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How is system load determined?


 
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# 1  
Old 12-07-2001
How is system load determined?

Hello!

I'm wondering what factors are used to determine the "system load"

Where can i look to get more information on this?

Patrick
# 2  
Old 12-07-2001
Found it

system load is the average length of the processor queue.
# 3  
Old 12-08-2001
Re: Found it

Quote:
Originally posted by Patrick_Morris
system load is the average length of the processor queue.
I would be interested to know where you found that particular language. The man page for uptime says
Quote:
the average number of jobs in the run queue
which is very close to your language. I encountered many cases where this didn't seem to jibe with reality so I took a peek at the source code.

Rather than looking at the run queue, the load is actually computed by scanning the proc table. A process is counted if
  • it is runnable (in the run queue)
  • if it is running (in a cpu)
  • if it sleeping with a priority lower than PZERO

That last one is intended to cover processes that are waiting for disk i/o to complete. And the load is divided by the number of cpu's.
# 4  
Old 12-11-2001
Quote:
System Load Average (SLA). It is important to note that the SLA can only be used as a rough indicator as it does not take scheduling priority into account . It also counts as runnable all jobs waiting for disk I/O, including NFS I/O. However, uptime is a good place to start when trying to determine whether a bottleneck is CPU or I/O based.
The extract above is from this paper..... CLICK HERE.

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