Re: cpu_exclusive feature of cpuset broken?

From: Paul Jackson
Date: Thu Mar 16 2006 - 11:36:02 EST

Srivatsa wrote:
# cd /dev/cpuset
# mkdir a
# /bin/echo 7 > cpus
# /bin/echo 1 > cpu_exclusive

I have not seen anything resembling such a lockup.

However you are doing something odd here.

While you created a subcpuset 'a', you changed the
cpus and cpu_exclusive in the root cpuset. This
changed -all- tasks to only be allowed to run on
cpu 7.

I'd guess you have some kernel thread or such that
really, really wants to run on some other cpu.

When I read you transcript, I expected it to say:

# mkdir /dev/cpuset
# mount -t cpuset cpuset /dev/cpuset # s/none/cpuset/ - clearer
# cd /dev/cpuset
# mkdir a
# cd a # the missing step
# /bin/echo 7 > cpus
# /bin/echo 1 > cpu_exclusive

The s/none/cpuset/ in the mount command is just a nit.
That field shows up in various mount command error
messages, and 'cpuset' is alot clearer than 'none' in
such messages.

When I do your commands (without the 'cd a'), I don't
see any problem or hang on my Altix test box. But that
probably just means I am not critically depending at that
moment on some kernel thread running on any particular cpu.

I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <pj@xxxxxxx> 1.925.600.0401
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