Enable KSM (Kernel Same-Page Merging) on boot in Debian

debian_ksm.md

Enable KSM (Kernel Same-Page Merging) on boot in Debian

I have installed and run Netdata on my Debian based home server and I wanted to enable KSM after Netdata installer suggested it could save some RAM.

To enable the KSM on boot in Debian you I executed these steps:

1. Install ksmtuned without all the QEMU dependencies:

sudo apt-get install ksmtuned --no-install-recommends

2. I actually don't need the ksmtuned.service and I did disabled it:

sudo systemctl stop ksmtuned.service
sudo systemctl disable ksmtuned.service

3. Finally if:

sudo cat /sys/kernel/mm/ksm/run

returns 0 restart the ksm.service:

sudo systemctl restart ksm.service

The service that does the work is ksm.service and it should be enabled by default.
If it isn't you can do enable it by running: sudo systemctl enable --now ksm.service.

Thanks. I don't have that service for some reason, despite following your steps and everything appeared to proceed without an issue (though I am running Arch, not Debian). I found that not having the ksm service is not a problem. In case anyone else runs into this and wants a different solution: you can use systemd's temporary files system to enable ksm at boot time (you will need to reboot or echo 1 > /sys/kernel/mm/ksm/run to enable it, though).

Create /etc/tmpfiles.d/ksm.conf with the contents:

w /sys/kernel/mm/ksm/run - - - - 1

Also, you can verify KSM is working by checking /sys/kernel/mm/ksm/pages_shared. If the output of that is a non-zero number, you are good to go.

Thanks I just learned about tmpfiles.d.
A network engineer managed to patch the kernel with UKSM. It seems like piece of code which performs better than KSM.

Thanks. I don't have that service for some reason, despite following your steps and everything appeared to proceed without an issue (though I am running Arch, not Debian). I found that not having the ksm service is not a problem. In case anyone else runs into this and wants a different solution: you can use systemd's temporary files system to enable ksm at boot time (you will need to reboot or echo 1 > /sys/kernel/mm/ksm/run to enable it, though).

Create /etc/tmpfiles.d/ksm.conf with the contents:

w /sys/kernel/mm/ksm/run - - - - 1

Also, you can verify KSM is working by checking /sys/kernel/mm/ksm/pages_shared. If the output of that is a non-zero number, you are good to go.

My output is zero, but i've enabled it. What could be wrong?

Has it been enabled in the kernel that you are running?