Oilpan: Split completeSweep() in idle tasks into chunks

Source/platform/heap/ThreadState.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 588 matching lines @@
     if (idleDeltaInSeconds <= Heap::estimatedMarkingTime() && !Scheduler::shared()->canExceedIdleDeadlineIfRequired()) {
         // If marking is estimated to take longer than the deadline and we can't
         // exceed the deadline, then reschedule for the next idle period.
         scheduleIdleGC();
         return;
     }
 
     Heap::collectGarbage(NoHeapPointersOnStack, GCWithoutSweep, Heap::IdleGC);
 }
 
-void ThreadState::performIdleCompleteSweep(double deadlineSeconds)
+void ThreadState::performIdleLazySweep(double deadlineSeconds)
 {
     ASSERT(isMainThread());
-    // The completeSweep() does nothing if the sweeping is already done.
-    // TODO(haraken): Split the sweeping task into chunks so that each chunk fits
-    // in the deadlineSeconds.
-    completeSweep();
+
+    // If we are not in a sweeping phase, there is nothing to do here.
+    if (!isSweepingInProgress())
+        return;
+
+    // This check is here to prevent performIdleLazySweep() from being called
+    // recursively. I'm not sure if it can happen but it would be safer to have
+    // the check just in case.
+    if (sweepForbidden())
+        return;
+
+    bool sweepCompleted = true;
+    ThreadState::SweepForbiddenScope scope(this);
+    {
+        if (isMainThread())
+            ScriptForbiddenScope::enter();
+
+        for (int i = 0; i < NumberOfHeaps; i++) {
+            // lazySweepWithDeadline() won't check the deadline until it sweeps
+            // 10 pages. So we give a small slack for safety.
+            double slack = 0.001;
+            double remainingBudget = deadlineSeconds - slack - Platform::current()->monotonicallyIncreasingTime();
+            if (remainingBudget <= 0 || !m_heaps[i]->lazySweepWithDeadline(deadlineSeconds)) {
+                // We couldn't finish the sweeping within the deadline.
+                // We request another idle task for the remaining sweeping.
+                scheduleIdleLazySweep();
+                sweepCompleted = false;
+                break;
+            }
+        }
+
+        if (isMainThread())
+            ScriptForbiddenScope::exit();
+    }
+
+    if (sweepCompleted)
+        postSweep();
 }
 
 void ThreadState::scheduleIdleGC()
 {
     // Idle GC is supported only in the main thread.
     if (!isMainThread())
         return;
 
     if (isSweepingInProgress()) {
         setGCState(SweepingAndIdleGCScheduled);
         return;
     }
 
     Scheduler::shared()->postNonNestableIdleTask(FROM_HERE, WTF::bind<double>(&ThreadState::performIdleGC, this));
     setGCState(IdleGCScheduled);
 }
 
-void ThreadState::scheduleIdleCompleteSweep()
+void ThreadState::scheduleIdleLazySweep()
 {
     // Idle complete sweep is supported only in the main thread.
     if (!isMainThread())
         return;
 
-    // TODO(haraken): Temporarily disable complete sweeping in idle tasks
-    // because it turned out that it has a risk of violating the idle task
-    // deadline and thus regressing queueing_durations. We'll enable this
-    // once we finish collecting performance numbers.
-#if 0
-    Scheduler::shared()->postIdleTask(FROM_HERE, WTF::bind<double>(&ThreadState::performIdleCompleteSweep, this));
+    // TODO(haraken): Remove this. Lazy sweeping is not yet enabled in non-oilpan builds.
+#if ENABLE(OILPAN)
+    Scheduler::shared()->postIdleTask(FROM_HERE, WTF::bind<double>(&ThreadState::performIdleLazySweep, this));
 #endif
 }
 
 void ThreadState::schedulePreciseGC()
 {
     if (isSweepingInProgress()) {
         setGCState(SweepingAndPreciseGCScheduled);
         return;
     }
 
@@ skipping 122 matching lines @@
         return;
 
     // completeSweep() can be called recursively if finalizers can allocate
     // memory and the allocation triggers completeSweep(). This check prevents
     // the sweeping from being executed recursively.
     if (sweepForbidden())
         return;
 
     ThreadState::SweepForbiddenScope scope(this);
     {
+        if (isMainThread())
+            ScriptForbiddenScope::enter();
+
         TRACE_EVENT0("blink_gc", "ThreadState::completeSweep");
         double timeStamp = WTF::currentTimeMS();
 
         for (int i = 0; i < NumberOfHeaps; i++)
             m_heaps[i]->completeSweep();
 
         if (Platform::current()) {
             Platform::current()->histogramCustomCounts("BlinkGC.CompleteSweep", WTF::currentTimeMS() - timeStamp, 0, 10 * 1000, 50);
         }
+
+        if (isMainThread())
+            ScriptForbiddenScope::exit();
     }
 
+    postSweep();
+}
+
+void ThreadState::postSweep()
+{
     if (isMainThread() && m_allocatedObjectSizeBeforeGC) {
         // FIXME: Heap::markedObjectSize() may not be accurate because other
         // threads may not have finished sweeping.
         m_collectionRate = 1.0 * Heap::markedObjectSize() / m_allocatedObjectSizeBeforeGC;
         ASSERT(m_collectionRate >= 0);
 
         // The main thread might be at a safe point, with other
         // threads leaving theirs and accumulating marked object size
         // while continuing to sweep. That accumulated size might end up
         // exceeding what the main thread sampled in preGC() (recorded
@@ skipping 241 matching lines @@
     }
 
 #if ENABLE(OILPAN)
     if (gcState() == EagerSweepScheduled) {
         // Eager sweeping should happen only in testing.
         setGCState(Sweeping);
         completeSweep();
     } else {
         // The default behavior is lazy sweeping.
         setGCState(Sweeping);
-        scheduleIdleCompleteSweep();
+        scheduleIdleLazySweep();
     }
 #else
     // FIXME: For now, we disable lazy sweeping in non-oilpan builds
     // to avoid unacceptable behavior regressions on trunk.
     setGCState(Sweeping);
     completeSweep();
 #endif
 
 #if ENABLE(GC_PROFILING)
     snapshotFreeListIfNecessary();
@@ skipping 196 matching lines @@
         json->beginArray(it->key.ascii().data());
         for (size_t age = 0; age <= maxHeapObjectAge; ++age)
             json->pushInteger(it->value.ages[age]);
         json->endArray();
     }
     TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(TRACE_DISABLED_BY_DEFAULT("blink_gc"), statsName, this, json.release());
 }
 #endif
 
 } // namespace blink