[openib-general] Re: [PATCH] 2/2 : ip over ib tx/rx split

[Michael S. Tsirkin]

Quoting r. Michael S. Tsirkin <mst at mellanox.co.il>:
> Subject: Re: [PATCH] 2/2 : ip over ib tx/rx split
> 
> 
> Quoting r. Roland Dreier <roland at topspin.com>:
> > Subject: Re: [openib-general] [PATCH] 2/2 : ip over ib tx/rx split
> > 
> >     Roland> The only difference is that we unlock the receive CQ and
> >     Roland> lock the send CQ in the middle.
> > 
> >     Michael> Are you sure?  I *do* have msi-x on these machines.
> > 
> > Of course I'm not sure, but as far as I know, with the current drivers
> > even with MSI-X there's still only one completion interrupt handler,
> > which can only run on one CPU at a time.
> > 
> 
> Sounds convincing. So the improvement is probably due to
> better send/receive parallelism we are getting in mthca.

Roland, I just made some measurements.

With the split lock in mthca, but a shared cq in ip over ib, bandwidth goes
up from around 300 to around 313 Mb/sec.
So for the mthca patch, I see almost 4% improvement - seems
like a good thing, so please consider applying it.

My ip over ib patch seems to need a bit more work before its actually
useful.

-- 
MST - Michael S. Tsirkin