From: Michael Wolf <mjw@linux.vnet.ibm.com>
To: Glauber Costa <glommer@parallels.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
peterz@infradead.org, mtosatti@redhat.com, mingo@redhat.com,
avi@redhat.com, anthony@codemonkey.ws
Subject: Re: [PATCH RFC V2 0/5] Separate consigned (expected steal) from steal time.
Date: Wed, 17 Oct 2012 10:13:57 -0500 [thread overview]
Message-ID: <1350486837.6414.3.camel@lambeau> (raw)
In-Reply-To: <507EE77D.6010906@parallels.com>
On Wed, 2012-10-17 at 21:14 +0400, Glauber Costa wrote:
> On 10/17/2012 06:23 AM, Michael Wolf wrote:
> > In the case of where you have a system that is running in a
> > capped or overcommitted environment the user may see steal time
> > being reported in accounting tools such as top or vmstat. This can
> > cause confusion for the end user. To ease the confusion this patch set
> > adds the idea of consigned (expected steal) time. The host will separate
> > the consigned time from the steal time. The consignment limit passed to the
> > host will be the amount of steal time expected within a fixed period of
> > time. Any other steal time accruing during that period will show as the
> > traditional steal time.
> >
> > TODO:
> > * Change native_clock to take params and not return a value
> > * Change update_rq_clock_task
> >
> > Changes from V1:
> > * Removed the steal time allowed percentage from the guest
> > * Moved the separation of consigned (expected steal) and steal time to the
> > host.
> > * No longer include a sysctl interface.
> >
>
> You are showing this in the guest somewhere, but tools like top will
> still not show it. So for quite a while, it achieves nothing.
>
> Of course this is a barrier that any new statistic has to go through. So
> while annoying, this is per-se ultimately not a blocker.
>
> What I still fail to see, is how this is useful information to be shown
> in the guest. Honestly, if I'm in a guest VM or container, any time
> during which I am not running is time I lost. It doesn't matter if this
> was expected or not. This still seems to me as a host-side problem, to
> be solved entirely by tooling.
>
What tools like top and vmstat will show is altered. When I put time in
the consign bucket it does not show up in steal. So now as long as the
system is performing as expected the user will see 100% and 0% steal. I
added the consign field to /proc/stat so that all time accrued in the
period is accounted for and also for debugging purposes. The user wont
care about consign and will not see it.
next prev parent reply other threads:[~2012-10-17 15:14 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-17 2:23 [PATCH RFC V2 0/5] Separate consigned (expected steal) from steal time Michael Wolf
2012-10-17 2:24 ` [PATCH RFC V2 1/5] Alter the amount of steal time reported by the guest Michael Wolf
2012-10-17 2:24 ` [PATCH RFC V2 2/5] Expand the steal time msr to also contain the consigned time Michael Wolf
2012-10-17 2:24 ` [PATCH RFC V2 3/5] Add the code to send the consigned time from the host to the guest Michael Wolf
2012-10-17 2:24 ` [PATCH RFC V2 4/5] Add a timer to allow the separation of consigned from steal time Michael Wolf
2012-10-17 2:24 ` [PATCH RFC V2 5/5] Add an ioctl to communicate the consign limit to the host Michael Wolf
2012-10-17 17:14 ` [PATCH RFC V2 0/5] Separate consigned (expected steal) from steal time Glauber Costa
2012-10-17 15:13 ` Michael Wolf [this message]
2012-10-22 15:33 ` Rik van Riel
2012-11-26 20:00 ` Michael Wolf
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