/*
* Copyright (c) 2001, 2019, 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_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP
#define SHARE_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP
#include "gc/cms/cmsOopClosures.hpp"
#include "gc/cms/gSpaceCounters.hpp"
#include "gc/cms/yieldingWorkgroup.hpp"
#include "gc/shared/cardGeneration.hpp"
#include "gc/shared/gcHeapSummary.hpp"
#include "gc/shared/gcStats.hpp"
#include "gc/shared/gcWhen.hpp"
#include "gc/shared/generationCounters.hpp"
#include "gc/shared/space.hpp"
#include "gc/shared/taskqueue.hpp"
#include "logging/log.hpp"
#include "memory/iterator.hpp"
#include "memory/virtualspace.hpp"
#include "runtime/mutexLocker.hpp"
#include "services/memoryService.hpp"
#include "utilities/bitMap.hpp"
#include "utilities/stack.hpp"
// ConcurrentMarkSweepGeneration is in support of a concurrent
// mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
// style. We assume, for now, that this generation is always the
// seniormost generation and for simplicity
// in the first implementation, that this generation is a single compactible
// space. Neither of these restrictions appears essential, and will be
// relaxed in the future when more time is available to implement the
// greater generality (and there's a need for it).
//
// Concurrent mode failures are currently handled by
// means of a sliding mark-compact.
class AdaptiveSizePolicy;
class CMSCollector;
class CMSConcMarkingTask;
class CMSGCAdaptivePolicyCounters;
class CMSTracer;
class ConcurrentGCTimer;
class ConcurrentMarkSweepGeneration;
class ConcurrentMarkSweepPolicy;
class ConcurrentMarkSweepThread;
class CompactibleFreeListSpace;
class FreeChunk;
class ParNewGeneration;
class PromotionInfo;
class ScanMarkedObjectsAgainCarefullyClosure;
class SerialOldTracer;
// A generic CMS bit map. It's the basis for both the CMS marking bit map
// as well as for the mod union table (in each case only a subset of the
// methods are used). This is essentially a wrapper around the BitMap class,
// with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
// we have _shifter == 0. and for the mod union table we have
// shifter == CardTable::card_shift - LogHeapWordSize.)
// XXX 64-bit issues in BitMap?
class CMSBitMap {
friend class VMStructs;
HeapWord* _bmStartWord; // base address of range covered by map
size_t _bmWordSize; // map size (in #HeapWords covered)
const int _shifter; // shifts to convert HeapWord to bit position
VirtualSpace _virtual_space; // underlying the bit map
BitMapView _bm; // the bit map itself
Mutex* const _lock; // mutex protecting _bm;
public:
// constructor
CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
// allocates the actual storage for the map
bool allocate(MemRegion mr);
// field getter
Mutex* lock() const { return _lock; }
// locking verifier convenience function
void assert_locked() const PRODUCT_RETURN;
// inquiries
HeapWord* startWord() const { return _bmStartWord; }
size_t sizeInWords() const { return _bmWordSize; }
size_t sizeInBits() const { return _bm.size(); }
// the following is one past the last word in space
HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
// reading marks
bool isMarked(HeapWord* addr) const;
bool par_isMarked(HeapWord* addr) const; // do not lock checks
bool isUnmarked(HeapWord* addr) const;
bool isAllClear() const;
// writing marks
void mark(HeapWord* addr);
// For marking by parallel GC threads;
// returns true if we did, false if another thread did
bool par_mark(HeapWord* addr);
void mark_range(MemRegion mr);
void par_mark_range(MemRegion mr);
void mark_large_range(MemRegion mr);
void par_mark_large_range(MemRegion mr);
void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
void clear_range(MemRegion mr);
void par_clear_range(MemRegion mr);
void clear_large_range(MemRegion mr);
void par_clear_large_range(MemRegion mr);
void clear_all();
void clear_all_incrementally(); // Not yet implemented!!
NOT_PRODUCT(
// checks the memory region for validity
void region_invariant(MemRegion mr);
)
// iteration
void iterate(BitMapClosure* cl) {
_bm.iterate(cl);
}
void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
void dirty_range_iterate_clear(MemRegionClosure* cl);
void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
// auxiliary support for iteration
HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
HeapWord* end_addr) const;
HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
HeapWord* end_addr) const;
MemRegion getAndClearMarkedRegion(HeapWord* addr);
MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
HeapWord* end_addr);
// conversion utilities
HeapWord* offsetToHeapWord(size_t offset) const;
size_t heapWordToOffset(HeapWord* addr) const;
size_t heapWordDiffToOffsetDiff(size_t diff) const;
void print_on_error(outputStream* st, const char* prefix) const;
// debugging
// is this address range covered by the bit-map?
NOT_PRODUCT(
bool covers(MemRegion mr) const;
bool covers(HeapWord* start, size_t size = 0) const;
)
void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
};
// Represents a marking stack used by the CMS collector.
// Ideally this should be GrowableArray<> just like MSC's marking stack(s).
class CMSMarkStack: public CHeapObj<mtGC> {
friend class CMSCollector; // To get at expansion stats further below.
VirtualSpace _virtual_space; // Space for the stack
oop* _base; // Bottom of stack
size_t _index; // One more than last occupied index
size_t _capacity; // Max #elements
Mutex _par_lock; // An advisory lock used in case of parallel access
NOT_PRODUCT(size_t _max_depth;) // Max depth plumbed during run
protected:
size_t _hit_limit; // We hit max stack size limit
size_t _failed_double; // We failed expansion before hitting limit
public:
CMSMarkStack():
_par_lock(Mutex::event, "CMSMarkStack._par_lock", true,
Monitor::_safepoint_check_never),
_hit_limit(0),
_failed_double(0) {}
bool allocate(size_t size);
size_t capacity() const { return _capacity; }
oop pop() {
if (!isEmpty()) {
return _base[--_index] ;
}
return NULL;
}
bool push(oop ptr) {
if (isFull()) {
return false;
} else {
_base[_index++] = ptr;
NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
return true;
}
}
bool isEmpty() const { return _index == 0; }
bool isFull() const {
assert(_index <= _capacity, "buffer overflow");
return _index == _capacity;
}
size_t length() { return _index; }
// "Parallel versions" of some of the above
oop par_pop() {
// lock and pop
MutexLocker x(&_par_lock, Mutex::_no_safepoint_check_flag);
return pop();
}
bool par_push(oop ptr) {
// lock and push
MutexLocker x(&_par_lock, Mutex::_no_safepoint_check_flag);
return push(ptr);
}
// Forcibly reset the stack, losing all of its contents.
void reset() {
_index = 0;
}
// Expand the stack, typically in response to an overflow condition.
void expand();
// Compute the least valued stack element.
oop least_value(HeapWord* low) {
HeapWord* least = low;
for (size_t i = 0; i < _index; i++) {
least = MIN2(least, (HeapWord*)_base[i]);
}
return (oop)least;
}
// Exposed here to allow stack expansion in || case.
