[plug] Load (overloading...)

[Peter F Bradshaw]

Hi;

On Tue, 21 Sep 2004, Tim White wrote:

> Being the bored Year 12 student that I am I decided to see how much
> impact a couple of hundred, cpu intensive, processes would do. While
> playing around I noticed that the load meter on my gnome bar was getting
> higher than I had ever seen. It actually got to 100% but that seems to
> be a lie. As further testing revealed some staggering load numbers.
> After being used to a load of .6 to 2.5 I thought that I must be around
> 5 or something. Not so according to /proc/loadavg and uptime. So after
> writing a few scripts that would allow me to continually spawn processor
> intensive processes simulatenously, and monitor the load, number of
> these particular process, etc... and a 'relief valve' so that I could
> return my system to its current 0.65 loadavg, I discovered to my horror
> that I could load the system way beyond my expectations.
> So what exactly is load? Well I orginately thought it was a percentage
> similar to CPU usage but I'm not to sure anymore.
> What is the maximum load? That I also do not know.
> During my testing the loadavg got to 232.64, with 234 CPU intensive
> processes. From this I could infer that the loadavg is the # of active
> processes. Would I be correct?

More exactly it is the smoothed number of processes in the "run queue"
at any one time. That is it is the number of processes that are not
blocked by I/O or swap or otherwise suspended. For compute intensive
operations the number of processes is the load if sufficient RAM is
avaliable.

One interpretation is that load is the number of "virtual CPUs" in use.

> Just looking for some enlightenment and showing off what my 667Mhz P3
> can do[1].
> BTW, I was very impressed with the way linux handeled the system under
> such high load. I could still use terminals fine (X was a little bit
> touch but still running) the slowest part was actually starting the
> screen session at login (due to my .bashrc automatically opening a
> screen session)

Wait until you have a situation where you have high load and massive
over commitment of RAM (i.e. lots of swapping)!

>
> Tim
> [1] I had seen people talking about servers with high loads and the
> numbers where VERY small compared to mine
>
>

Cheers

-- 
Peter F Bradshaw, pfb at users.sourceforge.net, ICQ 75431157 (exadios).
PGP public key at http://exadios.d2.net.au/public_key.html
"I love truth, and the way the government still uses it occasionally
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