The "Cluster CPU" visualization displayed in YARN Summary shows an average utilization of 50% always even when the data nodes are idle. The "CPU Usage" of individual data nodes are close to zero when no jobs are running as seen on "Summary" tab for the host in Ambari. Then why does the "Cluster CPU" graph always show 50% as the avg ? What exactly it is trying to depict ?
The definition says "Percentage of CPU utilized across all NodeManager hosts.". So, when it says 50% avg, does that mean (for example) 4 CPUs out of 8 total CPUs of all NodeManager hosts are being used ?