From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 4 Jan 2003 22:45:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 4 Jan 2003 22:45:49 -0500 Received: from packet.digeo.com ([12.110.80.53]:26840 "EHLO packet.digeo.com") by vger.kernel.org with ESMTP id ; Sat, 4 Jan 2003 22:45:48 -0500 Message-ID: <3E17AC67.43923E08@digeo.com> Date: Sat, 04 Jan 2003 19:54:15 -0800 From: Andrew Morton X-Mailer: Mozilla 4.79 [en] (X11; U; Linux 2.5.54 i686) X-Accept-Language: en MIME-Version: 1.0 To: Linus Torvalds CC: Andi Kleen , davem@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [BENCHMARK] Lmbench 2.5.54-mm2 (impressive improvements) References: <3E1783D0.5A47A299@digeo.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 05 Jan 2003 03:54:16.0102 (UTC) FILETIME=[1DE93460:01C2B46E] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Linus Torvalds wrote: > > On Sat, 4 Jan 2003, Andrew Morton wrote: > > > > Looks like you're right. The indications are that this change > > has slowed context switches by ~5% on a PIII. The backout patch > > against 2.5.54 is below. Testing on a P4 would be useful. > > Hmm.. The backup patch doesn't handle single-stepping correctly: the > eflags cleanup singlestep patch later in the sysenter sequence _depends_ > on the stack (and thus thread) being right on the very first in-kernel > instruction. Well that's just a straight `patch -R' of the patch which added the wrmsr's. > That (along with benchmarking of system call numbers - the stack switch at > system call run-time ends up being quite expensive on a P4) was what made > me decide to do the traditional "write MSR in schedule" approach, even > though I agree that it would be much nicer to not have to rewrite that > stupid MSR all the time. > > It doesn't show up on lmbench (insufficient precision), but your AIM9 > numbers are quite interesting. Are they stable? > Seem to be, but more work is needed, including oprofiling. Andi is doing some P4 testing at present.