[ovirt-users] Memory and swap issue

[Jeff Clay]

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.


On Thu, Jun 5, 2014 at 2:45 PM, Itamar Heim <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>> 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>>> 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...)
>>
>>
>
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