[Users] Memory usage
René Koch
rkoch at linuxland.at
Thu Feb 13 09:30:04 UTC 2014
On Thu, 2014-02-13 at 09:39 +0100, david van zeebroeck wrote:
> hello rene
> it's during testing check_rhev3 that we found this issue
> do you see a workaround for this?
At the moment I can only set the memory usage to 0 and add comments to
the documentation that vm memory usage is the usage of the vm on the
host, but not the memory usage in the vm (which I thought it was).
This issue was reported once to me, and check_rhev3 has a calculation of
the memory usage if it's negative in version 1.3, but this only solved
the issue accidentally for this specific vm of this user. As Doron
explained me in previous mail what this memory usage value really means,
I'll revert the commit from
https://github.com/ovido/check_rhev3/issues/10
and set the memory usage to 0 if negative.
I never saw this issue in my environments or on customer sides, as we
normally always monitor vms using agents in the vm and not using
check_rhev3 for vms. I use it on some test machines in my environments,
but have KSM disabled, as it consumes too much CPU load when having
databases running in vms.
Workaround is to get the memory usage from polling agents which are
running directly in the vm like check_mk, snmp, nrpe,... until I can
receive the memory usage in the vm via REST-API and add it to
check_rhev3.
Regards,
René
>
>
> On Wed, Feb 12, 2014 at 6:31 PM, René Koch <rkoch at linuxland.at> wrote:
> On Wed, 2014-02-12 at 11:22 -0500, Doron Fediuck wrote:
> >
> > ----- Original Message -----
> > > From: "René Koch" <rkoch at linuxland.at>
> > > To: "Koen Vanoppen" <vanoppen.koen at gmail.com>
> > > Cc: users at ovirt.org
> > > Sent: Wednesday, February 12, 2014 4:18:37 PM
> > > Subject: Re: [Users] Memory usage
> > >
> > > On Wed, 2014-02-12 at 15:14 +0100, Koen Vanoppen wrote:
> > > > In The GUI, it says it's using 25% of the memory.
> > >
> > >
> > > I guess it's the real value, right?
> > > The same happened for the memcached vm, someone reported
> to me -
> > > negative value in REST-API, but correct graph in oVirt
> webadmin GUI.
> > >
> > > I fear I have no idea how this can happen - so maybe
> someone else can
> > > help you troubleshoot this issue.
> > > >
> > > >
> > > >
> > > > 2014-02-12 15:10 GMT+01:00 Koen Vanoppen
> <vanoppen.koen at gmail.com>:
> > > > Thanks for the quick respons, but there is no
> memcached
> > > > running on that VM.
> > > >
> > > >
> > > > Kind regards
> > > >
> > > >
> > > >
> > > > 2014-02-12 15:06 GMT+01:00 René Koch
> <rkoch at linuxland.at>:
> > > >
> > > > On Wed, 2014-02-12 at 14:55 +0100, Koen
> Vanoppen
> > > > wrote:
> > > > > Dear all,
> > > > >
> > > > >
> > > > > When we monitor one of our machines,
> we noticed that
> > > > there was one vm
> > > > > that was constantly giving a error of
> memory usage.
> > > > But when we took a
> > > > > look at it, there is actually nothing
> wrong with it.
> > > > Now we looked
> > > > > furhter then that. We looked at the
> API of the
> > > > machine and noticed
> > > > > something very strange:
> > > > >
> > > > > <statistic
> > > > >
> > > >
> href="/api/vms/3b9aa245-75ff-42e8-b921-1c9ce61826bf/statistics/b7499508-c1c3-32f0-8174-c1783e57bb08"
> > > >
> id="b7499508-c1c3-32f0-8174-c1783e57bb08"><name>memory.used</name><description>Memory
> > > > used (agent)</description><values
> > > >
> type="INTEGER"><value><datum>-944892806</datum></value></values><type>GAUGE</type><unit>BYTES</unit>
> > > > >
> > > > >
> > > > > It's a negative...
> > > >
> > > >
> > > >
> > > > Do you have memcached running in this
> vm?
> > > >
> > > > I heard about this issue with memcached,
> but never
> > > > tested memcached in
> > > > my oVirt environment. You get the real
> usage value
> > > > with
> > > > memory.used = memory.installed +
> memory.used
> > > >
> > > >
> > > > Regards,
> > > > René
> > > >
> > > > >
> > > > >
> > > > > What could be the problem?
> > > > >
> > > > >
> > > > > Kind regards,
> > > > >
> > > > > koen
> > > > >
> > > >
> >
> > Guys,
> > these values are usually a result of overcommitment
> mechanism usage.
> > For example, if KSM is effective, it will free a lot of
> memory pages,
> > and total-free-committed becomes negative.
>
>
>
> Thanks a lot for the information.
>
>
> >
> > This was reported in
> https://bugzilla.redhat.com/show_bug.cgi?id=977758
> > and the engine is using memFree reported by vdsm, which is
> more accurate.
> >
> > The API reports the old version due to backwards
> compatibility.
>
>
>
> I just had a look at the bugzilla report and the RHEV
> documentation
> which says "Current memory in bytes used by the virtual
> machine.".
> So this means, the reported values are totally useless for
> monitoring
> memory usage of a virtual machine if KSM is active. I would
> expect to
> get the memory usage of a virtual machine and not how much
> memory is
> consumed on the hypervisor (this is pretty useless information
> for me).
>
> Is it planned to report the memory usage in a virtual machine
> in the API
> as well?
>
>
> Regards,
> René
>
>
> >
> > Doron
> >
> > P.S.
> > René- thanks for helping!
>
>
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