Date: Thu, 15 Dec 2011 13:04:21 -0800 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: Doug Barton <dougb@FreeBSD.org> Cc: freebsd-stable@FreeBSD.org Subject: Re: swi4: clock taking 40% cpu?!? Message-ID: <20111215210421.GA33083@icarus.home.lan> In-Reply-To: <4EEA5DD0.1040009@FreeBSD.org> References: <4EEA5DD0.1040009@FreeBSD.org>
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On Thu, Dec 15, 2011 at 12:51:28PM -0800, Doug Barton wrote:
> Howdy,
>
> Web server under heavy'ish load (7 on a 2 cpu system) running
> 8.2-RELEASE-p4 i386 I'm seeing this:
>
> PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU COMMAND
> 12 root -32 - 0K 112K WAIT 0 129:01 39.99% {swi4: clock}
>
> Any ideas why the clock should be taking so much cpu? HZ=100 if that
> makes a difference ...
Could be wrong, but I believe this correlates with IRQ 4. What does
vmstat -i show for a total and rate for irq4 if you run it, wait a
few seconds, then run it again? Does the number greatly/rapidly
increase?
Shot in the dark here, but the only thing I can think of that might
cause this is software being extremely aggressive with calls to things
like gettimeofday(2) or clock_gettime(2). Really not sure. ntpd maybe
(unlikely but possible)? Sort of grasping at straws here.
--
| Jeremy Chadwick jdc at parodius.com |
| Parodius Networking http://www.parodius.com/ |
| UNIX Systems Administrator Mountain View, CA, US |
| Making life hard for others since 1977. PGP 4BD6C0CB |
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