Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760505AbXHTTMu (ORCPT ); Mon, 20 Aug 2007 15:12:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754224AbXHTTMh (ORCPT ); Mon, 20 Aug 2007 15:12:37 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:44353 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754206AbXHTTMg (ORCPT ); Mon, 20 Aug 2007 15:12:36 -0400 Date: Mon, 20 Aug 2007 21:12:08 +0200 From: Ingo Molnar To: Martin Schwidefsky Cc: Christian Borntraeger , Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, Jan Glauber , heiko.carstens@de.ibm.com, Paul Mackerras Subject: Re: [accounting regression since rc1] scheduler updates Message-ID: <20070820191208.GB3714@elte.hu> References: <20070812163225.GA11996@elte.hu> <200708141037.48001.borntraeger@de.ibm.com> <20070820154529.GA300@elte.hu> <1187629438.8541.40.camel@localhost> <20070820180810.GA25160@elte.hu> <1187634782.4028.10.camel@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1187634782.4028.10.camel@localhost> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7-deb -1.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1562 Lines: 31 * Martin Schwidefsky wrote: > > If a virtual CPU is idle then i think the "real = steal, virtual = > > 0" way of thinking about idle looks a bit unnatural to me - wouldnt > > it be better to think in terms of "steal = 0, virtual = real" ? > > Basically a virtual CPU can idle at "perfect speed", without the > > host "stealing" any cycles from it. And with that way of thinking, > > if s390 passed in the real-idle-time value to the new callbacks > > below it would all fall into place. Hm? > > How you think about an idle cpu depends on your viewpoint. The source > for the virtual cpu time on s390 is the cpu timer. This timer is > stopped when a virtual cpu looses the physical cpu, so it seems > natural to me to think that real=steal, virtual=0 because the cpu > timer is stopped while the cpu is idle. The other way of thinking > about it is as valid though. my thinking is this: the structure of "idle time" only matters if it can be observed from "within" a virtual machine - via timers. Are on s390 any of the typical app-visible timers (timer_list, etc.) driven by the virtual tick? [which slows down if a virtual CPU is scheduled away by the host/monitor/hypervisor?] Or is the virtual tick only affecting scheduling/cpu-accounting statistics in essence? Ingo - 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/