From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: Stolen and degraded time and schedulers Date: Wed, 14 Mar 2007 14:18:39 -0700 Message-ID: <45F866AF.9060609@goop.org> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <45F85F43.9030803@vmware.com> Sender: linux-kernel-owner@vger.kernel.org To: Dan Hecht 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 List-Id: virtualization@lists.linuxfoundation.org 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? J