linux-kernel - Re: [Xen-devel] [PATCH] xen: add steal

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Message-ID: <1463587813.5851.35.camel@citrix.com>
Date:	Wed, 18 May 2016 18:10:13 +0200
From:	Dario Faggioli <dario.faggioli@...rix.com>
To:	Juergen Gross <jgross@...e.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	<xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>
CC:	<sstabellini@...nel.org>, <david.vrabel@...rix.com>,
	Tony S <suokunstar@...il.com>
Subject: Re: [Xen-devel] [PATCH] xen: add steal_clock support on x86

On Wed, 2016-05-18 at 16:53 +0200, Juergen Gross wrote:
> On 18/05/16 16:46, Boris Ostrovsky wrote:
> > 
> > Won't we be accounting for stolen cycles twice now --- once from
> > steal_account_process_tick()->steal_clock() and second time from
> > do_stolen_accounting()?
> Uuh, yes.
> 
> I guess I should rip do_stolen_accounting() out, too? It is a
> Xen-specific hack, so I guess nobody will cry. Maybe it would be a
> good idea to select CONFIG_PARAVIRT_TIME_ACCOUNTING for XEN then?
> 
So, config options aside, if I understand this correctly, it looks like
we were actually already doing steal time accounting, although in a
non-standard way.

And yet, people seem to have issues relating to lack of (proper?) steal
time accounting (Cc-ing Tony).

I guess this means that, either:
 - the issue being reported is actually not caused by the lack of 
   steal time accounting,
 - our current (Xen specific) steal time accounting solution is flawed,
 - the issue is caused by the lack of the bit of steal time accounting
   that we do not support yet,
 - other ideas? Tony?

Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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