[fedora-virt] does ksm really work?

[sean darcy]

On Sun, Sep 19, 2010 at 4:53 AM, Dor Laor <dlaor at redhat.com> wrote:
> On 09/19/2010 10:17 AM, Dan Kenigsberg wrote:
>>
>> On Sat, Sep 18, 2010 at 10:58:39PM -0400, sean darcy wrote:
>>>
>>> I'm running kvm on F14. I'm running 2 XP clones. The ksm and ksmtuned
>>> demons are running.
>>>
>>> Yet:
>>>
>>>  for ii in /sys/kernel/mm/ksm/* ; do echo -n "$ii: " ; cat $ii ; done
>>> /sys/kernel/mm/ksm/full_scans: 0
>>> /sys/kernel/mm/ksm/pages_shared: 0
>>> /sys/kernel/mm/ksm/pages_sharing: 0
>>> /sys/kernel/mm/ksm/pages_to_scan: 100
>>> /sys/kernel/mm/ksm/pages_unshared: 0
>>> /sys/kernel/mm/ksm/pages_volatile: 266200
>>> /sys/kernel/mm/ksm/run: 0
>>> /sys/kernel/mm/ksm/sleep_millisecs: 20
>>>
>>> And yes, I've echo'd 1 to sys/kernel/mm/ksm/run, but it gets reset to
>>> 0 after about a minute (ksmtuned at work?).
>>>
>>> When does ksm do its stuff? This is a pretty big machine (16G). Does
>>> it wait until there's memory pressure?
>>
>> Yes, ksmtuned does exactly that. If you prefer to control ksm/run
>> yourself, you can shut this service down.
>
> If you have sufficient memory on the host, ksm won't scan until the free ram
> pages will cross some water mark.
> Check /etc/ksmtuned.conf and watch the log file if debug is enabled.
>
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>
>

OK. Thanks for the prompt replies.

I'll be installing this server next week using 8 or more XP clones.
That'll be a better test.

sean