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Re: Making a VE use a particular cpu [message #34318 is a reply to message #34309] Tue, 23 December 2008 14:48 Go to previous messageGo to previous message
maratrus is currently offline  maratrus
Messages: 1495
Registered: August 2007
Location: Moscow
Senior Member
Hello,

as far as I understand (and please correct me if I'm wrong) cpuset changes task_struct->cpu_allowed field according to its rules.
That's mean that we bind the task not to physical but virtual cpus (it is OpenVZ specific feature). Virtual CPUs are bound to physical CPUs but this connection is not permanent. So, your task could be bound to virtual CPU (vcpu) but actually run on different physical CPUs (pcpu).

We can conduct the following experiment (on the test node!)
Set appropriate sets with cset command as described in previous post.
Run our VE and issue inside that VE the command e.g.
# cat /dev/zero > /dev/null &

then on the HN trigger several times:

# echo "p" > /proc/sysrq-trigger

and look in dmesg. There should be appear information concerning with the task running on that moment (physical and virtual CPUs numbers also should be shown). Our goal is catch "cat" process inside VE running on different physical CPUs.
 
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