Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262260AbUKQKok (ORCPT ); Wed, 17 Nov 2004 05:44:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262261AbUKQKok (ORCPT ); Wed, 17 Nov 2004 05:44:40 -0500 Received: from aun.it.uu.se ([130.238.12.36]:34031 "EHLO aun.it.uu.se") by vger.kernel.org with ESMTP id S262260AbUKQKnn (ORCPT ); Wed, 17 Nov 2004 05:43:43 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16795.11086.38315.444645@alkaid.it.uu.se> Date: Wed, 17 Nov 2004 11:43:26 +0100 From: Mikael Pettersson To: dean gaudet Cc: "Pallipadi, Venkatesh" , john stultz , lkml Subject: RE: [patch] prefer TSC over PM Timer In-Reply-To: References: <88056F38E9E48644A0F562A38C64FB60035C613D@scsmsx403.amr.corp.intel.com> X-Mailer: VM 7.17 under Emacs 20.7.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1374 Lines: 29 dean gaudet writes: > On Tue, 16 Nov 2004, Pallipadi, Venkatesh wrote: > > > I think trying to remove repeated inl()'s in read_pmtmr is a better > > fix for this issue. As John mentioned in other thread, we should do > > repeated reads only when something looks broken. Not always. > > that would be a nice improvement... then timer_pm will only be 3x as slow > as timer_tsc instead of 10x slower :) it's still a lot of unnecessary > overhead for many systems, and unfortunately this is a real performance > problem (albeit exaggerated by code which is overzealous in its use of > gettimeofday()). > > on a tangent... has the local apic timer ever been considered? it's fixed > rate, and my measurements show it in the same performance ballpark as TSC. > > i know that all p3, p-m, p4, k8 and efficeon have local APIC, but i'm not > sure if k7 (other than k7 smp parts of course) have local apics... so i'm > not sure how widespread it is compared to pm-timer. All K7/K8s except the very first K7 Model 1 have local APICs. There is no difference between UP and MP parts in this respect. /Mikael - 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/