netdev - Re: Minimizing TCP latency

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Message-ID: <1269840891.2256.28.camel@edumazet-laptop>
Date:	Mon, 29 Mar 2010 07:34:51 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ben Hoyt <benhoyt@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Minimizing TCP latency

Le lundi 29 mars 2010 à 16:24 +1300, Ben Hoyt a écrit :
> > I'm happy to receive some pointers via this list [...]
> 
> Sorry, I should also have posted more about what I've done in terms of
> reducing latency so far:
> 
> * We've already got TCP_NODELAY activated.

One machine sends messages, and messages are not aknowledged by other
part ? Is it one way communication ?

> 
> * We've also turned off interrupt coalescing on the network card (for
> example, see http://www.29west.com/docs/THPM/latency-interrupt-coalescing.html).
> 
> * We've modified our process's CPU affinity so it runs on a core by
> itself, reducing interrupt-handling latency slightly further.
> 
> * Our code is written in C, and we've tried to keep it as close to the
> kernel's socket calls as possible.
> 



So we're currently looking further into ways to reduce latency, which
> currently looks like it'll mean digging deeper into the kernel's
> networking options and innards.
> 
> FYI, we're using RHE release 4 and kernel version 2.6.9 on x86_64 machines.

What are the targets ?  (time constraints)

Mono threaded application handling one tcp flow ?

Are you handling a very light load on few flows, or many flows ? 

Are machines all in the same LAN ?


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