Friday, October 19, 2012

CPU utilization over 100%

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This week my client faced a weird situation, the CPU utilization of theirs ESXi host were over 100% !!!

Just as informational, the high utilization on their VMs, which caused the hosts to have a high CPU utilization, was not VMware related ; )

We know the hosts were in a high utilization period, but how was be over 100% possible ?


  
I started looking at vSphere Monitoring andPerformance, on page 49 I found a nice description of the CPU utilization.

 
The note on that description gave me the first clue

NOTE If a PCPU is running at frequency that is higher than its nominal (rated) frequency, then PCPU USED(%) can be greater than 100%.
Now that I confirmed that it’s possible, I decided to look for what could be allowing that.
Very soon I figured out that it’s a feature on Intel processors called Intel® Turbo Boost Technology.
When it’s enabled it allows the processor to transition to a higher frequency in order to give more horsepower during peak periods.
 
 I hope you don’t have to face extreme situations like this, but if you do that’s how you explain it to your boss.

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I’m an IT specialist with over 15 years of experience, working from IT infrastructure to management products, troubleshooting and project management skills from medium to large environments. Nowadays I'm working for VMware as a Consulting Architect, helping customers to embrace the Cloud Era and make them successfully on their journey. Despite the fact I'm a VMware employee these postings reflect my own opinion and do not represents VMware's position, strategies or opinions.

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