Re: {bb} Definition of CPU load...

[David A Smith <dasb@eci-esyst.com>]

On Mon, 25 Oct 1999, Steve Neuharth wrote:

>         What is the definition of "LOAD=xx" on the CPU.html pages... is
> it a percentage or the percentage x100?

To elaborate on Sean's answer.  The 5 minute load average is, for a
uniprocessor system, the average number of processes in the run queue over 
the last 5 minutes.  It does not, generally, count processes that are
blocked waiting for resources other than the CPU however in some cases you
can get a large spike in load average from a NFS server going down that
the machine depends on.

For a multiprocessor system it gets a bit more complicated.  In my
experence Sun systems (SunOS and Solaris) use the sum of the wait queue on
each CPU (as if there was just one queue feeding into all the processors)
while HPUX uses the average of the average of all the CPUs (so a busy
system with an average of 4 processes waiting for each of 2 CPUs would,
under SunOS/Solaris have a load average of 8 while on a HPUX system have a
load average of 4).

Oh, and high CPU load does not always mean that your CPU is at 100% all
the time.  It is not to odd to see a load average of 2-3 with a average
CPU utlization of 50% or less because of lack of resources other then CPU
cycles. 

Anyone know the way any other systems work, I haven't worked with any
others enough to know offhand how they decide load on a multiuser system.



-- 
David A. Smith          dasb@eci.esys.com
Contract Systems Administrator
at Raytheon Systems, St. Petersburg, FL
727-302-3202            727-302-3408 fax


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