Recently the menus for fast user switching and the menu bar clock have been malfunctioning on on my PowerMac at work: I would get the spinning beach ball whenever I’d move the mouse over them. It seemed very odd to me to have just a few menus lock up. I fired up terminal, and opened top, which is the command-line version of Activity Monitor. Top has several columns and lots of information to offer, but I’m going to focus on just two of them here: PID and %CPU.
PID is the process ID number. The PIDs start at 1, and each time a new process is spawned it’s assigned a new number. On my machine right now, the PID for a process called SystemUIServer is 319. SystemUIServer controls the menu bar clock, among other things. The CPU column shows what percentage of your processor is being used by which process.
Once in top I noticed that SystemUIServer was taking up nearly all the resources my dual processor G5 had to offer—160. On dual processor and dual core machines, the processing capacity is 200%; for quad models like the Mac Pro, Intel Xserve, and PowerMac G5 Quad, the capacity is 400%.
So…knowing the process to blame and its PID number, I then used kill, a command to immediately terminate problematic processes—similar to the Finder’s Force Quit command. The syntax is as follows:
sudo kill 319
where sudo gives you temporary “super user” privileges, kill forces the process to quit, and 319 is the PID.
Extending this a bit further, if you find your computer oddly frozen, fire up terminal, type top, hit return, and see if any one process is taking up lots of processing power under the %CPU column.
You could, of course, do all this in Activity Monitor, but somehow doing it in the Terminal makes me feel geekier. Sometimes that’s a good thing.