diff -r 0b27f3512f9e -r 37f87013dfd8 src/share/vm/gc_implementation/g1/concurrentMark.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/gc_implementation/g1/concurrentMark.cpp Thu Jun 05 15:57:56 2008 -0700 @@ -0,0 +1,3957 @@ +/* + * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +#include "incls/_precompiled.incl" +#include "incls/_concurrentMark.cpp.incl" + +// +// CMS Bit Map Wrapper + +CMBitMapRO::CMBitMapRO(ReservedSpace rs, int shifter): + _bm((uintptr_t*)NULL,0), + _shifter(shifter) { + _bmStartWord = (HeapWord*)(rs.base()); + _bmWordSize = rs.size()/HeapWordSize; // rs.size() is in bytes + ReservedSpace brs(ReservedSpace::allocation_align_size_up( + (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1)); + + guarantee(brs.is_reserved(), "couldn't allocate CMS bit map"); + // For now we'll just commit all of the bit map up fromt. + // Later on we'll try to be more parsimonious with swap. + guarantee(_virtual_space.initialize(brs, brs.size()), + "couldn't reseve backing store for CMS bit map"); + assert(_virtual_space.committed_size() == brs.size(), + "didn't reserve backing store for all of CMS bit map?"); + _bm.set_map((uintptr_t*)_virtual_space.low()); + assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >= + _bmWordSize, "inconsistency in bit map sizing"); + _bm.set_size(_bmWordSize >> _shifter); +} + +HeapWord* CMBitMapRO::getNextMarkedWordAddress(HeapWord* addr, + HeapWord* limit) const { + // First we must round addr *up* to a possible object boundary. + addr = (HeapWord*)align_size_up((intptr_t)addr, + HeapWordSize << _shifter); + size_t addrOffset = heapWordToOffset(addr); + if (limit == NULL) limit = _bmStartWord + _bmWordSize; + size_t limitOffset = heapWordToOffset(limit); + size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset); + HeapWord* nextAddr = offsetToHeapWord(nextOffset); + assert(nextAddr >= addr, "get_next_one postcondition"); + assert(nextAddr == limit || isMarked(nextAddr), + "get_next_one postcondition"); + return nextAddr; +} + +HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(HeapWord* addr, + HeapWord* limit) const { + size_t addrOffset = heapWordToOffset(addr); + if (limit == NULL) limit = _bmStartWord + _bmWordSize; + size_t limitOffset = heapWordToOffset(limit); + size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset); + HeapWord* nextAddr = offsetToHeapWord(nextOffset); + assert(nextAddr >= addr, "get_next_one postcondition"); + assert(nextAddr == limit || !isMarked(nextAddr), + "get_next_one postcondition"); + return nextAddr; +} + +int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const { + assert((diff & ((1 << _shifter) - 1)) == 0, "argument check"); + return (int) (diff >> _shifter); +} + +bool CMBitMapRO::iterate(BitMapClosure* cl, MemRegion mr) { + HeapWord* left = MAX2(_bmStartWord, mr.start()); + HeapWord* right = MIN2(_bmStartWord + _bmWordSize, mr.end()); + if (right > left) { + // Right-open interval [leftOffset, rightOffset). + return _bm.iterate(cl, heapWordToOffset(left), heapWordToOffset(right)); + } else { + return true; + } +} + +void CMBitMapRO::mostly_disjoint_range_union(BitMap* from_bitmap, + size_t from_start_index, + HeapWord* to_start_word, + size_t word_num) { + _bm.mostly_disjoint_range_union(from_bitmap, + from_start_index, + heapWordToOffset(to_start_word), + word_num); +} + +#ifndef PRODUCT +bool CMBitMapRO::covers(ReservedSpace rs) const { + // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); + assert(((size_t)_bm.size() * (1 << _shifter)) == _bmWordSize, + "size inconsistency"); + return _bmStartWord == (HeapWord*)(rs.base()) && + _bmWordSize == rs.size()>>LogHeapWordSize; +} +#endif + +void CMBitMap::clearAll() { + _bm.clear(); + return; +} + +void CMBitMap::markRange(MemRegion mr) { + mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); + assert(!mr.is_empty(), "unexpected empty region"); + assert((offsetToHeapWord(heapWordToOffset(mr.end())) == + ((HeapWord *) mr.end())), + "markRange memory region end is not card aligned"); + // convert address range into offset range + _bm.at_put_range(heapWordToOffset(mr.start()), + heapWordToOffset(mr.end()), true); +} + +void CMBitMap::clearRange(MemRegion mr) { + mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); + assert(!mr.is_empty(), "unexpected empty region"); + // convert address range into offset range + _bm.at_put_range(heapWordToOffset(mr.start()), + heapWordToOffset(mr.end()), false); +} + +MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr, + HeapWord* end_addr) { + HeapWord* start = getNextMarkedWordAddress(addr); + start = MIN2(start, end_addr); + HeapWord* end = getNextUnmarkedWordAddress(start); + end = MIN2(end, end_addr); + assert(start <= end, "Consistency check"); + MemRegion mr(start, end); + if (!mr.is_empty()) { + clearRange(mr); + } + return mr; +} + +CMMarkStack::CMMarkStack(ConcurrentMark* cm) : + _base(NULL), _cm(cm) +#ifdef ASSERT + , _drain_in_progress(false) + , _drain_in_progress_yields(false) +#endif +{} + +void CMMarkStack::allocate(size_t size) { + _base = NEW_C_HEAP_ARRAY(oop, size); + if (_base == NULL) + vm_exit_during_initialization("Failed to allocate " + "CM region mark stack"); + _index = 0; + // QQQQ cast ... + _capacity = (jint) size; + _oops_do_bound = -1; + NOT_PRODUCT(_max_depth = 0); +} + +CMMarkStack::~CMMarkStack() { + if (_base != NULL) FREE_C_HEAP_ARRAY(oop, _base); +} + +void CMMarkStack::par_push(oop ptr) { + while (true) { + if (isFull()) { + _overflow = true; + return; + } + // Otherwise... + jint index = _index; + jint next_index = index+1; + jint res = Atomic::cmpxchg(next_index, &_index, index); + if (res == index) { + _base[index] = ptr; + // Note that we don't maintain this atomically. We could, but it + // doesn't seem necessary. + NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index)); + return; + } + // Otherwise, we need to try again. + } +} + +void CMMarkStack::par_adjoin_arr(oop* ptr_arr, int n) { + while (true) { + if (isFull()) { + _overflow = true; + return; + } + // Otherwise... + jint index = _index; + jint next_index = index + n; + if (next_index > _capacity) { + _overflow = true; + return; + } + jint res = Atomic::cmpxchg(next_index, &_index, index); + if (res == index) { + for (int i = 0; i < n; i++) { + int ind = index + i; + assert(ind < _capacity, "By overflow test above."); + _base[ind] = ptr_arr[i]; + } + NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index)); + return; + } + // Otherwise, we need to try again. + } +} + + +void CMMarkStack::par_push_arr(oop* ptr_arr, int n) { + MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); + jint start = _index; + jint next_index = start + n; + if (next_index > _capacity) { + _overflow = true; + return; + } + // Otherwise. + _index = next_index; + for (int i = 0; i < n; i++) { + int ind = start + i; + guarantee(ind < _capacity, "By overflow test above."); + _base[ind] = ptr_arr[i]; + } +} + + +bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) { + MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); + jint index = _index; + if (index == 0) { + *n = 0; + return false; + } else { + int k = MIN2(max, index); + jint new_ind = index - k; + for (int j = 0; j < k; j++) { + ptr_arr[j] = _base[new_ind + j]; + } + _index = new_ind; + *n = k; + return true; + } +} + + +CMRegionStack::CMRegionStack() : _base(NULL) {} + +void CMRegionStack::allocate(size_t size) { + _base = NEW_C_HEAP_ARRAY(MemRegion, size); + if (_base == NULL) + vm_exit_during_initialization("Failed to allocate " + "CM region mark stack"); + _index = 0; + // QQQQ cast ... + _capacity = (jint) size; +} + +CMRegionStack::~CMRegionStack() { + if (_base != NULL) FREE_C_HEAP_ARRAY(oop, _base); +} + +void CMRegionStack::push(MemRegion mr) { + assert(mr.word_size() > 0, "Precondition"); + while (true) { + if (isFull()) { + _overflow = true; + return; + } + // Otherwise... + jint index = _index; + jint next_index = index+1; + jint res = Atomic::cmpxchg(next_index, &_index, index); + if (res == index) { + _base[index] = mr; + return; + } + // Otherwise, we need to try again. + } +} + +MemRegion CMRegionStack::pop() { + while (true) { + // Otherwise... + jint index = _index; + + if (index == 0) { + return MemRegion(); + } + jint next_index = index-1; + jint res = Atomic::cmpxchg(next_index, &_index, index); + if (res == index) { + MemRegion mr = _base[next_index]; + if (mr.start() != NULL) { + tmp_guarantee_CM( mr.end() != NULL, "invariant" ); + tmp_guarantee_CM( mr.word_size() > 0, "invariant" ); + return mr; + } else { + // that entry was invalidated... let's skip it + tmp_guarantee_CM( mr.end() == NULL, "invariant" ); + } + } + // Otherwise, we need to try again. + } +} + +bool CMRegionStack::invalidate_entries_into_cset() { + bool result = false; + G1CollectedHeap* g1h = G1CollectedHeap::heap(); + for (int i = 0; i < _oops_do_bound; ++i) { + MemRegion mr = _base[i]; + if (mr.start() != NULL) { + tmp_guarantee_CM( mr.end() != NULL, "invariant"); + tmp_guarantee_CM( mr.word_size() > 0, "invariant" ); + HeapRegion* hr = g1h->heap_region_containing(mr.start()); + tmp_guarantee_CM( hr != NULL, "invariant" ); + if (hr->in_collection_set()) { + // The region points into the collection set + _base[i] = MemRegion(); + result = true; + } + } else { + // that entry was invalidated... let's skip it + tmp_guarantee_CM( mr.end() == NULL, "invariant" ); + } + } + return result; +} + +template +bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) { + assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after + || SafepointSynchronize::is_at_safepoint(), + "Drain recursion must be yield-safe."); + bool res = true; + debug_only(_drain_in_progress = true); + debug_only(_drain_in_progress_yields = yield_after); + while (!isEmpty()) { + oop newOop = pop(); + assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop"); + assert(newOop->is_oop(), "Expected an oop"); + assert(bm == NULL || bm->isMarked((HeapWord*)newOop), + "only grey objects on this stack"); + // iterate over the oops in this oop, marking and pushing + // the ones in CMS generation. + newOop->oop_iterate(cl); + if (yield_after && _cm->do_yield_check()) { + res = false; break; + } + } + debug_only(_drain_in_progress = false); + return res; +} + +void CMMarkStack::oops_do(OopClosure* f) { + if (_index == 0) return; + assert(_oops_do_bound != -1 && _oops_do_bound <= _index, + "Bound must be set."); + for (int i = 0; i < _oops_do_bound; i++) { + f->do_oop(&_base[i]); + } + _oops_do_bound = -1; +} + +bool ConcurrentMark::not_yet_marked(oop obj) const { + return (_g1h->is_obj_ill(obj) + || (_g1h->is_in_permanent(obj) + && !nextMarkBitMap()->isMarked((HeapWord*)obj))); +} + +#ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away +#pragma warning( disable:4355 ) // 'this' : used in base member initializer list +#endif // _MSC_VER + +ConcurrentMark::ConcurrentMark(ReservedSpace rs, + int max_regions) : + _markBitMap1(rs, MinObjAlignment - 1), + _markBitMap2(rs, MinObjAlignment - 1), + + _parallel_marking_threads(0), + _sleep_factor(0.0), + _marking_task_overhead(1.0), + _cleanup_sleep_factor(0.0), + _cleanup_task_overhead(1.0), + _region_bm(max_regions, false /* in_resource_area*/), + _card_bm((rs.size() + CardTableModRefBS::card_size - 1) >> + CardTableModRefBS::card_shift, + false /* in_resource_area*/), + _prevMarkBitMap(&_markBitMap1), + _nextMarkBitMap(&_markBitMap2), + _at_least_one_mark_complete(false), + + _markStack(this), + _regionStack(), + // _finger set in set_non_marking_state + + _max_task_num(MAX2(ParallelGCThreads, (size_t)1)), + // _active_tasks set in set_non_marking_state + // _tasks set inside the constructor + _task_queues(new CMTaskQueueSet((int) _max_task_num)), + _terminator(ParallelTaskTerminator((int) _max_task_num, _task_queues)), + + _has_overflown(false), + _concurrent(false), + + // _verbose_level set below + + _init_times(), + _remark_times(), _remark_mark_times(), _remark_weak_ref_times(), + _cleanup_times(), + _total_counting_time(0.0), + _total_rs_scrub_time(0.0), + + _parallel_workers(NULL), + _cleanup_co_tracker(G1CLGroup) +{ + CMVerboseLevel verbose_level = + (CMVerboseLevel) G1MarkingVerboseLevel; + if (verbose_level < no_verbose) + verbose_level = no_verbose; + if (verbose_level > high_verbose) + verbose_level = high_verbose; + _verbose_level = verbose_level; + + if (verbose_low()) + gclog_or_tty->print_cr("[global] init, heap start = "PTR_FORMAT", " + "heap end = "PTR_FORMAT, _heap_start, _heap_end); + + _markStack.allocate(G1CMStackSize); + _regionStack.allocate(G1CMRegionStackSize); + + // Create & start a ConcurrentMark thread. + if (G1ConcMark) { + _cmThread = new ConcurrentMarkThread(this); + assert(cmThread() != NULL, "CM Thread should have been created"); + assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm"); + } else { + _cmThread = NULL; + } + _g1h = G1CollectedHeap::heap(); + assert(CGC_lock != NULL, "Where's the CGC_lock?"); + assert(_markBitMap1.covers(rs), "_markBitMap1 inconsistency"); + assert(_markBitMap2.covers(rs), "_markBitMap2 inconsistency"); + + SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set(); + satb_qs.set_buffer_size(G1SATBLogBufferSize); + + int size = (int) MAX2(ParallelGCThreads, (size_t)1); + _par_cleanup_thread_state = NEW_C_HEAP_ARRAY(ParCleanupThreadState*, size); + for (int i = 0 ; i < size; i++) { + _par_cleanup_thread_state[i] = new ParCleanupThreadState; + } + + _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_task_num); + _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_task_num); + + // so that the assertion in MarkingTaskQueue::task_queue doesn't fail + _active_tasks = _max_task_num; + for (int i = 0; i < (int) _max_task_num; ++i) { + CMTaskQueue* task_queue = new CMTaskQueue(); + task_queue->initialize(); + _task_queues->register_queue(i, task_queue); + + _tasks[i] = new CMTask(i, this, task_queue, _task_queues); + _accum_task_vtime[i] = 0.0; + } + + if (ParallelMarkingThreads > ParallelGCThreads) { + vm_exit_during_initialization("Can't have more ParallelMarkingThreads " + "than ParallelGCThreads."); + } + if (ParallelGCThreads == 0) { + // if we are not running with any parallel GC threads we will not + // spawn any marking threads either + _parallel_marking_threads = 0; + _sleep_factor = 0.0; + _marking_task_overhead = 1.0; + } else { + if (ParallelMarkingThreads > 0) { + // notice that ParallelMarkingThreads overwrites G1MarkingOverheadPerc + // if both are set + + _parallel_marking_threads = ParallelMarkingThreads; + _sleep_factor = 0.0; + _marking_task_overhead = 1.0; + } else if (G1MarkingOverheadPerc > 0) { + // we will calculate the number of parallel marking threads + // based on a target overhead with respect to the soft real-time + // goal + + double marking_overhead = (double) G1MarkingOverheadPerc / 100.0; + double overall_cm_overhead = + (double) G1MaxPauseTimeMS * marking_overhead / (double) G1TimeSliceMS; + double cpu_ratio = 1.0 / (double) os::processor_count(); + double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio); + double marking_task_overhead = + overall_cm_overhead / marking_thread_num * + (double) os::processor_count(); + double sleep_factor = + (1.0 - marking_task_overhead) / marking_task_overhead; + + _parallel_marking_threads = (size_t) marking_thread_num; + _sleep_factor = sleep_factor; + _marking_task_overhead = marking_task_overhead; + } else { + _parallel_marking_threads = MAX2((ParallelGCThreads + 2) / 4, (size_t)1); + _sleep_factor = 0.0; + _marking_task_overhead = 1.0; + } + + if (parallel_marking_threads() > 1) + _cleanup_task_overhead = 1.0; + else + _cleanup_task_overhead = marking_task_overhead(); + _cleanup_sleep_factor = + (1.0 - cleanup_task_overhead()) / cleanup_task_overhead(); + +#if 0 + gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads()); + gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead()); + gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor()); + gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead()); + gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor()); +#endif + + guarantee( parallel_marking_threads() > 0, "peace of mind" ); + _parallel_workers = new WorkGang("Parallel Marking Threads", + (int) parallel_marking_threads(), false, true); + if (_parallel_workers == NULL) + vm_exit_during_initialization("Failed necessary allocation."); + } + + // so that the call below can read a sensible value + _heap_start = (HeapWord*) rs.base(); + set_non_marking_state(); +} + +void ConcurrentMark::update_g1_committed(bool force) { + // If concurrent marking is not in progress, then we do not need to + // update _heap_end. This has a subtle and important + // side-effect. Imagine that two evacuation pauses happen between + // marking completion and remark. The first one can grow the + // heap (hence now the finger is below the heap end). Then, the + // second one could unnecessarily push regions on the region + // stack. This causes the invariant that the region stack is empty + // at the beginning of remark to be false. By ensuring that we do + // not observe heap expansions after marking is complete, then we do + // not have this problem. + if (!concurrent_marking_in_progress() && !force) + return; + + MemRegion committed = _g1h->g1_committed(); + tmp_guarantee_CM( committed.start() == _heap_start, + "start shouldn't change" ); + HeapWord* new_end = committed.end(); + if (new_end > _heap_end) { + // The heap has been expanded. + + _heap_end = new_end; + } + // Notice that the heap can also shrink. However, this only happens + // during a Full GC (at least currently) and the entire marking + // phase will bail out and the task will not be restarted. So, let's + // do nothing. +} + +void ConcurrentMark::reset() { + // Starting values for these two. This should be called in a STW + // phase. CM will be notified of any future g1_committed expansions + // will be at the end of evacuation pauses, when tasks are + // inactive. + MemRegion committed = _g1h->g1_committed(); + _heap_start = committed.start(); + _heap_end = committed.end(); + + guarantee( _heap_start != NULL && + _heap_end != NULL && + _heap_start < _heap_end, "heap bounds should look ok" ); + + // reset all the marking data structures and any necessary flags + clear_marking_state(); + + if (verbose_low()) + gclog_or_tty->print_cr("[global] resetting"); + + // We do reset all of them, since different phases will use + // different number of active threads. So, it's easiest to have all + // of them ready. + for (int i = 0; i < (int) _max_task_num; ++i) + _tasks[i]->reset(_nextMarkBitMap); + + // we need this to make sure that the flag is on during the evac + // pause with initial mark piggy-backed + set_concurrent_marking_in_progress(); +} + +void ConcurrentMark::set_phase(size_t active_tasks, bool concurrent) { + guarantee( active_tasks <= _max_task_num, "we should not have more" ); + + _active_tasks = active_tasks; + // Need to update the three data structures below according to the + // number of active threads for this phase. + _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues); + _first_overflow_barrier_sync.set_n_workers((int) active_tasks); + _second_overflow_barrier_sync.set_n_workers((int) active_tasks); + + _concurrent = concurrent; + // We propagate this to all tasks, not just the active ones. + for (int i = 0; i < (int) _max_task_num; ++i) + _tasks[i]->set_concurrent(concurrent); + + if (concurrent) { + set_concurrent_marking_in_progress(); + } else { + // We currently assume that the concurrent flag has been set to + // false before we start remark. At this point we should also be + // in a STW phase. + guarantee( !concurrent_marking_in_progress(), "invariant" ); + guarantee( _finger == _heap_end, "only way to get here" ); + update_g1_committed(true); + } +} + +void ConcurrentMark::set_non_marking_state() { + // We set the global marking state to some default values when we're + // not doing marking. + clear_marking_state(); + _active_tasks = 0; + clear_concurrent_marking_in_progress(); +} + +ConcurrentMark::~ConcurrentMark() { + int size = (int) MAX2(ParallelGCThreads, (size_t)1); + for (int i = 0; i < size; i++) delete _par_cleanup_thread_state[i]; + FREE_C_HEAP_ARRAY(ParCleanupThreadState*, + _par_cleanup_thread_state); + + for (int i = 0; i < (int) _max_task_num; ++i) { + delete _task_queues->queue(i); + delete _tasks[i]; + } + delete _task_queues; + FREE_C_HEAP_ARRAY(CMTask*, _max_task_num); +} + +// This closure is used to mark refs into the g1 generation +// from external roots in the CMS bit map. +// Called at the first checkpoint. +// + +#define PRINT_REACHABLE_AT_INITIAL_MARK 0 +#if PRINT_REACHABLE_AT_INITIAL_MARK +static FILE* reachable_file = NULL; + +class PrintReachableClosure: public OopsInGenClosure { + CMBitMap* _bm; + int _level; +public: + PrintReachableClosure(CMBitMap* bm) : + _bm(bm), _level(0) { + guarantee(reachable_file != NULL, "pre-condition"); + } + void do_oop(oop* p) { + oop obj = *p; + HeapWord* obj_addr = (HeapWord*)obj; + if (obj == NULL) return; + fprintf(reachable_file, "%d: "PTR_FORMAT" -> "PTR_FORMAT" (%d)\n", + _level, p, (void*) obj, _bm->isMarked(obj_addr)); + if (!_bm->isMarked(obj_addr)) { + _bm->mark(obj_addr); + _level++; + obj->oop_iterate(this); + _level--; + } + } +}; +#endif // PRINT_REACHABLE_AT_INITIAL_MARK + +#define SEND_HEAP_DUMP_TO_FILE 0 +#if SEND_HEAP_DUMP_TO_FILE +static FILE* heap_dump_file = NULL; +#endif // SEND_HEAP_DUMP_TO_FILE + +void ConcurrentMark::clearNextBitmap() { + guarantee(!G1CollectedHeap::heap()->mark_in_progress(), "Precondition."); + + // clear the mark bitmap (no grey objects to start with). + // We need to do this in chunks and offer to yield in between + // each chunk. + HeapWord* start = _nextMarkBitMap->startWord(); + HeapWord* end = _nextMarkBitMap->endWord(); + HeapWord* cur = start; + size_t chunkSize = M; + while (cur < end) { + HeapWord* next = cur + chunkSize; + if (next > end) + next = end; + MemRegion mr(cur,next); + _nextMarkBitMap->clearRange(mr); + cur = next; + do_yield_check(); + } +} + +class NoteStartOfMarkHRClosure: public HeapRegionClosure { +public: + bool doHeapRegion(HeapRegion* r) { + if (!r->continuesHumongous()) { + r->note_start_of_marking(true); + } + return false; + } +}; + +void ConcurrentMark::checkpointRootsInitialPre() { + G1CollectedHeap* g1h = G1CollectedHeap::heap(); + G1CollectorPolicy* g1p = g1h->g1_policy(); + + _has_aborted = false; + + // Find all the reachable objects... +#if PRINT_REACHABLE_AT_INITIAL_MARK + guarantee(reachable_file == NULL, "Protocol"); + char fn_buf[100]; + sprintf(fn_buf, "/tmp/reachable.txt.%d", os::current_process_id()); + reachable_file = fopen(fn_buf, "w"); + // clear the mark bitmap (no grey objects to start with) + _nextMarkBitMap->clearAll(); + PrintReachableClosure prcl(_nextMarkBitMap); + g1h->process_strong_roots( + false, // fake perm gen collection + SharedHeap::SO_AllClasses, + &prcl, // Regular roots + &prcl // Perm Gen Roots + ); + // The root iteration above "consumed" dirty cards in the perm gen. + // Therefore, as a shortcut, we dirty all such cards. + g1h->rem_set()->invalidate(g1h->perm_gen()->used_region(), false); + fclose(reachable_file); + reachable_file = NULL; + // clear the mark bitmap again. + _nextMarkBitMap->clearAll(); + COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); + COMPILER2_PRESENT(DerivedPointerTable::clear()); +#endif // PRINT_REACHABLE_AT_INITIAL_MARK + + // Initialise marking structures. This has to be done in a STW phase. + reset(); +} + +class CMMarkRootsClosure: public OopsInGenClosure { +private: + ConcurrentMark* _cm; + G1CollectedHeap* _g1h; + bool _do_barrier; + +public: + CMMarkRootsClosure(ConcurrentMark* cm, + G1CollectedHeap* g1h, + bool do_barrier) : _cm(cm), _g1h(g1h), + _do_barrier(do_barrier) { } + + virtual void do_oop(narrowOop* p) { + guarantee(false, "NYI"); + } + + virtual void do_oop(oop* p) { + oop thisOop = *p; + if (thisOop != NULL) { + assert(thisOop->is_oop() || thisOop->mark() == NULL, + "expected an oop, possibly with mark word displaced"); + HeapWord* addr = (HeapWord*)thisOop; + if (_g1h->is_in_g1_reserved(addr)) { + _cm->grayRoot(thisOop); + } + } + if (_do_barrier) { + assert(!_g1h->is_in_g1_reserved(p), + "Should be called on external roots"); + do_barrier(p); + } + } +}; + +void ConcurrentMark::checkpointRootsInitialPost() { + G1CollectedHeap* g1h = G1CollectedHeap::heap(); + + // For each region note start of marking. + NoteStartOfMarkHRClosure startcl; + g1h->heap_region_iterate(&startcl); + + // Start weak-reference discovery. + ReferenceProcessor* rp = g1h->ref_processor(); + rp->verify_no_references_recorded(); + rp->enable_discovery(); // enable ("weak") refs discovery + + SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); + satb_mq_set.set_process_completed_threshold(G1SATBProcessCompletedThreshold); + satb_mq_set.set_active_all_threads(true); + + // update_g1_committed() will be called at the end of an evac pause + // when marking is on. So, it's also called at the end of the + // initial-mark pause to update the heap end, if the heap expands + // during it. No need to call it here. + + guarantee( !_cleanup_co_tracker.enabled(), "invariant" ); + + size_t max_marking_threads = + MAX2((size_t) 1, parallel_marking_threads()); + for (int i = 0; i < (int)_max_task_num; ++i) { + _tasks[i]->enable_co_tracker(); + if (i < (int) max_marking_threads) + _tasks[i]->reset_co_tracker(marking_task_overhead()); + else + _tasks[i]->reset_co_tracker(0.0); + } +} + +// Checkpoint the roots into this generation from outside +// this generation. [Note this initial checkpoint need only +// be approximate -- we'll do a catch up phase subsequently.] +void ConcurrentMark::checkpointRootsInitial() { + assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped"); + G1CollectedHeap* g1h = G1CollectedHeap::heap(); + + double start = os::elapsedTime(); + GCOverheadReporter::recordSTWStart(start); + + // If there has not been a GC[n-1] since last GC[n] cycle completed, + // precede our marking with a collection of all + // younger generations to keep floating garbage to a minimum. + // YSR: we won't do this for now -- it's an optimization to be + // done post-beta. + + // YSR: ignoring weak refs for now; will do at bug fixing stage + // EVM: assert(discoveredRefsAreClear()); + + + G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy(); + g1p->record_concurrent_mark_init_start(); + checkpointRootsInitialPre(); + + // YSR: when concurrent precleaning is in place, we'll + // need to clear the cached card table here + + ResourceMark rm; + HandleMark hm; + + g1h->ensure_parsability(false); + g1h->perm_gen()->save_marks(); + + CMMarkRootsClosure notOlder(this, g1h, false); + CMMarkRootsClosure older(this, g1h, true); + + g1h->set_marking_started(); + g1h->rem_set()->prepare_for_younger_refs_iterate(false); + + g1h->process_strong_roots(false, // fake perm gen collection + SharedHeap::SO_AllClasses, + ¬Older, // Regular roots + &older // Perm Gen Roots + ); + checkpointRootsInitialPost(); + + // Statistics. + double end = os::elapsedTime(); + _init_times.add((end - start) * 1000.0); + GCOverheadReporter::recordSTWEnd(end); + + g1p->record_concurrent_mark_init_end(); +} + +/* + Notice that in the next two methods, we actually leave the STS + during the barrier sync and join it immediately afterwards. If we + do not do this, this then the following deadlock can occur: one + thread could be in the barrier sync code, waiting for the other + thread to also sync up, whereas another one could be trying to + yield, while also waiting for the other threads to sync up too. + + Because the thread that does the sync barrier has left the STS, it + is possible to be suspended for a Full GC or an evacuation pause + could occur. This is actually safe, since the entering the sync + barrier is one of the last things do_marking_step() does, and it + doesn't manipulate any data structures afterwards. +*/ + +void ConcurrentMark::enter_first_sync_barrier(int task_num) { + if (verbose_low()) + gclog_or_tty->print_cr("[%d] entering first barrier", task_num); + + ConcurrentGCThread::stsLeave(); + _first_overflow_barrier_sync.enter(); + ConcurrentGCThread::stsJoin(); + // at this point everyone should have synced up and not be doing any + // more work + + if (verbose_low()) + gclog_or_tty->print_cr("[%d] leaving first barrier", task_num); + + // let task 0 do this + if (task_num == 0) { + // task 0 is responsible for clearing the global data structures + clear_marking_state(); + + if (PrintGC) { + gclog_or_tty->date_stamp(PrintGCDateStamps); + gclog_or_tty->stamp(PrintGCTimeStamps); + gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]"); + } + } + + // after this, each task should reset its own data structures then + // then go into the second barrier +} + +void ConcurrentMark::enter_second_sync_barrier(int task_num) { + if (verbose_low()) + gclog_or_tty->print_cr("[%d] entering second barrier", task_num); + + ConcurrentGCThread::stsLeave(); + _second_overflow_barrier_sync.enter(); + ConcurrentGCThread::stsJoin(); + // at this point everything should be re-initialised and ready to go + + if (verbose_low()) + gclog_or_tty->print_cr("[%d] leaving second barrier", task_num); +} + +void ConcurrentMark::grayRoot(oop p) { + HeapWord* addr = (HeapWord*) p; + // We can't really check against _heap_start and _heap_end, since it + // is possible during an evacuation pause with piggy-backed + // initial-mark that the committed space is expanded during the + // pause without CM observing this change. So the assertions below + // is a bit conservative; but better than nothing. + tmp_guarantee_CM( _g1h->g1_committed().contains(addr), + "address should be within the heap bounds" ); + + if (!_nextMarkBitMap->isMarked(addr)) + _nextMarkBitMap->parMark(addr); +} + +void ConcurrentMark::grayRegionIfNecessary(MemRegion mr) { + // The objects on the region have already been marked "in bulk" by + // the caller. We only need to decide whether to push the region on + // the region stack or not. + + if (!concurrent_marking_in_progress() || !_should_gray_objects) + // We're done with marking and waiting for remark. We do not need to + // push anything else on the region stack. + return; + + HeapWord* finger = _finger; + + if (verbose_low()) + gclog_or_tty->print_cr("[global] attempting to push " + "region ["PTR_FORMAT", "PTR_FORMAT"), finger is at " + PTR_FORMAT, mr.start(), mr.end(), finger); + + if (mr.start() < finger) { + // The finger is always heap region aligned and it is not possible + // for mr to span heap regions. + tmp_guarantee_CM( mr.end() <= finger, "invariant" ); + + tmp_guarantee_CM( mr.start() <= mr.end() && + _heap_start <= mr.start() && + mr.end() <= _heap_end, + "region boundaries should fall within the committed space" ); + if (verbose_low()) + gclog_or_tty->print_cr("[global] region ["PTR_FORMAT", "PTR_FORMAT") " + "below the finger, pushing it", + mr.start(), mr.end()); + + if (!region_stack_push(mr)) { + if (verbose_low()) + gclog_or_tty->print_cr("[global] region stack has overflown."); + } + } +} + +void ConcurrentMark::markAndGrayObjectIfNecessary(oop p) { + // The object is not marked by the caller. We need to at least mark + // it and maybe push in on the stack. + + HeapWord* addr = (HeapWord*)p; + if (!_nextMarkBitMap->isMarked(addr)) { + // We definitely need to mark it, irrespective whether we bail out + // because we're done with marking. + if (_nextMarkBitMap->parMark(addr)) { + if (!concurrent_marking_in_progress() || !