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CPU and Memory overcommit defaults in Pike?

asked 2018-02-25 03:37:52 -0500

tonyp12 gravatar image

What are the overcommit defaults in Pike for cpu and memory on compute nodes? This linke states that cpu is 16:1 and memory is 1.5:1 : : https://docs.openstack.org/arch-design/design-compute/design-compute-overcommit.html (https://docs.openstack.org/arch-desig...)

When I checked nova.conf on the compute nodes it says this (and it's confusing to me):

This option helps you specify virtual CPU to physical CPU allocation ratio.

From Ocata (15.0.0) this is used to influence the hosts selected by the Placement API. Note that when Placement is used, the CoreFilter is redundant, because the Placement API will have already filtered out hosts that would have failed the CoreFilter.

This configuration specifies ratio for CoreFilter which can be set per compute node. For AggregateCoreFilter, it will fall back to this configuration value if no per-aggregate setting is found.

NOTE: This can be set per-compute, or if set to 0.0, the value set on the scheduler node(s) or compute node(s) will be used and defaulted to 16.0.

NOTE: As of the 16.0.0 Pike release, this configuration option is ignored for the ironic.IronicDriver compute driver and is hardcoded to 1.0.

Possible values:

  • Any valid positive integer or float value (floating point value) Minimum value: 0 cpu_allocation_ratio=0.0

I checked ironic.conf and couldnt find a similar cpu overcommit value, so I am confused about what overcommit is presently set to and where it is now configurable.

can you help?

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answered 2018-02-25 05:09:19 -0500

This means that there is no overcommit when you use Ironic. Since you talk about compute nodes rather than baremetal nodes, my guess is that you don’t use Ironic, and the default CPU overcommit is 16.

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How would I know if we use Ironic? I'm guessing we do not but just to check and be safe.. Thanks again Bernd

tonyp12 gravatar imagetonyp12 ( 2018-02-25 19:46:04 -0500 )edit

Ironic is the baremetal service. You use it to implement instances as physical machines rather than VMs. If you don’t know whether you use Ironic, chances are you don’t.

To confirm, check nova.conf on the compute nodes. If you see compute_driver=ironic.IronicDriver, this compute node uses Ironic.

Bernd Bausch gravatar imageBernd Bausch ( 2018-02-25 22:51:19 -0500 )edit

Thanks! It's libvirt

tonyp12 gravatar imagetonyp12 ( 2018-02-26 02:04:26 -0500 )edit

In this case, your overcommit is 16 if you don't override the default.

Bernd Bausch gravatar imageBernd Bausch ( 2018-02-26 08:24:54 -0500 )edit

Excellent thank you!

tonyp12 gravatar imagetonyp12 ( 2018-02-26 19:22:40 -0500 )edit

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Asked: 2018-02-25 03:37:52 -0500

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Last updated: Feb 25