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 class Generation;
51 class ContiguousSpace;
52 class CardTableRS;
53 class DirtyCardToOopClosure;
54 class FilteringClosure;
55
56 // A Space describes a heap area. Class Space is an abstract
57 // base class.
58 //
59 // Space supports allocation, size computation and GC support is provided.
60 //
61 // Invariant: bottom() and end() are on page_size boundaries and
62 // bottom() <= top() <= end()
63 // top() is inclusive and end() is exclusive.
64
65 class Space: public CHeapObj<mtGC> {
66 friend class VMStructs;
67 protected:
68 HeapWord* _bottom;
69 HeapWord* _end;
70
71 // Used in support of save_marks()
72 HeapWord* _saved_mark_word;
73
74 Space():
75 _bottom(nullptr), _end(nullptr) { }
76
77 public:
78 // Accessors
79 HeapWord* bottom() const { return _bottom; }
80 HeapWord* end() const { return _end; }
81 virtual void set_bottom(HeapWord* value) { _bottom = value; }
82 virtual void set_end(HeapWord* value) { _end = value; }
83
84 HeapWord* saved_mark_word() const { return _saved_mark_word; }
85
86 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
87
88 // Returns true if this object has been allocated since a
89 // generation's "save_marks" call.
90 bool obj_allocated_since_save_marks(const oop obj) const {
91 return cast_from_oop<HeapWord*>(obj) >= saved_mark_word();
92 }
93
94 // Returns a subregion of the space containing only the allocated objects in
95 // the space.
96 virtual MemRegion used_region() const = 0;
97
98 // Returns a region that is guaranteed to contain (at least) all objects
99 // allocated at the time of the last call to "save_marks". If the space
100 // initializes its DirtyCardToOopClosure's specifying the "contig" option
101 // (that is, if the space is contiguous), then this region must contain only
102 // such objects: the memregion will be from the bottom of the region to the
103 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
104 // the space must distinguish between objects in the region allocated before
105 // and after the call to save marks.
106 MemRegion used_region_at_save_marks() const {
107 return MemRegion(bottom(), saved_mark_word());
108 }
109
110 // For detecting GC bugs. Should only be called at GC boundaries, since
111 // some unused space may be used as scratch space during GC's.
112 // We also call this when expanding a space to satisfy an allocation
113 // request. See bug #4668531
114 virtual void mangle_unused_area() = 0;
115 virtual void mangle_unused_area_complete() = 0;
116
117 // Testers
118 bool is_empty() const { return used() == 0; }
119
120 // Returns true iff the given the space contains the
121 // given address as part of an allocated object. For
122 // certain kinds of spaces, this might be a potentially
123 // expensive operation. To prevent performance problems
124 // on account of its inadvertent use in product jvm's,
125 // we restrict its use to assertion checks only.
126 bool is_in(const void* p) const {
127 return used_region().contains(p);
128 }
129 bool is_in(oop obj) const {
130 return is_in((void*)obj);
131 }
132
133 // Returns true iff the given reserved memory of the space contains the
134 // given address.
135 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
136
137 // Returns true iff the given block is not allocated.
138 virtual bool is_free_block(const HeapWord* p) const = 0;
139
140 // Test whether p is double-aligned
141 static bool is_aligned(void* p) {
142 return ::is_aligned(p, sizeof(double));
143 }
144
145 // Size computations. Sizes are in bytes.
146 size_t capacity() const { return byte_size(bottom(), end()); }
147 virtual size_t used() const = 0;
148 virtual size_t free() const = 0;
149
150 // Iterate over all objects in the space, calling "cl.do_object" on
151 // each. Objects allocated by applications of the closure are not
152 // included in the iteration.
153 virtual void object_iterate(ObjectClosure* blk) = 0;
154
155 // If "p" is in the space, returns the address of the start of the
156 // "block" that contains "p". We say "block" instead of "object" since
157 // some heaps may not pack objects densely; a chunk may either be an
158 // object or a non-object. If "p" is not in the space, return null.
159 virtual HeapWord* block_start_const(const void* p) const = 0;
160
161 // The non-const version may have benevolent side effects on the data
162 // structure supporting these calls, possibly speeding up future calls.
163 // The default implementation, however, is simply to call the const
164 // version.
165 HeapWord* block_start(const void* p);
166
167 // Requires "addr" to be the start of a chunk, and returns its size.
168 // "addr + size" is required to be the start of a new chunk, or the end
169 // of the active area of the heap.
170 virtual size_t block_size(const HeapWord* addr) const = 0;
171
172 // Requires "addr" to be the start of a block, and returns "TRUE" iff
173 // the block is an object.
174 virtual bool block_is_obj(const HeapWord* addr) const = 0;
175
176 // Requires "addr" to be the start of a block, and returns "TRUE" iff
177 // the block is an object and the object is alive.
