[openib-general] Re: MMIO reads for IPoIB w/MSI-X

[Grant Grundler]

On Sun, Jan 23, 2005 at 12:00:17AM +0200, Michael S. Tsirkin wrote:
> Quoting r. Grant Grundler <iod00d at hp.com>:
> > Subject: MMIO reads for IPoIB w/MSI-X
> > 
> > Hi all,
> > In trying to understand why netperf TCP_STREAM sucks on the ia64 platform
> > I'm slowly collecting more data. I didn't really have any time this
> > week to poke at this issue.
> > 
> > The follow data confirms in MSI-X mode mthca is essentially doing
> > no MMIO reads.
> 
> An additional advantage of MSI-X is that interrupts are not shared.
> But how is this related to ia64?

How is _what_ related to ia64?

MMIO reads hurt perf. MSI-X shouldn't need any MMIO reads and
I confirmed that is fact the case as a first step to understanding
why ia64-linux perf is "suboptimal".

grant