On Tue, Nov 24, 2009 at 11:53:46AM +0100, Gianluca Cecchi wrote:
Hello,
F12 x86_64 with Qemu/KVM booted yesterday evening.
It has two guests with CentOS 5.3 x86_64 configured to auto-start and
now they are running...
I see this morning, some minutes ago:
[root@virtfed ~]# service ksm status
ksm is not running
My config:
[root@virtfed ~]# chkconfig --list|grep ksm
ksm 0:off 1:off 2:on 3:on 4:on 5:on 6:off
ksmtuned 0:off 1:off 2:on 3:on 4:on 5:on 6:off
[root@virtfed ~]# cat /sys/kernel/mm/ksm/pages_shared
3786
Then I start two other guests, both with CentOS 5.4 x86_64.
After a while:
[root@virtfed ~]# cat /sys/kernel/mm/ksm/pages_shared
4752
[root@virtfed ~]# cat /sys/kernel/mm/ksm/pages_shared
5219
...
[root@virtfed ~]# cat /sys/kernel/mm/ksm/pages_shared
90895
and now, without any action at my side:
[root@virtfed ~]# service ksm status
ksm is running
Is this normal/expected?
Any deeper doc/link about ksm/ksmtuned logic?
Is it ksmtuned that spins ksm as it is needed? Any log file to check/configure?
I read
https://fedoraproject.org/wiki/Features/KSM but probably I'm
missing something...
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.
Thanks,
Gianluca
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