_should_gray_objects) + // If we're done with concurrent marking and we're waiting for + // remark, then we're not pushing anything on the stack. + return; + + // No OrderAccess:store_load() is needed. It is implicit in the + // CAS done in parMark(addr) above + HeapWord* finger = _finger; + + if (addr < finger) { + if (!mark_stack_push(oop(addr))) { + if (verbose_low()) + gclog_or_tty->print_cr("[global] global stack overflow " + "during parMark"); + } + } + } + } +} + +class CMConcurrentMarkingTask: public AbstractGangTask { +private: + ConcurrentMark* _cm; + ConcurrentMarkThread* _cmt; + +public: + void work(int worker_i) { + guarantee( Thread::current()->is_ConcurrentGC_thread(), + "this should only be done by a conc GC thread" ); + + double start_vtime = os::elapsedVTime(); + + ConcurrentGCThread::stsJoin(); + + guarantee( (size_t)worker_i < _cm->active_tasks(), "invariant" ); + CMTask* the_task = _cm->task(worker_i); + the_task->start_co_tracker(); + the_task->record_start_time(); + if (!_cm->has_aborted()) { + do { + double start_vtime_sec = os::elapsedVTime(); + double start_time_sec = os::elapsedTime(); + the_task->do_marking_step(10.0); + double end_time_sec = os::elapsedTime(); + double end_vtime_sec = os::elapsedVTime(); + double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec; + double elapsed_time_sec = end_time_sec - start_time_sec; + _cm->clear_has_overflown(); + + bool ret = _cm->do_yield_check(worker_i); + + jlong sleep_time_ms; + if (!_cm->has_aborted() && the_task->has_aborted()) { + sleep_time_ms = + (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0); + ConcurrentGCThread::stsLeave(); + os::sleep(Thread::current(), sleep_time_ms, false); + ConcurrentGCThread::stsJoin(); + } + double end_time2_sec = os::elapsedTime(); + double elapsed_time2_sec = end_time2_sec - start_time_sec; + + the_task->update_co_tracker(); + +#if 0 + gclog_or_tty->print_cr("CM: elapsed %1.4lf ms, sleep %1.4lf ms, " + "overhead %1.4lf", + elapsed_vtime_sec * 1000.0, (double) sleep_time_ms, + the_task->conc_overhead(os::elapsedTime()) * 8.0); + gclog_or_tty->print_cr("elapsed time %1.4lf ms, time 2: %1.4lf ms", + elapsed_time_sec * 1000.0, elapsed_time2_sec * 1000.0); +#endif + } while (!_cm->has_aborted() && the_task->has_aborted()); + } + the_task->record_end_time(); + guarantee( !the_task->has_aborted() || _cm->has_aborted(), "invariant" ); + + ConcurrentGCThread::stsLeave(); + + double end_vtime = os::elapsedVTime(); + the_task->update_co_tracker(true); + _cm->update_accum_task_vtime(worker_i, end_vtime - start_vtime); + } + + CMConcurrentMarkingTask(ConcurrentMark* cm, + ConcurrentMarkThread* cmt) : + AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { } + + ~CMConcurrentMarkingTask() { } +}; + +void ConcurrentMark::markFromRoots() { + // we might be tempted to assert that: + // assert(asynch == !SafepointSynchronize::is_at_safepoint(), + // "inconsistent argument?"); + // However that wouldn't be right, because it's possible that + // a safepoint is indeed in progress as a younger generation + // stop-the-world GC happens even as we mark in this generation. + + _restart_for_overflow = false; + + set_phase(MAX2((size_t) 1, parallel_marking_threads()), true); + + CMConcurrentMarkingTask markingTask(this, cmThread()); + if (parallel_marking_threads() > 0) + _parallel_workers->run_task(&markingTask); + else + markingTask.work(0); + print_stats(); +} + +void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) { + // world is stopped at this checkpoint + assert(SafepointSynchronize::is_at_safepoint(), + "world should be stopped"); + G1CollectedHeap* g1h = G1CollectedHeap::heap(); + + // If a full collection has happened, we shouldn't do this. + if (has_aborted()) { + g1h->set_marking_complete(); // So bitmap clearing isn't confused + return; + } + + G1CollectorPolicy* g1p = g1h->g1_policy(); + g1p->record_concurrent_mark_remark_start(); + + double start = os::elapsedTime(); + GCOverheadReporter::recordSTWStart(start); + + checkpointRootsFinalWork(); + + double mark_work_end = os::elapsedTime(); + + weakRefsWork(clear_all_soft_refs); + + if (has_overflown()) { + // Oops. We overflowed. Restart concurrent marking. + _restart_for_overflow = true; + // Clear the flag. We do not need it any more. + clear_has_overflown(); + if (G1TraceMarkStackOverflow) + gclog_or_tty->print_cr("\nRemark led to restart for overflow."); + } else { + // We're done with marking. + JavaThread::satb_mark_queue_set().set_active_all_threads(false); + } + +#if VERIFY_OBJS_PROCESSED + _scan_obj_cl.objs_processed = 0; + ThreadLocalObjQueue::objs_enqueued = 0; +#endif + + // Statistics + double now = os::elapsedTime(); + _remark_mark_times.add((mark_work_end - start) * 1000.0); + _remark_weak_ref_times.add((now - mark_work_end) * 1000.0); + _remark_times.add((now - start) * 1000.0); + + GCOverheadReporter::recordSTWEnd(now); + for (int i = 0; i < (int)_max_task_num; ++i) + _tasks[i]->disable_co_tracker(); + _cleanup_co_tracker.enable(); + _cleanup_co_tracker.reset(cleanup_task_overhead()); + g1p->record_concurrent_mark_remark_end(); +} + + +#define CARD_BM_TEST_MODE 0 + +class CalcLiveObjectsClosure: public HeapRegionClosure { + + CMBitMapRO* _bm; + ConcurrentMark* _cm; + COTracker* _co_tracker; + bool _changed; + bool _yield; + size_t _words_done; + size_t _tot_live; + size_t _tot_used; + size_t _regions_done; + double _start_vtime_sec; + + BitMap* _region_bm; + BitMap* _card_bm; + intptr_t _bottom_card_num; + bool _final; + + void mark_card_num_range(intptr_t start_card_num, intptr_t last_card_num) { + for (intptr_t i = start_card_num; i <= last_card_num; i++) { +#if CARD_BM_TEST_MODE + guarantee(_card_bm->at(i - _bottom_card_num), + "Should already be set."); +#else + _card_bm->par_at_put(i - _bottom_card_num, 1); +#endif + } + } + +public: + CalcLiveObjectsClosure(bool final, + CMBitMapRO *bm, ConcurrentMark *cm, + BitMap* region_bm, BitMap* card_bm, + COTracker* co_tracker) : + _bm(bm), _cm(cm), _changed(false), _yield(true), + _words_done(0), _tot_live(0), _tot_used(0), + _region_bm(region_bm), _card_bm(card_bm), + _final(final), _co_tracker(co_tracker), + _regions_done(0), _start_vtime_sec(0.0) + { + _bottom_card_num = + intptr_t(uintptr_t(G1CollectedHeap::heap()->reserved_region().start()) >> + CardTableModRefBS::card_shift); + } + + bool doHeapRegion(HeapRegion* hr) { + if (_co_tracker != NULL) + _co_tracker->update(); + + if (!_final && _regions_done == 0) + _start_vtime_sec = os::elapsedVTime(); + + if (hr->continuesHumongous()) return false; + + HeapWord* nextTop = hr->next_top_at_mark_start(); + HeapWord* start = hr->top_at_conc_mark_count(); + assert(hr->bottom() <= start && start <= hr->end() && + hr->bottom() <= nextTop && nextTop <= hr->end() && + start <= nextTop, + "Preconditions."); + // Otherwise, record the number of word's we'll examine. + size_t words_done = (nextTop - start); + // Find the first marked object at or after "start". + start = _bm->getNextMarkedWordAddress(start, nextTop); + size_t marked_bytes = 0; + + // Below, the term "card num" means the result of shifting an address + // by the card shift -- address 0 corresponds to card number 0. One + // must subtract the card num of the bottom of the heap to obtain a + // card table index. + // The first card num of the sequence of live cards currently being + // constructed. -1 ==> no sequence. + intptr_t start_card_num = -1; + // The last card num of the sequence of live cards currently being + // constructed. -1 ==> no sequence. + intptr_t last_card_num = -1; + + while (start < nextTop) { + if (_yield && _cm->do_yield_check()) { + // We yielded. It might be for a full collection, in which case + // all bets are off; terminate the traversal. + if (_cm->has_aborted()) { + _changed = false; + return true; + } else { + // Otherwise, it might be a collection pause, and the region + // we're looking at might be in the collection set. We'll + // abandon this region. + return false; + } + } + oop obj = oop(start); + int obj_sz = obj->size(); + // The card num of the start of the current object. + intptr_t obj_card_num = + intptr_t(uintptr_t(start) >> CardTableModRefBS::card_shift); + + HeapWord* obj_last = start + obj_sz - 1; + intptr_t obj_last_card_num = + intptr_t(uintptr_t(obj_last) >> CardTableModRefBS::card_shift); + + if (obj_card_num != last_card_num) { + if (start_card_num == -1) { + assert(last_card_num == -1, "Both or neither."); + start_card_num = obj_card_num; + } else { + assert(last_card_num != -1, "Both or neither."); + assert(obj_card_num >= last_card_num, "Inv"); + if ((obj_card_num - last_card_num) > 1) { + // Mark the last run, and start a new one. + mark_card_num_range(start_card_num, last_card_num); + start_card_num = obj_card_num; + } + } +#if CARD_BM_TEST_MODE + /* + gclog_or_tty->print_cr("Setting bits from %d/%d.", + obj_card_num - _bottom_card_num, + obj_last_card_num - _bottom_card_num); + */ + for (intptr_t j = obj_card_num; j <= obj_last_card_num; j++) { + _card_bm->par_at_put(j - _bottom_card_num, 1); + } +#endif + } + // In any case, we set the last card num. + last_card_num = obj_last_card_num; + + marked_bytes += obj_sz * HeapWordSize; + // Find the next marked object after this one. + start = _bm->getNextMarkedWordAddress(start + 1, nextTop); + _changed = true; + } + // Handle the last range, if any. + if (start_card_num != -1) + mark_card_num_range(start_card_num, last_card_num); + if (_final) { + // Mark the allocated-since-marking portion... + HeapWord* tp = hr->top(); + if (nextTop < tp) { + start_card_num = + intptr_t(uintptr_t(nextTop) >> CardTableModRefBS::card_shift); + last_card_num = + intptr_t(uintptr_t(tp) >> CardTableModRefBS::card_shift); + mark_card_num_range(start_card_num, last_card_num); + // This definitely means the region has live objects. + _region_bm->par_at_put(hr->hrs_index(), 1); + } + } + + hr->add_to_marked_bytes(marked_bytes); + // Update the live region bitmap. + if (marked_bytes > 0) { + _region_bm->par_at_put(hr->hrs_index(), 1); + } + hr->set_top_at_conc_mark_count(nextTop); + _tot_live += hr->next_live_bytes(); + _tot_used += hr->used(); + _words_done = words_done; + + if (!_final) { + ++_regions_done; + if (_regions_done % 10 == 0) { + double end_vtime_sec = os::elapsedVTime(); + double elapsed_vtime_sec = end_vtime_sec - _start_vtime_sec; + if (elapsed_vtime_sec > (10.0 / 1000.0)) { + jlong sleep_time_ms = + (jlong) (elapsed_vtime_sec * _cm->cleanup_sleep_factor() * 1000.0); +#if 0 + gclog_or_tty->print_cr("CL: elapsed %1.4lf ms, sleep %1.4lf ms, " + "overhead %1.4lf", + elapsed_vtime_sec * 1000.0, (double) sleep_time_ms, + _co_tracker->concOverhead(os::elapsedTime())); +#endif + os::sleep(Thread::current(), sleep_time_ms, false); + _start_vtime_sec = end_vtime_sec; + } + } + } + + return false; + } + + bool changed() { return _changed; } + void reset() { _changed = false; _words_done = 0; } + void no_yield() { _yield = false; } + size_t words_done() { return _words_done; } + size_t tot_live() { return _tot_live; } + size_t tot_used() { return _tot_used; } +}; + + +void ConcurrentMark::calcDesiredRegions() { + guarantee( _cleanup_co_tracker.enabled(), "invariant" ); + _cleanup_co_tracker.start(); + + _region_bm.clear(); + _card_bm.clear(); + CalcLiveObjectsClosure calccl(false /*final*/, + nextMarkBitMap(), this, + &_region_bm, &_card_bm, + &_cleanup_co_tracker); + G1CollectedHeap *g1h = G1CollectedHeap::heap(); + g1h->heap_region_iterate(&calccl); + + do { + calccl.reset(); + g1h->heap_region_iterate(&calccl); + } while (calccl.changed()); + + _cleanup_co_tracker.update(true); +} + +class G1ParFinalCountTask: public AbstractGangTask { +protected: + G1CollectedHeap* _g1h; + CMBitMap* _bm; + size_t _n_workers; + size_t *_live_bytes; + size_t *_used_bytes; + BitMap* _region_bm; + BitMap* _card_bm; +public: + G1ParFinalCountTask(G1CollectedHeap* g1h, CMBitMap* bm, + BitMap* region_bm, BitMap* card_bm) : + AbstractGangTask("G1 final counting"), _g1h(g1h), + _bm(bm), _region_bm(region_bm), _card_bm(card_bm) + { + if (ParallelGCThreads > 0) + _n_workers = _g1h->workers()->total_workers(); + else + _n_workers = 1; + _live_bytes = NEW_C_HEAP_ARRAY(size_t, _n_workers); + _used_bytes = NEW_C_HEAP_ARRAY(size_t, _n_workers); + } + + ~G1ParFinalCountTask() { + FREE_C_HEAP_ARRAY(size_t, _live_bytes); + FREE_C_HEAP_ARRAY(size_t, _used_bytes); + } + + void work(int i) { + CalcLiveObjectsClosure calccl(true /*final*/, + _bm, _g1h->concurrent_mark(), + _region_bm, _card_bm, + NULL /* CO tracker */); + calccl.no_yield(); + if (ParallelGCThreads > 0) { + _g1h->heap_region_par_iterate_chunked(&calccl, i, 1); + } else { + _g1h->heap_region_iterate(&calccl); + } + assert(calccl.complete(), "Shouldn't have yielded!"); + + guarantee( (size_t)i < _n_workers, "invariant" ); + _live_bytes[i] = calccl.tot_live(); + _used_bytes[i] = calccl.tot_used(); + } + size_t live_bytes() { + size_t live_bytes = 0; + for (size_t i = 0; i < _n_workers; ++i) + live_bytes += _live_bytes[i]; + return live_bytes; + } + size_t used_bytes() { + size_t used_bytes = 0; + for (size_t i = 0; i < _n_workers; ++i) + used_bytes += _used_bytes[i]; + return used_bytes; + } +}; + +class G1ParNoteEndTask; + +class G1NoteEndOfConcMarkClosure : public HeapRegionClosure { + G1CollectedHeap* _g1; + int _worker_num; + size_t _max_live_bytes; + size_t _regions_claimed; + size_t _freed_bytes; + size_t _cleared_h_regions; + size_t _freed_regions; + UncleanRegionList* _unclean_region_list; + double _claimed_region_time; + double _max_region_time; + +public: + G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1, + UncleanRegionList* list, + int worker_num); + size_t freed_bytes() { return _freed_bytes; } + size_t cleared_h_regions() { return _cleared_h_regions; } + size_t freed_regions() { return _freed_regions; } + UncleanRegionList* unclean_region_list() { + return _unclean_region_list; + } + + bool doHeapRegion(HeapRegion *r); + + size_t max_live_bytes() { return _max_live_bytes; } + size_t regions_claimed() { return _regions_claimed; } + double claimed_region_time_sec() { return _claimed_region_time; } + double max_region_time_sec() { return _max_region_time; } +}; + +class G1ParNoteEndTask: public AbstractGangTask { + friend class G1NoteEndOfConcMarkClosure; +protected: + G1CollectedHeap* _g1h; + size_t _max_live_bytes; + size_t _freed_bytes; + ConcurrentMark::ParCleanupThreadState** _par_cleanup_thread_state; +public: + G1ParNoteEndTask(G1CollectedHeap* g1h, + ConcurrentMark::ParCleanupThreadState** + par_cleanup_thread_state) : + AbstractGangTask("G1 note end"), _g1h(g1h), + _max_live_bytes(0), _freed_bytes(0), + _par_cleanup_thread_state(par_cleanup_thread_state) + {} + + void work(int i) { + double start = os::elapsedTime(); + G1NoteEndOfConcMarkClosure g1_note_end(_g1h, + &_par_cleanup_thread_state[i]->list, + i); + if (ParallelGCThreads > 0) { + _g1h->heap_region_par_iterate_chunked(&g1_note_end, i, 2); + } else { + _g1h->heap_region_iterate(&g1_note_end); + } + assert(g1_note_end.complete(), "Shouldn't have yielded!"); + + // Now finish up freeing the current thread's regions. + _g1h->finish_free_region_work(g1_note_end.freed_bytes(), + g1_note_end.cleared_h_regions(), + 0, NULL); + { + MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); + _max_live_bytes += g1_note_end.max_live_bytes(); + _freed_bytes += g1_note_end.freed_bytes(); + } + double end = os::elapsedTime(); + if (G1PrintParCleanupStats) { + gclog_or_tty->print(" Worker thread %d [%8.3f..%8.3f = %8.3f ms] " + "claimed %d regions (tot = %8.3f ms, max = %8.3f ms).