page file size

Sigh...

Again not saying that page files shouldn't be used. I'm curious as to the
internals of XP and how memory management works.


"Richard Urban" wrote in message
...
Try running AutoCAD or Photoshop without a page file. See how horrendously
slow these programs are when working with large files.

--
Regards,

Richard Urban

aka Crusty (-: Old B@stard :-)

If you knew as much as you think you know,
You would realize that you don't know what you thought you knew!


"axis" wrote in message
...
You could just say you don't know.

Don't get your panties in a buch. No one's criticizing anything, I'm just
trying to get more info about XP's behavior. Nothing wrong with that.

"Richard Urban" wrote in message
...
There is really nothing to discuss. Microsoft designed "their" operating
system that way. If you are, or know someone who is, smarter than the
Microsoft engineers - please, reverse engineer the system and post a
fix. Many would thank you for it.

Until then, just flow with the tide!

--
Regards,

Richard Urban

aka Crusty (-: Old B@stard :-)

If you knew as much as you think you know,
You would realize that you don't know what you thought you knew!


"axis" wrote in message
...
I understand the topics discussed on the page. My question still seems
appropriate. A page file is necessary so that all applications can be
allocated as much VM as they need, without exhausting physical RAM. In a
desktop with 1Gb of RAM, under normal usage I have yet to see memory
usage above 500mb, which begs the question why should I have a page
file, and why does XP complain when a small page file exists?

I'm happy to let windows manage the page file, this is just an academic
discussion.

"Will Denny" wrote in message
...
Hi

Please try the following article by Alex Nichol:

"Virtual Memory in Windows XP"
http://aumha.org/win5/a/xpvm.php

--

Will Denny
MS-MVP Windows Shell/User
Please reply to the News Groups.


"axis" wrote in message
...
Why do I still need a page file, even when I have 1 Gig of ram and my
RAM usage normally hovers around 3-400mb? If I set the page file to
be very small windows XP goes nuts. I understand the need for page
files in memory constrained situations, I would appreaciate some info
as to why one needs it even in a situation where we shouldn't need to
page any data our of memory to disk.

thanks

If you want greater insight into it, see the following:
http://support.microsoft.com/default...b;en-us;555223


"axis" wrote in message
...
Sigh...

Again not saying that page files shouldn't be used. I'm curious as to the
internals of XP and how memory management works.


"Richard Urban" wrote in message
...
Try running AutoCAD or Photoshop without a page file. See how
horrendously slow these programs are when working with large files.

--
Regards,

Richard Urban

aka Crusty (-: Old B@stard :-)

If you knew as much as you think you know,
You would realize that you don't know what you thought you knew!


"axis" wrote in message
...
You could just say you don't know.

Don't get your panties in a buch. No one's criticizing anything, I'm
just trying to get more info about XP's behavior. Nothing wrong with
that.

"Richard Urban" wrote in message
...
There is really nothing to discuss. Microsoft designed "their"
operating system that way. If you are, or know someone who is, smarter
than the Microsoft engineers - please, reverse engineer the system and
post a fix. Many would thank you for it.

Until then, just flow with the tide!

--
Regards,

Richard Urban

aka Crusty (-: Old B@stard :-)

If you knew as much as you think you know,
You would realize that you don't know what you thought you knew!


"axis" wrote in message
...
I understand the topics discussed on the page. My question still seems
appropriate. A page file is necessary so that all applications can be
allocated as much VM as they need, without exhausting physical RAM. In
a desktop with 1Gb of RAM, under normal usage I have yet to see memory
usage above 500mb, which begs the question why should I have a page
file, and why does XP complain when a small page file exists?

I'm happy to let windows manage the page file, this is just an
academic discussion.

"Will Denny" wrote in message
...
Hi

Please try the following article by Alex Nichol:

"Virtual Memory in Windows XP"
http://aumha.org/win5/a/xpvm.php

--

Will Denny
MS-MVP Windows Shell/User
Please reply to the News Groups.


