From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933175Ab1ERNwU (ORCPT ); Wed, 18 May 2011 09:52:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55675 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932837Ab1ERNwR (ORCPT ); Wed, 18 May 2011 09:52:17 -0400 Date: Wed, 18 May 2011 09:51:32 -0400 From: Don Zickus To: Ingo Molnar Cc: Mandeep Singh Baines , Andrew Morton , linux-kernel@vger.kernel.org, Marcin Slusarz , Peter Zijlstra , Frederic Weisbecker Subject: Re: [PATCH 4/4 v2] watchdog: configure nmi watchdog period based on watchdog_thresh Message-ID: <20110518135132.GL29881@redhat.com> References: <1305588901-8141-1-git-send-email-msb@chromium.org> <1305588901-8141-4-git-send-email-msb@chromium.org> <20110517071642.GF22305@elte.hu> <20110518034431.GC11023@google.com> <20110518083936.GF14805@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110518083936.GF14805@elte.hu> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 18, 2011 at 10:39:36AM +0200, Ingo Molnar wrote: > > * Mandeep Singh Baines wrote: > > > Ingo Molnar (mingo@elte.hu) wrote: > > > > > > * Mandeep Singh Baines wrote: > > > > > > > Before the conversion of the NMI watchdog to perf event, the watchdog > > > > timeout was 5 seconds. Now it is 60 seconds. For my particular application, > > > > netbooks, 5 seconds was a better timeout. With a short timeout, we > > > > catch faults earlier and are able to send back a panic. With a 60 second > > > > timeout, the user is unlikely to wait and will instead hit the power > > > > button, causing us to lose the panic info. > > > > > > That's an interesting observation. Have you been able to measure/observe this > > > effect somehow, or do you presume that users find 60 seconds too long? > > > > > > > Mostly intuition. There is a threshold beyond which the user will hit > > the power button. Not sure if its 20 seconds or 20 minutes. My feeling > > was that the 1 minute was too long. > > > > For a user experience perspective, a quick reboot also seems like a better > > experience than a one minute hang. Our systems boot in 8 seconds and restore > > the previous session so a reboot is almost not noticable. > > Indeed you definitely want it configurable and have the delay down to 5 or 10 > seconds, to correlate it with your boot delay. > > Personally i consider any hang over 1 second annoying so you might want to work > on that 8 seconds boot time some more, it's too long ;-) > > And any kernel code running with more than 1 second irqs off is a bug, plain > and simple. Not necessarily, but in those cases the code can use touch_nmi_watchdog (for example slow hardware, long print outs, etc). :-) Cheers, Don