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SubjectRe: [PATCH v3 2/4] videobuf2-dma-streaming: new videobuf2 memory allocator
On Tue, 08 Jan 2013 07:50:41 +0100
Marek Szyprowski <> wrote:

> > 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.

Exactly. Uncached memory *hurts*, especially if you're having to touch it
all with the CPU.


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