Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753482Ab0DUJW0 (ORCPT ); Wed, 21 Apr 2010 05:22:26 -0400 Received: from va3ehsobe005.messaging.microsoft.com ([216.32.180.15]:6153 "EHLO VA3EHSOBE005.bigfish.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753106Ab0DUJWZ (ORCPT ); Wed, 21 Apr 2010 05:22:25 -0400 X-SpamScore: -34 X-BigFish: VPS-34(zz1432P98dN936eM4015L62a3L9371Pzz1202hzzz32i2a8h43h61h) X-Spam-TCS-SCL: 0:0 X-WSS-ID: 0L17ZCY-02-4TF-02 X-M-MSG: Date: Wed, 21 Apr 2010 11:21:45 +0200 From: Robert Richter To: Stephane Eranian CC: Peter Zijlstra , Ingo Molnar , LKML Subject: Re: [PATCH 11/12] perf, x86: implement AMD IBS event configuration Message-ID: <20100421092145.GV11907@erda.amd.com> References: <1271190201-25705-1-git-send-email-robert.richter@amd.com> <1271190201-25705-12-git-send-email-robert.richter@amd.com> <20100420160557.GT11907@erda.amd.com> <20100421084700.GU11907@erda.amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) X-OriginalArrivalTime: 21 Apr 2010 09:21:46.0094 (UTC) FILETIME=[104448E0:01CAE134] X-Reverse-DNS: unknown Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1896 Lines: 47 On 21.04.10 11:02:42, Stephane Eranian wrote: > On Wed, Apr 21, 2010 at 10:47 AM, Robert Richter wrote: > > On 20.04.10 18:05:57, Robert Richter wrote: > >> > What is the problem with directly using the period here, rejecting > >> > any value that is off range or with bottom 4 bits set? > >> > >> Yes, I will create an updated version of this patch. > > > > Stephane, do you think having the lower 4 bits set is worth an EINVAL? > > I would rather ignore them since the accuracy is not really necessary > > compared to a range lets say from 100000 cycles? Otherwise this will > > make the setup of ibs much more complicated. The check could be moved > > to userland and generate a waring or so. > > Explain why you think it would be more complicated? > If I recall there is already a function to validate the attrs: > amd_pmu_hw_config(). > But may be you are talking about userland setup. > > Here is one argument why this might be important. Some people like to > know exactly > the sampling period because they use a particular value, like a prime > number. You > chopping off the bottom 4 bits could break this logic silently. Ok, I see your point. I was thinking of some decimal value used to set the sample period. You will then have to check if the lower 4 bits are set or not by doing a dec to hex conversion and so on. But I realized that multiples of 10000 can be devided by 16 and thus all lower 4 bits are always cleared. So, I will check the lower 4 bits and return an error if they are set. Thanks, -Robert -- Advanced Micro Devices, Inc. Operating System Research Center email: robert.richter@amd.com -- 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/