Some tips about CPU utilization

[mikejuni]

I am primary a Unix guy.
I use Mac OS X every day.
I'd like to talk about some tips on CPU utilization.

Sometimes I heard other guys complaining about an application's CPU utilization is too high. I think there is some mis-understanding on that.

An application with a quite high CPU utilization does not nessessary means that it will hog up the CPU and don't let any other programs to work. The application just needs more CPU power when it needed. It is up to the OS (Mac OS X)'s scheduler to let the application to use more CPU power. If you set the priority of the app (using renice) to a higher priority, then it will definity hop up some of the CPU power if its utilization is already high.

But if the priority of the app is low and there are some critical tasks working with higher priority, the app will slow down no matter how high its normal CPU utilization is while the critical task will still perform up to its speed.

For example, many people says that Mozilla uses almost 90% CPU utilization. But if you are playing iTunes together with Mozilla, Mac OS X should not skip because Mozilla will just be slowed down a little bit by the OS and let iTunes to play smoothly.

So there is really no need to worry about CPU utilization, unless it is always 100%. If you want to look at the overall speed of the OS, use "uptime" and look at the load average.

Any other opinion on this topic?

 

[SCrossman]

There is a very noticeable degradation in other application's performance when Netscape 6.x is running in the background and you simply click and hold the mouse down. It still is using too much CPU time for being in the background.

 

[mikejuni]

Yes, there will be performance degrade if Mozilla is doing something in the background. But my point is that users should not be too worried about CPU utilization unless their CPU is always 100% being used by processes.

 

[ulrik]

that's what often happens with bad optimized apps. I had a simple app which showed me the free disk space of all my HDDs in a simple window. I used this all the time. When I first installed Cinema 4D and rendered something, I checked the top output and was surprised that Cinema 4D only had 60% and this freaking app 35% off my CPU...all the time, even when Cinema 4D should have gotten at least 90% for rendering. I killed the app and Cinema 4D went up to around 96%. I would never care about CPU times when nothing is going on, but as soon as an app does something complex, filters, rendering etc., other apps which shouldn't do much should also decrease their CPU utilization.