\n", + i, start, end, (end-start)*1000.0, + g1_note_end.regions_claimed(), + g1_note_end.claimed_region_time_sec()*1000.0, + g1_note_end.max_region_time_sec()*1000.0); + } + } + size_t max_live_bytes() { return _max_live_bytes; } + size_t freed_bytes() { return _freed_bytes; } +}; + +class G1ParScrubRemSetTask: public AbstractGangTask { +protected: + G1RemSet* _g1rs; + BitMap* _region_bm; + BitMap* _card_bm; +public: + G1ParScrubRemSetTask(G1CollectedHeap* g1h, + BitMap* region_bm, BitMap* card_bm) : + AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()), + _region_bm(region_bm), _card_bm(card_bm) + {} + + void work(int i) { + if (ParallelGCThreads > 0) { + _g1rs->scrub_par(_region_bm, _card_bm, i, 3); + } else { + _g1rs->scrub(_region_bm, _card_bm); + } + } + +}; + +G1NoteEndOfConcMarkClosure:: +G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1, + UncleanRegionList* list, + int worker_num) + : _g1(g1), _worker_num(worker_num), + _max_live_bytes(0), _regions_claimed(0), + _freed_bytes(0), _cleared_h_regions(0), _freed_regions(0), + _claimed_region_time(0.0), _max_region_time(0.0), + _unclean_region_list(list) +{} + +bool G1NoteEndOfConcMarkClosure::doHeapRegion(HeapRegion *r) { + // We use a claim value of zero here because all regions + // were claimed with value 1 in the FinalCount task. + r->reset_gc_time_stamp(); + if (!r->continuesHumongous()) { + double start = os::elapsedTime(); + _regions_claimed++; + r->note_end_of_marking(); + _max_live_bytes += r->max_live_bytes(); + _g1->free_region_if_totally_empty_work(r, + _freed_bytes, + _cleared_h_regions, + _freed_regions, + _unclean_region_list, + true /*par*/); + double region_time = (os::elapsedTime() - start); + _claimed_region_time += region_time; + if (region_time > _max_region_time) _max_region_time = region_time; + } + return false; +} + +void ConcurrentMark::cleanup() { + // world is stopped at this checkpoint + assert(SafepointSynchronize::is_at_safepoint(), + "world should be stopped"); + G1CollectedHeap* g1h = G1CollectedHeap::heap(); + + // If a full collection has happened, we shouldn't do this. + if (has_aborted()) { + g1h->set_marking_complete(); // So bitmap clearing isn't confused + return; + } + + _cleanup_co_tracker.disable(); + + G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy(); + g1p->record_concurrent_mark_cleanup_start(); + + double start = os::elapsedTime(); + GCOverheadReporter::recordSTWStart(start); + + // Do counting once more with the world stopped for good measure. + G1ParFinalCountTask g1_par_count_task(g1h, nextMarkBitMap(), + &_region_bm, &_card_bm); + if (ParallelGCThreads > 0) { + int n_workers = g1h->workers()->total_workers(); + g1h->set_par_threads(n_workers); + g1h->workers()->run_task(&g1_par_count_task); + g1h->set_par_threads(0); + } else { + g1_par_count_task.work(0); + } + + size_t known_garbage_bytes = + g1_par_count_task.used_bytes() - g1_par_count_task.live_bytes(); +#if 0 + gclog_or_tty->print_cr("used %1.2lf, live %1.2lf, garbage %1.2lf", + (double) g1_par_count_task.used_bytes() / (double) (1024 * 1024), + (double) g1_par_count_task.live_bytes() / (double) (1024 * 1024), + (double) known_garbage_bytes / (double) (1024 * 1024)); +#endif // 0 + g1p->set_known_garbage_bytes(known_garbage_bytes); + + size_t start_used_bytes = g1h->used(); + _at_least_one_mark_complete = true; + g1h->set_marking_complete(); + + double count_end = os::elapsedTime(); + double this_final_counting_time = (count_end - start); + if (G1PrintParCleanupStats) { + gclog_or_tty->print_cr("Cleanup:"); + gclog_or_tty->print_cr(" Finalize counting: %8.3f ms", + this_final_counting_time*1000.0); + } + _total_counting_time += this_final_counting_time; + + // Install newly created mark bitMap as "prev". + swapMarkBitMaps(); + + g1h->reset_gc_time_stamp(); + + // Note end of marking in all heap regions. + double note_end_start = os::elapsedTime(); + G1ParNoteEndTask g1_par_note_end_task(g1h, _par_cleanup_thread_state); + if (ParallelGCThreads > 0) { + int n_workers = g1h->workers()->total_workers(); + g1h->set_par_threads(n_workers); + g1h->workers()->run_task(&g1_par_note_end_task); + g1h->set_par_threads(0); + } else { + g1_par_note_end_task.work(0); + } + g1h->set_unclean_regions_coming(true); + double note_end_end = os::elapsedTime(); + // Tell the mutators that there might be unclean regions coming... + if (G1PrintParCleanupStats) { + gclog_or_tty->print_cr(" note end of marking: %8.3f ms.", + (note_end_end - note_end_start)*1000.0); + } + + // Now we "scrub" remembered sets. Note that we must do this before the + // call below, since it affects the metric by which we sort the heap + // regions. + if (G1ScrubRemSets) { + double rs_scrub_start = os::elapsedTime(); + G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm); + if (ParallelGCThreads > 0) { + int n_workers = g1h->workers()->total_workers(); + g1h->set_par_threads(n_workers); + g1h->workers()->run_task(&g1_par_scrub_rs_task); + g1h->set_par_threads(0); + } else { + g1_par_scrub_rs_task.work(0); + } + + double rs_scrub_end = os::elapsedTime(); + double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start); + _total_rs_scrub_time += this_rs_scrub_time; + } + + // this will also free any regions totally full of garbage objects, + // and sort the regions. + g1h->g1_policy()->record_concurrent_mark_cleanup_end( + g1_par_note_end_task.freed_bytes(), + g1_par_note_end_task.max_live_bytes()); + + // Statistics. + double end = os::elapsedTime(); + _cleanup_times.add((end - start) * 1000.0); + GCOverheadReporter::recordSTWEnd(end); + + // G1CollectedHeap::heap()->print(); + // gclog_or_tty->print_cr("HEAP GC TIME STAMP : %d", + // G1CollectedHeap::heap()->get_gc_time_stamp()); + + if (PrintGC || PrintGCDetails) { + g1h->print_size_transition(gclog_or_tty, + start_used_bytes, + g1h->used(), + g1h->capacity()); + } + + size_t cleaned_up_bytes = start_used_bytes - g1h->used(); + g1p->decrease_known_garbage_bytes(cleaned_up_bytes); + + // We need to make this be a "collection" so any collection pause that + // races with it goes around and waits for completeCleanup to finish. + g1h->increment_total_collections(); + +#ifndef PRODUCT + if (G1VerifyConcMark) { + G1CollectedHeap::heap()->prepare_for_verify(); + G1CollectedHeap::heap()->verify(true,false); + } +#endif +} + +void ConcurrentMark::completeCleanup() { + // A full collection intervened. + if (has_aborted()) return; + + int first = 0; + int last = (int)MAX2(ParallelGCThreads, (size_t)1); + for (int t = 0; t < last; t++) { + UncleanRegionList* list = &_par_cleanup_thread_state[t]->list; + assert(list->well_formed(), "Inv"); + HeapRegion* hd = list->hd(); + while (hd != NULL) { + // Now finish up the other stuff. + hd->rem_set()->clear(); + HeapRegion* next_hd = hd->next_from_unclean_list(); + (void)list->pop(); + guarantee(list->hd() == next_hd, "how not?"); + _g1h->put_region_on_unclean_list(hd); + if (!hd->isHumongous()) { + // Add this to the _free_regions count by 1. + _g1h->finish_free_region_work(0, 0, 1, NULL); + } + hd = list->hd(); + guarantee(hd == next_hd, "how not?"); + } + } +} + + +class G1CMIsAliveClosure: public BoolObjectClosure { + G1CollectedHeap* _g1; + public: + G1CMIsAliveClosure(G1CollectedHeap* g1) : + _g1(g1) + {} + + void do_object(oop obj) { + assert(false, "not to be invoked"); + } + bool do_object_b(oop obj) { + HeapWord* addr = (HeapWord*)obj; + return addr != NULL && + (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj)); + } +}; + +class G1CMKeepAliveClosure: public OopClosure { + G1CollectedHeap* _g1; + ConcurrentMark* _cm; + CMBitMap* _bitMap; + public: + G1CMKeepAliveClosure(G1CollectedHeap* g1, ConcurrentMark* cm, + CMBitMap* bitMap) : + _g1(g1), _cm(cm), + _bitMap(bitMap) {} + + void do_oop(narrowOop* p) { + guarantee(false, "NYI"); + } + + void do_oop(oop* p) { + oop thisOop = *p; + HeapWord* addr = (HeapWord*)thisOop; + if (_g1->is_in_g1_reserved(addr) && _g1->is_obj_ill(thisOop)) { + _bitMap->mark(addr); + _cm->mark_stack_push(thisOop); + } + } +}; + +class G1CMDrainMarkingStackClosure: public VoidClosure { + CMMarkStack* _markStack; + CMBitMap* _bitMap; + G1CMKeepAliveClosure* _oopClosure; + public: + G1CMDrainMarkingStackClosure(CMBitMap* bitMap, CMMarkStack* markStack, + G1CMKeepAliveClosure* oopClosure) : + _bitMap(bitMap), + _markStack(markStack), + _oopClosure(oopClosure) + {} + + void do_void() { + _markStack->drain((OopClosure*)_oopClosure, _bitMap, false); + } +}; + +void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) { + ResourceMark rm; + HandleMark hm; + ReferencePolicy* soft_ref_policy; + + // Process weak references. + if (clear_all_soft_refs) { + soft_ref_policy = new AlwaysClearPolicy(); + } else { +#ifdef COMPILER2 + soft_ref_policy = new LRUMaxHeapPolicy(); +#else + soft_ref_policy = new LRUCurrentHeapPolicy(); +#endif + } + assert(_markStack.isEmpty(), "mark stack should be empty"); + + G1CollectedHeap* g1 = G1CollectedHeap::heap(); + G1CMIsAliveClosure g1IsAliveClosure(g1); + + G1CMKeepAliveClosure g1KeepAliveClosure(g1, this, nextMarkBitMap()); + G1CMDrainMarkingStackClosure + g1DrainMarkingStackClosure(nextMarkBitMap(), &_markStack, + &g1KeepAliveClosure); + + // XXXYYY Also: copy the parallel ref processing code from CMS. + ReferenceProcessor* rp = g1->ref_processor(); + rp->process_discovered_references(soft_ref_policy, + &g1IsAliveClosure, + &g1KeepAliveClosure, + &g1DrainMarkingStackClosure, + NULL); + assert(_markStack.overflow() || _markStack.isEmpty(), + "mark stack should be empty (unless it overflowed)"); + if (_markStack.overflow()) { + set_has_overflown(); + } + + rp->enqueue_discovered_references(); + rp->verify_no_references_recorded(); + assert(!rp->discovery_enabled(), "should have been disabled"); + + // Now clean up stale oops in SymbolTable and StringTable + SymbolTable::unlink(&g1IsAliveClosure); + StringTable::unlink(&g1IsAliveClosure); +} + +void ConcurrentMark::swapMarkBitMaps() { + CMBitMapRO* temp = _prevMarkBitMap; + _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap; + _nextMarkBitMap = (CMBitMap*) temp; +} + +class CMRemarkTask: public AbstractGangTask { +private: + ConcurrentMark *_cm; + +public: + void work(int worker_i) { + // Since all available tasks are actually started, we should + // only proceed if we're supposed to be actived. + if ((size_t)worker_i < _cm->active_tasks()) { + CMTask* task = _cm->task(worker_i); + task->record_start_time(); + do { + task->do_marking_step(1000000000.0 /* something very large */); + } while (task->has_aborted() && !_cm->has_overflown()); + // If we overflow, then we do not want to restart. We instead + // want to abort remark and do concurrent marking again. + task->record_end_time(); + } + } + + CMRemarkTask(ConcurrentMark* cm) : + AbstractGangTask("Par Remark"), _cm(cm) { } +}; + +void ConcurrentMark::checkpointRootsFinalWork() { + ResourceMark rm; + HandleMark hm; + G1CollectedHeap* g1h = G1CollectedHeap::heap(); + + g1h->ensure_parsability(false); + + if (ParallelGCThreads > 0) { + g1h->change_strong_roots_parity(); + // this is remark, so we'll use up all available threads + int active_workers = ParallelGCThreads; + set_phase(active_workers, false); + + CMRemarkTask remarkTask(this); + // We will start all available threads, even if we decide that the + // active_workers will be fewer. The extra ones will just bail out + // immediately. + int n_workers = g1h->workers()->total_workers(); + g1h->set_par_threads(n_workers); + g1h->workers()->run_task(&remarkTask); + g1h->set_par_threads(0); + + SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); + guarantee( satb_mq_set.completed_buffers_num() == 0, "invariant" ); + } else { + g1h->change_strong_roots_parity(); + // this is remark, so we'll use up all available threads + int active_workers = 1; + set_phase(active_workers, false); + + CMRemarkTask remarkTask(this); + // We will start all available threads, even if we decide that the + // active_workers will be fewer. The extra ones will just bail out + // immediately. + remarkTask.work(0); + + SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); + guarantee( satb_mq_set.completed_buffers_num() == 0, "invariant" ); + } + + print_stats(); + + if (!restart_for_overflow()) + set_non_marking_state(); + +#if VERIFY_OBJS_PROCESSED + if (_scan_obj_cl.objs_processed != ThreadLocalObjQueue::objs_enqueued) { + gclog_or_tty->print_cr("Processed = %d, enqueued = %d.", + _scan_obj_cl.objs_processed, + ThreadLocalObjQueue::objs_enqueued); + guarantee(_scan_obj_cl.objs_processed == + ThreadLocalObjQueue::objs_enqueued, + "Different number of objs processed and enqueued."); + } +#endif +} + +class ReachablePrinterOopClosure: public OopClosure { +private: + G1CollectedHeap* _g1h; + CMBitMapRO* _bitmap; + outputStream* _out; + +public: + ReachablePrinterOopClosure(CMBitMapRO* bitmap, outputStream* out) : + _bitmap(bitmap), _g1h(G1CollectedHeap::heap()), _out(out) { } + + void do_oop(narrowOop* p) { + guarantee(false, "NYI"); + } + + void do_oop(oop* p) { + oop obj = *p; + const char* str = NULL; + const char* str2 = ""; + + if (!_g1h->is_in_g1_reserved(obj)) + str = "outside G1 reserved"; + else { + HeapRegion* hr = _g1h->heap_region_containing(obj); + guarantee( hr != NULL, "invariant" ); + if (hr->obj_allocated_since_prev_marking(obj)) { + str = "over TAMS"; + if (_bitmap->isMarked((HeapWord*) obj)) + str2 = " AND MARKED"; + } else if (_bitmap->isMarked((HeapWord*) obj)) + str = "marked"; + else + str = "#### NOT MARKED ####"; + } + + _out->print_cr(" "PTR_FORMAT" contains "PTR_FORMAT" %s%s", + p, (void*) obj, str, str2); + } +}; + +class ReachablePrinterClosure: public BitMapClosure { +private: + CMBitMapRO* _bitmap; + outputStream* _out; + +public: + ReachablePrinterClosure(CMBitMapRO* bitmap, outputStream* out) : + _bitmap(bitmap), _out(out) { } + + bool do_bit(size_t offset) { + HeapWord* addr = _bitmap->offsetToHeapWord(offset); + ReachablePrinterOopClosure oopCl(_bitmap, _out); + + _out->print_cr(" obj "PTR_FORMAT", offset %10d (marked)", addr, offset); + oop(addr)->oop_iterate(&oopCl); + _out->print_cr(""); + + return true; + } +}; + +class ObjInRegionReachablePrinterClosure : public ObjectClosure { +private: + CMBitMapRO* _bitmap; + outputStream* _out; + +public: + void do_object(oop o) { + ReachablePrinterOopClosure oopCl(_bitmap, _out); + + _out->print_cr(" obj "PTR_FORMAT" (over TAMS)", (void*) o); + o->oop_iterate(&oopCl); + _out->print_cr(""); + } + + ObjInRegionReachablePrinterClosure(CMBitMapRO* bitmap, outputStream* out) : + _bitmap(bitmap), _out(out) { } +}; + +class RegionReachablePrinterClosure : public HeapRegionClosure { +private: + CMBitMapRO* _bitmap; + outputStream* _out; + +public: + bool doHeapRegion(HeapRegion* hr) { + HeapWord* b = hr->bottom(); + HeapWord* e = hr->end(); + HeapWord* t = hr->top(); + HeapWord* p = hr->prev_top_at_mark_start(); + _out->print_cr("** ["PTR_FORMAT", "PTR_FORMAT"] top: "PTR_FORMAT" " + "PTAMS: "PTR_FORMAT, b, e, t, p); + _out->print_cr(""); + + ObjInRegionReachablePrinterClosure ocl(_bitmap, _out); + hr->object_iterate_mem_careful(MemRegion(p, t), &ocl); + + return false; + } + + RegionReachablePrinterClosure(CMBitMapRO* bitmap, + outputStream* out) : + _bitmap(bitmap), _out(out) { } +}; + +void ConcurrentMark::print_prev_bitmap_reachable() { + outputStream* out = gclog_or_tty; + +#if SEND_HEAP_DUMP_TO_FILE + guarantee(heap_dump_file == NULL, "Protocol"); + char fn_buf[100]; + sprintf(fn_buf, "/tmp/dump.txt.