[fedora-virt] F12 and ksm/ksmtuned: info required...

[Gianluca Cecchi]

On Tue, Nov 24, 2009 at 12:50 PM, Dan Kenigsberg <danken at redhat.com> wrote:
>
> yes, the purpose of ksmtuned is to tune ksm parameters, or stop it
> altogether if it is not needed. In case your two virtual machines
> required less than available memeory, ksm is not used. If ksmtune senses
> that memory stress has risen, it fires up ksm again.
>
> I don't think this is written anywhere but in the code.. We probably
> should add something to the "User experience" section to that feature page.
> How about:
>
> Fedora's kvm comes with 2 services controlling the behavior of ksm. One,
> simply called ksm, is just a nice means to start and stop ksm's kernel
> thread. The other, called ksmtuned, controls the first service and tunes
> its parameters according to the memory stress that is generated by KVM
> virtual machines.
>

It sounds good; I would only add something like this:

"In case of need, e.g. in minor load situations, ksmtuned can also
stop ksm service at all.
Later, if ksmtuned senses that memory stress has risen, it will fire
up ksm again."

So that one knows that to monitor the status of ksm is not a good idea
in general.....
Any log configurable to see/trace ksmtuned decisions (start ksm, stop
ksm, increase pages...)?

Gianluca