Re: process priority at 25

[Steven Smith <sos22@cam.ac.uk>]

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> I alway thought process priorities range from -20 to 19 (also according to
> "man nice"). But under kernel 2.5.16 I run top and process is display with
> priority 25..
A process's nice value is not the same thing as its priority. niceness
is used in the calculation of priority, but they're not bound together.
In particular, a process's priority is liable to become numerically
greater (-> lower priority) if it makes heavy use of the processor
(this is supposed to stop something like ``while (1) ; '' bringing
down the system), while a process which makes heavy use of the disk
is likely to get slightly higher priority (because as soon as it hits
the disk, it blocks, and something else can run).

Under 2.4 kernels, priority is constrained between 0 and 20 (for non-realtime
processes), but there's no reason why the same thing should apply to 2.5
kernels.

Steven Smith,
sos22@cam.ac.uk.

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