"axis" wrote in message
...
Why do I still need a page file, even when I have 1 Gig of ram and
my RAM usage normally hovers around 3-400mb? If I set the page file
to be very small windows XP goes nuts. I understand the need for
page files in memory constrained situations, I would appreaciate
some info as to why one needs it even in a situation where we
shouldn't need to page any data our of memory to disk.

thanks

"axis" wrote:

Why do I still need a page file, even when I have 1 Gig of ram and my RAM
usage normally hovers around 3-400mb? If I set the page file to be very
small windows XP goes nuts. I understand the need for page files in memory
constrained situations, I would appreaciate some info as to why one needs it
even in a situation where we shouldn't need to page any data our of memory
to disk.

thanks


One big reason is that Windows uses the page file to satisfy the
memory address space requirements for the unused portions of memory
allocation requests.

By design Windows must identify specific memory address space for all
of the memory allocation requests that are issued, whether by Windows
itself, device drivers, or application programs. And all of these
typically ask for allocations that are larger that what is usually
needed under normal circumstances. So what Windows does is to
allocate RAM only to those portions of these requests that are
actually used and uses space in the page file for the unused portions.

Two points about this:
1. Mapping of these unused portions of memory requests to the page
file does not require any actual writing to the hard drive. All that
is need is entries in the memory mapping tables maintained by the CPU.
2. Windows Task Manager includes the swap file space allocated to
these unused ports as Page File Usage in the data reported on the
performance tab.

And if subsequent events result in the usage of previously requested
but unused memory then it can be instantaneously remapped from the
page file to an available location in RAM.

The bottom line, insofar as the current topic is concerned, is that
the existence of the page file will make the actual usage of your RAM
more efficient. Without a page file it is quite possible, indeed even
likely, that you would have a couple of hundred megabytes of RAM tied
up for memory that was requested but never used.


Also you need to be aware that Windows does use the page file for more
than just swapping out of memory content from RAM. It is also used
for:
a: System Failure Memory Dumps, unless you have this option
configured as "no memory dump". And in order for this option to be
usable there must be an existing page file on the boot drive that is
at least as large as the dump size option selected.
b: If you have multiple users configured on the computer and if you
have the "fast user switching" option in effect then Windows will use
the page file to "roll out" the memory contents of the previous user
when the machine is switched to a new user.

Hope this explains the situation.

Good luck


Ron Martell Duncan B.C. Canada
--
Microsoft MVP
On-Line Help Computer Service
http://onlinehelp.bc.ca

"The reason computer chips are so small is computers don't eat much."

Not the article I meant -- but with similar woding:
http://support.microsoft.com/default...b;en-us;308417

quote
- For best performance, do not set the initial size to less than the
minimum recommended size under Total paging file size for all drives.
...
- To delete a paging file, set both the initial size and the maximum
size to zero, or click No paging file. We strongly recommend that you do
not disable or delete the paging file.
/quote

--
Mikhail Zhilin
http://www.aha.ru/~mwz
Sorry, no technical support by e-mail.
Please reply to the newsgroups only.
======
On Sun, 6 Mar 2005 17:30:51 -0500, "axis" wrote:

I'll try to find the KB article you mention at the end of your post.

I don't know if anyone here can answer this question but -- with ample free
memory in a system, will XP still evict VM pages to the disk page file?

Thanks to everyone for their responses up to this point.

"Mikhail Zhilin" wrote in message
.. .
"How to configure paging files for optimization and recovery in Windows
XP"
http://support.microsoft.com/default...b;en-us;314482

quote
However, if you remove the paging file from the boot partition, Windows
cannot create a dump file (Memory.dmp) in which to write debugging
information in the event that a kernel mode Stop Error message occurs.
This could lead to extended downtime if you must debug to troubleshoot
the Stop error message.
/quote

And it is not the only disadvantage of disabling Virtual Memory. There
are the other related MS KB articles, and one of them (can't find fast
its number) warns specifically about avoiding disabling paging file even
when large amount of RAM is installed -- with the substantiation of this
statement.

