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Old 08-23-2010, 04:43 PM
"Serge E. Hallyn"
 
Default KSM Control Scripts

Quoting Nikolai K. Bochev (n.bochev@grandstarco.com):
> I've stumbled upon those on the Proxmox VE forums, and as far as i can see they're in Fedora12 by default too.
> http://gitorious.org/ksm-control-scripts
> http://download.proxmox.com/sources/
>
>
> Has anyone tested those on 10.04 KVM Host ?

Not I

> Any reason why they aren't included in Lucid ?

Well, there is some talk out there (no links handy) about KSM being
a performance hog anyway, and some people seem to turn it off.

> I'll be giving those a shot next few days, will see how it goes.

That'd be great, thanks in advance. In particular, if you get some
statistics about performance with various settings vs. # VMS vs mem
vs cpu overhead, that'd be very useful.

thanks,
-serge

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Old 08-23-2010, 07:28 PM
Dustin Kirkland
 
Default KSM Control Scripts

Serge E. Hallyn <serge.hallyn@canonical.com> wrote:
> Quoting Nikolai K. Bochev (n.bochev@grandstarco.com):
>> I've stumbled upon those on the Proxmox VE forums, and as far as i can see they're in Fedora12 by default too.
>> http://gitorious.org/ksm-control-scripts
>> http://download.proxmox.com/sources/
>>
>>
>> Has anyone tested those on 10.04 KVM Host ?
>
> Not I
>
>> Any reason why they aren't included in Lucid ?
>
> Well, there is some talk out there (no links handy) about KSM being
> a performance hog anyway, and some people seem to turn it off.
>
>> I'll be giving those a shot next few days, will see how it goes.
>
> That'd be great, thanks in advance. *In particular, if you get some
> statistics about performance with various settings vs. # VMS vs mem
> vs cpu overhead, that'd be very useful.

Further to this....

1. KSM is enabled and running by default in Ubuntu 10.04
2. The default polling scan frequency is left at the (perhaps
egregious) upstream Linux kernel default of 20ms.
3. As Serge mentions, several people have complained about that being
to frequent. Other people have complained about higher values being
not frequent enough to be useful
4. In any case, this is totally and trivially configurable in your
/etc/default/qemu-kvm file. Edit that to your heart's content and
then 'sudo restart qemu-kvm'.

Cheers,
:-Dustin

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Old 09-01-2010, 06:28 PM
"Nikolai K. Bochev"
 
Default KSM Control Scripts

Yes, i know KSM is enabled by default, i just didn't know i can configure it through /etc/default/qemu-kvm .
After running the script for around 10 days i didn't notice any huge improvement ( the vm's were already running ).
I also didn't notice any increase in CPU usage with KSM_MONITOR_INTERVAL=60 ( loadavg stays around ~1 ).
The host machine is a 2xXeon5520 with 12G ram, running 6 VM's with total of 12G ram assigned to them ( yea i know it's pushing it ).
I have a scheduled downtime in two weeks and i'll see if i can get some tweaking going then.

----- Original Message -----
> Further to this....
>
> 1. KSM is enabled and running by default in Ubuntu 10.04
> 2. The default polling scan frequency is left at the (perhaps
> egregious) upstream Linux kernel default of 20ms.
> 3. As Serge mentions, several people have complained about that being
> to frequent. Other people have complained about higher values being
> not frequent enough to be useful
> 4. In any case, this is totally and trivially configurable in your
> /etc/default/qemu-kvm file. Edit that to your heart's content and
> then 'sudo restart qemu-kvm'.
>
> Cheers,
> :-Dustin

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System Administrator




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Old 09-01-2010, 06:47 PM
Dustin Kirkland
 
Default KSM Control Scripts

After changing that variable, you have to:
sudo service qemu-kvm restart

Also, move it up by orders of 10. Go from 20 to 200 to 2000.

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