--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.hpp Thu Jun 05 15:57:56 2008 -0700
@@ -0,0 +1,1049 @@
+/*
+ * Copyright 2001-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+class G1CollectedHeap;
+class CMTask;
+typedef GenericTaskQueue<oop> CMTaskQueue;
+typedef GenericTaskQueueSet<oop> CMTaskQueueSet;
+
+// A generic CM bit map. This is essentially a wrapper around the BitMap
+// class, with one bit per (1<<_shifter) HeapWords.
+
+class CMBitMapRO {
+ 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(ReservedSpace rs, 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
+ bool iterate(BitMapClosure* cl) { return _bm.iterate(cl); }
+ bool iterate(BitMapClosure* cl, MemRegion mr);
+
+ // 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
+ // XXX Fix these so that offsets are size_t's...
+ 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;
+ HeapWord* nextWord(HeapWord* addr) {
+ return offsetToHeapWord(heapWordToOffset(addr) + 1);
+ }
+
+ void mostly_disjoint_range_union(BitMap* from_bitmap,
+ size_t from_start_index,
+ HeapWord* to_start_word,
+ size_t word_num);
+
+ // debugging
+ NOT_PRODUCT(bool covers(ReservedSpace rs) const;)
+};
+
+class CMBitMap : public CMBitMapRO {
+
+ public:
+ // constructor
+ CMBitMap(ReservedSpace rs, int shifter) :
+ CMBitMapRO(rs, shifter) {}
+
+ // write marks
+ void mark(HeapWord* addr) {
+ assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
+ "outside underlying space?");
+ _bm.at_put(heapWordToOffset(addr), true);
+ }
+ void clear(HeapWord* addr) {
+ assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
+ "outside underlying space?");
+ _bm.at_put(heapWordToOffset(addr), false);
+ }
+ bool parMark(HeapWord* addr) {
+ assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
+ "outside underlying space?");
+ return _bm.par_at_put(heapWordToOffset(addr), true);
+ }
+ bool parClear(HeapWord* addr) {
+ assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
+ "outside underlying space?");
+ return _bm.par_at_put(heapWordToOffset(addr), false);
+ }
+ 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 the CM collector.
+// Ideally this should be GrowableArray<> just like MSC's marking stack(s).
+class CMMarkStack {
+ ConcurrentMark* _cm;
+ oop* _base; // bottom of stack
+ jint _index; // one more than last occupied index
+ jint _capacity; // max #elements
+ jint _oops_do_bound; // Number of elements to include in next iteration.
+ NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run
+
+ bool _overflow;
+ DEBUG_ONLY(bool _drain_in_progress;)
+ DEBUG_ONLY(bool _drain_in_progress_yields;)
+
+ public:
+ CMMarkStack(ConcurrentMark* cm);
+ ~CMMarkStack();
+
+ void allocate(size_t size);
+
+ 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; }
+
+ int size() { return _index; }
+
+ void setEmpty() { _index = 0; clear_overflow(); }
+
+ // Record the current size; a subsequent "oops_do" will iterate only over
+ // indices valid at the time of this call.
+ void set_oops_do_bound(jint bound = -1) {
+ if (bound == -1) {
+ _oops_do_bound = _index;
+ } else {
+ _oops_do_bound = bound;
+ }
+ }
+ jint oops_do_bound() { return _oops_do_bound; }
+ // iterate over the oops in the mark stack, up to the bound recorded via
+ // the call above.
+ void oops_do(OopClosure* f);
+};
+
+class CMRegionStack {
+ MemRegion* _base;
+ jint _capacity;
+ jint _index;
+ jint _oops_do_bound;
+ bool _overflow;
+public:
+ CMRegionStack();
+ ~CMRegionStack();
+ void allocate(size_t size);
+
+ // This is lock-free; assumes that it will only be called in parallel
+ // with other "push" operations (no pops).
+ void push(MemRegion mr);
+
+ // Lock-free; assumes that it will only be called in parallel
+ // with other "pop" operations (no pushes).
+ MemRegion pop();
+
+ bool isEmpty() { return _index == 0; }
+ bool isFull() { return _index == _capacity; }
+
+ bool overflow() { return _overflow; }
+ void clear_overflow() { _overflow = false; }
+
+ int size() { return _index; }
+
+ // It iterates over the entries in the region stack and it
+ // invalidates (i.e. assigns MemRegion()) the ones that point to
+ // regions in the collection set.