--
Mikhail Zhilin
http://www.aha.ru/~mwz
Sorry, no technical support by e-mail.
Please reply to the newsgroups only.
======
On Sun, 6 Mar 2005 14:46:00 -0500, "axis" wrote:

Why do I still need a page file, even when I have 1 Gig of ram and my RAM
usage normally hovers around 3-400mb? If I set the page file to be very
small windows XP goes nuts. I understand the need for page files in memory
constrained situations, I would appreaciate some info as to why one needs
it
even in a situation where we shouldn't need to page any data our of memory
to disk.

thanks

And the CPU was designed to page, the motherboard chipsets were designed =
to page. Windows was designed to suit the hardware.

--=20
----------------------------------------------------------
http://www.microscum.com/mscommunity/
"Ron Martell" wrote in message =
...
"axis" wrote:
=20
Why do I still need a page file, even when I have 1 Gig of ram and my =
RAM=20
usage normally hovers around 3-400mb? If I set the page file to be =
very=20
small windows XP goes nuts. I understand the need for page files in =
memory=20
constrained situations, I would appreaciate some info as to why one =
needs it=20
even in a situation where we shouldn't need to page any data our of =
memory=20
to disk.

thanks=20

=20
One big reason is that Windows uses the page file to satisfy the
memory address space requirements for the unused portions of memory
allocation requests.
=20
By design Windows must identify specific memory address space for all
of the memory allocation requests that are issued, whether by Windows
itself, device drivers, or application programs. And all of these
typically ask for allocations that are larger that what is usually
needed under normal circumstances. So what Windows does is to
allocate RAM only to those portions of these requests that are
actually used and uses space in the page file for the unused portions.
=20
Two points about this:
1. Mapping of these unused portions of memory requests to the page
file does not require any actual writing to the hard drive. All that
is need is entries in the memory mapping tables maintained by the CPU.
2. Windows Task Manager includes the swap file space allocated to
these unused ports as Page File Usage in the data reported on the
performance tab.
=20
And if subsequent events result in the usage of previously requested
but unused memory then it can be instantaneously remapped from the
page file to an available location in RAM. =20
=20
The bottom line, insofar as the current topic is concerned, is that
the existence of the page file will make the actual usage of your RAM
more efficient. Without a page file it is quite possible, indeed even
likely, that you would have a couple of hundred megabytes of RAM tied
up for memory that was requested but never used.
=20
=20
Also you need to be aware that Windows does use the page file for more
than just swapping out of memory content from RAM. It is also used
for:
a: System Failure Memory Dumps, unless you have this option
configured as "no memory dump". And in order for this option to be
usable there must be an existing page file on the boot drive that is
at least as large as the dump size option selected.
b: If you have multiple users configured on the computer and if you
have the "fast user switching" option in effect then Windows will use
the page file to "roll out" the memory contents of the previous user
when the machine is switched to a new user.
=20
Hope this explains the situation.
=20
Good luck
=20
=20
Ron Martell Duncan B.C. Canada
--=20
Microsoft MVP
On-Line Help Computer Service
http://onlinehelp.bc.ca
=20
"The reason computer chips are so small is computers don't eat much."

In article , David Candy . wrote:
And the CPU was designed to page, the motherboard chipsets were designed =
to page. Windows was designed to suit the hardware.

Fire up task manager and pick the View/Select Columns tab. You'll be
able to add counters for memory-related usage and see which programs
are doing what. There's lots there I don't understand for Windows but
to me the interesting data is "PF delta" which is how many times in
the update interval an apllication needed a page what wasn't in it's
cache.

