On Wednesday 07 May 2003 11:09 am, Dan Egli wrote:
: Tony Finch wrote:
: >Nico Erfurth <masta@???> wrote:
: >>On 3 May 2003, Tony Earnshaw wrote:
: >>>But in what /units/ is "load"?
: >>
: >>IIRC it's "How many processes fight for CPU-ressources".
: >
: >Many systems also count processes that are waiting for disk
: > towards the load average.
:
: I don't know on other O.S.'s but on Linux, a unit in the load
: average is the "Average number of processes that are waiting
: for access to the CPU". It's sampled in (if memory serves) 15
: second increments, and then averaged across one, five, and
: twenty minutes.
:
I can't speak to the general sampling frequency, but the running averages
are pretty general amoung unixen.
A better question for this, is what to set it at? Every machine config is
different, but in general there is a point where the machine is spending more
time moving from process to process than it is actually doing any useful work.
When it gets near this point, there is a noticable lag in response.
With increasing power of processors, and the availability of cheap memory,
the term load average is getting less significant.
Vague recollections of the Bad Olde Dayes:
It used to be that a PC
running linux was spritely in response inthe X windows at load levels below 2,
and sucked golfballs through a wet straw at load levels of 8.
Something that was a server only didn't require patience on the part of the
operator, so load levels of 15 were commonly used as the cut off for
further connections.
Unless you have a very fat pipe, or have reserected an ancient 486 SX
to use as your email server, you are far more likely to be limited by the bandwidth
of your pipe to the world. The next may be the amount of memory to keep
track of connections, buffer them, and do the packet reassembly.
CPU usage is unlikely to ever be a problem for most of us peasants.
If you want to set this, track the size of the cpu load (runqueue) for a few days
of normal usage, then set the reserve at a few times this number. This
will prevent denial of service attacks, but still leave room for extraoridinarly
bursts of traffic.
JMHO.
--
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St. John's School of Alberta RR - 5 Stony Plain, Alberta TZ7 1X5
Alternate address sgbotsford@yahoo . com