Mutex* par_lock() { return &_par_lock; }
};
class CardTableRS;
class CMSParGCThreadState;
class ModUnionClosure: public MemRegionClosure {
protected:
CMSBitMap* _t;
public:
ModUnionClosure(CMSBitMap* t): _t(t) { }
void do_MemRegion(MemRegion mr);
};
class ModUnionClosurePar: public ModUnionClosure {
public:
ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
void do_MemRegion(MemRegion mr);
};
// Survivor Chunk Array in support of parallelization of
// Survivor Space rescan.
class ChunkArray: public CHeapObj<mtGC> {
size_t _index;
size_t _capacity;
size_t _overflows;
HeapWord** _array; // storage for array
public:
ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
ChunkArray(HeapWord** a, size_t c):
_index(0), _capacity(c), _overflows(0), _array(a) {}
HeapWord** array() { return _array; }
void set_array(HeapWord** a) { _array = a; }
size_t capacity() { return _capacity; }
void set_capacity(size_t c) { _capacity = c; }
size_t end() {
assert(_index <= capacity(),
"_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
_index, _capacity);
return _index;
} // exclusive
HeapWord* nth(size_t n) {
assert(n < end(), "Out of bounds access");
return _array[n];
}
void reset() {
_index = 0;
if (_overflows > 0) {
log_trace(gc)("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times", _capacity, _overflows);
}
_overflows = 0;
}
void record_sample(HeapWord* p, size_t sz) {
// For now we do not do anything with the size
if (_index < _capacity) {
_array[_index++] = p;
} else {
++_overflows;
assert(_index == _capacity,
"_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
"): out of bounds at overflow#" SIZE_FORMAT,
_index, _capacity, _overflows);
}
}
};
//
// Timing, allocation and promotion statistics for gc scheduling and incremental
// mode pacing. Most statistics are exponential averages.
//
class CMSStats {
private:
ConcurrentMarkSweepGeneration* const _cms_gen; // The cms (old) gen.
// The following are exponential averages with factor alpha:
// avg = (100 - alpha) * avg + alpha * cur_sample
//
// The durations measure: end_time[n] - start_time[n]
// The periods measure: start_time[n] - start_time[n-1]
//
// The cms period and duration include only concurrent collections; time spent
// in foreground cms collections due to System.gc() or because of a failure to
// keep up are not included.
//
// There are 3 alphas to "bootstrap" the statistics. The _saved_alpha is the
// real value, but is used only after the first period. A value of 100 is
// used for the first sample so it gets the entire weight.
unsigned int _saved_alpha; // 0-100
unsigned int _gc0_alpha;
unsigned int _cms_alpha;
double _gc0_duration;
double _gc0_period;
size_t _gc0_promoted; // bytes promoted per gc0
double _cms_duration;
double _cms_duration_pre_sweep; // time from initiation to start of sweep
double _cms_period;
size_t _cms_allocated; // bytes of direct allocation per gc0 period
// Timers.
elapsedTimer _cms_timer;
TimeStamp _gc0_begin_time;
TimeStamp _cms_begin_time;
TimeStamp _cms_end_time;
// Snapshots of the amount used in the CMS generation.
size_t _cms_used_at_gc0_begin;
size_t _cms_used_at_gc0_end;
size_t _cms_used_at_cms_begin;
// Used to prevent the duty cycle from being reduced in the middle of a cms
// cycle.
bool _allow_duty_cycle_reduction;
enum {
_GC0_VALID = 0x1,
_CMS_VALID = 0x2,
_ALL_VALID = _GC0_VALID | _CMS_VALID
};
unsigned int _valid_bits;
protected:
// In support of adjusting of cms trigger ratios based on history
// of concurrent mode failure.
double cms_free_adjustment_factor(size_t free) const;
void adjust_cms_free_adjustment_factor(bool fail, size_t free);
public:
CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
unsigned int alpha = CMSExpAvgFactor);
// Whether or not the statistics contain valid data; higher level statistics
// cannot be called until this returns true (they require at least one young
// gen and one cms cycle to have completed).
bool valid() const;
// Record statistics.
void record_gc0_begin();
void record_gc0_end(size_t cms_gen_bytes_used);
void record_cms_begin();
void record_cms_end();
// Allow management of the cms timer, which must be stopped/started around
// yield points.
elapsedTimer& cms_timer() { return _cms_timer; }
void start_cms_timer() { _cms_timer.start(); }
void stop_cms_timer() { _cms_timer.stop(); }
// Basic statistics; units are seconds or bytes.
double gc0_period() const { return _gc0_period; }
double gc0_duration() const { return _gc0_duration; }
size_t gc0_promoted() const { return _gc0_promoted; }
double cms_period() const { return _cms_period; }
double cms_duration() const { return _cms_duration; }
size_t cms_allocated() const { return _cms_allocated; }
size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
// Seconds since the last background cms cycle began or ended.
double cms_time_since_begin() const;
double cms_time_since_end() const;
// Higher level statistics--caller must check that valid() returns true before
// calling.
// Returns bytes promoted per second of wall clock time.
double promotion_rate() const;
// Returns bytes directly allocated per second of wall clock time.
double cms_allocation_rate() const;
// Rate at which space in the cms generation is being consumed (sum of the
// above two).
double cms_consumption_rate() const;
// Returns an estimate of the number of seconds until the cms generation will
// fill up, assuming no collection work is done.
double time_until_cms_gen_full() const;
// Returns an estimate of the number of seconds remaining until
// the cms generation collection should start.
double time_until_cms_start() const;
// End of higher level statistics.
// Debugging.
void print_on(outputStream* st) const PRODUCT_RETURN;
void print() const { print_on(tty); }
};
// A closure related to weak references processing which
// we embed in the CMSCollector, since we need to pass
// it to the reference processor for secondary filtering
// of references based on reachability of referent;
// see role of _is_alive_non_header closure in the
// ReferenceProcessor class.
