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SubjectRe: alpha iommu fixes
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.

[BTW, the 2.4.4 netstack does not seem to make any attempt to handle the
pagecache > 4GB case on IA32 for sendfile, as the pci_* functions are dummies
here. It probably needs bounce buffers there for this case]



-Andi
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