Lawrence Stewart wrote:
On 09/21/10 02:21, David Xu wrote:
jhell wrote:
On Mon, 20 Sep 2010 10:26, David Xu wrote:
In Message-Id: <4c976f14.8000...@freebsd.org>
jhell wrote:
On 09/19/2010 09:28, David Xu wrote:
just typed sysctl -a on keyboard, and found it is slow, sometimes
it has been stuck for a few seconds, further studied,I found it is
stucked at sysctl kern.geom:
%/usr/bin/time sysctl -a kern.geom
kern.geom.collectstats: 1
kern.geom.debugflags: 0
kern.geom.label.debug: 0
kern.geom.label.ext2fs.enable: 1
kern.geom.label.iso9660.enable: 1
kern.geom.label.msdosfs.enable: 1
kern.geom.label.ntfs.enable: 1
kern.geom.label.reiserfs.enable: 1
kern.geom.label.ufs.enable: 1
kern.geom.label.ufsid.enable: 1
kern.geom.label.gptid.enable: 1
kern.geom.label.gpt.enable: 1
2.01 real 0.00 user 0.00 sys
it seems it needs more than 2 seconds to complete.
A ktrace(1) and a kdump(1) of the resulting ktrace.out file would
probably help here along with uname -a. Ive seen this happen once
before
but do not recall what caused it.
Regards & good luck,
Result is dumped here.
http://people.freebsd.org/~davidxu/sysctl_slow.txt
I think the culprit is sysctl kern.geom.confdot,
which does not appear in normal output, until I check the kdump result.
I tried five times, and it was blocked three times.
Inspecting the output of sysctl -b kern.geom.confdot will give you
what you currently have configured in the system as disks and what not
through geom. If this seems to be bailing at that point, which is an
opaque MIB/OID which doesn't come up other than when you use the "-o"
switch to sysctl(1) then could you check your labels for your disks
for any weird characters in the labels ?
( sysctl -bo kern.geom )
Also does this have the same effect when run in a xterm, cons25
terminal ?
And same for the above but with the C, *_COUNTRY.UTF-8 or your normal
locale ?
( env LANG=C sysctl kern.geom )
Looking at the output from mine there are quite a few unprintable
characters present. Maybe these are having an impact with one of your
labels.
I redirect all output to a disk file, and it still needs 1 second to
complete, this machine is dual-core pentium E5500, faster than previous
one which is a dual-core AMD 5000+ machine, the 5000+ needs 2
seconds to complete.
$/usr/bin/time sysctl -b kern.geom.confdot > sysctl_geom_confdot.txt
1.00 real 0.00 user 0.00 sys
the file is here:
http://people.freebsd.org/~davidxu/sysctl_geom_confdot.txt
As an extra data point, running "/usr/bin/time sysctl -b
kern.geom.confdot" repeatedly on my amd64 8.1-STABLE desktop varies
between 0s and 2s. It reports 0 majority of the time but every 5 or so
runs it'll stall for 1 or 2 seconds. So the problem isn't isolated to head.
Cheers,
Lawrence
I happened to set kern.sched.preempt_thresh=200, so the kernel is more
aggressive
than default on thread preemption. it is easier than default to
reproduce the
problem, my desktop machine is idle, but it still stalls 1 or 2
seconds on the sysctl.
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