Virtual memory

[thinktank]

I upgraded my T60 from 512MB to 1.5GB memory. What should I set my virtual memory to? And why? What exactly does it do and how do low/high settings influence overall performance?

Thanks.

[DIGITALgimpus]

Let the OS decide for you. There's no evidence that manual tamptering gives any performance boost. 99.9% of the time, people try to minimize it, and that just results in more clutter in your RAM, and ends up causing more problems. Since Windows NT 5.0 (Windows 2k) Windows does a decent job of managing it. It's one of the few things Windows actually does pretty well.

[christopher_wolf]

Just to note; there is *no* way you can tell Windows to use zero virtual memory. In addition, virtual memory is not the same as a pagefile/swapfile. Virtual memory is a way for windows to abstract various system resources as memory, a page file being the most obvious, but not only, example. Windows will always use some virutal memory allocation even if you turn the pagefile swapping off. In general, unless you have a few very volatile applications that suck up memory and require their resources to be available for real-time processing and rendering to the user, you don't need to eliminate the page file as Windows manages that pretty well.

[Wiz]

I upgraded my T60 from 512MB to 1.5GB memory. What should I set my virtual memory to? And why? What exactly does it do and how do low/high settings influence overall performance?

The default by windows is that the initial size of the paging file is 1.5 times the physical RAM on your computer and the max size is default the twice of the initial size. So in your case it would be something like 2304 and 4608 if you follow the windows default. Normally the paging file won't grow beyond the initial size and if it does you should consider installing more ram, but with 1.5gb i guess that won't be a problem. I would just follow the defaults and cannot find a good reason to not.

[leoblob]

Will reducing the size of the page file have any impact on boot times?

[smugiri]

Just to note; there is *no* way you can tell Windows to use zero virtual memory. In addition, virtual memory is not the same as a pagefile/swapfile. Virtual memory is a way for windows to abstract various system resources as memory, a page file being the most obvious, but not only, example. Windows will always use some virutal memory allocation even if you turn the pagefile swapping off. In general, unless you have a few very volatile applications that suck up memory and require their resources to be available for real-time processing and rendering to the user, you don't need to eliminate the page file as Windows manages that pretty well.

@christopher_wolf - while I saw your comment on virtual memory not being the same as swap in all cases, I think that they are synonymous for all practical purposes in the case of Windows. And I suspect this post is really all about the pagefile and there is a way to turn that off. For Windows XP SP2 machines you can pick the option of using no virtual memory in the environment settings. Photoshop (among other applications including Oracle DBs) do(es) not work though - I am still stuck at Photoshop 6 as I am too cheap to upgrade from something that works.

Whether having a swap file will have an effect on boot times or not depends partially on whether you have Windows set up to delete the swap file at every shutdown. If so, it will definitely take longer, if no, then there will be little impact.

[christopher_wolf]

Will reducing the size of the page file have any impact on boot times?

To a minor extent, but Windows is generally more concerned with loading the files that it marked in the pre-fetch and driver folders. It does help, however, to defragment the pagefile during boot.

Steve, that isn't quite the case. Windows, yes even Windows XP, *will still use* some virtual memory regardless of what you have indicated it will do. This is because virtual memory is an integral part of the Windows memory handler. Both Microsoft and Sysinternals have also made notes along those lines (Microsoft has several KB articles on this, as a simple search should show, and Mark Russinovich has also written about it). It does, indeed, affect system performance depending on what you do. If, for example, you have a session or so of AutoCAD 2007 running and have 2GB of memory, it is far more efficient to keep the bulk of the CAD program in the volatile areas of memory to permit faster operations. This is, of course, opposed to swapping data on and off the HDD for a small operation. This is especially evident on smaller systems, such as the X Series.

[smugiri]

Will reducing the size of the page file have any impact on boot times?

To a minor extent, but Windows is generally more concerned with loading the files that it marked in the pre-fetch and driver folders. It does help, however, to defragment the pagefile during boot.

Steve, that isn't quite the case. Windows, yes even Windows XP, *will still use* some virtual memory regardless of what you have indicated it will do. This is because virtual memory is an integral part of the Windows memory handler. Both Microsoft and Sysinternals have also made notes along those lines (Microsoft has several KB articles on this, as a simple search should show, and Mark Russinovich has also written about it). It does, indeed, affect system performance depending on what you do. If, for example, you have a session or so of AutoCAD 2007 running and have 2GB of memory, it is far more efficient to keep the bulk of the CAD program in the volatile areas of memory to permit faster operations. This is, of course, opposed to swapping data on and off the HDD for a small operation. This is especially evident on smaller systems, such as the X Series.

