From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McManus Subject: RE: 2.6.27 problem with shaping using netem/ifb (regression?) [TSO] Date: Wed, 01 Oct 2008 21:55:42 -0400 Message-ID: <1222912542.6395.30.camel@tng> References: <1222902286.6395.22.camel@tng> <36D9DB17C6DE9E40B059440DB8D95F52064FB007@orsmsx418.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: "Brandeburg, Jesse" Return-path: Received: from linode.ducksong.com ([64.22.125.164]:34065 "EHLO linode.ducksong.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751642AbYJBBzp (ORCPT ); Wed, 1 Oct 2008 21:55:45 -0400 In-Reply-To: <36D9DB17C6DE9E40B059440DB8D95F52064FB007@orsmsx418.amr.corp.intel.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2008-10-01 at 18:42 -0700, Brandeburg, Jesse wrote: > > Any thoughts on where to look? I hope attaching the script is helpful > - > > it is pretty self evident when running it if things are working ok. > > This > > is all on amd64 if that is relevant. > > Have you tried disabling TSO and/or GSO on the loopback device? for some reason with loopback that didn't come to mind. It's a good suggestion, and indeed is the crux of the problem. Thanks! Disabling TSO (ethtool -K lo tso off) fixes the problem. GSO has no impact. probly not relevant, but worth noting - the scripts also set the MTU of lo to 1500 down from the default 16436