Setting virtual memory - Good Practice

[Tesla]

hi peeps

 

what are the general rules you go by with regards to virtual memory? do you let the system deal with it, or do you find other methods better (such as setting up paging files etc on a separate partition etc)

 

if you have lots of RAM (i have 8GB in my home pc) do you set it low?

 

my "system managed" paging file was made to be about 8gb, which seems surplus to requirements with 8gb of ram already on the machine? (i don't do particularly heavy duty stuff either)

 

thoughts on this appreciated. Cheers.

Edited May 21, 2014 by Tesla

[Norphy]

General practice is to either let the OS handle it or to set it to 1.5x the amount of physical RAM.

[Arthur]

what are the general rules you go by with regards to virtual memory?

Either let Windows manage the page file or adjust the size of it based on your peak commit charge. See the explaination from Microsoft's Mark Russinovich below...

 

Pushing the Limits of Windows: Virtual Memory

 

How Big Should I Make the Paging File?

Perhaps one of the most commonly asked questions related to virtual memory is, how big should I make the paging file? There’s no end of ridiculous advice out on the web and in the newsstand magazines that cover Windows, and even Microsoft has published misleading recommendations. Almost all the suggestions are based on multiplying RAM size by some factor, with common values being 1.2, 1.5 and 2. Now that you understand the role that the paging file plays in defining a system’s commit limit and how processes contribute to the commit charge, you're well positioned to see how useless such formulas truly are.

 

Since the commit limit sets an upper bound on how much private and pagefile-backed virtual memory can be allocated concurrently by running processes, the only way to reasonably size the paging file is to know the maximum total commit charge for the programs you like to have running at the same time. If the commit limit is smaller than that number, your programs won’t be able to allocate the virtual memory they want and will fail to run properly.

 

So how do you know how much commit charge your workloads require? You might have noticed in the screenshots that Windows tracks that number and Process Explorer shows it: Peak Commit Charge. To optimally size your paging file you should start all the applications you run at the same time, load typical data sets, and then note the commit charge peak (or look at this value after a period of time where you know maximum load was attained). Set the paging file minimum to be that value minus the amount of RAM in your system (if the value is negative, pick a minimum size to permit the kind of crash dump you are configured for). If you want to have some breathing room for potentially large commit demands, set the maximum to double that number.

 

Some feel having no paging file results in better performance, but in general, having a paging file means Windows can write pages on the modified list (which represent pages that aren’t being accessed actively but have not been saved to disk) out to the paging file, thus making that memory available for more useful purposes (processes or file cache). So while there may be some workloads that perform better with no paging file, in general having one will mean more usable memory being available to the system (never mind that Windows won’t be able to write kernel crash dumps without a paging file sized large enough to hold them). (Source)

 

such as setting up paging files etc on a separate partition etc

There isn't any point in doing this if the partition is located on the same hard drive as the OS since it will increase seek times unnecessarily.

 

If you have lots of RAM (I have 8GB in my home pc) do you set it low?

My home PC has 32GB RAM and the page file is currently 4.8GB. I just let Windows manage it.

 

If you had hundreds of gigs of RAM, it would be a different matter, but 8GB RAM isn't a lot.

 

General practice is to either let the OS handle it or to set it to 1.5x the amount of physical RAM.

See article above.

Edited May 21, 2014 by Arthur

[HTCPCP]

If I set one, I usually set the min and the max to 1.5x the RAM. Home PC has 16GB RAM and a page file of 24GB. For normal machines that aren't heavily used, then Windows will deal with it, however if you are doing a lot on it, then set one manually. I have previously used a 20GB SSD for it, but I found that installing it in my netbook was far better use of it really.