What's the difference between niceness and priority?

[jguymon]

I was reading the man page for the top utility, and in the columns there is a column for priority, and a column right next to it for the niceness value. Being somewhat confused by the term niceness, I researched it and found out that the a niceness value of -20 gives a process top priority when consuming CPU cycles... but isn't that what the priority is? What's the difference?

Thanks

Jonathan

[lomcevak]

Google is your friend. I googled 'linux nice priority' and the 1st link it came up with is this:

Linux.com :: Influence scheduling priority with nice and renice

[jguymon]

Hi,

I saw the stuff that explained how to use nice to start a process with a different priority and renice to change the priority of a running process, but what I really want to know is when I run the top command, there is a column (NI) that shows nice values, and a column (PR) that shows the priority values of the process. Because the nice value seems to be the priority level, when I see a process with a nice value of 5 and a priority value of 25, what does it mean and what is the difference between the two values that appear in the columns displayed using the top command?