I’m hoping this information will help others. Hyper-V guests can suffer performance degradation when not in the High Performance Windows Power Plan.
I came across this when a friend and I were trying to run a game server, Space Engineers I believe. We ran into some hard to troubleshoot performance issues. If it was not for the nature of computer games and the reliance on low latencies more so than most other home lab workloads I’m not sure I would have run into this problem.
After a few days of digging and trying different things we discovered that CPU parking was known to cause performance issues in this game and that parking was taking place on the system.
Some suggestions came up to try force the CPU not to park but I decided I’d play with the power settings after reading that this was a normal process carried out for power saving reasons.
Parking was introduced in Win7/Server2008R2.
Like magic everything became much better after changing the power plan. I now ensure all my Hyper-V guests have a group policy applied to them to set the power plan to High Performance. I anecdotally noticed a few other minor improvements with other systems that I didn’t originally attribute to being performance problems.
This was earlier in my HomeLab setup when I was running on an early Core i7 desktop computer running Server 2012 R2 with Hyper-V Role. I have not experimented with this on server running a Xeon processor but as it is primarily Windows Kernel function I imagine it is no different.
In light of this I have of course set my host to run to High Performance also.
There is some good discussion around power plan and performance in general here:
In saying all of this I can still imagine calculated scenario’s that one might might use power saving functions for their VMs. To achieve the obvious cost savings though a lot of effort would need to go into properly testing the applications that will be running on the VMs. Until you’ve done that the high performance plan is your safe bet.