From 40b5bfe7e9b27465ec4bdb335a7a250a691f25b9 Mon Sep 17 00:00:00 2001
From: Andrew McCreight <continuation@gmail.com>
Date: Wed, 18 Dec 2013 11:42:16 -0800
Subject: [PATCH] Bug 937960, part 2 - Add ICC slice timer and scheduling.
 r=smaug

---
 dom/base/nsJSEnvironment.cpp | 64 ++++++++++++++++++++++++++++++++++--
 dom/base/nsJSEnvironment.h   |  1 +
 2 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index 6ca3f1bd5c5e..28a687e96cd6 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -121,6 +121,9 @@ static PRLogModuleInfo* gJSDiagnostics;
 
 #define NS_CC_SKIPPABLE_DELAY       400 // ms
 
+// Maximum amount of time that should elapse between incremental CC slices
+static const int64_t kICCIntersliceDelay = 32; // 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
@@ -144,6 +147,7 @@ static PRLogModuleInfo* gJSDiagnostics;
 static nsITimer *sGCTimer;
 static nsITimer *sShrinkGCBuffersTimer;
 static nsITimer *sCCTimer;
+static nsITimer *sICCTimer;
 static nsITimer *sFullGCTimer;
 static nsITimer *sInterSliceGCTimer;
 
@@ -223,6 +227,7 @@ KillTimers()
   nsJSContext::KillGCTimer();
   nsJSContext::KillShrinkGCBuffersTimer();
   nsJSContext::KillCCTimer();
+  nsJSContext::KillICCTimer();
   nsJSContext::KillFullGCTimer();
   nsJSContext::KillInterSliceGCTimer();
 }
@@ -2082,6 +2087,30 @@ nsJSContext::ScheduledCycleCollectNow()
   nsCycleCollector_scheduledCollect();
 }
 
+static void
+ICCTimerFired(nsITimer* aTimer, void* aClosure)
+{
+  if (sDidShutdown) {
+    return;
+  }
+
+  // Ignore ICC timer fires during IGC. Running ICC during an IGC will cause us
+  // to synchronously finish the GC, which is bad.
+
+  if (sCCLockedOut) {
+    PRTime now = PR_Now();
+    if (sCCLockedOutTime == 0) {
+      sCCLockedOutTime = now;
+      return;
+    }
+    if (now - sCCLockedOutTime < NS_MAX_CC_LOCKEDOUT_TIME) {
+      return;
+    }
+  }
+
+  nsJSContext::ScheduledCycleCollectNow();
+}
+
 //static
 void
 nsJSContext::BeginCycleCollectionCallback()
@@ -2092,6 +2121,20 @@ nsJSContext::BeginCycleCollectionCallback()
   gCCStats.mSuspected = nsCycleCollector_suspectedCount();
 
   KillCCTimer();
+
+  MOZ_ASSERT(!sICCTimer, "Tried to create a new ICC timer when one already existed.");
+
+  if (!sIncrementalCC) {
+    return;
+  }
+
+  CallCreateInstance("@mozilla.org/timer;1", &sICCTimer);
+  if (sICCTimer) {
+    sICCTimer->InitWithFuncCallback(ICCTimerFired,
+                                    nullptr,
+                                    kICCIntersliceDelay,
+                                    nsITimer::TYPE_REPEATING_SLACK);
+  }
 }
 
 //static
@@ -2100,6 +2143,8 @@ nsJSContext::EndCycleCollectionCallback(CycleCollectorResults &aResults)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
+  nsJSContext::KillICCTimer();
+
   sCCollectedWaitingForGC += aResults.mFreedRefCounted + aResults.mFreedGCed;
 
   // If we collected a substantial amount of cycles, poke the GC since more objects
@@ -2298,7 +2343,7 @@ CCTimerFired(nsITimer *aTimer, void *aClosure)
 
   // During early timer fires, we only run forgetSkippable. During the first
   // late timer fire, we decide if we are going to have a second and final
-  // late timer fire, where we may run the CC.
+  // late timer fire, where we may begin to run the CC.
   const uint32_t numEarlyTimerFires = ccDelay / NS_CC_SKIPPABLE_DELAY - 2;
   bool isLateTimerFire = sCCTimerFireCount > numEarlyTimerFires;
   uint32_t suspected = nsCycleCollector_suspectedCount();
@@ -2426,7 +2471,7 @@ nsJSContext::PokeShrinkGCBuffers()
 void
 nsJSContext::MaybePokeCC()
 {
-  if (sCCTimer || sShuttingDown || !sHasRunGC) {
+  if (sCCTimer || sICCTimer || sShuttingDown || !sHasRunGC) {
     return;
   }
 
@@ -2498,6 +2543,19 @@ nsJSContext::KillCCTimer()
   }
 }
 
+//static
+void
+nsJSContext::KillICCTimer()
+{
+  sCCLockedOutTime = 0;
+
+  if (sICCTimer) {
+    sICCTimer->Cancel();
+
+    NS_RELEASE(sICCTimer);
+  }
+}
+
 void
 nsJSContext::GC(JS::gcreason::Reason aReason)
 {
@@ -2659,7 +2717,7 @@ void
 mozilla::dom::StartupJSEnvironment()
 {
   // initialize all our statics, so that we can restart XPCOM
-  sGCTimer = sFullGCTimer = sCCTimer = nullptr;
+  sGCTimer = sFullGCTimer = sCCTimer = sICCTimer = nullptr;
   sCCLockedOut = false;
   sCCLockedOutTime = 0;
   sLastCCEndTime = 0;
diff --git a/dom/base/nsJSEnvironment.h b/dom/base/nsJSEnvironment.h
index 002351c658ef..cbfbd1559f30 100644
--- a/dom/base/nsJSEnvironment.h
+++ b/dom/base/nsJSEnvironment.h
@@ -117,6 +117,7 @@ public:
 
   static void MaybePokeCC();
   static void KillCCTimer();
+  static void KillICCTimer();
   static void KillFullGCTimer();
   static void KillInterSliceGCTimer();