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Comment thread started by heinrich321 on Virtual Machine Compute Optimizer

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May 07, 2021

We used the VMCO fling to optimize our VMs and made many changes over the past month. A lot of our VMs are 4+ cores, many 8 and 16 cores, and it suggested we move all our VMs to 1 socket and (4, 8, and 16) core setups.

However, our CPU ready time was astronomical... Like 80,000+ ms. Our CPU utilization on each host was only ~25%. We are running single-socket EPYCs host, each with 64 cores/128 threads.

We have since moved almost all of our VMs back to (1) core-per-socket and 4, 8, and 16 sockets. Now our CPU ready time is ~100ms or less for most of our VMs, 300-400ms for some of the heavy hitters.

Since moving back to (1) core-per-socket the VMs feel snappier but we made the changes yesterday and haven't had time to do proper testing. Any suggestions?

May 19, 2021

Heinrich, I apologize for the slow reply! Can you confirm what version of vSphere you are running in your environment? There are some versions that had performance issues w/ the EPYC processors, so a good place to start troubleshooting. See this KB:


May 19, 2021

Mark thanks for the reply. We are using vSphere 7.0 U2 ( and have AMD EPYC 7742 (Rome) processors.

We looked through this guide (Page 27)

We followed these recommendations:

- NUMA nodes per socket = 1
- CCX-as-NUMA = Disabled

These past few weeks the systems seem to be running much better, CPU Ready time is down considerably. Unfortunately I don't have a good benchmark test (before/after) to show...