8009940: G1: assert(_finger == _heap_end) failed, concurrentMark.cpp:809
Summary: Skip reference processing if the global marking stack overflows during remark. Refactor and rename set_phase(); move code that sets the concurrency level into its own routine. Do not call set_phase() from within parallel reference processing; use the concurrency level routine instead. The marking state should only set reset by CMTask[0] during the concurrent phase of the marking cycle; if an overflow occurs at any stage during the remark, the marking state will be reset after reference processing.
Reviewed-by: brutisso, jmasa
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#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
#define SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
#include "gc_implementation/g1/heapRegionSets.hpp"
#include "utilities/taskqueue.hpp"
class G1CollectedHeap;
class CMTask;
typedef GenericTaskQueue<oop, mtGC> CMTaskQueue;
typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet;
// Closure used by CM during concurrent reference discovery
// and reference processing (during remarking) to determine
// if a particular object is alive. It is primarily used
// to determine if referents of discovered reference objects
// are alive. An instance is also embedded into the
// reference processor as the _is_alive_non_header field
class G1CMIsAliveClosure: public BoolObjectClosure {
G1CollectedHeap* _g1;
public:
G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
void do_object(oop obj) {
ShouldNotCallThis();
}
bool do_object_b(oop obj);
};
// A generic CM bit map. This is essentially a wrapper around the BitMap
// class, with one bit per (1<<_shifter) HeapWords.
class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
protected:
HeapWord* _bmStartWord; // base address of range covered by map
size_t _bmWordSize; // map size (in #HeapWords covered)
const int _shifter; // map to char or bit
VirtualSpace _virtual_space; // underlying the bit map
BitMap _bm; // the bit map itself
public:
// constructor
CMBitMapRO(int shifter);
enum { do_yield = true };
// inquiries
HeapWord* startWord() const { return _bmStartWord; }
size_t sizeInWords() const { return _bmWordSize; }
// the following is one past the last word in space
HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
// read marks
bool isMarked(HeapWord* addr) const {
assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
"outside underlying space?");
return _bm.at(heapWordToOffset(addr));
}
// iteration
inline bool iterate(BitMapClosure* cl, MemRegion mr);
inline bool iterate(BitMapClosure* cl);
// Return the address corresponding to the next marked bit at or after
// "addr", and before "limit", if "limit" is non-NULL. If there is no
// such bit, returns "limit" if that is non-NULL, or else "endWord()".
HeapWord* getNextMarkedWordAddress(HeapWord* addr,
HeapWord* limit = NULL) const;
// Return the address corresponding to the next unmarked bit at or after
// "addr", and before "limit", if "limit" is non-NULL. If there is no
// such bit, returns "limit" if that is non-NULL, or else "endWord()".
HeapWord* getNextUnmarkedWordAddress(HeapWord* addr,
HeapWord* limit = NULL) const;
// conversion utilities
HeapWord* offsetToHeapWord(size_t offset) const {
return _bmStartWord + (offset << _shifter);
}
size_t heapWordToOffset(HeapWord* addr) const {
return pointer_delta(addr, _bmStartWord) >> _shifter;
}
int heapWordDiffToOffsetDiff(size_t diff) const;
// The argument addr should be the start address of a valid object
HeapWord* nextObject(HeapWord* addr) {
oop obj = (oop) addr;
HeapWord* res = addr + obj->size();
assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity");
return res;
}
// debugging
NOT_PRODUCT(bool covers(ReservedSpace rs) const;)
};
class CMBitMap : public CMBitMapRO {
public:
// constructor
CMBitMap(int shifter) :
CMBitMapRO(shifter) {}
// Allocates the back store for the marking bitmap
bool allocate(ReservedSpace heap_rs);
// write marks
void mark(HeapWord* addr) {
assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
"outside underlying space?");
_bm.set_bit(heapWordToOffset(addr));
}
void clear(HeapWord* addr) {
assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
"outside underlying space?");
_bm.clear_bit(heapWordToOffset(addr));
}
bool parMark(HeapWord* addr) {
assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
"outside underlying space?");
return _bm.par_set_bit(heapWordToOffset(addr));
}
bool parClear(HeapWord* addr) {
assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
"outside underlying space?");
return _bm.par_clear_bit(heapWordToOffset(addr));
}
void markRange(MemRegion mr);
void clearAll();
void clearRange(MemRegion mr);
// Starting at the bit corresponding to "addr" (inclusive), find the next
// "1" bit, if any. This bit starts some run of consecutive "1"'s; find
// the end of this run (stopping at "end_addr"). Return the MemRegion
// covering from the start of the region corresponding to the first bit
// of the run to the end of the region corresponding to the last bit of
// the run. If there is no "1" bit at or after "addr", return an empty
// MemRegion.
MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
};
// Represents a marking stack used by ConcurrentMarking in the G1 collector.
class CMMarkStack VALUE_OBJ_CLASS_SPEC {
VirtualSpace _virtual_space; // Underlying backing store for actual stack
ConcurrentMark* _cm;
oop* _base; // bottom of stack
jint _index; // one more than last occupied index
jint _capacity; // max #elements
jint _saved_index; // value of _index saved at start of GC
NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run
bool _overflow;
bool _should_expand;
DEBUG_ONLY(bool _drain_in_progress;)
DEBUG_ONLY(bool _drain_in_progress_yields;)
public:
CMMarkStack(ConcurrentMark* cm);
~CMMarkStack();
#ifndef PRODUCT
jint max_depth() const {
return _max_depth;
}
#endif
bool allocate(size_t capacity);
oop pop() {
if (!isEmpty()) {
return _base[--_index] ;
}
return NULL;
}
// If overflow happens, don't do the push, and record the overflow.
// *Requires* that "ptr" is already marked.
void push(oop ptr) {
if (isFull()) {
// Record overflow.
_overflow = true;
return;
} else {
_base[_index++] = ptr;
NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
}
}
// Non-block impl. Note: concurrency is allowed only with other
// "par_push" operations, not with "pop" or "drain". We would need
// parallel versions of them if such concurrency was desired.
void par_push(oop ptr);
// Pushes the first "n" elements of "ptr_arr" on the stack.
// Non-block impl. Note: concurrency is allowed only with other
// "par_adjoin_arr" or "push" operations, not with "pop" or "drain".
void par_adjoin_arr(oop* ptr_arr, int n);
// Pushes the first "n" elements of "ptr_arr" on the stack.
// Locking impl: concurrency is allowed only with
// "par_push_arr" and/or "par_pop_arr" operations, which use the same
// locking strategy.
void par_push_arr(oop* ptr_arr, int n);
// If returns false, the array was empty. Otherwise, removes up to "max"
// elements from the stack, and transfers them to "ptr_arr" in an
// unspecified order. The actual number transferred is given in "n" ("n
// == 0" is deliberately redundant with the return value.) Locking impl:
// concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
// operations, which use the same locking strategy.
bool par_pop_arr(oop* ptr_arr, int max, int* n);
// Drain the mark stack, applying the given closure to all fields of
// objects on the stack. (That is, continue until the stack is empty,
// even if closure applications add entries to the stack.) The "bm"
// argument, if non-null, may be used to verify that only marked objects
// are on the mark stack. If "yield_after" is "true", then the
// concurrent marker performing the drain offers to yield after
// processing each object. If a yield occurs, stops the drain operation
// and returns false. Otherwise, returns true.
template<class OopClosureClass>
bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
bool isEmpty() { return _index == 0; }
bool isFull() { return _index == _capacity; }
int maxElems() { return _capacity; }
bool overflow() { return _overflow; }
void clear_overflow() { _overflow = false; }
bool should_expand() const { return _should_expand; }
void set_should_expand();
// Expand the stack, typically in response to an overflow condition
void expand();
int size() { return _index; }
void setEmpty() { _index = 0; clear_overflow(); }
// Record the current index.
void note_start_of_gc();
// Make sure that we have not added any entries to the stack during GC.
void note_end_of_gc();
// iterate over the oops in the mark stack, up to the bound recorded via
// the call above.
void oops_do(OopClosure* f);
};
class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC {
private:
#ifndef PRODUCT
uintx _num_remaining;
bool _force;
#endif // !defined(PRODUCT)
public:
void init() PRODUCT_RETURN;
void update() PRODUCT_RETURN;
bool should_force() PRODUCT_RETURN_( return false; );
};
// this will enable a variety of different statistics per GC task
#define _MARKING_STATS_ 0
// this will enable the higher verbose levels
#define _MARKING_VERBOSE_ 0
#if _MARKING_STATS_
#define statsOnly(statement) \
do { \
statement ; \
} while (0)
#else // _MARKING_STATS_
#define statsOnly(statement) \
do { \
} while (0)
#endif // _MARKING_STATS_
typedef enum {
no_verbose = 0, // verbose turned off
stats_verbose, // only prints stats at the end of marking
low_verbose, // low verbose, mostly per region and per major event
medium_verbose, // a bit more detailed than low
high_verbose // per object verbose
} CMVerboseLevel;
class YoungList;
// Root Regions are regions that are not empty at the beginning of a
// marking cycle and which we might collect during an evacuation pause
// while the cycle is active. Given that, during evacuation pauses, we
// do not copy objects that are explicitly marked, what we have to do
// for the root regions is to scan them and mark all objects reachable
// from them. According to the SATB assumptions, we only need to visit
// each object once during marking. So, as long as we finish this scan
// before the next evacuation pause, we can copy the objects from the
// root regions without having to mark them or do anything else to them.
