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Windows 7: Pagefile.sys

08 Feb 2010   #61
BunBun

Windows 7 Ultimate x64
 
 

Quote   Quote: Originally Posted by Tepid View Post
Oh god,, are we really still talking about the Page File?

Seriously,,, get it through your heads...... A PAGE FILE IS NECESSARY TO THE STABLE AND PROPER WORKINGS OF WINDOWS..... PERIOD.

This has been discussed and tried and worked through since the dawning of XP.
That and Static vs Dynamic Page File sizes as well as min/max sizes.

MS recommends... as do I...

Amount of Ram x 1.5 = Min
Amount of Ram x 3 = Max

If you have more than 4G of memory,,
then I do recommend setting Min and Max size to 4096
This really is about all that you need and on 32Bit is the max size file you can have anyway.

Quote:
1. Disabling the pagefile does not disable virtual memory.
Yes, It Does. I would avoid whoever told you that as a teacher.

Virtual memory - Wikipedia, the free encyclopedia


Quote:
And note the PF is rebuilt EVERY time the system reboots.
I will have to look into this further,,, but I think the only time this happens is when you have the registry key set to delete the pagefile on shutdown enabled. Then it will delete and rebuild the pagefile on every reboot. This can slow things down a bit for shutdown and restart. Good security practice does say to set this bit as the pagefile does hold data that can be accessed.
No where in that article does it say that disabling the pagefile disables virtual memory. There is a section of that article to deals with paged virtual memory which is how virtual memory is broken up and allocated but that has nothing to do with the pagefile. A pagefile is just a overflow that virtual memory uses when physical ram is running out and also a place holder for inactive data. I think you need to go re-read those books you keep reccomending to everyone. Also... a wiki link? Really? You call that proof?

Virtual memory as is explain in your link is simply a virtual address space assigned to applications. The OS then determines from that virtual space where things are actually located in physcial RAM. This is what allows multiple programs to share the same physical memory space. The pagefile is just a component that is used in the situation that there is no more availible physical space (and to store inactive or infrequently used data). If you run out out of physical space... bad things happen.

And no, the page file is not rebuilt everytime windows restarts. Unless, however, you have it set to do so with a registry tweak.

And if a system is so unstable without a pagefile how come I have been running for 4 years with XP, Vista, and now Win 7 without any issues and no page files?


My System SpecsSystem Spec
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08 Feb 2010   #62
Tepid

Win 7 Ultimate 32bit
 
 

Virtual Memory is the swap file, page file, it resides on disk, end of story.
Disable Page file you disable virtual memory.

Quote:
Extending memory to disk is a normal consequence of using virtual memory techniques, but could be done by other means such as overlays or swapping programs and their data completely out to disk while they are inactive. The definition of "virtual memory" is based on redefining the address space with a contiguous virtual memory addresses to "trick" programs into thinking they are using large blocks of contiguous addresses.
Paging - Wikipedia, the free encyclopedia

Quote:
Paging is an important part of virtual memory implementation in most contemporary general-purpose operating systems, allowing them to use disk storage for data that does not fit into physical Random-access memory (RAM). Paging is usually implemented as architecture-specific code built into the kernel of the operating system.
Quote:
When swapping is utilised a problem called "thrashing" can occur, where the computer spends too much time shuffling blocks of virtual memory between real memory and disks, and therefore appears to work slower. Better design of application programs can help, but ultimately the only cure is to install more real memory.
That last quote does not mean that you should install a ton of memory and disable Virtual Memory.

Also note..

Quote:
It is required, however, for the boot partition (i.e. the drive containing the Windows directory) to have a pagefile on it if the system is configured to write either kernel or full memory dumps after a crash. Windows uses the paging file as temporary storage for the memory dump. When the system is rebooted, Windows copies the memory dump from the pagefile to a separate file and frees the space that was used in the pagefile.
And...

While this is true,,,

Quote:
Windows 2000, XP, and Vista offer the DisablePagingExecutive registry setting, which controls whether kernel-mode code and data can be eligible for paging out.
This is also true....

Quote:
It is not uncommon to find 32 bit computers with 4 GiB of RAM, the maximum amount addressable without the use of PAE.
Swap space can be used beyond this 4 GiB limit, due to it being addressed in terms of pages rather than individual bytes.
While 32 bit programs will continue to be limited to the 4 GiB they're capable of addressing, because they each exist in their own virtual address space, a group of programs can together grow beyond this limit and into any available swap space.
Meaning that not everyone can run without a page file and it is not always wise to turn it off. It is there when and if needed and by turning it off you can actually limit a program from using what it is coded to need. Some apps require a page file (swap file) (ie. Virtual Memory). Becasue....

Quote:
Developed for multitasking kernels, virtual memory provides two primary functions:
  1. Each process has its own address space, thereby not required to be relocated nor required to use relative addressing mode.
  2. Each process sees one contiguous block of free memory upon launch. Fragmentation is hidden.
All implementations (excluding emulators) require hardware support. This is typically in the form of a memory management unit built into the CPU.
Systems that use this technique make programming of large applications easier and use real physical memory (e.g. RAM) more efficiently than those without virtual memory.
What that means is,,, it will utilize RAM more efficiently with Virtual Memory than without.

In other words,, they work together, not independently.

Yes, you can run a system without a page file, but in real world examples, it really is better to have one than not. I have been through this with many, and I have debated this and tested this since 2000. I have seen systems that appear to run fine without a pagefile, but have minor constant problems. I have seen systems with an improper pagefile set and run like crap, then you set the page file proper, and it runs great. I am not just saying these things to talk out my ass. I have done it, seen it, tested it, lived it.

My recommendation is to NOT disable the pagefile and effectively disable Virtual Memory.
Some apps do require it. And no, I can't name them specifically, But my bet is Excel and Access would be 2.


And actually,, here it is,.,....

Quote:
The simplest page table systems often maintain a frame table and a page table.
The frame table holds information about which frames are mapped. In more advanced systems, the frame table can also hold information about which address space a page belongs to, statistics information, or other background information.
The page table holds the mapping between a virtual address of a page and the address of a physical frame. There is also auxiliary information about the page such as a present bit, a dirty or modified bit, address space or process ID information, amongst others.
Secondary storage, such as a hard disk, can be used to augment physical memory. Pages can be swapped in and out of physical memory and the disk. The present bit can indicate what pages are currently present in physical memory or are on disk, and can indicate how to treat these different pages, ie. whether to load a page from disk and swap another page in physical memory out.
The dirty bit allows for a performance optimization. A page on disk that is swapped in to physical memory, then read from, and subsequently paged out again does not need to be written back to disk, since the page hasn't changed. (However, if the page was written to, its dirty bit would need to be set as additional work). This strategy requires that the swap file retain a copy of the page after it is swapped in to memory; therefore, in strictly literal terms, the operation isn't actually a "swap". When a dirty bit is not used, the swap file need only be as large as the instantaneous total size of all swapped-out pages at any moment. When a dirty bit is used, at all times some pages will exist in both physical memory and the swap file, and the simplest strategy is to make the swap file as large as the total virtual memory size, i.e. making room for every page regardless of whether it is in virtual memory. With large hard disks being relatively inexpensive today, it can be expected that most modern operating systems will do this and will make the swap file permanent in order to ensure that it is always available and contiguous (for optimal speed of access).
http://en.wikipedia.org/wiki/Page_table
My System SpecsSystem Spec
08 Feb 2010   #63
BugMeister

Windows10 Pro - 64Bit vs.10547
 
 

a comprehensive reply there, Tepid..

- deserves maximum rep points..
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08 Feb 2010   #64
BunBun

Windows 7 Ultimate x64
 
 

You are wasting your time. The only thing in all that that even refered to the pagefile itself is swapping and memory dumps. Both of which I have already discussed.

I would be interested in knowing what these "minor constant problems" are that you talk about. As in the past 4 years I have had no issues related to not having a page file on my main rig.

I repeat. Pageing is refering to how virtual memory breaks up the allocated data. Pageing does not mean the explicit use of the pagefile, that is called swapping.

Everything in that post is true about virtual memory. However turning off the pagefile does not turn off virtual memory and no where in your post does it explicitly say that turning off the pagefile turns off virtual memory.

It even states in your post virtual memory is nothing other then code (a tool) for a multi task kernel to use to allow multiple programs to function in the same memory space. Pageing is how this allocated memory is broken up and swapping is the act of swaping pages to and from the pagefile. Disabling the pagefile only disables swapping. Virtual memory is still active. Otherwise the system would fail and there are plenty of people running without pagefiles perfectly fine including myself. All it means is that if I run out of memory programs are going to crash and if I get a BSOD I will not have a memory dump to analyze.

And please stop useing wiki to prove a point. Wiki is nothing other then information collected by people like you or me and is no more substantial then the posts we are writing.

I do agree however that for the typical user the pagefile should be set to managed by the OS and left alone. Although that could be furthered a bit and said you should have a page file thats at least big enough for memory dumps (so phyiscal RAM + 300mb) but not so big as to cause the pagefile to perform worse due to greater area of random read/writes to disk and/or taking up more of the faster area of the drive that other applications could utilize. If it is too big, afterall, it is mostly wasted anyway. So for the majority of situations physical ram + 300mb should suffice. Also there used to be talk about setting min and max the same for performance reasons which I can see the point in but not sure if there is any merit in doing so.
My System SpecsSystem Spec
08 Feb 2010   #65
medeiom

Windows 7
 
 

Quote   Quote: Originally Posted by brady View Post
Over 4GB = you don't need a pagefile under 2GB = You need a pagefile and it should be set to double your RAM.

I totally agree!
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08 Feb 2010   #66
madtownidiot

 

I've been running 64bit 7 ultimate on this machine with no pagefile for the past couple days with no trouble. Even removed 4 GB of memory. Still no trouble. Tried putting a movie on an external display while COD 4 MW is loaded.. guess what... it works just fine.
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08 Feb 2010   #67
Tepid

Win 7 Ultimate 32bit
 
 

Virtual Address Space is not the same as Virtual Memory.
Virtual Memory uses Virtual Address Space, but they are not the same.
Disable the Pagefile, you disable Virtual Memory

And I am done debating this issue.
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08 Feb 2010   #68
Frostmourne

Windows 7 Ultimate x86-64
 
 

Quote   Quote: Originally Posted by Tepid View Post
Virtual Address Space is not the same as Virtual Memory.
Virtual Memory uses Virtual Address Space, but they are not the same.
Disable the Pagefile, you disable Virtual Memory

And I am done debating this issue.
Honestly, all you need to do is let windows adjust it. You run out of RAM, windows will swap it. Otherwise, LEAVE IT ALONE.
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08 Feb 2010   #69
Tepid

Win 7 Ultimate 32bit
 
 

I do have one more thing to add....


A properly set pagefile is better than no page file.
However, it may be necessary and even recommended that from time to time, you set the "Clear Pagefile on Shutdown" and reboot, to allow the page file to Delete and be recreated.

It is ok to leave this set and have it delete the pagefile every time you shutdown and reboot.
The only thing you might notice is a very slightly slower shutdown and start up.

This does 3 things,....

A. Defrags the page file , however you will want to fully defrag your system before and/or after doing this

B. If there is any corruption (bad data in the pagefile) it will correct it.

C. Gets rid of the old data that may be sitting in there, that you may not want people to be able to access. (ie. personal info)

Which some will argue is a reason to not have a pagefile..... that's not a good reason.

Now I am done with this debate.
My System SpecsSystem Spec
09 Feb 2010   #70
BunBun

Windows 7 Ultimate x64
 
 

Quote   Quote: Originally Posted by Tepid View Post
Virtual Address Space is not the same as Virtual Memory.
Virtual Memory uses Virtual Address Space, but they are not the same.
Disable the Pagefile, you disable Virtual Memory

And I am done debating this issue.
Virtual Memory encompasses many things including Virtual Address Space.

I think this little debate stems for the issue of a loosely defined term. When I think virtual memory I think:

"Logically-assigned memory that may or may not exist physically. Through the use of paging and the swap area, more memory can be referenced and allocated than actually exists on the system."

Disabling the pagefile changes how the OS deals with memory, slightly, however does not change how applications address memory. And only under certain circumstances will not having a pagefile ever be an issue.

That said, for the typical user in a typical setting the pagefile is left managed by the OS. I beleive I read Windows 7 now automatically sets the pagefile to just big enough for a memory dump if need be (physical RAM + ~300mb) and only makes it larger if absolutely neccessary.
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