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Archives => 2008 => Topic started by: MamaMoose on April 02, 2008, 01:36:35 AM

Title: Page ins/outs - Interpreting values
Post by: MamaMoose on April 02, 2008, 01:36:35 AM

I notice in my activity Monitor under Systems there values for  Page Ins/Outs = 392940/0. I assume it describes the number of pages being transferred from Virtual Memory to RAM vs. the number of pages being transferred from RAM to Virtual Memory. Its been ~ 30 years since i worked on virtual memory development  and I do not remember how to interpret the values above. Are the good, bad, or who cares?

I am running a 17" MacBook Pro (2.4 GHz dual core Intel) with 4 GB of RAM and a 320 GB 5400 rpm internal hard drive.


Thanks,


MamaMoose

Title: Page ins/outs - Interpreting values
Post by: krissel on April 02, 2008, 04:43:07 AM

Those are excellent stats and are due to the 4G of RAM.  Anytime you have 0 Pageouts it is a good thing...as Martha would say.

Here is a good brief explanation:

QUOTE

1. all memory in OS X is "virtual". Some of that virtual memory is in RAM, some in system and application files on the hard drive, and some may be in swapfiles
   2. Wired RAM is memory that is pernamently "locked" by the OS and cannot be made inactive or moved to swapfiles. It must be there for the operation of the OS
   3. Active RAM is memory that is currently in use by either the system or an application.
   4. Inactive RAM may be thought of as a first stage swapfile. It contains instructions and data that are not currently in use within the OS or an application, but is left in RAM in the event it is needed again. If more Active RAM is needed, the Inactive RAM will be reassigned and if it contains data for a currently open application, that data will be rolled out to a swapfile. Otherwise the memory will simply be overwritten.
   5. Free RAM is just that. It is RAM that is currently not mapped into Wired, Active, or Inactive RAM. If more Active RAM is needed, the Free RAM will be the first to be remapped into Active status.
   6. Swapfiles are used to contain data being used by currently open applications for which there is currently no room in either Active or Inactive RAM
   7. System resources, fonts, application files, frameworks (shared libraries) are mapped into the virtual memory address space for each application whether they are in Wired, RAM Active RAM, Inactive, RAM, or in files on the HD, but these resources are never placed in the swapfile(s) because they are already available on the hard drive and there is no point in duplicating the code.
   8. Pageins occur anytime something is moved into Active RAM whether that is from Inactive RAM, the swapfile(s), or another file on the hard drive.
   9. Pagouts occur anytime anything is moved out of Active RAM which includes mapping into Inactive RAM, as well as writing to a Swapfile. Only data is ever written to the hard drive since instructions are already on the hard drive.

http://macosx.com/forums/mac-os-x-system-m...ot-fashion.html

More detailed explanation:

http://en.wikipedia.org/wiki/Paging

Title: Page ins/outs - Interpreting values
Post by: Paddy on April 02, 2008, 07:09:52 AM

I recently got another 2 GB of RAM, boosting the RAM in this G5 to 4.5 GB. Before I did, I'd been seeing a lot of pageouts and many slowdowns. It's made a huge difference - no more pageouts and no more turtle-like behaviour. I do tend to run a lot of memory-hogging apps at a time (Photoshop, InDesign, Dreamweaver, Safari and several other browsers) and 2.5GB just wasn't cutting it anymore.

Pretty wild when you think that I now have 900X the RAM I had in my first IIsi and that the RAM has over 100X the capacity of the HARD DRIVE in that IIsi - a machine that we bought in '91 and that I was still using until 11 years ago, though by then I had a whopping 750MB external drive to augment the 40MB internal!