Thu, 24 Mar 2011 15:47:01 -0700
7029036: Card-table verification hangs with all framework collectors, except G1, even before the first GC
Summary: When verifying clean card ranges, use memory-range-bounded iteration over oops of objects overlapping that range, thus avoiding the otherwise quadratic worst-case cost of scanning large object arrays.
Reviewed-by: jmasa, jwilhelm, tonyp
1 /*
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25 #ifndef SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP
26 #define SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP
28 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"
29 #include "memory/collectorPolicy.hpp"
30 #include "memory/generation.hpp"
31 #include "memory/sharedHeap.hpp"
33 class SubTasksDone;
35 // A "GenCollectedHeap" is a SharedHeap that uses generational
36 // collection. It is represented with a sequence of Generation's.
37 class GenCollectedHeap : public SharedHeap {
38 friend class GenCollectorPolicy;
39 friend class Generation;
40 friend class DefNewGeneration;
41 friend class TenuredGeneration;
42 friend class ConcurrentMarkSweepGeneration;
43 friend class CMSCollector;
44 friend class GenMarkSweep;
45 friend class VM_GenCollectForAllocation;
46 friend class VM_GenCollectForPermanentAllocation;
47 friend class VM_GenCollectFull;
48 friend class VM_GenCollectFullConcurrent;
49 friend class VM_GC_HeapInspection;
50 friend class VM_HeapDumper;
51 friend class HeapInspection;
52 friend class GCCauseSetter;
53 friend class VMStructs;
54 public:
55 enum SomeConstants {
56 max_gens = 10
57 };
59 friend class VM_PopulateDumpSharedSpace;
61 protected:
62 // Fields:
63 static GenCollectedHeap* _gch;
65 private:
66 int _n_gens;
67 Generation* _gens[max_gens];
68 GenerationSpec** _gen_specs;
70 // The generational collector policy.
71 GenCollectorPolicy* _gen_policy;
73 // Indicates that the most recent previous incremental collection failed.
74 // The flag is cleared when an action is taken that might clear the
75 // condition that caused that incremental collection to fail.
76 bool _incremental_collection_failed;
78 // In support of ExplicitGCInvokesConcurrent functionality
79 unsigned int _full_collections_completed;
81 // Data structure for claiming the (potentially) parallel tasks in
82 // (gen-specific) strong roots processing.
83 SubTasksDone* _gen_process_strong_tasks;
84 SubTasksDone* gen_process_strong_tasks() { return _gen_process_strong_tasks; }
86 // In block contents verification, the number of header words to skip
87 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
89 // GC is not allowed during the dump of the shared classes. Keep track
90 // of this in order to provide an reasonable error message when terminating.
91 bool _preloading_shared_classes;
93 protected:
94 // Directs each generation up to and including "collectedGen" to recompute
95 // its desired size.
96 void compute_new_generation_sizes(int collectedGen);
98 // Helper functions for allocation
99 HeapWord* attempt_allocation(size_t size,
100 bool is_tlab,
101 bool first_only);
103 // Helper function for two callbacks below.
104 // Considers collection of the first max_level+1 generations.
105 void do_collection(bool full,
106 bool clear_all_soft_refs,
107 size_t size,
108 bool is_tlab,
109 int max_level);
111 // Callback from VM_GenCollectForAllocation operation.
112 // This function does everything necessary/possible to satisfy an
113 // allocation request that failed in the youngest generation that should
114 // have handled it (including collection, expansion, etc.)
115 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
117 // Callback from VM_GenCollectFull operation.
118 // Perform a full collection of the first max_level+1 generations.
119 void do_full_collection(bool clear_all_soft_refs, int max_level);
121 // Does the "cause" of GC indicate that
122 // we absolutely __must__ clear soft refs?
123 bool must_clear_all_soft_refs();
125 public:
126 GenCollectedHeap(GenCollectorPolicy *policy);
128 GCStats* gc_stats(int level) const;
130 // Returns JNI_OK on success
131 virtual jint initialize();
132 char* allocate(size_t alignment, PermanentGenerationSpec* perm_gen_spec,
133 size_t* _total_reserved, int* _n_covered_regions,
134 ReservedSpace* heap_rs);
136 // Does operations required after initialization has been done.
137 void post_initialize();
139 // Initialize ("weak") refs processing support
140 virtual void ref_processing_init();
142 virtual CollectedHeap::Name kind() const {
143 return CollectedHeap::GenCollectedHeap;
144 }
146 // The generational collector policy.
147 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
149 // Adaptive size policy
150 virtual AdaptiveSizePolicy* size_policy() {
151 return gen_policy()->size_policy();
152 }
154 size_t capacity() const;
155 size_t used() const;
157 // Save the "used_region" for generations level and lower,
158 // and, if perm is true, for perm gen.
