Page file

I have Windows XP Pro and two gigs of RAM. Do I still need a page file?
Thanks for your reply

"Jaap Telschouw" wrote in message
...
I have Windows XP Pro and two gigs of RAM. Do I still need a page file?
Thanks for your reply

You never actually 'need' a page file, it just prevents applications /
windows from crashing / hanging when windows runs out of RAM.

I have 1.5GB RAM and I have my page file turned off. This makes things run
faster as everything loaded is in RAM and never swapped out to hard disk.
Beware, though if you use memory intensive applications and the RAM becomes
full, either the application or Windows will crash.

Jaap Telschouw wrote:

I have Windows XP Pro and two gigs of RAM. Do I still need a page file?

Yes, its safer to have one which doesnt get used much at all.

XP can be a little stupid with no page file at all.

On Thu, 18 Jan 2007 14:45:43 +0100, "Jaap Telschouw"
wrote:

I have Windows XP Pro and two gigs of RAM. Do I still need a page file?
Thanks for your reply



It depends on your specific use of the system. Typically
applications allocate memory they won't ever use, only some
portion of it is ever needed, but must be able to allocate
it anyway. If what you run (total of all apps/etc), never
had need to allocate more than the physical memory installed
in the system then you could run without a pagefile.

If the system use/jobs are non-critical you can just turn it
off and see how it goes, but the moment you have an out of
memory related error, it's time to re-enable pagefile and
check that the problem went away in the same scenario.

Some apps make more efficient use of memory than others too
(for same tasks), so if the goal was improving performance
there are more ways to get there than just disabling
pagefile.

Since most people buy large(r) amounts of memory in
anticipation of running larger jobs rather than to be able
to disable the pagefile, most people would not be able to
disable pagefile without some issues... but it is possible
to run fine without one, given sufficient physical memory.

(message (Hello 'GT)
(you :wrote n '(Thu, 18 Jan 2007 17:37:39 -0000))
(

G I have 1.5GB RAM and I have my page file turned off. This makes things
G run faster as everything loaded is in RAM and never swapped out to hard
G disk.

this is not really true..
there are pages in memory that are loaded from EXE and DLL files, windows in
some cases can forget about them -- replace those pages by file cache, for
example, and they will be read back later.
if you're using file system very intensively, you can still see some page
faults (and delays) of applications loading back..
you can see this in task manager, if you enabled 'page faults' column, does
it say 0 for all columns?
page file is for pages that are allocated in memory and not backed by some
file. actually, i think there are pages that are allocated, but never used,
so some small amount of paging files can speedup things -- there will be
more place for caches..
i have 2 GB of RAM and have some small page files. i believe it's more
optimal, but i can't be sure..

G Beware, though if you use memory intensive applications and the RAM
G becomes full, either the application or Windows will crash.

it's very unlinkely for windows to crash. memory allocation just fails, and
actually application can handle this gracefully.
btw there's one more reason to keep page file size at minimum -- some
applications erroneosly allocate tons of RAM, and with large pagefile
swapping make system non-responsible. with less or no pagefile, those
application will simply honestly report failure..

)
(With-best-regards '(Alex Mizrahi) :aka 'killer_storm)
"People who lust for the Feel of keys on their fingertips (c) Inity")

On Thu, 18 Jan 2007 21:48:13 +0200, "Alex Mizrahi"
wrote:

(message (Hello 'GT)
(you :wrote n '(Thu, 18 Jan 2007 17:37:39 -0000))
(

G I have 1.5GB RAM and I have my page file turned off. This makes things
G run faster as everything loaded is in RAM and never swapped out to hard
G disk.

this is not really true..
there are pages in memory that are loaded from EXE and DLL files, windows in
some cases can forget about them -- replace those pages by file cache, for
example, and they will be read back later.
if you're using file system very intensively, you can still see some page
faults (and delays) of applications loading back..
you can see this in task manager, if you enabled 'page faults' column, does
it say 0 for all columns?
page file is for pages that are allocated in memory and not backed by some
file. actually, i think there are pages that are allocated, but never used,
so some small amount of paging files can speedup things -- there will be
more place for caches..

No, pages allocated but never used will not matter, a small
amount of paging does NOT speedup anything. The system
either has enough (real) memory that it doesn't have to page
out (which is ALWAYS faster "IF" the use allows, if it
doesn't require too much memory), or it doesn't have enough
memory, in which case you may have faults, errors, but we
can ignore the error conditions with the simple concept of
"don't configure a system such that it has them".



i have 2 GB of RAM and have some small page files. i believe it's more
optimal, but i can't be sure..

If the total amount of allocated memory is beyond 2GB, yes
it is more optimal. If the total amount is below 2GB, it
may depend on how much of a benefit you would see from
having a larger filecache (IF you adjust Windows memory
management to have one, this is not a default installation
condition), it is quite possible the larger filecache
reduces rereads from HDD, more than the I/O to HDD from
slight pagefile use. In the end, the goal is still the
same- based on the specific uses of the system, to minimize
access to the HDD.



G Beware, though if you use memory intensive applications and the RAM
G becomes full, either the application or Windows will crash.

it's very unlinkely for windows to crash. memory allocation just fails, and
actually application can handle this gracefully.
btw there's one more reason to keep page file size at minimum -- some
applications erroneosly allocate tons of RAM, and with large pagefile
swapping make system non-responsible. with less or no pagefile, those
application will simply honestly report failure..

