| /* |
| * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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| */ |
| |
| #ifndef SHARE_VM_GC_SHARED_GENERATION_HPP |
| #define SHARE_VM_GC_SHARED_GENERATION_HPP |
| |
| #include "gc/shared/collectorCounters.hpp" |
| #include "gc/shared/referenceProcessor.hpp" |
| #include "logging/log.hpp" |
| #include "memory/allocation.hpp" |
| #include "memory/memRegion.hpp" |
| #include "memory/universe.hpp" |
| #include "memory/virtualspace.hpp" |
| #include "runtime/mutex.hpp" |
| #include "runtime/perfData.hpp" |
| |
| // A Generation models a heap area for similarly-aged objects. |
| // It will contain one ore more spaces holding the actual objects. |
| // |
| // The Generation class hierarchy: |
| // |
| // Generation - abstract base class |
| // - DefNewGeneration - allocation area (copy collected) |
| // - ParNewGeneration - a DefNewGeneration that is collected by |
| // several threads |
| // - CardGeneration - abstract class adding offset array behavior |
| // - TenuredGeneration - tenured (old object) space (markSweepCompact) |
| // - ConcurrentMarkSweepGeneration - Mostly Concurrent Mark Sweep Generation |
| // (Detlefs-Printezis refinement of |
| // Boehm-Demers-Schenker) |
| // |
| // The system configurations currently allowed are: |
| // |
| // DefNewGeneration + TenuredGeneration |
| // |
| // ParNewGeneration + ConcurrentMarkSweepGeneration |
| // |
| |
| class DefNewGeneration; |
| class GenerationSpec; |
| class CompactibleSpace; |
| class ContiguousSpace; |
| class CompactPoint; |
| class OopsInGenClosure; |
| class OopClosure; |
| class ScanClosure; |
| class FastScanClosure; |
| class GenCollectedHeap; |
| class GCStats; |
| |
| // A "ScratchBlock" represents a block of memory in one generation usable by |
| // another. It represents "num_words" free words, starting at and including |
| // the address of "this". |
| struct ScratchBlock { |
| ScratchBlock* next; |
| size_t num_words; |
| HeapWord scratch_space[1]; // Actually, of size "num_words-2" (assuming |
| // first two fields are word-sized.) |
| }; |
| |
| class Generation: public CHeapObj<mtGC> { |
| friend class VMStructs; |
| private: |
| jlong _time_of_last_gc; // time when last gc on this generation happened (ms) |
| MemRegion _prev_used_region; // for collectors that want to "remember" a value for |
| // used region at some specific point during collection. |
| |
| protected: |
| // Minimum and maximum addresses for memory reserved (not necessarily |
| // committed) for generation. |
| // Used by card marking code. Must not overlap with address ranges of |
| // other generations. |
| MemRegion _reserved; |
| |
| // Memory area reserved for generation |
| VirtualSpace _virtual_space; |
| |
| // ("Weak") Reference processing support |
| ReferenceProcessor* _ref_processor; |
| |
| // Performance Counters |
| CollectorCounters* _gc_counters; |
| |
| // Statistics for garbage collection |
| GCStats* _gc_stats; |
| |
| // Initialize the generation. |
| Generation(ReservedSpace rs, size_t initial_byte_size); |
| |
| // Apply "cl->do_oop" to (the address of) (exactly) all the ref fields in |
| // "sp" that point into younger generations. |
| // The iteration is only over objects allocated at the start of the |
| // iterations; objects allocated as a result of applying the closure are |
| // not included. |
| void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl, uint n_threads); |
| |
| public: |
| // The set of possible generation kinds. |
| enum Name { |
| DefNew, |
| ParNew, |
| MarkSweepCompact, |
| ConcurrentMarkSweep, |
| Other |
| }; |
| |
| enum SomePublicConstants { |
| // Generations are GenGrain-aligned and have size that are multiples of |
| // GenGrain. |
| // Note: on ARM we add 1 bit for card_table_base to be properly aligned |
| // (we expect its low byte to be zero - see implementation of post_barrier) |
| LogOfGenGrain = 16 ARM32_ONLY(+1), |
| GenGrain = 1 << LogOfGenGrain |
| }; |
| |
| // allocate and initialize ("weak") refs processing support |
| virtual void ref_processor_init(); |
| void set_ref_processor(ReferenceProcessor* rp) { |
| assert(_ref_processor == NULL, "clobbering existing _ref_processor"); |
| _ref_processor = rp; |
| } |
| |
| virtual Generation::Name kind() { return Generation::Other; } |
| |
| // This properly belongs in the collector, but for now this |
| // will do. |
| virtual bool refs_discovery_is_atomic() const { return true; } |
| virtual bool refs_discovery_is_mt() const { return false; } |
| |
| // Space inquiries (results in bytes) |
| size_t initial_size(); |
| virtual size_t capacity() const = 0; // The maximum number of object bytes the |
