| /* |
| * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "precompiled.hpp" |
| #include "classfile/classLoaderData.hpp" |
| #include "gc/g1/concurrentMarkThread.inline.hpp" |
| #include "gc/g1/g1CollectedHeap.inline.hpp" |
| #include "gc/g1/g1CollectorPolicy.hpp" |
| #include "gc/g1/g1MMUTracker.hpp" |
| #include "gc/g1/suspendibleThreadSet.hpp" |
| #include "gc/g1/vm_operations_g1.hpp" |
| #include "gc/shared/gcId.hpp" |
| #include "gc/shared/gcTrace.hpp" |
| #include "gc/shared/gcTraceTime.inline.hpp" |
| #include "logging/log.hpp" |
| #include "memory/resourceArea.hpp" |
| #include "runtime/vmThread.hpp" |
| |
| // ======= Concurrent Mark Thread ======== |
| |
| // The CM thread is created when the G1 garbage collector is used |
| |
| SurrogateLockerThread* |
| ConcurrentMarkThread::_slt = NULL; |
| |
| ConcurrentMarkThread::ConcurrentMarkThread(G1ConcurrentMark* cm) : |
| ConcurrentGCThread(), |
| _cm(cm), |
| _state(Idle), |
| _vtime_accum(0.0), |
| _vtime_mark_accum(0.0) { |
| |
| set_name("G1 Main Marker"); |
| create_and_start(); |
| } |
| |
| class CMCheckpointRootsFinalClosure: public VoidClosure { |
| |
| G1ConcurrentMark* _cm; |
| public: |
| |
| CMCheckpointRootsFinalClosure(G1ConcurrentMark* cm) : |
| _cm(cm) {} |
| |
| void do_void(){ |
| _cm->checkpointRootsFinal(false); // !clear_all_soft_refs |
| } |
| }; |
| |
| class CMCleanUp: public VoidClosure { |
| G1ConcurrentMark* _cm; |
| public: |
| |
| CMCleanUp(G1ConcurrentMark* cm) : |
| _cm(cm) {} |
| |
| void do_void(){ |
| _cm->cleanup(); |
| } |
| }; |
| |
| // Marking pauses can be scheduled flexibly, so we might delay marking to meet MMU. |
| void ConcurrentMarkThread::delay_to_keep_mmu(G1CollectorPolicy* g1_policy, bool remark) { |
| if (g1_policy->adaptive_young_list_length()) { |
| double now = os::elapsedTime(); |
| double prediction_ms = remark ? g1_policy->predict_remark_time_ms() |
| : g1_policy->predict_cleanup_time_ms(); |
| G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker(); |
| jlong sleep_time_ms = mmu_tracker->when_ms(now, prediction_ms); |
| os::sleep(this, sleep_time_ms, false); |
| } |
| } |
| |
| class GCConcPhaseTimer : StackObj { |
| G1ConcurrentMark* _cm; |
| |
| public: |
| GCConcPhaseTimer(G1ConcurrentMark* cm, const char* title) : _cm(cm) { |
| _cm->register_concurrent_phase_start(title); |
| } |
| |
| ~GCConcPhaseTimer() { |
| _cm->register_concurrent_phase_end(); |
| } |
| }; |
| |
| void ConcurrentMarkThread::run() { |
| initialize_in_thread(); |
| wait_for_universe_init(); |
| |
| run_service(); |
| |
| terminate(); |
| } |
| |
| void ConcurrentMarkThread::run_service() { |
| _vtime_start = os::elapsedVTime(); |
| |
| G1CollectedHeap* g1h = G1CollectedHeap::heap(); |
| G1CollectorPolicy* g1_policy = g1h->g1_policy(); |
| |
| while (!_should_terminate) { |
| // wait until started is set. |
| sleepBeforeNextCycle(); |
| if (_should_terminate) { |
| _cm->root_regions()->cancel_scan(); |
| break; |
| } |
| |
| assert(GCId::current() != GCId::undefined(), "GC id should have been set up by the initial mark GC."); |
| { |
| ResourceMark rm; |
| HandleMark hm; |
| double cycle_start = os::elapsedVTime(); |
| |
| { |
| GCConcPhaseTimer(_cm, "Concurrent Clearing of Claimed Marks"); |
| ClassLoaderDataGraph::clear_claimed_marks(); |
| } |
| |
| // We have to ensure that we finish scanning the root regions |
| // before the next GC takes place. To ensure this we have to |
| // make sure that we do not join the STS until the root regions |
| // have been scanned. If we did then it's possible that a |
| // subsequent GC could block us from joining the STS and proceed |
| // without the root regions have been scanned which would be a |
| // correctness issue. |
| |
| { |
| GCConcPhaseTimer(_cm, "Concurrent Root Region Scanning"); |
