Completely disable VM?

[wikoh]

Is it possible to completely disable virtuall mem in win xp? I have 1024 MB, but setting swapfile to zero or "no swap" doesn't really do it because there are still page faults for running procs (that is, their requested pages are not in RAM)

[dagwoood]

Is it possible to completely disable virtuall mem in win xp?

The short answer is no. By default XP will always want to offload some data to virtual memory; it doesn't matter even if you set your page file to zero, XP will still keep some data in virtual memory.

In effect all you do by setting your page file size is stop XP from searching where to put data it wants to put into virtual memory.

HTH, dagwoood.

[Scarecrow Man]

You have no reason to disable Virtual Memory. Most operating systems use it Windows, Linux. Mac? Standard Virtual Memory Size is 1 1/2 x your RAM. For 1GB use 1533 (1024*1.5). For 512, use 768 (512*1.5)

[wikoh]

That formula doesn't make sense, if you have more RAM you should need less VM. Did you know that a couple of years ago they said that for a Linux install on a 64 MB PC you didn't need any virtual memory? Has applications gotten as much better as their reqs grew? Despite this I believe I do have enough memory to disable it.

Are there some registry edits that will accomplish this? I know of a few, ie:

DisablePagingExecutive=1, LargeSystemCache=1, but I still have page faults so obviously disk is beeing used for RAM.

[Scarecrow Man]

It is ill advised to disable virtual memory in windows. Linux uses the hardware differently, and it also uses what is known as "swap" for it's paging file.

http://aumha.org/win5/a/xpvm.php - Apparently 1.5x is a myth? Read the link for more info.

What is Virtual Memory?

A program instruction on an Intel 386 or later CPU can address up to 4GB of memory, using its full 32 bits. This is normally far more than the RAM of the machine. (The 32nd exponent of 2 is exactly 4,294,967,296, or 4 GB. 32 binary digits allow the representation of 4,294,967,296 numbers — counting 0.) So the hardware provides for programs to operate in terms of as much as they wish of this full 4GB space as Virtual Memory, those parts of the program and data which are currently active being loaded into Physical Random Access Memory (RAM). The processor itself then translates (‘maps’) the virtual addresses from an instruction into the correct physical equivalents, doing this on the fly as the instruction is executed. The processor manages the mapping in terms of pages of 4 Kilobytes each - a size that has implications for managing virtual memory by the system.

What are Page Faults?

Only those parts of the program and data that are currently in active use need to be held in physical RAM. Other parts are then held in a swap file (as it’s called in Windows 95/98/ME: Win386.swp) or page file (in Windows NT versions including Windows 2000 and XP: pagefile.sys). When a program tries to access some address that is not currently in physical RAM, it generates an interrupt, called a Page Fault. This asks the system to retrieve the 4 KB page containing the address from the page file (or in the case of code possibly from the original program file). This — a valid page fault — normally happens quite invisibly. Sometimes, through program or hardware error, the page is not there either. The system then has an ‘Invalid Page Fault’ error. This will be a fatal error if detected in a program: if it is seen within the system itself (perhaps because a program sent it a bad request to do something), it may manifest itself as a ‘blue screen’ failure with a STOP code: consult the page on STOP Messages on this site.

If there is pressure on space in RAM, then parts of code and data that are not currently needed can be ‘paged out’ in order to make room — the page file can thus be seen as an overflow area to make the RAM behave as if it were larger than it is.

[wikoh]

I knew all about that already, except the part about "possibly the original file on disk" which I've now read on other places is the explanation - most OS:es won't load the whole exe or whatever binary into memory at once, but piece by piece. That's why page faults count remain constant after a process has been started, with the exception (at least on my WinXP machine) of a few processes that are particularly happy to create them.