| // generation can currently hold. |
| virtual size_t used() const = 0; // The number of used bytes in the gen. |
| virtual size_t free() const = 0; // The number of free bytes in the gen. |
| |
| // Support for java.lang.Runtime.maxMemory(); see CollectedHeap. |
| // Returns the total number of bytes available in a generation |
| // for the allocation of objects. |
| virtual size_t max_capacity() const; |
| |
| // If this is a young generation, the maximum number of bytes that can be |
| // allocated in this generation before a GC is triggered. |
| virtual size_t capacity_before_gc() const { return 0; } |
| |
| // The largest number of contiguous free bytes in the generation, |
| // including expansion (Assumes called at a safepoint.) |
| virtual size_t contiguous_available() const = 0; |
| // The largest number of contiguous free bytes in this or any higher generation. |
| virtual size_t max_contiguous_available() const; |
| |
| // Returns true if promotions of the specified amount are |
| // likely to succeed without a promotion failure. |
| // Promotion of the full amount is not guaranteed but |
| // might be attempted in the worst case. |
| virtual bool promotion_attempt_is_safe(size_t max_promotion_in_bytes) const; |
| |
| // For a non-young generation, this interface can be used to inform a |
| // generation that a promotion attempt into that generation failed. |
| // Typically used to enable diagnostic output for post-mortem analysis, |
| // but other uses of the interface are not ruled out. |
| virtual void promotion_failure_occurred() { /* does nothing */ } |
| |
| // Return an estimate of the maximum allocation that could be performed |
| // in the generation without triggering any collection or expansion |
| // activity. It is "unsafe" because no locks are taken; the result |
| // should be treated as an approximation, not a guarantee, for use in |
| // heuristic resizing decisions. |
| virtual size_t unsafe_max_alloc_nogc() const = 0; |
| |
| // Returns true if this generation cannot be expanded further |
| // without a GC. Override as appropriate. |
| virtual bool is_maximal_no_gc() const { |
| return _virtual_space.uncommitted_size() == 0; |
| } |
| |
| MemRegion reserved() const { return _reserved; } |
| |
| // Returns a region guaranteed to contain all the objects in the |
| // generation. |
| virtual MemRegion used_region() const { return _reserved; } |
| |
| MemRegion prev_used_region() const { return _prev_used_region; } |
| virtual void save_used_region() { _prev_used_region = used_region(); } |
| |
| // Returns "TRUE" iff "p" points into the committed areas in the generation. |
| // For some kinds of generations, this may be an expensive operation. |
| // To avoid performance problems stemming from its inadvertent use in |
| // product jvm's, we restrict its use to assertion checking or |
| // verification only. |
| virtual bool is_in(const void* p) const; |
| |
| /* Returns "TRUE" iff "p" points into the reserved area of the generation. */ |
| bool is_in_reserved(const void* p) const { |
| return _reserved.contains(p); |
| } |
| |
| // If some space in the generation contains the given "addr", return a |
| // pointer to that space, else return "NULL". |
| virtual Space* space_containing(const void* addr) const; |
| |
| // Iteration - do not use for time critical operations |
| virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0; |
| |
| // Returns the first space, if any, in the generation that can participate |
| // in compaction, or else "NULL". |
| virtual CompactibleSpace* first_compaction_space() const = 0; |
| |
| // Returns "true" iff this generation should be used to allocate an |
| // object of the given size. Young generations might |
| // wish to exclude very large objects, for example, since, if allocated |
| // often, they would greatly increase the frequency of young-gen |
| // collection. |
| virtual bool should_allocate(size_t word_size, bool is_tlab) { |
| bool result = false; |
| size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize); |
| if (!is_tlab || supports_tlab_allocation()) { |
| result = (word_size > 0) && (word_size < overflow_limit); |
| } |
| return result; |
| } |
| |
| // Allocate and returns a block of the requested size, or returns "NULL". |
| // Assumes the caller has done any necessary locking. |
| virtual HeapWord* allocate(size_t word_size, bool is_tlab) = 0; |
| |
| // Like "allocate", but performs any necessary locking internally. |
| virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0; |
| |
| // Some generation may offer a region for shared, contiguous allocation, |
