Today, I was looking at my system stats in the iStat Pro widget and noticed I had about 20 mb of free RAM. Even after restarting my Mac, within minutes of having several apps open, the RAM starting decreasing significantly. What's the deal? What should I do to optimize RAM usage besides performing maintenance on my Mac?

Thanks,
Mason

[Thinine]

Don't worry, that's normal.

Originally Posted by Thinine 

Don't worry, that's normal.

Should I just go ahead and max out to 2 GB RAM on my Mac?

Mason

[Sherman Homan]

Yup, it is normal. You can check your Activity Monitor. The Mac OS is smarter than you. It is smarter than me. The only thing that counts is page in and page outs. Look at System Memory. You want a big fat "0" for page outs. The Mac handles memory dynamically. If you don't have enough memory your Mac will start hitting the hard drive in desperation. Your page outs will increase, your Mac will slow to a crawl. If your page outs are small then you don't need more memory.

Originally Posted by Sherman Homan 

Yup, it is normal. You can check your Activity Monitor. The Mac OS is smarter than you. It is smarter than me. The only thing that counts is page in and page outs. Look at System Memory. You want a big fat "0" for page outs. The Mac handles memory dynamically. If you don't have enough memory your Mac will start hitting the hard drive in desperation. Your page outs will increase, your Mac will slow to a crawl. If your page outs are small then you don't need more memory.

Thanks. That was pretty funny what you said about the Mac OS being smarter than you. I guess I need to max out on my RAM.

Mason

[mduell]

Free memory is wasted memory. I mean, really, you paid for it, and it's empty!

OSX, Windows, and other modern OSs use otherwise-available RAM to cache files, so they can be accessed quicker and without waking the hard drive. As soon as an app needs that memory, the OS makes it available.

[cgc]

I have almost 900,000 page-ins and only about 3,000 page-outs. Is the number important or is the ratio?

[Thinine]

It's the ratio. And that's a pretty damn good ratio. How much RAM do you have?

[Big Mac]

Page-ins: Good, Pageouts: Not as Good. You should have an imbalance of Page-ins to Page-outs if you have enough RAM for your workflow (which you currently do from the look of it). That's a basic tip. Another way I evaluate RAM usage is to look at the ratio of Active+Wired RAM to Inactive+Free RAM. You should consistently have *at least* a 50-50 split; if Active+Wired accounts for most of your RAM, you don't have enough for your workflow. When my G5 had 2GBs, I used to consistently have an imbalance of Page-outs, and I noticed excess disk activity especially when switching users. After adding a GB, I no longer have that issue and Activity Monitor shows an imbalance of Page-ins.

We really should have a sticky on OS X RAM usage.

[OreoCookie]

Seems pretty optimized to me.

[peeb]

Yep. As above - the free memory thing is very deceptive. Only swapping to disc matters.

[TETENAL]

Mac OS X: Reading system memory usage in Activity Monitor

[cgc]

Originally Posted by Thinine 

It's the ratio. And that's a pretty damn good ratio. How much RAM do you have?

3GB