Changeset 215153 in webkit

Timestamp:

Apr 8, 2017, 4:55:30 PM (8 years ago)

Author:

Simon Fraser

Message:

Align the timers for throttled rAF to reduce power usage
​https://bugs.webkit.org/show_bug.cgi?id=170630
rdar://problem/31490620

Reviewed by Chris Dumez.

Align the timers for all throttled ScriptedAnimationControllers in the process with
a resolution of 30ms, which reduces process wake-ups and thus saves power.

• dom/ScriptedAnimationController.cpp:

(WebCore::ScriptedAnimationController::scheduleAnimation):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• dom/ScriptedAnimationController.cpp (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2017-04-08  Simon Fraser  <simon.fraser@apple.com>
+
+        Align the timers for throttled rAF to reduce power usage
+        https://bugs.webkit.org/show_bug.cgi?id=170630
+        rdar://problem/31490620
+
+        Reviewed by Chris Dumez.
+
+        Align the timers for all throttled ScriptedAnimationControllers in the process with
+        a resolution of 30ms, which reduces process wake-ups and thus saves power.
+
+        * dom/ScriptedAnimationController.cpp:
+        (WebCore::ScriptedAnimationController::scheduleAnimation):
+
 2017-04-08  Chris Dumez  <cdumez@apple.com>
 

trunk/Source/WebCore/dom/ScriptedAnimationController.cpp

@@ -304 +304 @@
 
     Seconds animationInterval = interval();
-    double scheduleDelay = std::max<double>(animationInterval.value() - (m_document->domWindow()->nowTimestamp() - m_lastAnimationFrameTimestamp), 0);
-    m_animationTimer.startOneShot(scheduleDelay);
+
+    // FIXME: not ideal to snapshot time both in now() and nowTimestamp(), the latter of which also has reduced resolution.
+    MonotonicTime now = MonotonicTime::now();
+
+    MonotonicTime fireTime = now + std::max(animationInterval - Seconds(m_document->domWindow()->nowTimestamp() - m_lastAnimationFrameTimestamp), 0_s);
+    Seconds alignmentInterval = 30_ms;
+    // Snap to the nearest alignmentInterval.
+    Seconds alignment = (fireTime + alignmentInterval / 2) % alignmentInterval;
+    MonotonicTime alignedFireTime = fireTime - alignment;
+
+    m_animationTimer.startOneShot(alignedFireTime - now);
+
     dispatchLoggingEventIfRequired("raf-schedule-animation-timer");
 #else