiveRange. See also use below. */ \
673 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer(); \
674 } \
675 } \
676 \
677 const intx interval = PrefetchScanIntervalInBytes; \
678 \
679 debug_only(HeapWord* prev_q = NULL); \
680 while (q < t) { \
681 /* prefetch beyond q */ \
682 Prefetch::write(q, interval); \
683 if (oop(q)->is_gc_marked()) { \
684 /* q is alive */ \
685 /* point all the oops to the new location */ \
686 size_t size = oop(q)->adjust_pointers(); \
687 size = adjust_obj_size(size); \
688 debug_only(prev_q = q); \
689 q += size; \
690 } else { \
691 /* q is not a live object, so its mark should point at the next \
692 * live object */ \
693 debug_only(prev_q = q); \
694 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
695 assert(q > prev_q, "we should be moving forward through memory"); \
696 } \
697 } \
698 \
699 assert(q == t, "just checking"); \
700 }
701
702 #define SCAN_AND_COMPACT(obj_size) { \
703 /* Copy all live objects to their new location \
704 * Used by MarkSweep::mark_sweep_phase4() */ \
705 \
706 HeapWord* q = bottom(); \
707 HeapWord* const t = _end_of_live; \
708 debug_only(HeapWord* prev_q = NULL); \
709 \
710 if (q < t && _first_dead > q && \
711 !oop(q)->is_gc_marked()) { \
712 debug_only( \
713 /* we have a chunk of the space which hasn't moved and we've reinitialized \
714 * the mark word during the previous pass, so we can't use is_gc_marked for \
715 * the traversal. */ \
716 HeapWord* const end = _first_dead; \
717 \
718 while (q < end) { \
719 size_t size = obj_size(q); \
720 assert(!oop(q)->is_gc_marked(), \
721 "should be unmarked (special dense prefix handling)"); \
722 debug_only(prev_q = q); \
723 q += size; \
724 } \
725 ) /* debug_only */ \
726 \
727 if (_first_dead == t) { \
728 q = t; \
729 } else { \
730 /* $$$ 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 assert(q != compaction_top, "everything in this pass should be moving"); \
756 Copy::aligned_conjoint_words(q, compaction_top, size); \
757 oop(compaction_top)->init_mark(); \
758 assert(oop(compaction_top)->klass() != NULL, "should have a class"); \
759 \
760 debug_only(prev_q = q); \
761 q += size; \
762 } \
763 } \
764 \
765 /* Let's remember if we were empty before we did the compaction. */ \
766 bool was_empty = used_region().is_empty(); \
767 /* Reset space after compaction is complete */ \
768 reset_after_compaction(); \
769 /* We do this clear, below, since it has overloaded meanings for some */ \
770 /* space subtypes. For example, OffsetTableContigSpace's that were */ \
771 /* compacted into will have had their offset table thresholds updated */ \
772 /* continuously, but those that weren't need to have their thresholds */ \
773 /* re-initialized. Also mangles unused area for debugging. */ \
774 if (used_region().is_empty()) { \
775 if (!was_empty) clear(SpaceDecorator::Mangle); \
776 } else { \
777 if (ZapUnusedHeapArea) mangle_unused_area(); \
778 } \
779 }
780
781 class GenSpaceMangler;
782
783 // A space in which the free area is contiguous. It therefore supports
784 // faster allocation, and compaction.
785 class ContiguousSpace: public CompactibleSpace {
786 friend class OneContigSpaceCardGeneration;
787 friend class VMStructs;
788 protected:
789 HeapWord* _top;
790 HeapWord* _concurrent_iteration_safe_limit;
791 // A helper for mangling the unused area of the space in debug builds.
792 GenSpaceMangler* _mangler;
793
794 GenSpaceMangler* mangler() { return _mangler; }
795
796 // Allocation helpers (return NULL if full).
797 inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
798 inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
799
800 public:
801 ContiguousSpace();
802 ~ContiguousSpace();
803
804 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
805 virtual void clear(bool mangle_space);
806
807 // Accessors
808 HeapWord* top() const { return _top; }
809 void set_top(HeapWord* value) { _top = value; }
810
811 virtual void set_saved_mark() { _saved_mark_word = top(); }
812 void reset_saved_mark() { _saved_mark_word = bottom(); }
813
814 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
815 WaterMark top_mark() { return WaterMark(this, top()); }
816 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
817 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
818
819 // In debug mode mangle (write it with a particular bit
820 // pattern) the unused part of a space.
821
822 // Used to save the an address in a space for later use during mangling.
823 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
824 // Used to save the space's current top for later use during mangling.
825 void set_top_for_allocations() PRODUCT_RETURN;
826
827 // Mangle regions in the space from the current top up to the
828 // previously mangled part of the space.
829 void mangle_unused_area() PRODUCT_RETURN;
830 // Mangle [top, end)
831 void mangle_unused_area_complete() PRODUCT_RETURN;
832 // Mangle the given MemRegion.
