Unresponsive Finder? Here's how to speed it up.

After the latest MacOSX update (10.9 aka Mavericks) several users have noticed that the Finder becomes unresponsive for a short while when booting up or waking up from sleep.

This seems to be due to App Nap, that aims to increase battery life by putting idle applications in "sleep" state. 

According to Apple official page "OS X can tell when an app is completely hidden behind other windows. And if that app isn't currently doing something for you — playing music, downloading a file, or checking email, for example — App Nap conserves valuable battery life by slowing the app down. But as soon as you start to use it again, the app instantly shifts back to full speed". 

Though this idea can have its upsides, it can slow down your Mac performance causing a lag when you click an application icon.

 

App Nap can't be disabled on a system level, but there are two methods to customize the way it works:

1. From the Get Info menu of a specific application: If you select an application and press down CMD and I at the same time on your keyboard or you right-click the application, you'll be shown the Get Info menu. From there, you can select Prevent App Nap to use that application always at full power.
2. Using Terminal: The previous method doesn't work for all your apps because some of them, considered critical by Apple, don't have the Prevent App Nap option in their Get Info menu. For these specific applications, we need to perform a Terminal hack (I know you're already cringing but I promise you it won't be a biggie). Open Terminal (Applications/Utilities/Terminal or look for "Terminal" in Spotlight) and enter the following command: sudo defaults write <app domain name> NSAppSleepDisabled -bool YES (if you want to revert this change, simply replace YES with NO). <app domain name> must be replaced with the application name, which is in this form: com.companyname.appname (e.g. for the Finder it's com.apple.Finder). This will prevent App Nap for that specific application for the current session. Consider that you'll need administrative privileges to run this command (that's why you need sudo, that will temporarily grant you administrative rights) and you'll have to enter your administrator password to run it. Heads up: when you enter the password, you won't be shown anything but don't worry because it's alright, your password isn't displayed for security reasons (same as Linux, under this point of view)

Wrap-up

Apple has introduced several new functionalities with Mavericks, one of which is App Nap (for more details, see my previous post MacOsX Mavericks: free upgrade, no revolution (part 3) ). 

This new feature tends to improve the battery life of your Mac but may cause slowdowns and lags when waking your Mac from sleep or booting it up. 

Though it can't be disabled on a system level, you can customize the way it works for specific applications both by right-clicking them and by performing a Terminal hack.

I recommend to perform a backup with Time Machine before applying the above described changes and to utilize Terminal only if you're an experienced user.

Consider that the more applications you use at full power, the slighter your available RAM will be, so you should use the above methods only for the most important applications necessary for you to get your job done.