Message-ID: <46C0693A.1080900@bull.net>
Date: Mon, 13 Aug 2007 16:22:50 +0200
From: Laurent Vivier <Laurent.Vivier@bull.net>
Organization: Bull S.A.S.
User-Agent: Thunderbird 1.5.0.2 (X11/20060420)
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To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: kvm-devel@lists.sourceforge.net,
       linux-kernel <linux-kernel@vger.kernel.org>, cotte@de.ibm.com
Subject: Re: [kvm-devel] [PATCH 0/2][KVM] guest time accounting
References: <46BC8B39.6050202@bull.net> <200708131605.40479.borntraeger@de.ibm.com>
In-Reply-To: <200708131605.40479.borntraeger@de.ibm.com>
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Christian Borntraeger wrote:
> Am Freitag, 10. August 2007 schrieb Laurent Vivier:
>> The aim of these two patches is to measure the CPU time used by a virt=
ual
>> machine. All comments are welcome... I'm not sure it's the good way to=
 do=20
> that.
>=20
> I did something similar for or s390guest prototype, that Carsten posted=
 in=20
> May.  I decided to account guest time to the user process instead of ad=
ding a=20
> new field to avoid hazzle with old top. As you can read in the patch co=
mment,=20
> I personally prefer a new field if we can get one.
>=20
> My implementation uses a similar mechanism like hard and softirq. So I =
have an=20
> sie_enter an sie_exit and a task_is_in_sie function - like irq_enter an=
d=20
> irq_exit. The main difference is based on the fact, that s390 has preci=
se=20
> accouting for irq, steal, user and system time, and therefore my patch =
is=20
> based on architecture specifc code using CONFIG_VIRT_CPU_ACCOUNT.=20
>=20
> In general my patch has the same idea as your patch, so I am going to r=
eview=20
> your patch and see if it would fit for s390.
>=20
> For reference this is the (never posted) old patch for our virtualisati=
on=20
> prototype. It wont work with kvm but it gives you the idea what we had =
in=20
> mind on s390.
>=20

thank you for your comment.

As virtualization becomes very popular, perhaps we should implement somet=
hing
which could be used by all linux supported architectures ?
(yes, I know it's non-sense for archs like m68k...)
But my [PATCH 1/2] can be a good start (adding "guest" in cpustat)
As guest accounting is hw dependent, I think we should add a hook in the
accounting functions.

Laurent
--=20
------------- Laurent.Vivier@bull.net  --------------
          "Software is hard" - Donald Knuth


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