On Thu, 2014-02-13 at 03:49 -0500, Doron Fediuck wrote:

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From: "René Koch" <rkoch@linuxland.at> To: "Doron Fediuck" <dfediuck@redhat.com> Cc: "Koen Vanoppen" <vanoppen.koen@gmail.com>, users@ovirt.org, "Martin Sivak" <msivak@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:

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From: "René Koch" <rkoch@linuxland.at> To: "Koen Vanoppen" <vanoppen.koen@gmail.com> Cc: users@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:

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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.

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2014-02-12 15:10 GMT+01:00 Koen Vanoppen <vanoppen.koen@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@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.

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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.

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 and keep reporting! Doron