833 void mangle_region(MemRegion mr) PRODUCT_RETURN;
834
835 // Do some sparse checking on the area that should have been mangled.
836 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
837 // Check the complete area that should have been mangled.
838 // This code may be NULL depending on the macro DEBUG_MANGLING.
839 void check_mangled_unused_area_complete() PRODUCT_RETURN;
840
841 // Size computations: sizes in bytes.
842 size_t capacity() const { return byte_size(bottom(), end()); }
843 size_t used() const { return byte_size(bottom(), top()); }
844 size_t free() const { return byte_size(top(), end()); }
845
846 // Override from space.
847 bool is_in(const void* p) const;
848
849 virtual bool is_free_block(const HeapWord* p) const;
850
851 // In a contiguous space we have a more obvious bound on what parts
852 // contain objects.
853 MemRegion used_region() const { return MemRegion(bottom(), top()); }
854
855 MemRegion used_region_at_save_marks() const {
856 return MemRegion(bottom(), saved_mark_word());
857 }
858
859 // Allocation (return NULL if full)
860 virtual HeapWord* allocate(size_t word_size);
861 virtual HeapWord* par_allocate(size_t word_size);
862
863 virtual bool obj_allocated_since_save_marks(const oop obj) const {
864 return (HeapWord*)obj >= saved_mark_word();
865 }
866
867 // Iteration
868 void oop_iterate(ExtendedOopClosure* cl);
869 void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
870 void object_iterate(ObjectClosure* blk);
871 // For contiguous spaces this method will iterate safely over objects
872 // in the space (i.e., between bottom and top) when at a safepoint.
873 void safe_object_iterate(ObjectClosure* blk);
874 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
875 // iterates on objects up to the safe limit
876 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
877 HeapWord* concurrent_iteration_safe_limit() {
878 assert(_concurrent_iteration_safe_limit <= top(),
879 "_concurrent_iteration_safe_limit update missed");
880 return _concurrent_iteration_safe_limit;
881 }
882 // changes the safe limit, all objects from bottom() to the new
883 // limit should be properly initialized
884 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
885 assert(new_limit <= top(), "uninitialized objects in the safe range");
886 _concurrent_iteration_safe_limit = new_limit;
887 }
888
889
890 #if INCLUDE_ALL_GCS
891 // In support of parallel oop_iterate.
892 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
893 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
894
895 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
896 #undef ContigSpace_PAR_OOP_ITERATE_DECL
897 #endif // INCLUDE_ALL_GCS
898
899 // Compaction support
900 virtual void reset_after_compaction() {
901 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
902 set_top(compaction_top());
903 // set new iteration safe limit
904 set_concurrent_iteration_safe_limit(compaction_top());
905 }
906 virtual size_t minimum_free_block_size() const { return 0; }
907
908 // Override.
909 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
910 CardTableModRefBS::PrecisionStyle precision,
911 HeapWord* boundary = NULL);
912
913 // Apply "blk->do_oop" to the addresses of all reference fields in objects
914 // starting with the _saved_mark_word, which was noted during a generation's
915 // save_marks and is required to denote the head of an object.
916 // Fields in objects allocated by applications of the closure
917 // *are* included in the iteration.
918 // Updates _saved_mark_word to point to just after the last object
919 // iterated over.
920 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
921 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
922
923 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
924 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
925
926 // Same as object_iterate, but starting from "mark", which is required
927 // to denote the start of an object. Objects allocated by
928 // applications of the closure *are* included in the iteration.
929 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
930
931 // Very inefficient implementation.
932 virtual HeapWord* block_start_const(const void* p) const;
933 size_t block_size(const HeapWord* p) const;
934 // If a block is in the allocated area, it is an object.
935 bool block_is_obj(const HeapWord* p) const { return p < top(); }
936
937 // Addresses for inlined allocation
938 HeapWord** top_addr() { return &_top; }
939 HeapWord** end_addr() { return &_end; }
940
941 // Overrides for more efficient compaction support.
942 void prepare_for_compaction(CompactPoint* cp);
943
944 // PrintHeapAtGC support.
945 virtual void print_on(outputStream* st) const;
946
947 // Checked dynamic downcasts.
948 virtual ContiguousSpace* toContiguousSpace() {
949 return this;
950 }
951
952 // Debugging
953 virtual void verify() const;
954
955 // Used to increase collection frequency. "factor" of 0 means entire
956 // space.
957 void allocate_temporary_filler(int factor);
958
959 };
960
961
962 // A dirty card to oop closure that does filtering.
963 // It knows how to filter out objects that are outside of the _boundary.
964 class Filtering_DCTOC : public DirtyCardToOopClosure {
965 protected:
966 // Override.
967 void walk_mem_region(MemRegion mr,
968 HeapWord* bottom, HeapWord* top);
969
970 // Walk the given memory region, from bottom to top, applying
971 // the given oop closure to (possibly) all objects found. The
972 // given oop closure may or may not be the same as the oop
973 // closure with which this closure was created, as it may
974 // be a filtering closure which makes use of the _boundary.
