diff -r 000000000000 -r f90c822e73f8 src/share/vm/gc_implementation/g1/concurrentMark.hpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/gc_implementation/g1/concurrentMark.hpp Wed Apr 27 01:25:04 2016 +0800 @@ -0,0 +1,1292 @@ +/* + * 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 "gc_implementation/g1/heapRegionSet.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) { } + + bool do_object_b(oop obj); +}; + +// A generic CM bit map. This is essentially a wrapper around the BitMap +// class, with one bit per (1<<_shifter) HeapWords. + +class CMBitMapRO VALUE_OBJ_CLASS_SPEC { + protected: + HeapWord* _bmStartWord; // base address of range covered by map + size_t _bmWordSize; // map size (in #HeapWords covered) + const int _shifter; // map to char or bit + VirtualSpace _virtual_space; // underlying the bit map + BitMap _bm; // the bit map itself + + public: + // constructor + CMBitMapRO(int shifter); + + enum { do_yield = true }; + + // inquiries + HeapWord* startWord() const { return _bmStartWord; } + size_t sizeInWords() const { return _bmWordSize; } + // the following is one past the last word in space + HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } + + // read marks + + bool isMarked(HeapWord* addr) const { + assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), + "outside underlying space?"); + return _bm.at(heapWordToOffset(addr)); + } + + // iteration + inline bool iterate(BitMapClosure* cl, MemRegion mr); + inline bool iterate(BitMapClosure* cl); + + // Return the address corresponding to the next marked bit at or after + // "addr", and before "limit", if "limit" is non-NULL. If there is no + // such bit, returns "limit" if that is non-NULL, or else "endWord()". + HeapWord* getNextMarkedWordAddress(HeapWord* addr, + HeapWord* limit = NULL) const; + // Return the address corresponding to the next unmarked bit at or after + // "addr", and before "limit", if "limit" is non-NULL. If there is no + // such bit, returns "limit" if that is non-NULL, or else "endWord()". + HeapWord* getNextUnmarkedWordAddress(HeapWord* addr, + HeapWord* limit = NULL) const; + + // conversion utilities + HeapWord* offsetToHeapWord(size_t offset) const { + return _bmStartWord + (offset << _shifter); + } + size_t heapWordToOffset(HeapWord* addr) const { + return pointer_delta(addr, _bmStartWord) >> _shifter; + } + int heapWordDiffToOffsetDiff(size_t diff) const; + + // The argument addr should be the start address of a valid object + HeapWord* nextObject(HeapWord* addr) { + oop obj = (oop) addr; + HeapWord* res = addr + obj->size(); + assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity"); + return res; + } + + void print_on_error(outputStream* st, const char* prefix) const; + + // debugging + NOT_PRODUCT(bool covers(ReservedSpace rs) const;) +}; + +class CMBitMap : public CMBitMapRO { + + public: + // constructor + CMBitMap(int shifter) : + CMBitMapRO(shifter) {} + + // Allocates the back store for the marking bitmap + bool allocate(ReservedSpace heap_rs); + + // write marks + void mark(HeapWord* addr) { + assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), + "outside underlying space?"); + _bm.set_bit(heapWordToOffset(addr)); + } + void clear(HeapWord* addr) { + assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), + "outside underlying space?"); + _bm.clear_bit(heapWordToOffset(addr)); + } + bool parMark(HeapWord* addr) { + assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), + "outside underlying space?"); + return _bm.par_set_bit(heapWordToOffset(addr)); + } + bool parClear(HeapWord* addr) { + assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), + "outside underlying space?"); + return _bm.par_clear_bit(heapWordToOffset(addr)); + } + void markRange(MemRegion mr); + void clearAll(); + void clearRange(MemRegion mr); + + // Starting at the bit corresponding to "addr" (inclusive), find the next + // "1" bit, if any. This bit starts some run of consecutive "1"'s; find + // the end of this run (stopping at "end_addr"). Return the MemRegion + // covering from the start of the region corresponding to the first bit + // of the run to the end of the region corresponding to the last bit of + // the run. If there is no "1" bit at or after "addr", return an empty + // MemRegion. + MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr); +}; + +// Represents a marking stack used by ConcurrentMarking in the G1 collector. +class CMMarkStack VALUE_OBJ_CLASS_SPEC { + VirtualSpace _virtual_space; // Underlying backing store for actual stack + ConcurrentMark* _cm; + oop* _base; // bottom of stack + jint _index; // one more than last occupied index + jint _capacity; // max #elements + jint _saved_index; // value of _index saved at start of GC + NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run + + bool _overflow; + bool _should_expand; + DEBUG_ONLY(bool _drain_in_progress;) + DEBUG_ONLY(bool _drain_in_progress_yields;) + + public: + CMMarkStack(ConcurrentMark* cm); + ~CMMarkStack(); + +#ifndef