//
// Currently, we only support root region scanning once (at the start
// of the marking cycle) and the root regions are all the survivor
// regions populated during the initial-mark pause.
class CMRootRegions VALUE_OBJ_CLASS_SPEC {
private:
YoungList* _young_list;
ConcurrentMark* _cm;
volatile bool _scan_in_progress;
volatile bool _should_abort;
HeapRegion* volatile _next_survivor;
public:
CMRootRegions();
// We actually do most of the initialization in this method.
void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
// Reset the claiming / scanning of the root regions.
void prepare_for_scan();
// Forces get_next() to return NULL so that the iteration aborts early.
void abort() { _should_abort = true; }
// Return true if the CM thread are actively scanning root regions,
// false otherwise.
bool scan_in_progress() { return _scan_in_progress; }
// Claim the next root region to scan atomically, or return NULL if
// all have been claimed.
HeapRegion* claim_next();
// Flag that we're done with root region scanning and notify anyone
// who's waiting on it. If aborted is false, assume that all regions
// have been claimed.
void scan_finished();
// If CM threads are still scanning root regions, wait until they
// are done. Return true if we had to wait, false otherwise.
bool wait_until_scan_finished();
};
class ConcurrentMarkThread;
class ConcurrentMark: public CHeapObj<mtGC> {
friend class CMMarkStack;
friend class ConcurrentMarkThread;
friend class CMTask;
friend class CMBitMapClosure;
friend class CMGlobalObjectClosure;
friend class CMRemarkTask;
friend class CMConcurrentMarkingTask;
friend class G1ParNoteEndTask;
friend class CalcLiveObjectsClosure;
friend class G1CMRefProcTaskProxy;
friend class G1CMRefProcTaskExecutor;
friend class G1CMKeepAliveAndDrainClosure;
friend class G1CMDrainMarkingStackClosure;
protected:
ConcurrentMarkThread* _cmThread; // the thread doing the work
G1CollectedHeap* _g1h; // the heap.
uint _parallel_marking_threads; // the number of marking
// threads we're use
uint _max_parallel_marking_threads; // max number of marking
// threads we'll ever use
double _sleep_factor; // how much we have to sleep, with
// respect to the work we just did, to
// meet the marking overhead goal
double _marking_task_overhead; // marking target overhead for
// a single task
// same as the two above, but for the cleanup task
double _cleanup_sleep_factor;
double _cleanup_task_overhead;
FreeRegionList _cleanup_list;
// Concurrent marking support structures
CMBitMap _markBitMap1;
CMBitMap _markBitMap2;
CMBitMapRO* _prevMarkBitMap; // completed mark bitmap
CMBitMap* _nextMarkBitMap; // under-construction mark bitmap
BitMap _region_bm;
BitMap _card_bm;
// Heap bounds
HeapWord* _heap_start;
HeapWord* _heap_end;
// Root region tracking and claiming.
CMRootRegions _root_regions;
// For gray objects
CMMarkStack _markStack; // Grey objects behind global finger.
HeapWord* volatile _finger; // the global finger, region aligned,
// always points to the end of the
// last claimed region
// marking tasks
uint _max_worker_id;// maximum worker id
uint _active_tasks; // task num currently active
CMTask** _tasks; // task queue array (max_worker_id len)
CMTaskQueueSet* _task_queues; // task queue set
ParallelTaskTerminator _terminator; // for termination
// Two sync barriers that are used to synchronise tasks when an
// overflow occurs. The algorithm is the following. All tasks enter
// the first one to ensure that they have all stopped manipulating
// the global data structures. After they exit it, they re-initialise
// their data structures and task 0 re-initialises the global data
// structures. Then, they enter the second sync barrier. This
// ensure, that no task starts doing work before all data
// structures (local and global) have been re-initialised. When they
// exit it, they are free to start working again.
WorkGangBarrierSync _first_overflow_barrier_sync;
WorkGangBarrierSync _second_overflow_barrier_sync;
// this is set by any task, when an overflow on the global data
// structures is detected.
volatile bool _has_overflown;
// true: marking is concurrent, false: we're in remark
volatile bool _concurrent;
// set at the end of a Full GC so that marking aborts
volatile bool _has_aborted;
// used when remark aborts due to an overflow to indicate that
// another concurrent marking phase should start
volatile bool _restart_for_overflow;
// This is true from the very start of concurrent marking until the
// point when all the tasks complete their work. It is really used
// to determine the points between the end of concurrent marking and
// time of remark.
volatile bool _concurrent_marking_in_progress;
// verbose level
CMVerboseLevel _verbose_level;
// All of these times are in ms.
