Paging: in and outs.

Question

Hello,
I've read a lot of articles about memory management in Mac OS X on this and other forums. But something caught my attention, and I think you could help, if you please.
I've read that paging out is bad, and if its growing constantly, you should add more physical RAM.
However, I couldn't find anything about paging IN.
On my iStat, shows I have 50,000 page in. What does that mean? Should I add more RAM? Is that bad as page out? Don't need to worry?
I have concluded also that swap files are more like a emergency or a last resource utility. Being that said, how could I have paging outs when Activity Monitor shows more than 700Mb of Free RAM?!?
Don't think something is going normal, and I just bought my new MacBook, sad... please help.
I used Leopard Cache Cleaner to optimize ram, among other things, don't think that was helpful either.
Summarizing:
1) Should I worry about 50,000 of pagein?
2) Having 700Mb of Free RAM, is it normal to have pageouts?
ps: Status retrieved when running these applications: Safari(1 tab); iTunes; Microsoft Messenger; Microsoft Word; Transmission; and, uh... Finder.
Thanks,
Danilo.

Answer 1

On my iStat, shows I have 50,000 page in. What does that mean? Should I add more RAM? Is that bad as page out?
As already mentioned, page-in is how Mac OS X (and many operating systems) load programs into memory. And yes pages paged-out may end up being paged back in, but that is noise compared to other normal page-in activity.
how could I have paging outs when Activity Monitor shows more than 700Mb of Free RAM?!?!?!
You are trying to compare Grapes and Cranberrys. The 700MB of free RAM is a "Current" amount. The Page-outs is a cumulative from when you booted your system. You can not compare the 2.
If you have installed the Xcode developer tools from your installation DVD, then you will have the vm_stat command line utility. Start an Applications -> Utilities -> Terminal session. Run the command
vm_stat 60
Let this run in the background while you use your Mac normally. It will output paging information once every minute. After an hour or so of normal usage, go back and look at the vm_stat output.
Look at the pageout column (last column). If most of the values are zero or very low numbers, your memory is fine (ignore the values just after the header lines as these are cumulative values).
If you are seeing large numbers for pageout (100's or even 1000's of page-outs) per minute, then you could use more memory.
If mostly you have zero or low page-out numbers, but once in a while when starting up a big application you get a short duration page-out spike, this is not really a problem, and virtual memory is doing what it is suppose to do, namely allow you to run lots of applications without needing to over spend on memory.
If while using your Mac you notice annoying slow downs, especially when switching between applications, and you examine the vm_stat output and see serious page-out activity during that period of time when you were experiencing the slowness, then more memory would be helpful.
If you think you have identified an activity that is running slow because of page-outs, then run vm_stat with a shorter time interval, such as:
vm_stat 5
and then run through your slow activity and look at your vm_stat page-out values to see if there is a direct relationship between your slowness and page-out activity.
Again, a few page-outs per minute with a once in a while page-out spike is not a problem.
But if "Money is No Object", then by all means, buy more memory. The memory vendors will thank you