// For objects in the CMS generation, this closure checks
// if the object is "live" (reachable). Used in weak
// reference processing.
class CMSIsAliveClosure: public BoolObjectClosure {
const MemRegion _span;
const CMSBitMap* _bit_map;
friend class CMSCollector;
public:
CMSIsAliveClosure(MemRegion span,
CMSBitMap* bit_map):
_span(span),
_bit_map(bit_map) {
assert(!span.is_empty(), "Empty span could spell trouble");
}
bool do_object_b(oop obj);
};
// Implements AbstractRefProcTaskExecutor for CMS.
class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
public:
CMSRefProcTaskExecutor(CMSCollector& collector)
: _collector(collector)
{ }
// Executes a task using worker threads.
virtual void execute(ProcessTask& task, uint ergo_workers);
private:
CMSCollector& _collector;
};
class CMSCollector: public CHeapObj<mtGC> {
friend class VMStructs;
friend class ConcurrentMarkSweepThread;
friend class ConcurrentMarkSweepGeneration;
friend class CompactibleFreeListSpace;
friend class CMSParMarkTask;
friend class CMSParInitialMarkTask;
friend class CMSParRemarkTask;
friend class CMSConcMarkingTask;
friend class CMSRefProcTaskProxy;
friend class CMSRefProcTaskExecutor;
friend class ScanMarkedObjectsAgainCarefullyClosure; // for sampling eden
friend class SurvivorSpacePrecleanClosure; // --- ditto -------
friend class PushOrMarkClosure; // to access _restart_addr
friend class ParPushOrMarkClosure; // to access _restart_addr
friend class MarkFromRootsClosure; // -- ditto --
// ... and for clearing cards
friend class ParMarkFromRootsClosure; // to access _restart_addr
// ... and for clearing cards
friend class ParConcMarkingClosure; // to access _restart_addr etc.
friend class MarkFromRootsVerifyClosure; // to access _restart_addr
friend class PushAndMarkVerifyClosure; // -- ditto --
friend class MarkRefsIntoAndScanClosure; // to access _overflow_list
friend class PushAndMarkClosure; // -- ditto --
friend class ParPushAndMarkClosure; // -- ditto --
friend class CMSKeepAliveClosure; // -- ditto --
friend class CMSDrainMarkingStackClosure; // -- ditto --
friend class CMSInnerParMarkAndPushClosure; // -- ditto --
NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) // assertion on _overflow_list
friend class ReleaseForegroundGC; // to access _foregroundGCShouldWait
friend class VM_CMS_Operation;
friend class VM_CMS_Initial_Mark;
friend class VM_CMS_Final_Remark;
friend class TraceCMSMemoryManagerStats;
private:
jlong _time_of_last_gc;
void update_time_of_last_gc(jlong now) {
_time_of_last_gc = now;
}
OopTaskQueueSet* _task_queues;
// Overflow list of grey objects, threaded through mark-word
// Manipulated with CAS in the parallel/multi-threaded case.
oopDesc* volatile _overflow_list;
// The following array-pair keeps track of mark words
// displaced for accommodating overflow list above.
// This code will likely be revisited under RFE#4922830.
Stack<oop, mtGC> _preserved_oop_stack;
Stack<markWord, mtGC> _preserved_mark_stack;
// In support of multi-threaded concurrent phases
YieldingFlexibleWorkGang* _conc_workers;
// Performance Counters
CollectorCounters* _gc_counters;
CollectorCounters* _cgc_counters;
// Initialization Errors
bool _completed_initialization;
// In support of ExplicitGCInvokesConcurrent
static bool _full_gc_requested;
static GCCause::Cause _full_gc_cause;
unsigned int _collection_count_start;
// Should we unload classes this concurrent cycle?
bool _should_unload_classes;
unsigned int _concurrent_cycles_since_last_unload;
unsigned int concurrent_cycles_since_last_unload() const {
return _concurrent_cycles_since_last_unload;
}
// Did we (allow) unload classes in the previous concurrent cycle?
bool unloaded_classes_last_cycle() const {
return concurrent_cycles_since_last_unload() == 0;
}
// Root scanning options for perm gen
int _roots_scanning_options;
int roots_scanning_options() const { return _roots_scanning_options; }
void add_root_scanning_option(int o) { _roots_scanning_options |= o; }
void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o; }
// Verification support
CMSBitMap _verification_mark_bm;
void verify_after_remark_work_1();
void verify_after_remark_work_2();
// True if any verification flag is on.
bool _verifying;
bool verifying() const { return _verifying; }
void set_verifying(bool v) { _verifying = v; }
void set_did_compact(bool v);
// XXX Move these to CMSStats ??? FIX ME !!!
elapsedTimer _inter_sweep_timer; // Time between sweeps
elapsedTimer _intra_sweep_timer; // Time _in_ sweeps
// Padded decaying average estimates of the above
AdaptivePaddedAverage _inter_sweep_estimate;
AdaptivePaddedAverage _intra_sweep_estimate;
CMSTracer* _gc_tracer_cm;
ConcurrentGCTimer* _gc_timer_cm;
bool _cms_start_registered;
GCHeapSummary _last_heap_summary;
MetaspaceSummary _last_metaspace_summary;
void register_gc_start(GCCause::Cause cause);
void register_gc_end();
void save_heap_summary();
void report_heap_summary(GCWhen::Type when);
protected:
ConcurrentMarkSweepGeneration* _cmsGen; // Old gen (CMS)
MemRegion _span; // Span covering above
CardTableRS* _ct; // Card table
// CMS marking support structures
CMSBitMap _markBitMap;
CMSBitMap _modUnionTable;
CMSMarkStack _markStack;
HeapWord* _restart_addr; // In support of marking stack overflow
void lower_restart_addr(HeapWord* low);
// Counters in support of marking stack / work queue overflow handling:
// a non-zero value indicates certain types of overflow events during
// the current CMS cycle and could lead to stack resizing efforts at
// an opportune future time.
size_t _ser_pmc_preclean_ovflw;
size_t _ser_pmc_remark_ovflw;
size_t _par_pmc_remark_ovflw;
size_t _ser_kac_preclean_ovflw;
size_t _ser_kac_ovflw;
size_t _par_kac_ovflw;
NOT_PRODUCT(ssize_t _num_par_pushes;)
// ("Weak") Reference processing support.
SpanSubjectToDiscoveryClosure _span_based_discoverer;
ReferenceProcessor* _ref_processor;
CMSIsAliveClosure _is_alive_closure;
// Keep this textually after _markBitMap and _span; c'tor dependency.
ConcurrentMarkSweepThread* _cmsThread; // The thread doing the work
ModUnionClosurePar _modUnionClosurePar;
// CMS abstract state machine
// initial_state: Idling
// next_state(Idling) = {Marking}
// next_state(Marking) = {Precleaning, Sweeping}
// next_state(Precleaning) = {AbortablePreclean, FinalMarking}
// next_state(AbortablePreclean) = {FinalMarking}
// next_state(FinalMarking) = {Sweeping}
// next_state(Sweeping) = {Resizing}
// next_state(Resizing) = {Resetting}
// next_state(Resetting) = {Idling}
// The numeric values below are chosen so that:
// . _collectorState <= Idling == post-sweep && pre-mark
// . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
// precleaning || abortablePrecleanb
public:
enum CollectorState {
Resizing = 0,
Resetting = 1,
Idling = 2,
InitialMarking = 3,
Marking = 4,
Precleaning = 5,
AbortablePreclean = 6,
FinalMarking = 7,
Sweeping = 8
};
protected:
static CollectorState _collectorState;
// State related to prologue/epilogue invocation for my generations
bool _between_prologue_and_epilogue;
// Signaling/State related to coordination between fore- and background GC
// Note: When the baton has been passed from background GC to foreground GC,
// _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
static bool _foregroundGCIsActive; // true iff foreground collector is active or
// wants to go active
static bool _foregroundGCShouldWait; // true iff background GC is active and has not
// yet passed the baton to the foreground GC
// Support for CMSScheduleRemark (abortable preclean)
bool _abort_preclean;
bool _start_sampling;
int _numYields;
size_t _numDirtyCards;
size_t _sweep_count;
// Occupancy used for bootstrapping stats
double _bootstrap_occupancy;
// Timer
elapsedTimer _timer;
// Timing, allocation and promotion statistics, used for scheduling.
CMSStats _stats;
enum CMS_op_type {
CMS_op_checkpointRootsInitial,
CMS_op_checkpointRootsFinal
};
void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
bool stop_world_and_do(CMS_op_type op);
OopTaskQueueSet* task_queues() { return _task_queues; }
YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
// Support for parallelizing Eden rescan in CMS remark phase
void sample_eden(); // ... sample Eden space top
private:
// Support for parallelizing young gen rescan in CMS remark phase
ParNewGeneration* _young_gen;
HeapWord* volatile* _top_addr; // ... Top of Eden
HeapWord** _end_addr; // ... End of Eden
Mutex* _eden_chunk_lock;
HeapWord** _eden_chunk_array; // ... Eden partitioning array
size_t _eden_chunk_index; // ... top (exclusive) of array
size_t _eden_chunk_capacity; // ... max entries in array
// Support for parallelizing survivor space rescan
HeapWord** _survivor_chunk_array;
size_t _survivor_chunk_index;
size_t _survivor_chunk_capacity;
size_t* _cursor;
ChunkArray* _survivor_plab_array;
// Support for marking stack overflow handling
bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
bool par_take_from_overflow_list(size_t num,
OopTaskQueue* to_work_q,
int no_of_gc_threads);
void push_on_overflow_list(oop p);
void par_push_on_overflow_list(oop p);
// The following is, obviously, not, in general, "MT-stable"
bool overflow_list_is_empty() const;
void preserve_mark_if_necessary(oop p);
void par_preserve_mark_if_necessary(oop p);
void preserve_mark_work(oop p, markWord m);
void restore_preserved_marks_if_any();
NOT_PRODUCT(bool no_preserved_marks() const;)
// In support of testing overflow code
NOT_PRODUCT(int _overflow_counter;)
NOT_PRODUCT(bool simulate_overflow();) // Sequential
NOT_PRODUCT(bool par_simulate_overflow();) // MT version
// CMS work methods
void checkpointRootsInitialWork(); // Initial checkpoint work
// A return value of false indicates failure due to stack overflow
bool markFromRootsWork(); // Concurrent marking work
public: // FIX ME!!! only for testing
bool do_marking_st(); // Single-threaded marking
bool do_marking_mt(); // Multi-threaded marking
private:
// Concurrent precleaning work
size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* old_gen,
ScanMarkedObjectsAgainCarefullyClosure* cl);
size_t preclean_card_table(ConcurrentMarkSweepGeneration* old_gen,
ScanMarkedObjectsAgainCarefullyClosure* cl);
// Does precleaning work, returning a quantity indicative of
// the amount of "useful work" done.
size_t preclean_work(bool clean_refs, bool clean_survivors);
void preclean_cld(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
void abortable_preclean(); // Preclean while looking for possible abort
void initialize_sequential_subtasks_for_young_gen_rescan(int i);
// Helper function for above; merge-sorts the per-thread plab samples
void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
// Resets (i.e. clears) the per-thread plab sample vectors
void reset_survivor_plab_arrays();
// Final (second) checkpoint work
void checkpointRootsFinalWork();
// Work routine for parallel version of remark
void do_remark_parallel();
// Work routine for non-parallel version of remark
void do_remark_non_parallel();
// Reference processing work routine (during second checkpoint)
void refProcessingWork();
// Concurrent sweeping work
void sweepWork(ConcurrentMarkSweepGeneration* old_gen);
// Concurrent resetting of support data structures
void reset_concurrent();
// Resetting of support data structures from a STW full GC
void reset_stw();
// Clear _expansion_cause fields of constituent generations
void clear_expansion_cause();
// An auxiliary method used to record the ends of
// used regions of each generation to limit the extent of sweep
void save_sweep_limits();
// A work method used by the foreground collector to do
// a mark-sweep-compact.
void do_compaction_work(bool clear_all_soft_refs);
// Work methods for reporting concurrent mode interruption or failure
bool is_external_interruption();
void report_concurrent_mode_interruption();
// If the background GC is active, acquire control from the background
// GC and do the collection.
void acquire_control_and_collect(bool full, bool clear_all_soft_refs);
// For synchronizing passing of control from background to foreground
// GC. waitForForegroundGC() is called by the background
// collector. It if had to wait for a foreground collection,
// it returns true and the background collection should assume
// that the collection was finished by the foreground
// collector.
bool waitForForegroundGC();
size_t block_size_using_printezis_bits(HeapWord* addr) const;
size_t block_size_if_printezis_bits(HeapWord* addr) const;
HeapWord* next_card_start_after_block(HeapWord* addr) const;
void setup_cms_unloading_and_verification_state();
public:
CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
CardTableRS* ct);
ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
MemRegion ref_processor_span() const { return _span_based_discoverer.span(); }
ReferenceProcessor* ref_processor() { return _ref_processor; }
void ref_processor_init();
Mutex* bitMapLock() const { return _markBitMap.lock(); }
static CollectorState abstract_state() { return _collectorState; }
bool should_abort_preclean() const; // Whether preclean should be aborted.
size_t get_eden_used() const;
size_t get_eden_capacity() const;
ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
// Locking checks
NOT_PRODUCT(static bool have_cms_token();)
bool shouldConcurrentCollect();
void collect(bool full,
bool clear_all_soft_refs,
size_t size,
bool tlab);
void collect_in_background(GCCause::Cause cause);
// In support of ExplicitGCInvokesConcurrent
static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
// Should we unload classes in a particular concurrent cycle?
bool should_unload_classes() const {
return _should_unload_classes;
}
void update_should_unload_classes();
void direct_allocated(HeapWord* start, size_t size);
// Object is dead if not marked and current phase is sweeping.
bool is_dead_obj(oop obj) const;
// After a promotion (of "start"), do any necessary marking.