NumberSeq _init_times;
NumberSeq _remark_times;
NumberSeq _remark_mark_times;
NumberSeq _remark_weak_ref_times;
NumberSeq _cleanup_times;
double _total_counting_time;
double _total_rs_scrub_time;
double* _accum_task_vtime; // accumulated task vtime
FlexibleWorkGang* _parallel_workers;
ForceOverflowSettings _force_overflow_conc;
ForceOverflowSettings _force_overflow_stw;
void weakRefsWork(bool clear_all_soft_refs);
void swapMarkBitMaps();
// It resets the global marking data structures, as well as the
// task local ones; should be called during initial mark.
void reset();
// Resets all the marking data structures. Called when we have to restart
// marking or when marking completes (via set_non_marking_state below).
void reset_marking_state(bool clear_overflow = true);
// We do this after we're done with marking so that the marking data
// structures are initialised to a sensible and predictable state.
void set_non_marking_state();
// Called to indicate how many threads are currently active.
void set_concurrency(uint active_tasks);
// It should be called to indicate which phase we're in (concurrent
// mark or remark) and how many threads are currently active.
void set_concurrency_and_phase(uint active_tasks, bool concurrent);
// prints all gathered CM-related statistics
void print_stats();
bool cleanup_list_is_empty() {
return _cleanup_list.is_empty();
}
// accessor methods
uint parallel_marking_threads() const { return _parallel_marking_threads; }
uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
double sleep_factor() { return _sleep_factor; }
double marking_task_overhead() { return _marking_task_overhead;}
double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
double cleanup_task_overhead() { return _cleanup_task_overhead;}
bool use_parallel_marking_threads() const {
assert(parallel_marking_threads() <=
max_parallel_marking_threads(), "sanity");
assert((_parallel_workers == NULL && parallel_marking_threads() == 0) ||
parallel_marking_threads() > 0,
"parallel workers not set up correctly");
return _parallel_workers != NULL;
}
HeapWord* finger() { return _finger; }
bool concurrent() { return _concurrent; }
uint active_tasks() { return _active_tasks; }
ParallelTaskTerminator* terminator() { return &_terminator; }
// It claims the next available region to be scanned by a marking
// task/thread. It might return NULL if the next region is empty or
// we have run out of regions. In the latter case, out_of_regions()
// determines whether we've really run out of regions or the task
// should call claim_region() again. This might seem a bit
// awkward. Originally, the code was written so that claim_region()
// either successfully returned with a non-empty region or there
// were no more regions to be claimed. The problem with this was
// that, in certain circumstances, it iterated over large chunks of
// the heap finding only empty regions and, while it was working, it
// was preventing the calling task to call its regular clock
// method. So, this way, each task will spend very little time in
// claim_region() and is allowed to call the regular clock method
// frequently.
HeapRegion* claim_region(uint worker_id);
// It determines whether we've run out of regions to scan.
bool out_of_regions() { return _finger == _heap_end; }
// Returns the task with the given id
CMTask* task(int id) {
assert(0 <= id && id < (int) _active_tasks,
"task id not within active bounds");
return _tasks[id];
}
// Returns the task queue with the given id
CMTaskQueue* task_queue(int id) {
assert(0 <= id && id < (int) _active_tasks,
"task queue id not within active bounds");
return (CMTaskQueue*) _task_queues->queue(id);
}
// Returns the task queue set
CMTaskQueueSet* task_queues() { return _task_queues; }
// Access / manipulation of the overflow flag which is set to
// indicate that the global stack has overflown
bool has_overflown() { return _has_overflown; }
void set_has_overflown() { _has_overflown = true; }
void clear_has_overflown() { _has_overflown = false; }
bool restart_for_overflow() { return _restart_for_overflow; }
bool has_aborted() { return _has_aborted; }
// Methods to enter the two overflow sync barriers
void enter_first_sync_barrier(uint worker_id);
void enter_second_sync_barrier(uint worker_id);
ForceOverflowSettings* force_overflow_conc() {
return &_force_overflow_conc;
}
ForceOverflowSettings* force_overflow_stw() {
return &_force_overflow_stw;
}
ForceOverflowSettings* force_overflow() {
if (concurrent()) {
return force_overflow_conc();
} else {
return force_overflow_stw();
}
}
// Live Data Counting data structures...
// These data structures are initialized at the start of
// marking. They are written to while marking is active.
// They are aggregated during remark; the aggregated values
// are then used to populate the _region_bm, _card_bm, and
// the total live bytes, which are then subsequently updated
// during cleanup.
// An array of bitmaps (one bit map per task). Each bitmap
// is used to record the cards spanned by the live objects
// marked by that task/worker.
BitMap* _count_card_bitmaps;
// Used to record the number of marked live bytes
// (for each region, by worker thread).
size_t** _count_marked_bytes;
// Card index of the bottom of the G1 heap. Used for biasing indices into
// the card bitmaps.
intptr_t _heap_bottom_card_num;
// Set to true when initialization is complete
bool _completed_initialization;
public:
// Manipulation of the global mark stack.
