Re: Stolen and degraded time and schedulers

From: Dan Hecht <dhecht@vmware.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: dwalker@mvista.com, cpufreq@lists.linux.org.uk,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Con Kolivas <kernel@kolivas.org>,
	Chris Wright <chrisw@sous-sol.org>,
	Virtualization Mailing List <virtualization@lists.osdl.org>,
	john stultz <johnstul@us.ibm.com>, Ingo Molnar <mingo@elte.hu>,
	Thomas Gleixner <tglx@linutronix.de>,
	paulus@au.ibm.com, schwidefsky@de.ibm.com,
	Rik van Riel <riel@redhat.com>
Subject: Re: Stolen and degraded time and schedulers
Date: Wed, 14 Mar 2007 13:26:10 -0700	[thread overview]
Message-ID: <45F85A62.8050001@vmware.com> (raw)
In-Reply-To: <45F84E39.7030507@goop.org>

>>> How is cpustat->steal used?  How does it get out to usermode?
>>>
>> Via /proc/stat, used by modern 'top', maybe other utilities.  It is
>> useful to users who want to see where the time is really going from
>> inside a guest when running on a (para)virtual machine.
>>
>> I believe previous set of xen paravirt-ops patches already handled
>> cases #2 and #3 (but no longer do since switching to clockevents), and
>> the old vmitime code did also.  Obviously, we need revamp this stuff
>> to make it fit in with the new clockevents/hrtimer way of doing things.
> 
> I added stolen time accounting to xen-pv_ops last night.  For Xen, at
> least, it wasn't hard to fit into the clockevent infrastructure.  I just
> update the stolen time accounting for each cpu when it gets a timer
> tick; they seem to get a tick every couple of seconds even when idle.
> 

Sounds good.  I don't see this in your patchset you sent yesterday 
though; did you add it after sending out those patches?  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)?

thanks,
Dan