| // via inlined code (by exporting the address of the top and end fields |
| // defining the extent of the contiguous allocation region.) |
| |
| // This function returns "true" iff the heap supports this kind of |
| // allocation. (More precisely, this means the style of allocation that |
| // increments *top_addr()" with a CAS.) (Default is "no".) |
| // A generation that supports this allocation style must use lock-free |
| // allocation for *all* allocation, since there are times when lock free |
| // allocation will be concurrent with plain "allocate" calls. |
| virtual bool supports_inline_contig_alloc() const { return false; } |
| |
| // These functions return the addresses of the fields that define the |
| // boundaries of the contiguous allocation area. (These fields should be |
| // physically near to one another.) |
| virtual HeapWord* volatile* top_addr() const { return NULL; } |
| virtual HeapWord** end_addr() const { return NULL; } |
| |
| // Thread-local allocation buffers |
| virtual bool supports_tlab_allocation() const { return false; } |
| virtual size_t tlab_capacity() const { |
| guarantee(false, "Generation doesn't support thread local allocation buffers"); |
| return 0; |
| } |
| virtual size_t tlab_used() const { |
| guarantee(false, "Generation doesn't support thread local allocation buffers"); |
| return 0; |
| } |
| virtual size_t unsafe_max_tlab_alloc() const { |
| guarantee(false, "Generation doesn't support thread local allocation buffers"); |
| return 0; |
| } |
| |
| // "obj" is the address of an object in a younger generation. Allocate space |
| // for "obj" in the current (or some higher) generation, and copy "obj" into |
| // the newly allocated space, if possible, returning the result (or NULL if |
| // the allocation failed). |
| // |
| // The "obj_size" argument is just obj->size(), passed along so the caller can |
| // avoid repeating the virtual call to retrieve it. |
| virtual oop promote(oop obj, size_t obj_size); |
| |
| // Thread "thread_num" (0 <= i < ParalleGCThreads) wants to promote |
| // object "obj", whose original mark word was "m", and whose size is |
| // "word_sz". If possible, allocate space for "obj", copy obj into it |
| // (taking care to copy "m" into the mark word when done, since the mark |
| // word of "obj" may have been overwritten with a forwarding pointer, and |
| // also taking care to copy the klass pointer *last*. Returns the new |
| // object if successful, or else NULL. |
| virtual oop par_promote(int thread_num, oop obj, markOop m, size_t word_sz); |
| |
| // Informs the current generation that all par_promote_alloc's in the |
| // collection have been completed; any supporting data structures can be |
| // reset. Default is to do nothing. |
| virtual void par_promote_alloc_done(int thread_num) {} |
| |
| // Informs the current generation that all oop_since_save_marks_iterates |
| // performed by "thread_num" in the current collection, if any, have been |
| // completed; any supporting data structures can be reset. Default is to |
| // do nothing. |
| virtual void par_oop_since_save_marks_iterate_done(int thread_num) {} |
| |
| // Returns "true" iff collect() should subsequently be called on this |
| // this generation. See comment below. |
| // This is a generic implementation which can be overridden. |
| // |
| // Note: in the current (1.4) implementation, when genCollectedHeap's |
| // incremental_collection_will_fail flag is set, all allocations are |
| // slow path (the only fast-path place to allocate is DefNew, which |
| // will be full if the flag is set). |
| // Thus, older generations which collect younger generations should |
| // test this flag and collect if it is set. |
| virtual bool should_collect(bool full, |
| size_t word_size, |
| bool is_tlab) { |
| return (full || should_allocate(word_size, is_tlab)); |
| } |
| |
| // Returns true if the collection is likely to be safely |
| // completed. Even if this method returns true, a collection |
| // may not be guaranteed to succeed, and the system should be |
| // able to safely unwind and recover from that failure, albeit |
| // at some additional cost. |
| virtual bool collection_attempt_is_safe() { |
| guarantee(false, "Are you sure you want to call this method?"); |
| return true; |
| } |
| |
| // Perform a garbage collection. |
| // If full is true attempt a full garbage collection of this generation. |
| // Otherwise, attempting to (at least) free enough space to support an |
| // allocation of the given "word_size". |
| virtual void collect(bool full, |
| bool clear_all_soft_refs, |
| size_t word_size, |
| bool is_tlab) = 0; |
| |
| // Perform a heap collection, attempting to create (at least) enough |
