[cairo] scaling performance test of cairo library

[Siarhei Siamashka]

On Tuesday 08 February 2011 06:52:02 cooolheater wrote:
> Hi,
> I'm developer of mobile browser using webkit with cairo library.
> Recently, I did performance comparing test between cairo 1.10.02 and skia
> library.

Thanks for your benchmarking data. What kind of hardware have you used for
running this benchmark? And because you are using cairo image backend, the
version of pixman library is also important because it is actually doing all
the scaling work.

> The performance of compstion and rotating seems similar,

Performance of rotation in pixman should be horrible right now, don't know if
I should be happy to know that skia seems to be just as bad :)

What kind of rotation are you are interested in? The following patches should
help with some types of rotation, and can be extended if needed:
http://lists.freedesktop.org/archives/pixman/2011-February/000970.html

> but scaling performance of cairo library seems quite low.

On non-SIMD capable processors, cairo/pixman should have bilinear scaling
performing roughly as fast as the other good implementations, so I assume that
some kind of SIMD is supported on your target system.

A problem with bilinear scaling performance in pixman is that it does not have
SIMD optimizations yet. That's something that I'm currently looking into, at
least for ARM NEON.

Also your benchmarks show that the overhead before reaching actual scaling code
is much lower with skia as can be seen for very small sizes of images. It's
still questionable how much such overhead affects real use cases, but I'm
expressing concern here from time to time whenever I see the patches which seem
to be increasing this overhead in pixman more than necessary.

The only surprising thing in your data is that skia seems to have really poor
performance for nearest scaling, but probably they just primarily focused on
making bilinear scaling fast.

-- 
Best regards,
Siarhei Siamashka