f9: question on load average

[Patrick O'Callaghan]

On Mon, 2008-09-15 at 10:46 +0200, Dario Lesca wrote:
> Hello! Why on this system the value of load average is so Higt?
> 
> > top - 10:42:27 up 3 days, 16:22,  1 user,  load average: 5.08, 5.05, 5.01
> > Tasks: 166 total,   1 running, 165 sleeping,   0 stopped,   0 zombie
> > Cpu0  :  0.0%us,  0.3%sy,  0.0%ni, 99.7%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
> > Cpu1  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
> > Cpu2  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
> > Cpu3  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
> > Mem:   2074912k total,  2014468k used,    60444k free,       40k buffers
> > Swap:  3571704k total,       60k used,  3571644k free,  1826260k cached
> 
> On other system when the CPUs are 100% idle, the load average is 0,00 0,00 0,00

"Load average" is a running average of the number of ready processes,
i.e. those that could do something if they had the cpu. Processes that
are waiting for something to happen, e.g. I/O to complete, can't use the
cpu even if it's idle. Thus it's perfectly possible to have the cpu
doing nothing while the load average is high. It often means you have
some long I/O operation on a slow disk system e.g. copying a DVD to an
external USB device, or multiple downloads waiting for data to arrive
from the net.

poc