Ubuntu lag, everything stuck every 5 seconds

Solution 1:

I have Ubuntu Server and 2 variants of Ubuntu desktop installed on my Acer Aspire 4820TG. Server and one Desktop are 14.04 the other desktop is 15.04 and I do not have these issues. I think it may be something to do with the Intel Graphics and the Radeon video card. Try making it only use 'Descrete Graphics'.

-Boot up into your BIOS (f2) at startup.
-Go -> to 'Main'
-Scroll to Graphic mode and make it [Discrete].
-Save and Exit

This will make your graphics not switchable. This has seem to fix a lot of things for me. Even on windows switchable graphics was a huge problem for me. Cause BSOD all the time.

Solution 2:

A little late for the party. I know that the answer above is already accepted, but I want to share my experience which might be helpful for others. The problem was something to do with ACPI. I wrote a bash script which solves this problem automatically:

if grep -q acpi_rev_override "/etc/default/grub"; then
 echo 'Found settings entry, nothing changed';
else
 sudo sed -i 's/splash/splash acpi_rev_override=1/g' /etc/default/grub
 echo "Finished successfully. please reboot to apply the new settings"
fi

I'm also posting a reverse script in case it is needed:

if grep -q acpi_rev_override=1 "/etc/default/grub"; then
 sudo sed -i 's/splash acpi_rev_override=1/splash/g' /etc/default/grub
 echo "Reset finished successfully"
else
 echo 'No settings found, exiting.';
fi