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SubjectRe: [RFC] block layer support for DMA IOMMU bypass mode II
On Tue, 08 Jul 2003 15:23:14 -0700 (PDT)
"David S. Miller" <davem@redhat.com> wrote:

> From: Grant Grundler <grundler@parisc-linux.org>
> Date: Tue, 8 Jul 2003 16:25:45 -0600
>
> On Tue, Jul 08, 2003 at 03:04:33PM -0700, David S. Miller wrote:
> > Do you know a common PCI block device that would benefit from this
> > (performs significantly better with short sg lists)? It would be
> > interesting to test.
> >
> > %10 to %15 on sym53c8xx devices found on sparc64 boxes.
>
> Which workload?
>
> dbench type stuff, but that's a hard thing to test these days with
> the block I/O schedulers changing so much. Try to keep that part
> constant in the with/vs/without VIO_VMERGE!=0 testing :)

With MPT-Fusion and reaim "new dbase" load it seems to be slightly faster
with forced IOMMU merging on Opteron, but the differences are quite small (~4%) and could
be measurement errors.

-Andi
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