Title: [197415] trunk/Source/WebCore
- Revision
- 197415
- Author
- [email protected]
- Date
- 2016-03-01 15:33:36 -0800 (Tue, 01 Mar 2016)
Log Message
Timer alignment in separate web processes should not all sync up to the same point.
https://bugs.webkit.org/show_bug.cgi?id=154878
Reviewed by Chris Dumez.
For any given WebContent process it is desirable that timers are synchronized to a single
alignment point, but if all WebContent processes align to the same point then there may
be a thundering herd of processes waking up.
* page/DOMTimer.cpp:
(WebCore::DOMTimer::alignedFireTime):
- align to a randomized point.
Modified Paths
Diff
Modified: trunk/Source/WebCore/ChangeLog (197414 => 197415)
--- trunk/Source/WebCore/ChangeLog 2016-03-01 22:29:39 UTC (rev 197414)
+++ trunk/Source/WebCore/ChangeLog 2016-03-01 23:33:36 UTC (rev 197415)
@@ -1,3 +1,18 @@
+2016-03-01 Gavin Barraclough <[email protected]>
+
+ Timer alignment in separate web processes should not all sync up to the same point.
+ https://bugs.webkit.org/show_bug.cgi?id=154878
+
+ Reviewed by Chris Dumez.
+
+ For any given WebContent process it is desirable that timers are synchronized to a single
+ alignment point, but if all WebContent processes align to the same point then there may
+ be a thundering herd of processes waking up.
+
+ * page/DOMTimer.cpp:
+ (WebCore::DOMTimer::alignedFireTime):
+ - align to a randomized point.
+
2016-03-01 Alex Christensen <[email protected]>
Reduce size of internal windows build output
Modified: trunk/Source/WebCore/page/DOMTimer.cpp (197414 => 197415)
--- trunk/Source/WebCore/page/DOMTimer.cpp 2016-03-01 22:29:39 UTC (rev 197414)
+++ trunk/Source/WebCore/page/DOMTimer.cpp 2016-03-01 23:33:36 UTC (rev 197415)
@@ -40,6 +40,7 @@
#include <wtf/HashMap.h>
#include <wtf/MathExtras.h>
#include <wtf/NeverDestroyed.h>
+#include <wtf/RandomNumber.h>
#include <wtf/StdLibExtras.h>
#if PLATFORM(IOS)
@@ -422,8 +423,15 @@
double DOMTimer::alignedFireTime(double fireTime) const
{
- if (double alignmentInterval = scriptExecutionContext()->timerAlignmentInterval(m_nestingLevel >= maxTimerNestingLevel))
- return ceil(fireTime / alignmentInterval) * alignmentInterval;
+ if (double alignmentInterval = scriptExecutionContext()->timerAlignmentInterval(m_nestingLevel >= maxTimerNestingLevel)) {
+ // Don't mess with zero-delay timers.
+ if (!fireTime)
+ return fireTime;
+ static const double randomizedAlignment = randomNumber();
+ // Force alignment to randomizedAlignment fraction of the way between alignemntIntervals, e.g.
+ // if alignmentInterval is 10 and randomizedAlignment is 0.3 this will align to 3, 13, 23, ...
+ return (ceil(fireTime / alignmentInterval - randomizedAlignment) + randomizedAlignment) * alignmentInterval;
+ }
return fireTime;
}
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