UNIX for Dummies Questions & Answers

Can someone tell me this. thanks

If you have more runable processes than you have cpu's, nice could be useful. In the unlikely event that you only have one process that you want to run, then even with a single cpu, nice can't do anything...(nothing else to nice down). But on unix, there are always enough processes that you could find something to nice. The thing is though, that I rarely use nice. The unix scheduler is very good and I just let it pick the priorities. If you're thinking that nice used to be more useful than it is today, you're right. But that is more due to cpu speed, rather than number. Today's cpus have clocks running at Gigahertz speed and have super-scalar architectures that can execute mutiple instructions every cycle. Most unix processes wind up waiting on i/o, and high priority or no, they can't run until their data arrives. When your processes are voluntarily surrendering the cpu before they use all of their timeslice, nice can't really impact very much. It's not that unusual to have a heavy load, but lots of cpu idle time. The other big factor is advancements in scheduling algorithms. Still, if you have multiple processes do calculations with no i/o and competing for the same cpu, nice can have a big impact on which one does the most calculations. That's not the mix of processes that most of us have.