From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933947AbXDBGuv (ORCPT ); Mon, 2 Apr 2007 02:50:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933962AbXDBGuu (ORCPT ); Mon, 2 Apr 2007 02:50:50 -0400 Received: from mx1.suse.de ([195.135.220.2]:33568 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933947AbXDBGum (ORCPT ); Mon, 2 Apr 2007 02:50:42 -0400 From: Andi Kleen Organization: SUSE Linux Products GmbH, Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg) To: Jeremy Fitzhardinge Subject: Re: [patch 17/17] Add a sched_clock paravirt_op Date: Mon, 2 Apr 2007 08:50:32 +0200 User-Agent: KMail/1.9.5 Cc: Andrew Morton , virtualization@lists.osdl.org, lkml , Zachary Amsden , Dan Hecht , john stultz References: <20070402055652.610711908@goop.org> <200704020809.42373.ak@suse.de> <4610A70A.7010105@goop.org> In-Reply-To: <4610A70A.7010105@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200704020850.32274.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Monday 02 April 2007 08:47, Jeremy Fitzhardinge wrote: > Andi Kleen wrote: > > I think it would be much cleaner if you didn't implement your own sched_clock, > > but you adjust ns_base/last_tsc to account for your lost cycles. > > This could be done cleanly by adding a new function to sched-clock.c > > Possibly such a function could be used by other parts of the kernel > > in the future too. > > > > Cleaner how? This seems pretty to me. Xen can return a > clock measuring unstolen nanoseconds, Do you also get a clock for stolen nanoseconds? > which maps directly to the > sched_clock interface, doesn't need any of the existing sched_clock > code. I suppose I could map the Xen interface onto some abstract > "cycles" notion and hook it into the tsc machinery, but it seems like it > would be a forced fit. In general, my approach has been to choose the > higher-level interface over a lower-level one, all other things being equal. No need for cycles, you could just subtract the stolen ns if you can get those. -Andi