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[Xen-devel] VCPU hotplug problem

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] VCPU hotplug problem
From: "Gabriel Southern" <gsouther@xxxxxxx>
Date: Mon, 11 Feb 2008 22:26:21 -0500
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I am working on a project using the VCPU hotplug feature in Xen, and I
think that there is a problem with how Linux is processing CPU hotplug
events.  The problem I have seen is that the /proc/stat file does not
change the number of CPU entries in response to the: xm vcpu-set
<domain> <num> command.  However, the /proc/cpuinfo file is updated

The reason this is important is that some applications use the
sysconf(_SC_NPROCESSORS_ONLN) to determine how many threads to run.
In Linux this function parses the /proc/stat file to determine how
many processors are available.  However, the /proc/stat file is not
being updated correctly in response to the xm vcpu-set command.

It would be a big help for me if anyone else could test to see if they
experience the same problem.  I'm not sure if this would qualify as a
problem with Linux or with Xen; however, any ideas for fixing it are
appreciated as well.



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