178 bool obj_is_alive(const HeapWord* addr) const;
179
180 // Allocation (return null if full). Assumes the caller has established
181 // mutually exclusive access to the space.
182 virtual HeapWord* allocate(size_t word_size) = 0;
183
184 // Allocation (return null if full). Enforces mutual exclusion internally.
185 virtual HeapWord* par_allocate(size_t word_size) = 0;
186
187 #if INCLUDE_SERIALGC
188 // Mark-sweep-compact support: all spaces can update pointers to objects
189 // moving as a part of compaction.
190 virtual void adjust_pointers() = 0;
191 #endif
192
193 void print() const;
194 virtual void print_on(outputStream* st) const;
195 void print_short() const;
196 void print_short_on(outputStream* st) const;
197 };
198
199 // A structure to represent a point at which objects are being copied
200 // during compaction.
201 class CompactPoint : public StackObj {
202 public:
203 Generation* gen;
204 ContiguousSpace* space;
205
206 CompactPoint(Generation* g = nullptr) :
207 gen(g), space(nullptr) {}
208 };
209
210 class GenSpaceMangler;
211
212 // A space in which the free area is contiguous. It therefore supports
213 // faster allocation, and compaction.
214 class ContiguousSpace: public Space {
215 friend class VMStructs;
216
217 private:
218 HeapWord* _compaction_top;
219 ContiguousSpace* _next_compaction_space;
220
221 static inline void verify_up_to_first_dead(ContiguousSpace* space) NOT_DEBUG_RETURN;
222
223 static inline void clear_empty_region(ContiguousSpace* space);
224
225 #if INCLUDE_SERIALGC
226 template <bool ALT_FWD>
227 void prepare_for_compaction_impl(CompactPoint* cp);
228
229 template <bool ALT_FWD>
230 void adjust_pointers_impl();
231
232 template <bool ALT_FWD>
233 void compact_impl();
234 #endif
235
236 protected:
237 HeapWord* _top;
238 // A helper for mangling the unused area of the space in debug builds.
239 GenSpaceMangler* _mangler;
240
241 // Used during compaction.
242 HeapWord* _first_dead;
243 HeapWord* _end_of_live;
244
245 // This the function to invoke when an allocation of an object covering
246 // "start" to "end" occurs to update other internal data structures.
247 virtual void update_for_block(HeapWord* start, HeapWord* the_end) { }
248
249 GenSpaceMangler* mangler() { return _mangler; }
250
251 // Allocation helpers (return null if full).
252 inline HeapWord* allocate_impl(size_t word_size);
253 inline HeapWord* par_allocate_impl(size_t word_size);
254
255 public:
256 ContiguousSpace();
257 ~ContiguousSpace();
258
259 // Initialization.
260 // "initialize" should be called once on a space, before it is used for
261 // any purpose. The "mr" arguments gives the bounds of the space, and
262 // the "clear_space" argument should be true unless the memory in "mr" is
263 // known to be zeroed.
264 void initialize(MemRegion mr, bool clear_space, bool mangle_space);
265
266 // The "clear" method must be called on a region that may have
267 // had allocation performed in it, but is now to be considered empty.
268 virtual void clear(bool mangle_space);
269
270 // Used temporarily during a compaction phase to hold the value
271 // top should have when compaction is complete.
272 HeapWord* compaction_top() const { return _compaction_top; }
273
274 void set_compaction_top(HeapWord* value) {
275 assert(value == nullptr || (value >= bottom() && value <= end()),
276 "should point inside space");
277 _compaction_top = value;
278 }
279
280 // Returns the next space (in the current generation) to be compacted in
281 // the global compaction order. Also is used to select the next
282 // space into which to compact.
283
284 virtual ContiguousSpace* next_compaction_space() const {
285 return _next_compaction_space;
286 }
287
288 void set_next_compaction_space(ContiguousSpace* csp) {
289 _next_compaction_space = csp;
290 }
291
292 #if INCLUDE_SERIALGC
293 // MarkSweep support phase2
294
295 // Start the process of compaction of the current space: compute
296 // post-compaction addresses, and insert forwarding pointers. The fields
297 // "cp->gen" and "cp->compaction_space" are the generation and space into
298 // which we are currently compacting. This call updates "cp" as necessary,
299 // and leaves the "compaction_top" of the final value of
300 // "cp->compaction_space" up-to-date. Offset tables may be updated in
301 // this phase as if the final copy had occurred; if so, "cp->threshold"
302 // indicates when the next such action should be taken.
303 void prepare_for_compaction(CompactPoint* cp);
304 // MarkSweep support phase3
305 void adjust_pointers() override;
306 // MarkSweep support phase4
307 virtual void compact();
308 #endif // INCLUDE_SERIALGC
309
310 // The maximum percentage of objects that can be dead in the compacted
311 // live part of a compacted space ("deadwood" support.)
