Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751379Ab3IPPlv (ORCPT ); Mon, 16 Sep 2013 11:41:51 -0400 Received: from mail-bk0-f41.google.com ([209.85.214.41]:49271 "EHLO mail-bk0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751025Ab3IPPlu (ORCPT ); Mon, 16 Sep 2013 11:41:50 -0400 Date: Mon, 16 Sep 2013 17:41:46 +0200 From: Ingo Molnar To: eranian@gmail.com Cc: Peter Zijlstra , Linus Torvalds , Linux Kernel Mailing List , Arnaldo Carvalho de Melo , Thomas Gleixner , Andi Kleen Subject: Re: PEBS bug on HSW: "Unexpected number of pebs records 10" (was: Re: [GIT PULL] perf changes for v3.12) Message-ID: <20130916154146.GA6470@gmail.com> References: <20130909100544.GI31370@twins.programming.kicks-ass.net> <20130910115306.GA6091@gmail.com> <20130910133845.GB7537@gmail.com> <20130910142942.GB8388@gmail.com> <20130910171449.GA10812@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Content-Length: 1623 Lines: 45 * Stephane Eranian wrote: > Hi, > > Some updates on this problem. > I have been running tests all week-end long on my HSW. > I can reproduce the problem. What I know: > > - It is not linked with callchain > - The extra entries are valid > - The reset values are still zeroes > - The problem does not happen on SNB with the same test case > - The PMU state looks sane when that happens. > - The problem occurs even when restricting to one CPU/core (taskset -c 0-3) > > So it seems like the threshold is ignored. But I don't understand where > there reset values are coming from. So it looks more like a bug in > micro-code where under certain circumstances multiple entries get > written. Either multiple entries are written, or the PMI/NMI is not asserted as it should be? > Something must be happening with the interrupt or HT. I will disable HT > next and also disable the NMI watchdog. Yes, interaction with the NMI watchdog events might also be possible. If it's truly just the threshold that is broken occasionally in a statistically insignificant manner then the bug is relatively benign and we could work it around in the kernel by ignoring excess entries. In that case we should probably not annoy users with the scary kernel warning and instead increase a debug count somewhere so that it's still detectable. Thanks, Ingo -- 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/