Diff between various CPU masks

Hi, I was going through the boot up code and came across the following masks . - CPU online mask : The number of CPU's available for getting scheduled on - CPU active mask : The number of CPU's on which some task can be migrated to (not very clear as to the difference between online and active) - CPU present mask : Total number of CPU's limited by max cpu's variable - CPU possible mask : Total number of possible CPU's in the system But i am not sure if my understanding is correct and wanted to validate the same . Thanks, --Vignesh http://vigneshradhakrishnan.blogspot.com/