[cod] cpu usage patch? :)

Steven Hartland killing at multiplay.co.uk
Tue Oct 5 10:31:35 EDT 2004


Yes I spent much time investigating the issue. Spoke to the developer of ps
and top for a while on the matter. Basically in the linux kernel cpu usages is
measure by the scheduler on a timeslice basis. So if the application gets
scheduled yet yields before using the full timeslice it will have 0 measured
cpu usage. So armed with this knowledge you can write an app which
would use 99% CPU yet read 0 by always yielding just before the time
slice expired. There where patches around which helped fix this but
they do take more cpu cycles. So its a compromise. With quicker
CPU's and low frequency kernels such as the default in 2.4 ( 100Hz )
the likely hood of this happening becomes greater. Its purely usage
patterns so its impossible to predict which apps are and aren't affected.

    Steve / K

----- Original Message ----- 
From: "Andre Lorbach"


I run several sof2 servers on this machine, one of it is usually full
with ~ 20 ppl, LAG FREE and I can see a CPU usage of 10-20%. 
I can imagine that these readings are not that exact, but you don't
wanna tell me that the reading may differ up to 50%?
Do you have any reference for kniown issues? Would be very intersted in
more details about such an "CPU measurement issue"...

Btw the cod server and sof2 server were running lagfree side by side
when I tested with 8 ppl. 


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