Fri, 25 Jan 2013 15:06:18 -0500
6479360: PrintClassHistogram improvements
Summary: jcmd <pid> GC.class_stats (UnlockDiagnosticVMOptions)
Reviewed-by: coleenp, hseigel, sla, acorn
Contributed-by: ioi.lam@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/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
47 #ifdef TARGET_OS_FAMILY_bsd
48 # include "os_bsd.inline.hpp"
49 #endif
51 // A space is an abstraction for the "storage units" backing
52 // up the generation abstraction. It includes specific
53 // implementations for keeping track of free and used space,
54 // for iterating over objects and free blocks, etc.
56 // Here's the Space hierarchy:
57 //
58 // - Space -- an asbtract base class describing a heap area
59 // - CompactibleSpace -- a space supporting compaction
60 // - CompactibleFreeListSpace -- (used for CMS generation)
61 // - ContiguousSpace -- a compactible space in which all free space
62 // is contiguous
63 // - EdenSpace -- contiguous space used as nursery
64 // - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation
65 // - OffsetTableContigSpace -- contiguous space with a block offset array
66 // that allows "fast" block_start calls
67 // - TenuredSpace -- (used for TenuredGeneration)
69 // Forward decls.
70 class Space;
71 class BlockOffsetArray;
72 class BlockOffsetArrayContigSpace;
73 class Generation;
74 class CompactibleSpace;
75 class BlockOffsetTable;
76 class GenRemSet;
77 class CardTableRS;
78 class DirtyCardToOopClosure;
80 // An oop closure that is circumscribed by a filtering memory region.
81 class SpaceMemRegionOopsIterClosure: public ExtendedOopClosure {
82 private:
83 ExtendedOopClosure* _cl;
84 MemRegion _mr;
85 protected:
86 template <class T> void do_oop_work(T* p) {
87 if (_mr.contains(p)) {
88 _cl->do_oop(p);
89 }
90 }
91 public:
92 SpaceMemRegionOopsIterClosure(ExtendedOopClosure* cl, MemRegion mr):
93 _cl(cl), _mr(mr) {}
94 virtual void do_oop(oop* p);
95 virtual void do_oop(narrowOop* p);
96 virtual bool do_metadata() {
97 // _cl is of type ExtendedOopClosure instead of OopClosure, so that we can check this.
98 assert(!_cl->do_metadata(), "I've checked all call paths, this shouldn't happen.");
99 return false;
100 }
101 virtual void do_klass(Klass* k) { ShouldNotReachHere(); }
102 virtual void do_class_loader_data(ClassLoaderData* cld) { ShouldNotReachHere(); }
103 };
105 // A Space describes a heap area. Class Space is an abstract
106 // base class.
107 //
108 // Space supports allocation, size computation and GC support is provided.
109 //
110 // Invariant: bottom() and end() are on page_size boundaries and
111 // bottom() <= top() <= end()
112 // top() is inclusive and end() is exclusive.
114 class Space: public CHeapObj<mtGC> {
115 friend class VMStructs;
116 protected:
117 HeapWord* _bottom;
118 HeapWord* _end;
120 // Used in support of save_marks()
121 HeapWord* _saved_mark_word;
123 MemRegionClosure* _preconsumptionDirtyCardClosure;
125 // A sequential tasks done structure. This supports
126 // parallel GC, where we have threads dynamically
127 // claiming sub-tasks from a larger parallel task.
128 SequentialSubTasksDone _par_seq_tasks;
130 Space():
131 _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { }
133 public:
134 // Accessors
135 HeapWord* bottom() const { return _bottom; }
136 HeapWord* end() const { return _end; }
137 virtual void set_bottom(HeapWord* value) { _bottom = value; }
138 virtual void set_end(HeapWord* value) { _end = value; }
140 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
142 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
144 MemRegionClosure* preconsumptionDirtyCardClosure() const {
145 return _preconsumptionDirtyCardClosure;
146 }
147 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
148 _preconsumptionDirtyCardClosure = cl;
149 }
151 // Returns a subregion of the space containing all the objects in
152 // the space.
153 virtual MemRegion used_region() const { return MemRegion(bottom(), end()); }
155 // Returns a region that is guaranteed to contain (at least) all objects
156 // allocated at the time of the last call to "save_marks". If the space
157 // initializes its DirtyCardToOopClosure's specifying the "contig" option
158 // (that is, if the space is contiguous), then this region must contain only
159 // such objects: the memregion will be from the bottom of the region to the
160 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
161 // the space must distiguish between objects in the region allocated before
162 // and after the call to save marks.
163 virtual MemRegion used_region_at_save_marks() const {
164 return MemRegion(bottom(), saved_mark_word());
165 }
167 // Initialization.
