What’s the best troubleshooting tool you already own but have probably never used? Activity Monitor, a utility tucked away in OS X’s /Applications/Utilities folder. Most users can ignore its geekier features and focus on its straightforward ability to resolve mysterious freezes, open unopenable applications, and diagnose performance slowdowns.
If you’ve ever had an application freeze—and who hasn’t?—you probably know about the Force Quit command (Apple: Force Quit or Command-option-escape). It brings up a window from which you can shut down even frozen-solid programs. What you may not know is that many programs (technically referred to as
) aren’t listed here, even though they’re running.
For instance, the Dock has no Quit command, and it doesn’t even appear in the Force Quit window’s list of active programs. If the Dock won’t budge, here’s how you can get its motor running again:
Launch Activity Monitor and select My Processes from the pop-up menu at the top of the main window.
Look for the Dock in the Process Name column. To find it quickly, type
in the toolbar’s Filter field. Select the Dock item.
Click on Quit Process at the top of the window.
In the dialog box that appears, click on Force Quit. The Dock should briefly vanish from your screen; when it reappears, it should work as usual.
“In Use” Documents
Activity Monitor can also help when you can’t delete a document because your Mac claims that it’s in use. This means the document is linked to a currently running process, typically the application used to open it.
To delete the document, you first need to quit the application. But what if the app isn’t listed in the Dock or anywhere else you’d normally look? Turn to Activity Monitor for help.
For example, Microsoft Entourage uses database files to store your e-mail messages (the files can be found in /
your user folder
/Documents/Microsoft User Data). Normally, you wouldn’t want to delete these; if you did, you’d lose
your e-mail. However, if you have two Macs, you may want to delete the files on one Mac and replace them with the newer files on the other Mac. This is the case for me whenever I go on a trip; I want to transfer the latest versions of the files on my desktop Mac to my PowerBook. That way, I start the trip with all my latest e-mail messages and appointments at hand.
The problem is that Microsoft Office’s Data-base Daemon constantly uses these files. This hidden process allows appointment reminders to pop up on your screen even when Entourage isn’t running. The solution is to use Activity Monitor to locate the process and quit it
you try to delete the files. After replacing the deleted files with updated ones, relaunch the Microsoft Database Daemon. It’s located in /Applications/Microsoft Office/Office.
Quit Applications That Other Users Opened
The Fast User Switching feature in Panther (under Login Options in the Accounts preference pane) is a fantastic time-saver. It lets an additional user log in to an account without making other users log out. That’s as handy for a computer lab as it is for a home computer on which every family member has an account. The problem is that some applications work only for one account at a time.
Say a user with another account has iDVD running. If you want to launch iDVD, the other user must quit the application. But what if he or she isn’t around? If you’re the Mac’s administrator, you can use Activity Monitor to manage this:
From the pop-up menu in Activity Monitor’s main window, select Other User Processes.
Locate iDVD in the list and select it.
From the toolbar, click on Quit Process; then click on the Quit button.
Enter your administrator password when asked. You can now go ahead and relaunch iDVD using your own account.
Check for CPU Drain
Your Mac’s performance has gradually slowed to a crawl. When you type a letter in your word processor, it takes several seconds for the character to appear on screen. True, restarting or quitting all open applications would probably solve this problem. But if you’d rather avoid that hassle, give Activity Monitor a try:
From Activity Monitor’s main window, select My Processes from the pop-up menu.
Click on the % CPU column header—this reorganizes the list to show you what’s taxing your Mac’s CPU the most. Make sure the triangle next to the column header points downward. If it doesn’t, click on the header again.
All of your open processes will appear in descending order—that is, the ones using the greatest percentage of your CPU’s power start the list.
In general, most processes will stay under 20 percent—often well under, although they may briefly spike higher. If one application shows a consistently higher percentage, especially if it’s much higher, it’s the likely cause of your Mac’s slowdown.
Note: Activity Monitor itself can significantly drain the CPU, mainly because it scans your Mac every two seconds. You can calm it down by shifting this value to every five seconds (go to Monitor: Update Frequency).
If you find a culprit application, quit it.
The last time I had this problem, I found that Safari’s % CPU was over 90 percent. I quit Safari, and my Mac’s performance returned to normal. Whatever the cause, it was a temporary glitch. When I relaunched Safari, the slowdown did not return. Perhaps a Web page had triggered the CPU drain.
Check for a Memory Leak
If CPU usage does not reveal why your Mac is traveling at bumper-to-bumper speed, your system may have run out of memory. If this happens frequently, either you need to open fewer applications at a time, or you need more RAM. But occasionally the problem is due to an application bug that causes a memory leak. In other words, the application uses a steadily increasing amount of memory over time—until there is no memory left for anything else. Check for leaks this way:
In Activity Monitor’s main window, select My Processes from the pop-up menu.
Click on the Real Memory column header. Make sure the triangle next to it points downward. If it doesn’t, click on the header again.
All your open processes will appear in descending order, with the ones using the greatest amount of your memory at the top of the list.
Activity Monitor updates these values every few seconds, so watch for a process’s memory value that’s heading skyward. That process is your leak.
If you find a culprit, quit it. If you don’t, check again, this time looking at the adjacent Virtual Memory column.
If your Mac returns to normal speed, you may still be able to use the application. With some luck, the leak may not recur—but if it does, contact the app’s developer to report the bug.
Activity Monitor can be a powerful ally in your quest to keep your Mac running smoothly and at top speed. The next time you run into a problem you can’t figure out, pull out Activity Monitor and try some of these tricks.
Live Mac Stats
Want a convenient way to check how your Mac divides memory between what’s currently in use and what’s still available? Or how about a continually updated timeline of your Mac’s CPU usage? To see these and other graphs in living color, simply select the appropriate tab (CPU, System Memory, and so on) from the row of tabs at the bottom of the Activity Monitor window.
But you don’t have to limit yourself to the main window. You can view graphs in separate floating windows and more. For example, choose Monitor: Show Floating CPU Window: Show Vertically to see a bar, updated in real time, tucked on the left side of your screen. My favorite is the Monitor: Dock Icon option. Use this to put the performance graph of your choice in the Dock so you can monitor your Mac all day long.
Quit with Care
In these examples, I generally recommended selecting My Processes from Activity Monitor’s pop-up menu. Why not select All Processes instead? If you do, Activity Monitor includes administrative processes in the list. Quitting these processes can cause unstable behavior (also known as system crashes). Unless you’re confident in your knowledge of what is safe to quit and what isn’t, don’t mess with administrative processes.
Contributing Editor Ted Landau is the author of
Mac OS X Help Line
(Peachpit Press, 2004) and the director of support services for
Doctor Mac Direct.]
Do you suspect that a rotten application is slowing down your Mac? Watch Activity Monitor’s list of all open applications in descending order of memory usage. The pie chart shows you how much memory is in use and how much is free.