Bug 937960, part 3 - Pass in a small time budget with ICC. r=smaug

dom/base/nsJSEnvironment.cpp

@@ -124,6 +124,12 @@ static PRLogModuleInfo* gJSDiagnostics;
 // Maximum amount of time that should elapse between incremental CC slices
 static const int64_t kICCIntersliceDelay = 32; // ms
 
+// Time budget for an incremental CC slice
+static const int64_t kICCSliceBudget = 10; // ms
+
+// Maximum total duration for an ICC
+static const uint32_t kMaxICCDuration = 2000; // ms
+
 // Force a CC after this long if there's more than NS_CC_FORCED_PURPLE_LIMIT
 // objects in the purple buffer.
 #define NS_CC_FORCED                (2 * 60 * PR_USEC_PER_SEC) // 2 min
@@ -2019,6 +2025,22 @@ struct CycleCollectorStats
 
 CycleCollectorStats gCCStats;
 
+static int64_t
+ICCSliceTime()
+{
+  // If CC is not incremental, use an unlimited budget.
+  if (!sIncrementalCC) {
+    return -1;
+  }
+
+  // If an ICC is in progress and is taking too long, finish it off.
+  if (gCCStats.mBeginTime != 0 &&
+      TimeBetween(gCCStats.mBeginTime, PR_Now()) >= kMaxICCDuration) {
+    return -1;
+  }
+
+  return kICCSliceBudget;
+}
 
 static void
 PrepareForCycleCollection(int32_t aExtraForgetSkippableCalls = 0)
@@ -2076,15 +2098,18 @@ nsJSContext::CycleCollectNow(nsICycleCollectorListener *aListener,
 
 //static
 void
-nsJSContext::ScheduledCycleCollectNow()
+nsJSContext::ScheduledCycleCollectNow(int64_t aSliceTime)
 {
   if (!NS_IsMainThread()) {
     return;
   }
 
   PROFILER_LABEL("CC", "ScheduledCycleCollectNow");
+
+  // Ideally, the slice time would be decreased by the amount of
+  // time spent on PrepareForCycleCollection().
   PrepareForCycleCollection();
-  nsCycleCollector_scheduledCollect();
+  nsCycleCollector_scheduledCollect(aSliceTime);
 }
 
 static void
@@ -2108,7 +2133,7 @@ ICCTimerFired(nsITimer* aTimer, void* aClosure)
     }
   }
 
-  nsJSContext::ScheduledCycleCollectNow();
+  nsJSContext::ScheduledCycleCollectNow(ICCSliceTime());
 }
 
 //static
@@ -2359,7 +2384,7 @@ CCTimerFired(nsITimer *aTimer, void *aClosure)
       // We are in the final timer fire and still meet the conditions for
       // triggering a CC. Let CycleCollectNow finish the current IGC, if any,
       // because that will allow us to include the GC time in the CC pause.
-      nsJSContext::ScheduledCycleCollectNow();
+      nsJSContext::ScheduledCycleCollectNow(ICCSliceTime());
     }
   } else if ((sPreviousSuspectedCount + 100) <= suspected) {
       // Only do a forget skippable if there are more than a few new objects.

dom/base/nsJSEnvironment.h

@@ -101,11 +101,17 @@ public:
                                 IsShrinking aShrinking = NonShrinkingGC,
                                 int64_t aSliceMillis = 0);
   static void ShrinkGCBuffersNow();
+
   // If aExtraForgetSkippableCalls is -1, forgetSkippable won't be
   // called even if the previous collection was GC.
   static void CycleCollectNow(nsICycleCollectorListener *aListener = nullptr,
                               int32_t aExtraForgetSkippableCalls = 0);
-  static void ScheduledCycleCollectNow();
+
+  // If aSliceTime is negative, the CC will run to completion.  If aSliceTime
+  // is 0, only a minimum quantum of work will be done.  Otherwise, aSliceTime
+  // will be used as the time budget for the slice, in ms.
+  static void ScheduledCycleCollectNow(int64_t aSliceTime);
+
   static void BeginCycleCollectionCallback();
   static void EndCycleCollectionCallback(mozilla::CycleCollectorResults &aResults);
 

xpcom/base/nsCycleCollector.cpp

@@ -3056,7 +3056,8 @@ nsCycleCollector::Collect(ccType aCCType,
 // don't want to abandon the current CC, because the graph contains
 // information about purple roots. So we synchronously finish off
 // the current CC.
-void nsCycleCollector::PrepareForGarbageCollection()
+void
+nsCycleCollector::PrepareForGarbageCollection()
 {
     if (mIncrementalPhase == IdlePhase) {
         MOZ_ASSERT(mGraph.IsEmpty(), "Non-empty graph when idle");
@@ -3551,7 +3552,7 @@ nsCycleCollector_collect(nsICycleCollectorListener *aManualListener)
 }
 
 void
-nsCycleCollector_scheduledCollect()
+nsCycleCollector_scheduledCollect(int64_t aSliceTime)
 {
     CollectorData *data = sCollectorData.get();
 
@@ -3560,8 +3561,13 @@ nsCycleCollector_scheduledCollect()
     MOZ_ASSERT(data->mCollector);
 
     PROFILER_LABEL("CC", "nsCycleCollector_scheduledCollect");
-    SliceBudget unlimitedBudget;
-    data->mCollector->Collect(ScheduledCC, unlimitedBudget, nullptr);
+    SliceBudget budget;
+    if (aSliceTime > 0) {
+        budget = SliceBudget::TimeBudget(aSliceTime);
+    } else if (aSliceTime == 0) {
+        budget = SliceBudget::WorkBudget(1);
+    }
+    data->mCollector->Collect(ScheduledCC, budget, nullptr);
 }
 
 void

xpcom/base/nsCycleCollector.h

@@ -41,7 +41,11 @@ void nsCycleCollector_dispatchDeferredDeletion(bool aContinuation = false);
 bool nsCycleCollector_doDeferredDeletion();
 
 void nsCycleCollector_collect(nsICycleCollectorListener *aManualListener);
-void nsCycleCollector_scheduledCollect();
+
+// If aSliceTime is negative, the CC will run to completion.  If aSliceTime
+// is 0, only a minimum quantum of work will be done.  Otherwise, aSliceTime
+// will be used as the time budget for the slice, in ms.
+void nsCycleCollector_scheduledCollect(int64_t aSliceTime);
 
 uint32_t nsCycleCollector_suspectedCount();
 void nsCycleCollector_shutdown();