Yarn Physical to Virtual Core multiplier

[#1]

We use CDH version 5.7.1 and Cloudera Manager 5.8.

In Yarn tuning Excel, I see a field called "Physical Cores to Vcores Multiplier" which has the following description:

"Set this ratio based on the expected number of concurrent threads per core. Use 1 for CPU intensive tasks up to 4 for standard I/O bound tasks."

I could not find a Cloudera Manager setting corresponding to it. How do we tell Yarn that it can use a multiplier of 4 ? Is there a default value to it ?

Or is this multiplier indicated to Yarn by setting "yarn.nodemanager.resource.cpu-vcores" parameter to a desired value instead of just the count of physical core ?

Say, if I have 24 physical cores, and I intend to use 50% of it for Yarn, then should I put 12 for this parameter to indicate that I want a ratio of 1:1 and put 48 to indicate a ratio of 1:4 ?

We use static pool resource allocation for various Hadoop components (Hbase, Solr, Hadoop, Yarn) and we set ~50% of resources to Yarn. But I could not find the multiplier anywhere.

Thanks,

Vivek

[#2 · Accepted solution]

The "multiplier" is not a parameter.

You directly set the number of vcpu you want yarn to use. I guess you have to do the math yourself before setting the value.

[#3]

Thank you Mathieu.d

Is this the vcpu parameter you are referring to ? yarn.nodemanager.resource.cpu-vcores

Thanks,

Vivek

[#4]

Yes, this one.

[#5]

Thanks for confirming. I appreciate your quick feedback.