159 void save_used_regions(int level, bool perm);
161 size_t max_capacity() const;
163 HeapWord* mem_allocate(size_t size,
164 bool is_large_noref,
165 bool is_tlab,
166 bool* gc_overhead_limit_was_exceeded);
168 // We may support a shared contiguous allocation area, if the youngest
169 // generation does.
170 bool supports_inline_contig_alloc() const;
171 HeapWord** top_addr() const;
172 HeapWord** end_addr() const;
174 // Return an estimate of the maximum allocation that could be performed
175 // without triggering any collection activity. In a generational
176 // collector, for example, this is probably the largest allocation that
177 // could be supported in the youngest generation. It is "unsafe" because
178 // no locks are taken; the result should be treated as an approximation,
179 // not a guarantee.
180 size_t unsafe_max_alloc();
182 // Does this heap support heap inspection? (+PrintClassHistogram)
183 virtual bool supports_heap_inspection() const { return true; }
185 // Perform a full collection of the heap; intended for use in implementing
186 // "System.gc". This implies as full a collection as the CollectedHeap
187 // supports. Caller does not hold the Heap_lock on entry.
188 void collect(GCCause::Cause cause);
190 // This interface assumes that it's being called by the
191 // vm thread. It collects the heap assuming that the
192 // heap lock is already held and that we are executing in
193 // the context of the vm thread.
194 void collect_as_vm_thread(GCCause::Cause cause);
196 // The same as above but assume that the caller holds the Heap_lock.
197 void collect_locked(GCCause::Cause cause);
199 // Perform a full collection of the first max_level+1 generations.
200 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
201 void collect(GCCause::Cause cause, int max_level);
203 // Returns "TRUE" iff "p" points into the allocated area of the heap.
204 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
205 // be expensive to compute in general, so, to prevent
206 // their inadvertent use in product jvm's, we restrict their use to
207 // assertion checking or verification only.
208 bool is_in(const void* p) const;
210 // override
211 bool is_in_closed_subset(const void* p) const {
212 if (UseConcMarkSweepGC) {
213 return is_in_reserved(p);
214 } else {
215 return is_in(p);
216 }
217 }
219 // Returns "TRUE" iff "p" points into the youngest generation.
220 bool is_in_youngest(void* p);
222 // Iteration functions.
223 void oop_iterate(OopClosure* cl);
224 void oop_iterate(MemRegion mr, OopClosure* cl);
225 void object_iterate(ObjectClosure* cl);
226 void safe_object_iterate(ObjectClosure* cl);
227 void object_iterate_since_last_GC(ObjectClosure* cl);
228 Space* space_containing(const void* addr) const;
230 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
231 // each address in the (reserved) heap is a member of exactly
232 // one block. The defining characteristic of a block is that it is
233 // possible to find its size, and thus to progress forward to the next
234 // block. (Blocks may be of different sizes.) Thus, blocks may
235 // represent Java objects, or they might be free blocks in a
236 // free-list-based heap (or subheap), as long as the two kinds are
237 // distinguishable and the size of each is determinable.
239 // Returns the address of the start of the "block" that contains the
240 // address "addr". We say "blocks" instead of "object" since some heaps
241 // may not pack objects densely; a chunk may either be an object or a
242 // non-object.
243 virtual HeapWord* block_start(const void* addr) const;
245 // Requires "addr" to be the start of a chunk, and returns its size.
246 // "addr + size" is required to be the start of a new chunk, or the end
247 // of the active area of the heap. Assumes (and verifies in non-product
248 // builds) that addr is in the allocated part of the heap and is
249 // the start of a chunk.
250 virtual size_t block_size(const HeapWord* addr) const;
252 // Requires "addr" to be the start of a block, and returns "TRUE" iff
253 // the block is an object. Assumes (and verifies in non-product
254 // builds) that addr is in the allocated part of the heap and is
255 // the start of a chunk.
256 virtual bool block_is_obj(const HeapWord* addr) const;
258 // Section on TLAB's.
259 virtual bool supports_tlab_allocation() const;
260 virtual size_t tlab_capacity(Thread* thr) const;
261 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
262 virtual HeapWord* allocate_new_tlab(size_t size);
264 // Can a compiler initialize a new object without store barriers?
265 // This permission only extends from the creation of a new object
266 // via a TLAB up to the first subsequent safepoint.
267 virtual bool can_elide_tlab_store_barriers() const {
268 return true;
269 }
271 virtual bool card_mark_must_follow_store() const {
272 return UseConcMarkSweepGC;
273 }
275 // We don't need barriers for stores to objects in the
276 // young gen and, a fortiori, for initializing stores to
277 // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS}
278 // only and may need to be re-examined in case other
279 // kinds of collectors are implemented in the future.
