Bug 1052793, part 1 - Do per-zone GC for CC_WAITING triggers. r=smaug

dom/base/nsJSEnvironment.cpp

@@ -178,6 +178,7 @@ static uint32_t sForgetSkippableBeforeCC = 0;
 static uint32_t sPreviousSuspectedCount = 0;
 static uint32_t sCleanupsSinceLastGC = UINT32_MAX;
 static bool sNeedsFullCC = false;
+static bool sNeedsFullGC = false;
 static bool sNeedsGCAfterCC = false;
 static bool sIncrementalCC = false;
 static bool sDidPaintAfterPreviousICCSlice = false;
@@ -1312,7 +1313,14 @@ nsJSContext::GarbageCollectNow(JS::gcreason::Reason aReason,
   }
 
   JSGCInvocationKind gckind = aShrinking == ShrinkingGC ? GC_SHRINK : GC_NORMAL;
-  JS::PrepareForFullGC(sRuntime);
+
+  if (sNeedsFullGC || aReason != JS::gcreason::CC_WAITING) {
+    sNeedsFullGC = false;
+    JS::PrepareForFullGC(sRuntime);
+  } else {
+    CycleCollectedJSRuntime::Get()->PrepareWaitingZonesForGC();
+  }
+
   if (aIncremental == IncrementalGC) {
     JS::StartIncrementalGC(sRuntime, gckind, aReason, aSliceMillis);
   } else {
@@ -2009,6 +2017,8 @@ nsJSContext::RunNextCollectorTimer()
 void
 nsJSContext::PokeGC(JS::gcreason::Reason aReason, int aDelay)
 {
+  sNeedsFullGC = sNeedsFullGC || aReason != JS::gcreason::CC_WAITING;
+
   if (sGCTimer || sInterSliceGCTimer || sShuttingDown) {
     // There's already a timer for GC'ing, just return
     return;
@@ -2380,6 +2390,7 @@ mozilla::dom::StartupJSEnvironment()
   sLikelyShortLivingObjectsNeedingGC = 0;
   sPostGCEventsToConsole = false;
   sNeedsFullCC = false;
+  sNeedsFullGC = false;
   sNeedsGCAfterCC = false;
   gNameSpaceManager = nullptr;
   sRuntime = nullptr;

xpcom/base/CycleCollectedJSRuntime.cpp

@@ -1557,6 +1557,7 @@ CycleCollectedJSRuntime::OnGC(JSGCStatus aStatus)
   switch (aStatus) {
     case JSGC_BEGIN:
       nsCycleCollector_prepareForGarbageCollection();
+      mZonesWaitingForGC.Clear();
       break;
     case JSGC_END: {
 #ifdef MOZ_CRASHREPORTER
@@ -1599,3 +1600,16 @@ CycleCollectedJSRuntime::OnLargeAllocationFailure()
   CustomLargeAllocationFailureCallback();
   AnnotateAndSetOutOfMemory(&mLargeAllocationFailureState, OOMState::Reported);
 }
+
+void
+CycleCollectedJSRuntime::PrepareWaitingZonesForGC()
+{
+  if (mZonesWaitingForGC.Count() == 0) {
+    JS::PrepareForFullGC(Runtime());
+  } else {
+    for (auto iter = mZonesWaitingForGC.Iter(); !iter.Done(); iter.Next()) {
+      JS::PrepareZoneForGC(iter.Get()->GetKey());
+    }
+    mZonesWaitingForGC.Clear();
+  }
+}

xpcom/base/CycleCollectedJSRuntime.h

@@ -19,6 +19,7 @@
 #include "nsDataHashtable.h"
 #include "nsHashKeys.h"
 #include "nsTArray.h"
+#include "nsTHashtable.h"
 
 class nsCycleCollectionNoteRootCallback;
 class nsIException;
@@ -334,6 +335,18 @@ public:
   // isn't one.
   static CycleCollectedJSRuntime* Get();
 
+  // Add aZone to the set of zones waiting for a GC.
+  void AddZoneWaitingForGC(JS::Zone* aZone)
+  {
+    mZonesWaitingForGC.PutEntry(aZone);
+  }
+
+  // Prepare any zones for GC that have been passed to AddZoneWaitingForGC()
+  // since the last GC or since the last call to PrepareWaitingZonesForGC(),
+  // whichever was most recent. If there were no such zones, prepare for a
+  // full GC.
+  void PrepareWaitingZonesForGC();
+
   // Storage for watching rejected promises waiting for some client to
   // consume their rejection.
   // We store values as `nsISupports` to avoid adding compile-time dependencies
@@ -386,6 +399,8 @@ private:
   SegmentedVector<JS::PersistentRooted<JSObject*>, kSegmentSize,
                   InfallibleAllocPolicy>
     mPreservedNurseryObjects;
+
+  nsTHashtable<nsPtrHashKey<JS::Zone>> mZonesWaitingForGC;
 };
 
 void TraceScriptHolder(nsISupports* aHolder, JSTracer* aTracer);

xpcom/base/nsCycleCollector.cpp

@@ -3265,9 +3265,15 @@ nsCycleCollector::CollectWhite()
     if (pinfo->mColor == white && pinfo->mParticipant) {
       if (pinfo->IsGrayJS()) {
         ++numWhiteGCed;
+        JS::Zone* zone;
         if (MOZ_UNLIKELY(pinfo->mParticipant == zoneParticipant)) {
           ++numWhiteJSZones;
+          zone = static_cast<JS::Zone*>(pinfo->mPointer);
+        } else {
+          JS::GCCellPtr ptr(pinfo->mPointer, js::GCThingTraceKind(pinfo->mPointer));
+          zone = JS::GetTenuredGCThingZone(ptr);
         }
+        mJSRuntime->AddZoneWaitingForGC(zone);
       } else {
         whiteNodes.InfallibleAppend(pinfo);
         pinfo->mParticipant->Root(pinfo->mPointer);