Re: [exim] Very weird e-mail problems

On 02/12/2006 16:41, Stanislaw Halik wrote:
> Machines running lots of processes being low on CPU often have higher
> loadavg than a machine that runs one process all the time, without
> sleeping in syscalls.

Heh. I was a server administrator of a large web server machine which
usually ran at a load average of 5-10. After a smallish change was made
to the page templates being used, the load average went over 200, and
the customer freaked out even though pages were being served just fine.
It turned out that the new templates were slightly larger than the
previous ones, meaning that web requests were slightly larger than the
TCP/IP sending buffers, meaning that each page now took 2 bites to serve
instead of one, and there were always lots of httpd processes waiting to
run. Despite the loadavg of over 200, the machine was not heavily
loaded, in that there was spare CPU, memory, disk and network I/O bandwidth.

In summary: the loadavg often isn't a useful indication of how busy a
machine is.