+ bool invalidate_entries_into_cset();
+
+ // This gives an upper bound up to which the iteration in
+ // invalidate_entries_into_cset() will reach. This prevents
+ // newly-added entries to be unnecessarily scanned.
+ void set_oops_do_bound() {
+ _oops_do_bound = _index;
+ }
+
+ void setEmpty() { _index = 0; clear_overflow(); }
+};
+
+// 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_
+
+// Some extra guarantees that I like to also enable in optimised mode
+// when debugging. If you want to enable them, comment out the assert
+// macro and uncomment out the guaratee macro
+// #define tmp_guarantee_CM(expr, str) guarantee(expr, str)
+#define tmp_guarantee_CM(expr, str) assert(expr, str)
+
+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 ConcurrentMarkThread;
+
+class ConcurrentMark {
+ friend class ConcurrentMarkThread;
+ friend class CMTask;
+ friend class CMBitMapClosure;
+ friend class CSMarkOopClosure;
+ friend class CMGlobalObjectClosure;
+ friend class CMRemarkTask;
+ friend class CMConcurrentMarkingTask;
+ friend class G1ParNoteEndTask;
+ friend class CalcLiveObjectsClosure;
+
+protected:
+ ConcurrentMarkThread* _cmThread; // the thread doing the work
+ G1CollectedHeap* _g1h; // the heap.
+ size_t _parallel_marking_threads; // the number of marking
+ // threads we'll 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;
+
+ // Stuff related to age cohort processing.
+ struct ParCleanupThreadState {
+ char _pre[64];
+ UncleanRegionList list;
+ char _post[64];
+ };
+ ParCleanupThreadState** _par_cleanup_thread_state;
+
+ // CMS marking support structures
+ CMBitMap _markBitMap1;
+ CMBitMap _markBitMap2;
+ CMBitMapRO* _prevMarkBitMap; // completed mark bitmap
+ CMBitMap* _nextMarkBitMap; // under-construction mark bitmap
+ bool _at_least_one_mark_complete;
+
+ BitMap _region_bm;
+ BitMap _card_bm;
+
+ // Heap bounds
+ HeapWord* _heap_start;
+ HeapWord* _heap_end;
+
+ // For gray objects
+ CMMarkStack _markStack; // Grey objects behind global finger.
+ CMRegionStack _regionStack; // Grey regions behind global finger.
+ HeapWord* volatile _finger; // the global finger, region aligned,
+ // always points to the end of the
+ // last claimed region
+
+ // marking tasks
+ size_t _max_task_num; // maximum task number
+ size_t _active_tasks; // task num currently active
+ CMTask** _tasks; // task queue array (max_task_num 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;
+
+ COTracker _cleanup_co_tracker;
+
+ // These two fields are used to implement the optimisation that
+ // avoids pushing objects on the global/region stack if there are
+ // no collection set regions above the lowest finger.
+
+ // This is the lowest finger (among the global and local fingers),
+ // which is calculated before a new collection set is chosen.
+ HeapWord* _min_finger;
+ // If this flag is true, objects/regions that are marked below the
+ // finger should be pushed on the stack(s). If this is flag is
+ // false, it is safe not to push them on the stack(s).
+ bool _should_gray_objects;
+
+ // 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
+
+ WorkGang* _parallel_workers;
+
+ 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();
+ // It resets all the marking data structures.
+ void clear_marking_state();
+
+ // It should be called to indicate which phase we're in (concurrent
+ // mark or remark) and how many threads are currently active.
