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SubjectRe: alpha iommu fixes
On Mon, May 21 2001, Andi Kleen wrote:
> On Mon, May 21, 2001 at 03:00:24AM -0700, David S. Miller wrote:
> > > That's currently the case, but at least on IA32 the block layer
> > > must be fixed soon because it's a serious performance problem in
> > > some cases (and fixing it is not very hard).
> >
> > If such a far reaching change goes into 2.4.x, I would probably
> > begin looking at enhancing the PCI dma interfaces as needed ;-)
>
> Hmm, I don't think it'll be a far reaching change. As far as I can see
> all it needs is a new entry point for block device drivers that uses
> bh->b_page. When that entry point exists skip the create_bounce call
> in __make_request. After that it is purely problem for selected drivers.

I've already done it, however not as a 2.4 solution. The partial and WIP
patches is here:

*.kernel.org/pub/linux/kernel/people/axboe/v2.5/bio-7

Block driver can indicate the need for bounce buffers above a certain
page.

Of course I can hack up something for 2.4 as well, but is this really a
pressing need?

--
Jens Axboe

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