Bug 415025, try to improve CC scheduling, r=peterv, sr=jst

dom/src/base/nsJSEnvironment.cpp

@@ -160,6 +160,16 @@ static PRLogModuleInfo* gJSDiagnostics;
 #define NS_PROBABILITY_MULTIPLIER   3
 // Cycle collector should never run more often than this value
 #define NS_MIN_CC_INTERVAL          10000 // ms
+// If previous cycle collection collected more than this number of objects,
+// the next collection will happen somewhat soon.
+#define NS_COLLECTED_OBJECTS_LIMIT  5000
+// CC will be called if GC has been called at least this number of times and
+// there are at least NS_MIN_SUSPECT_CHANGES new suspected objects.
+#define NS_MAX_GC_COUNT             5
+#define NS_MIN_SUSPECT_CHANGES      10
+// CC will be called if there are at least NS_MAX_SUSPECT_CHANGES new suspected
+// objects.
+#define NS_MAX_SUSPECT_CHANGES      100
 
 // if you add statics here, add them to the list in nsJSRuntime::Startup
 
@@ -167,7 +177,10 @@ static PRUint32 sDelayedCCollectCount;
 static PRUint32 sCCollectCount;
 static PRBool sUserIsActive;
 static PRTime sPreviousCCTime;
-static PRBool sPreviousCCDidCollect;
+static PRUint32 sCollectedObjectsCounts;
+static PRUint32 sGCCount;
+static PRUint32 sCCSuspectChanges;
+static PRUint32 sCCSuspectedCount;
 static nsITimer *sGCTimer;
 static PRBool sReadyForGC;
 
@@ -839,6 +852,7 @@ MaybeGC(JSContext *cx)
       || cx->runtime->gcZeal > 0
 #endif
       ) {
+    ++sGCCount;
     JS_GC(cx);
   }
 }
@@ -3317,19 +3331,22 @@ nsJSContext::PreserveWrapper(nsIXPConnectWrappedNative *aWrapper)
 void
 nsJSContext::CC()
 {
-  sPreviousCCTime = PR_Now();
-  sDelayedCCollectCount = 0;
   ++sCCollectCount;
 #ifdef DEBUG_smaug
-  printf("Will run cycle collector (%i)\n", sCCollectCount);
+  printf("Will run cycle collector (%i), %lldms since previous.\n",
+         sCCollectCount, (PR_Now() - sPreviousCCTime) / PR_USEC_PER_MSEC);
 #endif
+  sPreviousCCTime = PR_Now();
+  sDelayedCCollectCount = 0;
+  sGCCount = 0;
+  sCCSuspectChanges = 0;
   // nsCycleCollector_collect() will run a ::JS_GC() indirectly, so
   // we do not explicitly call ::JS_GC() here.
-  sPreviousCCDidCollect = nsCycleCollector_collect();
+  sCollectedObjectsCounts = nsCycleCollector_collect();
+  sCCSuspectedCount = nsCycleCollector_suspectedCount();
 #ifdef DEBUG_smaug
-  printf("(1) %s\n", sPreviousCCDidCollect ?
-                     "Cycle collector did collect nodes" :
-                     "Cycle collector did not collect nodes");
+  printf("Collected %u objects, %u suspected objects\n",
+         sCollectedObjectsCounts, sCCSuspectedCount);
 #endif
 }
 
