I have installed Ubuntu GNOME in BIOS mode on my MacBook (BIOS mode so that the proprietary NVIDIA drivers work. I need them for gaming.). For some reason, a lot of CPU is being used while not really doing anything. It swings between 20-30% on both cores, usually. But when I look at the list of processes and sort by CPU usage, I do not see anything special. No processes intensively doing anything. How can I fix this? EDIT: Output of top command. jop@jop-MacBook:~$ top top - 17:08:02 up 41 min, 2 users, load average: 0,51, 0,69, 0,95 Tasks: 202 total, 2 running, 200 sleeping, 0 stopped, 0 zombie %Cpu(s): 11,9 us, 5,8 sy, 0,0 ni, 80,3 id, 0,5 wa, 0,0 hi, 1,5 si, 0,0 st KiB Mem: 7908316 total, 2919940 used, 4988376 free, 153248 buffers KiB Swap: 3906244 total, 0 used, 3906244 free, 1326544 cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 3785 root 20 0 195m 82m 26m S 22,9 1,1 2:43.77 Xorg 4429 jop 20 0 1543m 150m 60m S 7,3 1,9 1:26.26 compiz 4198 jop 20 0 633m 21m 11m S 1,7 0,3 0:04.96 unity-panel-ser 7425 jop 20 0 564m 18m 12m S 1,7 0,2 0:00.84 gnome-terminal 7019 jop 20 0 806m 89m 46m S 1,0 1,2 0:10.01 chrome 7323 jop 20 0 966m 93m 23m S 1,0 1,2 0:06.85 chrome 6742 root 20 0 0 0 0 S 0,7 0,0 0:00.43 kworker/0:3 3 root 20 0 0 0 0 S 0,3 0,0 0:06.01 ksoftirqd/0 7008 root 20 0 0 0 0 S 0,3 0,0 0:00.27 kworker/1:3 7302 jop 20 0 972m 96m 28m S 0,3 1,2 0:06.32 chrome 7310 jop 20 0 382m 63m 39m S 0,3 0,8 0:00.34 chrome 7498 jop 20 0 24840 1600 1120 R 0,3 0,0 0:00.22 top 1 root 20 0 27176 2944 1412 S 0,0 0,0 0:01.58 init 2 root 20 0 0 0 0 S 0,0 0,0 0:00.00 kthreadd 5 root 0 -20 0 0 0 S 0,0 0,0 0:00.00 kworker/0:0H 6 root 20 0 0 0 0 S 0,0 0,0 0:00.00 kworker/u4:0 7 root rt 0 0 0 0 S 0,0 0,0 0:02.04 migration/0 Even when xorg isn't so busy like when I copied, CPU usage is higher then what the processes use.