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real · May 30, 2006, 10:52 PM

I was doing some exporting out of quicktime,

Things where running slow, and I wanted to see how much resources where being used.

I went to the activity monitor and noticed 70-90% Nice in the cpu useage. and only 10 and the remaining resources.

What is that. I think im missing something, but not really sure.

Thanks

real

macintologist · May 31, 2006, 12:17 AM

Nice is what allows apps to prioritize their CPU usage. If 90% of the CPU is Nice that means that it is using that CPU power to encode the video, however if another app wanted it, Quicktime gets last priority, which means it doesn't hog your processor and you can use the computer normally while encoding video in the background.

real · May 31, 2006, 10:31 AM

thanks thats what I thought but wanted to be sure

real

Millennium · May 31, 2006, 12:02 PM

CPU utilization isn't really a good measure of how loaded your computer is. The reason for this is that as macintologist said, many apps will try and take as much CPU as they can if it's available, but will happily yield it to higher-priority apps if the need arises.

However, there's another way to measure system load which works well. The Activity Monitor doesn't show it, which is unfortunate, but you can get it by opening the Terminal and typing top -d (plain top also works, but it needs more CPU time, which can skew the results).

You'll be presented with a while bunch of information, but what you're really interested in is up near the top left forner: the "Load Avg" statistic. You'll find three numbers there: the average load for the last minute, the last five minutes, and the last fifteen minutes. Most of the time, the first of these numbers is what you're really interested in.

This number isn't a percentage. Roughly speaking, it's the length of the process queue: in other words, how many apps had to wait in line while another app was taking up resources. Ideally, you want this number to be as low as possible. As long as it's less than a certain threshold, then even if the CPU is at 100% you're still fine: all of your apps are getting all the CPU time they need. If the load average is higher than that threshold, especially if it stays above it for a long time, then your system is doing more than it can really handle, and things will start slowing down.

So, how do you determine the threshold? Just count the number of processor cores in your machine. Most systems have one core, but dual-chip and dual-core systems have two. The Quad-Core G5 (two processors, each with two cores) has four cores. However many cores you have, that's the threshold you want to keep your system under.

Unfortunately, I don't know of any GUI apps that keep track of this number right now. The only way to get at it is through top in the Terminal. If someone knows of a good GUI solution for this, I'd love to hear about it.

TETENAL · May 31, 2006, 12:17 PM

Originally Posted by macintologist

Nice is what allows apps to prioritize their CPU usage. If 90% of the CPU is Nice that means that it is using that CPU power to encode the video, however if another app wanted it, Quicktime gets last priority, which means it doesn't hog your processor and you can use the computer normally while encoding video in the background.

I don't think that is correct. First, the process should be called "nice" then and not "Nice", second, I tried exporting something with QuickTime and there was no process called like this.

seanc · May 31, 2006, 12:37 PM

TETENAL · May 31, 2006, 12:53 PM

Sorry, I though he was talking about a process. I take back everything that I said.

Big Mac · Jun 2, 2006, 07:58 AM

Originally Posted by Millennium

You'll be presented with a while bunch of information, but what you're really interested in is up near the top left forner: the "Load Avg" statistic. . . .

Thank you for the information, Millennium.

dreamryche · Jun 7, 2006, 01:01 AM

iStat Pro tracks load avg. amongst a bunch of other things.

real · Jun 7, 2006, 02:20 PM

let me know if I am not understanding this.

When I was doing the encoding in quicktime Nice was useing 70 -90% of the cpu, and the User was useing 10% or so. So the reading of the CPU used by the quicktime is 70 -90% but if say safari wanted some cycles QT gives them up. WOW I think I confused myself,

Nice is the Same as User % but will be given up if need be.

real

SSharon · Jun 7, 2006, 03:16 PM

Originally Posted by Millennium

snip...
Unfortunately, I don't know of any GUI apps that keep track of this number right now. The only way to get at it is through top in the Terminal. If someone knows of a good GUI solution for this, I'd love to hear about it.

MenuMeters will display this info if you click on the processor usage in the menu bar. I use it all the time for this.