[mrtg] Re: Load vs CPU

[Gary W. Smith]

If there is something on the CPU thats waiting for outside resources (such as interrupts or I/O) then it's possible to queue up additional requests while the CPU is idle.  CPU is also based on scheduling priorities as well.  If something has a higher priority over something waiting in the queue then the queued item will remain.  The swapping of the context on the DMA controller also takes time, but that's not CPU time.  Things like busmastering will also take burded off of the CPU but then it becomes a bottleneck.  There are just so many reasons why the CPU can be idle while something is waiting in the queue.
 
Hope that helps, 
 
Gary 
________________________________

From: mrtg-bounce at list.ee.ethz.ch on behalf of Brian Steele
Sent: Tue 2/22/2005 2:14 PM
To: 'Corey Goldberg'; mrtg at list.ee.ethz.ch
Subject: [mrtg] Re: Load vs CPU



How is it possible for the CPU to be less than 100% when there are jobs in
the queue?  Shouldn't the OS automatically spawn new processes?

If I have 50% CPU utilization, but a high # of processes waiting, what does
this mean?  Or does it differ from one OS to another.

Brian

-----Original Message-----
From: mrtg-bounce at list.ee.ethz.ch [mailto:mrtg-bounce at list.ee.ethz.ch] On
Behalf Of Corey Goldberg
Sent: Tuesday, February 22, 2005 4:01 PM
To: mrtg at list.ee.ethz.ch
Subject: [mrtg] Re: Load vs CPU

Load is the average number of processes in the CPU's run queue (waiting for
time on the processor), whereas CPU utilization is the percentage of CPU
cycles that are currently utilized for doing work.  Both can be interesting
to watch and can tell you different things about the nature of a system's
processing health

-Corey Goldberg


-----Original Message-----
From: Brian Steele <bsteele at morrisprintinggroup.com>
Sent: Feb 22, 2005 1:54 PM
To: mrtg at list.ee.ethz.ch
Subject: [mrtg] Load vs CPU


Please excuse my ignorance.Can someone explain the difference between
average load and CPU utilization?



Brian



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