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Date: Fri, 14 Feb 2014 19:15:17 +0100
From: Stefan Priebe <s.priebe@profihost.ag>
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Subject: Re: [Qemu-devel] memory allocation of migration changed?
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Orit Wasserman <owasserm@redhat.com>, Peter Lieven <pl@kamp.de>, qemu-devel <qemu-devel@nongnu.org>, Dave Gilbert <dgilbert@redhat.com>, Juan Quintela <quintela@redhat.com>

Am 14.02.2014 15:59, schrieb Stefan Hajnoczi:
> On Tue, Feb 11, 2014 at 07:32:46PM +0100, Stefan Priebe wrote:
>> Am 11.02.2014 17:22, schrieb Peter Lieven:
>>>
>>>
>>>> Am 11.02.2014 um 16:44 schrieb Stefan Hajnoczi <stefanha@gmail.com>:
>>>>
>>>> On Tue, Feb 11, 2014 at 3:54 PM, Stefan Priebe - Profihost AG
>>>> <s.priebe@profihost.ag> wrote:
>>>>> in the past (Qemu 1.5) a migration failed if there was not enogh memory
>>>>> on the target host available directly at the beginning.
>>>>>
>>>>> Now with Qemu 1.7 i've seen succeeded migrations but the kernel OOM
>>>>> memory killer killing qemu processes. So the migration seems to takes
>>>>> place without having anough memory on the target machine?
>>>>
>>>> How much memory is the guest configured with?  How much memory does
>>>> the host have?
>>>>
>>>> I wonder if there are zero pages that can be migrated almost "for
>>>> free" and the destination host doesn't touch.  When they are touched
>>>> for the first time after migration handover, they need to be allocated
>>>> on the destination host.  This can lead to OOM if you overcommitted
>>>> memory.
>>>>
>>>> Can you reproduce the OOM reliably?  It should be possible to debug it
>>>> and figure out whether it's just bad luck or a true regression.
>>>>
>>>> Stefan
>>>
>>> Kernel Version would also be interesting as well as thp and ksm settings.
>>
>> Kernel Host: 3.10.26
>>
>> What's thp / ksm? how to get those settings?
>
> Transparent Huge Pages
>
> # cat /sys/kernel/mm/transparent_hugepage/enabled
>
> Kernel Samepage Merging
>
> # cat /sys/kernel/mm/ksm/run


# cat /sys/kernel/mm/transparent_hugepage/enabled
[always] madvise never


# cat /sys/kernel/mm/ksm/run
1


>
> Stefan
>