From eb8fe4ffcfb971c51c08c417b32e4909269396f7 Mon Sep 17 00:00:00 2001
From: Jon Coppeard <jcoppeard@mozilla.com>
Date: Wed, 2 Jul 2014 08:05:58 +0100
Subject: [PATCH] Bug 1032750 - Don't update GC triggers on uncollected zones
 r=terrence

---
 js/src/gc/Zone.cpp |  7 +++++++
 js/src/gc/Zone.h   |  2 ++
 js/src/jsgc.cpp    | 13 ++++++++-----
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/js/src/gc/Zone.cpp b/js/src/gc/Zone.cpp
index 898cd63c6fd..997f9ad800e 100644
--- a/js/src/gc/Zone.cpp
+++ b/js/src/gc/Zone.cpp
@@ -107,6 +107,13 @@ Zone::onTooMuchMalloc()
     }
 }
 
+bool
+Zone::isCloseToAllocTrigger(bool highFrequencyGC) const
+{
+    double factor = highFrequencyGC ? 0.85 : 0.9;
+    return usage.gcBytes() >= factor * threshold.gcTriggerBytes();
+}
+
 void
 Zone::beginSweepTypes(FreeOp *fop, bool releaseTypes)
 {
diff --git a/js/src/gc/Zone.h b/js/src/gc/Zone.h
index 6f4173e98f0..3a867e43f71 100644
--- a/js/src/gc/Zone.h
+++ b/js/src/gc/Zone.h
@@ -153,6 +153,8 @@ struct Zone : public JS::shadow::Zone,
     bool isTooMuchMalloc() const { return gcMallocBytes <= 0; }
     void onTooMuchMalloc();
 
+    bool isCloseToAllocTrigger(bool highFrequencyGC) const;
+
     void *onOutOfMemory(void *p, size_t nbytes) {
         return runtimeFromMainThread()->onOutOfMemory(p, nbytes);
     }
diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
index 6101eae98f8..e4e5f6796d9 100644
--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -1113,7 +1113,7 @@ GCRuntime::GCRuntime(JSRuntime *rt) :
     verifyPostData(nullptr),
     chunkAllocationSinceLastGC(false),
     nextFullGCTime(0),
-    lastGCTime(0),
+    lastGCTime(PRMJ_Now()),
     mode(JSGC_MODE_INCREMENTAL),
     decommitThreshold(32 * 1024 * 1024),
     cleanUpEverything(false),
@@ -3308,9 +3308,8 @@ GCRuntime::maybeGC(Zone *zone)
     if (gcIfNeeded())
         return true;
 
-    double factor = schedulingState.inHighFrequencyGCMode() ? 0.85 : 0.9;
     if (zone->usage.gcBytes() > 1024 * 1024 &&
-        zone->usage.gcBytes() >= factor * zone->threshold.gcTriggerBytes() &&
+        zone->isCloseToAllocTrigger(schedulingState.inHighFrequencyGCMode()) &&
         incrementalState == NO_INCREMENTAL &&
         !isBackgroundSweeping())
     {
@@ -5628,10 +5627,10 @@ GCRuntime::finishCollection()
     schedulingState.updateHighFrequencyMode(lastGCTime, currentTime, tunables);
 
     for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) {
-        zone->threshold.updateAfterGC(zone->usage.gcBytes(), invocationKind, tunables,
-                                      schedulingState);
         if (zone->isCollecting()) {
             MOZ_ASSERT(zone->isGCFinished() || zone->isGCCompacting());
+            zone->threshold.updateAfterGC(zone->usage.gcBytes(), invocationKind, tunables,
+                                          schedulingState);
             zone->setGCState(Zone::NoGC);
             zone->active = false;
         }
@@ -6219,6 +6218,10 @@ GCRuntime::scanZonesBeforeGC()
         if (incrementalState != NO_INCREMENTAL && zone->needsIncrementalBarrier())
             zone->scheduleGC();
 
+        /* This is a heuristic to reduce the total number of collections. */
+        if (zone->isCloseToAllocTrigger(schedulingState.inHighFrequencyGCMode()))
+            zone->scheduleGC();
+
         zoneStats.zoneCount++;
         if (zone->isGCScheduled()) {
             zoneStats.collectedZoneCount++;