/* * Copyright (c) 2001, 2013, 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 "classfile/javaClasses.hpp" #include "gc_implementation/g1/heapRegionSet.hpp" #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp" #include "gc_implementation/shared/gcId.hpp" #include "utilities/taskqueue.hpp" class G1CollectedHeap; class CMBitMap; 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) { } 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 BitMap _bm; // the bit map itself public: // constructor CMBitMapRO(int shifter); enum { do_yield = true }; // inquiries HeapWord* startWord() const { return _bmStartWord; } size_t sizeInWords() const { return _bmWordSize; } // the following is one past the last word in space HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } // read marks bool isMarked(HeapWord* addr) const { assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), "outside underlying space?"); return _bm.at(heapWordToOffset(addr)); } // iteration inline bool iterate(BitMapClosure* cl, MemRegion mr); inline bool iterate(BitMapClosure* cl); // Return the address corresponding to the next marked bit at or after // "addr", and before "limit", if "limit" is non-NULL. If there is no // such bit, returns "limit" if that is non-NULL, or else "endWord()". HeapWord* getNextMarkedWordAddress(const HeapWord* addr, const 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(const HeapWord* addr, const HeapWord* limit = NULL) const; // conversion utilities HeapWord* offsetToHeapWord(size_t offset) const { return _bmStartWord + (offset << _shifter); } size_t heapWordToOffset(const HeapWord* addr) const { return pointer_delta(addr, _bmStartWord) >> _shifter; } int heapWordDiffToOffsetDiff(size_t diff) const; // The argument addr should be the start address of a valid object HeapWord* nextObject(HeapWord* addr) { oop obj = (oop) addr; HeapWord* res = addr + obj->size(); assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity"); return res; } void print_on_error(outputStream* st, const char* prefix) const; // debugging NOT_PRODUCT(bool covers(MemRegion rs) const;) }; class CMBitMapMappingChangedListener : public G1MappingChangedListener { private: CMBitMap* _bm; public: CMBitMapMappingChangedListener() : _bm(NULL) {} void set_bitmap(CMBitMap* bm) { _bm = bm; } virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); }; class CMBitMap : public CMBitMapRO { private: CMBitMapMappingChangedListener _listener; public: static size_t compute_size(size_t heap_size); // Returns the amount of bytes on the heap between two marks in the bitmap. static size_t mark_distance(); CMBitMap() : CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); } // Initializes the underlying BitMap to cover the given area. void initialize(MemRegion heap, G1RegionToSpaceMapper* storage); // Write marks. inline void mark(HeapWord* addr); inline void clear(HeapWord* addr); inline bool parMark(HeapWord* addr); inline bool parClear(HeapWord* addr); void markRange(MemRegion mr); 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); // Clear the whole mark bitmap. void clearAll(); }; // Represents a marking stack used by ConcurrentMarking in the G1 collector. class CMMarkStack VALUE_OBJ_CLASS_SPEC { VirtualSpace _virtual_space; // Underlying backing store for actual stack ConcurrentMark* _cm; oop* _base; // bottom of stack jint _index; // one more than last occupied index jint _capacity; // max #elements jint _saved_index; // value of _index saved at start of GC NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run bool _overflow; bool _should_expand; DEBUG_ONLY(bool _drain_in_progress;) DEBUG_ONLY(bool _drain_in_progress_yields;) public: CMMarkStack(ConcurrentMark* cm); ~CMMarkStack(); #ifndef PRODUCT jint max_depth() const { return _max_depth; } #endif bool allocate(size_t capacity); oop pop() { if (!isEmpty()) { return _base[--_index] ; } return NULL; } // If overflow happens, don't do the push, and record the overflow. // *Requires* that "ptr" is already marked. void push(oop ptr) { if (isFull()) { // Record overflow. _overflow = true; return; } else { _base[_index++] = ptr; NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); } } // Non-block impl. Note: concurrency is allowed only with other // "par_push" operations, not with "pop" or "drain". We would need // parallel versions of them if such concurrency was desired. void par_push(oop ptr); // Pushes the first "n" elements of "ptr_arr" on the stack. // Non-block impl. Note: concurrency is allowed only with other // "par_adjoin_arr" or "push" operations, not with "pop" or "drain". void par_adjoin_arr(oop* ptr_arr, int n); // Pushes the first "n" elements of "ptr_arr" on the stack. // Locking impl: concurrency is allowed only with // "par_push_arr" and/or "par_pop_arr" operations, which use the same // locking