PRODUCT + jint max_depth() const { + return _max_depth; + } +#endif + + bool allocate(size_t capacity); + + oop pop() { + if (!isEmpty()) { + return _base[--_index] ; + } + return NULL; + } + + // If overflow happens, don't do the push, and record the overflow. + // *Requires* that "ptr" is already marked. + void push(oop ptr) { + if (isFull()) { + // Record overflow. + _overflow = true; + return; + } else { + _base[_index++] = ptr; + NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); + } + } + // Non-block impl. Note: concurrency is allowed only with other + // "par_push" operations, not with "pop" or "drain". We would need + // parallel versions of them if such concurrency was desired. + void par_push(oop ptr); + + // Pushes the first "n" elements of "ptr_arr" on the stack. + // Non-block impl. Note: concurrency is allowed only with other + // "par_adjoin_arr" or "push" operations, not with "pop" or "drain". + void par_adjoin_arr(oop* ptr_arr, int n); + + // Pushes the first "n" elements of "ptr_arr" on the stack. + // Locking impl: concurrency is allowed only with + // "par_push_arr" and/or "par_pop_arr" operations, which use the same + // locking strategy. + void par_push_arr(oop* ptr_arr, int n); + + // If returns false, the array was empty. Otherwise, removes up to "max" + // elements from the stack, and transfers them to "ptr_arr" in an + // unspecified order. The actual number transferred is given in "n" ("n + // == 0" is deliberately redundant with the return value.) Locking impl: + // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr" + // operations, which use the same locking strategy. + bool par_pop_arr(oop* ptr_arr, int max, int* n); + + // Drain the mark stack, applying the given closure to all fields of + // objects on the stack. (That is, continue until the stack is empty, + // even if closure applications add entries to the stack.) The "bm" + // argument, if non-null, may be used to verify that only marked objects + // are on the mark stack. If "yield_after" is "true", then the + // concurrent marker performing the drain offers to yield after + // processing each object. If a yield occurs, stops the drain operation + // and returns false. Otherwise, returns true. + template + 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; + + // used when remark aborts due to an overflow to indicate that + // another concurrent marking phase should start + volatile bool _restart_for_overflow; + + // This is true from the very start of concurrent marking until the + // point when all the tasks complete their work. It is really used + // to determine the points between the end of concurrent marking and + // time of remark. + volatile bool _concurrent_marking_in_progress; + + // verbose level + CMVerboseLevel _verbose_level; + + // All of these times are in ms. + NumberSeq _init_times; + NumberSeq _remark_times; + NumberSeq _remark_mark_times; + NumberSeq _remark_weak_ref_times; + NumberSeq _cleanup_times; + double _total_counting_time; + double _total_rs_scrub_time; + + double* _accum_task_vtime; // accumulated task vtime + + FlexibleWorkGang* _parallel_workers; + + ForceOverflowSettings _force_overflow_conc; + ForceOverflowSettings _force_overflow_stw; + + void weakRefsWork(bool clear_all_soft_refs); + + void swapMarkBitMaps(); + + // It resets the global marking data structures, as well as the + // task local ones; should be called during initial mark. + void reset(); + + // Resets all the marking data structures. Called when we have to restart + // marking or when marking completes (via set_non_marking_state below). + void reset_marking_state(bool clear_overflow = true); + + // We do this after we're done with marking so that the marking data + // structures are initialised to a sensible and predictable state. + void set_non_marking_state(); + + // Called to indicate how many threads are currently active. + void set_concurrency(uint active_tasks); + + // It should be called to indicate which phase we're in (concurrent + // mark or remark) and how many threads are currently active. + void set_concurrency_and_phase(uint active_tasks, bool concurrent); + + // prints all gathered CM-related statistics + void print_stats(); + + bool cleanup_list_is_empty() { + return _cleanup_list.is_empty(); + } + + // accessor methods + uint parallel_marking_threads() const { return _parallel_marking_threads; } + uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;} + double sleep_factor() { return _sleep_factor; } + double marking_task_overhead() { return _marking_task_overhead;} + double cleanup_sleep_factor() { return _cleanup_sleep_factor; } + double cleanup_task_overhead() { return _cleanup_task_overhead;} + + bool use_parallel_marking_threads() const { + assert(parallel_marking_threads() <= + max_parallel_marking_threads(), "sanity"); + assert((_parallel_workers == NULL && parallel_marking_threads() == 0) || + parallel_marking_threads() > 0, + "parallel