From mboxrd@z Thu Jan 1 00:00:00 1970 From: Carsten Wolff Subject: Re: TCP fast retransmit Date: Tue, 13 Dec 2011 15:59:17 +0100 Message-ID: <201112131559.17969.carsten@wolffcarsten.de> References: <2D9E1426-D432-4D08-BF28-FD2615AAEDBA@mpi-bpc.mpg.de> <53E23320-FE3E-4B9C-95FA-132F75E89E83@mpi-bpc.mpg.de> <1323786660.2744.1.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "Esztermann, Ansgar" , "netdev@vger.kernel.org" To: Eric Dumazet Return-path: Received: from h1346787.stratoserver.net ([85.214.49.182]:34433 "EHLO h1346787.stratoserver.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750942Ab1LMO7n convert rfc822-to-8bit (ORCPT ); Tue, 13 Dec 2011 09:59:43 -0500 In-Reply-To: <1323786660.2744.1.camel@edumazet-laptop> Sender: netdev-owner@vger.kernel.org List-ID: On Tuesday 13 December 2011, you wrote: > Le mardi 13 d=C3=A9cembre 2011 =C3=A0 15:05 +0100, Esztermann, Ansgar= a =C3=A9crit : > > On Dec 9, 2011, at 17:31 , Eric Dumazet wrote: > > >>> It seems you have a lot of packet reorders. > > >>>=20 > > >>> Are you using multipath or some channel bonding ? > > >>=20 > > >> Not that I am aware of (i.e. not on our end). However, the conne= ction > > >> will probably routed through a firewall. I will have to check if= it is > > >> configured to avoid reordering. > > >=20 > > > Is it a linux based firewall ? > >=20 > > No, it's Cisco. >=20 > OK >=20 > You could increase /proc/sys/net/ipv4/tcp_reordering from 3 to 16 >=20 > (Not sure it will change anything, since its kinda dynamic for a tcp > session) It's dynamic, but the sysctl changes the dynamic a lot, because its the= =20 minimum value of the dupack threshold. Be sure not to set this too high= , or=20 you will risk a lot of RTOs, which should kill performance even more=20 thoroughly. Carsten