From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Hannemann Subject: Re: scp stalls mysteriously Date: Thu, 03 Dec 2009 14:37:03 +0100 Message-ID: <4B17BEFF.2030309@nets.rwth-aachen.de> References: <20091130213727.2f4047d2@houba> <20091201211945.505d3c98@houba> <20091202085925.472136e2@houba> <20091202154403.GB30730@sd-11162.dedibox.fr> <20091202183451.173db5f2@houba> <4B16BD58.3040802@tvk.rwth-aachen.de> <20091203085933.GD30730@sd-11162.dedibox.fr> <20091203131127.131e9122@houba> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: =?UTF-8?B?SWxwbyBKw6RydmluZW4=?= , Damian Lukowski , Netdev , Asdo , David Miller , Eric Dumazet , Herbert Xu , Greg KH To: Frederic Leroy Return-path: Received: from mta-1.ms.rz.RWTH-Aachen.DE ([134.130.7.72]:64149 "EHLO mta-1.ms.rz.rwth-aachen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755970AbZLCNhP (ORCPT ); Thu, 3 Dec 2009 08:37:15 -0500 Received: from ironport-out-1.rz.rwth-aachen.de ([134.130.5.40]) by mta-1.ms.rz.RWTH-Aachen.de (Sun Java(tm) System Messaging Server 6.3-7.04 (built Sep 26 2008)) with ESMTP id <0KU200IA8WI9MJ70@mta-1.ms.rz.RWTH-Aachen.de> for netdev@vger.kernel.org; Thu, 03 Dec 2009 14:37:21 +0100 (CET) In-reply-to: <20091203131127.131e9122@houba> Sender: netdev-owner@vger.kernel.org List-ID: =46rederic Leroy wrote: > Le Thu, 3 Dec 2009 12:29:39 +0200 (EET), > "Ilpo J=C3=A4rvinen" a =C3=A9crit : >=20 >> Opinions, Dave?, Greg? >> >> Now back to the issue... >> >> You said in the other mail that "All further test are on linus-stabl= e=20 >> tree.", which has this contradiction that Linus does not maintain >> stable trees. Which exactly was the tree used for the .9. test >=20 > Sorry I'm confused and so confuse you. > For .9 .10 and now I'm only using :=20 > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git > =20 >> Linus' tree or the 2.6.31 stable tree? I suppose the former since th= e >> revert wouldn't apply to 2.6.31 so I just want to confirm. >=20 > I didn't keep the source of the old 2.6.31 kernel I have.=20 > So it's either=20 > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git > or > git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-2.6-stable= =2Egit >=20 >> Nice thinking indeed Damian, thanks. ...But but, where exactly did >> you print? ...There are multiple returns and the return false branch >> is expected to have a zero retrans_stamp in a typical case but that >> is not a problem because we never use the value. >=20 > Here is the code : > http://www.starox.org/pub/scp_stall/printk_retrans_stamp.patch >=20 >> ...Anyway, if I'm wrong with my suspicion and it still holds that we >> have zero retrans_stamp in the substraction too, it could have >> something to do with this snippet: >> >> static void tcp_try_to_open(struct sock *sk, int flag) >> { >> struct tcp_sock *tp =3D tcp_sk(sk); >> >> tcp_verify_left_out(tp); >> >> if (!tp->frto_counter && tp->retrans_out =3D=3D 0) >> tp->retrans_stamp =3D 0; >> >> ...It bit me last time when FRTO was enabled after very small >> modification (without running a full verification after the trivial >> looking modification). ...So I've worked around this clearing for >> FRTO as you can see :-). >=20 > :) >=20 >> Also, we have the another mystery to be solved, the fast >> retransmission is not triggered for some reason (or alternatively no= t >> captured in to a log), even in the working .9. case. It would be eas= y >> to see whether it works at all from TCP point of view by looking int= o >> mibs once you have have some transfers in a working configuration: >> >> grep -A1 TCP /proc/net/netstat >=20 > I will try this evening. I can do test only outside office hours. If you don't mind, could you also post the output of "sysctl -a | grep net.ipv4.tcp", please. The tars you posted (proc_net_tcp.tbz2) seem to be empty. Thanks. Best regards, Arnd