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Date: Mon, 7 Jan 2013 18:15:00 -0200
From: Mauro Carvalho Chehab <mchehab@redhat.com>
To: Jonathan Corbet <corbet@lwn.net>
Cc: Alessandro Rubini <rubini@gnudd.com>, federico.vaga@gmail.com,
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Subject: Re: [PATCH v3 2/4] videobuf2-dma-streaming: new videobuf2 memory
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Em Mon, 7 Jan 2013 12:40:50 -0700
Jonathan Corbet <corbet@lwn.net> escreveu:

> On Mon, 7 Jan 2013 00:09:47 +0100
> Alessandro Rubini <rubini@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?

Regards,
Mauro