@@ -3338,13 +3355,42 @@ PRBool
 nsJSContext::MaybeCC(PRBool aHigherProbability)
 {
   ++sDelayedCCollectCount;
+
+  // Don't check suspected count if CC will be called anyway.
+  if (sCCSuspectChanges <= NS_MIN_SUSPECT_CHANGES ||
+      sGCCount <= NS_MAX_GC_COUNT) {
+#ifdef DEBUG_smaug
+    PRTime now = PR_Now();
+#endif
+    PRUint32 suspected = nsCycleCollector_suspectedCount();
+#ifdef DEBUG_smaug
+    printf("%u suspected objects (%lldms), sCCSuspectedCount %u\n",
+            suspected, (PR_Now() - now) / PR_USEC_PER_MSEC,
+            sCCSuspectedCount);
+#endif
+    // Update only when suspected count has increased.
+    if (suspected > sCCSuspectedCount) {
+      sCCSuspectChanges += (suspected - sCCSuspectedCount);
+      sCCSuspectedCount = suspected;
+    }
+  }
+#ifdef DEBUG_smaug
+  printf("sCCSuspectChanges %u, sGCCount %u\n",
+         sCCSuspectChanges, sGCCount);
+#endif
+
   // Increase the probability also if the previous call to cycle collector
   // collected something.
-  if (aHigherProbability || sPreviousCCDidCollect) {
+  if (aHigherProbability ||
+      sCollectedObjectsCounts > NS_COLLECTED_OBJECTS_LIMIT) {
     sDelayedCCollectCount *= NS_PROBABILITY_MULTIPLIER;
   }
 
-  if (!sGCTimer && (sDelayedCCollectCount > NS_MAX_DELAYED_CCOLLECT)) {
+  if (!sGCTimer &&
+      (sDelayedCCollectCount > NS_MAX_DELAYED_CCOLLECT) &&
+      ((sCCSuspectChanges > NS_MIN_SUSPECT_CHANGES &&
+        sGCCount > NS_MAX_GC_COUNT) ||
+       (sCCSuspectChanges > NS_MAX_SUSPECT_CHANGES))) {
     if ((PR_Now() - sPreviousCCTime) >=
         PRTime(NS_MIN_CC_INTERVAL * PR_USEC_PER_MSEC)) {
       nsJSContext::CC();
@@ -3559,7 +3605,10 @@ nsJSRuntime::Startup()
   sCCollectCount = 0;
   sUserIsActive = PR_FALSE;
   sPreviousCCTime = 0;
-  sPreviousCCDidCollect = PR_FALSE;
+  sCollectedObjectsCounts = 0;
+  sGCCount = 0;
+  sCCSuspectChanges = 0;
+  sCCSuspectedCount = 0;
   sGCTimer = nsnull;
   sReadyForGC = PR_FALSE;
   sLoadInProgressGCTimer = PR_FALSE;

xpcom/base/nsCycleCollector.cpp

@@ -763,6 +763,17 @@ struct nsPurpleBuffer
             }
         }
     }
+
+    PRUint32 Count()
+    {
+        PRUint32 count = mBackingStore.Count();
+        for (PRUint32 i = 0; i < N_POINTERS; ++i) {
+            if (mCache[i]) {
+                ++count;
+            }
+        }
+        return count;
+    }
 };
 
 static PR_CALLBACK PLDHashOperator
@@ -867,6 +878,7 @@ struct nsCycleCollector
     PRBool mCollectionInProgress;
     PRBool mScanInProgress;
     PRBool mFollowupCollection;
+    PRUint32 mCollectedObjects;
 
     nsCycleCollectionLanguageRuntime *mRuntimes[nsIProgrammingLanguage::MAX+1];
     nsCycleCollectionXPCOMRuntime mXPCOMRuntime;
@@ -895,9 +907,10 @@ struct nsCycleCollector
 
     PRBool Suspect(nsISupports *n);
     PRBool Forget(nsISupports *n);
-    PRBool Collect(PRUint32 aTryCollections = 1);
+    PRUint32 Collect(PRUint32 aTryCollections = 1);
     PRBool BeginCollection();
     PRBool FinishCollection();
+    PRUint32 SuspectedCount();
     void Shutdown();
 
     void ClearGraph()
@@ -1613,6 +1626,7 @@ nsCycleCollector::CollectWhite()
         mStats.mFreedBytes += (ms1.lTotalCount - ms2.lTotalCount);
 #endif
 
