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Old 11-04-2010, 12:52 PM   #1
bujecas
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Load Average Normalized


Hello,

I have some doubts about the way that load is calculated in some UNIX flavours. Linux says that load average is not normalized, this means if I have a 2 CPU machine and a load of 1, the CPU is loaded 50% of the time. On the other hand, I think in HP-UX the load average is normalized. In AIX I couldn't get if is normalized or isn't.

Could anyone give me a explanation if the load is normalized or not in each system (AIX, HP-UX, Linux, Tru64, Solaris)?

Thanks.

Last edited by bujecas; 11-04-2010 at 01:12 PM.
 
Old 11-04-2010, 05:34 PM   #2
jlliagre
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Never heard of normalized load averages. Are you sure HP-UX reports non standard values ?
In any case, Solaris reports a value that isn't affected by the number of CPUs.

By the way, the load average isn't computed from CPU usage but from the runnable processes count at sample intervals.
 
Old 11-04-2010, 07:44 PM   #3
syg00
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Quote:
Originally Posted by bujecas View Post
Linux says that load average is not normalized, this means if I have a 2 CPU machine and a load of 1, the CPU is loaded 50% of the time.
Hmmmm ... and what if the loadavg is 4 (or 20 ...) on a 2 CPU machine ?.
Have a read of this - it has some errors, but will give a good idea of what the numbers actually represent.

jlliagre's definition is for traditional *nix - Linux includes tasks in uninterruptible sleep as well. The calculations of the moving average is similar for all though.
 
Old 11-10-2010, 06:06 AM   #4
bujecas
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I've found on http://www.loudermilk.org/software/solaris-hpux.html that load average calculation in HP-UX is normalized:

Load average calculations are different. In HP-UX, unlike Solaris, Linux, or just about any other UNIX, load averages reported by uptime are divided by the number of processors in the system, so that a load average of 1.0 means the system has as many processes in the run queue as it has processors. That's all well and good, and it might even be a better approach than the other vendors, but once again HP-UX breaks with tradition and confuses administrators of other platforms.
 
Old 11-10-2010, 06:32 AM   #5
jlliagre
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That's curious. HP-UX 11i v3 uptime manual page doesn't mention that normalization but is describing the usual Unix way (average number of jobs in the run queue).
http://h20000.www2.hp.com/bc/docs/su.../c02272185.pdf
 
Old 11-13-2010, 08:45 PM   #6
AlucardZero
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Quote:
Originally Posted by bujecas View Post
I've found on http://www.loudermilk.org/software/solaris-hpux.html that load average calculation in HP-UX is normalized:
HPUX 11.11? Solaris 8? How old is this web site? Both of those are from the prehistoric era, and half of his complaints are now resolved. I'd bet the load average changed too (I have HPUXes at work, but I'm not at work to check =)
 
  


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