168 // "initialize" should be called once on a space, before it is used for
169 // any purpose. The "mr" arguments gives the bounds of the space, and
170 // the "clear_space" argument should be true unless the memory in "mr" is
171 // known to be zeroed.
172 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
174 // The "clear" method must be called on a region that may have
175 // had allocation performed in it, but is now to be considered empty.
176 virtual void clear(bool mangle_space);
178 // For detecting GC bugs. Should only be called at GC boundaries, since
179 // some unused space may be used as scratch space during GC's.
180 // Default implementation does nothing. We also call this when expanding
181 // a space to satisfy an allocation request. See bug #4668531
182 virtual void mangle_unused_area() {}
183 virtual void mangle_unused_area_complete() {}
184 virtual void mangle_region(MemRegion mr) {}
186 // Testers
187 bool is_empty() const { return used() == 0; }
188 bool not_empty() const { return used() > 0; }
190 // Returns true iff the given the space contains the
191 // given address as part of an allocated object. For
192 // ceratin kinds of spaces, this might be a potentially
193 // expensive operation. To prevent performance problems
194 // on account of its inadvertent use in product jvm's,
195 // we restrict its use to assertion checks only.
196 virtual bool is_in(const void* p) const = 0;
198 // Returns true iff the given reserved memory of the space contains the
199 // given address.
200 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
202 // Returns true iff the given block is not allocated.
203 virtual bool is_free_block(const HeapWord* p) const = 0;
205 // Test whether p is double-aligned
206 static bool is_aligned(void* p) {
207 return ((intptr_t)p & (sizeof(double)-1)) == 0;
208 }
210 // Size computations. Sizes are in bytes.
211 size_t capacity() const { return byte_size(bottom(), end()); }
212 virtual size_t used() const = 0;
213 virtual size_t free() const = 0;
215 // Iterate over all the ref-containing fields of all objects in the
216 // space, calling "cl.do_oop" on each. Fields in objects allocated by
217 // applications of the closure are not included in the iteration.
218 virtual void oop_iterate(ExtendedOopClosure* cl);
220 // Same as above, restricted to the intersection of a memory region and
221 // the space. Fields in objects allocated by applications of the closure
222 // are not included in the iteration.
223 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl) = 0;
225 // Iterate over all objects in the space, calling "cl.do_object" on
226 // each. Objects allocated by applications of the closure are not
227 // included in the iteration.
228 virtual void object_iterate(ObjectClosure* blk) = 0;
229 // Similar to object_iterate() except only iterates over
230 // objects whose internal references point to objects in the space.
231 virtual void safe_object_iterate(ObjectClosure* blk) = 0;
233 // Iterate over all objects that intersect with mr, calling "cl->do_object"
234 // on each. There is an exception to this: if this closure has already
235 // been invoked on an object, it may skip such objects in some cases. This is
236 // Most likely to happen in an "upwards" (ascending address) iteration of
237 // MemRegions.
238 virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
240 // Iterate over as many initialized objects in the space as possible,
241 // calling "cl.do_object_careful" on each. Return NULL if all objects
242 // in the space (at the start of the iteration) were iterated over.
243 // Return an address indicating the extent of the iteration in the
244 // event that the iteration had to return because of finding an
245 // uninitialized object in the space, or if the closure "cl"
246 // signalled early termination.
247 virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
248 virtual HeapWord* object_iterate_careful_m(MemRegion mr,
249 ObjectClosureCareful* cl);
251 // Create and return a new dirty card to oop closure. Can be
252 // overriden to return the appropriate type of closure
253 // depending on the type of space in which the closure will
254 // operate. ResourceArea allocated.
255 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
256 CardTableModRefBS::PrecisionStyle precision,
257 HeapWord* boundary = NULL);
259 // If "p" is in the space, returns the address of the start of the
260 // "block" that contains "p". We say "block" instead of "object" since
261 // some heaps may not pack objects densely; a chunk may either be an
262 // object or a non-object. If "p" is not in the space, return NULL.
263 virtual HeapWord* block_start_const(const void* p) const = 0;
265 // The non-const version may have benevolent side effects on the data
266 // structure supporting these calls, possibly speeding up future calls.
267 // The default implementation, however, is simply to call the const
268 // version.
269 inline virtual HeapWord* block_start(const void* p);
271 // Requires "addr" to be the start of a chunk, and returns its size.
272 // "addr + size" is required to be the start of a new chunk, or the end
273 // of the active area of the heap.
274 virtual size_t block_size(const HeapWord* addr) const = 0;
276 // Requires "addr" to be the start of a block, and returns "TRUE" iff
277 // the block is an object.
278 virtual bool block_is_obj(const HeapWord* addr) const = 0;
280 // Requires "addr" to be the start of a block, and returns "TRUE" iff
281 // the block is an object and the object is alive.
282 virtual bool obj_is_alive(const HeapWord* addr) const;
284 // Allocation (return NULL if full). Assumes the caller has established
285 // mutually exclusive access to the space.
