Thu, 13 Jun 2013 22:02:40 -0700
8014431: cleanup warnings indicated by the -Wunused-value compiler option on linux
Reviewed-by: dholmes, coleenp
Contributed-by: jeremymanson@google.com, calvin.cheung@oracle.com
1 /*
2 * Copyright (c) 1997, 2012, 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.
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23 */
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/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_bsd
49 # include "os_bsd.inline.hpp"
50 #endif
52 // A space is an abstraction for the "storage units" backing
53 // up the generation abstraction. It includes specific
54 // implementations for keeping track of free and used space,
55 // for iterating over objects and free blocks, etc.
57 // Here's the Space hierarchy:
58 //
59 // - Space -- an asbtract base class describing a heap area
60 // - CompactibleSpace -- a space supporting compaction
61 // - CompactibleFreeListSpace -- (used for CMS generation)
62 // - ContiguousSpace -- a compactible space in which all free space
63 // is contiguous
64 // - EdenSpace -- contiguous space used as nursery
65 // - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation
66 // - OffsetTableContigSpace -- contiguous space with a block offset array
67 // that allows "fast" block_start calls
68 // - TenuredSpace -- (used for TenuredGeneration)
70 // Forward decls.
71 class Space;
72 class BlockOffsetArray;
73 class BlockOffsetArrayContigSpace;
74 class Generation;
75 class CompactibleSpace;
76 class BlockOffsetTable;
77 class GenRemSet;
78 class CardTableRS;
79 class DirtyCardToOopClosure;
81 // An oop closure that is circumscribed by a filtering memory region.
82 class SpaceMemRegionOopsIterClosure: public ExtendedOopClosure {
83 private:
84 ExtendedOopClosure* _cl;
85 MemRegion _mr;
86 protected:
87 template <class T> void do_oop_work(T* p) {
88 if (_mr.contains(p)) {
89 _cl->do_oop(p);
90 }
91 }
92 public:
93 SpaceMemRegionOopsIterClosure(ExtendedOopClosure* cl, MemRegion mr):
94 _cl(cl), _mr(mr) {}
95 virtual void do_oop(oop* p);
96 virtual void do_oop(narrowOop* p);
97 virtual bool do_metadata() {
98 // _cl is of type ExtendedOopClosure instead of OopClosure, so that we can check this.
99 assert(!_cl->do_metadata(), "I've checked all call paths, this shouldn't happen.");
100 return false;
101 }
102 virtual void do_klass(Klass* k) { ShouldNotReachHere(); }
103 virtual void do_class_loader_data(ClassLoaderData* cld) { ShouldNotReachHere(); }
104 };
106 // A Space describes a heap area. Class Space is an abstract
107 // base class.
108 //
109 // Space supports allocation, size computation and GC support is provided.
110 //
111 // Invariant: bottom() and end() are on page_size boundaries and
112 // bottom() <= top() <= end()
113 // top() is inclusive and end() is exclusive.
115 class Space: public CHeapObj<mtGC> {
116 friend class VMStructs;
117 protected:
118 HeapWord* _bottom;
119 HeapWord* _end;
121 // Used in support of save_marks()
122 HeapWord* _saved_mark_word;
124 MemRegionClosure* _preconsumptionDirtyCardClosure;
126 // A sequential tasks done structure. This supports
127 // parallel GC, where we have threads dynamically
128 // claiming sub-tasks from a larger parallel task.
129 SequentialSubTasksDone _par_seq_tasks;
131 Space():
132 _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { }
134 public:
135 // Accessors
136 HeapWord* bottom() const { return _bottom; }
137 HeapWord* end() const { return _end; }
138 virtual void set_bottom(HeapWord* value) { _bottom = value; }
139 virtual void set_end(HeapWord* value) { _end = value; }
141 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
143 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
145 MemRegionClosure* preconsumptionDirtyCardClosure() const {
146 return _preconsumptionDirtyCardClosure;
147 }
148 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
149 _preconsumptionDirtyCardClosure = cl;
150 }
152 // Returns a subregion of the space containing all the objects in
153 // the space.
154 virtual MemRegion used_region() const { return MemRegion(bottom(), end()); }
156 // Returns a region that is guaranteed to contain (at least) all objects
157 // allocated at the time of the last call to "save_marks". If the space
158 // initializes its DirtyCardToOopClosure's specifying the "contig" option
159 // (that is, if the space is contiguous), then this region must contain only
160 // such objects: the memregion will be from the bottom of the region to the
161 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
162 // the space must distiguish between objects in the region allocated before
163 // and after the call to save marks.
164 virtual MemRegion used_region_at_save_marks() const {
165 return MemRegion(bottom(), saved_mark_word());
166 }
168 // Initialization.
169 // "initialize" should be called once on a space, before it is used for
170 // any purpose. The "mr" arguments gives the bounds of the space, and
171 // the "clear_space" argument should be true unless the memory in "mr" is
172 // known to be zeroed.