280 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
281 // We wanted to assert that:-
282 // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC,
283 // "Check can_elide_initializing_store_barrier() for this collector");
284 // but unfortunately the flag UseSerialGC need not necessarily always
285 // be set when DefNew+Tenured are being used.
286 return is_in_youngest((void*)new_obj);
287 }
289 // Can a compiler elide a store barrier when it writes
290 // a permanent oop into the heap? Applies when the compiler
291 // is storing x to the heap, where x->is_perm() is true.
292 virtual bool can_elide_permanent_oop_store_barriers() const {
293 // CMS needs to see all, even intra-generational, ref updates.
294 return !UseConcMarkSweepGC;
295 }
297 // The "requestor" generation is performing some garbage collection
298 // action for which it would be useful to have scratch space. The
299 // requestor promises to allocate no more than "max_alloc_words" in any
300 // older generation (via promotion say.) Any blocks of space that can
301 // be provided are returned as a list of ScratchBlocks, sorted by
302 // decreasing size.
303 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
304 // Allow each generation to reset any scratch space that it has
305 // contributed as it needs.
306 void release_scratch();
308 size_t large_typearray_limit();
310 // Ensure parsability: override
311 virtual void ensure_parsability(bool retire_tlabs);
313 // Time in ms since the longest time a collector ran in
314 // in any generation.
315 virtual jlong millis_since_last_gc();
317 // Total number of full collections completed.
318 unsigned int total_full_collections_completed() {
319 assert(_full_collections_completed <= _total_full_collections,
320 "Can't complete more collections than were started");
321 return _full_collections_completed;
322 }
324 // Update above counter, as appropriate, at the end of a stop-world GC cycle
325 unsigned int update_full_collections_completed();
326 // Update above counter, as appropriate, at the end of a concurrent GC cycle
327 unsigned int update_full_collections_completed(unsigned int count);
329 // Update "time of last gc" for all constituent generations
330 // to "now".
331 void update_time_of_last_gc(jlong now) {
332 for (int i = 0; i < _n_gens; i++) {
333 _gens[i]->update_time_of_last_gc(now);
334 }
335 perm_gen()->update_time_of_last_gc(now);
336 }
338 // Update the gc statistics for each generation.
339 // "level" is the level of the lastest collection
340 void update_gc_stats(int current_level, bool full) {
341 for (int i = 0; i < _n_gens; i++) {
342 _gens[i]->update_gc_stats(current_level, full);
343 }
344 perm_gen()->update_gc_stats(current_level, full);
345 }
347 // Override.
348 bool no_gc_in_progress() { return !is_gc_active(); }
350 // Override.
351 void prepare_for_verify();
353 // Override.
354 void verify(bool allow_dirty, bool silent, bool /* option */);
356 // Override.
357 void print() const;
358 void print_on(outputStream* st) const;
359 virtual void print_gc_threads_on(outputStream* st) const;
360 virtual void gc_threads_do(ThreadClosure* tc) const;
361 virtual void print_tracing_info() const;
363 // PrintGC, PrintGCDetails support
364 void print_heap_change(size_t prev_used) const;
365 void print_perm_heap_change(size_t perm_prev_used) const;
367 // The functions below are helper functions that a subclass of
368 // "CollectedHeap" can use in the implementation of its virtual
369 // functions.
371 class GenClosure : public StackObj {
372 public:
373 virtual void do_generation(Generation* gen) = 0;
374 };
376 // Apply "cl.do_generation" to all generations in the heap (not including
377 // the permanent generation). If "old_to_young" determines the order.
378 void generation_iterate(GenClosure* cl, bool old_to_young);
380 void space_iterate(SpaceClosure* cl);
382 // Return "true" if all generations (but perm) have reached the
383 // maximal committed limit that they can reach, without a garbage
384 // collection.
385 virtual bool is_maximal_no_gc() const;
387 // Return the generation before "gen", or else NULL.
388 Generation* prev_gen(Generation* gen) const {
389 int l = gen->level();
390 if (l == 0) return NULL;
391 else return _gens[l-1];
392 }
394 // Return the generation after "gen", or else NULL.
395 Generation* next_gen(Generation* gen) const {
396 int l = gen->level() + 1;
397 if (l == _n_gens) return NULL;
398 else return _gens[l];
399 }
401 Generation* get_gen(int i) const {
402 if (i >= 0 && i < _n_gens)
403 return _gens[i];
404 else
405 return NULL;
406 }
408 int n_gens() const {
409 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
410 return _n_gens;
411 }
413 // Convenience function to be used in situations where the heap type can be
414 // asserted to be this type.
415 static GenCollectedHeap* heap();
417 void set_par_threads(int t);
420 // Invoke the "do_oop" method of one of the closures "not_older_gens"
421 // or "older_gens" on root locations for the generation at
422 // "level". (The "older_gens" closure is used for scanning references
423 // from older generations; "not_older_gens" is used everywhere else.)
