--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/concurrentMarkThread.cpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,470 @@
+/*
+ * Copyright (c) 2001, 2017, 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/g1Analytics.hpp"
+#include "gc/g1/g1CollectedHeap.inline.hpp"
+#include "gc/g1/g1ConcurrentMark.inline.hpp"
+#include "gc/g1/g1MMUTracker.hpp"
+#include "gc/g1/g1Policy.hpp"
+#include "gc/g1/suspendibleThreadSet.hpp"
+#include "gc/g1/vm_operations_g1.hpp"
+#include "gc/shared/concurrentGCPhaseManager.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"
+#include "utilities/debug.hpp"
+
+// ======= Concurrent Mark Thread ========
+
+// Check order in EXPAND_CURRENT_PHASES
+STATIC_ASSERT(ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE <
+ ConcurrentGCPhaseManager::IDLE_PHASE);
+
+#define EXPAND_CONCURRENT_PHASES(expander) \
+ expander(ANY, = ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE, NULL) \
+ expander(IDLE, = ConcurrentGCPhaseManager::IDLE_PHASE, NULL) \
+ expander(CONCURRENT_CYCLE,, "Concurrent Cycle") \
+ expander(CLEAR_CLAIMED_MARKS,, "Concurrent Clear Claimed Marks") \
+ expander(SCAN_ROOT_REGIONS,, "Concurrent Scan Root Regions") \
+ expander(CONCURRENT_MARK,, "Concurrent Mark") \
+ expander(MARK_FROM_ROOTS,, "Concurrent Mark From Roots") \
+ expander(BEFORE_REMARK,, NULL) \
+ expander(REMARK,, NULL) \
+ expander(CREATE_LIVE_DATA,, "Concurrent Create Live Data") \
+ expander(COMPLETE_CLEANUP,, "Concurrent Complete Cleanup") \
+ expander(CLEANUP_FOR_NEXT_MARK,, "Concurrent Cleanup for Next Mark") \
+ /* */
+
+class G1ConcurrentPhase : public AllStatic {
+public:
+ enum {
+#define CONCURRENT_PHASE_ENUM(tag, value, ignore_title) tag value,
+ EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_ENUM)
+#undef CONCURRENT_PHASE_ENUM
+ PHASE_ID_LIMIT
+ };
+};
+
+// The CM thread is created when the G1 garbage collector is used
+
+ConcurrentMarkThread::ConcurrentMarkThread(G1ConcurrentMark* cm) :
+ ConcurrentGCThread(),
+ _cm(cm),
+ _state(Idle),
+ _phase_manager_stack(),
+ _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(G1Policy* g1_policy, bool remark) {
+ const G1Analytics* analytics = g1_policy->analytics();
+ if (g1_policy->adaptive_young_list_length()) {
+ double now = os::elapsedTime();
+ double prediction_ms = remark ? analytics->predict_remark_time_ms()
+ : analytics->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 G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
+ G1ConcurrentMark* _cm;
+
+ public:
+ G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
+ GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title),
+ _cm(cm)
+ {
+ _cm->gc_timer_cm()->register_gc_concurrent_start(title);
+ }
+
+ ~G1ConcPhaseTimer() {
+ _cm->gc_timer_cm()->register_gc_concurrent_end();
+ }
+};
+
+static const char* const concurrent_phase_names[] = {
+#define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag),
+ EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME)
+#undef CONCURRENT_PHASE_NAME
+ NULL // terminator
+};
+// Verify dense enum assumption. +1 for terminator.
+STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 ==
+ ARRAY_SIZE(concurrent_phase_names));
+
+// Returns the phase number for name, or a negative value if unknown.
+static int lookup_concurrent_phase(const char* name) {
+ const char* const* names = concurrent_phase_names;
+ for (uint i = 0; names[i] != NULL; ++i) {
+ if (strcmp(name, names[i]) == 0) {
+ return static_cast<int>(i);
+ }
+ }
+ return -1;
+}
+
+// The phase must be valid and must have a title.
+static const char* lookup_concurrent_phase_title(int phase) {
+ static const char* const titles[] = {
+#define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title,
+ EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE)
+#undef CONCURRENT_PHASE_TITLE
+ };
+ // Verify dense enum assumption.
+ STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles));
+
+ assert(0 <= phase, "precondition");
+ assert((uint)phase < ARRAY_SIZE(titles), "precondition");
+ const char* title = titles[phase];
+ assert(title != NULL, "precondition");
+ return title;
+}
+
+class G1ConcPhaseManager : public StackObj {
+ G1ConcurrentMark* _cm;
+ ConcurrentGCPhaseManager _manager;
+
+public:
+ G1ConcPhaseManager(int phase, ConcurrentMarkThread* thread) :
+ _cm(thread->cm()),
+ _manager(phase, thread->phase_manager_stack())
+ { }
+
+ ~G1ConcPhaseManager() {
+ // Deactivate the manager if marking aborted, to avoid blocking on
+ // phase exit when the phase has been requested.
