[64studio-devel] CPU load reading too high on dual-core and SMP machines?

[Daniel James]

Hello all,

We have noticed that when running 64 Studio 0.9.6 (jackd 0.102.20) on an 
AMD Athlon 64 X2 dual-core machine and a dual Opteron (two single core 
CPUs) that Jack applications (e.g. qjackctl and jamin) report the CPU 
load as double that which top reports for total CPU load. Jack seems to 
be reporting the sum of both CPU loads rather than the average across cores.

So for example, if you run three instances of Jamin, top might report:

Cpu0  : 26.0%us
Cpu1  : 57.2%us

But qjackctl and all the instances of jamin say CPU load is 83%.

Then if we run five instances of Jamin, to simulate a rather heavy DSP 
session, the Jack CPU counter wraps after 100%. Top says:

Cpu0  : 68.6%us
Cpu1  : 62.7%us

but qjackctl and the jamins now all say CPU load is only 31%. I was 
hoping they would say 131% :-)

Can anyone else reproduce this on a multi-core or multi-CPU system? Or 
is there a flaw in our implementation?

Should we be encouraging multi-core and multi-cpu users to run jackdmp 
instead, bearing in mind that jackd is working fine and we are aiming to 
provide a solid distro that people can use and rely on today?

Cheers!

Daniel