From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932210Ab1GELXA (ORCPT ); Tue, 5 Jul 2011 07:23:00 -0400 Received: from merlin.infradead.org ([205.233.59.134]:60566 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932165Ab1GELW6 convert rfc822-to-8bit (ORCPT ); Tue, 5 Jul 2011 07:22:58 -0400 Subject: Re: [PATCH 1/4] perf, x86: Add Intel Nehalem/Westmere uncore pmu From: Peter Zijlstra To: Andi Kleen Cc: Lin Ming , Ingo Molnar , Stephane Eranian , Arnaldo Carvalho de Melo , linux-kernel In-Reply-To: <20110704215706.GH15637@one.firstfloor.org> References: <1309421396-17438-1-git-send-email-ming.m.lin@intel.com> <1309421396-17438-2-git-send-email-ming.m.lin@intel.com> <20110630165849.GE23059@one.firstfloor.org> <1309761541.18875.40.camel@minggr.sh.intel.com> <20110704215706.GH15637@one.firstfloor.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Tue, 05 Jul 2011 13:22:34 +0200 Message-ID: <1309864954.3282.61.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2011-07-04 at 23:57 +0200, Andi Kleen wrote: > > > There are no NMIs without sampling, so at least the comment seems bogus. > > > Perhaps the code could be a bit simplified now without atomics. > > > > I'm not sure if uncore PMU interrupt need to be enabled for counting > > only. What do you think? > > Only for overflow handling to accumulate into a larger counter, but it doesn't > need to be an NMI for that. Uncore is hooked into the regular PMI, and since we wire that to the NMI the uncore will always be NMI too. > But it's not strictly required I would say, > 44(?) bits are probably enough for near all use cases. 44bits is in the hours range for pure cycle counts, which is so-so. I bet you're going to be very annoyed when you find your counters are wrecked after your 5 hour test run finishes.