[OT] virtual memory

[deccan]

I run my comp with 512 mb RAM and no pagefile under Win XP fine too. I find that the only apps that need VM are resource-intensive 3-D games and graphics applications.

[Thermodyne]

Originally posted by Ruatha:

quote:

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Originally posted by Thermodyne:

No page file can cause problems. Some apps are written to use the page file for some data. This was done to free up system ram back in the day, but it still populates some code. Seti is an app that pages by default. IMHO 128megs is a ball park lower limit.

Still, if you don't use proggies that needs VM it's better to have none, as it then won't access the HD all the time.

All things ram are done in 32�s, 32-64-128-256-512-1024. Try to work the page file size in the same increments. It eases the addressing load on the CPU.

This I seriously question!
What should be the reason for the CPU to have "easier adress load" with 33554432 Bytes (32M) or 32M-some (ex 30M)?
Every adress between the 24 and the 32M range uses the same adress length (actually, above 16M it uses the same registers IIRC).
And a modern PC is made for large adress lenghts, so it should make no significant change to the internal workload for the computer what size the page file is, the only difference is in the drive handling. (And as I've stated far below in fragmantazion, aka also drive issues)
Right?
Enlighten me.

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32 bit memory buss.

[Thermodyne]

Originally posted by JoeViterbo:
The configuration of virtual memory even depends on your Version of windows. i think windows xp can even manage multiple page-files.

On rule to speed up things is: if you have two drives, put them on different controllers. Put your resource-consuming application to the drive where the page file is NOT. So using the page file and reloading software components won't interfere.

It is not a good solution to turn of the virtual memory. If you run multiple applications, your system will soon need it. Btw: Windows usually writes first the data to disk, that appears to be less important( e.g. idle apps etc )

quote:

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All things ram are done in 32�s, 32-64-128-256-512-1024. Try to work the page file size in the same increments. It eases the addressing load on the CPU.

I think the cpu runs in protected mode anyways. So every address is 32-Bit. There are no more "far" and "short" jumps. the cpu accesses each (even)adress at the same speed.

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XP and 2K can both manage more than one page file.

The reason for x32 page file size goes back to the original x86 code, and the function of the data buss. Take a look a the default page file size that windows sets. It will vary with the amount of ram installed, but it will always devide by 32.

A bench mark trick is to run a small page file. Just enough to meet the needs of the mark being run. Some times it will be 1meg or even 1/2 a meg. If you vary from x32, you will see it in the results.

[Ruatha]

Ok Thermo I see your point but it's still misguided.
If you change your page file to 32 M it doesn't matter if it 's anywhere between 16M+1 byte and 32M, it still has the same adress range, so having 32M doesn't make it go any faster than having 30M!
It's not some magic number, it's simply logic.
If you change from 32M to 32M+1 byte it can have some insignificant affact, hardly noticable I'd think but I'd agree that you might see it with a benchmark, haven't tested though, bit from say 24M to 29M or 32M it wouldn't have any aeffect, i e 32M page file is not faster then 24M pagefile.

The reason windows et it to "size dividable with 32" is that it want's the maximum amount possible if it's going above "size divided by 32" +1 byte, but youas a thinking human might hav ereasons not to set it that way.
And I've seen "not even dividable by 32" sizes if the free part of the disk doesn't allow it.
See?

[ August 02, 2003, 08:45: Message edited by: Ruatha ]

[Thermodyne]

Not exactly, but also true. As systems have gotten faster, page file virtual addressing has gotten more transparent, the load is a very small percentage of CPU time now. But the system still expects to see a size based on Base2 binary, starting with a 1 and then being all zeros. It will write each page as a 4kb page or slice of data. A simple way of seeing this is to enter 1 and a 0 into your electric slide rule, then look at the result. Repeat the process adding a zero each time. The results will be well known numbers.

Here is a link to the best place I know to get plain English answers on this stuff.

http://aumha.org/win5/a/xpvm.php

If you need more details, then we suffer the Chinese horror of the 1000 white papers 

[Ruatha]

That was a good link!

[Thermodyne]

Glad you liked it

In the long gone days of win98, this guy was the keeper of the grail for those of us who couldn�t deal with the white papers.