// Notice that the first mark_stack_push is CAS-based, whereas the
// two below are Mutex-based. This is OK since the first one is only
// called during evacuation pauses and doesn't compete with the
// other two (which are called by the marking tasks during
// concurrent marking or remark).
bool mark_stack_push(oop p) {
_markStack.par_push(p);
if (_markStack.overflow()) {
set_has_overflown();
return false;
}
return true;
}
bool mark_stack_push(oop* arr, int n) {
_markStack.par_push_arr(arr, n);
if (_markStack.overflow()) {
set_has_overflown();
return false;
}
return true;
}
void mark_stack_pop(oop* arr, int max, int* n) {
_markStack.par_pop_arr(arr, max, n);
}
size_t mark_stack_size() { return _markStack.size(); }
size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
bool mark_stack_overflow() { return _markStack.overflow(); }
bool mark_stack_empty() { return _markStack.isEmpty(); }
CMRootRegions* root_regions() { return &_root_regions; }
bool concurrent_marking_in_progress() {
return _concurrent_marking_in_progress;
}
void set_concurrent_marking_in_progress() {
_concurrent_marking_in_progress = true;
}
void clear_concurrent_marking_in_progress() {
_concurrent_marking_in_progress = false;
}
void update_accum_task_vtime(int i, double vtime) {
_accum_task_vtime[i] += vtime;
}
double all_task_accum_vtime() {
double ret = 0.0;
for (uint i = 0; i < _max_worker_id; ++i)
ret += _accum_task_vtime[i];
return ret;
}
// Attempts to steal an object from the task queues of other tasks
bool try_stealing(uint worker_id, int* hash_seed, oop& obj) {
return _task_queues->steal(worker_id, hash_seed, obj);
}
ConcurrentMark(G1CollectedHeap* g1h, ReservedSpace heap_rs);
~ConcurrentMark();
ConcurrentMarkThread* cmThread() { return _cmThread; }
CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
// Returns the number of GC threads to be used in a concurrent
// phase based on the number of GC threads being used in a STW
// phase.
uint scale_parallel_threads(uint n_par_threads);
// Calculates the number of GC threads to be used in a concurrent phase.
uint calc_parallel_marking_threads();
// The following three are interaction between CM and
// G1CollectedHeap
// This notifies CM that a root during initial-mark needs to be
// grayed. It is MT-safe. word_size is the size of the object in
// words. It is passed explicitly as sometimes we cannot calculate
// it from the given object because it might be in an inconsistent
// state (e.g., in to-space and being copied). So the caller is
// responsible for dealing with this issue (e.g., get the size from
// the from-space image when the to-space image might be
// inconsistent) and always passing the size. hr is the region that
// contains the object and it's passed optionally from callers who
// might already have it (no point in recalculating it).
inline void grayRoot(oop obj, size_t word_size,
uint worker_id, HeapRegion* hr = NULL);
// It iterates over the heap and for each object it comes across it
// will dump the contents of its reference fields, as well as
// liveness information for the object and its referents. The dump
// will be written to a file with the following name:
// G1PrintReachableBaseFile + "." + str.
// vo decides whether the prev (vo == UsePrevMarking), the next
// (vo == UseNextMarking) marking information, or the mark word
// (vo == UseMarkWord) will be used to determine the liveness of
// each object / referent.
// If all is true, all objects in the heap will be dumped, otherwise
// only the live ones. In the dump the following symbols / breviations
// are used:
// M : an explicitly live object (its bitmap bit is set)
// > : an implicitly live object (over tams)
// O : an object outside the G1 heap (typically: in the perm gen)
// NOT : a reference field whose referent is not live
// AND MARKED : indicates that an object is both explicitly and
// implicitly live (it should be one or the other, not both)
void print_reachable(const char* str,
VerifyOption vo, bool all) PRODUCT_RETURN;
// Clear the next marking bitmap (will be called concurrently).
void clearNextBitmap();
// These two do the work that needs to be done before and after the
// initial root checkpoint. Since this checkpoint can be done at two
// different points (i.e. an explicit pause or piggy-backed on a
// young collection), then it's nice to be able to easily share the
// pre/post code. It might be the case that we can put everything in
// the post method. TP
void checkpointRootsInitialPre();
void checkpointRootsInitialPost();
// Scan all the root regions and mark everything reachable from
// them.
void scanRootRegions();
// Scan a single root region and mark everything reachable from it.
void scanRootRegion(HeapRegion* hr, uint worker_id);
// Do concurrent phase of marking, to a tentative transitive closure.
void markFromRoots();
void checkpointRootsFinal(bool clear_all_soft_refs);
void checkpointRootsFinalWork();
void cleanup();
void completeCleanup();
// Mark in the previous bitmap. NB: this is usually read-only, so use
// this carefully!
inline void markPrev(oop p);
// Clears marks for all objects in the given range, for the prev,
// next, or both bitmaps. NB: the previous bitmap is usually
// read-only, so use this carefully!
void clearRangePrevBitmap(MemRegion mr);
void clearRangeNextBitmap(MemRegion mr);
void clearRangeBothBitmaps(MemRegion mr);
// Notify data structures that a GC has started.
void note_start_of_gc() {
_markStack.note_start_of_gc();
}
// Notify data structures that a GC is finished.
void note_end_of_gc() {
_markStack.note_end_of_gc();
}
// Verify that there are no CSet oops on the stacks (taskqueues /
// global mark stack), enqueued SATB buffers, per-thread SATB
// buffers, and fingers (global / per-task). The boolean parameters
// decide which of the above data structures to verify. If marking
// is not in progress, it's a no-op.