// If "par", then it's being done by a parallel GC thread.
// The last two args indicate if we need precise marking
// and if so the size of the object so it can be dirtied
// in its entirety.
void promoted(bool par, HeapWord* start,
bool is_obj_array, size_t obj_size);
void getFreelistLocks() const;
void releaseFreelistLocks() const;
bool haveFreelistLocks() const;
// Adjust size of underlying generation
void compute_new_size();
// GC prologue and epilogue
void gc_prologue(bool full);
void gc_epilogue(bool full);
jlong time_of_last_gc(jlong now) {
if (_collectorState <= Idling) {
// gc not in progress
return _time_of_last_gc;
} else {
// collection in progress
return now;
}
}
// Support for parallel remark of survivor space
void* get_data_recorder(int thr_num);
void sample_eden_chunk();
CMSBitMap* markBitMap() { return &_markBitMap; }
void directAllocated(HeapWord* start, size_t size);
// Main CMS steps and related support
void checkpointRootsInitial();
bool markFromRoots(); // a return value of false indicates failure
// due to stack overflow
void preclean();
void checkpointRootsFinal();
void sweep();
// Check that the currently executing thread is the expected
// one (foreground collector or background collector).
static void check_correct_thread_executing() PRODUCT_RETURN;
NOT_PRODUCT(bool is_cms_reachable(HeapWord* addr);)
// Performance Counter Support
CollectorCounters* counters() { return _gc_counters; }
CollectorCounters* cgc_counters() { return _cgc_counters; }
// Timer stuff
void startTimer() { assert(!_timer.is_active(), "Error"); _timer.start(); }
void stopTimer() { assert( _timer.is_active(), "Error"); _timer.stop(); }
void resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset(); }
jlong timerTicks() { assert(!_timer.is_active(), "Error"); return _timer.ticks(); }
int yields() { return _numYields; }
void resetYields() { _numYields = 0; }
void incrementYields() { _numYields++; }
void resetNumDirtyCards() { _numDirtyCards = 0; }
void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
size_t numDirtyCards() { return _numDirtyCards; }
static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
size_t sweep_count() const { return _sweep_count; }
void increment_sweep_count() { _sweep_count++; }
// Timers/stats for gc scheduling and incremental mode pacing.
CMSStats& stats() { return _stats; }
// Adaptive size policy
AdaptiveSizePolicy* size_policy();
static void print_on_error(outputStream* st);
// Debugging
void verify();
bool verify_after_remark();
void verify_ok_to_terminate() const PRODUCT_RETURN;
void verify_work_stacks_empty() const PRODUCT_RETURN;
void verify_overflow_empty() const PRODUCT_RETURN;
// Convenience methods in support of debugging
static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
// Accessors
CMSMarkStack* verification_mark_stack() { return &_markStack; }
CMSBitMap* verification_mark_bm() { return &_verification_mark_bm; }
// Initialization errors
bool completed_initialization() { return _completed_initialization; }
void print_eden_and_survivor_chunk_arrays();
ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
};
class CMSExpansionCause : public AllStatic {
public:
enum Cause {
_no_expansion,
_satisfy_free_ratio,
_satisfy_promotion,
_satisfy_allocation,
_allocate_par_lab,
_allocate_par_spooling_space,
_adaptive_size_policy
};
// Return a string describing the cause of the expansion.
static const char* to_string(CMSExpansionCause::Cause cause);
};
class ConcurrentMarkSweepGeneration: public CardGeneration {
friend class VMStructs;
friend class ConcurrentMarkSweepThread;
friend class ConcurrentMarkSweep;
friend class CMSCollector;
protected:
static CMSCollector* _collector; // the collector that collects us
CompactibleFreeListSpace* _cmsSpace; // underlying space (only one for now)
// Performance Counters
GenerationCounters* _gen_counters;
GSpaceCounters* _space_counters;
// Words directly allocated, used by CMSStats.
size_t _direct_allocated_words;
// Non-product stat counters
NOT_PRODUCT(
size_t _numObjectsPromoted;
size_t _numWordsPromoted;
size_t _numObjectsAllocated;
size_t _numWordsAllocated;
)
// Used for sizing decisions
bool _incremental_collection_failed;
bool incremental_collection_failed() {
return _incremental_collection_failed;
}
void set_incremental_collection_failed() {
_incremental_collection_failed = true;
}
void clear_incremental_collection_failed() {
_incremental_collection_failed = false;
}
// accessors
void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
// Accessing spaces
CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; }
private:
// For parallel young-gen GC support.
CMSParGCThreadState** _par_gc_thread_states;
// Reason generation was expanded
CMSExpansionCause::Cause _expansion_cause;
// In support of MinChunkSize being larger than min object size
const double _dilatation_factor;
// True if a compacting collection was done.
bool _did_compact;
bool did_compact() { return _did_compact; }
// Fraction of current occupancy at which to start a CMS collection which
// will collect this generation (at least).
double _initiating_occupancy;
protected:
// Shrink generation by specified size (returns false if unable to shrink)
void shrink_free_list_by(size_t bytes);
// Update statistics for GC
virtual void update_gc_stats(Generation* current_generation, bool full);
// Maximum available space in the generation (including uncommitted)
// space.
size_t max_available() const;
// getter and initializer for _initiating_occupancy field.
double initiating_occupancy() const { return _initiating_occupancy; }
void init_initiating_occupancy(intx io, uintx tr);
void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause);
void assert_correct_size_change_locking();
public:
ConcurrentMarkSweepGeneration(ReservedSpace rs,
size_t initial_byte_size,
size_t min_byte_size,
size_t max_byte_size,
CardTableRS* ct);
// Accessors
CMSCollector* collector() const { return _collector; }
static void set_collector(CMSCollector* collector) {
assert(_collector == NULL, "already set");
_collector = collector;
}
CompactibleFreeListSpace* cmsSpace() const { return _cmsSpace; }
Mutex* freelistLock() const;
virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
void set_did_compact(bool v) { _did_compact = v; }
bool refs_discovery_is_atomic() const { return false; }
bool refs_discovery_is_mt() const {
// Note: CMS does MT-discovery during the parallel-remark
// phases. Use ReferenceProcessorMTMutator to make refs
// discovery MT-safe during such phases or other parallel
// discovery phases in the future. This may all go away
// if/when we decide that refs discovery is sufficiently
// rare that the cost of the CAS's involved is in the
// noise. That's a measurement that should be done, and
// the code simplified if that turns out to be the case.
return ConcGCThreads > 1;
}
// Override
virtual void ref_processor_init();
void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
// Space enquiries
double occupancy() const { return ((double)used())/((double)capacity()); }
size_t contiguous_available() const;
size_t unsafe_max_alloc_nogc() const;
size_t used_stable() const;
// over-rides
MemRegion used_region_at_save_marks() const;
// Adjust quantities in the generation affected by
// the compaction.
