--- old/src/share/vm/memory/generation.hpp 2015-05-13 13:58:36.705512466 +0200 +++ /dev/null 2015-03-18 17:10:38.111854831 +0100 @@ -1,587 +0,0 @@ -/* - * Copyright (c) 1997, 2015, 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 - * or visit www.oracle.com if you need additional information or have any - * questions. - * - */ - -#ifndef SHARE_VM_MEMORY_GENERATION_HPP -#define SHARE_VM_MEMORY_GENERATION_HPP - -#include "gc_implementation/shared/collectorCounters.hpp" -#include "memory/allocation.hpp" -#include "memory/memRegion.hpp" -#include "memory/referenceProcessor.hpp" -#include "memory/universe.hpp" -#include "memory/virtualspace.hpp" -#include "memory/watermark.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 GenRemSet; -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 { - 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; - - // Level in the generation hierarchy. - int _level; - - // ("Weak") Reference processing support - ReferenceProcessor* _ref_processor; - - // Performance Counters - CollectorCounters* _gc_counters; - - // Statistics for garbage collection - GCStats* _gc_stats; - - // Returns the next generation in the configuration, or else NULL if this - // is the highest generation. - Generation* next_gen() const; - - // Initialize the generation. - Generation(ReservedSpace rs, size_t initial_byte_size, int level); - - // 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); - - 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; } - GenerationSpec* spec(); - - // 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 enquiries (results in bytes) - 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** 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) {} - - // This generation will collect all younger generations - // during a full collection. - virtual bool full_collects_younger_generations() const { return false; } - - // This generation does in-place marking, meaning that mark words - // are mutated during the marking phase and presumably reinitialized - // to a canonical value after the GC. This is currently used by the - // biased locking implementation to determine whether additional - // work is required during the GC prologue and epilogue. - virtual bool performs_in_place_marking() const { return true; } - - // 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) { - warning("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_level is - // the level of the collection that has most recently - // occurred. 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 younger generations has completed. - GCStats* gc_stats() const { return _gc_stats; } - virtual void update_gc_stats(int current_level, 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; - - int level() const { return _level; } - - // 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) = 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; - - - // PrintGC, PrintGCDetails support - void print_heap_change(size_t prev_used) const; - - // PrintHeapAtGC support - 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_MEMORY_GENERATION_HPP --- /dev/null 2015-03-18 17:10:38.111854831 +0100 +++ new/src/share/vm/gc/shared/generation.hpp 2015-05-13 13:58:36.527505070 +0200 @@ -0,0 +1,587 @@ +/* + * Copyright (c) 1997, 2015, 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 + * or visit www.oracle.com if you need additional information or have any + * questions. + * + */ + +#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 "gc/shared/watermark.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 GenRemSet; +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 { + 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; + + // Level in the generation hierarchy. + int _level; + + // ("Weak") Reference processing support + ReferenceProcessor* _ref_processor; + + // Performance Counters + CollectorCounters* _gc_counters; + + // Statistics for garbage collection + GCStats* _gc_stats; + + // Returns the next generation in the configuration, or else NULL if this + // is the highest generation. + Generation* next_gen() const; + + // Initialize the generation. + Generation(ReservedSpace rs, size_t initial_byte_size, int level); + + // 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); + + 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; } + GenerationSpec* spec(); + + // 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 enquiries (results in bytes) + 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** 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) {} + + // This generation will collect all younger generations + // during a full collection. + virtual bool full_collects_younger_generations() const { return false; } + + // This generation does in-place marking, meaning that mark words + // are mutated during the marking phase and presumably reinitialized + // to a canonical value after the GC. This is currently used by the + // biased locking implementation to determine whether additional + // work is required during the GC prologue and epilogue. + virtual bool performs_in_place_marking() const { return true; } + + // 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) { + warning("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_level is + // the level of the collection that has most recently + // occurred. 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 younger generations has completed. + GCStats* gc_stats() const { return _gc_stats; } + virtual void update_gc_stats(int current_level, 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; + + int level() const { return _level; } + + // 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) = 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; + + + // PrintGC, PrintGCDetails support + void print_heap_change(size_t prev_used) const; + + // PrintHeapAtGC support + 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