%d", os::current_process_id()); + heap_dump_file = fopen(fn_buf, "w"); + fileStream fstream(heap_dump_file); + out = &fstream; +#endif // SEND_HEAP_DUMP_TO_FILE + + RegionReachablePrinterClosure rcl(_prevMarkBitMap, out); + out->print_cr("--- ITERATING OVER REGIONS WITH PTAMS < TOP"); + _g1h->heap_region_iterate(&rcl); + out->print_cr(""); + + ReachablePrinterClosure cl(_prevMarkBitMap, out); + out->print_cr("--- REACHABLE OBJECTS ON THE BITMAP"); + _prevMarkBitMap->iterate(&cl); + out->print_cr(""); + +#if SEND_HEAP_DUMP_TO_FILE + fclose(heap_dump_file); + heap_dump_file = NULL; +#endif // SEND_HEAP_DUMP_TO_FILE +} + +// This note is for drainAllSATBBuffers and the code in between. +// In the future we could reuse a task to do this work during an +// evacuation pause (since now tasks are not active and can be claimed +// during an evacuation pause). This was a late change to the code and +// is currently not being taken advantage of. + +class CMGlobalObjectClosure : public ObjectClosure { +private: + ConcurrentMark* _cm; + +public: + void do_object(oop obj) { + _cm->deal_with_reference(obj); + } + + CMGlobalObjectClosure(ConcurrentMark* cm) : _cm(cm) { } +}; + +void ConcurrentMark::deal_with_reference(oop obj) { + if (verbose_high()) + gclog_or_tty->print_cr("[global] we're dealing with reference "PTR_FORMAT, + (void*) obj); + + + HeapWord* objAddr = (HeapWord*) obj; + if (_g1h->is_in_g1_reserved(objAddr)) { + tmp_guarantee_CM( obj != NULL, "is_in_g1_reserved should ensure this" ); + HeapRegion* hr = _g1h->heap_region_containing(obj); + if (_g1h->is_obj_ill(obj, hr)) { + if (verbose_high()) + gclog_or_tty->print_cr("[global] "PTR_FORMAT" is not considered " + "marked", (void*) obj); + + // we need to mark it first + if (_nextMarkBitMap->parMark(objAddr)) { + // No OrderAccess:store_load() is needed. It is implicit in the + // CAS done in parMark(objAddr) above + HeapWord* finger = _finger; + if (objAddr < finger) { + if (verbose_high()) + gclog_or_tty->print_cr("[global] below the global finger " + "("PTR_FORMAT"), pushing it", finger); + if (!mark_stack_push(obj)) { + if (verbose_low()) + gclog_or_tty->print_cr("[global] global stack overflow during " + "deal_with_reference"); + } + } + } + } + } +} + +void ConcurrentMark::drainAllSATBBuffers() { + CMGlobalObjectClosure oc(this); + SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); + satb_mq_set.set_closure(&oc); + + while (satb_mq_set.apply_closure_to_completed_buffer()) { + if (verbose_medium()) + gclog_or_tty->print_cr("[global] processed an SATB buffer"); + } + + // no need to check whether we should do this, as this is only + // called during an evacuation pause + satb_mq_set.iterate_closure_all_threads(); + + satb_mq_set.set_closure(NULL); + guarantee( satb_mq_set.completed_buffers_num() == 0, "invariant" ); +} + +void ConcurrentMark::markPrev(oop p) { + // Note we are overriding the read-only view of the prev map here, via + // the cast. + ((CMBitMap*)_prevMarkBitMap)->mark((HeapWord*)p); +} + +void ConcurrentMark::clear(oop p) { + assert(p != NULL && p->is_oop(), "expected an oop"); + HeapWord* addr = (HeapWord*)p; + assert(addr >= _nextMarkBitMap->startWord() || + addr < _nextMarkBitMap->endWord(), "in a region"); + + _nextMarkBitMap->clear(addr); +} + +void ConcurrentMark::clearRangeBothMaps(MemRegion mr) { + // Note we are overriding the read-only view of the prev map here, via + // the cast. + ((CMBitMap*)_prevMarkBitMap)->clearRange(mr); + _nextMarkBitMap->clearRange(mr); +} + +HeapRegion* +ConcurrentMark::claim_region(int task_num) { + // "checkpoint" the finger + HeapWord* finger = _finger; + + // _heap_end will not change underneath our feet; it only changes at + // yield points. + while (finger < _heap_end) { + tmp_guarantee_CM( _g1h->is_in_g1_reserved(finger), "invariant" ); + + // is the gap between reading the finger and doing the CAS too long? + + HeapRegion* curr_region = _g1h->heap_region_containing(finger); + HeapWord* bottom = curr_region->bottom(); + HeapWord* end = curr_region->end(); + HeapWord* limit = curr_region->next_top_at_mark_start(); + + if (verbose_low()) + gclog_or_tty->print_cr("[%d] curr_region = "PTR_FORMAT" " + "["PTR_FORMAT", "PTR_FORMAT"), " + "limit = "PTR_FORMAT, + task_num, curr_region, bottom, end, limit); + + HeapWord* res = + (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger); + if (res == finger) { + // we succeeded + + // notice that _finger == end cannot be guaranteed here since, + // someone else might have moved the finger even further + guarantee( _finger >= end, "the finger should have moved forward" ); + + if (verbose_low()) + gclog_or_tty->print_cr("[%d] we were successful with region = " + PTR_FORMAT, task_num, curr_region); + + if (limit > bottom) { + if (verbose_low()) + gclog_or_tty->print_cr("[%d] region "PTR_FORMAT" is not empty, " + "returning it ", task_num, curr_region); + return curr_region; + } else { + tmp_guarantee_CM( limit == bottom, + "the region limit should be at bottom" ); + if (verbose_low()) + gclog_or_tty->print_cr("[%d] region "PTR_FORMAT" is empty, " + "returning NULL", task_num, curr_region); + // we return NULL and the caller should try calling + // claim_region() again. + return NULL; + } + } else { + guarantee( _finger > finger, "the finger should have moved forward" ); + if (verbose_low()) + gclog_or_tty->print_cr("[%d] somebody else moved the finger, " + "global finger = "PTR_FORMAT", " + "our finger = "PTR_FORMAT, + task_num, _finger, finger); + + // read it again + finger = _finger; + } + } + + return NULL; +} + +void ConcurrentMark::oops_do(OopClosure* cl) { + if (_markStack.size() > 0 && verbose_low()) + gclog_or_tty->print_cr("[global] scanning the global marking stack, " + "size = %d", _markStack.size()); + // we first iterate over the contents of the mark stack... + _markStack.oops_do(cl); + + for (int i = 0; i < (int)_max_task_num; ++i) { + OopTaskQueue* queue = _task_queues->queue((int)i); + + if (queue->size() > 0 && verbose_low()) + gclog_or_tty->print_cr("[global] scanning task queue of task %d, " + "size = %d", i, queue->size()); + + // ...then over the contents of the all the task queues. + queue->oops_do(cl); + } + + // finally, invalidate any entries that in the region stack that + // point into the collection set + if (_regionStack.invalidate_entries_into_cset()) { + // otherwise, any gray objects copied during the evacuation pause + // might not be visited. + guarantee( _should_gray_objects, "invariant" ); + } +} + +void ConcurrentMark::clear_marking_state() { + _markStack.setEmpty(); + _markStack.clear_overflow(); + _regionStack.setEmpty(); + _regionStack.clear_overflow(); + clear_has_overflown(); + _finger = _heap_start; + + for (int i = 0; i < (int)_max_task_num; ++i) { + OopTaskQueue* queue = _task_queues->queue(i); + queue->set_empty(); + } +} + +void ConcurrentMark::print_stats() { + if (verbose_stats()) { + gclog_or_tty->print_cr("---------------------------------------------------------------------"); + for (size_t i = 0; i < _active_tasks; ++i) { + _tasks[i]->print_stats(); + gclog_or_tty->print_cr("---------------------------------------------------------------------"); + } + } +} + +class CSMarkOopClosure: public OopClosure { + friend class CSMarkBitMapClosure; + + G1CollectedHeap* _g1h; + CMBitMap* _bm; + ConcurrentMark* _cm; + oop* _ms; + jint* _array_ind_stack; + int _ms_size; + int _ms_ind; + int _array_increment; + + bool push(oop obj, int arr_ind = 0) { + if (_ms_ind == _ms_size) { + gclog_or_tty->print_cr("Mark stack is full."); + return false; + } + _ms[_ms_ind] = obj; + if (obj->is_objArray()) _array_ind_stack[_ms_ind] = arr_ind; + _ms_ind++; + return true; + } + + oop pop() { + if (_ms_ind == 0) return NULL; + else { + _ms_ind--; + return _ms[_ms_ind]; + } + } + + bool drain() { + while (_ms_ind > 0) { + oop obj = pop(); + assert(obj != NULL, "Since index was non-zero."); + if (obj->is_objArray()) { + jint arr_ind = _array_ind_stack[_ms_ind]; + objArrayOop aobj = objArrayOop(obj); + jint len = aobj->length(); + jint next_arr_ind = arr_ind + _array_increment; + if (next_arr_ind < len) { + push(obj, next_arr_ind); + } + // Now process this portion of this one. + int lim = MIN2(next_arr_ind, len); + assert(!UseCompressedOops, "This needs to be fixed"); + for (int j = arr_ind; j < lim; j++) { + do_oop(aobj->obj_at_addr(j)); + } + + } else { + obj->oop_iterate(this); + } + if (abort()) return false; + } + return true; + } + +public: + CSMarkOopClosure(ConcurrentMark* cm, int ms_size) : + _g1h(G1CollectedHeap::heap()), + _cm(cm), + _bm(cm->nextMarkBitMap()), + _ms_size(ms_size), _ms_ind(0), + _ms(NEW_C_HEAP_ARRAY(oop, ms_size)), + _array_ind_stack(NEW_C_HEAP_ARRAY(jint, ms_size)), + _array_increment(MAX2(ms_size/8, 16)) + {} + + ~CSMarkOopClosure() { + FREE_C_HEAP_ARRAY(oop, _ms); + FREE_C_HEAP_ARRAY(jint, _array_ind_stack); + } + + void do_oop(narrowOop* p) { + guarantee(false, "NYI"); + } + + void do_oop(oop* p) { + oop obj = *p; + if (obj == NULL) return; + if (obj->is_forwarded()) { + // If the object has already been forwarded, we have to make sure + // that it's marked. So follow the forwarding pointer. Note that + // this does the right thing for self-forwarding pointers in the + // evacuation failure case. + obj = obj->forwardee(); + } + HeapRegion* hr = _g1h->heap_region_containing(obj); + if (hr != NULL) { + if (hr->in_collection_set()) { + if (_g1h->is_obj_ill(obj)) { + _bm->mark((HeapWord*)obj); + if (!push(obj)) { + gclog_or_tty->print_cr("Setting abort in CSMarkOopClosure because push failed."); + set_abort(); + } + } + } else { + // Outside the collection set; we need to gray it + _cm->deal_with_reference(obj); + } + } + } +}; + +class CSMarkBitMapClosure: public BitMapClosure { + G1CollectedHeap* _g1h; + CMBitMap* _bitMap; + ConcurrentMark* _cm; + CSMarkOopClosure _oop_cl; +public: + CSMarkBitMapClosure(ConcurrentMark* cm, int ms_size) : + _g1h(G1CollectedHeap::heap()), + _bitMap(cm->nextMarkBitMap()), + _oop_cl(cm, ms_size) + {} + + ~CSMarkBitMapClosure() {} + + bool do_bit(size_t offset) { + // convert offset into a HeapWord* + HeapWord* addr = _bitMap->offsetToHeapWord(offset); + assert(_bitMap->endWord() && addr < _bitMap->endWord(), + "address out of range"); + assert(_bitMap->isMarked(addr), "tautology"); + oop obj = oop(addr); + if (!obj->is_forwarded()) { + if (!_oop_cl.push(obj)) return false; + if (!_oop_cl.drain()) return false; + } + // Otherwise... + return true; + } +}; + + +class CompleteMarkingInCSHRClosure: public HeapRegionClosure { + CMBitMap* _bm; + CSMarkBitMapClosure _bit_cl; + enum SomePrivateConstants { + MSSize = 1000 + }; + bool _completed; +public: + CompleteMarkingInCSHRClosure(ConcurrentMark* cm) : + _bm(cm->nextMarkBitMap()), + _bit_cl(cm, MSSize), + _completed(true) + {} + + ~CompleteMarkingInCSHRClosure() {} + + bool doHeapRegion(HeapRegion* r) { + if (!r->evacuation_failed()) { + MemRegion mr = MemRegion(r->bottom(), r->next_top_at_mark_start()); + if (!mr.is_empty()) { + if (!_bm->iterate(&_bit_cl, mr)) { + _completed = false; + return true; + } + } + } + return false; + } + + bool completed() { return _completed; } +}; + +class ClearMarksInHRClosure: public HeapRegionClosure { + CMBitMap* _bm; +public: + ClearMarksInHRClosure(CMBitMap* bm): _bm(bm) { } + + bool doHeapRegion(HeapRegion* r) { + if (!r->used_region().is_empty() && !r->evacuation_failed()) { + MemRegion usedMR = r->used_region(); + _bm->clearRange(r->used_region()); + } + return false; + } +}; + +void ConcurrentMark::complete_marking_in_collection_set() { + G1CollectedHeap* g1h = G1CollectedHeap::heap(); + + if (!g1h->mark_in_progress()) { + g1h->g1_policy()->record_mark_closure_time(0.0); + return; + } + + int i = 1; + double start = os::elapsedTime(); + while (true) { + i++; + CompleteMarkingInCSHRClosure cmplt(this); + g1h->collection_set_iterate(&cmplt); + if (cmplt.completed()) break; + } + double end_time = os::elapsedTime(); + double elapsed_time_ms = (end_time - start) * 1000.0; + g1h->g1_policy()->record_mark_closure_time(elapsed_time_ms); + if (PrintGCDetails) { + gclog_or_tty->print_cr("Mark closure took %5.2f ms.", elapsed_time_ms); + } + + ClearMarksInHRClosure clr(nextMarkBitMap()); + g1h->collection_set_iterate(&clr); +} + +// The next two methods deal with the following optimisation. Some +// objects are gray by being marked and located above the finger. If +// they are copied, during an evacuation pause, below the finger then +// the need to be pushed on the stack. The observation is that, if +// there are no regions in the collection set located above the +// finger, then the above cannot happen, hence we do not need to +// explicitly gray any objects when copying them to below the +// finger. The global stack will be scanned to ensure that, if it +// points to objects being copied, it will update their +// location. There is a tricky situation with the gray objects in +// region stack that are being coped, however. See the comment in +// newCSet(). + +void ConcurrentMark::newCSet() { + if (!concurrent_marking_in_progress()) + // nothing to do if marking is not in progress + return; + + // find what the lowest finger is among the global and local fingers + _min_finger = _finger; + for (int i = 0; i < (int)_max_task_num; ++i) { + CMTask* task = _tasks[i]; + HeapWord* task_finger = task->finger(); + if (task_finger != NULL && task_finger < _min_finger) + _min_finger = task_finger; + } + + _should_gray_objects = false; + + // This fixes a very subtle and fustrating bug. It might be the case + // that, during en evacuation pause, heap regions that contain + // objects that are gray (by being in regions contained in the + // region stack) are included in the collection set. Since such gray + // objects will be moved, and because it's not easy to redirect + // region stack entries to point to a new location (because objects + // in one region might be scattered to multiple regions after they + // are copied), one option is to ensure that all marked objects + // copied during a pause are pushed on the stack. Notice, however, + // that this problem can only happen when the region stack is not + // empty during an evacuation pause. So, we make the fix a bit less + // conservative and ensure that regions are pushed on the stack, + // irrespective whether all collection set regions are below the + // finger, if the region stack is not empty. This is expected to be + // a rare case, so I don't think it's necessary to be smarted about it. + if (!region_stack_empty()) + _should_gray_objects = true; +} + +void ConcurrentMark::registerCSetRegion(HeapRegion* hr) { + if (!concurrent_marking_in_progress()) + return; + + HeapWord* region_end = hr->end(); + if (region_end > _min_finger) + _should_gray_objects = true; +} + +void ConcurrentMark::disable_co_trackers() { + if (has_aborted()) { + if (_cleanup_co_tracker.enabled()) + _cleanup_co_tracker.disable(); + for (int i = 0; i < (int)_max_task_num; ++i) { + CMTask* task = _tasks[i]; + if (task->co_tracker_enabled()) + task->disable_co_tracker(); + } + } else { + guarantee( !