From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758944Ab0J0O0b (ORCPT ); Wed, 27 Oct 2010 10:26:31 -0400 Received: from smtp-out-231.synserver.de ([212.40.180.231]:1143 "HELO smtp-out-228.synserver.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1755177Ab0J0O03 (ORCPT ); Wed, 27 Oct 2010 10:26:29 -0400 X-SynServer-TrustedSrc: 1 X-SynServer-AuthUser: markus@trippelsdorf.de X-SynServer-PPID: 1103 Date: Wed, 27 Oct 2010 16:26:22 +0200 From: Markus Trippelsdorf To: john stultz Cc: Thomas Gleixner , Borislav Petkov , "linux-kernel@vger.kernel.org" , "hpa@linux.intel.com" , Ingo Molnar , Andreas Herrmann Subject: Re: Clocksource tsc unstable (delta = -8589361717 ns) in current git Message-ID: <20101027142622.GA1555@arch.trippelsdorf.de> References: <20101026112052.GA1672@arch.trippelsdorf.de> <20101026131843.GC17852@aftab> <20101026135808.GB1672@arch.trippelsdorf.de> <1288120736.2645.9.camel@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1288120736.2645.9.camel@localhost> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 26, 2010 at 12:18:56PM -0700, john stultz wrote: > On Tue, 2010-10-26 at 17:48 +0200, Thomas Gleixner wrote: > > On Tue, 26 Oct 2010, Markus Trippelsdorf wrote: > > > On Tue, Oct 26, 2010 at 03:18:43PM +0200, Borislav Petkov wrote: > > > > otherwise, I don't see anything strange in your dmesg. Unless tglx has a > > > > better idea, I'd ask you to bisect it. 5618 changesets shouldn't be that > > > > much but I don't know, if the issue appears every several hours it could > > > > still be tedious. > > > > > > That would be a several week long process, as the issue appears ~ every > > > 2 days here on this machine running 24/7. > > > > There is only a single commit in that area post 2.6.36: > > > > 8af3c153baf95374eff20a37f00c59a295b52756 > > > > But I have a hard time how this should make this happen. John ? > > Yea, that one doesn't look connected to me. > > There have been a few cases that I've seen where we can get false > positives for bad TSCs due to the watchdog clocksource having problems > (or the clocksource watchdog thread getting delayed for such a long time > the watchdog clocksource wraps and we then can't validly compare the two > - although this would be hard to trigger with non-rt kernels). I think the remark above points in the right direction, because the mysterious slowness happened again today (and this time on a vanilla git kernel). But this time no "Clocksource tsc unstable" message appeared in the kernel log. My system recovered by itself and after 2 minutes of slowness it was usable again. (The symptoms were the same as desribed in my first mail: Second long delays when typing and switching from X to the console took many seconds.) Is there anything I can do to pinpoint the cause of this slowdown should it happen again? (Maybe a perf timechart?) -- Markus