173 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
175 // The "clear" method must be called on a region that may have
176 // had allocation performed in it, but is now to be considered empty.
177 virtual void clear(bool mangle_space);
179 // For detecting GC bugs. Should only be called at GC boundaries, since
180 // some unused space may be used as scratch space during GC's.
181 // Default implementation does nothing. We also call this when expanding
182 // a space to satisfy an allocation request. See bug #4668531
183 virtual void mangle_unused_area() {}
184 virtual void mangle_unused_area_complete() {}
185 virtual void mangle_region(MemRegion mr) {}
187 // Testers
188 bool is_empty() const { return used() == 0; }
189 bool not_empty() const { return used() > 0; }
191 // Returns true iff the given the space contains the
192 // given address as part of an allocated object. For
193 // ceratin kinds of spaces, this might be a potentially
194 // expensive operation. To prevent performance problems
195 // on account of its inadvertent use in product jvm's,
196 // we restrict its use to assertion checks only.
197 virtual bool is_in(const void* p) const = 0;
199 // Returns true iff the given reserved memory of the space contains the
200 // given address.
201 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
203 // Returns true iff the given block is not allocated.
204 virtual bool is_free_block(const HeapWord* p) const = 0;
206 // Test whether p is double-aligned
207 static bool is_aligned(void* p) {
208 return ((intptr_t)p & (sizeof(double)-1)) == 0;
209 }
211 // Size computations. Sizes are in bytes.
212 size_t capacity() const { return byte_size(bottom(), end()); }
213 virtual size_t used() const = 0;
214 virtual size_t free() const = 0;
216 // Iterate over all the ref-containing fields of all objects in the
217 // space, calling "cl.do_oop" on each. Fields in objects allocated by
218 // applications of the closure are not included in the iteration.
219 virtual void oop_iterate(ExtendedOopClosure* cl);
221 // Same as above, restricted to the intersection of a memory region and
222 // the space. Fields in objects allocated by applications of the closure
223 // are not included in the iteration.
224 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl) = 0;
226 // Iterate over all objects in the space, calling "cl.do_object" on
227 // each. Objects allocated by applications of the closure are not
228 // included in the iteration.
229 virtual void object_iterate(ObjectClosure* blk) = 0;
230 // Similar to object_iterate() except only iterates over
231 // objects whose internal references point to objects in the space.
232 virtual void safe_object_iterate(ObjectClosure* blk) = 0;
234 // Iterate over all objects that intersect with mr, calling "cl->do_object"
235 // on each. There is an exception to this: if this closure has already
236 // been invoked on an object, it may skip such objects in some cases. This is
237 // Most likely to happen in an "upwards" (ascending address) iteration of
238 // MemRegions.
239 virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
241 // Iterate over as many initialized objects in the space as possible,
242 // calling "cl.do_object_careful" on each. Return NULL if all objects
243 // in the space (at the start of the iteration) were iterated over.
244 // Return an address indicating the extent of the iteration in the
245 // event that the iteration had to return because of finding an
246 // uninitialized object in the space, or if the closure "cl"
247 // signalled early termination.
248 virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
249 virtual HeapWord* object_iterate_careful_m(MemRegion mr,
250 ObjectClosureCareful* cl);
252 // Create and return a new dirty card to oop closure. Can be
253 // overriden to return the appropriate type of closure
254 // depending on the type of space in which the closure will
255 // operate. ResourceArea allocated.
256 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
257 CardTableModRefBS::PrecisionStyle precision,
258 HeapWord* boundary = NULL);
260 // If "p" is in the space, returns the address of the start of the
261 // "block" that contains "p". We say "block" instead of "object" since
262 // some heaps may not pack objects densely; a chunk may either be an
263 // object or a non-object. If "p" is not in the space, return NULL.
264 virtual HeapWord* block_start_const(const void* p) const = 0;
266 // The non-const version may have benevolent side effects on the data
267 // structure supporting these calls, possibly speeding up future calls.
268 // The default implementation, however, is simply to call the const
269 // version.
270 inline virtual HeapWord* block_start(const void* p);
272 // Requires "addr" to be the start of a chunk, and returns its size.
273 // "addr + size" is required to be the start of a new chunk, or the end
274 // of the active area of the heap.
275 virtual size_t block_size(const HeapWord* addr) const = 0;
277 // Requires "addr" to be the start of a block, and returns "TRUE" iff
278 // the block is an object.
279 virtual bool block_is_obj(const HeapWord* addr) const = 0;
281 // Requires "addr" to be the start of a block, and returns "TRUE" iff
282 // the block is an object and the object is alive.
283 virtual bool obj_is_alive(const HeapWord* addr) const;
285 // Allocation (return NULL if full). Assumes the caller has established
286 // mutually exclusive access to the space.
