Re: [Qemu-devel] memory allocation of migration changed?

[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.

Peter