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24
25 #ifndef SHARE_GC_SHARED_SPACE_HPP
26 #define SHARE_GC_SHARED_SPACE_HPP
27
28 #include "gc/shared/blockOffsetTable.hpp"
29 #include "gc/shared/cardTable.hpp"
30 #include "gc/shared/workerThread.hpp"
31 #include "memory/allocation.hpp"
32 #include "memory/iterator.hpp"
33 #include "memory/memRegion.hpp"
34 #include "oops/markWord.hpp"
35 #include "runtime/mutexLocker.hpp"
36 #include "utilities/align.hpp"
37 #include "utilities/macros.hpp"
38 #if INCLUDE_SERIALGC
39 #include "gc/serial/serialBlockOffsetTable.hpp"
40 #endif
41
42 // A space is an abstraction for the "storage units" backing
43 // up the generation abstraction. It includes specific
44 // implementations for keeping track of free and used space,
45 // for iterating over objects and free blocks, etc.
46
47 // Forward decls.
48 class Space;
49 class ContiguousSpace;
50 #if INCLUDE_SERIALGC
51 class BlockOffsetArray;
52 class BlockOffsetArrayContigSpace;
53 class BlockOffsetTable;
54 #endif
55 class Generation;
56 class CompactibleSpace;
57 class CardTableRS;
58 class DirtyCardToOopClosure;
59 class SlidingForwarding;
60 class FilteringClosure;
61
62 // A Space describes a heap area. Class Space is an abstract
63 // base class.
64 //
65 // Space supports allocation, size computation and GC support is provided.
66 //
67 // Invariant: bottom() and end() are on page_size boundaries and
68 // bottom() <= top() <= end()
69 // top() is inclusive and end() is exclusive.
70
71 class Space: public CHeapObj<mtGC> {
72 friend class VMStructs;
73 protected:
74 HeapWord* _bottom;
75 HeapWord* _end;
76
77 // Used in support of save_marks()
78 HeapWord* _saved_mark_word;
79
80 Space():
81 _bottom(nullptr), _end(nullptr) { }
82
83 public:
84 // Accessors
85 HeapWord* bottom() const { return _bottom; }
86 HeapWord* end() const { return _end; }
87 virtual void set_bottom(HeapWord* value) { _bottom = value; }
88 virtual void set_end(HeapWord* value) { _end = value; }
89
90 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
91
92 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
93
94 // Returns true if this object has been allocated since a
95 // generation's "save_marks" call.
96 virtual bool obj_allocated_since_save_marks(const oop obj) const {
97 return cast_from_oop<HeapWord*>(obj) >= saved_mark_word();
98 }
99
100 // Returns a subregion of the space containing only the allocated objects in
101 // the space.
102 virtual MemRegion used_region() const = 0;
103
104 // Returns a region that is guaranteed to contain (at least) all objects
105 // allocated at the time of the last call to "save_marks". If the space
106 // initializes its DirtyCardToOopClosure's specifying the "contig" option
107 // (that is, if the space is contiguous), then this region must contain only
108 // such objects: the memregion will be from the bottom of the region to the
109 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
110 // the space must distinguish between objects in the region allocated before
111 // and after the call to save marks.
112 MemRegion used_region_at_save_marks() const {
113 return MemRegion(bottom(), saved_mark_word());
114 }
115
116 // Initialization.
117 // "initialize" should be called once on a space, before it is used for
118 // any purpose. The "mr" arguments gives the bounds of the space, and
119 // the "clear_space" argument should be true unless the memory in "mr" is
120 // known to be zeroed.
121 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
122
123 // The "clear" method must be called on a region that may have
124 // had allocation performed in it, but is now to be considered empty.
125 virtual void clear(bool mangle_space);
126
127 // For detecting GC bugs. Should only be called at GC boundaries, since
128 // some unused space may be used as scratch space during GC's.
