Why is intr taking up so much cpu?

Kostik Belousov kostikbel at gmail.com
Tue Jul 20 13:26:49 UTC 2010

On Mon, Jul 19, 2010 at 11:05:26PM -0700, Doug Barton wrote:
> On Sun, 18 Jul 2010, Kostik Belousov wrote:
> >When intr time starts accumulating again, try to do
> >"procstat -kk <intr process pid>" and correlate the clock thread tid
> >with the backtrace. Might be, it helps to guess what callouts are eating
> >the CPU.
> Ok, I thought I was going to be able to do this easily but I didn't 
> realize that the numbers in the second column were thread ids, and I 
> don't know how to "correlate the clock thread tid with the backtrace." 
> Can you give me a hint? :)

It already printed the thread names, so no need. Unfortunately,
the clock threads were running instead of blocking etc (I suspected
that this would be a case), so procstat cannot get the backtrace.
Another option is to do a backtrace from ddb.

I cannot get much information from the dtrace snippets you posted in
parallel. I can only see that some threads used msleep (?) with timeout
a lot, and something at the address 0xc67bbe90 also raised a head.
Can you manually lookup nearby symbol for 0xc67bbe90 ?
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