+ if (_cm->has_aborted()) {
+ _manager.deactivate();
+ }
+ }
+
+ void set_phase(int phase, bool force) {
+ _manager.set_phase(phase, force);
+ }
+};
+
+// Combine phase management and timing into one convenient utility.
+class G1ConcPhase : public StackObj {
+ G1ConcPhaseTimer _timer;
+ G1ConcPhaseManager _manager;
+
+public:
+ G1ConcPhase(int phase, ConcurrentMarkThread* thread) :
+ _timer(thread->cm(), lookup_concurrent_phase_title(phase)),
+ _manager(phase, thread)
+ { }
+};
+
+const char* const* ConcurrentMarkThread::concurrent_phases() const {
+ return concurrent_phase_names;
+}
+
+bool ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) {
+ int phase = lookup_concurrent_phase(phase_name);
+ if (phase < 0) return false;
+
+ while (!ConcurrentGCPhaseManager::wait_for_phase(phase,
+ phase_manager_stack())) {
+ assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed");
+ if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) {
+ // If idle and the goal is !idle, start a collection.
+ G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark);
+ }
+ }
+ return true;
+}
+
+void ConcurrentMarkThread::run_service() {
+ _vtime_start = os::elapsedVTime();
+
+ G1CollectedHeap* g1h = G1CollectedHeap::heap();
+ G1Policy* g1_policy = g1h->g1_policy();
+
+ G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this);
+
+ while (!should_terminate()) {
+ // wait until started is set.
+ sleepBeforeNextCycle();
+ if (should_terminate()) {
+ break;
+ }
+
+ cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */);
+
+ GCIdMark gc_id_mark;
+
+ cm()->concurrent_cycle_start();
+
+ assert(GCId::current() != GCId::undefined(), "GC id should have been set up by the initial mark GC.");
+
+ GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
+ {
+ ResourceMark rm;
+ HandleMark hm;
+ double cycle_start = os::elapsedVTime();
+
+ {
+ G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this);
+ 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.
+
+ {
+ G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this);
+ _cm->scan_root_regions();
+ }
+
+ // It would be nice to use the G1ConcPhase class here but
+ // the "end" logging is inside the loop and not at the end of
+ // a scope. Also, the timer doesn't support nesting.
+ // Mimicking the same log output instead.
+ {
+ G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this);
+ jlong mark_start = os::elapsed_counter();
+ const char* cm_title =
+ lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK);
+ log_info(gc, marking)("%s (%.3fs)",
+ cm_title,
+ TimeHelper::counter_to_seconds(mark_start));
+ for (uint iter = 1; !cm()->has_aborted(); ++iter) {
+ // Concurrent marking.
+ {
+ G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this);
+ _cm->mark_from_roots();
+ }
+ if (cm()->has_aborted()) break;
+
+ // Provide a control point after mark_from_roots.
+ {
+ G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this);
+ }
+ if (cm()->has_aborted()) break;
+
+ // Delay remark pause for MMU.
+ double mark_end_time = os::elapsedVTime();
+ jlong mark_end = os::elapsed_counter();
+ _vtime_mark_accum += (mark_end_time - cycle_start);
+ delay_to_keep_mmu(g1_policy, true /* remark */);
+ if (cm()->has_aborted()) break;
+
+ // Pause Remark.
+ log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms",
+ cm_title,
+ TimeHelper::counter_to_seconds(mark_start),
+ TimeHelper::counter_to_seconds(mark_end),
+ TimeHelper::counter_to_millis(mark_end - mark_start));
+ mark_manager.set_phase(G1ConcurrentPhase::REMARK, false);
+ CMCheckpointRootsFinalClosure final_cl(_cm);
+ VM_CGC_Operation op(&final_cl, "Pause Remark");
+ VMThread::execute(&op);
+ if (cm()->has_aborted()) {
+ break;
+ } else if (!cm()->restart_for_overflow()) {
+ break; // Exit loop if no restart requested.
+ } else {
+ // Loop to restart for overflow.
+ mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false);
+ log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)",
+ cm_title, iter);
+ }
+ }
+ }
+
+ if (!cm()->has_aborted()) {
+ G1ConcPhase p(G1ConcurrentPhase::CREATE_LIVE_DATA, this);
+ cm()->create_live_data();
+ }
+
+ 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");
+ 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.
+
+ // Now do the concurrent cleanup operation.
+ G1ConcPhase p(G1ConcurrentPhase::COMPLETE_CLEANUP, this);
+ _cm->complete_cleanup();
+
+ // 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, marking)("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()) {
+ G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this);
+ _cm->cleanup_for_next_mark();
+ } 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 */);
+
+ cm()->concurrent_cycle_end();
+ }
+
+ cpmanager.set_phase(G1ConcurrentPhase::IDLE, cm()->has_aborted() /* force */);
+ }
+ _cm->root_regions()->cancel_scan();
+}
+
+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();
+ }
+}