On 1/7/2013 9:15 PM, Mauro Carvalho Chehab wrote:
Em Mon, 7 Jan 2013 12:40:50 -0700
Jonathan Corbet <cor...@lwn.net> escreveu:
> On Mon, 7 Jan 2013 00:09:47 +0100
> Alessandro Rubini <rub...@gnudd.com> wrote:
>
> > I don't expect you'll see serious performance differences on the PC. I
> > think ARM users will have better benefits, due to the different cache
> > architecture. You told me Jon measured meaningful figures on a Marvel
> > CPU.
>
> It made the difference between 10 frames per second with the CPU running
> flat out and 30fps mostly idle. I think that probably counts as
> meaningful, yeah...:)
Couldn't this performance difference be due to the usage of GFP_DMA inside
the VB2 code, like Federico's new patch series is proposing?
If not, why are there a so large performance penalty?
Nope, this was caused rather by a very poor CPU access to non-cached (aka
'coherent') memory and the way the video data has been accessed/read
with CPU.
Best regards
--
Marek Szyprowski
Samsung Poland R&D Center
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