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

Dan Kenigsberg danken at redhat.com
Tue Nov 24 14:30:41 UTC 2009

On Tue, Nov 24, 2009 at 06:43:42PM +0530, kashyap chamarthy wrote:
> On 11/24/2009 05:31 PM, Gianluca Cecchi wrote:
> >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...)?
> yes, configuratble log/trace info for ksm/ksmtuned would be useful.
> I see this for configuration stuff - /etc/ksmtuned.conf
> /kashyap

You'd have to apply the following patch to /usr/sbin/ksmtuned for it to
easily log into /var/log/ksmtuned. You'd have to add two lines to
/etc/ksmtuned.conf for this to actually work.



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