Why is intr taking up so much cpu?

Kostik Belousov kostikbel at gmail.com
Sat Jul 17 19:21:33 UTC 2010

On Sat, Jul 17, 2010 at 12:10:26PM -0700, Doug Barton wrote:
> On Sat, 17 Jul 2010, Rui Paulo wrote:
> >This doesn't indicate any problem. I suggest you try to figure out what 
> >interrupt is causing this by adding printfs or disabling drivers one by 
> >one.
> I've no idea where to even begin on something like that. Given that 
> there are other -current users who are also having problems 
> (particularly with the nvidia drivers) I'm wondering if some sort of 
> systemic debugging isn't in order here?

Note that intr time most likely come from the interrupt threads chewing
the CPU, not from the real interrupt handlers doing something, and definitely
not due to the high interrupt rate, as your vmstat -i output already shown.

Run top in the mode where all system threads are shown separately
(e.g. top -HS seems to do it), then watch what thread eats the processor.
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