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



On 11/24/2009 08:00 PM, Dan Kenigsberg wrote:
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 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.

thanks a lot. will try it.

/kashyap


Regards,

Dan.



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