virtual memory managment

Hi there,

I've been using Windows 7 now since 6th of May, and love it! I haven't had any troubles except 2, but this topic is meant for only one.

I remembered an application called Everest, it lists all of your hardware and information about it, OS and stuff, really nice. It also has tab for sensors, where you can monitor temperature.

When i was looking around in Everest, I found out somehow 7gigs. of virtual memory is available, and most of the time somewhere around 2gig. is being used. That was kind of weird, because I have 4 gigs of RAM, and most of the time only 25% is used of it. So, why would Windows prefer use of the virtual memory over the use of physical memory? I found out virtual memory could be managed in "advanced system settings". because 2.5 gigs of virtual memory was used most of the time, I thought: why not just completely disable paging file.

So it's: computer --> right click properties --> advanced system settings --> advanced tab --> performance --> settings --> virtual memory --> change.

So finally comes the problem, I have succesfully disabled the paging file, and it says "total paging size for all drives: 0 mb". But when I go to Everest, it still says I have 7 gigs of Virtual Memory available, and it uses 2 gigs........ I want to make full use of my physical memory!

Windows uses virtual memory for running it's processes. The Windows Memory Manager (WMM) manages the virtual memory by swapping it in and out of physical memory (RAM). Different limits apply for each.

The confusion arises in 32 versions of Windows when the WMM allocates 4 gB of virtual memory address space for each process With 50 processes running, that's 200 gB of virtual memory address space. Needless to say, each process doesn't use all 4gB - but it's there in case it's needed.

With 32 bit OS's, there's a limit on physical RAM of 4gB. You can install as much as you want (as long as the motherboard can handle it) - but only the first 4 gB will be recognized/utilized. Also, some hardware devices (video cards in particular) reserve some of this address space for their own use. So that's why 32 bit versions of Windows can only use 2.5 to 3.6 gB of RAM.

For 64 bit systems it gets a bit more complicated - but the numbers are essentially just larger versions of the 32 bit numbers.

For more info, here's a couple of links:
Physical Memory: Mark's Blog : Pushing the Limits of Windows: Physical Memory
Virtual Memory: Mark's Blog : Pushing the Limits of Windows: Virtual Memory
The Virtual Memory link also discusses the pagefile.

usasma said:

Windows uses virtual memory for running it's processes. The Windows Memory Manager (WMM) manages the virtual memory by swapping it in and out of physical memory (RAM). Different limits apply for each.

So when it says it's using 2gb. of virtual memory, that doesn't necessarily mean it's using 2gb of virtual memory on the hard drive?

I'm using 64-bit windows, so the limit shouldn't be a problem. I was just wondering why my windows would use disk space as memory, if there is plenty of "room" on my physical memory (4gb total, but only using 35% now).

Thanks for all of the replies. Guess I still have a lot to learn about (virtual) memory managment in Windows. I was just a bit "scared" my 4gb. physical memory was quite useless, and trying to make optimal use of it. I've re-enabled the page file and set it to auto-size, but if Windows screws it up, we're through ^^

usasma said:

Windows uses virtual memory..... - but the numbers are essentially just larger versions of the 32 bit numbers.

For more info, here's a couple of links:
Physical Memory: Mark's Blog : Pushing the Limits of Windows: Physical Memory
Virtual Memory: Mark's Blog : Pushing the Limits of Windows: Virtual Memory
The Virtual Memory link also discusses the pagefile.

Thanks! Great help!