129 // We also call this when expanding a space to satisfy an allocation
130 // request. See bug #4668531
131 virtual void mangle_unused_area() = 0;
132 virtual void mangle_unused_area_complete() = 0;
133
134 // Testers
135 bool is_empty() const { return used() == 0; }
136
137 // Returns true iff the given the space contains the
138 // given address as part of an allocated object. For
139 // certain kinds of spaces, this might be a potentially
140 // expensive operation. To prevent performance problems
141 // on account of its inadvertent use in product jvm's,
142 // we restrict its use to assertion checks only.
143 bool is_in(const void* p) const {
144 return used_region().contains(p);
145 }
146 bool is_in(oop obj) const {
147 return is_in((void*)obj);
148 }
149
150 // Returns true iff the given reserved memory of the space contains the
151 // given address.
152 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
153
154 // Returns true iff the given block is not allocated.
155 virtual bool is_free_block(const HeapWord* p) const = 0;
156
157 // Test whether p is double-aligned
158 static bool is_aligned(void* p) {
159 return ::is_aligned(p, sizeof(double));
160 }
161
162 // Size computations. Sizes are in bytes.
163 size_t capacity() const { return byte_size(bottom(), end()); }
164 virtual size_t used() const = 0;
165 virtual size_t free() const = 0;
166
167 // Iterate over all the ref-containing fields of all objects in the
168 // space, calling "cl.do_oop" on each. Fields in objects allocated by
169 // applications of the closure are not included in the iteration.
170 virtual void oop_iterate(OopIterateClosure* cl);
171
172 // Iterate over all objects in the space, calling "cl.do_object" on
173 // each. Objects allocated by applications of the closure are not
174 // included in the iteration.
175 virtual void object_iterate(ObjectClosure* blk) = 0;
176
177 // If "p" is in the space, returns the address of the start of the
178 // "block" that contains "p". We say "block" instead of "object" since
179 // some heaps may not pack objects densely; a chunk may either be an
180 // object or a non-object. If "p" is not in the space, return null.
181 virtual HeapWord* block_start_const(const void* p) const = 0;
182
183 // The non-const version may have benevolent side effects on the data
184 // structure supporting these calls, possibly speeding up future calls.
185 // The default implementation, however, is simply to call the const
186 // version.
187 virtual HeapWord* block_start(const void* p);
188
189 // Requires "addr" to be the start of a chunk, and returns its size.
190 // "addr + size" is required to be the start of a new chunk, or the end
191 // of the active area of the heap.
192 virtual size_t block_size(const HeapWord* addr) const = 0;
193
194 // Requires "addr" to be the start of a block, and returns "TRUE" iff
195 // the block is an object.
196 virtual bool block_is_obj(const HeapWord* addr) const = 0;
197
198 // Requires "addr" to be the start of a block, and returns "TRUE" iff
199 // the block is an object and the object is alive.
200 virtual bool obj_is_alive(const HeapWord* addr) const;
201
202 // Allocation (return null if full). Assumes the caller has established
203 // mutually exclusive access to the space.
204 virtual HeapWord* allocate(size_t word_size) = 0;
205
206 // Allocation (return null if full). Enforces mutual exclusion internally.
207 virtual HeapWord* par_allocate(size_t word_size) = 0;
208
209 #if INCLUDE_SERIALGC
210 // Mark-sweep-compact support: all spaces can update pointers to objects
211 // moving as a part of compaction.
212 virtual void adjust_pointers() = 0;
213 #endif
214
215 virtual void print() const;
216 virtual void print_on(outputStream* st) const;
217 virtual void print_short() const;
218 virtual void print_short_on(outputStream* st) const;
219
220
221 // IF "this" is a ContiguousSpace, return it, else return null.
222 virtual ContiguousSpace* toContiguousSpace() {
223 return nullptr;
224 }
225
226 // Debugging
227 virtual void verify() const = 0;
228 };
229
230 // A dirty card to oop closure for contiguous spaces (ContiguousSpace and
231 // sub-classes). It knows how to filter out objects that are outside of the
232 // _boundary.
233 // (Note that because of the imprecise nature of the write barrier, this may
234 // iterate over oops beyond the region.)