287 virtual HeapWord* allocate(size_t word_size) = 0;
289 // Allocation (return NULL if full). Enforces mutual exclusion internally.
290 virtual HeapWord* par_allocate(size_t word_size) = 0;
292 // Returns true if this object has been allocated since a
293 // generation's "save_marks" call.
294 virtual bool obj_allocated_since_save_marks(const oop obj) const = 0;
296 // Mark-sweep-compact support: all spaces can update pointers to objects
297 // moving as a part of compaction.
298 virtual void adjust_pointers();
300 // PrintHeapAtGC support
301 virtual void print() const;
302 virtual void print_on(outputStream* st) const;
303 virtual void print_short() const;
304 virtual void print_short_on(outputStream* st) const;
307 // Accessor for parallel sequential tasks.
308 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
310 // IF "this" is a ContiguousSpace, return it, else return NULL.
311 virtual ContiguousSpace* toContiguousSpace() {
312 return NULL;
313 }
315 // Debugging
316 virtual void verify() const = 0;
317 };
319 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
320 // OopClosure to (the addresses of) all the ref-containing fields that could
321 // be modified by virtue of the given MemRegion being dirty. (Note that
322 // because of the imprecise nature of the write barrier, this may iterate
323 // over oops beyond the region.)
324 // This base type for dirty card to oop closures handles memory regions
325 // in non-contiguous spaces with no boundaries, and should be sub-classed
326 // to support other space types. See ContiguousDCTOC for a sub-class
327 // that works with ContiguousSpaces.
329 class DirtyCardToOopClosure: public MemRegionClosureRO {
330 protected:
331 ExtendedOopClosure* _cl;
332 Space* _sp;
333 CardTableModRefBS::PrecisionStyle _precision;
334 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
335 // pointing below boundary.
336 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
337 // a downwards traversal; this is the
338 // lowest location already done (or,
339 // alternatively, the lowest address that
340 // shouldn't be done again. NULL means infinity.)
341 NOT_PRODUCT(HeapWord* _last_bottom;)
342 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
344 // Get the actual top of the area on which the closure will
345 // operate, given where the top is assumed to be (the end of the
346 // memory region passed to do_MemRegion) and where the object
347 // at the top is assumed to start. For example, an object may
348 // start at the top but actually extend past the assumed top,
349 // in which case the top becomes the end of the object.
350 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
352 // Walk the given memory region from bottom to (actual) top
353 // looking for objects and applying the oop closure (_cl) to
354 // them. The base implementation of this treats the area as
355 // blocks, where a block may or may not be an object. Sub-
356 // classes should override this to provide more accurate
357 // or possibly more efficient walking.
358 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
360 public:
361 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl,
362 CardTableModRefBS::PrecisionStyle precision,
363 HeapWord* boundary) :
364 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
365 _min_done(NULL) {
366 NOT_PRODUCT(_last_bottom = NULL);
367 NOT_PRODUCT(_last_explicit_min_done = NULL);
368 }
370 void do_MemRegion(MemRegion mr);
372 void set_min_done(HeapWord* min_done) {
373 _min_done = min_done;
374 NOT_PRODUCT(_last_explicit_min_done = _min_done);
375 }
376 #ifndef PRODUCT
377 void set_last_bottom(HeapWord* last_bottom) {
378 _last_bottom = last_bottom;
379 }
380 #endif
381 };
383 // A structure to represent a point at which objects are being copied
384 // during compaction.
385 class CompactPoint : public StackObj {
386 public:
387 Generation* gen;
388 CompactibleSpace* space;
389 HeapWord* threshold;
390 CompactPoint(Generation* _gen, CompactibleSpace* _space,
391 HeapWord* _threshold) :
392 gen(_gen), space(_space), threshold(_threshold) {}
393 };
396 // A space that supports compaction operations. This is usually, but not
397 // necessarily, a space that is normally contiguous. But, for example, a
398 // free-list-based space whose normal collection is a mark-sweep without
399 // compaction could still support compaction in full GC's.
401 class CompactibleSpace: public Space {
402 friend class VMStructs;
403 friend class CompactibleFreeListSpace;
404 private:
405 HeapWord* _compaction_top;
406 CompactibleSpace* _next_compaction_space;
408 public:
409 CompactibleSpace() :
410 _compaction_top(NULL), _next_compaction_space(NULL) {}
412 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
413 virtual void clear(bool mangle_space);
415 // Used temporarily during a compaction phase to hold the value
416 // top should have when compaction is complete.
417 HeapWord* compaction_top() const { return _compaction_top; }
419 void set_compaction_top(HeapWord* value) {
420 assert(value == NULL || (value >= bottom() && value <= end()),
421 "should point inside space");
422 _compaction_top = value;
423 }
425 // Perform operations on the space needed after a compaction
426 // has been performed.
