From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932574AbXCOTJa (ORCPT ); Thu, 15 Mar 2007 15:09:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932801AbXCOTJP (ORCPT ); Thu, 15 Mar 2007 15:09:15 -0400 Received: from smtp-outbound-1.vmware.com ([65.113.40.141]:47970 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932750AbXCOTJF (ORCPT ); Thu, 15 Mar 2007 15:09:05 -0400 Message-ID: <45F999D4.6080602@vmware.com> Date: Thu, 15 Mar 2007 12:09:08 -0700 From: Dan Hecht User-Agent: Thunderbird 1.5.0.2 (X11/20060420) MIME-Version: 1.0 To: Jeremy Fitzhardinge Cc: dwalker@mvista.com, cpufreq@lists.linux.org.uk, Linux Kernel Mailing List , Con Kolivas , Chris Wright , Virtualization Mailing List , john stultz , Ingo Molnar , Thomas Gleixner , paulus@au.ibm.com, schwidefsky@de.ibm.com, Rik van Riel , Zachary Amsden Subject: Re: Stolen and degraded time and schedulers References: <45F6D1D0.6080905@goop.org> <1173816769.22180.14.camel@localhost> <45F70A71.9090205@goop.org> <1173821224.1416.24.camel@dwalker1> <45F71EA5.2090203@goop.org> <45F74515.7010808@vmware.com> <45F77C27.8090604@goop.org> <45F846AB.6060200@vmware.com> <45F84E39.7030507@goop.org> <45F85A62.8050001@vmware.com> <45F85BBB.70707@goop.org> <45F85F43.9030803@vmware.com> <45F866AF.9060609@goop.org> In-Reply-To: <45F866AF.9060609@goop.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 15 Mar 2007 19:09:03.0961 (UTC) FILETIME=[65A55490:01C76735] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 03/14/2007 02:18 PM, Jeremy Fitzhardinge wrote: > Dan Hecht wrote: >> On 03/14/2007 01:31 PM, Jeremy Fitzhardinge wrote: >>> Dan Hecht wrote: >>>> Sounds good. I don't see this in your patchset you sent yesterday >>>> though; did you add it after sending out those patches? >>> Yes. >>> >>>> if so, could you forward the new patch? does it explicitly prevent >>>> stolen time from getting accounted as user/system time or does it >>>> just rely on NO_HZ mode sort of happening to work that way (since the >>>> one shot timer is skipped ahead for missed ticks)? >>> Hm, not sure. It doesn't care how often it gets called; it just >>> accumulates results up to that point, but I'm not sure if the time would >>> get double accounted. Perhaps it doesn't matter when using >>> xen_sched_clock(). >>> >> I think you might be double counting time in some cases. >> sched_clock() isn't really relevant to stolen time accounting (i.e. >> cpustat->steal). >> >> I think what you want is to make sure that the sum of the cputime >> passed to all of: >> >> account_user_time >> account_system_time >> account_steal_time >> >> adds up to the total amount of time that has passed. I think it is >> sort of working for you (i.e. doesn't always double count stolen >> ticks) since in NO_HZ mode, update_process_time (which calls >> account_user_time & account_system_time) happens to be skipped during >> periods of stolen time due to the hrtimer_forward()'ing of the one >> shot expiry. > > OK, this will need a closer look. > > BTW, what are the properties of the vmi read_available_cycles()? Is > that a per-cpu timer? If its used as the timebase for sched_clock, how > does recalc_task_prio not get a -ve sleep time? > Available time is defined to be (real_time - stolen_time). i.e. time in which the vcpu is either running or not ready to run [because it is halted, and nothing is pending]). So, yes, it is per-vcpu. But, the sched_clock() samples are rebased when processes are migrated between runqueues; search sched.c for most_recent_timestamp. It's not perfect since most_recent_timestamp between cpu0 and cpu1 do not correspond to the exact same instant, but does prevent negative sleep time and is fairly close. Dan