Changeset 83940 in webkit

Timestamp:

Apr 14, 2011 8:48:42 PM (13 years ago)

Author:

eric@webkit.org

Message:

2011-04-14 Eric Seidel <​eric@webkit.org>

Reviewed by Simon Fraser.

PumpSession should not call currentTime() in the constructor
​https://bugs.webkit.org/show_bug.cgi?id=55211

currentTime() is expensive. So we avoid calling it in the constructor
and instead set startTime on the first check for a yield
(which in the synchronous case never happens, and in the yielding
case will happen immediately after the first token due to
processedTokens being set to INT_MAX).

This ended up being a large win on (my local copy of)
peacekeeper's domDynamicCreationCreateElement:

Before:
avg 366.3333333333333
median 366
stdev 2.712112747574399
min 362
max 377

After:
avg 345.96666666666664
median 346
stdev 1.6829207415152454
min 343
max 349

• html/parser/HTMLDocumentParser.cpp:
• html/parser/HTMLParserScheduler.h: (WebCore::PumpSession::PumpSession): (WebCore::HTMLParserScheduler::checkForYieldBeforeToken):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• html/parser/HTMLDocumentParser.cpp (modified) (1 diff)
• html/parser/HTMLParserScheduler.h (modified) (3 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2011-04-14  Eric Seidel  <eric@webkit.org>
+
+        Reviewed by Simon Fraser.
+
+        PumpSession should not call currentTime() in the constructor
+        https://bugs.webkit.org/show_bug.cgi?id=55211
+
+        currentTime() is expensive.  So we avoid calling it in the constructor
+        and instead set startTime on the first check for a yield
+        (which in the synchronous case never happens, and in the yielding
+        case will happen immediately after the first token due to
+        processedTokens being set to INT_MAX).
+
+        This ended up being a large win on (my local copy of)
+        peacekeeper's domDynamicCreationCreateElement:
+
+        Before:
+        avg 366.3333333333333
+        median 366
+        stdev 2.712112747574399
+        min 362
+        max 377
+
+        After:
+        avg 345.96666666666664
+        median 346
+        stdev 1.6829207415152454
+        min 343
+        max 349
+
+        * html/parser/HTMLDocumentParser.cpp:
+        * html/parser/HTMLParserScheduler.h:
+        (WebCore::PumpSession::PumpSession):
+        (WebCore::HTMLParserScheduler::checkForYieldBeforeToken):
+
 2011-04-14  Ami Fischman  <fischman@google.com>
 

trunk/Source/WebCore/html/parser/HTMLDocumentParser.cpp

@@ -41 +41 @@
 #include "NestingLevelIncrementer.h"
 #include "Settings.h"
-#include <wtf/CurrentTime.h>
 
 namespace WebCore {

trunk/Source/WebCore/html/parser/HTMLParserScheduler.h

@@ -27 +27 @@
 #define HTMLParserScheduler_h
 
+#include <limits.h>
+
 #include "NestingLevelIncrementer.h"
 #include "Timer.h"
@@ -40 +42 @@
     PumpSession(unsigned& nestingLevel)
         : NestingLevelIncrementer(nestingLevel)
-        , processedTokens(0)
-        , startTime(currentTime())
+        // Setting processedTokens to INT_MAX causes us to check for yields
+        // after any token during any parse where yielding is allowed.
+        // At that time we'll initialize startTime.
+        , processedTokens(INT_MAX)
+        , startTime(0)
         , needsYield(false)
     {
@@ -64 +69 @@
     {
         if (session.processedTokens > m_parserChunkSize) {
+            // currentTime() can be expensive.  By delaying, we avoided calling
+            // currentTime() when constructing non-yielding PumpSessions.
+            if (!session.startTime)
+                session.startTime = currentTime();
+
             session.processedTokens = 0;
             double elapsedTime = currentTime() - session.startTime;