From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755997Ab0AMQ1x (ORCPT ); Wed, 13 Jan 2010 11:27:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755862Ab0AMQ1w (ORCPT ); Wed, 13 Jan 2010 11:27:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45805 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755850Ab0AMQ1v (ORCPT ); Wed, 13 Jan 2010 11:27:51 -0500 Date: Wed, 13 Jan 2010 11:25:34 -0500 From: Don Zickus To: Peter Zijlstra Cc: Ingo Molnar , Cyrill Gorcunov , aris@redhat.com, linux-kernel@vger.kernel.org Subject: Re: introduce NMI_AUTO as nmi_watchdog option Message-ID: <20100113162534.GX24885@redhat.com> 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) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 13, 2010 at 02:13:42PM +0100, 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. Interesting idea. How can I guarantee the frequency of the NMI I want to piggyback off of? A breakpoint that takes an hour to trigger may not be the best NMI to use? Then again I am still trying to understand the perf event code a little better. Cheers, Don