[equinox]

Hi,

i have an iMac G5 20" and 2 GB RAM. I can see that my system is paging a lot. Using iTunes and Safari i get 23000 pageouts and 2800 pageins. My virtual memory-size is 4,5 GB. Why that? I thought 2 GB RAM should be enough but if i see the paging i must be wrong!?

Regards,

Peter

[CatOne]

Originally posted by equinox:
Hi,

i have an iMac G5 20" and 2 GB RAM. I can see that my system is paging a lot. Using iTunes and Safari i get 23000 pageouts and 2800 pageins. My virtual memory-size is 4,5 GB. Why that? I thought 2 GB RAM should be enough but if i see the paging i must be wrong!?

Regards,

Peter

That's how many pageouts you have TOTAL? You shouldn't be worrying about it. How long has the machine been up?

Pageins/outs may NEVER be absolutely 0, even if you have 10x the RAM you need. The OS is pretty efficient about it, don't try and read one or two statistics and assume it's doing something wrong.

[Big Mac]

Yeah, there is something wrong there - you're getting far too many pageouts. Do you mean you only have Safari and iTunes open and you're seeing that level of pageouts? It sounds like there's some serious OS level corruption and an archive and install is in order.

[chabig]

I concur with CatOne. It's not something to worry about.There is nothing wrong with your Mac or the System software. My Powerbook has 768MB of RAM and I have 239581 page ins and 116274 page outs with an uptime of 5 days, 20 hours.

Repeat the OS X mantra three times while clicking your heels together--"Free RAM is wasted RAM, free RAM is wasted ram, free RAM is wasted RAM."

Chris

[osxman]

I think the important thing to look for is pageins vs pageouts.
If the number of pageins is greater than pageouts then there is nothing to worry about.
If pageouts is greater than pageins then you have too little ram,
but with 2GB ram this should not be the case (if you are not running many
memory hungry apps at the same time).

osxman

[SMacTech]

Originally posted by osxman:
I think the important thing to look for is pageins vs pageouts.
If the number of pageins is greater than pageouts then there is nothing to worry about.
If pageouts is greater than pageins then you have too little ram,
but with 2GB ram this should not be the case (if you are not running many
memory hungry apps at the same time).

osxman

2GB of ram is not what it used to be. Run PhotoShop, Safari, some torrent apps, iTunes and there goes your RAM.

Why not post a profile of your system using top -u to show exactly what is going on instead of all this surmising?

[mfdynusore]

Originally posted by equinox:
Hi,

i have an iMac G5 20" and 2 GB RAM. I can see that my system is paging a lot. Using iTunes and Safari i get 23000 pageouts and 2800 pageins. My virtual memory-size is 4,5 GB. Why that? I thought 2 GB RAM should be enough but if i see the paging i must be wrong!?

Regards,

Peter

Doesn't the OS page out the entire address space during launch? If it does then the pageouts are not important and your page in count is actually quite reasonable.

[Big Mac]

Originally posted by mfdynusore:
Doesn't the OS page out the entire address space during launch? If it does then the pageouts are not important and your page in count is actually quite reasonable.

No, it does not just pageout an application's memory space just to do it, and certainly not at launch. This logically could not be because there is no incentive to pageout the contents of RAM to disk while that data is active. Besides, if this were the case, then after a fresh restart one would always see pageout activity, which usually is not seen for at least awhile after a fresh boot. A pageout takes place when the system has to provide RAM for an application but does not have enough free to do so, causing it to move something else from RAM to the disk. A pagein happens simply when data paged to disk comes is transferred back to RAM. For long periods between boots (in which many applications are launched, are run and closed), you'll naturally see a lot of pageins and pageouts. But if you're seeing a lot more pageouts than pageins, that means that much more often than not the system is having to switch out data from RAM to disk rather than getting from disk back to RAM. It is important not to confuse pageins and pageouts with plain virtual memory use, because there is a distinction. Even if you have four gigs of RAM, you'll still see virtual memory being used because applications reserve more memory than they actually use. The OS reserves virtual memory for them at launch, which may have been what mfdynusore meant. The virtually memory reserved is different from pageins/pageouts.

