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I running here Ubuntu 16.04 as KVM Host. In a VM runs Windows with a time critical process (UDP Video Stream)

Sometime when other process runs on the host, for a moment it influence the CPU usage from the VM so that I get a short error in my stream.

I play with renice (-10), ionice and chrt (-r -p 70), but it have only a little impact. It looks like, the the CPU scheduler need a short moment to set prioritization and that moment is to long. But I don't now, I'm not a kernel expert.

My VMs have not more CPU cores then my host have, in reality there are two left, and the average CPU usage is around 20%. On the host runs also DHCP, DNS and spuid/squidguard and some crons, but all have no much cpu usage. I can also simulate a error with stress -c 6, for example.

Is there a way to stabilize the CPU usage for the VM?

I thought on cpu pinning, but some people don't recommend this.

KVM Version is 2.5, and on Windows all virtio driver a new.

  • Lesson learned? Do not put ANY time critical things on a VM. Period. – TomTom Nov 28 '16 at 13:07
  • The software who is running is Cloud certificated, so it must be possible to run it in a VM. The virtualization is not the problem, when I run other VMs with high CPU load, it have no effect at all. At the moment I only make a long time test, so in the worst situation I always can change back to a physical computer. My goal is to run it on a other server, where is less activities on the host side, but before this I need to be sure that I get it to work. Beside this, in 2010/11 you found already presentations where people use KVM for real time processes. – jb_alvarado Nov 28 '16 at 13:15
  • Current KVM version? All drivers up to date? Certification is also for KVM? Kernel configured for fast response time? We lack information to do anything but guess. – TomTom Nov 28 '16 at 13:26
  • I update my post with KVM version and driver Information. About the cloud certification, here is what the vendor says: Cinegy Air PRO can run in a VMWARE ESX, Microsoft Hyper-V, Citrix XenServer virtual environment (VM) and is available on Amazon Web Services Marketplace as well. KVM is not listed, but I don't belief this is a problem. I have not make Kernel configurations, when there is a chance to do this without recompiling, I really would like to know this. Using centos can also be a option, if this is better in KVM. – jb_alvarado Nov 28 '16 at 13:45
  • It may well be a problem with KVM at this point. I am inclined to close - we do not deal with "hack" configs (require: best business practices) and KVM is not a supported hypervisor. But I will leave it. This really could be a driver problem. I suggest trying with Hyper-V (free trial available) or any supported hypervisor to validate. – TomTom Nov 28 '16 at 13:49

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