| // space to support an allocation of the given "word_size". If |
| // successful, perform the allocation and return the resulting |
| // "oop" (initializing the allocated block). If the allocation is |
| // still unsuccessful, return "NULL". |
| virtual HeapWord* expand_and_allocate(size_t word_size, |
| bool is_tlab, |
| bool parallel = false) = 0; |
| |
| // Some generations may require some cleanup or preparation actions before |
| // allowing a collection. The default is to do nothing. |
| virtual void gc_prologue(bool full) {} |
| |
| // Some generations may require some cleanup actions after a collection. |
| // The default is to do nothing. |
| virtual void gc_epilogue(bool full) {} |
| |
| // Save the high water marks for the used space in a generation. |
| virtual void record_spaces_top() {} |
| |
| // Some generations may need to be "fixed-up" after some allocation |
| // activity to make them parsable again. The default is to do nothing. |
| virtual void ensure_parsability() {} |
| |
| // Time (in ms) when we were last collected or now if a collection is |
| // in progress. |
| virtual jlong time_of_last_gc(jlong now) { |
| // Both _time_of_last_gc and now are set using a time source |
| // that guarantees monotonically non-decreasing values provided |
| // the underlying platform provides such a source. So we still |
| // have to guard against non-monotonicity. |
| NOT_PRODUCT( |
| if (now < _time_of_last_gc) { |
| log_warning(gc)("time warp: " JLONG_FORMAT " to " JLONG_FORMAT, _time_of_last_gc, now); |
| } |
| ) |
| return _time_of_last_gc; |
| } |
| |
| virtual void update_time_of_last_gc(jlong now) { |
| _time_of_last_gc = now; |
| } |
| |
| // Generations may keep statistics about collection. This method |
| // updates those statistics. current_generation is the generation |
| // that was most recently collected. This allows the generation to |
| // decide what statistics are valid to collect. For example, the |
| // generation can decide to gather the amount of promoted data if |
| // the collection of the young generation has completed. |
| GCStats* gc_stats() const { return _gc_stats; } |
| virtual void update_gc_stats(Generation* current_generation, bool full) {} |
| |
| // Mark sweep support phase2 |
| virtual void prepare_for_compaction(CompactPoint* cp); |
| // Mark sweep support phase3 |
| virtual void adjust_pointers(); |
| // Mark sweep support phase4 |
| virtual void compact(); |
| virtual void post_compact() { ShouldNotReachHere(); } |
| |
| // Support for CMS's rescan. In this general form we return a pointer |
| // to an abstract object that can be used, based on specific previously |
| // decided protocols, to exchange information between generations, |
| // information that may be useful for speeding up certain types of |
| // garbage collectors. A NULL value indicates to the client that |
| // no data recording is expected by the provider. The data-recorder is |
| // expected to be GC worker thread-local, with the worker index |
| // indicated by "thr_num". |
| virtual void* get_data_recorder(int thr_num) { return NULL; } |
| virtual void sample_eden_chunk() {} |
| |
| // Some generations may require some cleanup actions before allowing |
| // a verification. |
| virtual void prepare_for_verify() {} |
| |
| // Accessing "marks". |
| |
| // This function gives a generation a chance to note a point between |
| // collections. For example, a contiguous generation might note the |
| // beginning allocation point post-collection, which might allow some later |
| // operations to be optimized. |
| virtual void save_marks() {} |
| |
| // This function allows generations to initialize any "saved marks". That |
| // is, should only be called when the generation is empty. |
| virtual void reset_saved_marks() {} |
| |
| // This function is "true" iff any no allocations have occurred in the |
| // generation since the last call to "save_marks". |
| virtual bool no_allocs_since_save_marks() = 0; |
| |
| // Apply "cl->apply" to (the addresses of) all reference fields in objects |
| // allocated in the current generation since the last call to "save_marks". |
| // If more objects are allocated in this generation as a result of applying |
| // the closure, iterates over reference fields in those objects as well. |
| // Calls "save_marks" at the end of the iteration. |
| // General signature... |
| virtual void oop_since_save_marks_iterate_v(OopsInGenClosure* cl) = 0; |
| // ...and specializations for de-virtualization. (The general |
| // implementation of the _nv versions call the virtual version. |
| // Note that the _nv suffix is not really semantically necessary, |