235 //
236 // Assumptions:
237 // 1. That the actual top of any area in a memory region
238 // contained by the space is bounded by the end of the contiguous
239 // region of the space.
240 // 2. That the space is really made up of objects and not just
241 // blocks.
242
243 class DirtyCardToOopClosure: public MemRegionClosure {
244 protected:
245 OopIterateClosure* _cl;
246 Space* _sp;
247 HeapWord* _min_done; // Need a downwards traversal to compensate
248 // imprecise write barrier; this is the
249 // lowest location already done (or,
250 // alternatively, the lowest address that
251 // shouldn't be done again. null means infinity.)
252 NOT_PRODUCT(HeapWord* _last_bottom;)
253
254 // Get the actual top of the area on which the closure will
255 // operate, given where the top is assumed to be (the end of the
256 // memory region passed to do_MemRegion) and where the object
257 // at the top is assumed to start. For example, an object may
258 // start at the top but actually extend past the assumed top,
259 // in which case the top becomes the end of the object.
260 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
261
262 // Walk the given memory region from bottom to (actual) top
263 // looking for objects and applying the oop closure (_cl) to
264 // them. The base implementation of this treats the area as
265 // blocks, where a block may or may not be an object. Sub-
266 // classes should override this to provide more accurate
267 // or possibly more efficient walking.
268 void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
269
270 // Walk the given memory region, from bottom to top, applying
271 // the given oop closure to (possibly) all objects found. The
272 // given oop closure may or may not be the same as the oop
273 // closure with which this closure was created, as it may
274 // be a filtering closure which makes use of the _boundary.
275 // We offer two signatures, so the FilteringClosure static type is
276 // apparent.
277 void walk_mem_region_with_cl(MemRegion mr,
278 HeapWord* bottom, HeapWord* top,
279 OopIterateClosure* cl);
280 public:
281 DirtyCardToOopClosure(Space* sp, OopIterateClosure* cl) :
282 _cl(cl), _sp(sp), _min_done(nullptr) {
283 NOT_PRODUCT(_last_bottom = nullptr);
284 }
285
286 void do_MemRegion(MemRegion mr) override;
287 };
288
289 // A structure to represent a point at which objects are being copied
290 // during compaction.
291 class CompactPoint : public StackObj {
292 public:
293 Generation* gen;
294 CompactibleSpace* space;
295
296 CompactPoint(Generation* g = nullptr) :
297 gen(g), space(nullptr) {}
298 };
299
300 // A space that supports compaction operations. This is usually, but not
301 // necessarily, a space that is normally contiguous. But, for example, a
302 // free-list-based space whose normal collection is a mark-sweep without
303 // compaction could still support compaction in full GC's.
304 class CompactibleSpace: public Space {
305 friend class VMStructs;
306 private:
307 HeapWord* _compaction_top;
308 CompactibleSpace* _next_compaction_space;
309
310 template <class SpaceType>
311 static inline void verify_up_to_first_dead(SpaceType* space) NOT_DEBUG_RETURN;
312
313 template <class SpaceType>
314 static inline void clear_empty_region(SpaceType* space);
315
316 public:
317 CompactibleSpace() :
318 _compaction_top(nullptr), _next_compaction_space(nullptr) {}
319
320 void initialize(MemRegion mr, bool clear_space, bool mangle_space) override;
321 void clear(bool mangle_space) override;
322
323 // Used temporarily during a compaction phase to hold the value
324 // top should have when compaction is complete.
325 HeapWord* compaction_top() const { return _compaction_top; }
326
327 void set_compaction_top(HeapWord* value) {
328 assert(value == nullptr || (value >= bottom() && value <= end()),
329 "should point inside space");
330 _compaction_top = value;
331 }
332
333 // Perform operations on the space needed after a compaction
334 // has been performed.
335 virtual void reset_after_compaction() = 0;
336
337 // Returns the next space (in the current generation) to be compacted in
338 // the global compaction order. Also is used to select the next
339 // space into which to compact.
