does ksm really work?

[sean darcy]

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?

sean

[Dan Kenigsberg]

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.

[Dor Laor]

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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>  virt(a)lists.fedoraproject.org
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[sean darcy]

On Sun, Sep 19, 2010 at 4:53 AM, Dor Laor <dlaor(a)redhat.com&gt; 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.
>
> > _______________________________________________
> > virt mailing list
> > virt(a)lists.fedoraproject.org
> > https://admin.fedoraproject.org/mailman/listinfo/virt
>
>  
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