286 virtual HeapWord* allocate(size_t word_size) = 0;
288 // Allocation (return NULL if full). Enforces mutual exclusion internally.
289 virtual HeapWord* par_allocate(size_t word_size) = 0;
291 // Returns true if this object has been allocated since a
292 // generation's "save_marks" call.
293 virtual bool obj_allocated_since_save_marks(const oop obj) const = 0;
295 // Mark-sweep-compact support: all spaces can update pointers to objects
296 // moving as a part of compaction.
297 virtual void adjust_pointers();
299 // PrintHeapAtGC support
300 virtual void print() const;
301 virtual void print_on(outputStream* st) const;
302 virtual void print_short() const;
303 virtual void print_short_on(outputStream* st) const;
306 // Accessor for parallel sequential tasks.
307 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
309 // IF "this" is a ContiguousSpace, return it, else return NULL.
310 virtual ContiguousSpace* toContiguousSpace() {
311 return NULL;
312 }
314 // Debugging
315 virtual void verify() const = 0;
316 };
318 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
319 // OopClosure to (the addresses of) all the ref-containing fields that could
320 // be modified by virtue of the given MemRegion being dirty. (Note that
321 // because of the imprecise nature of the write barrier, this may iterate
322 // over oops beyond the region.)
323 // This base type for dirty card to oop closures handles memory regions
324 // in non-contiguous spaces with no boundaries, and should be sub-classed
325 // to support other space types. See ContiguousDCTOC for a sub-class
326 // that works with ContiguousSpaces.
328 class DirtyCardToOopClosure: public MemRegionClosureRO {
329 protected:
330 ExtendedOopClosure* _cl;
331 Space* _sp;
332 CardTableModRefBS::PrecisionStyle _precision;
333 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
334 // pointing below boundary.
335 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
336 // a downwards traversal; this is the
337 // lowest location already done (or,
338 // alternatively, the lowest address that
339 // shouldn't be done again. NULL means infinity.)
340 NOT_PRODUCT(HeapWord* _last_bottom;)
341 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
343 // Get the actual top of the area on which the closure will
344 // operate, given where the top is assumed to be (the end of the
345 // memory region passed to do_MemRegion) and where the object
346 // at the top is assumed to start. For example, an object may
347 // start at the top but actually extend past the assumed top,
348 // in which case the top becomes the end of the object.
349 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
351 // Walk the given memory region from bottom to (actual) top
352 // looking for objects and applying the oop closure (_cl) to
353 // them. The base implementation of this treats the area as
354 // blocks, where a block may or may not be an object. Sub-
355 // classes should override this to provide more accurate
356 // or possibly more efficient walking.
357 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
359 public:
360 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl,
361 CardTableModRefBS::PrecisionStyle precision,
362 HeapWord* boundary) :
363 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
364 _min_done(NULL) {
365 NOT_PRODUCT(_last_bottom = NULL);
366 NOT_PRODUCT(_last_explicit_min_done = NULL);
367 }
369 void do_MemRegion(MemRegion mr);
371 void set_min_done(HeapWord* min_done) {
372 _min_done = min_done;
373 NOT_PRODUCT(_last_explicit_min_done = _min_done);
374 }
375 #ifndef PRODUCT
376 void set_last_bottom(HeapWord* last_bottom) {
377 _last_bottom = last_bottom;
378 }
379 #endif
380 };
382 // A structure to represent a point at which objects are being copied
383 // during compaction.
384 class CompactPoint : public StackObj {
385 public:
386 Generation* gen;
387 CompactibleSpace* space;
388 HeapWord* threshold;
389 CompactPoint(Generation* _gen, CompactibleSpace* _space,
390 HeapWord* _threshold) :
391 gen(_gen), space(_space), threshold(_threshold) {}
392 };
395 // A space that supports compaction operations. This is usually, but not
396 // necessarily, a space that is normally contiguous. But, for example, a
397 // free-list-based space whose normal collection is a mark-sweep without
398 // compaction could still support compaction in full GC's.
400 class CompactibleSpace: public Space {
401 friend class VMStructs;
402 friend class CompactibleFreeListSpace;
403 private:
404 HeapWord* _compaction_top;
405 CompactibleSpace* _next_compaction_space;
407 public:
408 CompactibleSpace() :
409 _compaction_top(NULL), _next_compaction_space(NULL) {}
411 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
412 virtual void clear(bool mangle_space);
414 // Used temporarily during a compaction phase to hold the value
415 // top should have when compaction is complete.
416 HeapWord* compaction_top() const { return _compaction_top; }
418 void set_compaction_top(HeapWord* value) {
419 assert(value == NULL || (value >= bottom() && value <= end()),
420 "should point inside space");
421 _compaction_top = value;
422 }
424 // Perform operations on the space needed after a compaction
425 // has been performed.
