Why am I always running out of RAM?

Question

For a pair of weeks now I have been doing all I am capable to understand the problem I have been experiencing. The language and terminology if my issue is somewhat foreign to me, but here is my best explanation.
On my Mac Pro 8-core 2.8 GHz tower with 8 GB of RAM I am finding myself running very few operations but end up in a situation where I can visibly see my performance bogging down as if I am out of RAM.
So I have been running activity monitor and what I am seeing is 40 MB of "Free" RAM with 630 MB "Wired", 2.5 GB "Inactive" and about 5 GB of "Active".
I understand some of the basics of what these terms mean. Here is one thing I am 100% certain: after a reboot I start with a massive majority of "Free" or "Green Colored Pie Section" of RAM and when this is happening, my performance is fantastic. Whenever I have a few GB's of RAM, I never complain about my performance.
Here is something I am almost 100% certain of: when my performance is poor or lacking, I notice two things that I find alarming: 1) I have under 100MB of "Free" RAM and 2) 50-60% of the RAM pie is colored yellow indicating "Active".
I am using very common applications and even when I quit all of my applications (except activity monitor) the active RAM is still dominating my 'pie'.
That's the best I can do for now, any help is appreciated.
Thanks,
Jeff

Answer 1

JeffKasper wrote:
So I have been running activity monitor and what I am seeing is 40 MB of "Free" RAM with 630 MB "Wired", 2.5 GB "Inactive" and about 5 GB of "Active".
Both "Free" and "Inactive" are (supposed to be) available for use by any process that wants it.
When you first start up, most memory is, of course, "Free." As apps or system processes need memory, that's where OSX gets it. When they release it, however, it does not go back to Free, but to "Inactive" and is identified with the last process that used it. This is done to speed up assigning it back to the previous process if it requests it (which of course is quite common).
So as time passes, you'll see less and less Free memory and more and more Inactive memory; this means your Mac is working properly. In fact, after running for a long time, if there's much Free memory left, it is, in a sense, wasted!
The thing to watch for is Paging. If the "Page outs" figure is high, or changing rapidly, then OSX is having to page stuff out because it's out of both Free and Inactive memory.
A better way to monitor page-outs is via a Terminal command. (The Terminal app is in your Applications/Utilities folder.) Enter the following, exactly as shown, at the prompt:
sar -g 60 10
Leave the terminal window open, then try to re-create the unresponsive problem.
This should tell you if you are doing pageouts. You'll see a line in the Terminal window every 60 seconds for 10 minutes (or until you quit Terminal), showing the number of pageouts per second. A few pageouts is normal. If you have large numbers of pageouts, then you have a memory problem.