When playing a online match the game fps would drop to 40 when everywhere else it was fine. Had to run sudo sysctl kernel.split_lock_mitigate=0 and it fixed the problem. Doing it the terminal only changes it for that session so you'll have to search up for your specific distro on how to change it permanently. You could also try what I did below.

sudo vim into ~/etc/sysctl.d/50-split-lock.conf

add a line kernal.split_lock_mitigate=0 save and quit

In the terminal use this command sysctl -p ~/etc/sysctl.d/50-split-lock.conf

Reboot