linux-kernel - Re: [kvm-devel] [PATCH 0/4] Virtual Machine Time Accounting

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Message-ID: <46CAE096.4060606@qumranet.com>
Date:	Tue, 21 Aug 2007 15:54:46 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Laurent Vivier <Laurent.Vivier@...l.net>,
	kvm-devel <kvm-devel@...ts.sourceforge.net>,
	John Stoffel <john@...ffel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [kvm-devel] [PATCH 0/4] Virtual Machine Time Accounting

Jeremy Fitzhardinge wrote:
> Laurent Vivier wrote:
>   
>> functionnalities:
>>
>> - allow to measure time spent by a CPU in a virtual CPU.
>> - allow to display in /proc/state this value by CPU
>> - allow to display in /proc/<pid>/state this value by process
>> - allow KVM to use these 3 previous functionnalities
>>   
>>     
>
> So, currently time spent in a kvm guest is accumulated as qemu-kvm
> usertime, right?  Given that qemu knows when its running in qemu vs
> guest context, couldn't it provide the breakdown between user and guest
> time (ditto lguest)?
>   

qemu doesn't (and shouldn't) do accounting; that's best done by 
interrupt driven code.

The patches do account for guest time in a separate counter; guest time 
is added to both user time and the new counter.  This allows an old 
'top' to see guest time (accounted as user time), and a new 'top' to 
separate guest time and user time by performing the appropriate 
mathematical operation.


-- 
error compiling committee.c: too many arguments to function

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