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qpi
Contributor
Contributor

Single Linux VM on quad-core host machine only utilizing 25% of available CPU

We are running a Fedora Linux VM in VMWare ESX 3.x on a quad-core Dell PowerEdge 2950.

The VM is being stressed by another machine using JMeter. When the server is pushed to the breaking point the CPU Performance Graph only shows that each of the four processors is using on average 25% and the combined CPU Usage Percentage is shown to be 25%.

The VM being tested is the only VM on the ESX server. There is a single resource pool which has been set to "High" for both CPU and Memory.

Together all the CPUs show to have 7477 MHz in the resource pool.

The single VM shows in the "Resource Allocation" tab when the single resource pool is selected. When I right click the VM and select "Edit Resource Settings..." the settings are NOT retained.

I am within the 60 day trial period of ESX server. Is this a trial limitation?

Should I be able to have the "Edit Resource Settings" be preserved? How do I get each CPU to utilize more than the 25% shown?

Message was edited by: qpi. First posting and I did not correctly formulate it as a question.

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6 Replies
tbrouwer
Hot Shot
Hot Shot

You can only use the full power of one core. Hence the reason it is showing 25% utilization.

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Chris_S_UK
Expert
Expert

as the other poster implied, if your VM has only 1 vCPU, then this is expected behaviour.

Reconfigure your VM with 4 vCPUs if you want it to be able to use all the host's CPU power.

Chris

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TomHowarth
Leadership
Leadership

Firstly welcome to the forums,

the behavior that you are experiencing is expected, a single vCPU guest will only ever address a single core. this is by design. ESX is designed to run serveral Guests on a single host, increase the amount of guests or the amount of vCPU in the guest and you will see the host start to sweat.

Tom Howarth

VMware Communities User Moderator

Tom Howarth VCP / VCAP / vExpert
VMware Communities User Moderator
Blog: http://www.planetvm.net
Contributing author on VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment
Contributing author on VCP VMware Certified Professional on VSphere 4 Study Guide: Exam VCP-410
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qpi
Contributor
Contributor

Thank you.

Is this limitation because I am using a trial version of ESX? A limitation of the chip set? A limitation on our software stack? Or some other limitation?

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qpi
Contributor
Contributor

The VM is already set to use 4 processors and is showing the problem.

The VM was moved over from a VMWare Server using the VMWare Converter. It has the same settings except I did increase the processors to 4.

Anything else I should change or check?

Is there a suggested benchmark virtual appliance I can use to seperate specifics of the host from that of the VM?

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mcowger
Immortal
Immortal

Is your VM running an SMP kernel?

--Matt

--Matt VCDX #52 blog.cowger.us
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