netdev - Re: setsockopt()

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Date:	Thu, 10 Jul 2008 20:50:45 -0400
From:	Bill Fink <billfink@...dspring.com>
To:	Rick Jones <rick.jones2@...com>
Cc:	Evgeniy Polyakov <johnpol@....mipt.ru>,
	Roland Dreier <rdreier@...co.com>,
	David Miller <davem@...emloft.net>, aglo@...i.umich.edu,
	shemminger@...tta.com, netdev@...r.kernel.org, rees@...ch.edu,
	bfields@...ldses.org
Subject: Re: setsockopt()

On Thu, 10 Jul 2008, Rick Jones wrote:

> > In my own network benchmarking experience, I've generally gotten the
> > best performance results when the nuttcp application and the NIC
> > interrupts are on the same CPU, which I understood was because of
> > cache effects.
> 
> Interestingly enough I have a slightly different experience:
> 
> *) single-transaction, single-stream TCP_RR - best when app and NIC use 
> same core
> 
> *) bulk transfer - either TCP_STREAM or aggregate TCP_RR:
>    a) enough CPU on one core to reach max tput, best when same core
>    b) not enough, tput max when app and NIC on separate cores, 
> preferably cores sharing some cache
> 
> That is in the context of either maximizing throughput or minimizing 
> latency.  If the context is most efficient transfer, then in all cases 
> my experience thusfar agrees with yours.

Yes, I was talking about single stream bulk data transfers, where the
CPU was not a limiting factor (just barely when doing full 10-GigE
line rate transfers with 9000-byte jumbo frames).

On multiple stream tests there can be a benefit to spreading the load
across multiple cores.

						-Bill
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