netdev - Re: Very low latency TCP for clusters

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Message-ID: <1279603570.2458.66.camel@edumazet-laptop>
Date:	Tue, 20 Jul 2010 07:26:10 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	netdev@...r.kernel.org, Rick Jones <rick.jones2@...com>
Subject: Re: Very low latency TCP for clusters

Le lundi 19 juillet 2010 à 16:37 -0700, Tom Herbert a écrit :

> That's pretty pokey ;-) I see numbers around 25 usecs between to
> machines, this is with TCP_NBRR.  With TCP_RR it's more like 35 usecs,
> so eliminating the scheduler is already a big reduction.  That leaves
> 18 usecs in device time, interrupt processing, network, and cache
> misses; 7 usecs in TCP processing, user space.  While 5 usecs is an
> aggressive goal, I am not ready to concede that there's an
> architectural limit in either NICs, TCP, or sockets that can't be
> overcome.

Last time I tried TCP_NBRR, it was not working (not even compiled in), I
guess I should submit a bug report to Rick ;)



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