[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
level
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
epoch
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.

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