My Ubuntu 12.04 x64 on Dell XPS 15 with 8GB of RAM has been really sluggish.
After some searching I came across post about swappiness. I noticed that swappiness on my system was reported as 0 which means swapping should only start when memory is all used and yet is was actually acting much the same as when swappiness is 60.
I set swappiness to 10 using:
echo 10 > /proc/sys/vm/swappiness
and update /etc/sysctl.conf with:
vm.swappiness = 10
After rebooting I notice that swappiness is reported as 0 again with same sluggish performance. I ran echo 10 > /proc/sys/vm/swappiness and the performance improved remarkably.
I rebooted again and check swappiness, it was reported as 0 again. I executed sudo sysctl -p and could see the values from sysctl.conf take effect.
It seems that the values from /etc/sysctl.conf is ignored on boot.
I have a notebook with Ubuntu 12.04 32 bit and I also applied the same configuration. On the notebook the changes do take effect as expected and remain after a reboot.
Has anyone come across this kind of problem?