426 virtual void reset_after_compaction() {}
428 // Returns the next space (in the current generation) to be compacted in
429 // the global compaction order. Also is used to select the next
430 // space into which to compact.
432 virtual CompactibleSpace* next_compaction_space() const {
433 return _next_compaction_space;
434 }
436 void set_next_compaction_space(CompactibleSpace* csp) {
437 _next_compaction_space = csp;
438 }
440 // MarkSweep support phase2
442 // Start the process of compaction of the current space: compute
443 // post-compaction addresses, and insert forwarding pointers. The fields
444 // "cp->gen" and "cp->compaction_space" are the generation and space into
445 // which we are currently compacting. This call updates "cp" as necessary,
446 // and leaves the "compaction_top" of the final value of
447 // "cp->compaction_space" up-to-date. Offset tables may be updated in
448 // this phase as if the final copy had occurred; if so, "cp->threshold"
449 // indicates when the next such action should be taken.
450 virtual void prepare_for_compaction(CompactPoint* cp);
451 // MarkSweep support phase3
452 virtual void adjust_pointers();
453 // MarkSweep support phase4
454 virtual void compact();
456 // The maximum percentage of objects that can be dead in the compacted
457 // live part of a compacted space ("deadwood" support.)
458 virtual size_t allowed_dead_ratio() const { return 0; };
460 // Some contiguous spaces may maintain some data structures that should
461 // be updated whenever an allocation crosses a boundary. This function
462 // returns the first such boundary.
463 // (The default implementation returns the end of the space, so the
464 // boundary is never crossed.)
465 virtual HeapWord* initialize_threshold() { return end(); }
467 // "q" is an object of the given "size" that should be forwarded;
468 // "cp" names the generation ("gen") and containing "this" (which must
469 // also equal "cp->space"). "compact_top" is where in "this" the
470 // next object should be forwarded to. If there is room in "this" for
471 // the object, insert an appropriate forwarding pointer in "q".
472 // If not, go to the next compaction space (there must
473 // be one, since compaction must succeed -- we go to the first space of
474 // the previous generation if necessary, updating "cp"), reset compact_top
475 // and then forward. In either case, returns the new value of "compact_top".
476 // If the forwarding crosses "cp->threshold", invokes the "cross_threhold"
477 // function of the then-current compaction space, and updates "cp->threshold
478 // accordingly".
479 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
480 HeapWord* compact_top);
482 // Return a size with adjusments as required of the space.
483 virtual size_t adjust_object_size_v(size_t size) const { return size; }
485 protected:
486 // Used during compaction.
487 HeapWord* _first_dead;
488 HeapWord* _end_of_live;
490 // Minimum size of a free block.
491 virtual size_t minimum_free_block_size() const = 0;
493 // This the function is invoked when an allocation of an object covering
494 // "start" to "end occurs crosses the threshold; returns the next
495 // threshold. (The default implementation does nothing.)
496 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
497 return end();
498 }
500 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
501 // free block of the given "word_len", and that "q", were it an object,
502 // would not move if forwared. If the size allows, fill the free
503 // block with an object, to prevent excessive compaction. Returns "true"
504 // iff the free region was made deadspace, and modifies
505 // "allowed_deadspace_words" to reflect the number of available deadspace
506 // words remaining after this operation.
507 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
508 size_t word_len);
509 };
511 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) { \
512 /* Compute the new addresses for the live objects and store it in the mark \
513 * Used by universe::mark_sweep_phase2() \
514 */ \
515 HeapWord* compact_top; /* This is where we are currently compacting to. */ \
516 \
517 /* We're sure to be here before any objects are compacted into this \
518 * space, so this is a good time to initialize this: \
519 */ \
520 set_compaction_top(bottom()); \
521 \
522 if (cp->space == NULL) { \
523 assert(cp->gen != NULL, "need a generation"); \
524 assert(cp->threshold == NULL, "just checking"); \
525 assert(cp->gen->first_compaction_space() == this, "just checking"); \
526 cp->space = cp->gen->first_compaction_space(); \
527 compact_top = cp->space->bottom(); \
528 cp->space->set_compaction_top(compact_top); \
529 cp->threshold = cp->space->initialize_threshold(); \
530 } else { \
531 compact_top = cp->space->compaction_top(); \
532 } \
533 \
534 /* We allow some amount of garbage towards the bottom of the space, so \
535 * we don't start compacting before there is a significant gain to be made.\
536 * Occasionally, we want to ensure a full compaction, which is determined \
537 * by the MarkSweepAlwaysCompactCount parameter. \
538 */ \
539 int invocations = MarkSweep::total_invocations(); \
540 bool skip_dead = (MarkSweepAlwaysCompactCount < 1) \
541 ||((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 #ifndef SERIALGC
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 // SERIALGC
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