[Openstack] Openstack+KVM+overcommit, VM priority

Kostyantyn Volenbovskyi volenbovsky at yandex.ru
Thu Jan 12 17:10:14 UTC 2017


I have provided the answer to that on https://ask.openstack.org/en/question/101374 where you asked this question as well.
That elaborates slightly on 'There are facilities to allow one VM or another to have CPU priority’ which James mentioned below.
For RAM such things as Memory Tuning https://libvirt.org/formatdomain.html#elementsMemoryTuning is not supported
as well as memory ballooning (which might be part of answer I think) are not supported in Nova.
And well, ‘don’t overcommit RAM’ is often a good principle to stick to.

> On Jan 12, 2017, at 1:33 PM, Ivan Derbenev <ivan.derbenev at tech-corps.com> wrote:
> What are the facilities for cpu? That's the initial question - how can I do it if this is possible
> Best Regards
> Tech-corps IT Engineer
> Ivan Derbenev
> Phone: +79633431774
> -----Original Message-----
> From: James Downs [mailto:egon at egon.cc] 
> Sent: Thursday, January 12, 2017 12:56 AM
> To: Ivan Derbenev <ivan.derbenev at tech-corps.com>
> Cc: openstack at lists.openstack.org
> Subject: Re: [Openstack] Openstack+KVM+overcommit, VM priority
> On Wed, Jan 11, 2017 at 09:34:32PM +0000, Ivan Derbenev wrote:
>> if both vms start using all 64gb memory, both of them start using swap
> Don't overcommit RAM.
>> So, the question is - is it possible to prioritize 1st vm above 2nd? so the second one will fail before the 1st, to leave maximum possible perfomance to the most importan one?
> Do you mean CPU prioritization? There are facilities to allow one VM or another to have CPU priority, but what, if a high priority VM wants RAM, you want to OOM the other? That doesn't exist, AFAIK.
> Cheers,
> -j
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