How to understand Activity Monitor CPU usage

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Level 1

9 points

How to understand Activity Monitor CPU usage

Can someone give me an idiots guide to understanding CPU usage in Activity Monitor? I would like to better understand what the numbers indicate (ie what's good, bad etc) and how to make sense of them. My goal is to better understand my computers performance. I have a new i5 and sometimes feel like it isn't as nimble as it should be. What is the best way to determine how efficient my system is? For example, I am running Handbrake right now (and nothing else) and my CPU is at 97% user (Handbrake says 369%-- I didn't know it could be over 100%!). Is this normal? Will the computer always through everything it has at whatever I am running? Obviously I don't understand the big picture. Am I really saturating my cuadcore with one program? Or maybe I want to be...

Thanks for any insight.

imac i5, Mac OS X (10.6.2)

Posted on Feb 27, 2010 4:08 PM

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Answer 1

Russa

Level 4

1,343 points

Feb 27, 2010 4:38 PM in response to nicholaspe

Hmm. Here's a "non-engineers reply" to start the thread.. % User is the number referencing your application execution. % System is the number referencing Mac O/S activities like memory/disk swaping. % Idle is self evident.

Performance is based on CPU speed, memory usage, and disk usage. For instance, you could be burning a lot of CPU cycles on system management if an application uses up a lot of your physical memory and/or your disk is at capacity i.e. about 80%.

So when you run an application and high CPU usage rates, check your disk and memory usage. If your CPU utilization is high, and your memory utilization is about 80% you probably need more memory. There's not much you can do about CPU cycle usage.

Can't answer too much about Handbrake but is it the latest version? A older version might not be able to use the quad core or the 64bit processor therefore affecting CPU efficiency and performance.

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Answer 2

etresoft

Level 9

57,002 points

Feb 27, 2010 4:37 PM in response to nicholaspe

You aren't going to get any sort of "nimbleness" when running programs that soak up all four cores on that machine. "Nimble" implies doing many things and being very responsive while doing it. You can't do that and have maximum throughput on video encoding. Something has got to give.

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Answer 3

Feb 27, 2010 6:01 PM in response to nicholaspe

And since the other answers don't say it explicitly, the "%" figure refers to one CPU core. You have 4 cores in your i5 system, so you have up to "400%" of CPU. If I'm running nothing else, I'd prefer that a process is using as much of the CPU as possible, so as to be complete sooner.

Matt

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Answer 4

roam

Level 6

13,637 points

Feb 27, 2010 4:53 PM in response to nicholaspe

Here is a brief outline from Apple on Activity Monitor.
http://support.apple.com/kb/HT1342?viewlocale=en_US

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