Loadavg calculation

From: bobyetman@att.net
Date: Sun Nov 05 2000 - 07:55:40 EST


I'm working a project a work that is using Linux to run some very
math-intensive calculations. One of the things we do is use the 1-minute
loadavg to determine how busy the machine is and can we fire off another
program to do more calculations. However, there's a problem with that.

Because it's a 1 minute load average, there's quite a bit of lag time from
when 1 program finishes until the loadavg goes down below a threshold for
our control mechanism to fire off another program.

Let me give an example (all on a 1-cpu PC)

HH:MM:SS
00:00:00 fire off 4 programs
00:01:00 loadavg goes up to 4
00:01:30 3 of the 4 programs finish loadavg still at 4
00:02:20 load avg goes down to 1, below our threshold
00:02:21 we fire off 3 more programs.

We'd like to reduce that almost 50 second lag time. Is it possible, in
user-space, to duplicate the loadavg calculation period, say to a 15
second load average, using the information in /proc?

The other option we looked at, besides using loadavg, was using idle pct%,
but if I read the source for top right, involves reading the entire
process table to calculate clock ticks used and then figuring out how many
weren't used.

Ideas, opinions welcome. Yes, I read the list, so either respond direct
to me, or to the list.

bobyetman@att.net (Robert A. Yetman)

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