strategy. void par_push_arr(oop* ptr_arr, int n); // If returns false, the array was empty. Otherwise, removes up to "max" // elements from the stack, and transfers them to "ptr_arr" in an // unspecified order. The actual number transferred is given in "n" ("n // == 0" is deliberately redundant with the return value.) Locking impl: // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr" // operations, which use the same locking strategy. bool par_pop_arr(oop* ptr_arr, int max, int* n); // Drain the mark stack, applying the given closure to all fields of // objects on the stack. (That is, continue until the stack is empty, // even if closure applications add entries to the stack.) The "bm" // argument, if non-null, may be used to verify that only marked objects // are on the mark stack. If "yield_after" is "true", then the // concurrent marker performing the drain offers to yield after // processing each object. If a yield occurs, stops the drain operation // and returns false. Otherwise, returns true. template bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false); bool isEmpty() { return _index == 0; } bool isFull() { return _index == _capacity; } int maxElems() { return _capacity; } bool overflow() { return _overflow; } void clear_overflow() { _overflow = false; } bool should_expand() const { return _should_expand; } void set_should_expand(); // Expand the stack, typically in response to an overflow condition void expand(); int size() { return _index; } void setEmpty() { _index = 0; clear_overflow(); } // Record the current index. void note_start_of_gc(); // Make sure that we have not added any entries to the stack during GC. void note_end_of_gc(); // iterate over the oops in the mark stack, up to the bound recorded via // the call above. void oops_do(OopClosure* f); }; class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC { private: #ifndef PRODUCT uintx _num_remaining; bool _force; #endif // !defined(PRODUCT) public: void init() PRODUCT_RETURN; void update() PRODUCT_RETURN; bool should_force() PRODUCT_RETURN_( return false; ); }; // this will enable a variety of different statistics per GC task #define _MARKING_STATS_ 0 // this will enable the higher verbose levels #define _MARKING_VERBOSE_ 0 #if _MARKING_STATS_ #define statsOnly(statement) \ do { \ statement ; \ } while (0) #else // _MARKING_STATS_ #define statsOnly(statement) \ do { \ } while (0) #endif // _MARKING_STATS_ typedef enum { no_verbose = 0, // verbose turned off stats_verbose, // only prints stats at the end of marking low_verbose, // low verbose, mostly per region and per major event medium_verbose, // a bit more detailed than low high_verbose // per object verbose } CMVerboseLevel; class YoungList; // Root Regions are regions that are not empty at the beginning of a // marking cycle and which we might collect during an evacuation pause // while the cycle is active. Given that, during evacuation pauses, we // do not copy objects that are explicitly marked, what we have to do // for the root regions is to scan them and mark all objects reachable // from them. According to the SATB assumptions, we only need to visit // each object once during marking. So, as long as we finish this scan // before the next evacuation pause, we can copy the objects from the // root regions without having to mark them or do anything else to them. // // Currently, we only support root region scanning once (at the start // of the marking cycle) and the root regions are all the survivor // regions populated during the initial-mark pause. class CMRootRegions VALUE_OBJ_CLASS_SPEC { private: YoungList* _young_list; ConcurrentMark* _cm; volatile bool _scan_in_progress; volatile bool _should_abort; HeapRegion* volatile _next_survivor; public: CMRootRegions(); // We actually do most of the initialization in this method. void init(G1CollectedHeap* g1h, ConcurrentMark* cm); // Reset the claiming / scanning of the root regions. void prepare_for_scan(); // Forces get_next() to return NULL so that the iteration aborts early. void abort() { _should_abort = true; } // Return true if the CM thread are actively scanning root regions, // false otherwise. bool scan_in_progress() { return _scan_in_progress; } // Claim the next root region to scan atomically, or return NULL if // all have been claimed. HeapRegion* claim_next(); // Flag that we're done with root region scanning and notify anyone // who's waiting on it. If aborted is false, assume that all regions // have been claimed. void scan_finished(); // If CM threads are still scanning root regions, wait until they // are done. Return true if we had to wait, false otherwise. bool wait_until_scan_finished(); }; class ConcurrentMarkThread; class ConcurrentMark: public CHeapObj { friend class CMMarkStack; friend class ConcurrentMarkThread; friend class CMTask; friend class CMBitMapClosure; friend class CMGlobalObjectClosure; friend class CMRemarkTask; friend class CMConcurrentMarkingTask; friend class G1ParNoteEndTask; friend class CalcLiveObjectsClosure; friend class G1CMRefProcTaskProxy; friend class G1CMRefProcTaskExecutor; friend class G1CMKeepAliveAndDrainClosure; friend class G1CMDrainMarkingStackClosure; protected: ConcurrentMarkThread* _cmThread; // the thread doing the work G1CollectedHeap* _g1h; // the heap. uint _parallel_marking_threads; // the number of marking // threads we're use uint _max_parallel_marking_threads; // max number of marking // threads we'll ever use double _sleep_factor; // how much we have to sleep, with // respect to the work we just did, to // meet the marking overhead goal double _marking_task_overhead; // marking target overhead for // a single task // same as the two above, but for the cleanup task double _cleanup_sleep_factor; double _cleanup_task_overhead; FreeRegionList _cleanup_list; // Concurrent marking support structures CMBitMap _markBitMap1; CMBitMap _markBitMap2; CMBitMapRO* _prevMarkBitMap; // completed mark bitmap CMBitMap* _nextMarkBitMap; // under-construction mark bitmap BitMap _region_bm; BitMap _card_bm; // Heap bounds HeapWord* _heap_start; HeapWord* _heap_end; // Root region tracking and claiming. CMRootRegions _root_regions; // For gray objects CMMarkStack _markStack; // Grey objects behind global finger. HeapWord* volatile _finger; // the global finger, region aligned, // always points to the end of the // last claimed region // marking tasks uint _max_worker_id;// maximum worker id uint _active_tasks; // task num currently active CMTask** _tasks; // task queue array (max_worker_id len) CMTaskQueueSet* _task_queues; // task queue set ParallelTaskTerminator _terminator; // for termination // Two sync barriers that are used to synchronise tasks when an // overflow occurs. The algorithm is the following. All tasks enter // the first one to ensure that they have all stopped manipulating // the global data structures. After they exit it, they re-initialise // their data structures and task 0 re-initialises the global data // structures. Then, they enter the second sync barrier. This // ensure, that no task starts doing work before all data // structures (local and global) have been re-initialised. When they // exit it, they are free to start working again. WorkGangBarrierSync _first_overflow_barrier_sync; WorkGangBarrierSync _second_overflow_barrier_sync; // this is set by any task, when an overflow on the global data // structures is detected. volatile bool _has_overflown; // true: marking is concurrent, false: we're in remark volatile bool _concurrent; // set at the end of a Full GC so that marking aborts volatile bool _has_aborted; GCId _aborted_gc_id; // used when remark aborts due to an overflow to indicate that // another concurrent marking phase should start volatile bool _restart_for_overflow; // This is true from the very start of concurrent marking until the // point when all the tasks complete their work. It is really used // to determine the points between the end of concurrent marking and // time of remark. volatile bool _concurrent_marking_in_progress; // verbose level CMVerboseLevel _verbose_level; // All of these times are in ms. NumberSeq _init_times; NumberSeq _remark_times; NumberSeq _remark_mark_times; NumberSeq _remark_weak_ref_times; NumberSeq _cleanup_times; double _total_counting_time; double _total_rs_scrub_time; double* _accum_task_vtime; // accumulated task vtime FlexibleWorkGang* _parallel_workers; ForceOverflowSettings _force_overflow_conc; ForceOverflowSettings _force_overflow_stw; void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes); void weakRefsWork(bool clear_all_soft_refs); void swapMarkBitMaps(); // It resets the global marking data structures, as well as the // task local ones; should be called during initial mark. void reset(); // Resets all the marking data structures. Called when we have to restart // marking or when marking completes (via set_non_marking_state below). void reset_marking_state(bool clear_overflow = true); // We do this after we're done with marking so that the marking data // structures are initialised to a sensible and predictable state. void set_non_marking_state(); // Called to indicate how many threads are currently active. void set_concurrency(uint active_tasks); // It should be called to indicate which phase we're in (concurrent // mark or remark) and how many threads are currently active. void set_concurrency_and_phase(uint active_tasks, bool concurrent); // prints all gathered CM-related statistics void print_stats(); bool cleanup_list_is_empty() { return _cleanup_list.is_empty(); } // accessor methods uint parallel_marking_threads() const { return _parallel_marking_threads; } uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;} double sleep_factor() { return _sleep_factor; } double marking_task_overhead() { return _marking_task_overhead;} double cleanup_sleep_factor() { return _cleanup_sleep_factor; } double cleanup_task_overhead() { return _cleanup_task_overhead;} bool use_parallel_marking_threads() const { assert(parallel_marking_threads() <= max_parallel_marking_threads(), "sanity"); assert((_parallel_workers == NULL && parallel_marking_threads() == 0) || parallel_marking_threads() > 0, "parallel workers not set up correctly"); return _parallel_workers != NULL; } HeapWord* finger() { return _finger; } bool concurrent() { return _concurrent; } uint active_tasks() { return _active_tasks; } ParallelTaskTerminator* terminator() { return &_terminator; } // It claims the next available region to be scanned by a marking // task/thread. It might return NULL if the next region is empty or // we have run out of regions. In the latter case, out_of_regions() // determines whether we've really run out of regions or the task // should call claim_region() again. This might seem a bit // awkward. Originally, the code was written so that claim_region() // either successfully returned with a non-empty region or there // were no more regions to be claimed. The problem with this was // that, in certain circumstances, it iterated over large chunks of // the heap finding only empty regions and, while it was working, it // was preventing the calling task to call its regular clock // method. So, this way, each task will spend very little time in // claim_region() and is allowed to call the regular clock method // frequently. HeapRegion* claim_region(uint worker_id); // It determines whether we've run out of regions to scan. Note that // the finger can point past the heap end in case the heap was expanded // to satisfy an allocation without doing a GC. This is fine, because all // objects in those regions will be considered live anyway because of // SATB guarantees (i.e. their TAMS will be equal to bottom). bool out_of_regions() { return _finger >= _heap_end; } // Returns the task with the given id CMTask* task(int id) { assert(0 <= id && id < (int) _active_tasks, "task id not within active bounds"); return _tasks[id]; } // Returns the task queue with the given id CMTaskQueue* task_queue(int id) { assert(0 <= id && id < (int) _active_tasks, "task queue id not within active bounds"); return (CMTaskQueue*) _task_queues->queue(id); } // Returns the task queue set CMTaskQueueSet* task_queues() { return _task_queues; } // Access / manipulation of the overflow flag which is set to // indicate that the global stack has overflown bool has_overflown() { return _has_overflown; } void set_has_overflown() { _has_overflown = true; } void clear_has_overflown() { _has_overflown = false; } bool restart_for_overflow() { return _restart_for_overflow; } // Methods to enter the two overflow sync barriers void enter_first_sync_barrier(uint worker_id); void enter_second_sync_barrier(uint worker_id); ForceOverflowSettings* force_overflow_conc() { return &_force_overflow_conc; } ForceOverflowSettings* force_overflow_stw() { return &_force_overflow_stw; } ForceOverflowSettings* force_overflow() { if (concurrent()) { return force_overflow_conc(); } else { return force_overflow_stw(); } } // Live Data Counting data structures... // These data structures are initialized at the start of // marking. They are written to while marking is active. // They are aggregated during remark; the aggregated values // are then used to populate the _region_bm, _card_bm, and // the total live bytes, which are then subsequently updated // during cleanup. // An array of bitmaps (one bit map per task). Each bitmap // is used to record the cards spanned by the live objects // marked by that task/worker. BitMap* _count_card_bitmaps; // Used to record the number of marked live bytes // (for each region, by worker thread). size_t** _count_marked_bytes; // Card index of the bottom of the G1 heap. Used for biasing indices into // the card bitmaps. intptr_t _heap_bottom_card_num; // Set to true when initialization is complete bool _completed_initialization; public: // Manipulation of the global mark stack. // Notice that the first mark_stack_push is CAS-based, whereas the // two below are Mutex-based. This is OK since the first one is only // called during evacuation pauses and doesn't compete with the // other two (which are called by the marking tasks during // concurrent marking or remark). bool mark_stack_push(oop p) { _markStack.par_push(p); if (_markStack.overflow()) { set_has_overflown(); return false; } return true; } bool mark_stack_push(oop* arr, int n) { _markStack.par_push_arr(arr, n); if (_markStack.overflow()) { set_has_overflown(); return false; } return true; } void