| // but it avoids some not-so-useful warnings on Solaris.) |
| #define Generation_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ |
| virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ |
| oop_since_save_marks_iterate_v((OopsInGenClosure*)cl); \ |
| } |
| SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(Generation_SINCE_SAVE_MARKS_DECL) |
| |
| #undef Generation_SINCE_SAVE_MARKS_DECL |
| |
| // The "requestor" generation is performing some garbage collection |
| // action for which it would be useful to have scratch space. If |
| // the target is not the requestor, no gc actions will be required |
| // of the target. The requestor promises to allocate no more than |
| // "max_alloc_words" in the target generation (via promotion say, |
| // if the requestor is a young generation and the target is older). |
| // If the target generation can provide any scratch space, it adds |
| // it to "list", leaving "list" pointing to the head of the |
| // augmented list. The default is to offer no space. |
| virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor, |
| size_t max_alloc_words) {} |
| |
| // Give each generation an opportunity to do clean up for any |
| // contributed scratch. |
| virtual void reset_scratch() {} |
| |
| // When an older generation has been collected, and perhaps resized, |
| // this method will be invoked on all younger generations (from older to |
| // younger), allowing them to resize themselves as appropriate. |
| virtual void compute_new_size() = 0; |
| |
| // Printing |
| virtual const char* name() const = 0; |
| virtual const char* short_name() const = 0; |
| |
| // Reference Processing accessor |
| ReferenceProcessor* const ref_processor() { return _ref_processor; } |
| |
| // Iteration. |
| |
| // Iterate over all the ref-containing fields of all objects in the |
| // generation, calling "cl.do_oop" on each. |
| virtual void oop_iterate(ExtendedOopClosure* cl); |
| |
| // Iterate over all objects in the generation, calling "cl.do_object" on |
| // each. |
| virtual void object_iterate(ObjectClosure* cl); |
| |
| // Iterate over all safe objects in the generation, calling "cl.do_object" on |
| // each. An object is safe if its references point to other objects in |
| // the heap. This defaults to object_iterate() unless overridden. |
| virtual void safe_object_iterate(ObjectClosure* cl); |
| |
| // Apply "cl->do_oop" to (the address of) all and only all the ref fields |
| // in the current generation that contain pointers to objects in younger |
| // generations. Objects allocated since the last "save_marks" call are |
| // excluded. |
| virtual void younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) = 0; |
| |
| // Inform a generation that it longer contains references to objects |
| // in any younger generation. [e.g. Because younger gens are empty, |
| // clear the card table.] |
| virtual void clear_remembered_set() { } |
| |
| // Inform a generation that some of its objects have moved. [e.g. The |
| // generation's spaces were compacted, invalidating the card table.] |
| virtual void invalidate_remembered_set() { } |
| |
| // Block abstraction. |
| |
| // Returns the address of the start of the "block" that contains the |
| // address "addr". We say "blocks" instead of "object" since some heaps |
| // may not pack objects densely; a chunk may either be an object or a |
| // non-object. |
| virtual HeapWord* block_start(const void* addr) const; |
| |
| // Requires "addr" to be the start of a chunk, and returns its size. |
| // "addr + size" is required to be the start of a new chunk, or the end |
| // of the active area of the heap. |
| virtual size_t block_size(const HeapWord* addr) const ; |
| |
| // Requires "addr" to be the start of a block, and returns "TRUE" iff |
| // the block is an object. |
| virtual bool block_is_obj(const HeapWord* addr) const; |
| |
| void print_heap_change(size_t prev_used) const; |
| |
| virtual void print() const; |
| virtual void print_on(outputStream* st) const; |
| |
| virtual void verify() = 0; |
| |
| struct StatRecord { |
| int invocations; |
| elapsedTimer accumulated_time; |
| StatRecord() : |
| invocations(0), |
| accumulated_time(elapsedTimer()) {} |
| }; |
| private: |
| StatRecord _stat_record; |
| public: |
| StatRecord* stat_record() { return &_stat_record; } |
| |
| virtual void print_summary_info(); |
| virtual void print_summary_info_on(outputStream* st); |
| |
| // Performance Counter support |
| virtual void update_counters() = 0; |
| virtual CollectorCounters* counters() { return _gc_counters; } |
| }; |
| |
| #endif // SHARE_VM_GC_SHARED_GENERATION_HPP |