Inexplicable slow-down? Check for hanging processes

Thursday, January 24th

As we've noted a number of times, checking Activity Monitor (located in /Applications/Utilities) for stalled, processor hogging or otherwise unruly processes can be a great routine for eliminating inexplicable system slow-down (see our tutorial for information on using Activity Monitor to this end). Essentially, you're looking for processes that are displayed in red, or that are using large swaths of processor time though they aren't performing any activities.

Such an inspection recently proved fruitful for Birgit Zeiter, who discovered that the SystemUIServer process was hung.

"We just had an MacBook Pro 2.16 GHz Intel Core2 duo with 1GB Ram, System 10.4.11, with a hanging SystemUIServer."

The hung SystemUIServer was causing general system slow-down and lack of responsiveness.

Once the problematic process had been targeted, Zeiter knew where to look:

"Deleting ~/Library/Preferences/com.apple.systemuiserver.plist logging out and in again solved the problem, all menu icons in place again, the machine works fast."

But what if you're not sure where to look? The ~/Library/Preferences/ folder is a good place to start. Look for files that math or closely resemble the name of errant processes and temporarily remove them from the folder, then restart and check for alleviation of the problem. Sometimes you'll need to wait and see if the process will hang again after routine operation (it might not falter immediately after a restart).

Other good places to look for culprits include plug-in directories. For instance, a number of users have found the process UserEventAgent hanging or exhibiting inordinately high processor usage. This process is used to handle interaction with various device drivers, and as such, is prone to hangs, spikes in processor usage and other issues caused by potentially faulty devices or device drivers. In some cases, just quitting this process (using Activity Monitor) does the trick, eliminating slow-down on a semi-permanent basis. In other cases, actual drivers must be removed. A number of users have fingered audio-related plug-ins, such as those located in:

• /Library/Audio/Plug ins/

Errant devices can also be to blame, especially if you see processes like usbmuxd hanging. Try disconnecting the devices tempoararily, forcing the aforementioned process to quit with Activity Monitor, or deleting kernel-related caches as described in this tutorial.

Feedback? Late-breakers@macfixit.com.

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