Article ID: 119993, created on Feb 5, 2014, last review on May 11, 2014

  • Applies to:
  • Virtuozzo
  • Virtuozzo hypervisor

Symptoms

  • Benchmarking CPU inside a Virtual Machine produces much lower results, comparing to the same test on the host.

  • The VM is configured with certain CPU limitations (amount of CPU cores or CPU limit).

  • Removing any CPU limitation makes the results similar to the ones, observed on the host.

  • The VM doesn't have any other CPU load at the time of the test.

Cause

The delay in CPU operations may be caused by the VM CPUs using different NUMA nodes.

Resolution

  1. Find out the CPU core <-> NUMA node mapping:

    # numactl --hardware
    available: 2 nodes (0-1)
    node 0 cpus: 0 1 2 3 10 11 12 13
    node 0 size: 24567 MB
    node 0 free: 4319 MB
    node 1 cpus: 4 5 6 7 8 9 14 15 16 17 18 19
    node 1 size: 24576 MB
    node 1 free: 2345 MB
    
  2. Bind the VM to specific CPUs, residing in a single NUMA node:

    # prlctl set $VM_NAME --cpumask 0,1,2,3,10,11
    

Search Words

Low CPU performance

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