From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [TCP bug, regression] stuck distcc connections in latest -git Date: Thu, 24 Jul 2008 11:25:18 +0200 Message-ID: <20080724092517.GA31358@elte.hu> References: <20080724060448.GA10203@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: w@1wt.eu, davem@davemloft.net, davidn@davidnewall.com, torvalds@linux-foundation.org, akpm@linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stefanr@s5r6.in-berlin.de, rjw@sisk.pl, ilpo.jarvinen@helsinki.fi To: Herbert Xu Return-path: Received: from mx2.mail.elte.hu ([157.181.151.9]:56876 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751302AbYGXJ0I (ORCPT ); Thu, 24 Jul 2008 05:26:08 -0400 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: * Herbert Xu wrote: > Ingo Molnar wrote: > > > > the client (running 2.6.24) does periodic 120 seconds retransmits: > > > > 07:40:48.255452 IP dione.39201 > phoenix.distcc: . 1608:2144(536) ack 1 win 584007:40:48.255547 IP phoenix.distcc > dione.39201: . ack 2144 win 65535 > > 07:40:48.255564 IP dione.39201 > phoenix.distcc: . 67143:67679(536) ack 1 win 5840 > > 07:40:48.255648 IP phoenix.distcc > dione.39201: . ack 2144 win 65535 > > 07:42:48.255440 IP dione.39201 > phoenix.distcc: . 2144:2680(536) ack 1 win 5840 > > 07:42:48.255559 IP phoenix.distcc > dione.39201: . ack 2680 win 65535 > > 07:42:48.255570 IP dione.39201 > phoenix.distcc: . 67679:68215(536) ack 1 win 5840 > > 07:42:48.255659 IP phoenix.distcc > dione.39201: . ack 2680 win 65535 > > 07:44:48.255436 IP dione.39201 > phoenix.distcc: . 2680:3216(536) ack 1 win 584007:44:48.255570 IP phoenix.distcc > dione.39201: . ack 3216 win 65535 > > 07:44:48.255585 IP dione.39201 > phoenix.distcc: . 68215:68751(536) ack 1 win 5840 > > 07:44:48.255669 IP phoenix.distcc > dione.39201: . ack 3216 win 65535 > > OK, something's seriously screwed up on dione's kernel. Could you > please disable syncookies (which should enable SACK for you) and see > if the problem goes away? > > I think our Reno code may have been broken. ok, i've booted the latest kernel on dione and the builds are running on it now. It's using these settings currently: # cat /proc/sys/net/ipv4/tcp_syncookies 0 # cat /proc/sys/net/ipv4/tcp_sack 1 Just to make sure i have the right test-plan: assuming this suspected-good kernel is trouble-free for say 48 hours, i should be able to switch back to the suspected-broken variant, by doing: echo 1 > /proc/sys/net/ipv4/tcp_syncookies without rebooting the kernel, right? And then if the bug comes back again we've nailed it down to the area you suspect, correct? Ingo