impossible to use more than 50% of the selected core of container

[MhmtErsy]

Bug description

I have a problem with JupyterHub-YarnSpawner. When I launch a X core-Y GB server. I can't use more than 50% of the X core. I have been using CDH platform with YARN that configured as Fair Scheduler.

For example I launched a server with 8 core 16 GB. There is no problem with memory, I can use 100% of 16G but I cannot exceed more than 4 core. Is this a bug related with YARN or YARN Fair Scheduler ?

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