* Andrew Morton <[email protected]> wrote:
> On Mon, 26 Nov 2007 20:36:32 -0600 (CST) [email protected] wrote:
>
> > Question: Why is ksoftirqd eating about 5 to 10 percent of my CPU on an idle
> > system? The problem occurs if I config the kernel with tickless
> > support (i.e. CONFIG_TICK_ONESHOT=y). (Thanks to "oprofile" for putting me
> > onto this.)
>
> beware that oprofile can provide misleading results on a paritally-idle
> system. You may have discovered that ksoftirqd is consuming 5-10% of the
> non-idle time on that idle system, which is less surprising.
>
> > I have noted this same problem on kernel versions: 2.6.23.1, 2.6.23.8 and
> > 2.6.23.9
> >
> > **************************************************************************
> > *** Output from "vmstat -n 1 10" -- Note very high context switch rate ***
> > *** This is on a idle machine! ***
> > **************************************************************************
> >
> > procs -----------memory---------- ---swap-- -----io---- --system--
> > ----cpu----
> > r b swpd free buff cache si so bi bo in cs us sy
> > id wa
> > 0 0 0 1925556 4768 116104 0 0 124 2 6 7538 1 2
> > 96 1
> > 0 0 0 1925556 4768 116104 0 0 0 0 2 147329 0 1
> > 99 0
> > 0 0 0 1925548 4768 116104 0 0 0 0 0 154515 0 1
> > 99 0
> > 0 0 0 1925548 4768 116104 0 0 0 0 1 153898 0 2
> > 98 0
> > 0 0 0 1925548 4780 116104 0 0 0 16 3 155216 0 1
> > 99 0
> > 0 0 0 1925548 4780 116104 0 0 0 0 1 161718 0 1
> > 99 0
> > 0 0 0 1925548 4780 116104 0 0 0 0 0 147587 0 2
> > 98 0
> > 0 0 0 1925548 4780 116104 0 0 0 0 1 153524 0 2
> > 98 0
> > 0 0 0 1925448 4780 116104 0 0 0 0 0 153434 0 1
> > 99 0
> > 0 0 0 1925448 4792 116092 0 0 0 16 4 153527 0 2
> > 98 0
>
> So what piece of code is scheduling so much? What does `top' say?
> What does the (sorted) output of oprofile look like?
>
> Did you try shutting down as much userspace code as possible to find
> out if some userspace task is misbehaving?
such 'what the heck is happening' problems can also be debugged via the
tracer. Here's a quickstart:
http://redhat.com/~mingo/latency-tracing-patches/tracing-QuickStart.txt
Ingo
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