975 // We offer two signatures, so the FilteringClosure static type is
976 // apparent.
977 virtual void walk_mem_region_with_cl(MemRegion mr,
978 HeapWord* bottom, HeapWord* top,
979 ExtendedOopClosure* cl) = 0;
980 virtual void walk_mem_region_with_cl(MemRegion mr,
981 HeapWord* bottom, HeapWord* top,
982 FilteringClosure* cl) = 0;
983
984 public:
985 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl,
986 CardTableModRefBS::PrecisionStyle precision,
987 HeapWord* boundary) :
988 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
989 };
990
991 // A dirty card to oop closure for contiguous spaces
992 // (ContiguousSpace and sub-classes).
993 // It is a FilteringClosure, as defined above, and it knows:
994 //
995 // 1. That the actual top of any area in a memory region
996 // contained by the space is bounded by the end of the contiguous
997 // region of the space.
998 // 2. That the space is really made up of objects and not just
999 // blocks.
1000
1001 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
1002 protected:
1003 // Overrides.
1004 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
1005
1006 virtual void walk_mem_region_with_cl(MemRegion mr,
1007 HeapWord* bottom, HeapWord* top,
1008 ExtendedOopClosure* cl);
1009 virtual void walk_mem_region_with_cl(MemRegion mr,
1010 HeapWord* bottom, HeapWord* top,
1011 FilteringClosure* cl);
1012
1013 public:
1014 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
1015 CardTableModRefBS::PrecisionStyle precision,
1016 HeapWord* boundary) :
1017 Filtering_DCTOC(sp, cl, precision, boundary)
1018 {}
1019 };
1020
1021
1022 // Class EdenSpace describes eden-space in new generation.
1023
1024 class DefNewGeneration;
1025
1026 class EdenSpace : public ContiguousSpace {
1027 friend class VMStructs;
1028 private:
1029 DefNewGeneration* _gen;
1030
1031 // _soft_end is used as a soft limit on allocation. As soft limits are
1032 // reached, the slow-path allocation code can invoke other actions and then
1033 // adjust _soft_end up to a new soft limit or to end().
1034 HeapWord* _soft_end;
1035
1036 public:
1037 EdenSpace(DefNewGeneration* gen) :
1038 _gen(gen), _soft_end(NULL) {}
1039
1040 // Get/set just the 'soft' limit.
1041 HeapWord* soft_end() { return _soft_end; }
1042 HeapWord** soft_end_addr() { return &_soft_end; }
1043 void set_soft_end(HeapWord* value) { _soft_end = value; }
1044
1045 // Override.
1046 void clear(bool mangle_space);
1047
1048 // Set both the 'hard' and 'soft' limits (_end and _soft_end).
1049 void set_end(HeapWord* value) {
1050 set_soft_end(value);
1051 ContiguousSpace::set_end(value);
1052 }
1053
1054 // Allocation (return NULL if full)
1055 HeapWord* allocate(size_t word_size);
1056 HeapWord* par_allocate(size_t word_size);
1057 };
1058
1059 // Class ConcEdenSpace extends EdenSpace for the sake of safe
1060 // allocation while soft-end is being modified concurrently
1061
1062 class ConcEdenSpace : public EdenSpace {
1063 public:
1064 ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
1065
1066 // Allocation (return NULL if full)
1067 HeapWord* par_allocate(size_t word_size);
1068 };
1069
1070
1071 // A ContigSpace that Supports an efficient "block_start" operation via
1072 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
1073 // other spaces.) This is the abstract base class for old generation
1074 // (tenured) spaces.
1075
1076 class OffsetTableContigSpace: public ContiguousSpace {
1077 friend class VMStructs;
1078 protected:
1079 BlockOffsetArrayContigSpace _offsets;
1080 Mutex _par_alloc_lock;
1081
1082 public:
1083 // Constructor
1084 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
1085 MemRegion mr);
1086
1087 void set_bottom(HeapWord* value);
1088 void set_end(HeapWord* value);
1089
1090 void clear(bool mangle_space);
1091
1092 inline HeapWord* block_start_const(const void* p) const;
1093
1094 // Add offset table update.
1095 virtual inline HeapWord* allocate(size_t word_size);
1096 inline HeapWord* par_allocate(size_t word_size);
1097
1098 // MarkSweep support phase3
1099 virtual HeapWord* initialize_threshold();
1100 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
1101
1102 virtual void print_on(outputStream* st) const;
1103
1104 // Debugging
1105 void verify() const;
1106 };
1107
1108
1109 // Class TenuredSpace is used by TenuredGeneration
1110
1111 class TenuredSpace: public OffsetTableContigSpace {
1112 friend class VMStructs;
1113 protected:
1114 // Mark sweep support
1115 size_t allowed_dead_ratio() const;
1116 public:
1117 // Constructor
1118 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
1119 MemRegion mr) :
1120 OffsetTableContigSpace(sharedOffsetArray, mr) {}
1121 };
1122 #endif // SHARE_VM_MEMORY_SPACE_HPP

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