From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756028Ab0AMQgL (ORCPT ); Wed, 13 Jan 2010 11:36:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756009Ab0AMQgK (ORCPT ); Wed, 13 Jan 2010 11:36:10 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:42328 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755974Ab0AMQgJ (ORCPT ); Wed, 13 Jan 2010 11:36:09 -0500 Date: Wed, 13 Jan 2010 17:35:51 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: Don Zickus , Cyrill Gorcunov , aris@redhat.com, linux-kernel@vger.kernel.org Subject: Re: introduce NMI_AUTO as nmi_watchdog option Message-ID: <20100113163551.GA10643@elte.hu> References: <20100111191633.GT24885@redhat.com> <20100111202729.GI4923@lenovo> <20100111203356.GU24885@redhat.com> <20100113093240.GC6739@elte.hu> <1263388422.4244.214.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1263388422.4244.214.camel@laptop> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=none autolearn=no SpamAssassin version=3.2.5 _SUMMARY_ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > On Wed, 2010-01-13 at 10:32 +0100, Ingo Molnar wrote: > > other architectures have NMI concepts as well, such as Sparc64. > > I think both sparc64 and ppc64 fake NMIs by playing games with hw IRQ > priorities and partial masks. But yes. > > One interesting 'feature' for the perf-nmi interaction is creating an idle > scheduling class for counters, because as long as there is a counter present > you can use his NMIs to drive the watchdog, but as soon as there are non > left, you need to install one. Yeah. I'd suggest to not complicate things with that initially - but to simply create a standalone event for it and 'waste' a counter on NMI generation. Later on it can indeed be a good feature to make the NMI watchdog 'seemless' in the sense of it not causing any wasted hw resources - it can piggyback on any existing NMI event. (as long as that event is at least ~1 HZ strong or so) Ingo