I cannot seem to make any headway finding material covering non-swap virtual memory in Windows, any chance you could point me to some of the resources that you mentioned please?

[christopher_wolf]

Sure; a look-through of the KB database at Microsoft.com will give the following...

http://support.microsoft.com/default.as ... -us;555223

In modern operating systems, including Windows, application programs and many system processes always reference memory using virtual memory addresses which are automatically translated to real (RAM) addresses by the hardware. Only core parts of the operating system kernel bypass this address translation and use real memory addresses directly.

Virtual Memory is always in use, even when the memory required by all running processes does not exceed the amount of RAM installed on the system.

As such, it is an *integral part* of the Windows Memory manager and quite a few things, excepting the kernel, simply wouldn't run without it. Again, it *does not* cannonically equal the paging file alone; think of the paging file being used as a type of memory container with special handling to make up for slower read/write ops. Essentially, that is all you have to do to get a page file to work and that happens to be one, but not the only, application of virtual memory on most Windows OSes. Looking at a filesystem, say JFS and its derivatives, you can trace their development all the way back to components of IBM's research into memory managers.

See also;

http://members.shaw.ca/bsanders/Windows ... ileEtc.htm

In addition to;

http://shsc.info/WindowsMemoryManagement

Also, various tasks (printing to a PDF) and interaction with external computer equipment, on Windows, have virtual memory assigned to them. Another good example is when you plug in a removable media device; Windows has to have a way to reference and access the storage area on the device, either RAM or HDD based storage, quickly over UPnP and virtual memory is a key component in allowing it to do this.

HTH

[Kyocera]

large print job spooling is an example of virtual memory use.

[smugiri]

Thanks for the links and explanations @christopher_wolf, I love learning new stuff. So, my new understanding of the gist of the material you pointed me to is that virtual memory is the combination of swap, paging files, extended memory and temporary files used by the OS/apps. Does this sound accurate?

[christopher_wolf]

Thanks for the links and explanations @christopher_wolf, I love learning new stuff. So, my new understanding of the gist of the material you pointed me to is that virtual memory is the combination of swap, paging files, extended memory and temporary files used by the OS/apps. Does this sound accurate?

Almost; just about everything that can be used as a storage device can have virtual memory attached to it. Virtual memory is more of a way to abstract storage (storage in the sense that Windows is equating it with memory). Basically anytime a process needs to use a form of memory it gets a handle to resources covered by virtual memory. Also, virtual memory is used as a way for windows to present memory to large tasks that would usually cause interrupts in the smooth flow of operation (due to the increase in the rate of resource acquisition by the large process), such as printer spooling as Mike pointed out.

[fschwep]

As other and more technically inclined posters have shown the virtual memory is a complicated thing. As far as the swap file is concerned, I have adopted the habit of setting its maximum and minimum sizes to be identical, so that the file does not change size. It can then be defragged into a single block that remains where it is and/or moved to the beginning of the harddisk (provided the defrag software/Windows lets you do that).
On my X30 I have done the experiment of turning the page file off. It has 512 MB RAM and it seems to run happily without the page file, with less disk access and a slightly cooler harddrive. It also runs a bit longer on battery power (I used the gain in battery duration to set the screen brightness in BIOS to Normal so it is just as bright on battery as on AC power). Of course I do not run PhotoShop or large databases on that machine...

[bill bolton]

It can then be defragged into a single block that remains where it is and/or moved to the beginning of the harddisk (provided the defrag software/Windows lets you do that)

In general, having the pagefile in about the middle of the boot drive partition is a better strategy than placing it at the begining of the boot drive partition.

Cheers,

Bill

[christopher_wolf]

You can place it as Bill said, or you can let something like PerfectDisk 7.0 handle it during an offline defrag and placing the proper reference files during an online defrag.

[Deckard]

Hello,

quite a while ago, I came across a site, as I have upgraded the memory on my laptop. I have followed the instructions on their site to the letter, which worked very well for me.

Here's the link to the site:

http://www.theeldergeek.com/paging_file.htm

[pvetch]

Recently (2 - 3 months ago) German mag C'T (an excellent, very competent and trustworthy publication - unlike any other computing magazine...) ran an article which put to the test about 40 or more well known 'so called' Windows tweaks, including fixing virtual memory at a set size, putting the paging file on another disk, etc. They also tested loads of other tweaks you see about the internet. In every single case they performed benchmarks and found that tweaking Windows settings either had no performance effect, or a detrimental effect.

YMMV but on the strength of this I've changed from being a tweaker to letting Windows get on with looking after itself - the numbers don't lie....

(Sorry, I can't find the article online to link to)

[jdhurst]

@pvetch - good post. Thank you. JD Hurst