--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/shared/generation.hpp Wed May 13 15:16:06 2015 +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<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;
+
+ // 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