There are a lot of users struggling with performance in VMs and are going overboard in trying to improve performance.  From what I have read, the biggest issue is with latency in VMs causing choppy video and audio playback and low/erratic FPS while gaming.  It appears that the standard answer is to throw more cpus at a VM.  This is not only wasteful of cpus, it doesn't solve any problems, and is overkill.

 

I would like to suggest some minor changes in the VM manager cpu pinning and add an emulatorpin entry.

 

For example:

 

A Xeon 4 core processor with hyperthreading is laid out as:

 

0,4

1,5

2,6

3,7

 

Suggestions:

• Don't allow a user to pin any of the first core cpus.  Linux tends to favor cpu 0.
  
• Default emulatorpin to pin the first cpu pair.  <emulatorpin cpuset='0,4'>.
  

 

This should help all VMs, but more importantly those with latency issues.

 

I am still doing some experimenting with isolcpus.  I'm not convinced that it is necessary to isolate the cpus.

yes i think that would be a great idea.

 

Further to this some time down the road i would love to see you manually manipulate some things in the user space to allow adding isolcpus capability post-boot.