I'm thinking about upgrading my RAM from 1GB to 2 or 4 GB. I would like to have some idea as to whether buying more RAM would be worth the expense. How can I know whether I will see better performance after upgrading RAM?
Are you spending a lot of time waiting for data to be loaded or written to the hard disk? RAM helps with that. It doesn't make computations faster, it reduces the time the computer pauses between computations because it can't get at the data fast enough.
If you want to rely on more objective measurements, open your usual applications and work normally for a bit. Then open a terminal and run the command free -m. You'll see output like this:
total used free shared buffers cached
Mem: 3965 3618 346 0 157 276
-/+ buffers/cache: 3184 780
Swap: 16383 774 15609
or
total used free shared buffers cached
Mem: 1851 1798 52 0 338 489
-/+ buffers/cache: 971 879
Swap: 15257 11 15245
Look at the values on the line with -/+ buffers/cache. The one in the “used” column tells you how much of your memory is used for applications proper. The second one tells you how much memory is used to store data that is also on the disk (cache and buffers). On a healthy desktop system where you use multiple applications (say, a web browser and a word processor and a music player and a couple more), the cache and buffers should represent about half the total memory, i.e. the two values on the -/+ buffers/cache line should be roughly the same. This is a crude approximation: 60%/40% is just fine, 80%/20% says you could use RAM. The first system above could use more RAM, the second one is fine.