workers not set up correctly"); + return _parallel_workers != NULL; + } + + HeapWord* finger() { return _finger; } + bool concurrent() { return _concurrent; } + uint active_tasks() { return _active_tasks; } + ParallelTaskTerminator* terminator() { return &_terminator; } + + // It claims the next available region to be scanned by a marking + // task/thread. It might return NULL if the next region is empty or + // we have run out of regions. In the latter case, out_of_regions() + // determines whether we've really run out of regions or the task + // should call claim_region() again. This might seem a bit + // awkward. Originally, the code was written so that claim_region() + // either successfully returned with a non-empty region or there + // were no more regions to be claimed. The problem with this was + // that, in certain circumstances, it iterated over large chunks of + // the heap finding only empty regions and, while it was working, it + // was preventing the calling task to call its regular clock + // method. So, this way, each task will spend very little time in + // claim_region() and is allowed to call the regular clock method + // frequently. + HeapRegion* claim_region(uint worker_id); + + // It determines whether we've run out of regions to scan. 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, ReservedSpace heap_rs); + ~ConcurrentMark(); + + ConcurrentMarkThread* cmThread() { return _cmThread; } + + CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; } + CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; } + + // Returns the number of GC threads to be used in a concurrent + // phase based on the number of GC threads being used in a STW + // phase. + uint scale_parallel_threads(uint n_par_threads); + + // Calculates the number of GC threads to be used in a concurrent phase. + uint calc_parallel_marking_threads(); + + // The following three are interaction between CM and + // G1CollectedHeap + + // This notifies CM that a root during initial-mark needs to be + // grayed. It is MT-safe. word_size is the size of the object in + // words. It is passed explicitly as sometimes we cannot calculate + // it from the given object because it might be in an inconsistent + // state (e.g., in to-space and being copied). So the caller is + // responsible for dealing with this issue (e.g., get the size from + // the from-space image when the to-space image might be + // inconsistent) and always passing the size. hr is the region that + // contains the object and it's passed optionally from callers who + // might already have it (no point in recalculating it). + inline void grayRoot(oop obj, size_t word_size, + uint worker_id, HeapRegion* hr = NULL); + + // It iterates over the heap and for each object it comes across it + // will dump the contents of its reference fields, as well as + // liveness information for the object and its referents. The dump + // will be written to a file with the following name: + // G1PrintReachableBaseFile + "." + str. + // vo decides whether the prev (vo == UsePrevMarking), the next + // (vo == UseNextMarking) marking information, or the mark word + // (vo == UseMarkWord) will be used to determine the liveness of + // each object / referent. + // If all is true, all objects in the heap will be dumped, otherwise + // only the live ones. In the dump the following symbols / breviations + // are used: + // M : an explicitly live object (its bitmap bit is set) + // > : an implicitly live object (over tams) + // O : an object outside the G1 heap (typically: in the perm gen) + // NOT : a reference field whose referent is not live + // AND MARKED : indicates that an object is both explicitly and + // implicitly live (it should be one or the other, not both) + void print_reachable(const char* str, + VerifyOption vo, bool all) PRODUCT_RETURN; + + // Clear the next marking bitmap (will be called concurrently). + void clearNextBitmap(); + + // These two do the work that needs to be done before and after the + // initial root checkpoint. Since this checkpoint can be done at two + // different points (i.e. an explicit pause or piggy-backed on a + // young collection), then it's nice to be able to easily share the + // pre/post code. It might be the case that we can put everything in + // the post method. TP + void checkpointRootsInitialPre(); + void checkpointRootsInitialPost(); + + // Scan all the root regions and mark everything reachable from + // them. + void scanRootRegions(); + + // Scan a single root region and mark everything reachable from it. + void scanRootRegion(HeapRegion* hr, uint worker_id); + + // Do concurrent phase of marking, to a tentative transitive closure. + void markFromRoots(); + + void checkpointRootsFinal(bool clear_all_soft_refs); + void checkpointRootsFinalWork(); + void cleanup(); + void completeCleanup(); + + // Mark in the previous bitmap. NB: this is usually read-only, so use + // this carefully! + inline void markPrev(oop p); + + // Clears