424 // If "younger_gens_as_roots" is false, younger generations are
425 // not scanned as roots; in this case, the caller must be arranging to
426 // scan the younger generations itself. (For example, a generation might
427 // explicitly mark reachable objects in younger generations, to avoid
428 // excess storage retention.) If "collecting_perm_gen" is false, then
429 // roots that may only contain references to permGen objects are not
430 // scanned. The "so" argument determines which of the roots
431 // the closure is applied to:
432 // "SO_None" does none;
433 // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
434 // "SO_SystemClasses" to all the "system" classes and loaders;
435 // "SO_Symbols_and_Strings" applies the closure to all entries in
436 // SymbolsTable and StringTable.
437 void gen_process_strong_roots(int level,
438 bool younger_gens_as_roots,
439 // The remaining arguments are in an order
440 // consistent with SharedHeap::process_strong_roots:
441 bool activate_scope,
442 bool collecting_perm_gen,
443 SharedHeap::ScanningOption so,
444 OopsInGenClosure* not_older_gens,
445 bool do_code_roots,
446 OopsInGenClosure* older_gens);
448 // Apply "blk" to all the weak roots of the system. These include
449 // JNI weak roots, the code cache, system dictionary, symbol table,
450 // string table, and referents of reachable weak refs.
451 void gen_process_weak_roots(OopClosure* root_closure,
452 CodeBlobClosure* code_roots,
453 OopClosure* non_root_closure);
455 // Set the saved marks of generations, if that makes sense.
456 // In particular, if any generation might iterate over the oops
457 // in other generations, it should call this method.
458 void save_marks();
460 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
461 // allocated since the last call to save_marks in generations at or above
462 // "level" (including the permanent generation.) The "cur" closure is
463 // applied to references in the generation at "level", and the "older"
464 // closure to older (and permanent) generations.
465 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
466 void oop_since_save_marks_iterate(int level, \
467 OopClosureType* cur, \
468 OopClosureType* older);
470 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
472 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
474 // Returns "true" iff no allocations have occurred in any generation at
475 // "level" or above (including the permanent generation) since the last
476 // call to "save_marks".
477 bool no_allocs_since_save_marks(int level);
479 // Returns true if an incremental collection is likely to fail.
480 // We optionally consult the young gen, if asked to do so;
481 // otherwise we base our answer on whether the previous incremental
482 // collection attempt failed with no corrective action as of yet.
483 bool incremental_collection_will_fail(bool consult_young) {
484 // Assumes a 2-generation system; the first disjunct remembers if an
485 // incremental collection failed, even when we thought (second disjunct)
486 // that it would not.
487 assert(heap()->collector_policy()->is_two_generation_policy(),
488 "the following definition may not be suitable for an n(>2)-generation system");
489 return incremental_collection_failed() ||
490 (consult_young && !get_gen(0)->collection_attempt_is_safe());
491 }
493 // If a generation bails out of an incremental collection,
494 // it sets this flag.
495 bool incremental_collection_failed() const {
496 return _incremental_collection_failed;
497 }
498 void set_incremental_collection_failed() {
499 _incremental_collection_failed = true;
500 }
501 void clear_incremental_collection_failed() {
502 _incremental_collection_failed = false;
503 }
505 // Promotion of obj into gen failed. Try to promote obj to higher non-perm
506 // gens in ascending order; return the new location of obj if successful.
507 // Otherwise, try expand-and-allocate for obj in each generation starting at
508 // gen; return the new location of obj if successful. Otherwise, return NULL.
509 oop handle_failed_promotion(Generation* gen,
510 oop obj,
511 size_t obj_size);
513 private:
514 // Accessor for memory state verification support
515 NOT_PRODUCT(
516 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
517 )
519 // Override
520 void check_for_non_bad_heap_word_value(HeapWord* addr,
521 size_t size) PRODUCT_RETURN;
523 // For use by mark-sweep. As implemented, mark-sweep-compact is global
524 // in an essential way: compaction is performed across generations, by
525 // iterating over spaces.
526 void prepare_for_compaction();
528 // Perform a full collection of the first max_level+1 generations.
529 // This is the low level interface used by the public versions of
530 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
531 void collect_locked(GCCause::Cause cause, int max_level);
533 // Returns success or failure.
534 bool create_cms_collector();
536 // In support of ExplicitGCInvokesConcurrent functionality
537 bool should_do_concurrent_full_gc(GCCause::Cause cause);
538 void collect_mostly_concurrent(GCCause::Cause cause);
540 // Save the tops of the spaces in all generations
541 void record_gen_tops_before_GC() PRODUCT_RETURN;
543 protected:
544 virtual void gc_prologue(bool full);
545 virtual void gc_epilogue(bool full);
547 public:
548 virtual void preload_and_dump(TRAPS) KERNEL_RETURN;
549 };
551 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP