Suggestion for improvement: nice

[Henrik Haraldsson]

(This is a suggestion for an improvement, not a proper bug report)

A process running with nice -19 still gets 14% of the CPU when there is
a non-nice process in parallell. If there is a nice -10 process running
in parallell with a nice -19 process, the nice -19 process gets 25% of
the CPU. 

I see this as highly undesireable. I would like a nice -20 level, which
takes 0% CPU power if there is another process asking for 99%. (Or
change nice -19 so that it works like this.) "nice" was working like
this on our old unix system (alpha stations): the nicest level meant
that the process stopped running if there was another process asking for
the CPU. (If the other process only asked for 30% of the processor, the
maximum-nice process kept 70% CPU, of course.) E.g. if there was a nice
-18 process running in parallell with a nice -19 process (the nicest
level), the nice -18 process got 99% of the CPU and the nice -19 got 0%.

I'm a Ph.D. student in complex systems, and we have many people who want
to run processes on our linux machines. If I had a nice like on the
alpha unix, I could start a two-week low priority processes with maximum
niceness, knowing that I'm not disturbing anybody. Now I need to think
first, because there might be somebody who also wants to wants to run a
nice process, but one that only takes a day. Then I want them to have
all of the CPU. As it is now, they might set nice -18 - then I get
almost half of the CPU, which I don't want. If they set nice -10 I still
get 25% of the CPU (which I don't want), PLUS the nice -10 person might
feel that he is stealing CPU from people who might want to run with zero
nice. A "I'm giving all other processes priority" nice level would solve
that.

hope this is of help - keep up the good work

Henrik Haraldsson