/* * Copyright (c) 2001, 2012, 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 "gc_implementation/g1/concurrentMarkThread.inline.hpp" #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" #include "gc_implementation/g1/g1CollectorPolicy.hpp" #include "gc_implementation/g1/g1MMUTracker.hpp" #include "gc_implementation/g1/vm_operations_g1.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(ConcurrentMark* cm) : ConcurrentGCThread(), _cm(cm), _started(false), _in_progress(false), _vtime_accum(0.0), _vtime_mark_accum(0.0) { create_and_start(); } class CMCheckpointRootsFinalClosure: public VoidClosure { ConcurrentMark* _cm; public: CMCheckpointRootsFinalClosure(ConcurrentMark* cm) : _cm(cm) {} void do_void(){ _cm->checkpointRootsFinal(false); // !clear_all_soft_refs } }; class CMCleanUp: public VoidClosure { ConcurrentMark* _cm; public: CMCleanUp(ConcurrentMark* cm) : _cm(cm) {} void do_void(){ _cm->cleanup(); } }; void ConcurrentMarkThread::run() { initialize_in_thread(); _vtime_start = os::elapsedVTime(); wait_for_universe_init(); G1CollectedHeap* g1h = G1CollectedHeap::heap(); G1CollectorPolicy* g1_policy = g1h->g1_policy(); G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker(); Thread *current_thread = Thread::current(); while (!_should_terminate) { // wait until started is set. sleepBeforeNextCycle(); { ResourceMark rm; HandleMark hm; double cycle_start = os::elapsedVTime(); char verbose_str[128]; // 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. double scan_start = os::elapsedTime(); if (!cm()->has_aborted()) { if (PrintGC) { gclog_or_tty->date_stamp(PrintGCDateStamps); gclog_or_tty->stamp(PrintGCTimeStamps); gclog_or_tty->print_cr("[GC concurrent-root-region-scan-start]"); } _cm->scanRootRegions(); double scan_end = os::elapsedTime(); if (PrintGC) { gclog_or_tty->date_stamp(PrintGCDateStamps); gclog_or_tty->stamp(PrintGCTimeStamps); gclog_or_tty->print_cr("[GC concurrent-root-region-scan-end, %1.7lf]", scan_end - scan_start); } } double mark_start_sec = os::elapsedTime(); if (PrintGC) { gclog_or_tty->date_stamp(PrintGCDateStamps); gclog_or_tty->stamp(PrintGCTimeStamps); gclog_or_tty->print_cr("[GC concurrent-mark-start]"); } int iter = 0; do { iter++; if (!cm()->has_aborted()) { _cm->markFromRoots(); } double mark_end_time = os::elapsedVTime(); double mark_end_sec = os::elapsedTime(); _vtime_mark_accum += (mark_end_time - cycle_start); if (!cm()->has_aborted()) { if (g1_policy->adaptive_young_list_length()) { double now = os::elapsedTime(); double remark_prediction_ms = g1_policy->predict_remark_time_ms(); jlong sleep_time_ms = mmu_tracker->when_ms(now, remark_prediction_ms); os::sleep(current_thread, sleep_time_ms, false); } if (PrintGC) { gclog_or_tty->date_stamp(PrintGCDateStamps); gclog_or_tty->stamp(PrintGCTimeStamps); gclog_or_tty->print_cr("[GC concurrent-mark-end, %1.7lf sec]", mark_end_sec - mark_start_sec); } CMCheckpointRootsFinalClosure final_cl(_cm); sprintf(verbose_str, "GC remark"); VM_CGC_Operation op(&final_cl, verbose_str); VMThread::execute(&op); } if (cm()->restart_for_overflow() && G1TraceMarkStackOverflow) { gclog_or_tty->print_cr("Restarting conc marking because of MS overflow " "in remark (restart #%d).", iter); } if (cm()->restart_for_overflow()) { if (PrintGC) { gclog_or_tty->date_stamp(PrintGCDateStamps); gclog_or_tty->stamp(PrintGCTimeStamps); gclog_or_tty->print_cr("[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()) { if (g1_policy->adaptive_young_list_length()) { double now = os::elapsedTime(); double cleanup_prediction_ms = g1_policy->predict_cleanup_time_ms(); jlong sleep_time_ms = mmu_tracker->when_ms(now, cleanup_prediction_ms); os::sleep(current_thread, sleep_time_ms, false); } CMCleanUp cl_cl(_cm); sprintf(verbose_str, "GC cleanup"); VM_CGC_Operation op(&cl_cl, verbose_str); VMThread::execute(&op); } else { // We don't want to update the marking status if a GC pause // is already underway. _sts.join(); g1h->set_marking_complete(); _sts.leave(); } // 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. double cleanup_start_sec = os::elapsedTime(); if (PrintGC) { gclog_or_tty->date_stamp(PrintGCDateStamps); gclog_or_tty->stamp(PrintGCTimeStamps); gclog_or_tty->print_cr("[GC concurrent-cleanup-start]"); } // 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(); double cleanup_end_sec = os::elapsedTime(); if (PrintGC) { gclog_or_tty->date_stamp(PrintGCDateStamps); gclog_or_tty->stamp(PrintGCTimeStamps); gclog_or_tty->print_cr("[GC concurrent-cleanup-end, %1.7lf]", cleanup_end_sec - cleanup_start_sec); } } 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). _sts.join(); if (!cm()->has_aborted()) { g1_policy->record_concurrent_mark_cleanup_completed(); } _sts.leave(); if (cm()->has_aborted()) { if (PrintGC) { gclog_or_tty->date_stamp(PrintGCDateStamps); gclog_or_tty->stamp(PrintGCTimeStamps); gclog_or_tty->print_cr("[GC concurrent-mark-abort]"); } } // We now want to allow clearing of the marking bitmap to be // suspended by a collection pause. _sts.join(); _cm->clearNextBitmap(); _sts.leave(); } // 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). _sts.join(); g1h->increment_full_collections_completed(true /* concurrent */); _sts.leave(); } assert(_should_terminate, "just checking"); terminate(); } void ConcurrentMarkThread::yield() { _sts.yield("Concurrent Mark"); } void ConcurrentMarkThread::stop() { // it is ok to take late safepoints here, if needed MutexLockerEx mu(Terminator_lock); _should_terminate = true; while (!_has_terminated) { Terminator_lock->wait(); } } void ConcurrentMarkThread::print() const { print_on(tty); } void ConcurrentMarkThread::print_on(outputStream* st) const { st->print("\"G1 Main Concurrent Mark GC Thread\" "); Thread::print_on(st); st->cr(); } 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()) { CGC_lock->wait(Mutex::_no_safepoint_check_flag); } set_in_progress(); clear_started(); } // 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); }