void reset_after_compaction();
// Allocation support
HeapWord* allocate(size_t size, bool tlab);
HeapWord* have_lock_and_allocate(size_t size, bool tlab);
oop promote(oop obj, size_t obj_size);
HeapWord* par_allocate(size_t size, bool tlab) {
return allocate(size, tlab);
}
// Used by CMSStats to track direct allocation. The value is sampled and
// reset after each young gen collection.
size_t direct_allocated_words() const { return _direct_allocated_words; }
void reset_direct_allocated_words() { _direct_allocated_words = 0; }
// Overrides for parallel promotion.
virtual oop par_promote(int thread_num,
oop obj, markWord m, size_t word_sz);
virtual void par_promote_alloc_done(int thread_num);
virtual void par_oop_since_save_marks_iterate_done(int thread_num);
virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
// Inform this (old) generation that a promotion failure was
// encountered during a collection of the young generation.
virtual void promotion_failure_occurred();
bool should_collect(bool full, size_t size, bool tlab);
virtual bool should_concurrent_collect() const;
virtual bool is_too_full() const;
void collect(bool full,
bool clear_all_soft_refs,
size_t size,
bool tlab);
HeapWord* expand_and_allocate(size_t word_size,
bool tlab,
bool parallel = false);
// GC prologue and epilogue
void gc_prologue(bool full);
void gc_prologue_work(bool full, bool registerClosure,
ModUnionClosure* modUnionClosure);
void gc_epilogue(bool full);
void gc_epilogue_work(bool full);
// Time since last GC of this generation
jlong time_of_last_gc(jlong now) {
return collector()->time_of_last_gc(now);
}
void update_time_of_last_gc(jlong now) {
collector()-> update_time_of_last_gc(now);
}
// Allocation failure
void shrink(size_t bytes);
HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
bool expand_and_ensure_spooling_space(PromotionInfo* promo);
// Iteration support and related enquiries
void save_marks();
bool no_allocs_since_save_marks();
// Iteration support specific to CMS generations
void save_sweep_limit();
// More iteration support
virtual void oop_iterate(OopIterateClosure* cl);
virtual void safe_object_iterate(ObjectClosure* cl);
virtual void object_iterate(ObjectClosure* cl);
template <typename OopClosureType>
void oop_since_save_marks_iterate(OopClosureType* cl);
// Smart allocation XXX -- move to CFLSpace?
void setNearLargestChunk();
bool isNearLargestChunk(HeapWord* addr);
// Get the chunk at the end of the space. Delegates to
// the space.
FreeChunk* find_chunk_at_end();
void post_compact();
// Debugging
void prepare_for_verify();
void verify();
void print_statistics() PRODUCT_RETURN;
// Performance Counters support
virtual void update_counters();
virtual void update_counters(size_t used);
void initialize_performance_counters(size_t min_old_size, size_t max_old_size);
CollectorCounters* counters() { return collector()->counters(); }
// Support for parallel remark of survivor space
void* get_data_recorder(int thr_num) {
//Delegate to collector
return collector()->get_data_recorder(thr_num);
}
void sample_eden_chunk() {
//Delegate to collector
return collector()->sample_eden_chunk();
}
// Printing
const char* name() const;
virtual const char* short_name() const { return "CMS"; }
void print() const;
// Resize the generation after a compacting GC. The
// generation can be treated as a contiguous space
// after the compaction.
virtual void compute_new_size();
// Resize the generation after a non-compacting
// collection.
void compute_new_size_free_list();
};
//
// Closures of various sorts used by CMS to accomplish its work
//
// This closure is used to do concurrent marking from the roots
// following the first checkpoint.
class MarkFromRootsClosure: public BitMapClosure {
CMSCollector* _collector;
MemRegion _span;
CMSBitMap* _bitMap;
CMSBitMap* _mut;
CMSMarkStack* _markStack;
bool _yield;
int _skipBits;
HeapWord* _finger;
HeapWord* _threshold;
DEBUG_ONLY(bool _verifying;)
public:
MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
CMSBitMap* bitMap,
CMSMarkStack* markStack,
bool should_yield, bool verifying = false);
bool do_bit(size_t offset);
void reset(HeapWord* addr);
inline void do_yield_check();
private:
void scanOopsInOop(HeapWord* ptr);
void do_yield_work();
};
// This closure is used to do concurrent multi-threaded
// marking from the roots following the first checkpoint.
// XXX This should really be a subclass of The serial version
// above, but i have not had the time to refactor things cleanly.
class ParMarkFromRootsClosure: public BitMapClosure {
CMSCollector* _collector;
MemRegion _whole_span;
MemRegion _span;
CMSBitMap* _bit_map;
CMSBitMap* _mut;
OopTaskQueue* _work_queue;
CMSMarkStack* _overflow_stack;
int _skip_bits;
HeapWord* _finger;
HeapWord* _threshold;
CMSConcMarkingTask* _task;
public:
ParMarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
MemRegion span,
CMSBitMap* bit_map,
OopTaskQueue* work_queue,
CMSMarkStack* overflow_stack);
bool do_bit(size_t offset);
inline void do_yield_check();
private:
void scan_oops_in_oop(HeapWord* ptr);
void do_yield_work();
bool get_work_from_overflow_stack();
};
// The following closures are used to do certain kinds of verification of
// CMS marking.
class PushAndMarkVerifyClosure: public MetadataVisitingOopIterateClosure {
CMSCollector* _collector;
MemRegion _span;
CMSBitMap* _verification_bm;
CMSBitMap* _cms_bm;
CMSMarkStack* _mark_stack;
protected:
void do_oop(oop p);
template <class T> void do_oop_work(T *p);
public:
PushAndMarkVerifyClosure(CMSCollector* cms_collector,
MemRegion span,
CMSBitMap* verification_bm,
CMSBitMap* cms_bm,
CMSMarkStack* mark_stack);
void do_oop(oop* p);
void do_oop(narrowOop* p);
// Deal with a stack overflow condition
void handle_stack_overflow(HeapWord* lost);
};
class MarkFromRootsVerifyClosure: public BitMapClosure {
CMSCollector* _collector;
MemRegion _span;
CMSBitMap* _verification_bm;
CMSBitMap* _cms_bm;
CMSMarkStack* _mark_stack;
HeapWord* _finger;
PushAndMarkVerifyClosure _pam_verify_closure;
public:
MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
CMSBitMap* verification_bm,
CMSBitMap* cms_bm,
CMSMarkStack* mark_stack);
bool do_bit(size_t offset);
void reset(HeapWord* addr);
};
// This closure is used to check that a certain set of bits is
// "empty" (i.e. the bit vector doesn't have any 1-bits).
class FalseBitMapClosure: public BitMapClosure {
public:
bool do_bit(size_t offset) {
guarantee(false, "Should not have a 1 bit");
return true;
}
};
// A version of ObjectClosure with "memory" (see _previous_address below)
class UpwardsObjectClosure: public BoolObjectClosure {
HeapWord* _previous_address;
public:
UpwardsObjectClosure() : _previous_address(NULL) { }
void set_previous(HeapWord* addr) { _previous_address = addr; }
HeapWord* previous() { return _previous_address; }
// A return value of "true" can be used by the caller to decide
// if this object's end should *NOT* be recorded in
// _previous_address above.
virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
};
// This closure is used during the second checkpointing phase
// to rescan the marked objects on the dirty cards in the mod
// union table and the card table proper. It's invoked via
// MarkFromDirtyCardsClosure below. It uses either
// [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
// declared in genOopClosures.hpp to accomplish some of its work.
