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I'm evaluating performance of a software on a server. To do that I'm watching at Top command output. Anyway sometimes the process exceed the 100% cpu usage. How this is possible? What means 120% cpu usage for example?!?

Akinn
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    Better use tools like sar (sysstat) or pcp (Performance CoPilot) for such a purpose. It'll provide you with statistics for defined period of time so you can better compare your software performance. – Jaroslav Kucera Sep 15 '17 at 11:18
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    Just hit key "1" while running top and you'll see your cores seperately. Toggle between the two views hitting "1" again. – TomTomTom Sep 15 '17 at 11:39
  • This does not directly answer your question but `htop` is a much better package to see pretty much the same information. It includes a breakdown by cpu core/thread – Eric Sep 16 '17 at 09:07

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In top, 100% essentially means that the software is using one processor core full time (or n cores for 1/n of the time each).

So what top is telling you is that your process is multithreaded and uses more than one CPU core at the same time. Note that this number doesn't tell you anything about how the CPU time the process uses is distributed over each core. It could mean two cores and 60% each or 24 cores and 5% each (depending on your hardware, of course).

Sven
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  • On a macbook dual core I obtain values also of 230%. What does it means? – Akinn Sep 15 '17 at 16:17
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    As other said - just hit "1" on the keyboard while Top is running to see how many CPUs the OS sees , dual core is just a name - physical dual core can be seen as 4 logical cores by OS. – Yuri Sep 16 '17 at 10:02