Inactive memory is a good thing. People should stop worrying about it. You can even consider it as free memory.
If you've been using an app, when quitting it all of its memory isn't cleared unless the app states so. This memory stays inactive so if you run the app again it's immediately available.
Also, there are several things that are stores in memory that you wouldn't expect. For example... disk writes. When you create a text file for instance, part of it (if not all) is stored in memory before it's in its actual physical spot of the drive.
There are ways to see this. If someone's comfortable using terminal, type:
Code:
find ~ -size +100M | head -n1
This will output the first file found in your home directory which is over 100MB.
Then do:
Code:
time cat <PathToThatFile> > /dev/null
You'll see some times appear the window.
Then run it again:
Code:
time cat <PathToThatFile> > /dev/null
You'll see times are A LOT lower. See attached image.
That's because that file, after being read, has been stored in memory for if you need to access it again. That is probably system or active memory, but it will eventually go to inactive memory and, when needed, to free (or active again).
My point being, your RAM used isn't the sum of the RAM of all the apps you're running. There's a bunch of stuff using RAM that it's pointless trying to control it. Just use your machine and in case it slows down considerably launch activity monitor and go tot he memory tab.
Doesn't matter if you don't have any free memory as long as you have inactive. The OS should be able to automatically free the inactive memory and give it to whatever app needs it.
Problems start when the system starts to Page Out. If your swap memory is used, then everything will slow down.
(i.e. You have 2 gigs of RAM and launch an iPhoto with a 1.000.000+ photo library. System will page out and will need to use the disk as memory.)