From: Srivatsa Vaddagiri <vatsa@in.ibm.com>
To: Boris Dolgov <boris@dolgov.name>
Cc: kvm@vger.kernel.org, bharata@in.ibm.com,
Balbir Singh <balbir@in.ibm.com>
Subject: Re: Fwd: KVM and cpu limiting
Date: Tue, 6 Jul 2010 10:09:45 +0530 [thread overview]
Message-ID: <20100706043945.GD15598@linux.vnet.ibm.com> (raw)
In-Reply-To: <AANLkTikrTOZpuiCXiOlPvhJJg8AgVp4IkUrFoimjLZF1@mail.gmail.com>
On Fri, Jul 02, 2010 at 08:38:37PM +0400, Boris Dolgov wrote:
> On Fri, Jul 2, 2010 at 11:57 AM, Srivatsa Vaddagiri <vatsa@in.ibm.com> wrote:
> >> Is it possible to limit cpu usage be VM when using qemu+kvm?
> >
> > Have you checked cpu controller?
> It is very interesting. Looks like it is something, that I need.
> So, limiting qemu process will limit cpu usage for the container?
> I think, i will be able to configure it to provide guaranted cpu to
> containers in that way.
Note that shares control how much cpu bandwidth a VM gets _relative_ to other
active VMs and hence is not a absolute measure of how much CPU capacity is
provided to a particular VM. If the number of VMs deployed on a server
and their relative priority remains static in general, then shares can be
used as both "guarantee" and "limit" mechanism.
> But what happens with the VM when qemu process is paused by the
> scheduler? Will this time be counted as idle time for VM's cpu,
No - it should be accounted as "runqueue wait time".
> or it will be added to the state, which was used when qemu process was
> paused?
The runqueue wait time should reflect as "steal" time for the VMs. top command
should show the steal time for a VM (look for 'st'), although I am not 100% sure
whether steal time is reported in case of KVM guests.
> > Why do you want to modify /proc/cpuinfo of VMs?
> Just for information about the limits for the VMs' owners.
Sounds like a cool idea - although not sure whether cpuinfo is the right place.
You can try sending a patch and find out what the community thinks of it!
- vatsa
next prev parent reply other threads:[~2010-07-06 4:40 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-02 6:23 KVM and cpu limiting Boris Dolgov
[not found] ` <AANLkTinbGi6LOu01xySOiqfml-VFG5TYt7ovXVn7hVlR@mail.gmail.com>
2010-07-02 7:57 ` Fwd: " Srivatsa Vaddagiri
2010-07-02 16:38 ` Boris Dolgov
2010-07-06 4:39 ` Srivatsa Vaddagiri [this message]
2010-07-02 8:02 ` RW
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