Friday, October 14, 2005

High Kernel Usage

Bernd Haug <h...@berndhaug.net> wrote:
> sean...@yahoo.com <sean...@yahoo.com> wrote:
>> TOP shows Kernel has been using over 55% CPU.
>> How can we find what are those kernel's processes? why do those use a
>> lot of CPU? Normally i only see about 10%.
> Wouldn't spending some time in syscalls be pretty normal on a DB
> server?

Not that much.

> I rather think it's funny that you have 0 iowait.
> Maybe something went wrong and now your top conflates the two into
> kernel time?

Remember that IOwait is only a subset of idle time. If you have no idle
time, then you can't display any IOwait (even if the disks are slow).

I'd look to see if the "last PID" is increasing rapidly. A constantly
forking program that creates new processes which are quickly reaped will
eat up tons of system time. Difficult to trace directly (well, without
Solaris 10 and dtrace).

Take some guesses and run 'truss' looking for forks.

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