Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 17 Dec 2002 16:34:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 17 Dec 2002 16:34:20 -0500 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:34064 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id ; Tue, 17 Dec 2002 16:33:51 -0500 Message-ID: <3DFF9A23.1090607@transmeta.com> Date: Tue, 17 Dec 2002 13:41:55 -0800 From: "H. Peter Anvin" Organization: Transmeta Corporation User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3a) Gecko/20021119 X-Accept-Language: en, sv MIME-Version: 1.0 To: Benjamin LaHaise CC: dean gaudet , Linus Torvalds , Dave Jones , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: Intel P6 vs P7 system call performance References:

<3DFF76D7.2050403@transmeta.com> <20021217163954.D10781@redhat.com> In-Reply-To: <20021217163954.D10781@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 763 Lines: 26 Benjamin LaHaise wrote: > On Tue, Dec 17, 2002 at 11:11:19AM -0800, H. Peter Anvin wrote: > >>>against 0xfffffxxx and "rollback" (or complete) any incomplete >>>gettimeofday call prior to saving a task's state. but i bet that test is >>>undesirable on all interrupt paths. >>> >> >>Exactly. This is a real problem. > > > 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? -hpa - 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/