Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756551AbXHUJsa (ORCPT ); Tue, 21 Aug 2007 05:48:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753548AbXHUJsW (ORCPT ); Tue, 21 Aug 2007 05:48:22 -0400 Received: from ozlabs.org ([203.10.76.45]:59603 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754578AbXHUJsV (ORCPT ); Tue, 21 Aug 2007 05:48:21 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <18122.46304.556919.568565@cargo.ozlabs.ibm.com> Date: Tue, 21 Aug 2007 19:48:16 +1000 From: Paul Mackerras To: Ingo Molnar Cc: Martin Schwidefsky , Christian Borntraeger , Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, Jan Glauber , heiko.carstens@de.ibm.com Subject: Re: [accounting regression since rc1] scheduler updates In-Reply-To: <20070821093434.GB12025@elte.hu> References: <20070812163225.GA11996@elte.hu> <200708141037.48001.borntraeger@de.ibm.com> <20070820154529.GA300@elte.hu> <200708211017.02998.borntraeger@de.ibm.com> <20070821084243.GB1144@elte.hu> <1187687476.7623.8.camel@localhost> <20070821093434.GB12025@elte.hu> X-Mailer: VM 7.19 under Emacs 21.4.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1527 Lines: 32 Ingo Molnar writes: > my feeling is that it gives us generally higher-quality scheduling if we > drive all things scheduler via virtual time. Do you agree with that? On PowerPC at least, while we can measure virtual time, there is no hardware facility for getting an interrupt after a certain amount of virtual time has elapsed, but there is a facility to get an interrupt after an elapsed real-time interval. So sched_clock() could easily change to measure virtual time, but I don't see how to make scheduler_tick() be driven off virtual time. It sounds like s390 is the same. > it seems you'd like accounting to be sensitive to 'external load' - i.e. > you'd like an 'internal' top to show the 'real' CPU accounting, right? > > Wouldnt it be more consistent if a virtual box would not show any > dependency on external load? (i.e. it would slow down all of its > internal functionality transparently, without exposing it via /proc. The The tools that use the data in /proc get unhappy if user time + system time + hardirq time + softirq time + idle time + stolen time doesn't add up to real time. The way we handle that is by making stolen time represent the time taken away by the hypervisor (and on PowerPC with SMT, the time taken by the other thread too). Paul. - 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/