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xen-devel
Re: [Xen-devel] SWIOMMU redundant copies?
Yes, the swiotlb check could be relaxed. Do we really do many mergeable
page-straddling I/Os in practice though? I would expect most block I/O to be
scattered by the page cache.
-- Keir
On 14/3/08 15:50, "Stephen C. Tweedie" <sct@xxxxxxxxxx> wrote:
> So we'll create bios which span multiple pages, assuming that that's
> more efficient; but then we'll force them to be copied because they span
> multiple pages!
>
> Have I missed something, or is this an oversight in the swiotlb.c patch
> above?
>
> The reason I discovered this is that including the patch seems to be
> causing SWIOTLB overflows on some hardware. Adding an extra test to
> swiotlb_map_sg() to catch sg segments which are truly machine-contig and
> don't need mapping, and avoid copying those, cures those symptoms for
> me, but I suspect there may be other issues lurking in this area.
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