[Xen-devel] RE: VCPU time reporting!

[Ata Bohra <ata.husain@xxxxxxxxxxx>]

Dear All,
 
I was trying to understand the increased CPU utilization percentage reported by xentop on ay domain (no matter domains waits at getty login). I was able to find that 'nash-hotlplug' process uses almost 100 % of the CPU if system is idle, but being a nice process if you kickoff some job, it relinguishes most of the cpu.
 
By adding 'pkill -9 nash-hotplug' in /etc/rc.local helped me get the normal values of CPU utilization. Just sharing in case some one else also lands in same situation as mine.
 
Thanks!
Ata
  

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From: ata.husain@xxxxxxxxxxx
To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: VCPU time reporting!
Date: Thu, 4 Jun 2009 23:14:29 +0530

Dear All,
 
I am trying to extract the CPU time used by each domain. As per the xentop code, it reports the VCPU time using 'xenstat_vcpu_ns()'. I have a strange observation, I started a ubuntu-8 domain and left it without running any application at the getty login prompt, when I observe the xentop data, it still gives me a constant increase in the VCPU time for both the domain0 and domain1(ubuntu-8).
 
Just to further analyze the data, I ran a large matrix multiplication program on dom0 and expected that the increase in VCPU time for domain0 should increase substantially that domain1 (which is doing nothing), BUT it is observed that the increase in VCPU time is in ration os maximum 1:2 with respect to domain1: domain0.
 
Is there any reason for a idle domain to consume so much of CPU time, I have not set any cap for scheduling thus I observe the domain0 maximum utilization not more than 50% whereas domain1 always shows the CPU utililzation of >= 50%.
 
Is there a more cleaner way to get individual domain CPU utlization parameters.
 
Thanks for your support!
 
Regards,
Ata E Husain
University at Buffalo
 

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