[cairo] Pixman - refactoring of fbFetchTransformed - performance issue

[Frédéric Plourde]

Hi !  I've run the perf suite on paint, paint-with-alpha and fill with 
"min" and "mag" sources.... And my results are closer to what Bertram got.
you can see them at : http://pastebin.mozilla.org/339355

in the best case,    we have 20% speedup
in the worst case,  we have 3X slowdown

I ran the tests on a intel Duo Core 2 CPU, 1.6 GHz
and compiled both versions using Visual C++ on WinXP in release mode (-O2)


-Fred -

> As an aside, it's odd that the difference between *_source and *_over
> is so large in your tests, and that *_source turns out to be slower.
> I wonder why.
>
> My numbers are different, for example:
>
> (before)
> [  9]    image-rgba  paint_image_rgba_mag_source-256   12614763    6.919    7.006  0.81%   8
> [ 10]    image-rgba   paint_image_rgba_min_over-256   14194059    7.785    7.788  0.09%   4
>
> (after)
> [  9]    image-rgba  paint_image_rgba_mag_source-256   16889333    9.264    9.267  0.02%   5
> [ 10]    image-rgba   paint_image_rgba_min_over-256   18351320   10.066   10.086  0.51%   5
>
> with hardly any difference between _source and _over.
>
>   
>> Could a third person run the perf before and after the refactoring to 
>> check the numbers?
>>     
>
> Yes, that would help - the more numbers the better.
>
> The relevant commits are in the pixman repository,
>    e95638c629334151e27633cc1c476ea582d766ec
>    (before the refactoring)
> and
>    8d79c48126398aa7b31e9bb9e25af9d231075604
>    (after)
>
> Of particular interest are the *_image_rgba_min_* and
> *_image_rgba_mag_* tests in the performance testsuite (now in
> cairo's git repository).
>
> Bertram
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