linux-kernel - Re: [PATCH RFC V2 0/5] Separate consigned (expected steal) from steal time.

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Date:	Wed, 17 Oct 2012 21:14:37 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Michael Wolf <mjw@...ux.vnet.ibm.com>
CC:	<linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
	<peterz@...radead.org>, <mtosatti@...hat.com>, <mingo@...hat.com>,
	<avi@...hat.com>, <anthony@...emonkey.ws>
Subject: Re: [PATCH RFC V2 0/5] Separate consigned (expected steal) from steal
 time.

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.

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