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 protected:
226 HeapWord* _top;
227 // A helper for mangling the unused area of the space in debug builds.
228 GenSpaceMangler* _mangler;
229
230 // Used during compaction.
231 HeapWord* _first_dead;
232 HeapWord* _end_of_live;
233
234 // This the function to invoke when an allocation of an object covering
235 // "start" to "end" occurs to update other internal data structures.
236 virtual void update_for_block(HeapWord* start, HeapWord* the_end) { }
237
238 GenSpaceMangler* mangler() { return _mangler; }
239
240 // Allocation helpers (return null if full).
241 inline HeapWord* allocate_impl(size_t word_size);
242 inline HeapWord* par_allocate_impl(size_t word_size);
243
244 public:
245 ContiguousSpace();
246 ~ContiguousSpace();
247
248 // Initialization.
249 // "initialize" should be called once on a space, before it is used for
250 // any purpose. The "mr" arguments gives the bounds of the space, and
251 // the "clear_space" argument should be true unless the memory in "mr" is
252 // known to be zeroed.
253 void initialize(MemRegion mr, bool clear_space, bool mangle_space);
254
255 // The "clear" method must be called on a region that may have
256 // had allocation performed in it, but is now to be considered empty.
257 virtual void clear(bool mangle_space);
258
259 // Used temporarily during a compaction phase to hold the value
260 // top should have when compaction is complete.
261 HeapWord* compaction_top() const { return _compaction_top; }
262
263 void set_compaction_top(HeapWord* value) {
264 assert(value == nullptr || (value >= bottom() && value <= end()),
265 "should point inside space");
266 _compaction_top = value;
267 }
268
269 // Returns the next space (in the current generation) to be compacted in
270 // the global compaction order. Also is used to select the next
271 // space into which to compact.
272
273 virtual ContiguousSpace* next_compaction_space() const {
274 return _next_compaction_space;
275 }
276
277 void set_next_compaction_space(ContiguousSpace* csp) {
278 _next_compaction_space = csp;
279 }
280
281 #if INCLUDE_SERIALGC
282 // MarkSweep support phase2
283
284 // Start the process of compaction of the current space: compute
285 // post-compaction addresses, and insert forwarding pointers. The fields
286 // "cp->gen" and "cp->compaction_space" are the generation and space into
287 // which we are currently compacting. This call updates "cp" as necessary,
288 // and leaves the "compaction_top" of the final value of
289 // "cp->compaction_space" up-to-date. Offset tables may be updated in
290 // this phase as if the final copy had occurred; if so, "cp->threshold"
291 // indicates when the next such action should be taken.
292 void prepare_for_compaction(CompactPoint* cp);
293 // MarkSweep support phase3
294 void adjust_pointers() override;
295 // MarkSweep support phase4
296 virtual void compact();
297 #endif // INCLUDE_SERIALGC
298
299 // The maximum percentage of objects that can be dead in the compacted
300 // live part of a compacted space ("deadwood" support.)
301 virtual size_t allowed_dead_ratio() const { return 0; };
302
303 // "q" is an object of the given "size" that should be forwarded;
304 // "cp" names the generation ("gen") and containing "this" (which must
305 // also equal "cp->space"). "compact_top" is where in "this" the
306 // next object should be forwarded to. If there is room in "this" for
307 // the object, insert an appropriate forwarding pointer in "q".
308 // If not, go to the next compaction space (there must
309 // be one, since compaction must succeed -- we go to the first space of
310 // the previous generation if necessary, updating "cp"), reset compact_top
311 // and then forward. In either case, returns the new value of "compact_top".
312 // Invokes the "update_for_block" function of the then-current compaction
313 // space.
314 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
315 HeapWord* compact_top);
316
317 // Accessors
318 HeapWord* top() const { return _top; }
319 void set_top(HeapWord* value) { _top = value; }
320
321 void set_saved_mark() { _saved_mark_word = top(); }
322
323 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
324
325 // In debug mode mangle (write it with a particular bit
326 // pattern) the unused part of a space.