340
341 virtual CompactibleSpace* next_compaction_space() const {
342 return _next_compaction_space;
343 }
344
345 void set_next_compaction_space(CompactibleSpace* csp) {
346 _next_compaction_space = csp;
347 }
348
349 #if INCLUDE_SERIALGC
350 // MarkSweep support phase2
351
352 // Start the process of compaction of the current space: compute
353 // post-compaction addresses, and insert forwarding pointers. The fields
354 // "cp->gen" and "cp->compaction_space" are the generation and space into
355 // which we are currently compacting. This call updates "cp" as necessary,
356 // and leaves the "compaction_top" of the final value of
357 // "cp->compaction_space" up-to-date. Offset tables may be updated in
358 // this phase as if the final copy had occurred; if so, "cp->threshold"
359 // indicates when the next such action should be taken.
360 virtual void prepare_for_compaction(CompactPoint* cp) = 0;
361 // MarkSweep support phase3
362 void adjust_pointers() override;
363 // MarkSweep support phase4
364 virtual void compact();
365 #endif // INCLUDE_SERIALGC
366
367 // The maximum percentage of objects that can be dead in the compacted
368 // live part of a compacted space ("deadwood" support.)
369 virtual size_t allowed_dead_ratio() const { return 0; };
370
371 // Some contiguous spaces may maintain some data structures that should
372 // be updated whenever an allocation crosses a boundary. This function
373 // initializes these data structures for further updates.
374 virtual void initialize_threshold() { }
375
376 // "q" is an object of the given "size" that should be forwarded;
377 // "cp" names the generation ("gen") and containing "this" (which must
378 // also equal "cp->space"). "compact_top" is where in "this" the
379 // next object should be forwarded to. If there is room in "this" for
380 // the object, insert an appropriate forwarding pointer in "q".
381 // If not, go to the next compaction space (there must
382 // be one, since compaction must succeed -- we go to the first space of
383 // the previous generation if necessary, updating "cp"), reset compact_top
384 // and then forward. In either case, returns the new value of "compact_top".
385 // Invokes the "alloc_block" function of the then-current compaction
386 // space.
387 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
388 HeapWord* compact_top, SlidingForwarding* const forwarding);
389 protected:
390 // Used during compaction.
391 HeapWord* _first_dead;
392 HeapWord* _end_of_live;
393
394 // This the function to invoke when an allocation of an object covering
395 // "start" to "end" occurs to update other internal data structures.
396 virtual void alloc_block(HeapWord* start, HeapWord* the_end) { }
397 };
398
399 class GenSpaceMangler;
400
401 // A space in which the free area is contiguous. It therefore supports
402 // faster allocation, and compaction.
403 class ContiguousSpace: public CompactibleSpace {
404 friend class VMStructs;
405
406 protected:
407 HeapWord* _top;
408 // A helper for mangling the unused area of the space in debug builds.
409 GenSpaceMangler* _mangler;
410
411 GenSpaceMangler* mangler() { return _mangler; }
412
413 // Allocation helpers (return null if full).
414 inline HeapWord* allocate_impl(size_t word_size);
415 inline HeapWord* par_allocate_impl(size_t word_size);
416
417 public:
418 ContiguousSpace();
419 ~ContiguousSpace();
420
421 void initialize(MemRegion mr, bool clear_space, bool mangle_space) override;
422 void clear(bool mangle_space) override;
423
424 // Accessors
425 HeapWord* top() const { return _top; }
426 void set_top(HeapWord* value) { _top = value; }
427
428 void set_saved_mark() { _saved_mark_word = top(); }
429
430 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
431
432 // In debug mode mangle (write it with a particular bit
433 // pattern) the unused part of a space.
434
435 // Used to save the address in a space for later use during mangling.
436 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
437 // Used to save the space's current top for later use during mangling.
438 void set_top_for_allocations() PRODUCT_RETURN;
439
440 // Mangle regions in the space from the current top up to the
441 // previously mangled part of the space.
442 void mangle_unused_area() override PRODUCT_RETURN;
443 // Mangle [top, end)
444 void mangle_unused_area_complete() override PRODUCT_RETURN;
445
446 // Do some sparse checking on the area that should have been mangled.
