KSM Control Scripts

Dustin Kirkland kirkland at canonical.com
Mon Aug 23 19:28:57 UTC 2010

Serge E. Hallyn <serge.hallyn at canonical.com> wrote:
> Quoting Nikolai K. Bochev (n.bochev at 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'.


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