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