Mercurial > hg > truffle
diff src/share/vm/gc_implementation/g1/concurrentMark.hpp @ 342:37f87013dfd8
6711316: Open source the Garbage-First garbage collector
Summary: First mercurial integration of the code for the Garbage-First garbage collector.
Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr
author | ysr |
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date | Thu, 05 Jun 2008 15:57:56 -0700 |
parents | |
children | fe3d7c11b4b7 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/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_ +};