Another important piece of the equations is the number of pageins and pageouts inside the parenthesis when you're looking at the terminal's top command. The numbers in the respective parenthesis refer to the number of disk operations (pageins or pageouts) within five seconds, and if you're seeing those numbers increase (past 25 I've heard) during routine work, that's another indication you need more RAM.

[Tyre MacAdmin]

See this article:
http://arstechnica.com/reviews/01q4....html#vm-basics
"The Buffer Cache

The second most important factor in Mac OS X's memory usage behavior is the buffer cache. The buffer cache is meant to speed up access to files on disk. Every time a piece of data is read from the disk, it may (optionally) be stored in memory. If that same piece of data is needed again in the near future, it may still be available in (physical) memory, saving a trip to the disk. Mac OS X implements a "unified buffer cache", meaning that the buffer cache and the virtual memory system are combined. A page is a page is a page in Mac OS X.

The buffer cache affects RAM usage in ways that a Mac user may not expect. Heavy file i/o can use a lot of physical memory very quickly, potentially thinning out the physical memory presence of running applications. Poorly written applications may exacerbate this problem by using cached file i/o when it is not necessary, or even useful. An application that reads and parses a large file a single time during start-up should probably not use caching i/o, since it is not likely that the application will need those memory pages again some time in the near future before they're evicted from physical memory by another active process."

Since the buffer cache and memory system are combined this is more than likely the reason you're coming back to your computer and seeing the slow down... because the applications you've been using are in the buffer cache and have been paged out to disk... all that info being pulled from disk is causing the slowdown and since you reboot it's cleared and now everythig is loaded in to memory."


If you are switching between a few different apps and some are taking *priority* over others then you are going to see some paging.

If it's actually impacting performance then you should put your swap on a different high speed disk/disk system

Otherwise, more than likely it's normal and it's your machine self optimising itself.

[themexican]

I have 3 gigs of ram and a similar problem. It seems especially bad in Safari which often takes up 80% of CPU and gives me the beachball all the time. I've deleted prefs and the icon cache... but am not sure what else to do. in top, rsize =387M, vsize = 823M

Page ins 1106566/ outs = 1245081

admittedly I have a ton of apps open, but with 3 gigs safari shouldn't be beachballing up every minute or two.

[mfdynusore]

Originally posted by Big Mac:
No, it does not just pageout an application's memory space just to do it, and certainly not at launch. This logically could not be because there is no incentive to pageout the contents of RAM to disk while that data is active. Besides, if this were the case, then after a fresh restart one would always see pageout activity, which usually is not seen for at least awhile after a fresh boot. A pageout takes place when the system has to provide RAM for an application but does not have enough free to do so, causing it to move something else from RAM to the disk. A pagein happens simply when data paged to disk comes is transferred back to RAM. For long periods between boots (in which many applications are launched, are run and closed), you'll naturally see a lot of pageins and pageouts. But if you're seeing a lot more pageouts than pageins, that means that much more often than not the system is having to switch out data from RAM to disk rather than getting from disk back to RAM. It is important not to confuse pageins and pageouts with plain virtual memory use, because there is a distinction. Even if you have four gigs of RAM, you'll still see virtual memory being used because applications reserve more memory than they actually use. The OS reserves virtual memory for them at launch, which may have been what mfdynusore meant. The virtually memory reserved is different from pageins/pageouts.

Another important piece of the equations is the number of pageins and pageouts inside the parenthesis when you're looking at the terminal's top command. The numbers in the respective parenthesis refer to the number of disk operations (pageins or pageouts) within five seconds, and if you're seeing those numbers increase (past 25 I've heard) during routine work, that's another indication you need more RAM.

I assume you are correct as I know very little about Mac osx. However, some multiple virtual systems do write the backing pages at launch as it allows you to simply reuse the real storage without paging it out when needed by another address space. Of course this assumes the pages are re-entrable code and may not apply to Mac osx. ymmv.