Poor CPU performance on VM

[skumflum42]

I have a 4vCPU VM that sometimes performs poorly but I have a hard time finding out why. Every night it run some CPU intensive operations.

I have attached some screenshots of CPU and Disk performance graph. There is a big gap between the CPU Demand and Usage but negligible Ready and Co-Stop. I don’t see any disk bottlenecks either.

How can this gap and the occasional poor performance be explained.

[rsicilia]

Hi, can you post a screenshot of CPU utilization of the host in the same time interval?

--

Rocco Sicilia

[skumflum42]

Sure :smileyhappy:

[rsicilia]

Well, I don't see particular issues in this graphs. Host's CPU ready-time is high but vCPU responce with low ready-time when VM demand CPU time.

Can you set CPU reservation and retake the tests?

--

Rocco Sicilia

[skumflum42]

Yes, I will try that!

Do you think ready-time is high? I was under impression that it was very low but I may misinterpreted the data?

Past Day: CPU summation value / 3000

Maximum Ready 434ms = 0,14%

[TryMi]

What power management profile are you running?  I've seen something similar while running a balanced profile vs high performance.

[skumflum42]

High performance

[Linjo]

You also have to check your bios performance settings.

[skumflum42]

The result while CPU reservation enabled. The result is pretty much the same.

Am I correct in my understanding of the values? The Demand value is the speed the CPU would have run if there were no constraints.

In this example the CPU would have run 2x the speed???

[Paltelkalpesh]

1. Is there any other Virtual machines are hosted on this particular host, if yes then try to monitor secondary virtual machine CPU performance 

2. Is there any backup job are running on this period of times.

3. Disable power management and check.

[skumflum42]

1. yes but not many

2. no

3.i will try

[beckham007fifa]

On which hardware your ESXi is sitting, Can you post esxtop output when the performance get worse.

[skumflum42]

By the way, my hardware is HP BL460c Gen8 Intel E5-2600 V2 gen.

The problem was related to power management. I changed all power management settings from “balanced” to “performance/max” in the bios. Now the demand and usage values is virtually the same and the nightly operation almost cut in half! :smileyshocked:

The Power Management Button in the host setting is now grayed out and stuck on “High Performance”.

I was under the impression that setting a power policy from vSphere was enough. Isn’t that how it is supposed to work?

[Linjo]

Great news! The bios setting is mandating the power setting, vSphere can only change it if its set to "OS Controlled" or similar.

// Linjo

[skumflum42]

I would think the default setting is OS controlled since the button no longer is active.

[spravtek]

This KB discusses your case as well, just for reference: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1018206