[ovirt-users] Memory and swap issue
Doron Fediuck
dfediuck at redhat.com
Fri Jun 6 16:26:27 UTC 2014
Jeff,
I'd appreciate to get some more info on this;
First of all which ovirt version are you using?
Next, I'd appreciate if you can restore the no swap (swapoff)
and run on the host:
vdsClient -s 0 getVdsCaps
Then share the output with us.
Generally speaking swap is really bad for VMs, so we should be fine
without it. However when calculating the needed amount of memory we
reserve safety margins for various components such as vdsm itself.
We published the calculation here: http://www.ovirt.org/Sla/FreeMemoryCalculation
So feel free to add the numbers or share the data with us.
Thanks for the feedback,
Doron
----- Original Message -----
> From: "Itamar Heim" <iheim at redhat.com>
> To: "Jeff Clay" <jeffclay at gmail.com>
> Cc: users at ovirt.org, "Doron Fediuck" <dfediuck at redhat.com>
> Sent: Thursday, June 5, 2014 10:58:39 PM
> Subject: Re: [ovirt-users] Memory and swap issue
>
> On 06/05/2014 10:48 PM, Jeff Clay wrote:
> > Am I correct in understanding that vm's which aren't being actively used
> > are moved to swap space to free more available RAM? If so, that might be
> > what is causing my issue, since we usually have several VM's idle and
> > not in direct use.
>
> yes, though i don't they are supposed to be swapped if there is enough
> available memory.
>
> >
> >
> > On Thu, Jun 5, 2014 at 2:45 PM, Itamar Heim <iheim at redhat.com
> > <mailto:iheim at redhat.com>> wrote:
> >
> > On 06/05/2014 10:36 PM, Jeff Clay wrote:
> >
> > I'm concerned about disabling it and having unexpected behavior
> > if the
> > system actually does end up using all of its swap space. Any
> > insight?
> >
> >
> > change the percentage threshold then.
> > the idea is if you are swapping - its bad.
> > though, if you also have a lot of free memory, its kind of absurd to
> > block because there is a swap, but its not needed so it remains
> > swapped.
> >
> >
> >
> > On Jun 5, 2014 2:34 PM, "Itamar Heim" <iheim at redhat.com
> > <mailto:iheim at redhat.com>
> > <mailto:iheim at redhat.com <mailto:iheim at redhat.com>>> wrote:
> >
> > On 06/05/2014 10:30 PM, Jeff Clay wrote:
> >
> > 126455 MB total, 863 MB used, 125592 MB free
> > That's what I'm showing right now, but I don't have
> > as many VM's
> > running at the moment. There are currently 8 running
> > and I was
> > getting
> > that issue yesterday when I got around the 15 vm mark.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > On Thu, Jun 5, 2014 at 2:07 PM, Itamar Heim
> > <iheim at redhat.com <mailto:iheim at redhat.com>
> > <mailto:iheim at redhat.com <mailto:iheim at redhat.com>>
> > <mailto:iheim at redhat.com <mailto:iheim at redhat.com>
> > <mailto:iheim at redhat.com <mailto:iheim at redhat.com>>>> wrote:
> >
> > On 06/05/2014 02:24 AM, Jeff Clay wrote:
> >
> > I'm getting the following error trying to
> > start a VM. I
> > have 64
> > gb of
> > RAM on this host. I got this error once before
> > and
> > found that my
> > swap
> > partition was only 2gb or so. I increased the
> > swap size
> > to 124GB
> > and the
> > problem went away. Below is the error when
> > trying to
> > start a VM and
> > below that is what my output from "free -g". I
> > don't
> > see why I'm
> > getting
> > a swap file error when there's plenty of it
> > available.
> >
> >
> > * Cannot run VM. Host swap percentage is
> > above the
> > defined
> > threshold.
> >
> > - Check your configuration parameters for
> > Host
> > Swap Percentage.
> > * Cannot run VM. There is no host that
> > satisfies current
> > scheduling
> >
> > constraints. See below for details:
> > * The host USARPAOVRTHOST02 did not satisfy
> > internal
> > filter
> > Memory.
> >
> >
> >
> >
> > [root at usarpaovrthost02 ~]# free -g
> > total used free
> > shared
> > buffers
> > cached
> > Mem: 62 62 0
> > 0
> > 0
> > 12
> > -/+ buffers/cache: 50 12
> > Swap: 123 12 110
> > [root at usarpaovrthost02 ~]#
> > [root at usarpaovrthost02 ~]#
> > [root at usarpaovrthost02 ~]# swapon -s
> > Filename Type
> > Size Used
> > Priority
> > /dev/dm-1 partition
> > 129490936
> > 12811000 -1
> > [root at usarpaovrthost02 ~]#
> >
> >
> >
> >
> > _____________________________________________________
> > Users mailing list
> > Users at ovirt.org <mailto:Users at ovirt.org> <mailto:Users at ovirt.org
> > <mailto:Users at ovirt.org>> <mailto:Users at ovirt.org
> > <mailto:Users at ovirt.org>
> > <mailto:Users at ovirt.org <mailto:Users at ovirt.org>>>
> > http://lists.ovirt.org/______mailman/listinfo/users
> > <http://lists.ovirt.org/____mailman/listinfo/users>
> > <http://lists.ovirt.org/____mailman/listinfo/users
> > <http://lists.ovirt.org/__mailman/listinfo/users>>
> >
> >
> > <http://lists.ovirt.org/____mailman/listinfo/users
> > <http://lists.ovirt.org/__mailman/listinfo/users>
> > <http://lists.ovirt.org/__mailman/listinfo/users
> > <http://lists.ovirt.org/mailman/listinfo/users>>>
> >
> >
> > what do you see under host general subtab for swap
> > percentage?
> >
> >
> >
> > iirc, you can either disable the swap check via the config
> > EnableSwapCheck, or change the threshold via
> > BlockMigrationOnSwapUsagePerce____ntage
> >
> > (which would be a confusing name if it affects RunVm and
> > not only
> > migration...)
> >
> >
> >
>
>
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