_cleanup_co_tracker.enabled(), "invariant" ); + for (int i = 0; i < (int)_max_task_num; ++i) { + CMTask* task = _tasks[i]; + guarantee( !task->co_tracker_enabled(), "invariant" ); + } + } +} + +// abandon current marking iteration due to a Full GC +void ConcurrentMark::abort() { + // If we're not marking, nothing to do. + if (!G1ConcMark) return; + + // Clear all marks to force marking thread to do nothing + _nextMarkBitMap->clearAll(); + // Empty mark stack + clear_marking_state(); + for (int i = 0; i < (int)_max_task_num; ++i) + _tasks[i]->clear_region_fields(); + _has_aborted = true; + + SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); + satb_mq_set.abandon_partial_marking(); + satb_mq_set.set_active_all_threads(false); +} + +static void print_ms_time_info(const char* prefix, const char* name, + NumberSeq& ns) { + gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).", + prefix, ns.num(), name, ns.sum()/1000.0, ns.avg()); + if (ns.num() > 0) { + gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]", + prefix, ns.sd(), ns.maximum()); + } +} + +void ConcurrentMark::print_summary_info() { + gclog_or_tty->print_cr(" Concurrent marking:"); + print_ms_time_info(" ", "init marks", _init_times); + print_ms_time_info(" ", "remarks", _remark_times); + { + print_ms_time_info(" ", "final marks", _remark_mark_times); + print_ms_time_info(" ", "weak refs", _remark_weak_ref_times); + + } + print_ms_time_info(" ", "cleanups", _cleanup_times); + gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).", + _total_counting_time, + (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 / + (double)_cleanup_times.num() + : 0.0)); + if (G1ScrubRemSets) { + gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).", + _total_rs_scrub_time, + (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 / + (double)_cleanup_times.num() + : 0.0)); + } + gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.", + (_init_times.sum() + _remark_times.sum() + + _cleanup_times.sum())/1000.0); + gclog_or_tty->print_cr(" Total concurrent time = %8.2f s " + "(%8.2f s marking, %8.2f s counting).", + cmThread()->vtime_accum(), + cmThread()->vtime_mark_accum(), + cmThread()->vtime_count_accum()); +} + +// Closures +// XXX: there seems to be a lot of code duplication here; +// should refactor and consolidate the shared code. + +// This closure is used to mark refs into the CMS generation in +// the CMS bit map. Called at the first checkpoint. + +// We take a break if someone is trying to stop the world. +bool ConcurrentMark::do_yield_check(int worker_i) { + if (should_yield()) { + if (worker_i == 0) + _g1h->g1_policy()->record_concurrent_pause(); + cmThread()->yield(); + if (worker_i == 0) + _g1h->g1_policy()->record_concurrent_pause_end(); + return true; + } else { + return false; + } +} + +bool ConcurrentMark::should_yield() { + return cmThread()->should_yield(); +} + +bool ConcurrentMark::containing_card_is_marked(void* p) { + size_t offset = pointer_delta(p, _g1h->reserved_region().start(), 1); + return _card_bm.at(offset >> CardTableModRefBS::card_shift); +} + +bool ConcurrentMark::containing_cards_are_marked(void* start, + void* last) { + return + containing_card_is_marked(start) && + containing_card_is_marked(last); +} + +#ifndef PRODUCT +// for debugging purposes +void ConcurrentMark::print_finger() { + gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT, + _heap_start, _heap_end, _finger); + for (int i = 0; i < (int) _max_task_num; ++i) { + gclog_or_tty->print(" %d: "PTR_FORMAT, i, _tasks[i]->finger()); + } + gclog_or_tty->print_cr(""); +} +#endif + +// Closure for iteration over bitmaps +class CMBitMapClosure : public BitMapClosure { +private: + // the bitmap that is being iterated over + CMBitMap* _nextMarkBitMap; + ConcurrentMark* _cm; + CMTask* _task; + // true if we're scanning a heap region claimed by the task (so that + // we move the finger along), false if we're not, i.e. currently when + // scanning a heap region popped from the region stack (so that we + // do not move the task finger along; it'd be a mistake if we did so). + bool _scanning_heap_region; + +public: + CMBitMapClosure(CMTask *task, + ConcurrentMark* cm, + CMBitMap* nextMarkBitMap) + : _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { } + + void set_scanning_heap_region(bool scanning_heap_region) { + _scanning_heap_region = scanning_heap_region; + } + + bool do_bit(size_t offset) { + HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset); + tmp_guarantee_CM( _nextMarkBitMap->isMarked(addr), "invariant" ); + tmp_guarantee_CM( addr < _cm->finger(), "invariant" ); + + if (_scanning_heap_region) { + statsOnly( _task->increase_objs_found_on_bitmap() ); + tmp_guarantee_CM( addr >= _task->finger(), "invariant" ); + // We move that task's local finger along. + _task->move_finger_to(addr); + } else { + // We move the task's region finger along. + _task->move_region_finger_to(addr); + } + + _task->scan_object(oop(addr)); + // we only partially drain the local queue and global stack + _task->drain_local_queue(true); + _task->drain_global_stack(true); + + // if the has_aborted flag has been raised, we need to bail out of + // the iteration + return !_task->has_aborted(); + } +}; + +// Closure for iterating over objects, currently only used for +// processing SATB buffers. +class CMObjectClosure : public ObjectClosure { +private: + CMTask* _task; + +public: + void do_object(oop obj) { + _task->deal_with_reference(obj); + } + + CMObjectClosure(CMTask* task) : _task(task) { } +}; + +// Closure for iterating over object fields +class CMOopClosure : public OopClosure { +private: + G1CollectedHeap* _g1h; + ConcurrentMark* _cm; + CMTask* _task; + +public: + void do_oop(narrowOop* p) { + guarantee(false, "NYI"); + } + + void do_oop(oop* p) { + tmp_guarantee_CM( _g1h->is_in_g1_reserved((HeapWord*) p), "invariant" ); + + oop obj = *p; + if (_cm->verbose_high()) + gclog_or_tty->print_cr("[%d] we're looking at location " + "*"PTR_FORMAT" = "PTR_FORMAT, + _task->task_id(), p, (void*) obj); + _task->deal_with_reference(obj); + } + + CMOopClosure(G1CollectedHeap* g1h, + ConcurrentMark* cm, + CMTask* task) + : _g1h(g1h), _cm(cm), _task(task) { } +}; + +void CMTask::setup_for_region(HeapRegion* hr) { + tmp_guarantee_CM( hr != NULL && !hr->continuesHumongous(), + "claim_region() should have filtered out continues humongous regions" ); + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] setting up for region "PTR_FORMAT, + _task_id, hr); + + _curr_region = hr; + _finger = hr->bottom(); + update_region_limit(); +} + +void CMTask::update_region_limit() { + HeapRegion* hr = _curr_region; + HeapWord* bottom = hr->bottom(); + HeapWord* limit = hr->next_top_at_mark_start(); + + if (limit == bottom) { + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] found an empty region " + "["PTR_FORMAT", "PTR_FORMAT")", + _task_id, bottom, limit); + // The region was collected underneath our feet. + // We set the finger to bottom to ensure that the bitmap + // iteration that will follow this will not do anything. + // (this is not a condition that holds when we set the region up, + // as the region is not supposed to be empty in the first place) + _finger = bottom; + } else if (limit >= _region_limit) { + tmp_guarantee_CM( limit >= _finger, "peace of mind" ); + } else { + tmp_guarantee_CM( limit < _region_limit, "only way to get here" ); + // This can happen under some pretty unusual circumstances. An + // evacuation pause empties the region underneath our feet (NTAMS + // at bottom). We then do some allocation in the region (NTAMS + // stays at bottom), followed by the region being used as a GC + // alloc region (NTAMS will move to top() and the objects + // originally below it will be grayed). All objects now marked in + // the region are explicitly grayed, if below the global finger, + // and we do not need in fact to scan anything else. So, we simply + // set _finger to be limit to ensure that the bitmap iteration + // doesn't do anything. + _finger = limit; + } + + _region_limit = limit; +} + +void CMTask::giveup_current_region() { + tmp_guarantee_CM( _curr_region != NULL, "invariant" ); + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] giving up region "PTR_FORMAT, + _task_id, _curr_region); + clear_region_fields(); +} + +void CMTask::clear_region_fields() { + // Values for these three fields that indicate that we're not + // holding on to a region. + _curr_region = NULL; + _finger = NULL; + _region_limit = NULL; + + _region_finger = NULL; +} + +void CMTask::reset(CMBitMap* nextMarkBitMap) { + guarantee( nextMarkBitMap != NULL, "invariant" ); + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] resetting", _task_id); + + _nextMarkBitMap = nextMarkBitMap; + clear_region_fields(); + + _calls = 0; + _elapsed_time_ms = 0.0; + _termination_time_ms = 0.0; + _termination_start_time_ms = 0.0; + +#if _MARKING_STATS_ + _local_pushes = 0; + _local_pops = 0; + _local_max_size = 0; + _objs_scanned = 0; + _global_pushes = 0; + _global_pops = 0; + _global_max_size = 0; + _global_transfers_to = 0; + _global_transfers_from = 0; + _region_stack_pops = 0; + _regions_claimed = 0; + _objs_found_on_bitmap = 0; + _satb_buffers_processed = 0; + _steal_attempts = 0; + _steals = 0; + _aborted = 0; + _aborted_overflow = 0; + _aborted_cm_aborted = 0; + _aborted_yield = 0; + _aborted_timed_out = 0; + _aborted_satb = 0; + _aborted_termination = 0; +#endif // _MARKING_STATS_ +} + +bool CMTask::should_exit_termination() { + regular_clock_call(); + // This is called when we are in the termination protocol. We should + // quit if, for some reason, this task wants to abort or the global + // stack is not empty (this means that we can get work from it). + return !_cm->mark_stack_empty() || has_aborted(); +} + +// This determines whether the method below will check both the local +// and global fingers when determining whether to push on the stack a +// gray object (value 1) or whether it will only check the global one +// (value 0). The tradeoffs are that the former will be a bit more +// accurate and possibly push less on the stack, but it might also be +// a little bit slower. + +#define _CHECK_BOTH_FINGERS_ 1 + +void CMTask::deal_with_reference(oop obj) { + if (_cm->verbose_high()) + gclog_or_tty->print_cr("[%d] we're dealing with reference = "PTR_FORMAT, + _task_id, (void*) obj); + + ++_refs_reached; + + HeapWord* objAddr = (HeapWord*) obj; + if (_g1h->is_in_g1_reserved(objAddr)) { + tmp_guarantee_CM( obj != NULL, "is_in_g1_reserved should ensure this" ); + HeapRegion* hr = _g1h->heap_region_containing(obj); + if (_g1h->is_obj_ill(obj, hr)) { + if (_cm->verbose_high()) + gclog_or_tty->print_cr("[%d] "PTR_FORMAT" is not considered marked", + _task_id, (void*) obj); + + // we need to mark it first + if (_nextMarkBitMap->parMark(objAddr)) { + // No OrderAccess:store_load() is needed. It is implicit in the + // CAS done in parMark(objAddr) above + HeapWord* global_finger = _cm->finger(); + +#if _CHECK_BOTH_FINGERS_ + // we will check both the local and global fingers + + if (_finger != NULL && objAddr < _finger) { + if (_cm->verbose_high()) + gclog_or_tty->print_cr("[%d] below the local finger ("PTR_FORMAT"), " + "pushing it", _task_id, _finger); + push(obj); + } else if (_curr_region != NULL && objAddr < _region_limit) { + // do nothing + } else if (objAddr < global_finger) { + // Notice that the global finger might be moving forward + // concurrently. This is not a problem. In the worst case, we + // mark the object while it is above the global finger and, by + // the time we read the global finger, it has moved forward + // passed this object. In this case, the object will probably + // be visited when a task is scanning the region and will also + // be pushed on the stack. So, some duplicate work, but no + // correctness problems. + + if (_cm->verbose_high()) + gclog_or_tty->print_cr("[%d] below the global finger " + "("PTR_FORMAT"), pushing it", + _task_id, global_finger); + push(obj); + } else { + // do nothing + } +#else // _CHECK_BOTH_FINGERS_ + // we will only check the global finger + + if (objAddr < global_finger) { + // see long comment above + + if (_cm->verbose_high()) + gclog_or_tty->print_cr("[%d] below the global finger " + "("PTR_FORMAT"), pushing it", + _task_id, global_finger); + push(obj); + } +#endif // _CHECK_BOTH_FINGERS_ + } + } + } +} + +void CMTask::push(oop obj) { + HeapWord* objAddr = (HeapWord*) obj; + tmp_guarantee_CM( _g1h->is_in_g1_reserved(objAddr), "invariant" ); + tmp_guarantee_CM( !_g1h->is_obj_ill(obj), "invariant" ); + tmp_guarantee_CM( _nextMarkBitMap->isMarked(objAddr), "invariant" ); + + if (_cm->verbose_high()) + gclog_or_tty->print_cr("[%d] pushing "PTR_FORMAT, _task_id, (void*) obj); + + if (!_task_queue->push(obj)) { + // The local task queue looks full. We need to push some entries + // to the global stack. + + if (_cm->verbose_medium()) + gclog_or_tty->print_cr("[%d] task queue overflow, " + "moving entries to the global stack", + _task_id); + move_entries_to_global_stack(); + + // this should succeed since, even if we overflow the global + // stack, we should have definitely removed some entries from the + // local queue. So, there must be space on it. + bool success = _task_queue->push(obj); + tmp_guarantee_CM( success, "invariant" ); + } + + statsOnly( int tmp_size = _task_queue->size(); + if (tmp_size > _local_max_size) + _local_max_size = tmp_size; + ++_local_pushes ); +} + +void CMTask::reached_limit() { + tmp_guarantee_CM( _words_scanned >= _words_scanned_limit || + _refs_reached >= _refs_reached_limit , + "shouldn't have been called otherwise" ); + regular_clock_call(); +} + +void CMTask::regular_clock_call() { + if (has_aborted()) + return; + + // First, we need to recalculate the words scanned and refs reached + // limits for the next clock call. + recalculate_limits(); + + // During the regular clock call we do the following + + // (1) If an overflow has been flagged, then we abort. + if (_cm->has_overflown()) { + set_has_aborted(); + return; + } + + // If we are not concurrent (i.e. we're doing remark) we don't need + // to check anything else. The other steps are only needed during + // the concurrent marking phase. + if (!concurrent()) + return; + + // (2) If marking has been aborted for Full GC, then we also abort. + if (_cm->has_aborted()) { + set_has_aborted(); + statsOnly( ++_aborted_cm_aborted ); + return; + } + + double curr_time_ms = os::elapsedVTime() * 1000.0; + + // (3) If marking stats are enabled, then we update the step history. +#if _MARKING_STATS_ + if (_words_scanned >= _words_scanned_limit) + ++_clock_due_to_scanning; + if (_refs_reached >= _refs_reached_limit) + ++_clock_due_to_marking; + + double last_interval_ms = curr_time_ms - _interval_start_time_ms; + _interval_start_time_ms = curr_time_ms; + _all_clock_intervals_ms.add(last_interval_ms); + + if (_cm->verbose_medium()) { + gclog_or_tty->print_cr("[%d] regular clock, interval = %1.2lfms, " + "scanned = %d%s, refs reached = %d%s", + _task_id, last_interval_ms, + _words_scanned, + (_words_scanned >= _words_scanned_limit) ? " (*)" : "", + _refs_reached, + (_refs_reached >= _refs_reached_limit) ? " (*)" : ""); + } +#endif // _MARKING_STATS_ + + // (4) We check whether we should yield. If we have to, then we abort. + if (_cm->should_yield()) { + // We should yield. To do this we abort the task. The caller is + // responsible for yielding. + set_has_aborted(); + statsOnly( ++_aborted_yield ); + return; + } + + // (5) We check whether we've reached our time quota. If we have, + // then we abort. + double elapsed_time_ms = curr_time_ms - _start_time_ms; + if (elapsed_time_ms > _time_target_ms) { + set_has_aborted(); + _has_aborted_timed_out = true; + statsOnly( ++_aborted_timed_out ); + return; + } + + // (6) Finally, we check whether there are enough completed STAB + // buffers available for processing. If there are, we abort. + SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); + if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) { + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] aborting to deal with pending SATB buffers", + _task_id); + // we do need to process SATB buffers, we'll abort and restart + // the marking task to do so + set_has_aborted(); + statsOnly( ++_aborted_satb ); + return; + } +} + +void CMTask::recalculate_limits() { + _real_words_scanned_limit = _words_scanned + words_scanned_period; + _words_scanned_limit = _real_words_scanned_limit; + + _real_refs_reached_limit = _refs_reached + refs_reached_period; + _refs_reached_limit = _real_refs_reached_limit; +} + +void CMTask::decrease_limits() { + // This is called when we believe that we're going to do an infrequent + // operation which will increase the per byte scanned cost (i.e. move + // entries to/from the global stack). It basically tries to decrease the + // scanning limit so that the clock is called earlier. + + if (_cm->verbose_medium()) + gclog_or_tty->print_cr("[%d] decreasing limits", _task_id); + + _words_scanned_limit = _real_words_scanned_limit - + 3 * words_scanned_period / 4; + _refs_reached_limit = _real_refs_reached_limit - + 3 * refs_reached_period / 4; +} + +void CMTask::move_entries_to_global_stack() { + // local array where we'll store the entries that will be popped + // from the local queue + oop buffer[global_stack_transfer_size]; + + int n = 0; + oop obj; + while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) { + buffer[n] = obj; + ++n; + } + + if (n > 0) { + // we popped at least one entry from the local queue + + statsOnly( ++_global_transfers_to; _local_pops += n ); + + if (!