Three server processes limited to one CPU core

Hi!


I have a Debian server running three instances of Counter-Strike.
Processor is Intel Core 2 Duo E4500 2.2 GHz. Recently I have noticed
that CPU load cannot go higher than 50% of total processing power (two
cores). There is mrtg graph attached showing user cpu load (green) and
idle times (blue). As you can see from the graph, user cpu load is
topped at 50% and does not go higher (14-22 pm yesterday). Today,
around 20 pm I have forced more loaded instance to CPU#0 with command
'schedtool -a 0x01 <PID1>' and two other instances with fewer players
to CPU#1 ('schedtool -a 0x02 <PID{2,3}>'). Before that adjustment,
affinity masks were 0x03 for all three instances, and from the 'top'
output I was able to see that both cores were running, just their
combined load was never higher than 50%. After I've set new
affinities, total CPU load goes higher, as you can see from the graph.

Why do these three instances consume no more than 50% with default
affinity setting when they are permitted to run on any core available
and why they are able to take more after such adjustment? Any hints?


-- 
Timur Irmatov, xmpp:[email protected]