[openib-general] Re: Re: [PATCH] IPoIB splitting CQ, increase both send/recv poll NUM_WC & interval

[Shirley Ma]

"Michael S. Tsirkin" <mst at mellanox.co.il> wrote on 04/29/2006 03:23:51 PM:

> Quoting r. Shirley Ma <xma at us.ibm.com>:
> > Subject: Re: [openib-general] Re: Re: [PATCH] IPoIB splitting CQ,?
> increase both send/recv poll NUM_WC & interval
> > 
> > 
> > Michael,
> > 
> > smp kernel on UP result is very bad. It dropped 40% throughput.
> > up kernel on UP thoughput dropped with cpu utilization dropped 
> from 75% idle to 52% idle.
> 
> Hmm. So far it seems the approach only works well on 2 CPUs.

Yes, since one cpu can only handler one handler. 
The easy solution would use ifdef SMP. 

Some mistake here, the cpu utilization dropped 
from 85%(15% idle) to 52%(48% idle). 

> > I didn't see latency difference. I used TCP_RR test.
> 
> This is somewhat surprising, isn't it? One would explain the extra
> context switch to have some effect on latency, would one not?
> 
> -- 
> MST

Thread context switch is pretty light.

Thanks
Shirley Ma
IBM Linux Technology Center
15300 SW Koll Parkway
Beaverton, OR 97006-6063
Phone(Fax): (503) 578-7638
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