[ovirt-users] Memory and swap issue

[Itamar Heim]

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 ~]#
>
>
>
>
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>
>                       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...)
>
>
>