Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755767Ab1DYWN6 (ORCPT ); Mon, 25 Apr 2011 18:13:58 -0400 Received: from mga01.intel.com ([192.55.52.88]:34986 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754607Ab1DYWN5 (ORCPT ); Mon, 25 Apr 2011 18:13:57 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,266,1301900400"; d="scan'208";a="683803426" Date: Mon, 25 Apr 2011 15:12:58 -0700 From: Andi Kleen To: Vince Weaver Cc: Ingo Molnar , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Peter Zijlstra , Stephane Eranian , Lin Ming , Arnaldo Carvalho de Melo , Thomas Gleixner , Peter Zijlstra , torvalds@linux-foundation.org Subject: Re: [PATCH 1/1] perf tools: Add missing user space support for config1/config2 Message-ID: <20110425221258.GA21442@tassilo.jf.intel.com> References: <1303407662-15564-1-git-send-email-acme@infradead.org> <1303407662-15564-2-git-send-email-acme@infradead.org> <20110422063429.GA16643@elte.hu> <20110422080604.GA22611@elte.hu> <20110425175444.GC28239@elte.hu> 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: 1230 Lines: 33 > The PAPI tool was using the perf_events interface in the 2.6.39-git > kernels to collect offcore response results by properly setting the > config1 register on Nehalem and Westmere machines. I already had some users for this functionality too. Offcore events are quite useful for various analysis: basically every time you have a memory performance problem -- especially a NUMA problem -- they can help you a lot tracking it down. They answer questions like "who accesses memory on another node" As far as I'm concerned b52c55c6a25e4515b5e075a989ff346fc251ed09 is a bad feature regression. > > Now it has been disabled for unclear reasons. Also unfortunately only partial. Previously you could at least write the MSR from user space through /dev/cpu/*/msr, but now the kernel randomly rewrites it if anyone else uses cache events. Right now I have some frontend scripts which are doing this, but it's really quite nasty. It's very sad we have to go through this. -Andi -- 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/