Messages in this thread |  | | Date | Tue, 8 Jan 2013 07:31:30 -0700 | From | Jonathan Corbet <> | Subject | Re: [PATCH v3 2/4] videobuf2-dma-streaming: new videobuf2 memory allocator |
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On Tue, 08 Jan 2013 07:50:41 +0100 Marek Szyprowski <m.szyprowski@samsung.com> 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.
jon
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