General Question

queenzboulevard's avatar

What are page-ins and page-outs?

Asked by queenzboulevard (2549points) October 11th, 2008

I have the iStat nano widget and under memory it says page-ins and page-outs. Is it bad to have a lot of one more than the other? How does it affect my Macbook?

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4 Answers

jrpowell's avatar

That is basically when your computer is using your hard drive for memory instead of RAM. RAM is lots faster so you want to keep both numbers low. Right now I am at about 2 million on both. But my computer has been on for 27 days so that isn’t a good metric for a MacBook.

You should go to the Apple menu in the upper left and select About this Mac. Let us know how much Memory you have installed. If it is under 2 GB you could probably use more.

jrpowell's avatar

RAM is really cheap right now. You should have more. I would suggest 2 GB. Right now you can get that for 33$ from

I went from 512 Megs to 2 GB and it was like getting a new computer. And RAM is easy to install. But the moral is that you should have more.

jaredg's avatar

Page ins are unavoidable, that’s just an indicator that the machine is moving stuff around in memory—OS X and the Mach microkernel have sort of a weird way of managing memory from what I recall. Page outs are the things you want to avoid—that means a page of memory is being “swapped” out to disk to make room for something else as johnpowell said above.

I’ve got 4gb of memory in my computer and, as a dirty secret, I rarely use most of it. So all it does is soak up a little more battery and give off more heat. If you don’t have any/many page outs(under 5–10% of the page in value) after you’ve used your computer as you would normally for a few hours after reboot, you’re probably good on RAM. has a decent discussion; stuff I read on the Apple Support forums and on another site jives with what bobw says there.

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