Subject: Re: [PATCH 3/4] myri10ge - Driver core

From: Anton Blanchard <[email-masked]>
Date: Thu, 25 May 2006 07:21:17 +1000

Hi,

> We didn't get any ppc64 with PCI-E to run Linux so far. What performance
> drop should we expect with our current code ?

We have seen > 20% improvement on ppc64 running some networking
workloads when forcing 128 byte alignment (instead of 16 byte
alignment). DMA writes have to get cacheline aligned (in power of 2
steps) on some IO chips.

> I am not sure what you mean.
> The only ppc64 with PCI-E that we have seen so far (a G5) couldn't do
> write combining according to Apple.

Im thinking more generally, MTRRs are x86 specific and it would be good
to have a more generic way to enable write combining.

Anton