[Pixman] [ssse3]Optimization for fetch_scanline_x8r8g8b8

Siarhei Siamashka siarhei.siamashka at gmail.com
Tue Sep 7 14:25:55 PDT 2010

On Friday 03 September 2010 01:39:54 Soeren Sandmann wrote:
> Siarhei Siamashka <siarhei.siamashka at gmail.com> writes:
> > Apparently software prefetch also disables or interferes with the hardware
> > prefetcher on Intel Atom, hurting performance a lot. More advanced
> > processors can cope with it.
> > 
> > But increased prefetch distance is less effective (or can even decrease
> > performance) when dealing with small images, so it is not always good.
> > 
> > Are there any SSE2 capable x86 processors without hardware prefetch
> > capability? Maybe it's really a good idea to remove software prefetch
> > from SSE2 fast path code?
> Yeah, it seems so. All data so far suggests that software prefetching
> is somewhere between 'slight slowdown' and 'no real effect'. The SSE2
> fast paths have very predictable memory access patterns, so a hardware
> prefetcher should be able to do a good job.
> (It might be worth investigating whether software prefetch would be
> beneficial in the tiled rotation fast paths, since the access patterns
> there could be much harder to predict for the hardware).

So I guess it makes sense for Liu, Xinyun to resubmit a clean patch with 
software prefetch removal for sse2 code instead of commenting it out?

As suggested in:

Best regards,
Siarhei Siamashka
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