Re: [Users] Memory usage

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

> > 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