void verify_no_cset_oops(bool verify_stacks,
bool verify_enqueued_buffers,
bool verify_thread_buffers,
bool verify_fingers) PRODUCT_RETURN;
// It is called at the end of an evacuation pause during marking so
// that CM is notified of where the new end of the heap is. It
// doesn't do anything if concurrent_marking_in_progress() is false,
// unless the force parameter is true.
void update_g1_committed(bool force = false);
bool isMarked(oop p) const {
assert(p != NULL && p->is_oop(), "expected an oop");
HeapWord* addr = (HeapWord*)p;
assert(addr >= _nextMarkBitMap->startWord() ||
addr < _nextMarkBitMap->endWord(), "in a region");
return _nextMarkBitMap->isMarked(addr);
}
inline bool not_yet_marked(oop p) const;
// XXX Debug code
bool containing_card_is_marked(void* p);
bool containing_cards_are_marked(void* start, void* last);
bool isPrevMarked(oop p) const {
assert(p != NULL && p->is_oop(), "expected an oop");
HeapWord* addr = (HeapWord*)p;
assert(addr >= _prevMarkBitMap->startWord() ||
addr < _prevMarkBitMap->endWord(), "in a region");
return _prevMarkBitMap->isMarked(addr);
}
inline bool do_yield_check(uint worker_i = 0);
inline bool should_yield();
// Called to abort the marking cycle after a Full GC takes palce.
void abort();
// This prints the global/local fingers. It is used for debugging.
NOT_PRODUCT(void print_finger();)
void print_summary_info();
void print_worker_threads_on(outputStream* st) const;
// The following indicate whether a given verbose level has been
// set. Notice that anything above stats is conditional to
// _MARKING_VERBOSE_ having been set to 1
bool verbose_stats() {
return _verbose_level >= stats_verbose;
}
bool verbose_low() {
return _MARKING_VERBOSE_ && _verbose_level >= low_verbose;
}
bool verbose_medium() {
return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose;
}
bool verbose_high() {
return _MARKING_VERBOSE_ && _verbose_level >= high_verbose;
}
// Liveness counting
// Utility routine to set an exclusive range of cards on the given
// card liveness bitmap
inline void set_card_bitmap_range(BitMap* card_bm,
BitMap::idx_t start_idx,
BitMap::idx_t end_idx,
bool is_par);
// Returns the card number of the bottom of the G1 heap.
// Used in biasing indices into accounting card bitmaps.
intptr_t heap_bottom_card_num() const {
return _heap_bottom_card_num;
}
// Returns the card bitmap for a given task or worker id.
BitMap* count_card_bitmap_for(uint worker_id) {
assert(0 <= worker_id && worker_id < _max_worker_id, "oob");
assert(_count_card_bitmaps != NULL, "uninitialized");
BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
return task_card_bm;
}
// Returns the array containing the marked bytes for each region,
// for the given worker or task id.
size_t* count_marked_bytes_array_for(uint worker_id) {
assert(0 <= worker_id && worker_id < _max_worker_id, "oob");
assert(_count_marked_bytes != NULL, "uninitialized");
size_t* marked_bytes_array = _count_marked_bytes[worker_id];
assert(marked_bytes_array != NULL, "uninitialized");
return marked_bytes_array;
}
// Returns the index in the liveness accounting card table bitmap
// for the given address
inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
// Counts the size of the given memory region in the the given
// marked_bytes array slot for the given HeapRegion.
// Sets the bits in the given card bitmap that are associated with the
// cards that are spanned by the memory region.
inline void count_region(MemRegion mr, HeapRegion* hr,
size_t* marked_bytes_array,
BitMap* task_card_bm);
// Counts the given memory region in the task/worker counting
// data structures for the given worker id.
inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id);
// Counts the given memory region in the task/worker counting
// data structures for the given worker id.
inline void count_region(MemRegion mr, uint worker_id);
// Counts the given object in the given task/worker counting
// data structures.
inline void count_object(oop obj, HeapRegion* hr,
size_t* marked_bytes_array,
BitMap* task_card_bm);
// Counts the given object in the task/worker counting data
// structures for the given worker id.
inline void count_object(oop obj, HeapRegion* hr, uint worker_id);
// Attempts to mark the given object and, if successful, counts
// the object in the given task/worker counting structures.
inline bool par_mark_and_count(oop obj, HeapRegion* hr,
size_t* marked_bytes_array,
BitMap* task_card_bm);
// Attempts to mark the given object and, if successful, counts
// the object in the task/worker counting structures for the
// given worker id.
inline bool par_mark_and_count(oop obj, size_t word_size,
HeapRegion* hr, uint worker_id);
// Attempts to mark the given object and, if successful, counts
// the object in the task/worker counting structures for the
// given worker id.
inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id);
// Similar to the above routine but we don't know the heap region that
// contains the object to be marked/counted, which this routine looks up.
inline bool par_mark_and_count(oop obj, uint worker_id);
// Similar to the above routine but there are times when we cannot
// safely calculate the size of obj due to races and we, therefore,
// pass the size in as a parameter. It is the caller's reponsibility
// to ensure that the size passed in for obj is valid.
inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id);
// Unconditionally mark the given object, and unconditinally count
// the object in the counting structures for worker id 0.