| _cm->scanRootRegions(); |
| } |
| |
| // It would be nice to use the GCTraceConcTime class here but |
| // the "end" logging is inside the loop and not at the end of |
| // a scope. Mimicking the same log output as GCTraceConcTime instead. |
| jlong mark_start = os::elapsed_counter(); |
| log_info(gc)("Concurrent Mark (%.3fs)", TimeHelper::counter_to_seconds(mark_start)); |
| |
| int iter = 0; |
| do { |
| iter++; |
| if (!cm()->has_aborted()) { |
| GCConcPhaseTimer(_cm, "Concurrent Mark"); |
| _cm->markFromRoots(); |
| } |
| |
| double mark_end_time = os::elapsedVTime(); |
| jlong mark_end = os::elapsed_counter(); |
| _vtime_mark_accum += (mark_end_time - cycle_start); |
| if (!cm()->has_aborted()) { |
| delay_to_keep_mmu(g1_policy, true /* remark */); |
| log_info(gc)("Concurrent Mark (%.3fs, %.3fs) %.3fms", |
| TimeHelper::counter_to_seconds(mark_start), |
| TimeHelper::counter_to_seconds(mark_end), |
| TimeHelper::counter_to_millis(mark_end - mark_start)); |
| |
| CMCheckpointRootsFinalClosure final_cl(_cm); |
| VM_CGC_Operation op(&final_cl, "Pause Remark", true /* needs_pll */); |
| VMThread::execute(&op); |
| } |
| if (cm()->restart_for_overflow()) { |
| log_debug(gc)("Restarting conc marking because of MS overflow in remark (restart #%d).", iter); |
| log_info(gc)("Concurrent Mark restart for overflow"); |
| } |
| } while (cm()->restart_for_overflow()); |
| |
| double end_time = os::elapsedVTime(); |
| // Update the total virtual time before doing this, since it will try |
| // to measure it to get the vtime for this marking. We purposely |
| // neglect the presumably-short "completeCleanup" phase here. |
| _vtime_accum = (end_time - _vtime_start); |
| |
| if (!cm()->has_aborted()) { |
| delay_to_keep_mmu(g1_policy, false /* cleanup */); |
| |
| CMCleanUp cl_cl(_cm); |
| VM_CGC_Operation op(&cl_cl, "Pause Cleanup", false /* needs_pll */); |
| VMThread::execute(&op); |
| } else { |
| // We don't want to update the marking status if a GC pause |
| // is already underway. |
| SuspendibleThreadSetJoiner sts_join; |
| g1h->collector_state()->set_mark_in_progress(false); |
| } |
| |
| // Check if cleanup set the free_regions_coming flag. If it |
| // hasn't, we can just skip the next step. |
| if (g1h->free_regions_coming()) { |
| // The following will finish freeing up any regions that we |
| // found to be empty during cleanup. We'll do this part |
| // without joining the suspendible set. If an evacuation pause |
| // takes place, then we would carry on freeing regions in |
| // case they are needed by the pause. If a Full GC takes |
| // place, it would wait for us to process the regions |
| // reclaimed by cleanup. |
| |
| GCTraceConcTime(Info, gc) tt("Concurrent Cleanup"); |
| GCConcPhaseTimer(_cm, "Concurrent Cleanup"); |
| |
| // Now do the concurrent cleanup operation. |
| _cm->completeCleanup(); |
| |
| // Notify anyone who's waiting that there are no more free |
| // regions coming. We have to do this before we join the STS |
| // (in fact, we should not attempt to join the STS in the |
| // interval between finishing the cleanup pause and clearing |
| // the free_regions_coming flag) otherwise we might deadlock: |
| // a GC worker could be blocked waiting for the notification |
| // whereas this thread will be blocked for the pause to finish |
| // while it's trying to join the STS, which is conditional on |
| // the GC workers finishing. |
| g1h->reset_free_regions_coming(); |
| } |
| guarantee(cm()->cleanup_list_is_empty(), |
| "at this point there should be no regions on the cleanup list"); |
| |
| // There is a tricky race before recording that the concurrent |
| // cleanup has completed and a potential Full GC starting around |
| // the same time. We want to make sure that the Full GC calls |
| // abort() on concurrent mark after |