mark_stack_pop(oop* arr, int max, int* n) { _markStack.par_pop_arr(arr, max, n); } size_t mark_stack_size() { return _markStack.size(); } size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; } bool mark_stack_overflow() { return _markStack.overflow(); } bool mark_stack_empty() { return _markStack.isEmpty(); } CMRootRegions* root_regions() { return &_root_regions; } bool concurrent_marking_in_progress() { return _concurrent_marking_in_progress; } void set_concurrent_marking_in_progress() { _concurrent_marking_in_progress = true; } void clear_concurrent_marking_in_progress() { _concurrent_marking_in_progress = false; } void update_accum_task_vtime(int i, double vtime) { _accum_task_vtime[i] += vtime; } double all_task_accum_vtime() { double ret = 0.0; for (uint i = 0; i < _max_worker_id; ++i) ret += _accum_task_vtime[i]; return ret; } // Attempts to steal an object from the task queues of other tasks bool try_stealing(uint worker_id, int* hash_seed, oop& obj) { return _task_queues->steal(worker_id, hash_seed, obj); } ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage); ~ConcurrentMark(); ConcurrentMarkThread* cmThread() { return _cmThread; } CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; } CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; } // Returns the number of GC threads to be used in a concurrent // phase based on the number of GC threads being used in a STW // phase. uint scale_parallel_threads(uint n_par_threads); // Calculates the number of GC threads to be used in a concurrent phase. uint calc_parallel_marking_threads(); // The following three are interaction between CM and // G1CollectedHeap // This notifies CM that a root during initial-mark needs to be // grayed. It is MT-safe. word_size is the size of the object in // words. It is passed explicitly as sometimes we cannot calculate // it from the given object because it might be in an inconsistent // state (e.g., in to-space and being copied). So the caller is // responsible for dealing with this issue (e.g., get the size from // the from-space image when the to-space image might be // inconsistent) and always passing the size. hr is the region that // contains the object and it's passed optionally from callers who // might already have it (no point in recalculating it). inline void grayRoot(oop obj, size_t word_size, uint worker_id, HeapRegion* hr = NULL); // It iterates over the heap and for each object it comes across it // will dump the contents of its reference fields, as well as // liveness information for the object and its referents. The dump // will be written to a file with the following name: // G1PrintReachableBaseFile + "." + str. // vo decides whether the prev (vo == UsePrevMarking), the next // (vo == UseNextMarking) marking information, or the mark word // (vo == UseMarkWord) will be used to determine the liveness of // each object / referent. // If all is true, all objects in the heap will be dumped, otherwise // only the live ones. In the dump the following symbols / breviations // are used: // M : an explicitly live object (its bitmap bit is set) // > : an implicitly live object (over tams) // O : an object outside the G1 heap (typically: in the perm gen) // NOT : a reference field whose referent is not live // AND MARKED : indicates that an object is both explicitly and // implicitly live (it should be one or the other, not both) void print_reachable(const char* str, VerifyOption vo, bool all) PRODUCT_RETURN; // Clear the next marking bitmap (will be called concurrently). void clearNextBitmap(); // Return whether the next mark bitmap has no marks set. To be used for assertions // only. Will not yield to pause requests. bool nextMarkBitmapIsClear(); // These two do the work that needs to be done before and after the // initial root checkpoint. Since this checkpoint can be done at two // different points (i.e. an explicit pause or piggy-backed on a // young collection), then it's nice to be able to easily share the // pre/post code. It might be the case that we can put everything in // the post method. TP void checkpointRootsInitialPre(); void checkpointRootsInitialPost(); // Scan all the root regions and mark everything reachable from // them. void scanRootRegions(); // Scan a single root region and mark everything reachable from it. void scanRootRegion(HeapRegion* hr, uint worker_id); // Do concurrent phase of marking, to a tentative transitive closure. void markFromRoots(); void checkpointRootsFinal(bool clear_all_soft_refs); void checkpointRootsFinalWork(); void cleanup(); void completeCleanup(); // Mark in the previous bitmap. NB: this is usually read-only, so use // this carefully! inline void markPrev(oop p); // Clears marks for all objects in the given range, for the prev or // next bitmaps. NB: the previous bitmap is usually // read-only, so use this carefully! void clearRangePrevBitmap(MemRegion mr); void clearRangeNextBitmap(MemRegion mr); // Notify data structures that a GC has started. void note_start_of_gc() { _markStack.note_start_of_gc(); } // Notify data structures that a GC is finished. void note_end_of_gc() { _markStack.note_end_of_gc(); } // Verify that there are no CSet oops on the stacks (taskqueues / // global mark stack), enqueued SATB buffers, per-thread SATB // buffers, and fingers (global / per-task). The boolean parameters // decide which of the above data structures to verify. If marking // is not in progress, it's a no-op. void verify_no_cset_oops(bool verify_stacks, bool verify_enqueued_buffers, bool verify_thread_buffers, bool verify_fingers) PRODUCT_RETURN; bool isPrevMarked(oop p) const { assert(p != NULL && p->is_oop(), "expected an oop"); HeapWord* addr = (HeapWord*)p; assert(addr >= _prevMarkBitMap->startWord() || addr < _prevMarkBitMap->endWord(), "in a region"); return _prevMarkBitMap->isMarked(addr); } inline bool do_yield_check(uint worker_i = 0); // Called to abort the marking cycle after a Full GC takes palce. void abort(); bool has_aborted() { return _has_aborted; } const GCId& concurrent_gc_id(); // 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; void print_on_error(outputStream* st) const; // The following indicate whether a given verbose level has been // set. Notice that anything above stats is conditional to // _MARKING_VERBOSE_ having been set to 1 bool verbose_stats() { return _verbose_level >= stats_verbose; } bool verbose_low() { return _MARKING_VERBOSE_ && _verbose_level >= low_verbose; } bool verbose_medium() { return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose; } bool verbose_high() { return _MARKING_VERBOSE_ && _verbose_level >= high_verbose; } // Liveness counting // Utility routine to set an exclusive range of cards on the given // card liveness bitmap inline void set_card_bitmap_range(BitMap* card_bm, BitMap::idx_t start_idx, BitMap::idx_t end_idx, bool is_par); // Returns the card number of the bottom of the G1 heap. // Used in biasing indices into accounting card bitmaps. intptr_t heap_bottom_card_num() const { return _heap_bottom_card_num; } // Returns the card bitmap for a given task or worker id. BitMap* count_card_bitmap_for(uint worker_id) { assert(0 <= worker_id && worker_id < _max_worker_id, "oob"); assert(_count_card_bitmaps != NULL, "uninitialized"); BitMap* task_card_bm = &_count_card_bitmaps[worker_id]; assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); return task_card_bm; } // Returns the array containing the marked bytes for each region, // for the given worker or task id. size_t* count_marked_bytes_array_for(uint worker_id) { assert(0 <= worker_id && worker_id < _max_worker_id, "oob"); assert(_count_marked_bytes != NULL, "uninitialized"); size_t* marked_bytes_array = _count_marked_bytes[worker_id]; assert(marked_bytes_array != NULL, "uninitialized"); return marked_bytes_array; } // Returns the index in the liveness accounting card table bitmap // for the given address inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr); // Counts the size of the given memory region in the the given // marked_bytes array slot for the given HeapRegion. // Sets the bits in the given card bitmap that are associated with the // cards that are spanned by the memory region. inline void count_region(MemRegion mr, HeapRegion* hr, size_t* marked_bytes_array, BitMap* task_card_bm); // Counts the given memory region in the task/worker counting // data structures for the given worker id. inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id); // Counts the given object in the given task/worker counting // data structures. inline void count_object(oop obj, HeapRegion* hr, size_t* marked_bytes_array, BitMap* task_card_bm); // Attempts to mark the given object and, if successful, counts // the object in the given task/worker counting structures. inline bool par_mark_and_count(oop obj, HeapRegion* hr, size_t* marked_bytes_array, BitMap* task_card_bm); // Attempts to mark the given object and, if successful, counts // the object in the task/worker counting structures for the // given worker id. inline bool par_mark_and_count(oop obj, size_t word_size, HeapRegion* hr, uint worker_id); // Returns true if initialization was successfully completed. bool completed_initialization() const { return _completed_initialization; } protected: // Clear all the per-task bitmaps and arrays used to store the // counting data. void clear_all_count_data(); // Aggregates the counting data for each worker/task // that was constructed while marking. Also sets // the amount of marked bytes for each region and // the top at concurrent mark count. void aggregate_count_data(); // Verification routine void verify_count_data(); }; // A