AquinusLet me tell you something, dual 10c Xeons, 128GB of memory, and PCI-E Flash SSDs is a great reason to not use a page file. Simply put, you don't need it.

You should rephrase your comment "you don't need it" to instead say "I don't need it." There are cases where it is optimal to kill processes rather than allow them to run slowly, but that is an exception rather than the rule. I run a few critical servers running Debian, and it is a much bigger issue if the software on the server terminates due to lack of memory (and I get a call at 3:00AM saying the server isn't working and needs to be fixed immediately) than if the server is slightly slower due to it using a tiny fraction of the swap area, which I can deal with later in the day. You optimally want enough memory to never hit the swap area, but disk space is so cheap that in most cases you don't want to disable the safeguard because you don't want programs randomly closing.

OMG! I'm sorry. Please, don't fight :(

:toast:

As a follow up, even with 16GB of RAM I've kept a 1GB page file, if only for crash dumps and for the rare application than requires it.

The Von MatricesYou should rephrase your comment "you don't need it" to instead say "I don't need it." There are cases where it is optimal to kill processes rather than allow them to run slowly, but that is an exception rather than the rule. I run a few critical servers running Debian, and it is a much bigger issue if the software on the server terminates due to lack of memory (and I get a call at 3:00AM saying the server isn't working and needs to be fixed immediately) than if the server is slightly slower due to it using a tiny fraction of the swap area, which I can deal with later in the day. You optimally want enough memory to never hit the swap area, but disk space is so cheap that in most cases you don't want to disable the safeguard because you don't want programs randomly closing.

Yes. I will agree that there are cases where you may want swap for purposes like that, but normally a server can be configured not to use so much memory or to limit clients or connections to keep it within reason, but your right. If sudden termination of an application is not acceptable, then it's important. However if it is a memory leak, you can still run out of swap and run into the same issue or even hang up the server so bad that it becomes unresponsive which could be worse. So I think on the scale of 128GB of ram, a page file makes less sense. Even more so since the only storage available are PCI-E SSDs, but you're very right. There have been cases at work where having a swap file on a server has actually caused the server to lockup when swap got hit with the number of connections we have going into our web server. So I just want to point out that swap mitigates the issue, it doesn't resolve it.

There is no substitute to having enough physical memory for whatever task you throw at it, that's all I'm really trying to say.

AquinusAlso I have to produce sources but you don't provide any yourself? I would be careful with a double standard like that.

But I just gave you a link to MSDN... Still, I'll ask again, can YOU provide me with a source that tells me, as a C++ developer, never to use shared memory in Windows? I'm still waiting, because it's going to be a very controversial material that I (and thousands of Windows developers) would love to discuss.

AquinusYou're not writing an OS, that's not your job.

I'm not, but I'm using Win32 API capabilities, as millions of people around the planet do. It's a pretty straight-forward stuff, really. If this looks like "writing an OS" to you, then I don't know why are you even trying to call me and many other people incompetent developers.

AquinusI suspect you found a sub-optimal solution to your specific problem, but that doesn't mean it's the only answer or the most correct one.

Then tell me the right one. Where do I store my file mapping object on Windows? I need the exact copy of a specific area of memory that will be handled entirely by the OS (restricted read access, automated disposing), what's your solution?

AquinusRAID-5 calculates parity, something useless (and very slow) for swap space.

What are you talking about?.. Page file is not being separated or mirrored in RAID setups, it's placed on one drive. You can double check that with specific tools (for example, Dell provides one for their servers customers).

AquinusSSDs degrade the more you write to them

True. Those 0.03% of lifespan wasted over the course of 5 years mean a lot. Oh, but what if there's an update for your browser? What if it burns some of your precious little blocks?.. Come on, MSI installers can eat up something like 10 MiB during their work just to save all the log files and registry changes. Your Battlenet cache for Battlefield 4 will require something like 50 MiB when you get a new rank and a few ribbons just to display them on your screen...

Aquinusa dedicated temp file would be more suitable for your purposes.

You don't know what you're talking about. Windows, like any other OS will not allow you to just dump a direct copy of memory onto drive, it violates the encapsulation principle and exposes said data (which might be sensitive) to possible threats. And so you have a specific Win32 API call to tell the OS parameters such as buffer size, destination size and so on. If at any point your code fails to predict the size of second parameter (or the unexpected changes occur), this opens up a possibility of denial-of-service attack. If user terminates your app, again, said data won't be purged and will remain on your drive forever, open to all sorts of threats. Shared memory mechanism does check all this for you the fastest and most secure way possible, because it's already implemented by Windows creators.

AquinusThe way you describe your usage of swap space in your application tells me that you're using it wrong and that a dedicated temp file would be more suitable for your purposes.

Do you want to review my code? I'm open-minded towards this sort of stuff, if you are a fellow developer willing to help me to understand Windows memory management better, then why not.

I can tell you know your stuff.

As a total newbie and mostly a user that is concerned about HDD space, what would be the minimum amount of page file the would be wise to keep. I have 8 GiBs of ram and never, on idle, exceed 2 Gigs. I once or twice exceeded 4.
You do seem to know your stuff and, until aquinus forks out some sources, I'll have to turn to you for questions.

Thanks Samsung for reducing my nanometers.....

Adam NdjaAs a total newbie and mostly a user that is concerned about HDD space, what would be the minimum amount of page file the would be wise to keep. I have 8 GiBs of ram and never, on idle, exceed 2 Gigs. I once or twice exceeded 4.
You do seem to know your stuff and, until aquinus forks out some sources, I'll have to turn to you for questions.

If you have a limited storage space in your Windows 8/8.1 installation, you can set the maximum size of the paging file to be 1 GiB. This is absolutely safe to do and, in fact, is approved by Microsoft (support.microsoft.com/kb/2860880, skip to the "Automatic Memory Dump" paragraph). That way you can ensure that both the shared memory functionality and registering crash information will work as they were meant to be. The interesting thing here is that if you're using previous Windows versions, you don't have to assume that in some scenarios the automatic memory dump is being added to your pagefile (this mechanism wasn't introduced before Windows 8), so you'll probably be fine with just 896 (or even 768) MiB. Again, we're talking about the case when you are severely limited with you space (64/80/90/128 GiB SSDs, fixed virtual hard drives, etc), there's no real need to put any limitations on a regular system.

Now, in order to set the pagefile size restrictions you have to go to "Start" -> "Computer" -> "Properties", find there "Advanced system properties" link, click it and then navigate to the "Advanced" tab. There you'll see a "Virtual memory" panel with a "Change..." button. Once you clicked it, uncheck the "Automatically manage page file size for all drives" box, select "Custom size" radio button, type "256" into "Initial size (MB):" textbox and "1024" - into the "Maximum size (MB):" one.

By the way, do you use System Restore?.. I'm asking because this thing can eat up about 1.8 GiB in a matter of 3 programs being installed. It's allowed to use up to 2% of your drive's space by default (e. g. 10 GiB for a 500 GiB HDD), but you can manually lock it (via Command Prompt) to be, say, 2 GiB:

vssadmin Resize ShadowStorage /For=C: /On=C: /Maxsize=2GB

Constantine YevseyevBut I just gave you a link to MSDN... Still, I'll ask again, can YOU provide me with a source that tells me, as a C++ developer, never to use shared memory in Windows? I'm still waiting, because it's going to be a very controversial material that I (and thousands of Windows developers) would love to discuss.

You have yet to provide a link and I searched MSDN with no success for what you're describing.

Constantine YevseyevNow this is a very bold statement, mister. Are you a certified Windows developer? Or maybe you have a source that tells why such practice shouldn't be used? Mine says that it's perfectly fine, and it is Microsoft Developer Network.

And I assure you that it does. I explicitly state in my code the fact that I need my file mapping object to be put into the page file, and if I don't check for the ability of doing such thing at some point, your copy of application will crash, guaranteedly. Now, I don't have to completely rewrite this part of my product because some technical enthusiasts (like you) believe in possibility of achieving "speedup" because they turned something off in their Windows. I want my 0.7 GiB of in-memory infrastructure to be preserved in a specific area on your system drive and not in the RAM, for obvious reasons (and that's why this whole page file thing was created in the first place). You've got 16 GiB of RAM? Excellent! Not everybody does, though. Most of budget laptops (as well as old systems) come with only 2 GiB, then there are tablet devices, virtual machines and thin clients.

I like this term, "modern software".

Again, can you please tell me what are you trying to achieve by disabling page file? I just don't understand, I really don't. Swapping is a completely transparent mechanism that helps to prevent your RAM from over-bloating by data that your Task Manager thinks won't be needed on a high demand. You allow this thing to eat up as much processor time as it wants, purge your drive's cache, but when it comes to storing 30 MiB of changes history from your Microsoft Word... You just don't let it to! Why?..

There is no link in that entire post.

Constantine YevseyevI'm not, but I'm using Win32 API capabilities, as millions of people around the planet do. It's a pretty straight-forward stuff, really. If this looks like "writing an OS" to you, then I don't know why are you even trying to call me and many other people incompetent developers.

I'm calling you incompetent for how you're using it. Not for using it in the first place.

Constantine YevseyevThen tell me the right one. Where do I store my file mapping object on Windows? I need the exact copy of a specific area of memory that will be handled entirely by the OS (restricted read access, automated disposing), what's your solution?

In active memory. If you start running out, let Windows swap pages for you. Windows keeps track of the most commonly used pages and swaps out the least used one. Don't try to presume you can do a better job than the OS can.

Constantine YevseyevWhat are you talking about?.. Page file is not being separated or mirrored in RAID setups, it's placed on one drive. You can double check that with specific tools (for example, Dell provides one for their servers customers).

If you store a page file on a RAID drive, you are storing it on the entire RAID. For someone like me who has only RAID devices available in Windows, that's not feasible.

Constantine YevseyevTrue. Those 0.03% of lifespan wasted over the course of 5 years mean a lot. Oh, but what if there's an update for your browser? What if it burns some of your precious little blocks?.. Come on, MSI installers can eat up something like 10 MiB during their work just to save all the log files and registry changes. Your Battlenet cache for Battlefield 4 will require something like 50 MiB when you get a new rank and a few ribbons just to display them on your screen...

None of that stuff is stored in swap unless you have it enabled and you've run out of memory. That's my point. MSI installers and Battle.Net definitely don't require a page file.

Constantine YevseyevYou don't know what you're talking about. Windows, like any other OS will not allow you to just dump a direct copy of memory onto drive, it violates the encapsulation principle and exposes said data (which might be sensitive) to possible threats. And so you have a specific Win32 API call to tell the OS parameters such as buffer size, destination size and so on. If at any point your code fails to predict the size of second parameter (or the unexpected changes occur), this opens up a possibility of denial-of-service attack. If user terminates your app, again, said data won't be purged and will remain on your drive forever, open to all sorts of threats. Shared memory mechanism does check all this for you the fastest and most secure way possible, because it's already implemented by Windows creators.

This only re-emphsizes my point that you probably achieved what you wanted to with sub-optimal tools and the wrong way. I still don't understand why you need to use the page file directly and not just store shared data in memory. You can bash me all you want and call me names, but when push comes to shove, you're using the page file wrong.

Constantine YevseyevDo you want to review my code? I'm open-minded towards this sort of stuff, if you are a fellow developer willing to help me to understand Windows memory management better, then why not.

I can look at it, I can't say how much time I'll have to look at it. I guess I would be more interested in exactly what you need to use swap space for and where you do it. Without seeing it, I can only guess what you're doing. Are you writing this in VC++ or a different CLR language? I just don't recall ever needing to do anything with the swap file, even with shared memory. Granted, I did Windows development several years ago but this sounds like something that hasn't changed for a decade though.

Adam NdjaAs a total newbie and mostly a user that is concerned about HDD space, what would be the minimum amount of page file the would be wise to keep. I have 8 GiBs of ram and never, on idle, exceed 2 Gigs. I once or twice exceeded 4.
You do seem to know your stuff and, until aquinus forks out some sources, I'll have to turn to you for questions.

That's insulting considering I'm speaking from my education and my degree in Comp Sci and he has yet to provide a source either. It's simple really with how swap works. Swap moves unused data in memory to the disk to leave more open to whatever you're doing and swaps them back in if the machine needs them.

Swap space:
Benefit: You can use more memory than you have.
Your machine won't crash when you run out of physical memory.
There will be place to dump system debug logs.

Disadvantages: Increase disk I/O (and increases as you reach your memory limit.)
Due to I/O wait, the overall system will slow down. (Thrashing)
If you use enough swap space, you could make the machine unresponsive.

No swap space:
Benefit: Pages never leave active memory unless they're being free'd up.
Windows will stay in memory (I find minimizing/maximizing in and out of games to be faster with it disabled but that could be placebo effect.)
No page file will exists, which means you won't have a xGB file sitting on your disk.
SSDs don't like swap.* I'll explain this.

Disavantages:
You can't swap out other applications if you run out of physical memory. In other words, the OS will start killing processes to free up space.
Requires enough memory to hold your entire workload plus Windows.
High memory consumption for Windows. (3.5Gb, full load on boot but it never grows bigger.)

*: Now, the SSD bit. Your right that it's not a ton of writes, but keep in mind that memory pages are very small. Writing one Flash page on an SSD might write 16K pages, several times, where the flash drive might need to erase an entire page to write that data. That along is wasteful which is why it's never good to do this to an SSD as it results in write amplification.

What the page file is, most definitely not in dispute. How it's used in certain situations is what we're debating. Most people will want to leave it on, but there are reasons for turning it off.

AquinusDisabling the page file has the expectation that you will always be able to fit your workload which is everything running, including the OS, into memory.

I understand your point. I don't think you are wrong. I am just approaching the issue of SWAP/Page differently.

Constantine YevseyevBy the way, do you use System Restore?.. I'm asking because this thing can eat up about 1.8 GiB in a matter of 3 programs being installed. It's allowed to use up to 2% of your drive's space by default (e. g. 10 GiB for a 500 GiB HDD), but you can manually lock it (via Command Prompt) to be, say, 2 GiB

I already made it use <=2GiB on a 128 GiB SSD using CMD, thank you.

AquinusThat's insulting considering I'm speaking from my education and my degree in Comp Sci and he has yet to provide a source either.

I'm sorry, I didn't mean it like that, really, and your "debate" on SWAP really helps people understand it better, but since Easy Rhino and Constantine are erring on the side of caution and you are basically telling people that, on systems with low memory requirement compared to available memory, Page/Swap is better off, you have a lot more work to do to get me, as someone without any opinion on the matter to side with you.

on an other note, the reason I, for now and until further arguments make me change my mind, am keeping a small amount of page file is this:
For best performance, do not set the initial size to less than the minimum recommended size under Total paging file size for all drives. The recommended size is equivalent to 1.5 times the amount of RAM on your system. Usually, you should leave the paging file at its recommended size, although you might increase its size if you routinely use programs that require a lot of memory.

Right off of Microsoft.com; knowing that they are the authority on the matter of their own OS, I am inclined to listen to what they have to say regarding Page File.

Obviously, If you have a citeable source to answer :

Easy RhinoBut how do you know your OS isn't going to start killing processes or preventing writes to memory even with gigs of RAM available? You don't. You could have 8 gigs of RAM free (again, a complete waste) and if you launch an application that eats up 2 or 3 gigs your OS is going to immediately move stuff from memory to SWAP even though you have space in RAM free after the application launches.

then I would have basically no other qualm about disabling Page File.

AquinusSwap space:
Benefit: You can use more memory than you have.
Your machine won't crash when you run out of physical memory.
There will be place to dump system debug logs.

Disadvantages: Increase disk I/O (and increases as you reach your memory limit.)
Due to I/O wait, the overall system will slow down. (Thrashing)
If you use enough swap space, you could make the machine unresponsive.

No swap space:
Benefit: Pages never leave active memory unless they're being free'd up.
Windows will stay in memory (I find minimizing/maximizing in and out of games to be faster with it disabled but that could be placebo effect.)
No page file will exists, which means you won't have a xGB file sitting on your disk.
SSDs don't like swap.* I'll explain this.

Disavantages:
You can't swap out other applications if you run out of physical memory. In other words, the OS will start killing processes to free up space.
Requires enough memory to hold your entire workload plus Windows.
High memory consumption for Windows. (3.5Gb, full load on boot but it never grows bigger.)

*: Now, the SSD bit. Your right that it's not a ton of writes, but keep in mind that memory pages are very small. Writing one Flash page on an SSD might wright 16K, several times, where the flash drive might need to erase an entire page to write that data. That along is wasteful which is why it's never good to do this to an SSD as it results in write amplification.

What the page file is, most definitely not in dispute. How it's used in certain situations is what we're debating. Most people will want to leave it on, but there are reasons for turning it off.

I double that, that's absolutely true.

AquinusI can look at it, I can't say how much time I'll have to look at it. I guess I would be more interested in exactly what you need to use swap space for and where you do it. Without seeing it, I can only guess what you're doing. Are you writing this in VC++ or a different CLR language? I just don't recall ever needing to do anything with the swap file, even with shared memory. Granted, I did Windows development several years ago but this sounds like something that hasn't changed for a decade though.

Do you have some time later on? I can provide an example of real world application that (in my opinion) can benefit from explicitly using Pagefile, and, of course, show my implementation in code.

Easy RhinoGoodbye page file? Why would you remove a mechanicsm your OS uses to logically and intelligently manage memory?

This discussion needs a little bit of Comp Sci 101 in it.

You want your system to MAXIMIZE the usage of RAM. So if you have 16 gigs of RAM you want your OS to use ALL OF IT! Yes, you read that correct. Using only 15 gigs of the 16 gigs of RAM you purchases is wasting RAM!!! Why? Well the more data you can store in RAM the faster the system response. It is only logical.

So take that mentality and extrapolate it out to the page file/swap space argument.

If you want your OS to MAXIMIZE the amount of RAM you have in your rig then you want to ensure that the OS has all of the necessary tools required to MAXIMIZE said RAM. The page file/swap area is a mechanism to allow your OS to offload clean pages to your HDD which ineffect MAXIMIZES the amount of RAM you have. If you disable the page file or remove swap area then you have removed a mechanicsm that your OS uses to manage memory and it will instead have to start killing processes and preventing new write to memory!

So the page file/swap are argument is actually moot if you do the proper thing in the first place and make sure you utilize all of the RAM that is in your system.

I appreciate what a page file does but it's still not necessary if you have ample memory for everything. My desktop sports 32gb and my laptop 8gb, never memory problems on either with the swap file disabled. Windows uses my spare memory for lightening-fast cache on disk reads.

I prefer to eliminate unnecessary SSD writes and valuable storage space.