+ void set_phase(size_t active_tasks, bool concurrent);
+ // 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();
+
+ // prints all gathered CM-related statistics
+ void print_stats();
+
+ // accessor methods
+ size_t parallel_marking_threads() { return _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;}
+
+ HeapWord* finger() { return _finger; }
+ bool concurrent() { return _concurrent; }
+ size_t active_tasks() { return _active_tasks; }
+ ParallelTaskTerminator* terminator() { return &_terminator; }
+
+ // It claims the next available region to be scanned by a marking
+ // task. 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(int task);
+
+ // 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) {
+ guarantee( 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) {
+ guarantee( 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 or region stack has overflown
+ bool has_overflown() { return _has_overflown; }
+ void set_has_overflown() { _has_overflown = true; }
+ void clear_has_overflown() { _has_overflown = false; }
+
+ bool has_aborted() { return _has_aborted; }
+ bool restart_for_overflow() { return _restart_for_overflow; }
+
+ // Methods to enter the two overflow sync barriers
+ void enter_first_sync_barrier(int task_num);
+ void enter_second_sync_barrier(int task_num);
+
+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(); }
+
+ // Manipulation of the region stack
+ bool region_stack_push(MemRegion mr) {
+ _regionStack.push(mr);
+ if (_regionStack.overflow()) {
+ set_has_overflown();
+ return false;
+ }
+ return true;
+ }
+ MemRegion region_stack_pop() { return _regionStack.pop(); }
+ int region_stack_size() { return _regionStack.size(); }
+ bool region_stack_overflow() { return _regionStack.overflow(); }
+ bool region_stack_empty() { return _regionStack.isEmpty(); }
+
+ 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 (int i = 0; i < (int)_max_task_num; ++i)
+ ret += _accum_task_vtime[i];
+ return ret;
+ }
+
+ // Attempts to steal an object from the task queues of other tasks
+ bool try_stealing(int task_num, int* hash_seed, oop& obj) {
+ return _task_queues->steal(task_num, hash_seed, obj);
+ }
+
+ // It grays an object by first marking it. Then, if it's behind the
+ // global finger, it also pushes it on the global stack.
+ void deal_with_reference(oop obj);
+
+ ConcurrentMark(ReservedSpace rs, int max_regions);
+ ~ConcurrentMark();
+ ConcurrentMarkThread* cmThread() { return _cmThread; }
+
+ CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
+ CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
+
+ // The following three are interaction between CM and
+ // G1CollectedHeap
+
+ // This notifies CM that a root during initial-mark needs to be
+ // grayed and it's MT-safe. Currently, we just mark it. But, in the
+ // future, we can experiment with pushing it on the stack and we can
+ // do this without changing G1CollectedHeap.
+ void grayRoot(oop p);
+ // It's used during evacuation pauses to gray a region, if
+ // necessary, and it's MT-safe. It assumes that the caller has
+ // marked any objects on that region. If _should_gray_objects is
+ // true and we're still doing concurrent marking, the region is
+ // pushed on the region stack, if it is located below the global
+ // finger, otherwise we do nothing.
+ void grayRegionIfNecessary(MemRegion mr);
+ // It's used during evacuation pauses to mark and, if necessary,
+ // gray a single object and it's MT-safe. It assumes the caller did
+ // not mark the object. If _should_gray_objects is true and we're
+ // still doing concurrent marking, the objects is pushed on the
+ // global stack, if it is located below the global finger, otherwise
+ // we do nothing.
+ void markAndGrayObjectIfNecessary(oop p);
+
+ // This iterates over the bitmap of the previous marking and prints
+ // out all objects that are marked on the bitmap and indicates
+ // whether what they point to is also marked or not.
+ void print_prev_bitmap_reachable();
+
+ // Clear the next marking bitmap (will be called concurrently).
+ void clearNextBitmap();
+
+ // main CMS steps and related support
+ void checkpointRootsInitial();
+
+ // 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();
+
+ // Do concurrent phase of marking, to a tentative transitive closure.
+ void markFromRoots();
+
+ // Process all unprocessed SATB buffers. It is called at the
+ // beginning of an evacuation pause.
+ void drainAllSATBBuffers();
+
+ void checkpointRootsFinal(bool clear_all_soft_refs);
+ void checkpointRootsFinalWork();
+ void calcDesiredRegions();
+ void cleanup();
+ void completeCleanup();
+
+ // Mark in the previous bitmap. NB: this is usually read-only, so use
+ // this carefully!
+ void markPrev(oop p);
+ void clear(oop p);
+ // Clears marks for all objects in the given range, for both prev and
+ // next bitmaps. NB: the previous bitmap is usually read-only, so use
+ // this carefully!
+ void clearRangeBothMaps(MemRegion mr);
+
+ // Record the current top of the mark and region stacks; a
+ // subsequent oops_do() on the mark stack and
+ // invalidate_entries_into_cset() on the region stack will iterate
+ // only over indices valid at the time of this call.
+ void set_oops_do_bound() {
+ _markStack.set_oops_do_bound();
+ _regionStack.set_oops_do_bound();
+ }
+ // Iterate over the oops in the mark stack and all local queues. It
+ // also calls invalidate_entries_into_cset() on the region stack.
