Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 17 Dec 2002 16:45:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 17 Dec 2002 16:45:39 -0500 Received: from to-velocet.redhat.com ([216.138.202.10]:38387 "EHLO touchme.toronto.redhat.com") by vger.kernel.org with ESMTP id ; Tue, 17 Dec 2002 16:45:38 -0500 Date: Tue, 17 Dec 2002 16:53:37 -0500 From: Benjamin LaHaise To: "H. Peter Anvin" Cc: dean gaudet , Linus Torvalds , Dave Jones , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: Intel P6 vs P7 system call performance Message-ID: <20021217165337.F10781@redhat.com> References:

<3DFF76D7.2050403@transmeta.com> <20021217163954.D10781@redhat.com> <3DFF9A23.1090607@transmeta.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <3DFF9A23.1090607@transmeta.com>; from hpa@transmeta.com on Tue, Dec 17, 2002 at 01:41:55PM -0800 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 848 Lines: 21 On Tue, Dec 17, 2002 at 01:41:55PM -0800, H. Peter Anvin wrote: > > No, just take the number of context switches before and after the attempt > > to read the time of day. > How do you do that from userspace, atomically? A counter in the shared > page? Yup. You need some shared data for the TSC offset such anyways, so moving the context switch counter onto such a page won't be much of a problem. Using the %tr trick to get the CPU number would allow for some of these data structures to be per-cpu without incurring any LOCK overhead, too. -ben -- "Do you seek knowledge in time travel?" - 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/