/* * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #ifndef SHARE_VM_GC_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 CMTaskQueue; typedef GenericTaskQueueSet 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(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.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 the CM collector. // Ideally this should be GrowableArray<> just like MSC's marking stack(s). class CMMarkStack VALUE_OBJ_CLASS_SPEC { 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 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 VALUE_OBJ_CLASS_SPEC { 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_lock_free(MemRegion mr); // Lock-free; assumes that it will only be called in parallel // with other "pop" operations (no pushes). MemRegion pop_lock_free(); #if 0 // The routines that manipulate the region stack with a lock are // not currently used. They should be retained, however, as a // diagnostic aid. // These two are the implementations that use a lock. They can be // called concurrently with each other but they should not be called // concurrently with the lock-free versions (push() / pop()). void push_with_lock(MemRegion mr); MemRegion pop_with_lock(); #endif 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(); } }; 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 ConcurrentMarkThread; class ConcurrentMark: public CHeapObj { 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; friend class G1RefProcTaskProxy; friend class G1RefProcTaskExecutor; friend class G1CMParKeepAliveAndDrainClosure; friend class G1CMParDrainMarkingStackClosure; 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; FreeRegionList _cleanup_list; // 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; // 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; 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(); // It resets all the marking data structures. void clear_marking_state(bool clear_overflow = true); // 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(); bool cleanup_list_is_empty() { return _cleanup_list.is_empty(); } // 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) { 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 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); 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(); } } 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(); } // (Lock-free) Manipulation of the region stack bool region_stack_push_lock_free(MemRegion mr) { // Currently we only call the lock-free version during evacuation // pauses. assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped"); _regionStack.push_lock_free(mr); if (_regionStack.overflow()) { set_has_overflown(); return false; } return true; } // Lock-free version of region-stack pop. Should only be // called in tandem with other lock-free pops. MemRegion region_stack_pop_lock_free() { return _regionStack.pop_lock_free(); } #if 0 // The routines that manipulate the region stack with a lock are // not currently used. They should be retained, however, as a // diagnostic aid. bool region_stack_push_with_lock(MemRegion mr) { // Currently we only call the lock-based version during either // concurrent marking or remark. assert(!SafepointSynchronize::is_at_safepoint() || !concurrent(), "if we are at a safepoint it should be the remark safepoint"); _regionStack.push_with_lock(mr); if (_regionStack.overflow()) { set_has_overflown(); return false; } return true; } MemRegion region_stack_pop_with_lock() { // Currently we only call the lock-based version during either // concurrent marking or remark. assert(!SafepointSynchronize::is_at_safepoint() || !concurrent(), "if we are at a safepoint it should be the remark safepoint"); return _regionStack.pop_with_lock(); } #endif int region_stack_size() { return _regionStack.size(); } bool region_stack_overflow() { return _regionStack.overflow(); } bool region_stack_empty() { return _regionStack.isEmpty(); } // Iterate over any regions that were aborted while draining the // region stack (any such regions are saved in the corresponding // CMTask) and invalidate (i.e. assign to the empty MemRegion()) // any regions that point into the collection set. bool invalidate_aborted_regions_in_cset(); // Returns true if there are any aborted memory regions. bool has_aborted_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 (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); // 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(); // 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); // Resets the region fields of any active CMTask whose region fields // are in the collection set (i.e. the region currently claimed by // the CMTask will be evacuated and may be used, subsequently, as // an alloc region). When this happens the region fields in the CMTask // are stale and, hence, should be cleared causing the worker thread // to claim a new region. void reset_active_task_region_fields_in_cset(); // Registers the maximum region-end associated with a set of // regions with CM. Again this is used to determine whether any // heap regions are located above the finger. void register_collection_set_finger(HeapWord* max_finger) { // max_finger is the highest heap region end of the regions currently // contained in the collection set. If this value is larger than // _min_finger then we need to gray objects. // This routine is like registerCSetRegion but for an entire // collection of regions. if (max_finger > _min_finger) { _should_gray_objects = true; } } // 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(); // 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; } }; // 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; 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; // 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; // If we abort while scanning a region we record the remaining // unscanned portion and check this field when marking restarts. // This avoids having to push on the region stack while other // marking threads may still be popping regions. // If we were to push the unscanned portion directly to the // region stack then we would need to using locking versions // of the push and pop operations. MemRegion _aborted_region; // 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; // 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(); // 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_stealing, bool do_termination); // 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(); // 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; } // Support routines for the partially scanned region that may be // recorded as a result of aborting while draining the CMRegionStack MemRegion aborted_region() { return _aborted_region; } void set_aborted_region(MemRegion mr) { _aborted_region = mr; } // Clears any recorded partially scanned region void clear_aborted_region() { set_aborted_region(MemRegion()); } 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(); // 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) { assert(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) { assert(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_ }; // 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