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Re: [Qemu-devel] memory allocation of migration changed?
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] memory allocation of migration changed? |
Date: |
Fri, 14 Feb 2014 15:59:00 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
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 <address@hidden>:
> >>
> >>On Tue, Feb 11, 2014 at 3:54 PM, Stefan Priebe - Profihost AG
> >><address@hidden> 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
Stefan