Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

From what I've read, page outs are a sign that you don't have enough RAM. I have also read that if you have inactive memory available, then the machine will use that memory when starting up new programs.

I have about 2GB of inactive memory and very little available memory. Once this happens, my page outs go up. Why is this and do I need more memory?

I have 8GB of RAM. I'm running VMware Fusion 5 with 2GB allotted to Windows 8.

share|improve this question
windows does that too. I can have 6GB free and there is still some paging. the only modern os I've see that doesn't is linux. I wonder if its stale IO cache. – Frank Thomas Dec 1 '12 at 4:24
The reason you don't have an answer is probably because the actual answer is "it's a bug". It looks like a pretty frequent problem, and the answer is too often "buy more memory". Of course from a user's perspective it will temporarily alleviate your system, but you're going to hit it again later on (I do with 24GB RAM, I can often see 10GB inactive and the system actively paging out... it only happens less often when I run more RAM-hungry programs). – Calimo Nov 15 '13 at 9:19

Here is what Apple has to say about it. In general, inactive memory isn't quite the same as free memory. The kernel might be using it for disk buffer cache, read-only executable pages (the Mail example from the support page), or the inactive memory might be pages of memory from an existing application process that has not accessed them in a while. If memory demand goes up and the amount of free memory reaches a critical point, some of these inactive memory pages will need to be reclaimed, which means page outs for the inactive pages of existing processes.

Page out activity is a sign that you're edging toward a memory starvation situation, but the definite sign of too little memory is heavy paging activity both in and out while doing your normal work. The system is thrashing at this point; active memory pages are being ejected from main memory and the operating system is wasting considerable time waiting for pages to be read back from disk. When you see this, it's time to buy more RAM.

share|improve this answer
This doesn't really answer the question. Page out refers specifically to moving pages from RAM to disk, not from inactive to active, as your link says: "This refers to the amount of information moved between RAM and the Mac's drive". The link also says that "Inactive memory is available for use by another application, just like Free memory", and I can't really see any situation where paging out would be better than using this inactive memory. – Calimo Nov 15 '13 at 9:11

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .