From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756703Ab1HENsJ (ORCPT ); Fri, 5 Aug 2011 09:48:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:29608 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751891Ab1HENsF (ORCPT ); Fri, 5 Aug 2011 09:48:05 -0400 Date: Fri, 5 Aug 2011 09:47:48 -0400 From: Don Zickus To: Ingo Molnar Cc: Peter Zijlstra , Robert Richter , Arnaldo Carvalho de Melo , LKML Subject: Re: [PATCH 4/7] perf, x86: Implement IBS interrupt handler Message-ID: <20110805134748.GK1972@redhat.com> References: <1311860812-28748-1-git-send-email-robert.richter@amd.com> <1311860812-28748-5-git-send-email-robert.richter@amd.com> <1311958726.5890.411.camel@twins> <20110801053201.GY4590@erda.amd.com> <1312212103.2617.495.camel@laptop> <20110801163823.GZ2581@redhat.com> <20110805095519.GC2420@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110805095519.GC2420@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 Fri, Aug 05, 2011 at 11:55:19AM +0200, Ingo Molnar wrote: > > I tried looking into but everytime I applied workarounds for Intel > > errata I wound up with more unknown NMIs and proving that a couple > > of them worked (with trace_printks) seemed elusive. I got > > frustrated and left it alone. > > > > But yeah, Intel's perf has so many errata that I think if you kick > > the box while running perf you can generate an unknown NMI. > > Hence the only sane approach is to just tolerate spurious NMIs and > only annoy the user with them if there's *way* too many of them or > so. That may work if we can determine if the user is running perf or not. But on older systems (like pre-Nehalem), sometimes the only way a system can signal a platform error is through a single unknown NMI. I would be afraid we might lose one of those if we 'tolerate' unknown NMIs. So far I have only noticed perf generating 'unknown NMIs' on high volume usage (like multiple counters). For the casual user it has been ok so far. Cheers, Don