Comment 39 for bug 657990

Romain, I'd sas that for additional troubleshooting the issue the following article may give you some hints:
http://linoxide.com/how-tos/cpu-bottleneck-linux/

You should have the following packages installed: procps and sysstat.

First, maximize the terminal window. Then run vmstat and mpstat for a while to see CPU usage, e.g.:

$ vmstat 2 5

$ mpstat 2 5

If you see high %irq you can use the following command to find out which interrupt number is the culprit:

$ sar -I XALL 2 1 | less

And the following command shows the recorded number of interrupts per CPU per IO device:

$ cat /proc/interrupts

which is useful to find out which IO device uses the interrupt (see more in proc(5) man page).

-- rpr.