[wellylug] Load average statistics dubious

[Daniel Pittman]

Bruce Hoult <bruce at hoult.org> writes:
> On Tue, Mar 30, 2010 at 12:29 PM, C.T.F. Jansen
> <frank.jansen at actrix.gen.nz> wrote:
>
>> I used to use a number of different unix OS's and the load average
>> statistics on them is an artificial number and often with values too
>> different with what is actually happening on the system. It was regarded as
>> a joke and people warned not to use it.
>
> I don't understand. Load average has a very specific definition -- the
> number of processes in runnable (including actually running) state.

It is worth noting that this may, or may not, include processes blocked
waiting on I/O.  On some platforms like Linux this has even changed over time,
since they now report with, but used to report without.

> It aims to tell you how busy the CPUs are and whether you could potentially
> faster ones, or more of them.

It can also be quite confusing when someone is faced with an SMP machine: if
you have four cores, do you want a load average of 1, or of 4?

        Daniel

That is also a trick question, since the answer is probably higher than either.
-- 
✣ Daniel Pittman            ✉ daniel at rimspace.net            ☎ +61 401 155 707
               ♽ made with 100 percent post-consumer electrons