[svlug] Linux process priorities/contention

Ian MacLure imaclure at seagull.com
Fri Nov 30 13:33:01 PST 2001

I have been asked the following question.

What is the max number of distinct priority levels it is possible to have
for processes
running on a Linux box.

Given that you have a number of processes running at the same priority
how is contention resolved.

Not being in possession of TFM...
Went to the web...

Found O'Reilly's understanding the linux kernel stuff on-line. Cool....
( http://www.oreilly.com/catalog/linuxkernel/chapter/ch10.html )

Read it.
Understood some of it.

Static Priorities are 0-99 ( 100 total ), real-time, user assigned,
scheduler independent
( Can multiple processes run at the same realtime priority ?)
Dynamic priorities are base priority + ticks left in quantum of currrent
Static priorities trump dynamic.
Dynamic priorities look like they tend to resolve themselves
contentionwise ( more or
less ).

As to contention it looks like FCFS ( 1st come 1st served ) unless a
process is waiting 
for some service in which case the next in line proceeds.

Is this essentially corrrect.

Ian B MacLure                                       Air Transportation
imaclure at seagull.com                          Seagull Technology, Inc.
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