From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752789Ab1LQVri (ORCPT ); Sat, 17 Dec 2011 16:47:38 -0500 Received: from rcsinet15.oracle.com ([148.87.113.117]:19350 "EHLO rcsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752042Ab1LQVrf (ORCPT ); Sat, 17 Dec 2011 16:47:35 -0500 Date: Sat, 17 Dec 2011 16:46:26 -0500 From: Konrad Rzeszutek Wilk To: Ferenc Wagner Cc: Jeremy Fitzhardinge , Zhenzhong Duan , linux-x86_64@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com Subject: Re: [PATCH] cpu idle ticks show twice in xen pvm guest Message-ID: <20111217214626.GA17841@phenom.dumpdata.com> References: <20111010155319.GA29140@phenom.oracle.com> <4E934EC9.5030909@goop.org> <87vcppbvc4.fsf@tac.ki.iif.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87vcppbvc4.fsf@tac.ki.iif.hu> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet22.oracle.com [141.146.126.238] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090204.4EED0DF0.0086,ss=1,re=0.000,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 09, 2011 at 04:47:39PM +0100, Ferenc Wagner wrote: > Jeremy Fitzhardinge writes: > > >> On Wed, Oct 05, 2011 at 10:11:58PM -0700, Zhenzhong Duan wrote: > >> > >>> Run below test on xen pvm. > >>> # x=$(cat /proc/stat | grep cpu0 | awk '{print $5}') && sleep 60 \ > >>> && y=$(cat /proc/stat | grep cpu0 | awk '{print $5}') \ > >>> && echo -e "X:$x\nY:$y\nIDLE:" $(echo "scale=3; ($y-$x)/6000*100" | bc) > >>> > >>> @ X:58562301 > >>> @ Y:58574282 > >>> @ IDLE: 199.600 > >>> > >>> Normal idle percent should be around 100%. > >>> xen_timer_interrupt called account_idle_ticks to account hypervisor stolen idle ticks > >>> but these ticks will be accounted again when idle ticks restarted. > >>> > >>> Signed-off-by: Zhenzhong Duan > >>> Signed-off-by: Joe Jin > > > > Does this affect the accounting of stolen ticks? If it does, that's not > > necessarily a showstopper for this patch, but we'll need to do some more > > thinking about it. Certainly, accurate accounting for idleness is > > important. > > Please see also http://thread.gmane.org/gmane.linux.kernel/734441, where > I found that the counter doubling isn't always present under 2.6.26. > However, after going to 2.6.32 (Debian lenny-backports kernel, 4th of > April on the graph below) that instability seems to disappear. Please > note that the following graph shows halved idle and iowait percentages. > What happenend in Feb? > > (I haven't collected steal values, so the numbers don't sum up to 100%.) > I'd be grateful if this discrepancy could be cleared up eventually! > It's heartening to see some progress after more than three years. :) > > Actually, as Munin doesn't half the idle and iowait values, but > truncates the (then overflowing) graph at 100%, I was rather surprised > to see iowait completely disappear after the kernel upgrade, and > concluded that it was somehow converted into buggy-looping in blkfront. > Now I see this isn't the case, but the steadily increasing system CPU > usage between reboots is still a mystery. I'll start a separate thread > for that, just wanted to provide some motivation for this topic. Did you add more memory in the system? > -- > Thanks, > Feri.