Question about relation between nice value and %CPU

[papoon]

Hi HP UX Expert,

I would like to ask why a process with nice value of 20 can be allcoated more cpu power than those with nice value of 15 (See the attachment). What is the relation between nice value (NI) and priority (PRI) and %CPU? Is the NI is invertedly proportional to priority ? Why processes with same NI can have different PI? Please advise.

Thanks milliion!
Anthony

[Dennis Handly]

It depends on what the two processes are doing. Processes that the kernel determines are unmutual get lower priority.

Typically CPU bound processes get their priority lowered by increasing the PRI value.
http://docs.hp.com/en/B2355-60130/nice.1.html

[Kranti Mahmud]

Hi Papoon,

read this: http://en.wikipedia.org/wiki/Nice_(Unix)

Rgds-Kranti

[Emil Velez]

priority is what the priority of the process is.

Nice value is used to determine how quickly its priority increases when it is waiting for the CPU.

If the program with a nice value of 15 does a lot of I/O it will generate a I/O request and then wait till it finishes where a CPU bound program with a nice value of 20 might get cpu since there is nothing else using the cpu.