427 virtual void reset_after_compaction() {}
429 // Returns the next space (in the current generation) to be compacted in
430 // the global compaction order. Also is used to select the next
431 // space into which to compact.
433 virtual CompactibleSpace* next_compaction_space() const {
434 return _next_compaction_space;
435 }
437 void set_next_compaction_space(CompactibleSpace* csp) {
438 _next_compaction_space = csp;
439 }
441 // MarkSweep support phase2
443 // Start the process of compaction of the current space: compute
444 // post-compaction addresses, and insert forwarding pointers. The fields
445 // "cp->gen" and "cp->compaction_space" are the generation and space into
446 // which we are currently compacting. This call updates "cp" as necessary,
447 // and leaves the "compaction_top" of the final value of
448 // "cp->compaction_space" up-to-date. Offset tables may be updated in
449 // this phase as if the final copy had occurred; if so, "cp->threshold"
450 // indicates when the next such action should be taken.
451 virtual void prepare_for_compaction(CompactPoint* cp);
452 // MarkSweep support phase3
453 virtual void adjust_pointers();
454 // MarkSweep support phase4
455 virtual void compact();
457 // The maximum percentage of objects that can be dead in the compacted
458 // live part of a compacted space ("deadwood" support.)
459 virtual size_t allowed_dead_ratio() const { return 0; };
461 // Some contiguous spaces may maintain some data structures that should
462 // be updated whenever an allocation crosses a boundary. This function
463 // returns the first such boundary.
464 // (The default implementation returns the end of the space, so the
465 // boundary is never crossed.)
466 virtual HeapWord* initialize_threshold() { return end(); }
468 // "q" is an object of the given "size" that should be forwarded;
469 // "cp" names the generation ("gen") and containing "this" (which must
470 // also equal "cp->space"). "compact_top" is where in "this" the
471 // next object should be forwarded to. If there is room in "this" for
472 // the object, insert an appropriate forwarding pointer in "q".
473 // If not, go to the next compaction space (there must
474 // be one, since compaction must succeed -- we go to the first space of
475 // the previous generation if necessary, updating "cp"), reset compact_top
476 // and then forward. In either case, returns the new value of "compact_top".
477 // If the forwarding crosses "cp->threshold", invokes the "cross_threhold"
478 // function of the then-current compaction space, and updates "cp->threshold
479 // accordingly".
480 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
481 HeapWord* compact_top);
483 // Return a size with adjusments as required of the space.
484 virtual size_t adjust_object_size_v(size_t size) const { return size; }
486 protected:
487 // Used during compaction.
488 HeapWord* _first_dead;
489 HeapWord* _end_of_live;
491 // Minimum size of a free block.
492 virtual size_t minimum_free_block_size() const = 0;
494 // This the function is invoked when an allocation of an object covering
495 // "start" to "end occurs crosses the threshold; returns the next
496 // threshold. (The default implementation does nothing.)
497 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
498 return end();
499 }
501 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
502 // free block of the given "word_len", and that "q", were it an object,
503 // would not move if forwared. If the size allows, fill the free
504 // block with an object, to prevent excessive compaction. Returns "true"
505 // iff the free region was made deadspace, and modifies
506 // "allowed_deadspace_words" to reflect the number of available deadspace
507 // words remaining after this operation.
508 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
509 size_t word_len);
510 };
512 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) { \
513 /* Compute the new addresses for the live objects and store it in the mark \
514 * Used by universe::mark_sweep_phase2() \
515 */ \
516 HeapWord* compact_top; /* This is where we are currently compacting to. */ \
517 \
518 /* We're sure to be here before any objects are compacted into this \
519 * space, so this is a good time to initialize this: \
520 */ \
521 set_compaction_top(bottom()); \
522 \
523 if (cp->space == NULL) { \
524 assert(cp->gen != NULL, "need a generation"); \
525 assert(cp->threshold == NULL, "just checking"); \
526 assert(cp->gen->first_compaction_space() == this, "just checking"); \
527 cp->space = cp->gen->first_compaction_space(); \
528 compact_top = cp->space->bottom(); \
529 cp->space->set_compaction_top(compact_top); \
530 cp->threshold = cp->space->initialize_threshold(); \
531 } else { \
532 compact_top = cp->space->compaction_top(); \
533 } \
534 \
535 /* We allow some amount of garbage towards the bottom of the space, so \
