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<div class="moz-cite-prefix">On 3/30/21 7:54 PM, Strahil Nikolov
wrote:<br>
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<blockquote type="cite"
cite="mid:1731516382.1153225.1617126879058@mail.yahoo.com">
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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).
<div id="yMail_cursorElementTracker_1617126697789"><br>
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<div id="yMail_cursorElementTracker_1617126697942">In oVirt
migration is possible with KSM actively working, so it should
work with pacemaker.<br>
<br>
<br>
I doubt that KSM would be a problem... most probably performance
would not be optimal.</div>
<div id="yMail_cursorElementTracker_1617126815211"><br>
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<div id="yMail_cursorElementTracker_1617126815392">Best Regards,</div>
<div id="yMail_cursorElementTracker_1617126819228">Strahil Nikolov<br>
<blockquote style="margin: 0 0 20px 0;">
<div style="font-family:Roboto, sans-serif; color:#6D00F6;">
<div>On Tue, Mar 30, 2021 at 19:47, Andrei Borzenkov</div>
<div><a class="moz-txt-link-rfc2396E" href="mailto:arvidjaar@gmail.com"><arvidjaar@gmail.com></a> wrote:</div>
</div>
<div style="padding: 10px 0 0 20px; margin: 10px 0 0 0;
border-left: 1px solid #6D00F6;"> On 30.03.2021 18:16,
Lentes, Bernd wrote:<br clear="none">
> Hi,<br clear="none">
> <br clear="none">
> currently i'm reading "Mastering KVM Virtualization",
published by Packt Publishing, a book i can really
recommend.<br clear="none">
> There are some proposals for tuning guests. One is KSM
(kernel samepage merging), which sounds quite interesting.<br
clear="none">
> Especially in a system with lots of virtual machines
with the same OS this could lead to significant merory
saving.<br clear="none">
> I'd like to test, but i don't know if KSM maybe
prevents live migration in a pacemaker cluster.<br
clear="none">
<br clear="none">
I do not think pacemaker cares or is aware about KSM. It
just tells<br clear="none">
resource agent to perform migration; what happens is
entirely up to<br clear="none">
resource agent.<br clear="none">
<br clear="none">
If you can migrate without pacemaker you can also migrate
with pacemaker.</div>
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<font face="monospace">Apart from the cpu consumption another point
to be<br>
careful about with migration could be that when you<br>
start up machines they will increase memory consumption<br>
as they start up services and at the same time ksm-daemon<br>
will scan them and merge the pages keeping memory<br>
consumption under control - possibly without big spikes.<br>
When you move a lot of VMs to a node I'd expect a spike<br>
</font><font face="monospace">in memory consumption till ksm-daemon
is able to do</font><br>
<font face="monospace">the merging. Of course that will depend on
network</font><br>
<font face="monospace">throughput competing with ksm-daemon. No idea
if any</font><br>
<font face="monospace">special hinting for ksm is being done on a
migration.</font><br>
<br>
<font face="monospace">Klaus</font><br>
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