// In the parallel case the bitMap is shared, so access to
// it needs to be suitably synchronized for updates by embedded
// closures that update it; however, this closure itself only
// reads the bit_map and because it is idempotent, is immune to
// reading stale values.
class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
#ifdef ASSERT
CMSCollector* _collector;
MemRegion _span;
union {
CMSMarkStack* _mark_stack;
OopTaskQueue* _work_queue;
};
#endif // ASSERT
bool _parallel;
CMSBitMap* _bit_map;
union {
MarkRefsIntoAndScanClosure* _scan_closure;
ParMarkRefsIntoAndScanClosure* _par_scan_closure;
};
public:
ScanMarkedObjectsAgainClosure(CMSCollector* collector,
MemRegion span,
ReferenceProcessor* rp,
CMSBitMap* bit_map,
CMSMarkStack* mark_stack,
MarkRefsIntoAndScanClosure* cl):
#ifdef ASSERT
_collector(collector),
_span(span),
_mark_stack(mark_stack),
#endif // ASSERT
_parallel(false),
_bit_map(bit_map),
_scan_closure(cl) { }
ScanMarkedObjectsAgainClosure(CMSCollector* collector,
MemRegion span,
ReferenceProcessor* rp,
CMSBitMap* bit_map,
OopTaskQueue* work_queue,
ParMarkRefsIntoAndScanClosure* cl):
#ifdef ASSERT
_collector(collector),
_span(span),
_work_queue(work_queue),
#endif // ASSERT
_parallel(true),
_bit_map(bit_map),
_par_scan_closure(cl) { }
bool do_object_b(oop obj) {
guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
return false;
}
bool do_object_bm(oop p, MemRegion mr);
};
// This closure is used during the second checkpointing phase
// to rescan the marked objects on the dirty cards in the mod
// union table and the card table proper. It invokes
// ScanMarkedObjectsAgainClosure above to accomplish much of its work.
// In the parallel case, the bit map is shared and requires
// synchronized access.
class MarkFromDirtyCardsClosure: public MemRegionClosure {
CompactibleFreeListSpace* _space;
ScanMarkedObjectsAgainClosure _scan_cl;
size_t _num_dirty_cards;
public:
MarkFromDirtyCardsClosure(CMSCollector* collector,
MemRegion span,
CompactibleFreeListSpace* space,
CMSBitMap* bit_map,
CMSMarkStack* mark_stack,
MarkRefsIntoAndScanClosure* cl):
_space(space),
_scan_cl(collector, span, collector->ref_processor(), bit_map,
mark_stack, cl),
_num_dirty_cards(0) { }
MarkFromDirtyCardsClosure(CMSCollector* collector,
MemRegion span,
CompactibleFreeListSpace* space,
CMSBitMap* bit_map,
OopTaskQueue* work_queue,
ParMarkRefsIntoAndScanClosure* cl):
_space(space),
_scan_cl(collector, span, collector->ref_processor(), bit_map,
work_queue, cl),
_num_dirty_cards(0) { }
void do_MemRegion(MemRegion mr);
void set_space(CompactibleFreeListSpace* space) { _space = space; }
size_t num_dirty_cards() { return _num_dirty_cards; }
};
// This closure is used in the non-product build to check
// that there are no MemRegions with a certain property.
class FalseMemRegionClosure: public MemRegionClosure {
void do_MemRegion(MemRegion mr) {
guarantee(!mr.is_empty(), "Shouldn't be empty");
guarantee(false, "Should never be here");
}
};
// This closure is used during the precleaning phase
// to "carefully" rescan marked objects on dirty cards.
// It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
// to accomplish some of its work.
class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
CMSCollector* _collector;
MemRegion _span;
bool _yield;
Mutex* _freelistLock;
CMSBitMap* _bitMap;
CMSMarkStack* _markStack;
MarkRefsIntoAndScanClosure* _scanningClosure;
DEBUG_ONLY(HeapWord* _last_scanned_object;)
public:
ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
MemRegion span,
CMSBitMap* bitMap,
CMSMarkStack* markStack,
MarkRefsIntoAndScanClosure* cl,
bool should_yield):
_collector(collector),
_span(span),
_yield(should_yield),
_bitMap(bitMap),
_markStack(markStack),
_scanningClosure(cl)
DEBUG_ONLY(COMMA _last_scanned_object(NULL))
{ }
void do_object(oop p) {
guarantee(false, "call do_object_careful instead");
}
size_t do_object_careful(oop p) {
guarantee(false, "Unexpected caller");
return 0;
}
size_t do_object_careful_m(oop p, MemRegion mr);
void setFreelistLock(Mutex* m) {
_freelistLock = m;
_scanningClosure->set_freelistLock(m);
}
private:
inline bool do_yield_check();
void do_yield_work();
};
class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
CMSCollector* _collector;
MemRegion _span;
bool _yield;
CMSBitMap* _bit_map;
CMSMarkStack* _mark_stack;
PushAndMarkClosure* _scanning_closure;
unsigned int _before_count;
public:
SurvivorSpacePrecleanClosure(CMSCollector* collector,
MemRegion span,
CMSBitMap* bit_map,
CMSMarkStack* mark_stack,
PushAndMarkClosure* cl,
unsigned int before_count,
bool should_yield):
_collector(collector),
_span(span),
_yield(should_yield),
_bit_map(bit_map),
_mark_stack(mark_stack),
_scanning_closure(cl),
_before_count(before_count)
{ }
void do_object(oop p) {
guarantee(false, "call do_object_careful instead");
}
size_t do_object_careful(oop p);
size_t do_object_careful_m(oop p, MemRegion mr) {
guarantee(false, "Unexpected caller");
return 0;
}
private:
inline void do_yield_check();
void do_yield_work();
};
// This closure is used to accomplish the sweeping work
// after the second checkpoint but before the concurrent reset
// phase.
