Re: softirq considered harmful

David Miller
2006-08-10T11:41:26Z

From: Jens Axboe <axboe@suse.de>
Date: Thu, 10 Aug 2006 13:06:27 +0200

> run_timer_softirq+0x0/0x18e: took 3750
> run_timer_softirq+0x0/0x18e: took 2595
> run_timer_softirq+0x0/0x18e: took 6265
> run_timer_softirq+0x0/0x18e: took 2608
>
> So from 2.6 to 6.2msecs just that handler, auch. During normal running,
> the 2.6 msec variant triggers quite often.

It would be interesting to know what timers ran when
the overhead got this high.

You can probably track this with a per-cpu array
of pointers, have run_timer_softirq record the
t->func pointers into the array as it runs the
current slew of timers, then if the "took" is
very large dump the array.