It is taking a long time because all the logs stored on the Android device are re-fetched each time debugging begins. In order to not interfere with other logcat showing tools, the logcat window is made not to delete the logs from the device when they are fetched. Thus if the Android device has been running a long time, the logs have been accumulating as well.
Currently there are two ways to solve the slowness:
1) Display the logcat all the time for the debug Android device. Then the messages are updated constantly and the messages won’t be re-fetched when debugging begins. To display the logcat between debugging sessions go to ‘Android->View LogCat’.
2) Clear the logcat on the Android device manually. For this go to ‘Android->Open Android shell’ and enter the command ‘logcat -c’ there. Please not that this will irreversibly delete all the stored logcat messages from the device.