Hello michal,
Thanks for your answers.
If others have same questions, I did found this information below on oVirt web
site
(http://www.ovirt.org/develop/release-management/features/engine/maximum-memory-size/)
Note on size of maximum memory
If memory hot-plug is not required, max memory can be set to be the same as VM
memory. Suggested value is 4x size of VM memory. Larger max memory is
discouraged because:
* I can make QEMU process to start for longer time.
* If hot plugged memory is also required to be hot unpluggable, it needs to
be considered as movable by the guest kernel. Kernel requires the amount of
movable memory to be at most 4x larger that non-movable memory for stable run.
* On PowerPC platform continuous block of non-movable memory of size 1/64
of the max memory needs to be allocated for each VM.
cordialement, regards,
Nelson LAMEIRAS
Ingénieur Systèmes et Réseaux / Systems and Networks engineer
Tel: +33 5 32 09 09 70
nelson.lamei...@lyra-network.com
www.lyra-network.com | www.payzen.eu
Lyra Network, 109 rue de l'innovation, 31670 Labège, FRANCE
From: "Michal Skrivanek" <michal.skriva...@redhat.com>
To: "Nelson Lameiras" <nelson.lamei...@lyra-network.com>
Cc: "ovirt users" <users@ovirt.org>
Sent: Tuesday, April 18, 2017 11:55:46 AM
Subject: Re: [ovirt-users] vm "maximum memory" setting questions
On 18 Apr 2017, at 11:46, Nelson Lameiras < nelson.lamei...@lyra-network.com >
wrote:
Hello,
A new vm setting "maximum memory" has appeared in oVirt >4 which by default has
the value "current memory”*4
In 4.1
BQ_BEGIN
- Why is "maximum memory" setting necessary to set?
BQ_END
BQ_BEGIN
- Why isn't this value set to "infinity" by default ?
BQ_END
Because it’s recommended to be about 4x the startup size by linux kernel
BQ_BEGIN
It seems to me kind of uselessly counter productif to have to decide a maximum
memory amount beforehand. if we do this, will we have to set maximum CPU cores
also in the future (being devil's advocate here ;) )
BQ_END
You don’t have to decide, you can keep the default 4x.
For CPUs it is not currently needed and is set according to engine-config
maximum supported by qemu-kvm - 288 in 4.1
Thanks,
michal
.
BQ_BEGIN
I did searched oVirt documentation, but very little information is available.
Maybe this is an libvirt question, but I'm hopping a oVirt guru could quickly
enlighten me.
cordialement, regards,
<element-signature_logo_lyra_115x94.jpg>
Nelson LAMEIRAS
Ingénieur Systèmes et Réseaux / Systems and Networks engineer
Tel: +33 5 32 09 09 70
nelson.lamei...@lyra-network.com
www.lyra-network.com | www.payzen.eu
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Lyra Network, 109 rue de l'innovation, 31670 Labège, FRANCE
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BQ_END
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