Date: Mon, 17 Jul 2006 14:30:27 +0100 From: Gareth McCaughan <gmccaughan@synaptics-uk.com> To: freebsd-questions@freebsd.org, freebsd-stable@freebsd.org Subject: Re: "swiN: clock sio" process taking 75% CPU Message-ID: <200607171430.27752.gmccaughan@synaptics-uk.com> In-Reply-To: <200607132002.43637.gmccaughan@synaptics-uk.com> References: <200607132002.43637.gmccaughan@synaptics-uk.com>
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I wrote:
> About 6 minutes after booting (on two occasions; I don't
> guarantee that this doesn't vary), a process that appears
> in the output of "ps" as "[swi4: clock sio]" begins to
> use about 3/4 of the machine's CPU. I think it does so
> more or less instantaneously. It continues to do so
> indefinitely, so far as I can tell.
[etc]
No ideas? I'm willing to help track this down, and the machine
in question is sufficiently little used that I can do so without
gross inconvenience; but I don't have enough FreeBSD kernel
expertise to feel like diving in blind.
*
A little more information, in case it's useful to anyone:
| $ echo; sysctl debug | egrep to_
| debug.to_avg_mpcalls: 2890
| debug.to_avg_mtxcalls: 0
| debug.to_avg_gcalls: 768
| debug.to_avg_depth: 3815
That's with HZ = 100. Here are some numbers from a message
in freebsd-ia64, from Marcel Moolenaar, in 2004-07, to someone
seeing symptoms like mine. They're meant to be typical healthy
numbers. Mine above look somewhat worse, but not insanely so;
surely not enough to explain the difference between using
0.3% cpu and using 75%. Marcel also had HZ=100.
| % sysctl debug | grep to_avg
| debug.to_avg_depth: 2500
| debug.to_avg_gcalls: 1003
| debug.to_avg_mpcalls: 1255
*
It would be a shame if the only conclusion to be drawn from this
were "sometimes a machine running FreeBSD is just 4x slower than
it should be, and no one knows why".
--
g
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