Why is intr taking up so much cpu?

Dan Nelson dnelson at allantgroup.com
Tue Jul 20 17:15:59 UTC 2010


In the last episode (Jul 19), Doug Barton said:
> On Sun, 18 Jul 2010, Dan Nelson wrote:
> > You can also use dtrace to get a count of callouts and their time spent. 
> > Run this for a few seconds then hit ^C:
> 
> Okey dokey, here you go:
> 
> http://people.freebsd.org/~dougb/normal-dtrace.txt
> http://people.freebsd.org/~dougb/bad-dtrace.txt

I don't see any real difference between those two runs, so maybe it's not a
callout eating your CPU.  How about running this for a few seconds, which
will print all the stack traces seen during the sampling period:

dtrace -n 'profile:::profile-276hz { @pc[stack()]=count(); }'

On an otherwise idle system, you should see most of the counts in cpu_idle,
with the remainder clustered in whatever code is eating your CPU.

-- 
	Dan Nelson
	dnelson at allantgroup.com


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