[Users] Memory usage
Doron Fediuck
dfediuck at redhat.com
Thu Feb 13 09:51:08 UTC 2014
----- Original Message -----
> From: "René Koch" <rkoch at linuxland.at>
> To: "Doron Fediuck" <dfediuck at redhat.com>
> Cc: "Koen Vanoppen" <vanoppen.koen at gmail.com>, users at ovirt.org, "Martin Sivak" <msivak at redhat.com>
> Sent: Thursday, February 13, 2014 11:16:27 AM
> Subject: Re: [Users] Memory usage
>
> On Thu, 2014-02-13 at 03:49 -0500, Doron Fediuck wrote:
> >
> > ----- Original Message -----
> > > From: "René Koch" <rkoch at linuxland.at>
> > > To: "Doron Fediuck" <dfediuck at redhat.com>
> > > Cc: "Koen Vanoppen" <vanoppen.koen at gmail.com>, users at ovirt.org, "Martin
> > > Sivak" <msivak at redhat.com>
> > > Sent: Wednesday, February 12, 2014 7:31:47 PM
> > > Subject: Re: [Users] Memory usage
> > >
> > > 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
> > >
> > >
> >
> > René,
> > started digging into this, but it may take some time.
> >
> > Note that there are 2 memory usage reports; one for the host,
> > and another for each VM.
> > My response is related to the host, while the original question was
> > for the VM. I still think the root cause is the same (ie- related to
> > overcommitment; for example the VM may have a balloon inflated), but
> > would like to properly check and fix if needed.
>
>
> Yes, I know. So my question was if we can add another value for the
> usage in the vm in addition to the usage of the vm on the host.
>
We'll know once we understand the cause- ie is it a bug needs fixing or
should we indeed add another value
If you have a setup with this issue, try removing the balloon device
and see if it helps / changes.
>
> >
> > In order to make sure we keep track of it, please open a bug with all the
> > relevant info.
> >
>
> I'll open a bug for this.
>
Thanks
>
> > Thanks and keep reporting!
> > Doron
>
>
>
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