Time to lock desktop

When I lock my desktop (via SuperL shortcut) it takes 2-3 seconds before it happens. I don't whether it is due to the speed of my pc, but it looks more like a animation that's be playing first.

Can I change some setting to remove the animation?

SuperL shortcut calls Unity's built-in shortcut, which uses Unity's lock-screen (technically, it's unity-panel-service process in lockscreen mode, but that's a formality), which does use animation, and might be slower.

The alternative way, dm-tool allows you to lock the screen or switch-to-greeter (which is basically goes back to the screen that you see when you sign in). This method is slightly faster, since it involves your login screen, rather than Unity's tools. You can bind the shortcut to use dm-tool switch-to-greeter or dm-tool lock instead.

The shortcut is set within a specific compiz schema. There's two ways to go around disabling it. One, is via command-line:

dconf write /org/compiz/profiles/unity/plugins/unityshell/lock-screen "'Disabled'"

Another way is via compizconfig-settings-manager (which if you don't have installed, install via sudo apt-get install compizconfig-settings-manager). The shortcut is set under Unity Plugin -> General tab.

Once you have that done, you can go into System Settings -> Keyboard -> Shortcuts -> Custom , and create a new keybinding for SuperL with dm-tool switch-to-greeter as command.