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Simple really

Have a linux server - 4 processes are running at or in excess of 100% cpu usage.

What exactly does this mean? I assumed nothing could go beyond 100% :)

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up vote 11 down vote accepted

Is it a multi core machine? My laptop is a dual core, and I can get top to show 100% for 2 processes.

From my understanding, top will give you 100% per processor/core.

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Yes, if you have 4 cores and you max it out, you'll be using 400% CPU :) –  Xorlev Mar 28 '10 at 15:08
    
Thanks, its multi core :) –  steve Mar 28 '10 at 20:39
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Different versions of top display CPU usage differently. Assuming your referring to individual process line items, top is displaying cumulative CPU usage for that process and all child threads. IE if a process has two child threads running, one using 50% of CPU 0 and the other thread using 75% of CPU 1, top will report CPU usage for the process at 125%.

These threads can be displayed by running top with an -H or in PS with the -m option.

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Utilization is in reference to a processor. Single threaded processes can not exceed 100%. However, if top can report some samples as over 100%. Multi-threaded processes should be able to exceed 100% given multiple processors.

It would appear you have a lot of CPU bound processes. This is normal for some processes such as the Seti program. Interactive processes normally don't use much CPU.

Based on your report you must have at least 4 processors.

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