[CentOS] Load Average

Sam Drinkard sam at wa4phy.net
Thu Mar 2 04:05:59 UTC 2006


On Wed, 2006-03-01 at 20:49 -0600, Les Mikesell wrote:

> On Wed, 2006-03-01 at 19:18, Chris Mason (Lists) wrote:
> > Sudev Barar wrote:
> > >
> > > No load average is not just CPU but reflects all parameters. For pure
> > > CPU usage system monitor or similar tool will give better
> > > understanding. Also the processes (or dameons) running will really
> > > determine the expected load average.
> > > But as some else said for genera usage 2~3 times x number of
> > > processors is a thumb rule guide.
> > > --
> > >   
> > I don't think so. I believe, but could be wrong, that load average is 
> > the number of processes waiting to execute. Nothing else.
> > However, I reserve the right to be wrong.
> 
> It is supposed to be the number of runnable processes (i.e. not
> waiting on i/o completion) so 1 per processor is busy, higher
> means something is waiting for CPU.  Most programs other than
> graphics and number-crunching tend to wait more for i/o than
> CPU, so a load average of 2-3 (x processors) may not reflect
> noticeable delays.


All of you who have responded have given me good information, and I
appreciate it.  Altho I don't perceive this machine to *have* a load
problem, I was more curious than anything as to what would constitute
heavy or moderate loads.  This evening, while there were processes
active, I did a few tests, one of which was the hdparm -t, and I was
quite shocked to see how low the thruput really was, albeit cached.
Results were like 18mb/sec where as a few other times during a lighter
loading, I/O was what I consider respectable, at 160 +/- mb/ 3 seconds.,
or approximately 54mb/sec.  I also tried a few commands to see what kind
of sluggishness was evident, and about the only thing I could really
tell a big difference in was deleting messages from evolution, and of
all things, logging out.  System was *very* slow to log me out, but was
about normal when I logged back in.  At that time, 7 processes were
running, with a load average according to top of 5.4, with 1.4gb memory
in use, and 700k of swap, but not actively swapping out.  There were a
lot of processes that were swapped out, and only a few as runnable.
Since the machine only has a single 200gb disk, I suspect part of the
sluggishness comes from a bottlenecked disk I/O, just based on so many
processes actually in swap.

Again, thanks for everyone's input, and thoughts.  I have again, learned
a thing or 3!

Regards,

Sam
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