From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758922AbYDKHn6 (ORCPT ); Fri, 11 Apr 2008 03:43:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756084AbYDKHnv (ORCPT ); Fri, 11 Apr 2008 03:43:51 -0400 Received: from smtp-out03.alice-dsl.net ([88.44.63.5]:23750 "EHLO smtp-out03.alice-dsl.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755189AbYDKHnu (ORCPT ); Fri, 11 Apr 2008 03:43:50 -0400 To: Karsten Wiese Cc: linux-kernel@vger.kernel.org, Ingo Molnar Subject: Re: [PATCH] x86: set_cyc2ns_scale() remove tsc_now and ns_now From: Andi Kleen References: <200804102331.11815.fzu@wemgehoertderstaat.de> Date: Fri, 11 Apr 2008 09:42:48 +0200 In-Reply-To: <200804102331.11815.fzu@wemgehoertderstaat.de> (Karsten Wiese's message of "Thu, 10 Apr 2008 23:31:11 +0200") Message-ID: <873apsn8g7.fsf@basil.nowhere.org> User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-OriginalArrivalTime: 11 Apr 2008 07:36:03.0846 (UTC) FILETIME=[B24F0A60:01C89BA6] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Karsten Wiese writes: > Both are unused and the functions rdtscll() and __cycles_2_ns() don't have > side-effects. I don't think you should remove those. At some point the offset needs to be reset when the frequency scale changes for obvious reasons, and that needs to be fixed, not the code removed. Right now you'll get scheduling inconsistencies during frequency changes on !constant_tsc CPUs. (actually it is still the wrong time -- really needs a grace period during which the TSC is not used ftp://firstfloor.org/pub/ak/quilt/patches/sched-clock implemented some of these ideas against an older kernel) -Andi