536 * we don't start compacting before there is a significant gain to be made.\
537 * Occasionally, we want to ensure a full compaction, which is determined \
538 * by the MarkSweepAlwaysCompactCount parameter. \
539 */ \
540 uint invocations = MarkSweep::total_invocations(); \
541 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0); \
542 \
543 size_t allowed_deadspace = 0; \
544 if (skip_dead) { \
545 const size_t ratio = allowed_dead_ratio(); \
546 allowed_deadspace = (capacity() * ratio / 100) / HeapWordSize; \
547 } \
548 \
549 HeapWord* q = bottom(); \
550 HeapWord* t = scan_limit(); \
551 \
552 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last \
553 live object. */ \
554 HeapWord* first_dead = end();/* The first dead object. */ \
555 LiveRange* liveRange = NULL; /* The current live range, recorded in the \
556 first header of preceding free area. */ \
557 _first_dead = first_dead; \
558 \
559 const intx interval = PrefetchScanIntervalInBytes; \
560 \
561 while (q < t) { \
562 assert(!block_is_obj(q) || \
563 oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() || \
564 oop(q)->mark()->has_bias_pattern(), \
565 "these are the only valid states during a mark sweep"); \
566 if (block_is_obj(q) && oop(q)->is_gc_marked()) { \
567 /* prefetch beyond q */ \
568 Prefetch::write(q, interval); \
569 size_t size = block_size(q); \
570 compact_top = cp->space->forward(oop(q), size, cp, compact_top); \
571 q += size; \
572 end_of_live = q; \
573 } else { \
574 /* run over all the contiguous dead objects */ \
575 HeapWord* end = q; \
576 do { \
577 /* prefetch beyond end */ \
578 Prefetch::write(end, interval); \
579 end += block_size(end); \
580 } while (end < t && (!block_is_obj(end) || !oop(end)->is_gc_marked()));\
581 \
582 /* see if we might want to pretend this object is alive so that \
583 * we don't have to compact quite as often. \
584 */ \
585 if (allowed_deadspace > 0 && q == compact_top) { \
586 size_t sz = pointer_delta(end, q); \
587 if (insert_deadspace(allowed_deadspace, q, sz)) { \
588 compact_top = cp->space->forward(oop(q), sz, cp, compact_top); \
589 q = end; \
590 end_of_live = end; \
591 continue; \
592 } \
593 } \
594 \
595 /* otherwise, it really is a free region. */ \
596 \
597 /* for the previous LiveRange, record the end of the live objects. */ \
598 if (liveRange) { \
599 liveRange->set_end(q); \
600 } \
601 \
602 /* record the current LiveRange object. \
603 * liveRange->start() is overlaid on the mark word. \
604 */ \
605 liveRange = (LiveRange*)q; \
606 liveRange->set_start(end); \
607 liveRange->set_end(end); \
608 \
609 /* see if this is the first dead region. */ \
610 if (q < first_dead) { \
611 first_dead = q; \
612 } \
613 \
614 /* move on to the next object */ \
615 q = end; \
616 } \
617 } \
618 \
619 assert(q == t, "just checking"); \
620 if (liveRange != NULL) { \
621 liveRange->set_end(q); \
622 } \
623 _end_of_live = end_of_live; \
624 if (end_of_live < first_dead) { \
625 first_dead = end_of_live; \
626 } \
627 _first_dead = first_dead; \
628 \
629 /* save the compaction_top of the compaction space. */ \
630 cp->space->set_compaction_top(compact_top); \
631 }
633 #define SCAN_AND_ADJUST_POINTERS(adjust_obj_size) { \
634 /* adjust all the interior pointers to point at the new locations of objects \
635 * Used by MarkSweep::mark_sweep_phase3() */ \
636 \
637 HeapWord* q = bottom(); \
638 HeapWord* t = _end_of_live; /* Established by "prepare_for_compaction". */ \
639 \
640 assert(_first_dead <= _end_of_live, "Stands to reason, no?"); \
641 \
642 if (q < t && _first_dead > q && \
643 !oop(q)->is_gc_marked()) { \
644 /* we have a chunk of the space which hasn't moved and we've \
645 * reinitialized the mark word during the previous pass, so we can't \
646 * use is_gc_marked for the traversal. */ \
647 HeapWord* end = _first_dead; \
648 \
649 while (q < end) { \
650 /* I originally tried to conjoin "block_start(q) == q" to the \
651 * assertion below, but that doesn't work, because you can't \
652 * accurately traverse previous objects to get to the current one \
653 * after their pointers have been \
654 * updated, until the actual compaction is done. dld, 4/00 */ \
655 assert(block_is_obj(q), \
656 "should be at block boundaries, and should be looking at objs"); \
657 \
658 /* point all the oops to the new location */ \
659 size_t size = oop(q)->adjust_pointers(); \
660 size = adjust_obj_size(size); \
661 \
662 q += size; \
663 } \
664 \
665 if (_first_dead == t) { \
666 q = t; \
667 } else { \
668 /* $$$ This is funky. Using this to read the previously written \
669 * LiveRange. See also use below. */ \
670 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer(); \
671 } \
672 } \
673 \
674 const intx interval = PrefetchScanIntervalInBytes; \
675 \
676 debug_only(HeapWord* prev_q = NULL); \
677 while (q < t) { \
678 /* prefetch beyond q */ \