_cm->mark_stack_push(buffer, n)) { + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] aborting due to global stack overflow", _task_id); + set_has_aborted(); + } else { + // the transfer was successful + + if (_cm->verbose_medium()) + gclog_or_tty->print_cr("[%d] pushed %d entries to the global stack", + _task_id, n); + statsOnly( int tmp_size = _cm->mark_stack_size(); + if (tmp_size > _global_max_size) + _global_max_size = tmp_size; + _global_pushes += n ); + } + } + + // this operation was quite expensive, so decrease the limits + decrease_limits(); +} + +void CMTask::get_entries_from_global_stack() { + // local array where we'll store the entries that will be popped + // from the global stack. + oop buffer[global_stack_transfer_size]; + int n; + _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n); + tmp_guarantee_CM( n <= global_stack_transfer_size, + "we should not pop more than the given limit" ); + if (n > 0) { + // yes, we did actually pop at least one entry + + statsOnly( ++_global_transfers_from; _global_pops += n ); + if (_cm->verbose_medium()) + gclog_or_tty->print_cr("[%d] popped %d entries from the global stack", + _task_id, n); + for (int i = 0; i < n; ++i) { + bool success = _task_queue->push(buffer[i]); + // We only call this when the local queue is empty or under a + // given target limit. So, we do not expect this push to fail. + tmp_guarantee_CM( success, "invariant" ); + } + + statsOnly( int tmp_size = _task_queue->size(); + if (tmp_size > _local_max_size) + _local_max_size = tmp_size; + _local_pushes += n ); + } + + // this operation was quite expensive, so decrease the limits + decrease_limits(); +} + +void CMTask::drain_local_queue(bool partially) { + if (has_aborted()) + return; + + // Decide what the target size is, depending whether we're going to + // drain it partially (so that other tasks can steal if they run out + // of things to do) or totally (at the very end). + size_t target_size; + if (partially) + target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize); + else + target_size = 0; + + if (_task_queue->size() > target_size) { + if (_cm->verbose_high()) + gclog_or_tty->print_cr("[%d] draining local queue, target size = %d", + _task_id, target_size); + + oop obj; + bool ret = _task_queue->pop_local(obj); + while (ret) { + statsOnly( ++_local_pops ); + + if (_cm->verbose_high()) + gclog_or_tty->print_cr("[%d] popped "PTR_FORMAT, _task_id, + (void*) obj); + + tmp_guarantee_CM( _g1h->is_in_g1_reserved((HeapWord*) obj), + "invariant" ); + + scan_object(obj); + + if (_task_queue->size() <= target_size || has_aborted()) + ret = false; + else + ret = _task_queue->pop_local(obj); + } + + if (_cm->verbose_high()) + gclog_or_tty->print_cr("[%d] drained local queue, size = %d", + _task_id, _task_queue->size()); + } +} + +void CMTask::drain_global_stack(bool partially) { + if (has_aborted()) + return; + + // We have a policy to drain the local queue before we attempt to + // drain the global stack. + tmp_guarantee_CM( partially || _task_queue->size() == 0, "invariant" ); + + // Decide what the target size is, depending whether we're going to + // drain it partially (so that other tasks can steal if they run out + // of things to do) or totally (at the very end). Notice that, + // because we move entries from the global stack in chunks or + // because another task might be doing the same, we might in fact + // drop below the target. But, this is not a problem. + size_t target_size; + if (partially) + target_size = _cm->partial_mark_stack_size_target(); + else + target_size = 0; + + if (_cm->mark_stack_size() > target_size) { + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] draining global_stack, target size %d", + _task_id, target_size); + + while (!has_aborted() && _cm->mark_stack_size() > target_size) { + get_entries_from_global_stack(); + drain_local_queue(partially); + } + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] drained global stack, size = %d", + _task_id, _cm->mark_stack_size()); + } +} + +// SATB Queue has several assumptions on whether to call the par or +// non-par versions of the methods. this is why some of the code is +// replicated. We should really get rid of the single-threaded version +// of the code to simplify things. +void CMTask::drain_satb_buffers() { + if (has_aborted()) + return; + + // We set this so that the regular clock knows that we're in the + // middle of draining buffers and doesn't set the abort flag when it + // notices that SATB buffers are available for draining. It'd be + // very counter productive if it did that. :-) + _draining_satb_buffers = true; + + CMObjectClosure oc(this); + SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); + if (ParallelGCThreads > 0) + satb_mq_set.set_par_closure(_task_id, &oc); + else + satb_mq_set.set_closure(&oc); + + // This keeps claiming and applying the closure to completed buffers + // until we run out of buffers or we need to abort. + if (ParallelGCThreads > 0) { + while (!has_aborted() && + satb_mq_set.par_apply_closure_to_completed_buffer(_task_id)) { + if (_cm->verbose_medium()) + gclog_or_tty->print_cr("[%d] processed an SATB buffer", _task_id); + statsOnly( ++_satb_buffers_processed ); + regular_clock_call(); + } + } else { + while (!has_aborted() && + satb_mq_set.apply_closure_to_completed_buffer()) { + if (_cm->verbose_medium()) + gclog_or_tty->print_cr("[%d] processed an SATB buffer", _task_id); + statsOnly( ++_satb_buffers_processed ); + regular_clock_call(); + } + } + + if (!concurrent() && !has_aborted()) { + // We should only do this during remark. + if (ParallelGCThreads > 0) + satb_mq_set.par_iterate_closure_all_threads(_task_id); + else + satb_mq_set.iterate_closure_all_threads(); + } + + _draining_satb_buffers = false; + + tmp_guarantee_CM( has_aborted() || + concurrent() || + satb_mq_set.completed_buffers_num() == 0, "invariant" ); + + if (ParallelGCThreads > 0) + satb_mq_set.set_par_closure(_task_id, NULL); + else + satb_mq_set.set_closure(NULL); + + // again, this was a potentially expensive operation, decrease the + // limits to get the regular clock call early + decrease_limits(); +} + +void CMTask::drain_region_stack(BitMapClosure* bc) { + if (has_aborted()) + return; + + tmp_guarantee_CM( _region_finger == NULL, + "it should be NULL when we're not scanning a region" ); + + if (!_cm->region_stack_empty()) { + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] draining region stack, size = %d", + _task_id, _cm->region_stack_size()); + + MemRegion mr = _cm->region_stack_pop(); + // it returns MemRegion() if the pop fails + statsOnly(if (mr.start() != NULL) ++_region_stack_pops ); + + while (mr.start() != NULL) { + if (_cm->verbose_medium()) + gclog_or_tty->print_cr("[%d] we are scanning region " + "["PTR_FORMAT", "PTR_FORMAT")", + _task_id, mr.start(), mr.end()); + tmp_guarantee_CM( mr.end() <= _cm->finger(), + "otherwise the region shouldn't be on the stack" ); + assert(!mr.is_empty(), "Only non-empty regions live on the region stack"); + if (_nextMarkBitMap->iterate(bc, mr)) { + tmp_guarantee_CM( !has_aborted(), + "cannot abort the task without aborting the bitmap iteration" ); + + // We finished iterating over the region without aborting. + regular_clock_call(); + if (has_aborted()) + mr = MemRegion(); + else { + mr = _cm->region_stack_pop(); + // it returns MemRegion() if the pop fails + statsOnly(if (mr.start() != NULL) ++_region_stack_pops ); + } + } else { + guarantee( has_aborted(), "currently the only way to do so" ); + + // The only way to abort the bitmap iteration is to return + // false from the do_bit() method. However, inside the + // do_bit() method we move the _region_finger to point to the + // object currently being looked at. So, if we bail out, we + // have definitely set _region_finger to something non-null. + guarantee( _region_finger != NULL, "invariant" ); + + // The iteration was actually aborted. So now _region_finger + // points to the address of the object we last scanned. If we + // leave it there, when we restart this task, we will rescan + // the object. It is easy to avoid this. We move the finger by + // enough to point to the next possible object header (the + // bitmap knows by how much we need to move it as it knows its + // granularity). + MemRegion newRegion = + MemRegion(_nextMarkBitMap->nextWord(_region_finger), mr.end()); + + if (!newRegion.is_empty()) { + if (_cm->verbose_low()) { + gclog_or_tty->print_cr("[%d] pushing unscanned region" + "[" PTR_FORMAT "," PTR_FORMAT ") on region stack", + _task_id, + newRegion.start(), newRegion.end()); + } + // Now push the part of the region we didn't scan on the + // region stack to make sure a task scans it later. + _cm->region_stack_push(newRegion); + } + // break from while + mr = MemRegion(); + } + _region_finger = NULL; + } + + // We only push regions on the region stack during evacuation + // pauses. So if we come out the above iteration because we region + // stack is empty, it will remain empty until the next yield + // point. So, the guarantee below is safe. + guarantee( has_aborted() || _cm->region_stack_empty(), + "only way to exit the loop" ); + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] drained region stack, size = %d", + _task_id, _cm->region_stack_size()); + } +} + +void CMTask::print_stats() { + gclog_or_tty->print_cr("Marking Stats, task = %d, calls = %d", + _task_id, _calls); + gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms", + _elapsed_time_ms, _termination_time_ms); + gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms", + _step_times_ms.num(), _step_times_ms.avg(), + _step_times_ms.sd()); + gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms", + _step_times_ms.maximum(), _step_times_ms.sum()); + +#if _MARKING_STATS_ + gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms", + _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(), + _all_clock_intervals_ms.sd()); + gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms", + _all_clock_intervals_ms.maximum(), + _all_clock_intervals_ms.sum()); + gclog_or_tty->print_cr(" Clock Causes (cum): scanning = %d, marking = %d", + _clock_due_to_scanning, _clock_due_to_marking); + gclog_or_tty->print_cr(" Objects: scanned = %d, found on the bitmap = %d", + _objs_scanned, _objs_found_on_bitmap); + gclog_or_tty->print_cr(" Local Queue: pushes = %d, pops = %d, max size = %d", + _local_pushes, _local_pops, _local_max_size); + gclog_or_tty->print_cr(" Global Stack: pushes = %d, pops = %d, max size = %d", + _global_pushes, _global_pops, _global_max_size); + gclog_or_tty->print_cr(" transfers to = %d, transfers from = %d", + _global_transfers_to,_global_transfers_from); + gclog_or_tty->print_cr(" Regions: claimed = %d, Region Stack: pops = %d", + _regions_claimed, _region_stack_pops); + gclog_or_tty->print_cr(" SATB buffers: processed = %d", _satb_buffers_processed); + gclog_or_tty->print_cr(" Steals: attempts = %d, successes = %d", + _steal_attempts, _steals); + gclog_or_tty->print_cr(" Aborted: %d, due to", _aborted); + gclog_or_tty->print_cr(" overflow: %d, global abort: %d, yield: %d", + _aborted_overflow, _aborted_cm_aborted, _aborted_yield); + gclog_or_tty->print_cr(" time out: %d, SATB: %d, termination: %d", + _aborted_timed_out, _aborted_satb, _aborted_termination); +#endif // _MARKING_STATS_ +} + +/***************************************************************************** + + The do_marking_step(time_target_ms) method is the building block + of the parallel marking framework. It can be called in parallel + with other invocations of do_marking_step() on different tasks + (but only one per task, obviously) and concurrently with the + mutator threads, or during remark, hence it eliminates the need + for two versions of the code. When called during remark, it will + pick up from where the task left off during the concurrent marking + phase. Interestingly, tasks are also claimable during evacuation + pauses too, since do_marking_step() ensures that it aborts before + it needs to yield. + + The data structures that is uses to do marking work are the + following: + + (1) Marking Bitmap. If there are gray objects that appear only + on the bitmap (this happens either when dealing with an overflow + or when the initial marking phase has simply marked the roots + and didn't push them on the stack), then tasks claim heap + regions whose bitmap they then scan to find gray objects. A + global finger indicates where the end of the last claimed region + is. A local finger indicates how far into the region a task has + scanned. The two fingers are used to determine how to gray an + object (i.e. whether simply marking it is OK, as it will be + visited by a task in the future, or whether it needs to be also + pushed on a stack). + + (2) Local Queue. The local queue of the task which is accessed + reasonably efficiently by the task. Other tasks can steal from + it when they run out of work. Throughout the marking phase, a + task attempts to keep its local queue short but not totally + empty, so that entries are available for stealing by other + tasks. Only when there is no more work, a task will totally + drain its local queue. + + (3) Global Mark Stack. This handles local queue overflow. During + marking only sets of entries are moved between it and the local + queues, as access to it requires a mutex and more fine-grain + interaction with it which might cause contention. If it + overflows, then the marking phase should restart and iterate + over the bitmap to identify gray objects. Throughout the marking + phase, tasks attempt to keep the global mark stack at a small + length but not totally empty, so that entries are available for + popping by other tasks. Only when there is no more work, tasks + will totally drain the global mark stack. + + (4) Global Region Stack. Entries on it correspond to areas of + the bitmap that need to be scanned since they contain gray + objects. Pushes on the region stack only happen during + evacuation pauses and typically correspond to areas covered by + GC LABS. If it overflows, then the marking phase should restart + and iterate over the bitmap to identify gray objects. Tasks will + try to totally drain the region stack as soon as possible. + + (5) SATB Buffer Queue. This is where completed SATB buffers are + made available. Buffers are regularly removed from this queue + and scanned for roots, so that the queue doesn't get too + long. During remark, all completed buffers are processed, as + well as the filled in parts of any uncompleted buffers. + + The do_marking_step() method tries to abort when the time target + has been reached. There are a few other cases when the + do_marking_step() method also aborts: + + (1) When the marking phase has been aborted (after a Full GC). + + (2) When a global overflow (either on the global stack or the + region stack) has been triggered. Before the task aborts, it + will actually sync up with the other tasks to ensure that all + the marking data structures (local queues, stacks, fingers etc.) + are re-initialised so that when do_marking_step() completes, + the marking phase can immediately restart. + + (3) When enough completed SATB buffers are available. The + do_marking_step() method only tries to drain SATB buffers right + at the beginning. So, if enough buffers are available, the + marking step aborts and the SATB buffers are processed at + the beginning of the next invocation. + + (4) To yield. when we have to yield then we abort and yield + right at the end of do_marking_step(). This saves us from a lot + of hassle as, by yielding we might allow a Full GC. If this + happens then objects will be compacted underneath our feet, the + heap might shrink, etc. We save checking for this by just + aborting and doing the yield right at the end. + + From the above it follows that the do_marking_step() method should + be called in a loop (or, otherwise, regularly) until it completes. + + If a marking step completes without its has_aborted() flag being + true, it means it has completed the current marking phase (and + also all other marking tasks have done so and have all synced up). + + A method called regular_clock_call() is invoked "regularly" (in + sub ms intervals) throughout marking. It is this clock method that + checks all the abort conditions which were mentioned above and + decides when the task should abort. A work-based scheme is used to + trigger this clock method: when the number of object words the + marking phase has scanned or the number of references the marking + phase has visited reach a given limit. Additional invocations to + the method clock have been planted in a few other strategic places + too. The initial reason for the clock method was to avoid calling + vtime too regularly, as it is quite expensive. So, once it was in + place, it was natural to piggy-back all the other conditions on it + too and not constantly check them throughout the code. + + *****************************************************************************/ + +void CMTask::do_marking_step(double time_target_ms) { + guarantee( time_target_ms >= 1.0, "minimum granularity is 1ms" ); + guarantee( concurrent() == _cm->concurrent(), "they should be the same" ); + + guarantee( concurrent() || _cm->region_stack_empty(), + "the region stack should have been cleared before remark" ); + guarantee( _region_finger == NULL, + "this should be non-null only when a region is being scanned" ); + + G1CollectorPolicy* g1_policy = _g1h->g1_policy(); + guarantee( _task_queues != NULL, "invariant" ); + guarantee( _task_queue != NULL, "invariant" ); + guarantee( _task_queues->queue(_task_id) == _task_queue, "invariant" ); + + guarantee( !