//
// Terminology
// left hand chunk (LHC) - block of one or more chunks currently being
// coalesced. The LHC is available for coalescing with a new chunk.
// right hand chunk (RHC) - block that is currently being swept that is
// free or garbage that can be coalesced with the LHC.
// _inFreeRange is true if there is currently a LHC
// _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
// _freeRangeInFreeLists is true if the LHC is in the free lists.
// _freeFinger is the address of the current LHC
class SweepClosure: public BlkClosureCareful {
CMSCollector* _collector; // collector doing the work
ConcurrentMarkSweepGeneration* _g; // Generation being swept
CompactibleFreeListSpace* _sp; // Space being swept
HeapWord* _limit;// the address at or above which the sweep should stop
// because we do not expect newly garbage blocks
// eligible for sweeping past that address.
Mutex* _freelistLock; // Free list lock (in space)
CMSBitMap* _bitMap; // Marking bit map (in
// generation)
bool _inFreeRange; // Indicates if we are in the
// midst of a free run
bool _freeRangeInFreeLists;
// Often, we have just found
// a free chunk and started
// a new free range; we do not
// eagerly remove this chunk from
// the free lists unless there is
// a possibility of coalescing.
// When true, this flag indicates
// that the _freeFinger below
// points to a potentially free chunk
// that may still be in the free lists
bool _lastFreeRangeCoalesced;
// free range contains chunks
// coalesced
bool _yield;
// Whether sweeping should be
// done with yields. For instance
// when done by the foreground
// collector we shouldn't yield.
HeapWord* _freeFinger; // When _inFreeRange is set, the
// pointer to the "left hand
// chunk"
size_t _freeRangeSize;
// When _inFreeRange is set, this
// indicates the accumulated size
// of the "left hand chunk"
NOT_PRODUCT(
size_t _numObjectsFreed;
size_t _numWordsFreed;
size_t _numObjectsLive;
size_t _numWordsLive;
size_t _numObjectsAlreadyFree;
size_t _numWordsAlreadyFree;
FreeChunk* _last_fc;
)
private:
// Code that is common to a free chunk or garbage when
// encountered during sweeping.
void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
// Process a free chunk during sweeping.
void do_already_free_chunk(FreeChunk *fc);
// Work method called when processing an already free or a
// freshly garbage chunk to do a lookahead and possibly a
// preemptive flush if crossing over _limit.
void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
// Process a garbage chunk during sweeping.
size_t do_garbage_chunk(FreeChunk *fc);
// Process a live chunk during sweeping.
size_t do_live_chunk(FreeChunk* fc);
// Accessors.
HeapWord* freeFinger() const { return _freeFinger; }
void set_freeFinger(HeapWord* v) { _freeFinger = v; }
bool inFreeRange() const { return _inFreeRange; }
void set_inFreeRange(bool v) { _inFreeRange = v; }
bool lastFreeRangeCoalesced() const { return _lastFreeRangeCoalesced; }
void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
bool freeRangeInFreeLists() const { return _freeRangeInFreeLists; }
void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
// Initialize a free range.
void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
// Return this chunk to the free lists.
void flush_cur_free_chunk(HeapWord* chunk, size_t size);
// Check if we should yield and do so when necessary.
inline void do_yield_check(HeapWord* addr);
// Yield
void do_yield_work(HeapWord* addr);
// Debugging/Printing
void print_free_block_coalesced(FreeChunk* fc) const;
public:
SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
CMSBitMap* bitMap, bool should_yield);
~SweepClosure() PRODUCT_RETURN;
size_t do_blk_careful(HeapWord* addr);
void print() const { print_on(tty); }
void print_on(outputStream *st) const;
};
// Closures related to weak references processing
// During CMS' weak reference processing, this is a
// work-routine/closure used to complete transitive
// marking of objects as live after a certain point
// in which an initial set has been completely accumulated.
// This closure is currently used both during the final
// remark stop-world phase, as well as during the concurrent
// precleaning of the discovered reference lists.
class CMSDrainMarkingStackClosure: public VoidClosure {
CMSCollector* _collector;
MemRegion _span;
CMSMarkStack* _mark_stack;
CMSBitMap* _bit_map;
CMSKeepAliveClosure* _keep_alive;
bool _concurrent_precleaning;
public:
CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
CMSBitMap* bit_map, CMSMarkStack* mark_stack,
CMSKeepAliveClosure* keep_alive,
bool cpc):
_collector(collector),
_span(span),
_mark_stack(mark_stack),
_bit_map(bit_map),
_keep_alive(keep_alive),
_concurrent_precleaning(cpc) {
assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
"Mismatch");
}
void do_void();
};
// A parallel version of CMSDrainMarkingStackClosure above.
class CMSParDrainMarkingStackClosure: public VoidClosure {
CMSCollector* _collector;
MemRegion _span;
OopTaskQueue* _work_queue;
CMSBitMap* _bit_map;
CMSInnerParMarkAndPushClosure _mark_and_push;
public:
CMSParDrainMarkingStackClosure(CMSCollector* collector,
MemRegion span, CMSBitMap* bit_map,
OopTaskQueue* work_queue):
_collector(collector),
_span(span),
_work_queue(work_queue),
_bit_map(bit_map),
_mark_and_push(collector, span, bit_map, work_queue) { }
public:
void trim_queue(uint max);
void do_void();
};
// Allow yielding or short-circuiting of reference list
// precleaning work.
class CMSPrecleanRefsYieldClosure: public YieldClosure {
CMSCollector* _collector;
void do_yield_work();
public:
CMSPrecleanRefsYieldClosure(CMSCollector* collector):
_collector(collector) {}
virtual bool should_return();
};
// Convenience class that locks free list locks for given CMS collector
class FreelistLocker: public StackObj {
private:
CMSCollector* _collector;
public:
FreelistLocker(CMSCollector* collector):
_collector(collector) {
_collector->getFreelistLocks();
}
~FreelistLocker() {
_collector->releaseFreelistLocks();
}
};
// Mark all dead objects in a given space.
class MarkDeadObjectsClosure: public BlkClosure {
const CMSCollector* _collector;
const CompactibleFreeListSpace* _sp;
CMSBitMap* _live_bit_map;
CMSBitMap* _dead_bit_map;
public:
MarkDeadObjectsClosure(const CMSCollector* collector,
const CompactibleFreeListSpace* sp,
CMSBitMap *live_bit_map,
CMSBitMap *dead_bit_map) :
_collector(collector),
_sp(sp),
_live_bit_map(live_bit_map),
_dead_bit_map(dead_bit_map) {}
size_t do_blk(HeapWord* addr);
};
class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
public:
TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
};
#endif // SHARE_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP