KSM

[dignus]

Hi all,

On my currently 7 node cluster I see on all nodes that KSM sharing is 0. Is there a setting I have to make to enable KSM sharing? 90% of my VM's are the same OS, on the old platform (oVirt) we did see KSM sharing active.

 

[tom]

KSM starts only if you use more than 50 % of your physical ram, so the questions are:

1. how much physical RAM do you have on your host?
2. how much RAM usage do you see on your host?

 

[dignus]

Ah, that part was unknown to me. However.. I have a 192 GB host, 53% RAM in use. KSM is not used. I'll put some more VM's on it to see what it does.

 

[LnxBil]

It's also important that only KVM/QEMU VMs are considered for KSM. Please correct me if i'm wrong, but as far as I know, KSM does not work for LXC/containers due to security considerations. Every test I run shows this (unfortunate) behavior.

 

[spirit]

KSM starts only if you use more than 50 % of your physical ram, so the

it's when you use more than 80%

KSM_THRES_COEF=20