[webkit-qt] QtWebKit very slow compared to WebKitGtk (on top of directfb)

[haithem rahmani]

Hi,


> I doubt decoding is the issue. Except for the GIF format, the decoding
> of images is done by the usual libraries (libjpeg, libpng).
>
> My guess is color conversion could be an issue depending on the target
> color format on your directfb. If the color format on 32 bits, the
> problem could also be on composition or the final color conversion to
> the target framebuffer.
> (If the problem is on color conversion, scrolling is likely to be slower
> than usual as well).
>
> I suggest you to profile your application (oprofile generally works
> great on Linux devices) and share the results here.
>
>
I've sent a reply but it was blocked since it was a bit huge.

so here are the profiling results done using the "perf" tool.

# Samples: 3756
#
# Overhead  Samples           Command
                       Shared Object  Symbol
# ........ ..........  ..............
 .........................................................................
 ......
#
    57.11%       2145         swapper  [kernel]                       [k]
default_idle
     2.21%         83         browser
 /home/rahmanih/qt-4.7.2_21072011/lib/libQtWebKit.so.4.7.2
 [.] WebCore::DeprecatedPtrListImplIterator::operator++()
     1.76%         66         browser
 /home/rahmanih/qt-4.7.2_21072011/lib/libQtWebKit.so.4.7.2
 [.] WebCore::RenderBlock::leftRelOffset(int, int, bool, int*) const
     1.60%         60         browser
 /home/rahmanih/qt-4.7.2_21072011/lib/libQtWebKit.so.4.7.2
 [.] WebCore::RenderBlock::rightRelOffset(int, int, bool, int*) const
     0.96%         36         browser
 /home/rahmanih/qt-4.7.2_21072011/lib/libQtWebKit.so.4.7.2
 [.] WebCore::DeprecatedPtrListImplIterator::current() const
     0.80%         30         browser
 /home/rahmanih/qt-4.7.2_21072011/lib/libQtWebKit.so.4.7.2
 [.] WebCore::RenderLayer::paintLayer(WebCore::RenderLayer*,
WebCore::GraphicsContext*, WebCore::IntRect const&, unsigned int,
WebCore::RenderObject*, WTF::HashMap<WebCore::OverlapTestRequestClient*,
WebCore::IntRect, WTF::PtrHash<WebCore::OverlapTestRequestClient*>,
WTF::HashTraits<WebCore::OverlapTestRequestClient*>,
WTF::HashTraits<WebCore::IntRect> >*, unsigned int)
     0.77%         29         browser  [kernel]
                                      [k] 0x000000c1152b6e
     0.59%         22         browser
 /home/rahmanih/qt-4.7.2_21072011/lib/libQtWebKit.so.4.7.2
 [.] WebCore::InlineBox::height() const
     0.53%         20         browser
 /home/rahmanih/qt-4.7.2_21072011/lib/libQtGui.so.4.7.2
[.] INTERPOLATE_PIXEL_255(unsigned int, unsigned int, unsigned int, unsigned
int)
     0.51%         19         browser
 /home/rahmanih/qt-4.7.2_21072011/lib/libQtWebKit.so.4.7.2
 [.]
WebCore::RenderBlock::findNextLineBreak(WebCore::BidiResolver<WebCore::InlineIterator,
WebCore::BidiRun>&, bool, bool&, bool&, WebCore::EClear*)
     0.48%         18         browser  /lib/ld-2.10.1.so
                                     [.] do_lookup_x
     0.43%         16         browser  /lib/libc-2.10.1.so
                                     [.] _int_malloc
     0.43%         16         browser  /home/rahmanih/qt-4.7.2

I really can't understand why the 51% of the time is spent in the kernel as
"idle" ?

any idea on that ?

regards.
Haithem.


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