| // record_concurrent_mark_cleanup_completed(), since abort() is |
| // the method that will reset the concurrent mark state. If we |
| // end up calling record_concurrent_mark_cleanup_completed() |
| // after abort() then we might incorrectly undo some of the work |
| // abort() did. Checking the has_aborted() flag after joining |
| // the STS allows the correct ordering of the two methods. There |
| // are two scenarios: |
| // |
| // a) If we reach here before the Full GC, the fact that we have |
| // joined the STS means that the Full GC cannot start until we |
| // leave the STS, so record_concurrent_mark_cleanup_completed() |
| // will complete before abort() is called. |
| // |
| // b) If we reach here during the Full GC, we'll be held up from |
| // joining the STS until the Full GC is done, which means that |
| // abort() will have completed and has_aborted() will return |
| // true to prevent us from calling |
| // record_concurrent_mark_cleanup_completed() (and, in fact, it's |
| // not needed any more as the concurrent mark state has been |
| // already reset). |
| { |
| SuspendibleThreadSetJoiner sts_join; |
| if (!cm()->has_aborted()) { |
| g1_policy->record_concurrent_mark_cleanup_completed(); |
| } else { |
| log_info(gc)("Concurrent Mark abort"); |
| } |
| } |
| |
| // We now want to allow clearing of the marking bitmap to be |
| // suspended by a collection pause. |
| // We may have aborted just before the remark. Do not bother clearing the |
| // bitmap then, as it has been done during mark abort. |
| if (!cm()->has_aborted()) { |
| GCConcPhaseTimer(_cm, "Concurrent Bitmap Clearing"); |
| _cm->clearNextBitmap(); |
| } else { |
| assert(!G1VerifyBitmaps || _cm->nextMarkBitmapIsClear(), "Next mark bitmap must be clear"); |
| } |
| } |
| |
| // Update the number of full collections that have been |
| // completed. This will also notify the FullGCCount_lock in case a |
| // Java thread is waiting for a full GC to happen (e.g., it |
| // called System.gc() with +ExplicitGCInvokesConcurrent). |
| { |
| SuspendibleThreadSetJoiner sts_join; |
| g1h->increment_old_marking_cycles_completed(true /* concurrent */); |
| g1h->register_concurrent_cycle_end(); |
| } |
| } |
| } |
| |
| void ConcurrentMarkThread::stop() { |
| { |
| MutexLockerEx ml(Terminator_lock); |
| _should_terminate = true; |
| } |
| |
| stop_service(); |
| |
| { |
| MutexLockerEx ml(Terminator_lock); |
| while (!_has_terminated) { |
| Terminator_lock->wait(); |
| } |
| } |
| } |
| |
| void ConcurrentMarkThread::stop_service() { |
| MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag); |
| CGC_lock->notify_all(); |
| } |
| |
| void ConcurrentMarkThread::sleepBeforeNextCycle() { |
| // We join here because we don't want to do the "shouldConcurrentMark()" |
| // below while the world is otherwise stopped. |
| assert(!in_progress(), "should have been cleared"); |
| |
| MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); |
| while (!started() && !_should_terminate) { |
| CGC_lock->wait(Mutex::_no_safepoint_check_flag); |
| } |
| |
| if (started()) { |
| set_in_progress(); |
| } |
| } |
| |
| // Note: As is the case with CMS - this method, although exported |
| // by the ConcurrentMarkThread, which is a non-JavaThread, can only |
| // be called by a JavaThread. Currently this is done at vm creation |
| // time (post-vm-init) by the main/Primordial (Java)Thread. |
| // XXX Consider changing this in the future to allow the CM thread |
| // itself to create this thread? |
| void ConcurrentMarkThread::makeSurrogateLockerThread(TRAPS) { |
| assert(UseG1GC, "SLT thread needed only for concurrent GC"); |
| assert(THREAD->is_Java_thread(), "must be a Java thread"); |
| assert(_slt == NULL, "SLT already created"); |
| _slt = SurrogateLockerThread::make(THREAD); |
| } |