679 Prefetch::write(q, interval); \
680 if (oop(q)->is_gc_marked()) { \
681 /* q is alive */ \
682 /* point all the oops to the new location */ \
683 size_t size = oop(q)->adjust_pointers(); \
684 size = adjust_obj_size(size); \
685 debug_only(prev_q = q); \
686 q += size; \
687 } else { \
688 /* q is not a live object, so its mark should point at the next \
689 * live object */ \
690 debug_only(prev_q = q); \
691 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
692 assert(q > prev_q, "we should be moving forward through memory"); \
693 } \
694 } \
695 \
696 assert(q == t, "just checking"); \
697 }
699 #define SCAN_AND_COMPACT(obj_size) { \
700 /* Copy all live objects to their new location \
701 * Used by MarkSweep::mark_sweep_phase4() */ \
702 \
703 HeapWord* q = bottom(); \
704 HeapWord* const t = _end_of_live; \
705 debug_only(HeapWord* prev_q = NULL); \
706 \
707 if (q < t && _first_dead > q && \
708 !oop(q)->is_gc_marked()) { \
709 debug_only( \
710 /* we have a chunk of the space which hasn't moved and we've reinitialized \
711 * the mark word during the previous pass, so we can't use is_gc_marked for \
712 * the traversal. */ \
713 HeapWord* const end = _first_dead; \
714 \
715 while (q < end) { \
716 size_t size = obj_size(q); \
717 assert(!oop(q)->is_gc_marked(), \
718 "should be unmarked (special dense prefix handling)"); \
719 debug_only(prev_q = q); \
720 q += size; \
721 } \
722 ) /* debug_only */ \
723 \
724 if (_first_dead == t) { \
725 q = t; \
726 } else { \
727 /* $$$ Funky */ \
728 q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer(); \
729 } \
730 } \
731 \
732 const intx scan_interval = PrefetchScanIntervalInBytes; \
733 const intx copy_interval = PrefetchCopyIntervalInBytes; \
734 while (q < t) { \
735 if (!oop(q)->is_gc_marked()) { \
736 /* mark is pointer to next marked oop */ \
737 debug_only(prev_q = q); \
738 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \
739 assert(q > prev_q, "we should be moving forward through memory"); \
740 } else { \
741 /* prefetch beyond q */ \
742 Prefetch::read(q, scan_interval); \
743 \
744 /* size and destination */ \
745 size_t size = obj_size(q); \
746 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee(); \
747 \
748 /* prefetch beyond compaction_top */ \
749 Prefetch::write(compaction_top, copy_interval); \
750 \
751 /* copy object and reinit its mark */ \
752 assert(q != compaction_top, "everything in this pass should be moving"); \
753 Copy::aligned_conjoint_words(q, compaction_top, size); \
754 oop(compaction_top)->init_mark(); \
755 assert(oop(compaction_top)->klass() != NULL, "should have a class"); \
756 \
757 debug_only(prev_q = q); \
758 q += size; \
759 } \
760 } \
761 \
762 /* Let's remember if we were empty before we did the compaction. */ \
763 bool was_empty = used_region().is_empty(); \
764 /* Reset space after compaction is complete */ \
765 reset_after_compaction(); \
766 /* We do this clear, below, since it has overloaded meanings for some */ \
767 /* space subtypes. For example, OffsetTableContigSpace's that were */ \
768 /* compacted into will have had their offset table thresholds updated */ \
769 /* continuously, but those that weren't need to have their thresholds */ \
770 /* re-initialized. Also mangles unused area for debugging. */ \
771 if (used_region().is_empty()) { \
772 if (!was_empty) clear(SpaceDecorator::Mangle); \
773 } else { \
774 if (ZapUnusedHeapArea) mangle_unused_area(); \
775 } \
776 }
778 class GenSpaceMangler;
780 // A space in which the free area is contiguous. It therefore supports
781 // faster allocation, and compaction.
782 class ContiguousSpace: public CompactibleSpace {
783 friend class OneContigSpaceCardGeneration;
784 friend class VMStructs;
785 protected:
786 HeapWord* _top;
787 HeapWord* _concurrent_iteration_safe_limit;
788 // A helper for mangling the unused area of the space in debug builds.
789 GenSpaceMangler* _mangler;
791 GenSpaceMangler* mangler() { return _mangler; }
793 // Allocation helpers (return NULL if full).
794 inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
795 inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
797 public:
798 ContiguousSpace();
799 ~ContiguousSpace();
801 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
802 virtual void clear(bool mangle_space);
804 // Accessors
805 HeapWord* top() const { return _top; }
806 void set_top(HeapWord* value) { _top = value; }
808 virtual void set_saved_mark() { _saved_mark_word = top(); }
809 void reset_saved_mark() { _saved_mark_word = bottom(); }
811 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
812 WaterMark top_mark() { return WaterMark(this, top()); }
813 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
814 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
816 // In debug mode mangle (write it with a particular bit
817 // pattern) the unused part of a space.
