[jessejlt]

I'm on an iBook 600 (snow) r.2 and I have 640 mb of physical ram installed. After I reboot and all the apps that I have set to start have started, I have about 250 mb used up. I noticed that at this time I also have 5 pageouts. Is this normal behavior? My understanding of a pageout was that they were used when the physical ram is all used up so the OS will write some of that ram to disk, thus a pageout. Is this correct, more than less?



jesse ;-)

[superlarry]

your understanding is mostly correct.. the problem is that OSX (and maybe BSD?) handles it a little differently. i'm not sure about the technical details, but you'll almost always get pageouts before you're out of physical RAM.
so i guess all i can say is not to be worried - that's normal. i just wish i could explain why ;c) i seem to get different behavior out of linux (2.4.20) - more what i'd expect.

[someone_else]

Originally posted by superlarry:
your understanding is mostly correct.. the problem is that OSX (and maybe BSD?) handles it a little differently. i'm not sure about the technical details, but you'll almost always get pageouts before you're out of physical RAM.
so i guess all i can say is not to be worried - that's normal. i just wish i could explain why ;c) i seem to get different behavior out of linux (2.4.20) - more what i'd expect.

This is because the kernel will "age" pages that are explicitly marked as "probably won't be used again". Since these pages may be used in the future, but aren't likely to be, they are paged out to disk so more real RAM is availble. The pages aren't actually released, because the page MAY be needed in the future.

The Linux kernel is different, it generally won't page out until it absolutly has to.

The OS X behavior is similar to *BSD which is considered to have a better VM system than Linux.

IOW, what the OP is seeing is normal (and generally preffered) behavior.

HTH.

[superlarry]

cool - thanks!