From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Snook Subject: Re: RFC: Nagle latency tuning Date: Mon, 22 Sep 2008 19:00:08 -0400 Message-ID: <48D82378.4000306@redhat.com> References: <20080922.040912.193700258.davem@davemloft.net> <20080922203042.GY25711@one.firstfloor.org> <48D81A95.5080207@redhat.com> <20080922.152615.215876787.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: andi@firstfloor.org, rick.jones2@hp.com, netdev@vger.kernel.org To: David Miller Return-path: Received: from mx2.redhat.com ([66.187.237.31]:33283 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753606AbYIVW7o (ORCPT ); Mon, 22 Sep 2008 18:59:44 -0400 In-Reply-To: <20080922.152615.215876787.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: David Miller wrote: > From: Chris Snook > Date: Mon, 22 Sep 2008 18:22:13 -0400 > >> How horrendous of a layering violation would it be to attach TCP >> performance parameters (either user-supplied or based on interface >> stats) to route table entries, like route metrics but intended to >> guide TCP autotuning? It seems like it shouldn't be that hard to >> teach TCP that it doesn't need to optimize my lo connections much, >> and that it should be optimizing my eth0 subnet connections for >> lower latency and higher bandwidth than the connections that go >> through my gateway into the great beyond. > > We already do this for other TCP connection parameters, and I tend to > think these delack/ato values belong there too. > > If we add a global knob, people are just going to turn it on even if > they are also connected to the real internet on the system rather than > only internal networks they completely control. > > That tends to cause problems. It gets an entry on all of these bogus > "Linux performance tuning" sections administrators read from the > various financial messaging products. So everyone does it without > thinking and using their brains. I agree 100%. Could you please point me to an example of a connection parameter that gets tuned and cached this way, so I can experiment with it? -- Chris