From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: Minimizing TCP latency Date: Mon, 29 Mar 2010 16:23:49 +0100 Message-ID: <1269876229.2092.3.camel@achroite.uk.solarflarecom.com> References: <7c93bf1e1003281829h3ddba989w198df86ac9f2d27c@mail.gmail.com> <7c93bf1e1003282024p75e70011j31577b42f29cc153@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: Ben Hoyt Return-path: Received: from exchange.solarflare.com ([216.237.3.220]:40740 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750902Ab0C2PXw (ORCPT ); Mon, 29 Mar 2010 11:23:52 -0400 In-Reply-To: <7c93bf1e1003282024p75e70011j31577b42f29cc153@mail.gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2010-03-29 at 16:24 +1300, Ben Hoyt wrote: > > 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. > > * 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. Choose low-latency NICs. Read the tuning guide, but run your own benchmarks. > FYI, we're using RHE release 4 and kernel version 2.6.9 on x86_64 machines. You're not going to get much help here in working on that kernel. Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Communications Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.