+    mCollectedObjects += count;
     return count > 0;
 }
 
@@ -1818,6 +1832,7 @@ InitMemHook(void)
 nsCycleCollector::nsCycleCollector() : 
     mCollectionInProgress(PR_FALSE),
     mScanInProgress(PR_FALSE),
+    mCollectedObjects(0),
     mWhiteNodes(nsnull),
     mWhiteNodeCount(0),
 #ifdef DEBUG_CC
@@ -2138,7 +2153,7 @@ nsCycleCollector::Freed(void *n)
 }
 #endif
 
-PRBool
+PRUint32
 nsCycleCollector::Collect(PRUint32 aTryCollections)
 {
 #if defined(DEBUG_CC) && !defined(__MINGW32__)
@@ -2148,7 +2163,7 @@ nsCycleCollector::Collect(PRUint32 aTryCollections)
 
     // This can legitimately happen in a few cases. See bug 383651.
     if (mCollectionInProgress)
-        return PR_FALSE;
+        return 0;
 
 #ifdef COLLECT_TIME_DEBUG
     printf("cc: Starting nsCycleCollector::Collect(%d)\n", aTryCollections);
@@ -2164,7 +2179,7 @@ nsCycleCollector::Collect(PRUint32 aTryCollections)
     }
 
     mFollowupCollection = PR_FALSE;
-
+    mCollectedObjects = 0;
     nsAutoTPtrArray<PtrInfo, 4000> whiteNodes;
     mWhiteNodes = &whiteNodes;
 
@@ -2224,7 +2239,7 @@ nsCycleCollector::Collect(PRUint32 aTryCollections)
 #ifdef DEBUG_CC
     ExplainLiveExpectedGarbage();
 #endif
-    return totalCollections > 0;
+    return mCollectedObjects;
 }
 
 PRBool
@@ -2340,7 +2355,7 @@ nsCycleCollector::BeginCollection()
         RootWhite();
 
 #ifdef COLLECT_TIME_DEBUG
-        printf("cc: CollectWhite() took %lldms\n",
+        printf("cc: RootWhite() took %lldms\n",
                (PR_Now() - now) / PR_USEC_PER_MSEC);
 #endif
     }
@@ -2354,8 +2369,16 @@ nsCycleCollector::BeginCollection()
 PRBool
 nsCycleCollector::FinishCollection()
 {
+#ifdef COLLECT_TIME_DEBUG
+    PRTime now = PR_Now();
+#endif
     PRBool collected = CollectWhite();
 
+#ifdef COLLECT_TIME_DEBUG
+    printf("cc: CollectWhite() took %lldms\n",
+           (PR_Now() - now) / PR_USEC_PER_MSEC);
+#endif
+
 #ifdef DEBUG_CC
     mStats.mCollection++;
     if (mParams.mReportStats)
@@ -2372,6 +2395,12 @@ nsCycleCollector::FinishCollection()
     return collected;
 }
 
+PRUint32
+nsCycleCollector::SuspectedCount()
+{
+    return mPurpleBuf.Count();
+}
+
 void
 nsCycleCollector::Shutdown()
 {
@@ -2780,10 +2809,16 @@ NS_CycleCollectorForget(nsISupports *n)
 }
 
 
-PRBool
+PRUint32
 nsCycleCollector_collect()
 {
-    return sCollector ? sCollector->Collect() : PR_FALSE;
+    return sCollector ? sCollector->Collect() : 0;
+}
+
+PRUint32
+nsCycleCollector_suspectedCount()
+{
+    return sCollector ? sCollector->SuspectedCount() : 0;
 }
 
 PRBool 

xpcom/base/nsCycleCollector.h

@@ -60,8 +60,9 @@ struct nsCycleCollectionLanguageRuntime
 };
 
 nsresult nsCycleCollector_startup();
-// Returns PR_TRUE if some nodes were collected.
-NS_COM PRBool nsCycleCollector_collect();
+// Returns the number of collected nodes.
+NS_COM PRUint32 nsCycleCollector_collect();
+NS_COM PRUint32 nsCycleCollector_suspectedCount();
 void nsCycleCollector_shutdown();
 
 // The JS runtime is special, it needs to call cycle collection during its GC.