From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758598Ab3BVUvt (ORCPT ); Fri, 22 Feb 2013 15:51:49 -0500 Received: from cantor2.suse.de ([195.135.220.15]:46275 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757322Ab3BVUvs (ORCPT ); Fri, 22 Feb 2013 15:51:48 -0500 Date: Fri, 22 Feb 2013 21:51:44 +0100 From: Jan Kara To: Marcus Sundman Cc: Jan Kara , linux-kernel@vger.kernel.org Subject: Re: Debugging system freezes on filesystem writes Message-ID: <20130222205144.GA30600@quack.suse.cz> References: <20121107161730.GB23654@quack.suse.cz> <509C4339.2090506@hibox.fi> <509D014B.2080709@hibox.fi> <20121113135159.GA18651@quack.suse.cz> <50A592BA.8050709@hibox.fi> <20121121233021.GA8730@quack.suse.cz> <50B4E6F2.6010000@hibox.fi> <20121205153216.GF5706@quack.suse.cz> <51248C5F.4040606@hibox.fi> <5124B613.6040400@hibox.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5124B613.6040400@hibox.fi> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 20-02-13 13:40:03, Marcus Sundman wrote: > On 20.02.2013 10:42, Marcus Sundman wrote: > >On 05.12.2012 17:32, Jan Kara wrote: > >> I see. Maybe you could have something like > >>while true; do echo w >/proc/sysrq-trigger; sleep 10; done > >> running in the background? > > > >Sure, but I suspect it'll take until the worst is over before it > >manages to load and execute that "echo w". > > Here is a big run of sysrq-triggering, all while I was uncompressing > a big rar file causing the whole system to be utterly unusable. > NB: Even with realtime I/O-priority the sysrq couldn't be triggered > between 12:41:54 and 12:42:49, as you can see from the dmesg-3.txt > file. > > $ sudo ionice -c 1 su > # ionice > realtime: prio 4 > # while true; do sleep 10; echo w >/proc/sysrq-trigger; done > ^C > # tail -n +1700 /var/log/syslog >dmesg-3.txt > > http://sundman.iki.fi/dmesg-3.txt Thanks for the traces. I was looking at them and we seem to be always waiting for IO. There don't seem to be that much CPU load either. I'm actually starting to suspect the SSD in your laptop. The svctm field from iostat output shows it takes 1 second on average to complete an IO request. That is awfully slow given one request has ~180 KB of data on average. Ah, one more idea - can you post your /proc/mounts please? Honza -- Jan Kara SUSE Labs, CR