From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raphael Hertzog Subject: Re: Constantly varying download rate with a complex xen networking setup, why? Date: Mon, 15 Jun 2009 18:02:54 +0200 Message-ID: <20090615160254.GA8550@rivendell> References: <20090615075313.GA22819@rivendell> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Netdev To: Ilpo =?iso-8859-15?Q?J=E4rvinen?= Return-path: Received: from arrakeen.ouaza.com ([212.85.152.62]:60523 "EHLO arrakeen.ouaza.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762114AbZFOQC5 (ORCPT ); Mon, 15 Jun 2009 12:02:57 -0400 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Le lundi 15 juin 2009, Ilpo J=E4rvinen a =E9crit : > On Mon, 15 Jun 2009, Raphael Hertzog wrote: >=20 > > My problem is that when I download a big file from the internet by = HTTP in > > the dom0, the download rate is not stable. It goes up progressively= and then > > stalls for a few seconds, and restart again going up progressively = (and > > all this in loop until the download is complete). >=20 > My guess: TCP sawtooth pattern and the associated loss recovery...? W= hat=20 > you describe here seems to match exactly to what is expected to happe= n=20 > because of it (I see this happening quite often actually). Why would this not happen for the same transfer done through a proxy (t= hat runs on the same machine but different domU)? > What is the size of the bottleneck buffer and base RTTs of the releva= nt > flows (HTTP, ssh)? How can I collect those information? > Please verify "blocking" using tcpdump or so. You may find out e.g. t= hat=20 I'll try to do so and follow-up. > network is not stalled but that out-of-order arrivals prevent=20 > applications from making progress. >=20 > If this matches with your problem, deploying AQM at the bottleneck wo= uld=20 > help. The bottleneck in my test setup is the ADSL connection and I don't cont= rol the ADSL router. Cheers, --=20 Rapha=EBl Hertzog -+- http://www.ouaza.com =46reexian : des d=E9veloppeurs Debian au service des entreprises http://www.freexian.com