Hello, I've had an early 2011 15'' MBP for almost 2 years now, and it has become noticably slower. The obvious solution is to increase the RAM. However, when I go to activity monitor, whilst it states at times that 3.99GB out of 4GB are in use, the 'memory pressure' remains green and doesn't appear to be very high. What exactly is memory pressure, and do these results indicate that a RAM increase would speed up my computer - I don't want to waste money on more RAM if it wouldn't have any real effect! Thankyou!