327
328 // Used to save the address in a space for later use during mangling.
329 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
330 // Used to save the space's current top for later use during mangling.
331 void set_top_for_allocations() PRODUCT_RETURN;
332
333 // Mangle regions in the space from the current top up to the
334 // previously mangled part of the space.
335 void mangle_unused_area() override PRODUCT_RETURN;
336 // Mangle [top, end)
337 void mangle_unused_area_complete() override PRODUCT_RETURN;
338
339 // Do some sparse checking on the area that should have been mangled.
340 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
341 // Check the complete area that should have been mangled.
342 // This code may be null depending on the macro DEBUG_MANGLING.
343 void check_mangled_unused_area_complete() PRODUCT_RETURN;
344
345 // Size computations: sizes in bytes.
346 size_t used() const override { return byte_size(bottom(), top()); }
347 size_t free() const override { return byte_size(top(), end()); }
348
349 bool is_free_block(const HeapWord* p) const override;
350
351 // In a contiguous space we have a more obvious bound on what parts
352 // contain objects.
353 MemRegion used_region() const override { return MemRegion(bottom(), top()); }
354
355 // Allocation (return null if full)
356 HeapWord* allocate(size_t word_size) override;
357 HeapWord* par_allocate(size_t word_size) override;
358
359 // Iteration
360 void object_iterate(ObjectClosure* blk) override;
361
362 // Compaction support
363 void reset_after_compaction() {
364 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
365 set_top(compaction_top());
366 }
367
368 // Apply "blk->do_oop" to the addresses of all reference fields in objects
369 // starting with the _saved_mark_word, which was noted during a generation's
370 // save_marks and is required to denote the head of an object.
371 // Fields in objects allocated by applications of the closure
372 // *are* included in the iteration.
373 // Updates _saved_mark_word to point to just after the last object
374 // iterated over.
375 template <typename OopClosureType>
376 void oop_since_save_marks_iterate(OopClosureType* blk);
377
378 // Same as object_iterate, but starting from "mark", which is required
379 // to denote the start of an object. Objects allocated by
380 // applications of the closure *are* included in the iteration.
381 virtual void object_iterate_from(HeapWord* mark, ObjectClosure* blk);
382
383 // Very inefficient implementation.
384 HeapWord* block_start_const(const void* p) const override;
385 size_t block_size(const HeapWord* p) const override;
386 // If a block is in the allocated area, it is an object.
387 bool block_is_obj(const HeapWord* p) const override { return p < top(); }
388
389 // Addresses for inlined allocation
390 HeapWord** top_addr() { return &_top; }
391 HeapWord** end_addr() { return &_end; }
392
393 void print_on(outputStream* st) const override;
394
395 // Debugging
396 void verify() const;
397 };
398
399 #if INCLUDE_SERIALGC
400
401 // Class TenuredSpace is used by TenuredGeneration; it supports an efficient
402 // "block_start" operation via a SerialBlockOffsetTable.
403
404 class TenuredSpace: public ContiguousSpace {
405 friend class VMStructs;
406 protected:
407 SerialBlockOffsetTable _offsets;
408
409 // Mark sweep support
410 size_t allowed_dead_ratio() const override;
411 public:
412 // Constructor
413 TenuredSpace(SerialBlockOffsetSharedArray* sharedOffsetArray,
414 MemRegion mr);
415
416 HeapWord* block_start_const(const void* addr) const override;
417
418 // Add offset table update.
419 inline HeapWord* allocate(size_t word_size) override;
420 inline HeapWord* par_allocate(size_t word_size) override;
421
422 // MarkSweep support phase3
423 void update_for_block(HeapWord* start, HeapWord* end) override;
424
425 void print_on(outputStream* st) const override;
426 };
427 #endif //INCLUDE_SERIALGC
428
429 #endif // SHARE_GC_SHARED_SPACE_HPP