447 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
448 // Check the complete area that should have been mangled.
449 // This code may be null depending on the macro DEBUG_MANGLING.
450 void check_mangled_unused_area_complete() PRODUCT_RETURN;
451
452 // Size computations: sizes in bytes.
453 size_t used() const override { return byte_size(bottom(), top()); }
454 size_t free() const override { return byte_size(top(), end()); }
455
456 bool is_free_block(const HeapWord* p) const override;
457
458 // In a contiguous space we have a more obvious bound on what parts
459 // contain objects.
460 MemRegion used_region() const override { return MemRegion(bottom(), top()); }
461
462 // Allocation (return null if full)
463 HeapWord* allocate(size_t word_size) override;
464 HeapWord* par_allocate(size_t word_size) override;
465
466 // Iteration
467 void oop_iterate(OopIterateClosure* cl) override;
468 void object_iterate(ObjectClosure* blk) override;
469
470 // Compaction support
471 void reset_after_compaction() override {
472 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
473 set_top(compaction_top());
474 }
475
476 // Apply "blk->do_oop" to the addresses of all reference fields in objects
477 // starting with the _saved_mark_word, which was noted during a generation's
478 // save_marks and is required to denote the head of an object.
479 // Fields in objects allocated by applications of the closure
480 // *are* included in the iteration.
481 // Updates _saved_mark_word to point to just after the last object
482 // iterated over.
483 template <typename OopClosureType>
484 void oop_since_save_marks_iterate(OopClosureType* blk);
485
486 // Same as object_iterate, but starting from "mark", which is required
487 // to denote the start of an object. Objects allocated by
488 // applications of the closure *are* included in the iteration.
489 virtual void object_iterate_from(HeapWord* mark, ObjectClosure* blk);
490
491 // Very inefficient implementation.
492 HeapWord* block_start_const(const void* p) const override;
493 size_t block_size(const HeapWord* p) const override;
494 // If a block is in the allocated area, it is an object.
495 bool block_is_obj(const HeapWord* p) const override { return p < top(); }
496
497 // Addresses for inlined allocation
498 HeapWord** top_addr() { return &_top; }
499 HeapWord** end_addr() { return &_end; }
500
501 #if INCLUDE_SERIALGC
502 // Overrides for more efficient compaction support.
503 void prepare_for_compaction(CompactPoint* cp) override;
504 #endif
505
506 void print_on(outputStream* st) const override;
507
508 // Checked dynamic downcasts.
509 ContiguousSpace* toContiguousSpace() override {
510 return this;
511 }
512
513 // Debugging
514 void verify() const override;
515 };
516
517 #if INCLUDE_SERIALGC
518
519 // Class TenuredSpace is used by TenuredGeneration; it supports an efficient
520 // "block_start" operation via a BlockOffsetArray (whose BlockOffsetSharedArray
521 // may be shared with other spaces.)
522
523 class TenuredSpace: public ContiguousSpace {
524 friend class VMStructs;
525 protected:
526 BlockOffsetArrayContigSpace _offsets;
527 Mutex _par_alloc_lock;
528
529 // Mark sweep support
530 size_t allowed_dead_ratio() const override;
531 public:
532 // Constructor
533 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
534 MemRegion mr);
535
536 void set_bottom(HeapWord* value) override;
537 void set_end(HeapWord* value) override;
538
539 void clear(bool mangle_space) override;
540
541 inline HeapWord* block_start_const(const void* p) const override;
542
543 // Add offset table update.
544 inline HeapWord* allocate(size_t word_size) override;
545 inline HeapWord* par_allocate(size_t word_size) override;
546
547 // MarkSweep support phase3
548 void initialize_threshold() override;
549 void alloc_block(HeapWord* start, HeapWord* end) override;
550
551 void print_on(outputStream* st) const override;
552
553 // Debugging
554 void verify() const override;
555 };
556 #endif //INCLUDE_SERIALGC
557
558 #endif // SHARE_GC_SHARED_SPACE_HPP