[Pixman] [PATCH 0/4] ARM: REPEAT_NORMAL support for standard fast paths
sandmann at cs.au.dk
Tue Jul 12 07:05:22 PDT 2011
Taekyun Kim <podain77 at gmail.com> writes:
> On 07/11/2011 09:18 PM, Soeren Sandmann wrote:
>> This performance regression was introduced when the "simple repeat" code
>> was removed. But I'm not sure hacking it into the ARM backend is the
>> right plan. See this mail for a different approach:
>> I have a branch with a start on doing it that way here:
>> which may or may not be useful as a starting point. (I'd be interested
>> in seeing what the benchmark results of that branch are).
> It seems to be the right place where we can put simple repeat codes.
> It can handle simple repeat for both sse2 and ARM at common place.
> I'm a bit worried that tiling does not give us good memory access patterns
> causing cache overhead. 1 x n source images would be as slow as 90 degree
> rotation. Memory buffer will be accessed in vertical order.
Yeah, that is a problem, and that was in fact one of the reasons the
original 'simple repeat' code was deleted. It's memory access pattern
for 1xn images was really bad. It may be that adding this support to
the ARM backend, as you did, is the better way.
> May I take yours as a starting point and integrate with mine?
> Below is benchmark results. (Core2 Duo E5200)
> I couldn't see any noticeable performance changes.
No, it looks like a slowdown ...
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