Pagefile and Ram Question

[Stinger 0]

I have heard about a million different explanations of the pagefile. I know that it is what Windows uses when it runs out of Ram and puts it to disk but...why is the pagefile being used then if I have Hundreds of megs free of Ram?

[Dark Ranger 0]

Well, let's see how much of this I can answer:

First off, Windows OS's have a "Virtual Memory Management" system(VMM), which reads and files ALL of the data the computer uses or needs, before it ever gets to the Physical Memory. The VMM provides the ability to run more apps concurrently than would normally be possible using just the amount of physical ram. This is obviously a useful feature for computers with a small amount of Ram.

When a thread requests access to memory resourses, it requests a "Virtual Address Space". Then, VMM uses the Virtual Address requested by the process or thread to locate the corresponding physical address(on memory chip). Then it transfers the data. So for instance, let's say you want to start up MS-Word. Once you click the icon, or program name, VMM figures out how much data to buffer to the Ram, by how may processes required to start up the program. It will get alot of data from the HDD too, but once Windows VMM figures out how much ram required to start the application, it assigns portions of that data a Virtual Memory Space, which then corresponds to a Physical Memory Space. There for you will use 30MB of Ram or whatever to start the program.

The act of Paging referrs to moving memory contents to and from the HDD when needed. When your Ram (physical memory) becomes full from many tasks completed over time, VMM moves some of the data(pages) from the Ram to a storage area on disk called a PageFile. The data on the HDD can still be used again, however, its former space on the RAM was replaced by data that needed more importance at the moment.

So, Valid Pages are those pages or processes located in the physical memory available to process. Invalid Pages are those that don't exist anymore in the memory. They are either not available to process or on the HDD. So, if you have ever received a "Page Fault Error in Sector bla bla bla", it means that the data requested to start an application was not available or located on the HDD. This is what happens to correct the Page Fault:

1. The MicroProcessor issues an Error Message and Page Fault.

2. VMM traps the page fault, locates the required page (data), then loads it into free space on RAM. If no free space can be found on RAM, then it takes the oldest pages and data from the RAM, places it on the HDD, then takes the requested data and loads it into the now free space on RAM.

How to correct or increase the VMM Paging File size:

Open up your Control Panel, and click on the System icon.

Click on the Advanced tab, and click Performance Options. You will notice you can optimize processing and resourses for either Background Services (all open applications get the same amount of CPU time, memory, etc.), or Applications, (only the most important, or current window app will receive the most attention. This is the Default method.)

You will then see a Total Paging Size for all Drives box. This is the Windows VMM portion. Click Change.

Now, depending on how much RAM you have in your machine, the Recommended size is 1.5 times the Physical Memory. So for instance, Stinger has 512MB of RAM. Recommended is 768MB. However, you can choose to enter the Maximum value(2 times the Physical Memory), in Stinger's case, would be 1024MB of Paging size. This is what I have done with my machine, and it helps if you run many concurrent apps.

As far as using all of your RAM, this doesn't happen too much, especially in your case. But the VMM does most of the work.

Hope this helps you Stinger, and anyone else that is wondering about Paging.

[Stinger 0]

GRACIAS SENIOR! I have a 1500mb page file I knew how to change that but never understood much about it. Again thanks