// Should *not* be called from parallel code.
inline bool mark_and_count(oop obj, HeapRegion* hr);
// Similar to the above routine but we don't know the heap region that
// contains the object to be marked/counted, which this routine looks up.
// Should *not* be called from parallel code.
inline bool mark_and_count(oop obj);
// Returns true if initialization was successfully completed.
bool completed_initialization() const {
return _completed_initialization;
}
protected:
// Clear all the per-task bitmaps and arrays used to store the
// counting data.
void clear_all_count_data();
// Aggregates the counting data for each worker/task
// that was constructed while marking. Also sets
// the amount of marked bytes for each region and
// the top at concurrent mark count.
void aggregate_count_data();
// Verification routine
void verify_count_data();
};
// A class representing a marking task.
class CMTask : public TerminatorTerminator {
private:
enum PrivateConstants {
// the regular clock call is called once the scanned words reaches
// this limit
words_scanned_period = 12*1024,
// the regular clock call is called once the number of visited
// references reaches this limit
refs_reached_period = 384,
// initial value for the hash seed, used in the work stealing code
init_hash_seed = 17,
// how many entries will be transferred between global stack and
// local queues
global_stack_transfer_size = 16
};
uint _worker_id;
G1CollectedHeap* _g1h;
ConcurrentMark* _cm;
CMBitMap* _nextMarkBitMap;
// the task queue of this task
CMTaskQueue* _task_queue;
private:
// the task queue set---needed for stealing
CMTaskQueueSet* _task_queues;
// indicates whether the task has been claimed---this is only for
// debugging purposes
bool _claimed;
// number of calls to this task
int _calls;
// when the virtual timer reaches this time, the marking step should
// exit
double _time_target_ms;
// the start time of the current marking step
double _start_time_ms;
// the oop closure used for iterations over oops
G1CMOopClosure* _cm_oop_closure;
// the region this task is scanning, NULL if we're not scanning any
HeapRegion* _curr_region;
// the local finger of this task, NULL if we're not scanning a region
HeapWord* _finger;
// limit of the region this task is scanning, NULL if we're not scanning one
HeapWord* _region_limit;
// the number of words this task has scanned
size_t _words_scanned;
// When _words_scanned reaches this limit, the regular clock is
// called. Notice that this might be decreased under certain
// circumstances (i.e. when we believe that we did an expensive
// operation).
size_t _words_scanned_limit;
// the initial value of _words_scanned_limit (i.e. what it was
// before it was decreased).
size_t _real_words_scanned_limit;
// the number of references this task has visited
size_t _refs_reached;
// When _refs_reached reaches this limit, the regular clock is
// called. Notice this this might be decreased under certain
// circumstances (i.e. when we believe that we did an expensive
// operation).
size_t _refs_reached_limit;
// the initial value of _refs_reached_limit (i.e. what it was before
// it was decreased).
size_t _real_refs_reached_limit;
// used by the work stealing stuff
int _hash_seed;
// if this is true, then the task has aborted for some reason
bool _has_aborted;
// set when the task aborts because it has met its time quota
bool _has_timed_out;
// true when we're draining SATB buffers; this avoids the task
// aborting due to SATB buffers being available (as we're already
// dealing with them)
bool _draining_satb_buffers;
// number sequence of past step times
NumberSeq _step_times_ms;
// elapsed time of this task
double _elapsed_time_ms;
// termination time of this task
double _termination_time_ms;
// when this task got into the termination protocol
double _termination_start_time_ms;
// true when the task is during a concurrent phase, false when it is
// in the remark phase (so, in the latter case, we do not have to
// check all the things that we have to check during the concurrent
// phase, i.e. SATB buffer availability...)
bool _concurrent;
TruncatedSeq _marking_step_diffs_ms;
// Counting data structures. Embedding the task's marked_bytes_array
// and card bitmap into the actual task saves having to go through
// the ConcurrentMark object.
