Intel CPU setup. C-States and all that

[heratic]

Hi I'm currently trying to setup my server to run VM's on.  I'm wondering what settings i need to enable/ disable to get good single core performance for gaming.

 

Do C states cause any issues with unraid?

 

Will unraid let the cpu boost to turbo frequency if p states are enabled or do i have to change something.

 

I noticed when i start unraid it states CPU frequency governor is set to power save. If there a way to change that?

 

Is there any way to check that the cpu hits turbo frequencies?

 

Can anyone explain what bios settings are good to have enabled/disabled to get maximum performance for VM's with unraid. Thanks for any help.

[bonkers]

To prevent issues on my machine with 2 VM's that have to run at max performance when they are running i disabled C-states and the CPU is locked on a decent overclock. I can check on cpu frequency with 'lscpu' command via SSH.

 

From overclock.net:

C states are processor idle states. The more C states you have enabled, the more aggressively your CPU can throttle down its power usage when it is idle. When it detects computer activity (a hardware interrupt), it will throttle back up to C0 (full power state). If you disable C states, your CPU will be in C0 state all the time. A Google search for C states will have more technical explanations.

This website is worth a read if you have some time and are willing to do some reading:

http://www.hardwaresecrets.com/everything-you-need-to-know-about-the-cpu-c-states-power-saving-modes/

 

Your ideal settings will depend on what kind of VM's you have, and if your system is stable when C-states are enabled. I have found that a heavily overclocked CPU dislikes enabled C-states but your mileage may vary. Best way to test performance in your particular usage scenario is to actually test it on your system 

[heratic]

To prevent issues on my machine with 2 VM's that have to run at max performance when they are running i disabled C-states and the CPU is locked on a decent overclock. I can check on cpu frequency with 'lscpu' command via SSH.

 

From overclock.net:

C states are processor idle states. The more C states you have enabled, the more aggressively your CPU can throttle down its power usage when it is idle. When it detects computer activity (a hardware interrupt), it will throttle back up to C0 (full power state). If you disable C states, your CPU will be in C0 state all the time. A Google search for C states will have more technical explanations.

This website is worth a read if you have some time and are willing to do some reading:

http://www.hardwaresecrets.com/everything-you-need-to-know-about-the-cpu-c-states-power-saving-modes/

 

Your ideal settings will depend on what kind of VM's you have, and if your system is stable when C-states are enabled. I have found that a heavily overclocked CPU dislikes enabled C-states but your mileage may vary. Best way to test performance in your particular usage scenario is to actually test it on your system 

 

I use this to see CPU frequencies in real time

 

watch grep \"cpu MHz\" /proc/cpuinfo

 

I'm using Intel p states driver. I worked out that the Performance Governor wasn't letting my CPU E5-2689v4 use turbo frequencies. Switching back to the powersave profile and all is well again.

[Ph9214]

they will cause latency in some situations putting it up from the standard ~0.5 latency to ~100 !!!

 

you can check this with latencymon

 

you may also want to disable thermal throtteling