marks for all objects in the given range, for the prev, + // next, or both bitmaps. NB: the previous bitmap is usually + // read-only, so use this carefully! + void clearRangePrevBitmap(MemRegion mr); + void clearRangeNextBitmap(MemRegion mr); + void clearRangeBothBitmaps(MemRegion mr); + + // Notify data structures that a GC has started. + void note_start_of_gc() { + _markStack.note_start_of_gc(); + } + + // Notify data structures that a GC is finished. + void note_end_of_gc() { + _markStack.note_end_of_gc(); + } + + // Verify that there are no CSet oops on the stacks (taskqueues / + // global mark stack), enqueued SATB buffers, per-thread SATB + // buffers, and fingers (global / per-task). The boolean parameters + // decide which of the above data structures to verify. If marking + // is not in progress, it's a no-op. + void verify_no_cset_oops(bool verify_stacks, + bool verify_enqueued_buffers, + bool verify_thread_buffers, + bool verify_fingers) PRODUCT_RETURN; + + // It is called at the end of an evacuation pause during marking so + // that CM is notified of where the new end of the heap is. It + // doesn't do anything if concurrent_marking_in_progress() is false, + // unless the force parameter is true. + void update_g1_committed(bool force = false); + + bool isMarked(oop p) const { + assert(p != NULL && p->is_oop(), "expected an oop"); + HeapWord* addr = (HeapWord*)p; + assert(addr >= _nextMarkBitMap->startWord() || + addr < _nextMarkBitMap->endWord(), "in a region"); + + return _nextMarkBitMap->isMarked(addr); + } + + inline bool not_yet_marked(oop p) const; + + // XXX Debug code + bool containing_card_is_marked(void* p); + bool containing_cards_are_marked(void* start, void* last); + + bool isPrevMarked(oop p) const { + assert(p != NULL && p->is_oop(), "expected an oop"); + HeapWord* addr = (HeapWord*)p; + assert(addr >= _prevMarkBitMap->startWord() || + addr < _prevMarkBitMap->endWord(), "in a region"); + + return _prevMarkBitMap->isMarked(addr); + } + + inline bool do_yield_check(uint worker_i = 0); + inline bool should_yield(); + + // Called to abort the marking cycle after a Full GC takes palce. + void abort(); + + bool has_aborted() { return _has_aborted; } + + // 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 memory region in the task/worker counting + // data structures for the given worker id. + inline void count_region(MemRegion mr, uint worker_id); + + // Counts the given object in the given task/worker counting + // data structures. + inline void count_object(oop obj, HeapRegion* hr, + size_t* marked_bytes_array, + BitMap* task_card_bm); + + // Counts the given object in the task/worker counting data + // structures for the given worker id. + inline void count_object(oop obj, HeapRegion* hr, uint worker_id); + + // Attempts to mark the given object and, if successful, counts + // the object in the given task/worker counting structures. + inline bool par_mark_and_count(oop obj, HeapRegion* hr, + size_t* marked_bytes_array, + BitMap* task_card_bm); + + // Attempts to mark the given object and, if successful, counts + // the object in the task/worker counting structures for the + // given worker id. + inline bool par_mark_and_count(oop obj, size_t word_size, + HeapRegion* hr, uint worker_id); + + // Attempts to mark the given object and, if successful, counts + // the object in the task/worker counting structures for the + // given worker id. + inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id); + + // Similar to the above routine but we don't know the heap region that + // contains the object to be marked/counted, which this routine looks up. + inline bool par_mark_and_count(oop obj, uint worker_id); + + // Similar to the above routine but there are times when we cannot + // safely calculate the size of obj due to races and we, therefore, + // pass the size in as a parameter. It is the caller's reponsibility + // to ensure that the size passed in for obj is valid. + inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id); + + // Unconditionally mark the given object, and unconditinally count + // the object in the counting structures for worker id 0. + // Should *not* be called from parallel code. + inline bool mark_and_count(oop obj, HeapRegion* hr); + + // Similar to the above routine but we don't know the heap region that + // contains the object to be marked/counted, which this routine looks up. + // Should *not* be called from parallel code. + inline bool mark_and_count(oop obj); + + // Returns true if initialization was successfully completed. + bool completed_initialization() const { + return _completed_initialization; + } + +protected: + // Clear all the per-task bitmaps and arrays used to store the + // counting data. + void clear_all_count_data(); + + // Aggregates the counting data for each worker/task + // that was constructed while marking. Also sets + // the amount of marked bytes for each region and + // the top at concurrent mark