[Webkit-unassigned] [Bug 33520] Mapping from local to container coord space is O(N^2)

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=33520





--- Comment #2 from James Robinson <jamesr at chromium.org>  2010-01-11 23:43:25 PST ---
Created an attachment (id=46340)
 --> (https://bugs.webkit.org/attachment.cgi?id=46340)
Profile of the position:relative test page (postscript)

Here are the top few hot functions (as reported by pprof, tested using the
'test_shell' thin WebView wrapper from Chromium on a 32bit linux system):

(pprof) top20
Total: 2571 samples
     877  34.1%  34.1%      877  34.1%
WebCore::RenderLayer::convertToLayerCoords
     329  12.8%  46.9%     1223  47.6% WebCore::RenderBox::mapLocalToContainer
     275  10.7%  57.6%      369  14.4%
WebCore::RenderBox::computeRectForRepaint
     134   5.2%  62.8%      161   6.3% WebCore::RenderObject::containingBlock
      92   3.6%  66.4%      618  24.0%
WebCore::RenderBoxModelObject::relativePositionOffsetX
      89   3.5%  69.9%      758  29.5% WebCore::RenderBox::offsetFromContainer
      81   3.2%  73.0%      303  11.8% WebCore::RenderBlock::availableWidth
      78   3.0%  76.0%       78   3.0%
WebCore::RenderObject::offsetFromContainer
      74   2.9%  78.9%       74   2.9%
WebCore::RenderBoxModelObject::borderLeft
      72   2.8%  81.7%       72   2.8% WebCore::RenderObject::isRooted
      69   2.7%  84.4%      162   6.3% WebCore::RenderBox::clientWidth
      38   1.5%  85.9%       38   1.5% WebCore::TransformState::move
      37   1.4%  87.3%       37   1.4%
WebCore::RenderBoxModelObject::relativePositionOffsetY
      36   1.4%  88.7%       40   1.6% WebCore::RenderBlock::isBlockFlow
      32   1.2%  90.0%       32   1.2%
WebCore::RenderBoxModelObject::paddingRight
      29   1.1%  91.1%       29   1.1%
WebCore::RenderBoxModelObject::paddingLeft
      28   1.1%  92.2%       33   1.3% WebCore::RenderObject::enclosingLayer
      26   1.0%  93.2%       26   1.0% WebCore::RenderObject::isHR
      25   1.0%  94.2%       27   1.1% WebCore::RenderObject::enclosingBox
      23   0.9%  95.1%      110   4.3%
WebCore::RenderLayer::updateLayerPositions
      10   0.4%  95.4%       10   0.4%
WebCore::RenderBox::verticalScrollbarWidth

Information about the profiler is here:
http://goog-perftools.sourceforge.net/doc/cpu_profiler.html.  The important
column are the first (number of samples recorded inside this function), second
(% of total time recorded within this function) and fourth (% of time spend in
this function and its callees).

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