Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754562Ab0HDPqT (ORCPT ); Wed, 4 Aug 2010 11:46:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:61876 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753893Ab0HDPqS (ORCPT ); Wed, 4 Aug 2010 11:46:18 -0400 Date: Wed, 4 Aug 2010 11:45:52 -0400 From: Don Zickus To: Peter Zijlstra Cc: Robert Richter , Lin Ming , Ingo Molnar , Cyrill Gorcunov , "fweisbec@gmail.com" , "linux-kernel@vger.kernel.org" , "Huang, Ying" Subject: Re: A question of perf NMI handler Message-ID: <20100804154552.GR3353@redhat.com> References: <1280913670.20797.179.camel@minggr.sh.intel.com> <20100804100116.GH26154@erda.amd.com> <20100804140021.GN3353@redhat.com> <1280931093.1923.1194.camel@laptop> <20100804145203.GP3353@redhat.com> <1280934161.1923.1294.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1280934161.1923.1294.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 Content-Length: 1068 Lines: 27 On Wed, Aug 04, 2010 at 05:02:41PM +0200, Peter Zijlstra wrote: > So then the first interrupt will see 3+ overflows, return 3+, and will > thus eat 2+ NMIs, only one of which will be the pending interrupt, > leaving 1+ NMIs from other sources to consume unhandled. > > In which case Yinghai will have to press his NMI button 2+ times before > it registers. > > That said, that might be a better situation than always consuming > unknown NMIs.. Well if the worse case scenario is only one extra NMI, then I can change the logic in my patch to eat a max of 1 possible NMI instead of 2 as in the example you gave above. It still won't be 100% accurate but how often are people running perf where they need 4 counters, have to hit an external nmi button or run into broken firmware all at the same time? :-) Cheers, Don -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/