count. + void aggregate_count_data(); + + // Verification routine + void verify_count_data(); +}; + +// A class representing a marking task. +class CMTask : public TerminatorTerminator { +private: + enum PrivateConstants { + // the regular clock call is called once the scanned words reaches + // this limit + words_scanned_period = 12*1024, + // the regular clock call is called once the number of visited + // references reaches this limit + refs_reached_period = 384, + // initial value for the hash seed, used in the work stealing code + init_hash_seed = 17, + // how many entries will be transferred between global stack and + // local queues + global_stack_transfer_size = 16 + }; + + uint _worker_id; + G1CollectedHeap* _g1h; + ConcurrentMark* _cm; + CMBitMap* _nextMarkBitMap; + // the task queue of this task + CMTaskQueue* _task_queue; +private: + // the task queue set---needed for stealing + CMTaskQueueSet* _task_queues; + // indicates whether the task has been claimed---this is only for + // debugging purposes + bool _claimed; + + // number of calls to this task + int _calls; + + // when the virtual timer reaches this time, the marking step should + // exit + double _time_target_ms; + // the start time of the current marking step + double _start_time_ms; + + // the oop closure used for iterations over oops + G1CMOopClosure* _cm_oop_closure; + + // the region this task is scanning, NULL if we're not scanning any + HeapRegion* _curr_region; + // the local finger of this task, NULL if we're not scanning a region + HeapWord* _finger; + // limit of the region this task is scanning, NULL if we're not scanning one + HeapWord* _region_limit; + + // the number of words this task has scanned + size_t _words_scanned; + // When _words_scanned reaches this limit, the regular clock is + // called. Notice that this might be decreased under certain + // circumstances (i.e. when we believe that we did an expensive + // operation). + size_t _words_scanned_limit; + // the initial value of _words_scanned_limit (i.e. what it was + // before it was decreased). + size_t _real_words_scanned_limit; + + // the number of references this task has visited + size_t _refs_reached; + // When _refs_reached reaches this limit, the regular clock is + // called. Notice this this might be decreased under certain + // circumstances (i.e. when we believe that we did an expensive + // operation). + size_t _refs_reached_limit; + // the initial value of _refs_reached_limit (i.e. what it was before + // it was decreased). + size_t _real_refs_reached_limit; + + // used by the work stealing stuff + int _hash_seed; + // if this is true, then the task has aborted for some reason + bool _has_aborted; + // set when the task aborts because it has met its time quota + bool _has_timed_out; + // true when we're draining SATB buffers; this avoids the task + // aborting due to SATB buffers being available (as we're already + // dealing with them) + bool _draining_satb_buffers; + + // number sequence of past step times + NumberSeq _step_times_ms; + // elapsed time of this task + double _elapsed_time_ms; + // termination time of this task + double _termination_time_ms; + // when this task got into the termination protocol + double _termination_start_time_ms; + + // true when the task is during a concurrent phase, false when it is + // in the remark phase (so, in the latter case, we do not have to + // check all the things that we have to check during the concurrent + // phase, i.e. SATB buffer availability...) + bool _concurrent; + + TruncatedSeq _marking_step_diffs_ms; + + // Counting data structures. Embedding the task's marked_bytes_array + // and card bitmap into the actual task saves having to go through + // the ConcurrentMark object. + size_t* _marked_bytes_array; + BitMap* _card_bm; + + // LOTS of statistics related with this task +#if _MARKING_STATS_ + NumberSeq _all_clock_intervals_ms; + double _interval_start_time_ms; + + int _aborted; + int _aborted_overflow; + int _aborted_cm_aborted; + int _aborted_yield; + int _aborted_timed_out; + int _aborted_satb; + int _aborted_termination; + + int _steal_attempts; + int _steals; + + int _clock_due_to_marking; + int _clock_due_to_scanning; + + int _local_pushes; + int _local_pops; + int _local_max_size; + int _objs_scanned; + + int _global_pushes; + int _global_pops; + int _global_max_size; + + int _global_transfers_to; + int _global_transfers_from; + + int _regions_claimed; + int _objs_found_on_bitmap; + + int _satb_buffers_processed; +#endif // _MARKING_STATS_ + + // it updates the local fields after this task has claimed + // a new region to scan + void setup_for_region(HeapRegion* hr); + // it brings up-to-date the limit of the region + void update_region_limit(); + + // called when either the words scanned or the refs visited limit + // has been reached + void reached_limit(); + // recalculates the words scanned and refs visited limits + void recalculate_limits(); + // decreases the words scanned