Re: [Xen-devel] Writing to a ramdisk in a PV domain is SLLLOOOWWW?!?

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 05/06/2010 03:04 PM, Santos, Jose Renato G wrote:
> This is complete wild guess, but could it be that you are doing multi-page 
> I/O with non contiguous machine pages?
> I believe the DMA API for pv guests uses swioltlb which does extra copies to 
> a bounce buffer if you request a dma address to a multi-page region (as the 
> pages may be non contiguous).
>   

Ramdisk access shouldn't be going anywhere near DMA API or swiotlb.

    J

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