Re: [cobalt-developers] CPU Load average - acceptable

[Paul Gillingwater <paul@xxxxxxxxxxx>]

Quoting Andrew Cudzilo <linuxps@xxxxxxxxx>:

> it goes all the way up to .99 (99 percent) but most servers I've seen
> operate in the .10 to .25 range..but thats not including the peak times of 
usage
> 
> > I am wondering what an acceptable load average is on my CPU.  I have a
> > Raq4r and occasionally go and check this information.. usually this
> number 
> > is very low (less then .10).  What does this number max out at?

Actually, this is not a percentage.  Instead, it's an average over a period of 
time of how many processes are sitting in the run queue.  Normally, Linux (and 
other UNIXen) operate a queue for processes that are actively running and a 
queue for processes that are sleeping (usually waiting on a resource like disk, 
LAN or serial I/O.)  Generally, most processes are sleeping.  The eighth column 
of a "ps waux" command under Linux shows the run state for all processes, which 
is usually S (for Sleep), followed by N for low priority processes or W if 
there are no pages from the process in memory.  The few processes that are 
actually busy will show "R" for Run.  

It is quite possible for the load average to exceed 1 (therefore it's not a 
percentage), when there are two or more processes running continuously for over 
5 minutes (e.g., ray tracing.)  I've seen some UNIX systems with load averages 
in excess of 25, however this indicates very heavy load.  There's no hard and 
fast rule about what's healthy for a system, but anything over 1 should be 
investigated, as it can mean buggy software hasn't terminated properly, and is 
running wild.

In the past I have integrated the CPU load average with MRTG (by multiplying it 
by 100), which shows very nicely the long term trends for system usage.

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        Paul Gillingwater
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