and refs visited limits when we reach + // an expensive operation + void decrease_limits(); + // it checks whether the words scanned or refs visited reached their + // respective limit and calls reached_limit() if they have + void check_limits() { + if (_words_scanned >= _words_scanned_limit || + _refs_reached >= _refs_reached_limit) { + reached_limit(); + } + } + // this is supposed to be called regularly during a marking step as + // it checks a bunch of conditions that might cause the marking step + // to abort + void regular_clock_call(); + bool concurrent() { return _concurrent; } + +public: + // It resets the task; it should be called right at the beginning of + // a marking phase. + void reset(CMBitMap* _nextMarkBitMap); + // it clears all the fields that correspond to a claimed region. + void clear_region_fields(); + + void set_concurrent(bool concurrent) { _concurrent = concurrent; } + + // The main method of this class which performs a marking step + // trying not to exceed the given duration. However, it might exit + // prematurely, according to some conditions (i.e. SATB buffers are + // available for processing). + void do_marking_step(double target_ms, + bool do_termination, + bool is_serial); + + // These two calls start and stop the timer + void record_start_time() { + _elapsed_time_ms = os::elapsedTime() * 1000.0; + } + void record_end_time() { + _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; + } + + // returns the worker ID associated with this task. + uint worker_id() { return _worker_id; } + + // From TerminatorTerminator. It determines whether this task should + // exit the termination protocol after it's entered it. + virtual bool should_exit_termination(); + + // Resets the local region fields after a task has finished scanning a + // region; or when they have become stale as a result of the region + // being evacuated. + void giveup_current_region(); + + HeapWord* finger() { return _finger; } + + bool has_aborted() { return _has_aborted; } + void set_has_aborted() { _has_aborted = true; } + void clear_has_aborted() { _has_aborted = false; } + bool has_timed_out() { return _has_timed_out; } + bool claimed() { return _claimed; } + + void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); + + // It grays the object by marking it and, if necessary, pushing it + // on the local queue + inline void deal_with_reference(oop obj); + + // It scans an object and visits its children. + void scan_object(oop obj); + + // It pushes an object on the local queue. + inline void push(oop obj); + + // These two move entries to/from the global stack. + void move_entries_to_global_stack(); + void get_entries_from_global_stack(); + + // It pops and scans objects from the local queue. If partially is + // true, then it stops when the queue size is of a given limit. If + // partially is false, then it stops when the queue is empty. + void drain_local_queue(bool partially); + // It moves entries from the global stack to the local queue and + // drains the local queue. If partially is true, then it stops when + // both the global stack and the local queue reach a given size. If + // partially if false, it tries to empty them totally. + void drain_global_stack(bool partially); + // It keeps picking SATB buffers and processing them until no SATB + // buffers are available. + void drain_satb_buffers(); + + // moves the local finger to a new location + inline void move_finger_to(HeapWord* new_finger) { + assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); + _finger = new_finger; + } + + CMTask(uint worker_id, ConcurrentMark *cm, + size_t* marked_bytes, BitMap* card_bm, + CMTaskQueue* task_queue, CMTaskQueueSet* task_queues); + + // it prints statistics associated with this task + void print_stats(); + +#if _MARKING_STATS_ + void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; } +#endif // _MARKING_STATS_ +}; + +// Class that's used to to print out per-region liveness +// information. It's currently used at the end of marking and also +// after we sort the old regions at the end of the cleanup operation. +class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { +private: + outputStream* _out; + + // Accumulators for these values. + size_t _total_used_bytes; + size_t _total_capacity_bytes; + size_t _total_prev_live_bytes; + size_t _total_next_live_bytes; + + // These are set up when we come across a "stars humongous" region + // (as this is where most of this information is stored, not in the + // subsequent "continues humongous" regions). After that, for every + // region in a given humongous region series we deduce the right + // values for it by simply subtracting the appropriate amount from + // these fields. All these values should reach 0 after we've visited + // the last region in the series. + size_t _hum_used_bytes; + size_t _hum_capacity_bytes; + size_t _hum_prev_live_bytes; + size_t _hum_next_live_bytes; + + // 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