Re: ksoftirqd using mysteriously high amounts of CPU time

From: Brad Laue
Date: Thu Mar 11 2004 - 03:42:02 EST

Andrew Morton wrote:
Please ensure that the machine was booted with `profile=1' on
the kernel boot command line. The cost of this is negligible.

When the problem starts happening, run:

sudo readprofile -r
sleep 10
sudo readprofile -n -v -m /boot/ | sort -n +2 | tail -40

(make sure that /boot/ refers to the currently-running kernel)

Gave the machine a bit of a workout to create the problem sooner than usual, albeit on a smaller scale. ksoftirqd consumed about 4.7% of the CPU according to top after several concurrent wget operations, and had accumulated about 6 seconds of runtime, unheard of for a system uptime of 15 minutes; the output attached is during this.

Hopefully I'm right in assuming that; on all other systems I've experimented with ksoftirqd doesn't even flinch unless subjected to extremes.

Did some further testing with a machine of identical configuration (suffers the same issue too); removed iptables from the suspects list, as the issue exists sans those modules.

Hopefully the attached shows some irregularity. If not, I'll have to reply back in a few weeks when the problem recurs over the course of time.

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