_claimed, + "only one thread should claim this task at any one time" ); + + // OK, this doesn't safeguard again all possible scenarios, as it is + // possible for two threads to set the _claimed flag at the same + // time. But it is only for debugging purposes anyway and it will + // catch most problems. + _claimed = true; + + _start_time_ms = os::elapsedVTime() * 1000.0; + statsOnly( _interval_start_time_ms = _start_time_ms ); + + double diff_prediction_ms = + g1_policy->get_new_prediction(&_marking_step_diffs_ms); + _time_target_ms = time_target_ms - diff_prediction_ms; + + // set up the variables that are used in the work-based scheme to + // call the regular clock method + _words_scanned = 0; + _refs_reached = 0; + recalculate_limits(); + + // clear all flags + clear_has_aborted(); + _has_aborted_timed_out = false; + _draining_satb_buffers = false; + + ++_calls; + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] >>>>>>>>>> START, call = %d, " + "target = %1.2lfms >>>>>>>>>>", + _task_id, _calls, _time_target_ms); + + // Set up the bitmap and oop closures. Anything that uses them is + // eventually called from this method, so it is OK to allocate these + // statically. + CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap); + CMOopClosure oop_closure(_g1h, _cm, this); + set_oop_closure(&oop_closure); + + if (_cm->has_overflown()) { + // This can happen if the region stack or the mark stack overflows + // during a GC pause and this task, after a yield point, + // restarts. We have to abort as we need to get into the overflow + // protocol which happens right at the end of this task. + set_has_aborted(); + } + + // First drain any available SATB buffers. After this, we will not + // look at SATB buffers before the next invocation of this method. + // If enough completed SATB buffers are queued up, the regular clock + // will abort this task so that it restarts. + drain_satb_buffers(); + // ...then partially drain the local queue and the global stack + drain_local_queue(true); + drain_global_stack(true); + + // Then totally drain the region stack. We will not look at + // it again before the next invocation of this method. Entries on + // the region stack are only added during evacuation pauses, for + // which we have to yield. When we do, we abort the task anyway so + // it will look at the region stack again when it restarts. + bitmap_closure.set_scanning_heap_region(false); + drain_region_stack(&bitmap_closure); + // ...then partially drain the local queue and the global stack + drain_local_queue(true); + drain_global_stack(true); + + do { + if (!has_aborted() && _curr_region != NULL) { + // This means that we're already holding on to a region. + tmp_guarantee_CM( _finger != NULL, + "if region is not NULL, then the finger " + "should not be NULL either" ); + + // We might have restarted this task after an evacuation pause + // which might have evacuated the region we're holding on to + // underneath our feet. Let's read its limit again to make sure + // that we do not iterate over a region of the heap that + // contains garbage (update_region_limit() will also move + // _finger to the start of the region if it is found empty). + update_region_limit(); + // We will start from _finger not from the start of the region, + // as we might be restarting this task after aborting half-way + // through scanning this region. In this case, _finger points to + // the address where we last found a marked object. If this is a + // fresh region, _finger points to start(). + MemRegion mr = MemRegion(_finger, _region_limit); + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] we're scanning part " + "["PTR_FORMAT", "PTR_FORMAT") " + "of region "PTR_FORMAT, + _task_id, _finger, _region_limit, _curr_region); + + // Let's iterate over the bitmap of the part of the + // region that is left. + bitmap_closure.set_scanning_heap_region(true); + if (mr.is_empty() || + _nextMarkBitMap->iterate(&bitmap_closure, mr)) { + // We successfully completed iterating over the region. Now, + // let's give up the region. + giveup_current_region(); + regular_clock_call(); + } else { + guarantee( has_aborted(), "currently the only way to do so" ); + // The only way to abort the bitmap iteration is to return + // false from the do_bit() method. However, inside the + // do_bit() method we move the _finger to point to the + // object currently being looked at. So, if we bail out, we + // have definitely set _finger to something non-null. + guarantee( _finger != NULL, "invariant" ); + + // Region iteration was actually aborted. So now _finger + // points to the address of the object we last scanned. If we + // leave it there, when we restart this task, we will rescan + // the object. It is easy to avoid this. We move the finger by + // enough to point to the next possible object header (the + // bitmap knows by how much we need to move it as it knows its + // granularity). + move_finger_to(_nextMarkBitMap->nextWord(_finger)); + } + } + // At this point we have either completed iterating over the + // region we were holding on to, or we have aborted. + + // We then partially drain the local queue and the global stack. + // (Do we really need this?) + drain_local_queue(true); + drain_global_stack(true); + + // Read the note on the claim_region() method on why it might + // return NULL with potentially more regions available for + // claiming and why we have to check out_of_regions() to determine + // whether we're done or not. + while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) { + // We are going to try to claim a new region. We should have + // given up on the previous one. + tmp_guarantee_CM( _curr_region == NULL && + _finger == NULL && + _region_limit == NULL, "invariant" ); + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] trying to claim a new region", _task_id); + HeapRegion* claimed_region = _cm->claim_region(_task_id); + if (claimed_region != NULL) { + // Yes, we managed to claim one + statsOnly( ++_regions_claimed ); + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] we successfully claimed " + "region "PTR_FORMAT, + _task_id, claimed_region); + + setup_for_region(claimed_region); + tmp_guarantee_CM( _curr_region == claimed_region, "invariant" ); + } + // It is important to call the regular clock here. It might take + // a while to claim a region if, for example, we hit a large + // block of empty regions. So we need to call the regular clock + // method once round the loop to make sure it's called + // frequently enough. + regular_clock_call(); + } + + if (!has_aborted() && _curr_region == NULL) { + tmp_guarantee_CM( _cm->out_of_regions(), + "at this point we should be out of regions" ); + } + } while ( _curr_region != NULL && !has_aborted()); + + if (!has_aborted()) { + // We cannot check whether the global stack is empty, since other + // tasks might be pushing objects to it concurrently. + tmp_guarantee_CM( _cm->out_of_regions() && _cm->region_stack_empty(), + "at this point we should be out of regions" ); + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] all regions claimed", _task_id); + + // Try to reduce the number of available SATB buffers so that + // remark has less work to do. + drain_satb_buffers(); + } + + // Since we've done everything else, we can now totally drain the + // local queue and global stack. + drain_local_queue(false); + drain_global_stack(false); + + // Attempt at work stealing from other task's queues. + if (!has_aborted()) { + // We have not aborted. This means that we have finished all that + // we could. Let's try to do some stealing... + + // We cannot check whether the global stack is empty, since other + // tasks might be pushing objects to it concurrently. + guarantee( _cm->out_of_regions() && + _cm->region_stack_empty() && + _task_queue->size() == 0, "only way to reach here" ); + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] starting to steal", _task_id); + + while (!has_aborted()) { + oop obj; + statsOnly( ++_steal_attempts ); + + if (_cm->try_stealing(_task_id, &_hash_seed, obj)) { + if (_cm->verbose_medium()) + gclog_or_tty->print_cr("[%d] stolen "PTR_FORMAT" successfully", + _task_id, (void*) obj); + + statsOnly( ++_steals ); + + tmp_guarantee_CM( _nextMarkBitMap->isMarked((HeapWord*) obj), + "any stolen object should be marked" ); + scan_object(obj); + + // And since we're towards the end, let's totally drain the + // local queue and global stack. + drain_local_queue(false); + drain_global_stack(false); + } else { + break; + } + } + } + + // We still haven't aborted. Now, let's try to get into the + // termination protocol. + if (!has_aborted()) { + // We cannot check whether the global stack is empty, since other + // tasks might be concurrently pushing objects on it. + guarantee( _cm->out_of_regions() && + _cm->region_stack_empty() && + _task_queue->size() == 0, "only way to reach here" ); + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] starting termination protocol", _task_id); + + _termination_start_time_ms = os::elapsedVTime() * 1000.0; + // The CMTask class also extends the TerminatorTerminator class, + // hence its should_exit_termination() method will also decide + // whether to exit the termination protocol or not. + bool finished = _cm->terminator()->offer_termination(this); + double termination_end_time_ms = os::elapsedVTime() * 1000.0; + _termination_time_ms += + termination_end_time_ms - _termination_start_time_ms; + + if (finished) { + // We're all done. + + if (_task_id == 0) { + // let's allow task 0 to do this + if (concurrent()) { + guarantee( _cm->concurrent_marking_in_progress(), "invariant" ); + // we need to set this to false before the next + // safepoint. This way we ensure that the marking phase + // doesn't observe any more heap expansions. + _cm->clear_concurrent_marking_in_progress(); + } + } + + // We can now guarantee that the global stack is empty, since + // all other tasks have finished. + guarantee( _cm->out_of_regions() && + _cm->region_stack_empty() && + _cm->mark_stack_empty() && + _task_queue->size() == 0 && + !_cm->has_overflown() && + !_cm->mark_stack_overflow() && + !_cm->region_stack_overflow(), + "only way to reach here" ); + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] all tasks terminated", _task_id); + } else { + // Apparently there's more work to do. Let's abort this task. It + // will restart it and we can hopefully find more things to do. + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] apparently there is more work to do", _task_id); + + set_has_aborted(); + statsOnly( ++_aborted_termination ); + } + } + + // Mainly for debugging purposes to make sure that a pointer to the + // closure which was statically allocated in this frame doesn't + // escape it by accident. + set_oop_closure(NULL); + double end_time_ms = os::elapsedVTime() * 1000.0; + double elapsed_time_ms = end_time_ms - _start_time_ms; + // Update the step history. + _step_times_ms.add(elapsed_time_ms); + + if (has_aborted()) { + // The task was aborted for some reason. + + statsOnly( ++_aborted ); + + if (_has_aborted_timed_out) { + double diff_ms = elapsed_time_ms - _time_target_ms; + // Keep statistics of how well we did with respect to hitting + // our target only if we actually timed out (if we aborted for + // other reasons, then the results might get skewed). + _marking_step_diffs_ms.add(diff_ms); + } + + if (_cm->has_overflown()) { + // This is the interesting one. We aborted because a global + // overflow was raised. This means we have to restart the + // marking phase and start iterating over regions. However, in + // order to do this we have to make sure that all tasks stop + // what they are doing and re-initialise in a safe manner. We + // will achieve this with the use of two barrier sync points. + + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] detected overflow", _task_id); + + _cm->enter_first_sync_barrier(_task_id); + // When we exit this sync barrier we know that all tasks have + // stopped doing marking work. So, it's now safe to + // re-initialise our data structures. At the end of this method, + // task 0 will clear the global data structures. + + statsOnly( ++_aborted_overflow ); + + // We clear the local state of this task... + clear_region_fields(); + + // ...and enter the second barrier. + _cm->enter_second_sync_barrier(_task_id); + // At this point everything has bee re-initialised and we're + // ready to restart. + } + + if (_cm->verbose_low()) { + gclog_or_tty->print_cr("[%d] <<<<<<<<<< ABORTING, target = %1.2lfms, " + "elapsed = %1.2lfms <<<<<<<<<<", + _task_id, _time_target_ms, elapsed_time_ms); + if (_cm->has_aborted()) + gclog_or_tty->print_cr("[%d] ========== MARKING ABORTED ==========", + _task_id); + } + } else { + if (_cm->verbose_low()) + gclog_or_tty->print_cr("[%d] <<<<<<<<<< FINISHED, target = %1.2lfms, " + "elapsed = %1.2lfms <<<<<<<<<<", + _task_id, _time_target_ms, elapsed_time_ms); + } + + _claimed = false; +} + +CMTask::CMTask(int task_id, + ConcurrentMark* cm, + CMTaskQueue* task_queue, + CMTaskQueueSet* task_queues) + : _g1h(G1CollectedHeap::heap()), + _co_tracker(G1CMGroup), + _task_id(task_id), _cm(cm), + _claimed(false), + _nextMarkBitMap(NULL), _hash_seed(17), + _task_queue(task_queue), + _task_queues(task_queues), + _oop_closure(NULL) { + guarantee( task_queue != NULL, "invariant" ); + guarantee( task_queues != NULL, "invariant" ); + + statsOnly( _clock_due_to_scanning = 0; + _clock_due_to_marking = 0 ); + + _marking_step_diffs_ms.add(0.5); +}