+ void oops_do(OopClosure* f);
+ // 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);
+
+ void complete_marking_in_collection_set();
+
+ // It indicates that a new collection set is being chosen.
+ void newCSet();
+ // It registers a collection set heap region with CM. This is used
+ // to determine whether any heap regions are located above the finger.
+ void registerCSetRegion(HeapRegion* hr);
+
+ // Returns "true" if at least one mark has been completed.
+ bool at_least_one_mark_complete() { return _at_least_one_mark_complete; }
+
+ 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(int worker_i = 0);
+ inline bool should_yield();
+
+ // Called to abort the marking cycle after a Full GC takes palce.
+ void abort();
+
+ void disable_co_trackers();
+
+ // This prints the global/local fingers. It is used for debugging.
+ NOT_PRODUCT(void print_finger();)
+
+ void print_summary_info();
+
+ // 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; }
+};
+
+// 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
+ };
+
+ int _task_id;
+ G1CollectedHeap* _g1h;
+ ConcurrentMark* _cm;
+ CMBitMap* _nextMarkBitMap;
+ // the task queue of this task
+ CMTaskQueue* _task_queue;
+ // 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;
+
+ // concurrent overhead over a single CPU for this task
+ COTracker _co_tracker;
+
+ // 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
+ OopClosure* _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;
+
+ // This is used only when we scan regions popped from the region
+ // stack. It records what the last object on such a region we
+ // scanned was. It is used to ensure that, if we abort region
+ // iteration, we do not rescan the first part of the region. This
+ // should be NULL when we're not scanning a region from the region
+ // stack.
+ HeapWord* _region_finger;
+
+ // 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_aborted_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;
+
+ // 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 _region_stack_pops;
+
+ 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();
+ // it resets the local fields after a task has finished scanning a
+ // region
+ void giveup_current_region();
+
+ // 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; }
+
+ void enable_co_tracker() {
+ guarantee( !_co_tracker.enabled(), "invariant" );
+ _co_tracker.enable();
+ }
+ void disable_co_tracker() {
+ guarantee( _co_tracker.enabled(), "invariant" );
+ _co_tracker.disable();
+ }
+ bool co_tracker_enabled() {
+ return _co_tracker.enabled();
+ }
+ void reset_co_tracker(double starting_conc_overhead = 0.0) {
+ _co_tracker.reset(starting_conc_overhead);
+ }
+ void start_co_tracker() {
+ _co_tracker.start();
+ }
+ void update_co_tracker(bool force_end = false) {
+ _co_tracker.update(force_end);
+ }
+
+ // 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);
+
+ // 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 task ID
+ int task_id() { return _task_id; }
+
+ // From TerminatorTerminator. It determines whether this task should
+ // exit the termination protocol after it's entered it.
+ virtual bool should_exit_termination();
+
+ 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 claimed() { return _claimed; }
+
+ void set_oop_closure(OopClosure* oop_closure) {
+ _oop_closure = oop_closure;
+ }
+
+ // It grays the object by marking it and, if necessary, pushing it
+ // on the local queue
+ void deal_with_reference(oop obj);
+
+ // It scans an object and visits its children.
+ void scan_object(oop obj) {
+ tmp_guarantee_CM( _nextMarkBitMap->isMarked((HeapWord*) obj),
+ "invariant" );
+
+ if (_cm->verbose_high())
+ gclog_or_tty->print_cr("[%d] we're scanning object "PTR_FORMAT,
+ _task_id, (void*) obj);
+
+ size_t obj_size = obj->size();
+ _words_scanned += obj_size;
+
+ obj->oop_iterate(_oop_closure);
+ statsOnly( ++_objs_scanned );
+ check_limits();
+ }
+
+ // It pushes an object on the local queue.
+ 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();
+ // It keeps popping regions from the region stack and processing
+ // them until the region stack is empty.
+ void drain_region_stack(BitMapClosure* closure);
+
+ // moves the local finger to a new location
+ inline void move_finger_to(HeapWord* new_finger) {
+ tmp_guarantee_CM( new_finger >= _finger && new_finger < _region_limit,
+ "invariant" );
+ _finger = new_finger;
+ }
+
+ // moves the region finger to a new location
+ inline void move_region_finger_to(HeapWord* new_finger) {
+ tmp_guarantee_CM( new_finger < _cm->finger(), "invariant" );
+ _region_finger = new_finger;
+ }
+
+ CMTask(int task_num, ConcurrentMark *cm,
+ 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_
+};