819 // Used to save the an address in a space for later use during mangling.
820 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
821 // Used to save the space's current top for later use during mangling.
822 void set_top_for_allocations() PRODUCT_RETURN;
824 // Mangle regions in the space from the current top up to the
825 // previously mangled part of the space.
826 void mangle_unused_area() PRODUCT_RETURN;
827 // Mangle [top, end)
828 void mangle_unused_area_complete() PRODUCT_RETURN;
829 // Mangle the given MemRegion.
830 void mangle_region(MemRegion mr) PRODUCT_RETURN;
832 // Do some sparse checking on the area that should have been mangled.
833 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
834 // Check the complete area that should have been mangled.
835 // This code may be NULL depending on the macro DEBUG_MANGLING.
836 void check_mangled_unused_area_complete() PRODUCT_RETURN;
838 // Size computations: sizes in bytes.
839 size_t capacity() const { return byte_size(bottom(), end()); }
840 size_t used() const { return byte_size(bottom(), top()); }
841 size_t free() const { return byte_size(top(), end()); }
843 // Override from space.
844 bool is_in(const void* p) const;
846 virtual bool is_free_block(const HeapWord* p) const;
848 // In a contiguous space we have a more obvious bound on what parts
849 // contain objects.
850 MemRegion used_region() const { return MemRegion(bottom(), top()); }
852 MemRegion used_region_at_save_marks() const {
853 return MemRegion(bottom(), saved_mark_word());
854 }
856 // Allocation (return NULL if full)
857 virtual HeapWord* allocate(size_t word_size);
858 virtual HeapWord* par_allocate(size_t word_size);
860 virtual bool obj_allocated_since_save_marks(const oop obj) const {
861 return (HeapWord*)obj >= saved_mark_word();
862 }
864 // Iteration
865 void oop_iterate(ExtendedOopClosure* cl);
866 void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
867 void object_iterate(ObjectClosure* blk);
868 // For contiguous spaces this method will iterate safely over objects
869 // in the space (i.e., between bottom and top) when at a safepoint.
870 void safe_object_iterate(ObjectClosure* blk);
871 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
872 // iterates on objects up to the safe limit
873 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
874 HeapWord* concurrent_iteration_safe_limit() {
875 assert(_concurrent_iteration_safe_limit <= top(),
876 "_concurrent_iteration_safe_limit update missed");
877 return _concurrent_iteration_safe_limit;
878 }
879 // changes the safe limit, all objects from bottom() to the new
880 // limit should be properly initialized
881 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
882 assert(new_limit <= top(), "uninitialized objects in the safe range");
883 _concurrent_iteration_safe_limit = new_limit;
884 }
887 #if INCLUDE_ALL_GCS
888 // In support of parallel oop_iterate.
889 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
890 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
892 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
893 #undef ContigSpace_PAR_OOP_ITERATE_DECL
894 #endif // INCLUDE_ALL_GCS
896 // Compaction support
897 virtual void reset_after_compaction() {
898 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
899 set_top(compaction_top());
900 // set new iteration safe limit
901 set_concurrent_iteration_safe_limit(compaction_top());
902 }
903 virtual size_t minimum_free_block_size() const { return 0; }
905 // Override.
906 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
907 CardTableModRefBS::PrecisionStyle precision,
908 HeapWord* boundary = NULL);
910 // Apply "blk->do_oop" to the addresses of all reference fields in objects
911 // starting with the _saved_mark_word, which was noted during a generation's
912 // save_marks and is required to denote the head of an object.
913 // Fields in objects allocated by applications of the closure
914 // *are* included in the iteration.
915 // Updates _saved_mark_word to point to just after the last object
916 // iterated over.
917 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
918 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
920 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
921 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
923 // Same as object_iterate, but starting from "mark", which is required
924 // to denote the start of an object. Objects allocated by
925 // applications of the closure *are* included in the iteration.
926 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
928 // Very inefficient implementation.
929 virtual HeapWord* block_start_const(const void* p) const;
930 size_t block_size(const HeapWord* p) const;
931 // If a block is in the allocated area, it is an object.
932 bool block_is_obj(const HeapWord* p) const { return p < top(); }
934 // Addresses for inlined allocation
935 HeapWord** top_addr() { return &_top; }
936 HeapWord** end_addr() { return &_end; }
938 // Overrides for more efficient compaction support.
939 void prepare_for_compaction(CompactPoint* cp);
941 // PrintHeapAtGC support.
942 virtual void print_on(outputStream* st) const;
944 // Checked dynamic downcasts.
945 virtual ContiguousSpace* toContiguousSpace() {
946 return this;
947 }
949 // Debugging
950 virtual void verify() const;
952 // Used to increase collection frequency. "factor" of 0 means entire
953 // space.
954 void allocate_temporary_filler(int factor);
956 };
959 // A dirty card to oop closure that does filtering.
