How is system load determined?

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How is system load determined?

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12-07-2001

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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

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12-07-2001

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Found it

system load is the average length of the processor queue.

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12-08-2001

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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.

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12-11-2001

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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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