Bug 568730 - Allow customizing the sleep duration in XPCJSRuntime::WatchdogMain. r=igor/jst/gal

js/src/jsapi.cpp

@@ -805,6 +805,9 @@ JS_BeginRequest(JSContext *cx)
         cx->outstandingRequests++;
         cx->thread->requestContext = cx;
         rt->requestCount++;
+
+        if (rt->requestCount == 1)
+            rt->activityCallback(rt->activityCallbackArg, true);
     }
 #endif
 }
@@ -853,8 +856,10 @@ StopRequest(JSContext *cx)
         /* Give the GC a chance to run if this was the last request running. */
         JS_ASSERT(rt->requestCount > 0);
         rt->requestCount--;
-        if (rt->requestCount == 0)
+        if (rt->requestCount == 0) {
             JS_NOTIFY_REQUEST_DONE(rt);
+            rt->activityCallback(rt->activityCallbackArg, false);
+        }
     }
 }
 #endif

js/src/jscntxt.h

@@ -1218,6 +1218,9 @@ struct JSCompartment {
     void sweep(JSContext *cx);
 };
 
+typedef void
+(* JSActivityCallback)(void *arg, JSBool active);
+
 struct JSRuntime {
     /* Default compartment. */
     JSCompartment       *defaultCompartment;
@@ -1234,6 +1237,20 @@ struct JSRuntime {
     /* Compartment create/destroy callback. */
     JSCompartmentCallback compartmentCallback;
 
+    /*
+     * Sets a callback that is run whenever the runtime goes idle - the
+     * last active request ceases - and begins activity - when it was
+     * idle and a request begins. Note: The callback is called under the
+     * GC lock.
+     */
+    void setActivityCallback(JSActivityCallback cb, void *arg) {
+        activityCallback = cb;
+        activityCallbackArg = arg;
+    }
+
+    JSActivityCallback    activityCallback;
+    void                 *activityCallbackArg;
+
     /*
      * Shape regenerated whenever a prototype implicated by an "add property"
      * property cache fill and induced trace guard has a readonly property or a

js/src/xpconnect/src/xpcjsruntime.cpp

@@ -803,14 +803,22 @@ XPCJSRuntime::WatchdogMain(void *arg)
     // Lock lasts until we return
     AutoLockJSGC lock(self->mJSRuntime);
 
+    PRIntervalTime sleepInterval;
     while (self->mWatchdogThread)
     {
+        // Sleep only 1 second if recently (or currently) active; otherwise, hibernate
+        if (self->mLastActiveTime == -1 || PR_Now() - self->mLastActiveTime <= 2*PR_USEC_PER_SEC)
+            sleepInterval = PR_TicksPerSecond();
+        else
+        {
+            sleepInterval = PR_INTERVAL_NO_TIMEOUT;
+            self->mWatchdogHibernating = PR_TRUE;
+        }
 #ifdef DEBUG
         PRStatus status =
 #endif
-            PR_WaitCondVar(self->mWatchdogWakeup, PR_TicksPerSecond());
+            PR_WaitCondVar(self->mWatchdogWakeup, sleepInterval);
         JS_ASSERT(status == PR_SUCCESS);
-
         JSContext* cx = nsnull;
         while((cx = js_NextActiveContext(self->mJSRuntime, cx)))
         {
@@ -822,6 +830,23 @@ XPCJSRuntime::WatchdogMain(void *arg)
     PR_NotifyCondVar(self->mWatchdogWakeup);
 }
 
+//static
+void
+XPCJSRuntime::ActivityCallback(void *arg, PRBool active)
+{
+    XPCJSRuntime* self = static_cast<XPCJSRuntime*>(arg);
+    if (active) {
+        self->mLastActiveTime = -1;
+        if (self->mWatchdogHibernating)
+        {
+            self->mWatchdogHibernating = PR_FALSE;
+            PR_NotifyCondVar(self->mWatchdogWakeup);
+        }
+    } else {
+        self->mLastActiveTime = PR_Now();
+    }
+}
+
 
 /***************************************************************************/
 
@@ -1108,7 +1133,9 @@ XPCJSRuntime::XPCJSRuntime(nsXPConnect* aXPConnect)
    mWrappedJSRoots(nsnull),
    mObjectHolderRoots(nsnull),
    mWatchdogWakeup(nsnull),
-   mWatchdogThread(nsnull)
+   mWatchdogThread(nsnull),
+   mWatchdogHibernating(PR_FALSE),
+   mLastActiveTime(-1)
 {
 #ifdef XPC_CHECK_WRAPPERS_AT_SHUTDOWN
     DEBUG_WrappedNativeHashtable =
@@ -1138,6 +1165,8 @@ XPCJSRuntime::XPCJSRuntime(nsXPConnect* aXPConnect)
         JS_SetExtraGCRoots(mJSRuntime, TraceJS, this);
         mWatchdogWakeup = JS_NEW_CONDVAR(mJSRuntime->gcLock);
 
+        mJSRuntime->setActivityCallback(ActivityCallback, this);
+
         mJSRuntime->setCustomGCChunkAllocator(&gXPCJSChunkAllocator);
 
         NS_RegisterMemoryReporter(new NS_MEMORY_REPORTER_NAME(XPConnectJSRuntimeGCChunks));

js/src/xpconnect/src/xpcprivate.h

@@ -720,6 +720,8 @@ public:
     void AddGCCallback(JSGCCallback cb);
     void RemoveGCCallback(JSGCCallback cb);
 
+    static void ActivityCallback(void *arg, PRBool active);
+
 private:
     XPCJSRuntime(); // no implementation
     XPCJSRuntime(nsXPConnect* aXPConnect);
@@ -758,6 +760,8 @@ private:
     PRCondVar *mWatchdogWakeup;
     PRThread *mWatchdogThread;
     nsTArray<JSGCCallback> extraGCCallbacks;
+    PRBool mWatchdogHibernating;
+    PRTime mLastActiveTime; // -1 if active NOW
 };
 
 /***************************************************************************/