From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758148Ab0ERTdo (ORCPT ); Tue, 18 May 2010 15:33:44 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:21992 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752384Ab0ERTdl convert rfc822-to-8bit (ORCPT ); Tue, 18 May 2010 15:33:41 -0400 MIME-Version: 1.0 Message-ID: Date: Tue, 18 May 2010 12:00:34 -0700 (PDT) From: Dan Magenheimer To: "H. Peter Anvin" Cc: Peter Zijlstra , Andi Kleen , Arjan van de Ven , Thomas Gleixner , Venkatesh Pallipadi , Ingo Molnar , chris.mason@oracle.com, linux-kernel@vger.kernel.org Subject: RE: [PATCH] x86: Export tsc related information in sysfs References: <1273887635-27610-1-git-send-email-venki@google.com>> <87tyq9mqrz.fsf@basil.nowhere.org>> <35aa841b-e151-424d-b1c1-0c03dbcae5cc@default>> <20100515121424.38f5b389@infradead.org>> > <20100515224305.17a04022@infradead.org>> > <5adf3fee-0f7b-4039-b13f-619640cc4b88@default>> <20100516220638.2baf315d@infradead.org> <1274176698.5605.7358.camel@twins>> <20100518112509.GD22675@basil.fritz.box> <1274183935.5605.7726.camel@twins>> <4BF2C30F.6030502@zytor.com> <1274201536.5605.8347.camel@twins> <4BF2C881.60807@zytor.com> <1dc4abc2-6455-4b95-90f6-c86bf56ff39a@default 4BF2E0A2.6030209@zytor.com> In-Reply-To: <4BF2E0A2.6030209@zytor.com> X-Priority: 3 X-Mailer: Oracle Beehive Extensions for Outlook 1.5.1.5.2 (401224) [OL 12.0.6514.5000] Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Auth-Type: Internal IP X-Source-IP: rcsinet15.oracle.com [148.87.113.117] X-CT-RefId: str=0001.0A090206.4BF2EB7C.0090:SCFMA4539811,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: H. Peter Anvin [mailto:hpa@zytor.com] > Subject: Re: [PATCH] x86: Export tsc related information in sysfs > > On 05/18/2010 10:49 AM, Dan Magenheimer wrote: > > > > (Though I expect tglx/arjan/andi/mingo to disagree with this proposal > > for similar reasons as the original one that started this thread...) > > I'll add another reason to disagree: exporting these as sysfs variables > is non-atomic, but these are really only useful when atomically read as > a unit. Which "these"? The counters? I would think the primary use of the counters is to diagnose extreme problem cases, not to differentiate whether a system or process did exactly 27 vs 28 rdtsc's, so I don't see why atomic read is at all necessary. Or did I miss your point entirely?