960 // It knows how to filter out objects that are outside of the _boundary.
961 class Filtering_DCTOC : public DirtyCardToOopClosure {
962 protected:
963 // Override.
964 void walk_mem_region(MemRegion mr,
965 HeapWord* bottom, HeapWord* top);
967 // Walk the given memory region, from bottom to top, applying
968 // the given oop closure to (possibly) all objects found. The
969 // given oop closure may or may not be the same as the oop
970 // closure with which this closure was created, as it may
971 // be a filtering closure which makes use of the _boundary.
972 // We offer two signatures, so the FilteringClosure static type is
973 // apparent.
974 virtual void walk_mem_region_with_cl(MemRegion mr,
975 HeapWord* bottom, HeapWord* top,
976 ExtendedOopClosure* cl) = 0;
977 virtual void walk_mem_region_with_cl(MemRegion mr,
978 HeapWord* bottom, HeapWord* top,
979 FilteringClosure* cl) = 0;
981 public:
982 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl,
983 CardTableModRefBS::PrecisionStyle precision,
984 HeapWord* boundary) :
985 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
986 };
988 // A dirty card to oop closure for contiguous spaces
989 // (ContiguousSpace and sub-classes).
990 // It is a FilteringClosure, as defined above, and it knows:
991 //
992 // 1. That the actual top of any area in a memory region
993 // contained by the space is bounded by the end of the contiguous
994 // region of the space.
995 // 2. That the space is really made up of objects and not just
996 // blocks.
998 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
999 protected:
1000 // Overrides.
1001 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
1003 virtual void walk_mem_region_with_cl(MemRegion mr,
1004 HeapWord* bottom, HeapWord* top,
1005 ExtendedOopClosure* cl);
1006 virtual void walk_mem_region_with_cl(MemRegion mr,
1007 HeapWord* bottom, HeapWord* top,
1008 FilteringClosure* cl);
1010 public:
1011 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
1012 CardTableModRefBS::PrecisionStyle precision,
1013 HeapWord* boundary) :
1014 Filtering_DCTOC(sp, cl, precision, boundary)
1015 {}
1016 };
1019 // Class EdenSpace describes eden-space in new generation.
1021 class DefNewGeneration;
1023 class EdenSpace : public ContiguousSpace {
1024 friend class VMStructs;
1025 private:
1026 DefNewGeneration* _gen;
1028 // _soft_end is used as a soft limit on allocation. As soft limits are
1029 // reached, the slow-path allocation code can invoke other actions and then
1030 // adjust _soft_end up to a new soft limit or to end().
1031 HeapWord* _soft_end;
1033 public:
1034 EdenSpace(DefNewGeneration* gen) :
1035 _gen(gen), _soft_end(NULL) {}
1037 // Get/set just the 'soft' limit.
1038 HeapWord* soft_end() { return _soft_end; }
1039 HeapWord** soft_end_addr() { return &_soft_end; }
1040 void set_soft_end(HeapWord* value) { _soft_end = value; }
1042 // Override.
1043 void clear(bool mangle_space);
1045 // Set both the 'hard' and 'soft' limits (_end and _soft_end).
1046 void set_end(HeapWord* value) {
1047 set_soft_end(value);
1048 ContiguousSpace::set_end(value);
1049 }
1051 // Allocation (return NULL if full)
1052 HeapWord* allocate(size_t word_size);
1053 HeapWord* par_allocate(size_t word_size);
1054 };
1056 // Class ConcEdenSpace extends EdenSpace for the sake of safe
1057 // allocation while soft-end is being modified concurrently
1059 class ConcEdenSpace : public EdenSpace {
1060 public:
1061 ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
1063 // Allocation (return NULL if full)
1064 HeapWord* par_allocate(size_t word_size);
1065 };
1068 // A ContigSpace that Supports an efficient "block_start" operation via
1069 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
1070 // other spaces.) This is the abstract base class for old generation
1071 // (tenured) spaces.
1073 class OffsetTableContigSpace: public ContiguousSpace {
1074 friend class VMStructs;
1075 protected:
1076 BlockOffsetArrayContigSpace _offsets;
1077 Mutex _par_alloc_lock;
1079 public:
1080 // Constructor
1081 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
1082 MemRegion mr);
1084 void set_bottom(HeapWord* value);
1085 void set_end(HeapWord* value);
1087 void clear(bool mangle_space);
1089 inline HeapWord* block_start_const(const void* p) const;
1091 // Add offset table update.
1092 virtual inline HeapWord* allocate(size_t word_size);
1093 inline HeapWord* par_allocate(size_t word_size);
1095 // MarkSweep support phase3
1096 virtual HeapWord* initialize_threshold();
1097 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
1099 virtual void print_on(outputStream* st) const;
1101 // Debugging
1102 void verify() const;
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 };
1119 #endif // SHARE_VM_MEMORY_SPACE_HPP