If there is a Page Fault it means that a page your application needs
isn't in the VM mapping tables and the OS takes over and updates the
VM tables, bringing a page in, if necessary. If you are short on real
memory that may mean forcing a physical write of some other page to
make room, so there were two disk I/O ops instead of zero. Even if a
page is in memory a PF takes CPU time away from useful work and slows
down your app. A "soft PF" means that the page was in memory and no
I/O was necessary to resolve. a "hard PF" means that I/O was
necessary. (anyone that can correct my terminology for WIndows please
chip in.)

As someone else described, each program has a "working set", the
minimum number pf pages it needs to do it's job with essentially zero
page faults (except for startup). The total size of the program is
frequently many times the working set size. As long as the total of
the working set for all running processes is less than the total real
memory you've got a system that is running efficiently.

I used to be able to quote microsecond figures for page fault handling
for certain mainframes. Soft faults were in microseconds, hard faults
are in milliseconds. (they still are.) In the day, I knew that 25 soft
faults per second meant we either had to tune our application mix
(might be expensive) or buy another chunk of memory (expensive.)

At least one major mainframe operating systems that was current in the
late 70's was even more tightly coupled to the VM architecture than
Windows is. The hardware and OS managed a data page of the file
system the same way it handled a memory page. All of memory was one
big cache. Top-20, fast as h**l for it's day.

Many PhD papers were were written in the 60's and 70's about memory
management strategies for virtual systems and there were loud
arguements at perfessional meetings about how they worked with
different process scheduling algoritms. Something we take for granted
now.

Now I'll return your TV channel to the 21st century......





--=20
----------------------------------------------------------
http://www.microscum.com/mscommunity/
"Ron Martell" wrote in message =
.. .
"axis" wrote:
=20
Why do I still need a page file, even when I have 1 Gig of ram and my =
RAM=20
usage normally hovers around 3-400mb? If I set the page file to be =
very=20
small windows XP goes nuts. I understand the need for page files in =
memory=20
constrained situations, I would appreaciate some info as to why one =
needs it=20
even in a situation where we shouldn't need to page any data our of =
memory=20
to disk.

thanks=20

=20
One big reason is that Windows uses the page file to satisfy the
memory address space requirements for the unused portions of memory
allocation requests.
=20
By design Windows must identify specific memory address space for all
of the memory allocation requests that are issued, whether by Windows
itself, device drivers, or application programs. And all of these
typically ask for allocations that are larger that what is usually
needed under normal circumstances. So what Windows does is to
allocate RAM only to those portions of these requests that are
actually used and uses space in the page file for the unused portions.
=20
Two points about this:
1. Mapping of these unused portions of memory requests to the page
file does not require any actual writing to the hard drive. All that
is need is entries in the memory mapping tables maintained by the CPU.
2. Windows Task Manager includes the swap file space allocated to
these unused ports as Page File Usage in the data reported on the
performance tab.
=20
And if subsequent events result in the usage of previously requested
but unused memory then it can be instantaneously remapped from the
page file to an available location in RAM. =20
=20
The bottom line, insofar as the current topic is concerned, is that
the existence of the page file will make the actual usage of your RAM
more efficient. Without a page file it is quite possible, indeed even
likely, that you would have a couple of hundred megabytes of RAM tied
up for memory that was requested but never used.
=20
=20
Also you need to be aware that Windows does use the page file for more
than just swapping out of memory content from RAM. It is also used
for:
a: System Failure Memory Dumps, unless you have this option
configured as "no memory dump". And in order for this option to be
usable there must be an existing page file on the boot drive that is
at least as large as the dump size option selected.
b: If you have multiple users configured on the computer and if you
have the "fast user switching" option in effect then Windows will use
the page file to "roll out" the memory contents of the previous user
when the machine is switched to a new user.
=20
Hope this explains the situation.
=20
Good luck
=20
=20
Ron Martell Duncan B.C. Canada
--=20
Microsoft MVP
On-Line Help Computer Service
http://onlinehelp.bc.ca
=20
"The reason computer chips are so small is computers don't eat much."


--

a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.