312 virtual size_t allowed_dead_ratio() const { return 0; };
313
314 // "q" is an object of the given "size" that should be forwarded;
315 // "cp" names the generation ("gen") and containing "this" (which must
316 // also equal "cp->space"). "compact_top" is where in "this" the
317 // next object should be forwarded to. If there is room in "this" for
318 // the object, insert an appropriate forwarding pointer in "q".
319 // If not, go to the next compaction space (there must
320 // be one, since compaction must succeed -- we go to the first space of
321 // the previous generation if necessary, updating "cp"), reset compact_top
322 // and then forward. In either case, returns the new value of "compact_top".
323 // Invokes the "update_for_block" function of the then-current compaction
324 // space.
325 template <bool ALT_FWD>
326 HeapWord* forward(oop q, size_t size, CompactPoint* cp,
327 HeapWord* compact_top);
328
329 // Accessors
330 HeapWord* top() const { return _top; }
331 void set_top(HeapWord* value) { _top = value; }
332
333 void set_saved_mark() { _saved_mark_word = top(); }
334
335 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
336
337 // In debug mode mangle (write it with a particular bit
338 // pattern) the unused part of a space.
339
340 // Used to save the address in a space for later use during mangling.
341 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
342 // Used to save the space's current top for later use during mangling.
343 void set_top_for_allocations() PRODUCT_RETURN;
344
345 // Mangle regions in the space from the current top up to the
346 // previously mangled part of the space.
347 void mangle_unused_area() override PRODUCT_RETURN;
348 // Mangle [top, end)
349 void mangle_unused_area_complete() override PRODUCT_RETURN;
350
351 // Do some sparse checking on the area that should have been mangled.
352 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
353 // Check the complete area that should have been mangled.
354 // This code may be null depending on the macro DEBUG_MANGLING.
355 void check_mangled_unused_area_complete() PRODUCT_RETURN;
356
357 // Size computations: sizes in bytes.
358 size_t used() const override { return byte_size(bottom(), top()); }
359 size_t free() const override { return byte_size(top(), end()); }
360
361 bool is_free_block(const HeapWord* p) const override;
362
363 // In a contiguous space we have a more obvious bound on what parts
364 // contain objects.
365 MemRegion used_region() const override { return MemRegion(bottom(), top()); }
366
367 // Allocation (return null if full)
368 HeapWord* allocate(size_t word_size) override;
369 HeapWord* par_allocate(size_t word_size) override;
370
371 // Iteration
372 void object_iterate(ObjectClosure* blk) override;
373
374 // Compaction support
375 void reset_after_compaction() {
376 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
377 set_top(compaction_top());
378 }
379
380 // Apply "blk->do_oop" to the addresses of all reference fields in objects
381 // starting with the _saved_mark_word, which was noted during a generation's
382 // save_marks and is required to denote the head of an object.
383 // Fields in objects allocated by applications of the closure
384 // *are* included in the iteration.
385 // Updates _saved_mark_word to point to just after the last object
386 // iterated over.
387 template <typename OopClosureType>
388 void oop_since_save_marks_iterate(OopClosureType* blk);
389
390 // Same as object_iterate, but starting from "mark", which is required
391 // to denote the start of an object. Objects allocated by
392 // applications of the closure *are* included in the iteration.
393 virtual void object_iterate_from(HeapWord* mark, ObjectClosure* blk);
394
395 // Very inefficient implementation.
396 HeapWord* block_start_const(const void* p) const override;
397 size_t block_size(const HeapWord* p) const override;
398 // If a block is in the allocated area, it is an object.
399 bool block_is_obj(const HeapWord* p) const override { return p < top(); }
400
401 // Addresses for inlined allocation
402 HeapWord** top_addr() { return &_top; }
403 HeapWord** end_addr() { return &_end; }
404
405 void print_on(outputStream* st) const override;
406
407 // Debugging
408 void verify() const;
409 };
410
411 #if INCLUDE_SERIALGC
412
413 // Class TenuredSpace is used by TenuredGeneration; it supports an efficient
414 // "block_start" operation via a SerialBlockOffsetTable.
415
416 class TenuredSpace: public ContiguousSpace {
417 friend class VMStructs;
418 protected:
419 SerialBlockOffsetTable _offsets;
420
421 // Mark sweep support
422 size_t allowed_dead_ratio() const override;
423 public:
424 // Constructor
425 TenuredSpace(SerialBlockOffsetSharedArray* sharedOffsetArray,
426 MemRegion mr);
427
428 HeapWord* block_start_const(const void* addr) const override;
429
430 // Add offset table update.
431 inline HeapWord* allocate(size_t word_size) override;
432 inline HeapWord* par_allocate(size_t word_size) override;
433
434 // MarkSweep support phase3
435 void update_for_block(HeapWord* start, HeapWord* end) override;
436
437 void print_on(outputStream* st) const override;
438 };
439 #endif //INCLUDE_SERIALGC
440
441 #endif // SHARE_GC_SHARED_SPACE_HPP