[openib-general] [PATCH for-2.6.21] IPoIB/cm: improve small message bandwidth

[Michael S. Tsirkin]

> Quoting Roland Dreier <rdreier at cisco.com>:
> Subject: Re: [PATCH for-2.6.21] IPoIB/cm: improve small message bandwidth
> 
> Thanks, queued for 2.6.21.  With this patch I see small-packet latency
> down almost all the way back to what datagram mode gives -- on a pair
> of fast woodcrest systems I see latencies for netpipe tcp 1 byte
> messages like
> 
>   datagram     13.xx
>   original CM  17.xx
>   patched CM   14.xx
> 
> so there is still a measurable difference but it is much less now.

Hmm. An old system I tried here has a much higher latency, but
does not seem to exhibit latency difference between datagram and CM.

1. Is there something special you do when you run the benchmark (msi, taskset, ...)?
2. On a wild guess that the issue here is higher interrupt rate with CM,
   is there a chance you could test the following patch posted by me earlier?
   http://www.mail-archive.com/openib-general@openib.org/msg29290.html

Thanks,

-- 
MST