size_t* _marked_bytes_array;
BitMap* _card_bm;
// LOTS of statistics related with this task
#if _MARKING_STATS_
NumberSeq _all_clock_intervals_ms;
double _interval_start_time_ms;
int _aborted;
int _aborted_overflow;
int _aborted_cm_aborted;
int _aborted_yield;
int _aborted_timed_out;
int _aborted_satb;
int _aborted_termination;
int _steal_attempts;
int _steals;
int _clock_due_to_marking;
int _clock_due_to_scanning;
int _local_pushes;
int _local_pops;
int _local_max_size;
int _objs_scanned;
int _global_pushes;
int _global_pops;
int _global_max_size;
int _global_transfers_to;
int _global_transfers_from;
int _regions_claimed;
int _objs_found_on_bitmap;
int _satb_buffers_processed;
#endif // _MARKING_STATS_
// it updates the local fields after this task has claimed
// a new region to scan
void setup_for_region(HeapRegion* hr);
// it brings up-to-date the limit of the region
void update_region_limit();
// called when either the words scanned or the refs visited limit
// has been reached
void reached_limit();
// recalculates the words scanned and refs visited limits
void recalculate_limits();
// decreases the words scanned and refs visited limits when we reach
// an expensive operation
void decrease_limits();
// it checks whether the words scanned or refs visited reached their
// respective limit and calls reached_limit() if they have
void check_limits() {
if (_words_scanned >= _words_scanned_limit ||
_refs_reached >= _refs_reached_limit) {
reached_limit();
}
}
// this is supposed to be called regularly during a marking step as
// it checks a bunch of conditions that might cause the marking step
// to abort
void regular_clock_call();
bool concurrent() { return _concurrent; }
public:
// It resets the task; it should be called right at the beginning of
// a marking phase.
void reset(CMBitMap* _nextMarkBitMap);
// it clears all the fields that correspond to a claimed region.
void clear_region_fields();
void set_concurrent(bool concurrent) { _concurrent = concurrent; }
// The main method of this class which performs a marking step
// trying not to exceed the given duration. However, it might exit
// prematurely, according to some conditions (i.e. SATB buffers are
// available for processing).
void do_marking_step(double target_ms,
bool do_termination,
bool is_serial);
// These two calls start and stop the timer
void record_start_time() {
_elapsed_time_ms = os::elapsedTime() * 1000.0;
}
void record_end_time() {
_elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
}
// returns the worker ID associated with this task.
uint worker_id() { return _worker_id; }
// From TerminatorTerminator. It determines whether this task should
// exit the termination protocol after it's entered it.
virtual bool should_exit_termination();
// Resets the local region fields after a task has finished scanning a
// region; or when they have become stale as a result of the region
// being evacuated.
void giveup_current_region();
HeapWord* finger() { return _finger; }
bool has_aborted() { return _has_aborted; }
void set_has_aborted() { _has_aborted = true; }
void clear_has_aborted() { _has_aborted = false; }
bool has_timed_out() { return _has_timed_out; }
bool claimed() { return _claimed; }
void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
// It grays the object by marking it and, if necessary, pushing it
// on the local queue
inline void deal_with_reference(oop obj);
// It scans an object and visits its children.
void scan_object(oop obj);
// It pushes an object on the local queue.
inline void push(oop obj);
// These two move entries to/from the global stack.
void move_entries_to_global_stack();
void get_entries_from_global_stack();
// It pops and scans objects from the local queue. If partially is
// true, then it stops when the queue size is of a given limit. If
// partially is false, then it stops when the queue is empty.
void drain_local_queue(bool partially);
// It moves entries from the global stack to the local queue and
// drains the local queue. If partially is true, then it stops when
// both the global stack and the local queue reach a given size. If
// partially if false, it tries to empty them totally.
void drain_global_stack(bool partially);
// It keeps picking SATB buffers and processing them until no SATB
// buffers are available.
void drain_satb_buffers();
// moves the local finger to a new location
inline void move_finger_to(HeapWord* new_finger) {
assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
_finger = new_finger;
}
CMTask(uint worker_id, ConcurrentMark *cm,
size_t* marked_bytes, BitMap* card_bm,
CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
// it prints statistics associated with this task
void print_stats();
#if _MARKING_STATS_
void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
#endif // _MARKING_STATS_
};
// Class that's used to to print out per-region liveness
// information. It's currently used at the end of marking and also
// after we sort the old regions at the end of the cleanup operation.
class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
private:
outputStream* _out;
// Accumulators for these values.
size_t _total_used_bytes;
size_t _total_capacity_bytes;
size_t _total_prev_live_bytes;
size_t _total_next_live_bytes;
// These are set up when we come across a "stars humongous" region
// (as this is where most of this information is stored, not in the
// subsequent "continues humongous" regions). After that, for every
// region in a given humongous region series we deduce the right
// values for it by simply subtracting the appropriate amount from
// these fields. All these values should reach 0 after we've visited
// the last region in the series.
size_t _hum_used_bytes;
size_t _hum_capacity_bytes;
size_t _hum_prev_live_bytes;
size_t _hum_next_live_bytes;
static double perc(size_t val, size_t total) {
if (total == 0) {
return 0.0;
} else {
return 100.0 * ((double) val / (double) total);
}
}
static double bytes_to_mb(size_t val) {
return (double) val / (double) M;
}
// See the .cpp file.
size_t get_hum_bytes(size_t* hum_bytes);
void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
size_t* prev_live_bytes, size_t* next_live_bytes);
public:
// The header and footer are printed in the constructor and
// destructor respectively.
G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name);
virtual bool doHeapRegion(HeapRegion* r);
~G1PrintRegionLivenessInfoClosure();
};
#endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP