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Old 11-22-2005, 01:56 AM   #1 (permalink)
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Default pagefile.sys and virtual memory

Hello
is the pagefile.sys the virtual memory. in that case if i allocate 1 GB of memory to pagefile.sys, am i allocating 1 GB of memory to virtual memory?
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Old 11-22-2005, 04:12 AM   #2 (permalink)
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yes
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Old 11-22-2005, 11:55 AM   #3 (permalink)
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And why in the world would you want a 1 gig swap file? How much system ram are you running? If you are 1+ gigs you can set the page file to 64megs and it will be very lonely. With a lot of RAM the page file will not be routinely accessed unless you are running one humongous CAD program or the like that sucks up a whole bunch of RAM!!
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Old 11-22-2005, 11:58 AM   #4 (permalink)
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Old 11-22-2005, 12:50 PM   #5 (permalink)
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Old 11-22-2005, 03:56 PM   #6 (permalink)
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you should set your page file for 1.5 times your ram size
so if you have 500M of ram your page file would be 750 meg
also the page file should be on another drive.
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Old 11-22-2005, 05:15 PM   #7 (permalink)
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naaaaa........the page file is only accessed when program access via HAL in XP has exceeded the "free memory" present at any time on the fly. If any home PC as a gig or more of memory, the page file is nearly never accessed. Mine is set a 32mb and I run a page file running history in windows.....guess what....with 2 gigs of DDR 400................no page file history in the past 6 months!!!!! Tractorboy, you are right about the location. And it should be set on a slave and even it's own small partition so that the defrag issues for that file are minimalized but the size of the page file should not be that big with a gig or more of memory...not that setting it high is going to slow anything down because it will be rarely if ever accessed and then minimally if you are using a memory ravenous program of some sort.
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Old 11-22-2005, 05:33 PM   #8 (permalink)
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Old 11-22-2005, 11:13 PM   #9 (permalink)
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Depends on what the system is used for. If, for example, you have SQL running then that would be a very bad idea. Some programs will also allocate large amounts of memory for themselves, even if they are not used. SQL does this, although there are stored procedures and advanced configurations so it only uses so much memory but then you have to know what your doing with it and hope you have small tables/dbases.


Here's something found on IT pro site:



A. Any program that runs on an Intel 386 or later system can access up to 4GB of RAM, which is typically far more memory than is physically available on a machine. To make up for the missing physical memory, the OS creates a virtual address space, known as virtual memory, in which programs can see their own 4GB memory space. (This virtual address space consists of two 2GB portions--one for the program and one for the OS.) The OS is responsible for allocating and mapping to physical RAM those parts of the program or memory that are currently active.

To work around a machine's physical RAM limitations, a local file known as the pagefile stores pages (in 4KB increments) that aren't in use. (One installation can have multiple pagefiles.) When a program needs to access a page from the pagefile, the OS generates a page fault that instructs the system to read the page from the pagefile and store it in memory. Because disks are much slower than memory, excessive page faults eventually degrade performance. A computer's RAM consists of two sections. The first section, the non-paged area, stores core OS information that's never moved to the pagefile. The second section, the paged area, contains program code, data, and inactive file system cache information that the OS can write to the pagefile if needed.

Although the discussion so far might lead you to believe that Windows stores only active code and data (plus the core OS) in physical RAM, Windows actually attempts to use as much RAM as possible. Often, the OS uses RAM to cache recently run programs so that the OS can start these programs more quickly the next time you use them. If the amount of available free RAM on your computer is low and an application needs physical RAM, the OS can remove from RAM pages of memory used to cache recently run programs or move non-active data pages to the pagefile.

So, if you have a lot of RAM, you don't need a pagefile, right? Not necessarily. When certain applications start, they allocate a huge amount of memory (hundreds of megabytes typically set aside in virtual memory) even though they might not use it. If no pagefile (i.e., virtual memory) is present, a memory-hogging application can quickly use a large chunk of RAM. Even worse, just a few such programs can bring a machine loaded with memory to a halt. Some applications (e.g., Adobe Photoshop) will display warnings on startup if no pagefile is present.

My advice, therefore, is not to disable the pagefile, because Windows will move pages from RAM to the pagefile only when necessary. Furthermore, you gain no performance improvement by turning off the pagefile. To save disk space, you can set a small initial pagefile size (as little as 100MB) and set a high maximum size (e.g., 1GB) so that Windows can increase the size if needed. With 1GB of RAM under normal application loads, the pagefile would probably never need to grow.

If you want to prevent Windows from moving any core OS kernel or driver files to the pagefile, perform the following steps:

1. Start a registry editor (e.g., regedit.exe).
2. Navigate to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Session Manager\Memory Management registry subkey.
3. Set the DisablePagingExecutive registry entry to 1.

If you want to determine how much of the pagefile is actually being used, you can download Bill James' various pagefile utilities, which are available at this Web site. Among these tools is a WinXP-2K_Pagefile.vbs script that tells you the current and maximum pagefile usage.



Also note that doesn't mean you need a large page file. If it is to high a page file then that may hinder performance. Also, setting min and max may be helpful as then the o/s pagefile is not dynamic (constant increase and decrease in the pagefiles structural size takes a very small performance hit).
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Old 11-23-2005, 08:12 AM   #10 (permalink)
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I would not turn off your page file
do control alt delete
task manager
then performance, you can see your page file usage
..as PF usage
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