class representing a marking task. class CMTask : public TerminatorTerminator { private: enum PrivateConstants { // the regular clock call is called once the scanned words reaches // this limit words_scanned_period = 12*1024, // the regular clock call is called once the number of visited // references reaches this limit refs_reached_period = 384, // initial value for the hash seed, used in the work stealing code init_hash_seed = 17, // how many entries will be transferred between global stack and // local queues global_stack_transfer_size = 16 }; uint _worker_id; G1CollectedHeap* _g1h; ConcurrentMark* _cm; CMBitMap* _nextMarkBitMap; // the task queue of this task CMTaskQueue* _task_queue; private: // the task queue set---needed for stealing CMTaskQueueSet* _task_queues; // indicates whether the task has been claimed---this is only for // debugging purposes bool _claimed; // number of calls to this task int _calls; // when the virtual timer reaches this time, the marking step should // exit double _time_target_ms; // the start time of the current marking step double _start_time_ms; // the oop closure used for iterations over oops G1CMOopClosure* _cm_oop_closure; // the region this task is scanning, NULL if we're not scanning any HeapRegion* _curr_region; // the local finger of this task, NULL if we're not scanning a region HeapWord* _finger; // limit of the region this task is scanning, NULL if we're not scanning one HeapWord* _region_limit; // the number of words this task has scanned size_t _words_scanned; // When _words_scanned reaches this limit, the regular clock is // called. Notice that this might be decreased under certain // circumstances (i.e. when we believe that we did an expensive // operation). size_t _words_scanned_limit; // the initial value of _words_scanned_limit (i.e. what it was // before it was decreased). size_t _real_words_scanned_limit; // the number of references this task has visited size_t _refs_reached; // When _refs_reached reaches this limit, the regular clock is // called. Notice this this might be decreased under certain // circumstances (i.e. when we believe that we did an expensive // operation). size_t _refs_reached_limit; // the initial value of _refs_reached_limit (i.e. what it was before // it was decreased). size_t _real_refs_reached_limit; // used by the work stealing stuff int _hash_seed; // if this is true, then the task has aborted for some reason bool _has_aborted; // set when the task aborts because it has met its time quota bool _has_timed_out; // true when we're draining SATB buffers; this avoids the task // aborting due to SATB buffers being available (as we're already // dealing with them) bool _draining_satb_buffers; // number sequence of past step times NumberSeq _step_times_ms; // elapsed time of this task double _elapsed_time_ms; // termination time of this task double _termination_time_ms; // when this task got into the termination protocol double _termination_start_time_ms; // true when the task is during a concurrent phase, false when it is // in the remark phase (so, in the latter case, we do not have to // check all the things that we have to check during the concurrent // phase, i.e. SATB buffer availability...) bool _concurrent; TruncatedSeq _marking_step_diffs_ms; // Counting data structures. Embedding the task's marked_bytes_array // and card bitmap into the actual task saves having to go through // the ConcurrentMark object. size_t* _marked_bytes_array; BitMap* _card_bm; // LOTS of statistics related with this task #if _MARKING_STATS_ NumberSeq _all_clock_intervals_ms; double _interval_start_time_ms; int _aborted; int _aborted_overflow; int _aborted_cm_aborted; int _aborted_yield; int _aborted_timed_out; int _aborted_satb; int _aborted_termination; int _steal_attempts; int _steals; int _clock_due_to_marking; int _clock_due_to_scanning; int _local_pushes; int _local_pops; int _local_max_size; int _objs_scanned; int _global_pushes; int _global_pops; int _global_max_size; int _global_transfers_to; int _global_transfers_from; int _regions_claimed; int _objs_found_on_bitmap; int _satb_buffers_processed; #endif // _MARKING_STATS_ // it updates the local fields after this task has claimed // a new region to scan void setup_for_region(HeapRegion* hr); // it brings up-to-date the limit of the region void update_region_limit(); // called when either the words scanned or the refs visited limit // has been reached void reached_limit(); // recalculates the words scanned and refs visited limits void recalculate_limits(); // decreases the words scanned and refs visited limits when we reach // an expensive operation void decrease_limits(); // it checks whether the words scanned or refs visited reached their // respective limit and calls reached_limit() if they have void check_limits() { if (_words_scanned >= _words_scanned_limit || _refs_reached >= _refs_reached_limit) { reached_limit(); } } // this is supposed to be called regularly during a marking step as // it checks a bunch of conditions that might cause the marking step // to abort void regular_clock_call(); bool concurrent() { return _concurrent; } // Test whether objAddr might have already been passed over by the // mark bitmap scan, and so needs to be pushed onto the mark stack. bool is_below_finger(HeapWord* objAddr, HeapWord* global_finger) const; public: // It resets the task; it should be called right at the beginning of // a marking phase. void reset(CMBitMap* _nextMarkBitMap); // it clears all the fields that correspond to a claimed region. void clear_region_fields(); void set_concurrent(bool concurrent) { _concurrent = concurrent; } // The main method of this class which performs a marking step // trying not to exceed the given duration. However, it might exit // prematurely, according to some conditions (i.e. SATB buffers are // available for processing). void do_marking_step(double target_ms, bool do_termination, bool is_serial); // These two calls start and stop the timer void record_start_time() { _elapsed_time_ms = os::elapsedTime() * 1000.0; } void record_end_time() { _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; } // returns the worker ID associated with this task. uint worker_id() { return _worker_id; } // From TerminatorTerminator. It determines whether this task should // exit the termination protocol after it's entered it. virtual bool should_exit_termination(); // Resets the local region fields after a task has finished scanning a // region; or when they have become stale as a result of the region // being evacuated. void giveup_current_region(); HeapWord* finger() { return _finger; } bool has_aborted() { return _has_aborted; } void set_has_aborted() { _has_aborted = true; } void clear_has_aborted() { _has_aborted = false; } bool has_timed_out() { return _has_timed_out; } bool claimed() { return _claimed; } void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); // It grays the object by marking it and, if necessary, pushing it // on the local queue inline void deal_with_reference(oop obj); // It scans an object and visits its children. void scan_object(oop obj); // It pushes an object on the local queue. inline void push(oop obj); // These two move entries to/from the global stack. void move_entries_to_global_stack(); void get_entries_from_global_stack(); // It pops and scans objects from the local queue. If partially is // true, then it stops when the queue size is of a given limit. If // partially is false, then it stops when the queue is empty. void drain_local_queue(bool partially); // It moves entries from the global stack to the local queue and // drains the local queue. If partially is true, then it stops when // both the global stack and the local queue reach a given size. If // partially if false, it tries to empty them totally. void drain_global_stack(bool partially); // It keeps picking SATB buffers and processing them until no SATB // buffers are available. void drain_satb_buffers(); // moves the local finger to a new location inline void move_finger_to(HeapWord* new_finger) { assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); _finger = new_finger; } CMTask(uint worker_id, ConcurrentMark *cm, size_t* marked_bytes, BitMap* card_bm, CMTaskQueue* task_queue, CMTaskQueueSet* task_queues); // it prints statistics associated with this task void print_stats(); #if _MARKING_STATS_ void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; } #endif // _MARKING_STATS_ }; // Class that's used to to print out per-region liveness // information. It's currently used at the end of marking and also // after we sort the old regions at the end of the cleanup operation. class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { private: outputStream* _out; // Accumulators for these values. size_t _total_used_bytes; size_t _total_capacity_bytes; size_t _total_prev_live_bytes; size_t _total_next_live_bytes; // These are set up when we come across a "stars humongous" region // (as this is where most of this information is stored, not in the // subsequent "continues humongous" regions). After that, for every // region in a given humongous region series we deduce the right // values for it by simply subtracting the appropriate amount from // these fields. All these values should reach 0 after we've visited // the last region in the series. size_t _hum_used_bytes; size_t _hum_capacity_bytes; size_t _hum_prev_live_bytes; size_t _hum_next_live_bytes; // Accumulator for the remembered set size size_t _total_remset_bytes; // Accumulator for strong code roots memory size size_t _total_strong_code_roots_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