On 4/6/21 9:34 AM, Ulrich Windl wrote:
"Lentes, Bernd" <bernd.len...@helmholtz-muenchen.de> schrieb am 31.03.2021 um
15:58 in Nachricht
<537587707.120787942.1617199127012.javamail.zim...@helmholtz-muenchen.de>:
----- On Mar 30, 2021, at 7:54 PM, hunter86 bg hunter86...@yahoo.com wrote:
Keep in mind that KSM is highly cpu intensive and is most suitable for same
type
of VMs,so similar memory pages will be merged until a change happen (and
that
change is allocated elsewhere).
In oVirt migration is possible with KSM actively working, so it should work
with
pacemaker.
I doubt that KSM would be a problem... most probably performance would not
be
optimal.
Best Regards,
Strahil Nikolov
On Tue, Mar 30, 2021 at 19:47, Andrei Borzenkov
<arvidj...@gmail.com> wrote:
On 30.03.2021 18:16, Lentes, Bernd wrote:
Hi,
currently i'm reading "Mastering KVM Virtualization", published by Packt
Publishing, a book i can really recommend.
There are some proposals for tuning guests. One is KSM (kernel samepage
merging), which sounds quite interesting.
Especially in a system with lots of virtual machines with the same OS this
could
lead to significant merory saving.
I'd like to test, but i don't know if KSM maybe prevents live migration in a
pacemaker cluster.
I do not think pacemaker cares or is aware about KSM. It just tells
resource agent to perform migration; what happens is entirely up to
resource agent.
If you can migrate without pacemaker you can also migrate with pacemaker.
Just to give a feedback.
I configured KSM on both nodes. On one it saves me nearly 20GB RAM.
I checked live migration and it worked.
It' like with any sharing: If you need to "unshare", then you need extra memory. So I
wouldn't use that "extra" 20GB to run more VMs.
Yep - probably safer to use it for giving the OS some extra room to
breathe with some cache-memory ;-)
Bernd
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