If you're going to have a pagefile active, it should be
large enough to handle the entire memory allocation from
applications. Allocated memory that isn't used is not
going to be so much of an undue burden on the system, but I
suppose it does depend on exactly what the app is trying to
do, if it is excessively buggy then the solution is to
replace the app.

(message (Hello 'kony)
(you :wrote n '(Thu, 18 Jan 2007 16:23:14 -0500))
(

k No, pages allocated but never used will not matter, a small
k amount of paging does NOT speedup anything. The system
k either has enough (real) memory that it doesn't have to page
k out (which is ALWAYS faster "IF" the use allows, if it
k doesn't require too much memory),

it might be true if i run a single application cosuming gigabytes of RAM,
but usage patterns on modern desktop computers are not like that.
i have lots of applications running (74 processes for 2 users), and i don't
need all the processes all the time, certainly. i'm even running two OSes
simultaneously -- Linux in vmware, but i'm working with that Linux from time
to time.
so, i think they'll better be swapped out. as i've said, if some active
process will need more RAM, or if some file operations will need be cached,
Windows will swap out that processes anyway -- but it will swap out it's DLL
and EXE pages if it cannot swap allocated memory to pagefile.
RAM is just a cache for data -- some data is backed by files (executable or
filemappings), some is backed by pagefiles, and some will be not backed by
anything. OS might optimize better when it has flexibility to swap out some
allocated memory that is not used to pagefile. certainly, OS might be wrong
in it's optimizations, so it's questionable..
if you disable pagefile, you give priority to data that is explicitly
allocated by applications that is not backed by anything -- so it's not
swapped even if it's not used because there's no place for it. at same time
some data that is more-or-less actively used -- for example, file cache that
caches filesystem structure MFT -- can be swapped out.

?? i have 2 GB of RAM and have some small page files. i believe it's more
?? optimal, but i can't be sure..

k If the total amount of allocated memory is beyond 2GB, yes
k it is more optimal. If the total amount is below 2GB, it
k may depend on how much of a benefit you would see from
k having a larger filecache (IF you adjust Windows memory
k management to have one, this is not a default installation
k condition), it is quite possible the larger filecache
k reduces rereads from HDD, more than the I/O to HDD from
k slight pagefile use. In the end, the goal is still the
k same- based on the specific uses of the system, to minimize
k access to the HDD.



?? it's very unlinkely for windows to crash. memory allocation just
?? fails, and actually application can handle this gracefully. btw
?? there's one more reason to keep page file size at minimum -- some
?? applications erroneosly allocate tons of RAM, and with large pagefile
?? swapping make system non-responsible. with less or no pagefile, those
?? application will simply honestly report failure..

k If you're going to have a pagefile active, it should be
k large enough to handle the entire memory allocation from
k applications.

why?

)
(With-best-regards '(Alex Mizrahi) :aka 'killer_storm)
"People who lust for the Feel of keys on their fingertips (c) Inity")

On Fri, 19 Jan 2007 00:13:41 +0200, "Alex Mizrahi"
wrote:

(message (Hello 'kony)
(you :wrote n '(Thu, 18 Jan 2007 16:23:14 -0500))
(

k No, pages allocated but never used will not matter, a small
k amount of paging does NOT speedup anything. The system
k either has enough (real) memory that it doesn't have to page
k out (which is ALWAYS faster "IF" the use allows, if it
k doesn't require too much memory),

it might be true if i run a single application cosuming gigabytes of RAM,
but usage patterns on modern desktop computers are not like that.

Wrong. Usage patterns do not change it and multiple apps
merely have additive memory load which is still weighed
against what the physical memory can support, or can't.

If there is enough physical memory, enabling a pagefile will
ALWAYS, no matter what other variable, be slower. For the
(nonspecific and thus unprovable) "usage patterns on modern
desktop", it could easily be that there is not enough
physical memory - hence why a pagefile is enabled by
default. Only the user can determine that it isn't needed.



i have lots of applications running (74 processes for 2 users), and i don't
need all the processes all the time, certainly. i'm even running two OSes
simultaneously -- Linux in vmware, but i'm working with that Linux from time
to time.
so, i think they'll better be swapped out.


IF you don't have enough physical memory to accomdate all
the rest without swapping, yes. That's not same as having
enough and paging it out for no good reason.


as i've said, if some active
process will need more RAM, or if some file operations will need be cached,
Windows will swap out that processes anyway -- but it will swap out it's DLL
and EXE pages if it cannot swap allocated memory to pagefile.
RAM is just a cache for data -- some data is backed by files (executable or
filemappings), some is backed by pagefiles, and some will be not backed by
anything. OS might optimize better when it has flexibility to swap out some
allocated memory that is not used to pagefile. certainly, OS might be wrong
in it's optimizations, so it's questionable..
if you disable pagefile, you give priority to data that is explicitly
allocated by applications that is not backed by anything -- so it's not
swapped even if it's not used because there's no place for it. at same time
some data that is more-or-less actively used -- for example, file cache that
caches filesystem structure MFT -- can be swapped out.

It is true that some data is needed later, or more
frequently, and some isn't. That does not change the fact
that swapping out data is going to be slower if there was no
other use for remaining physical memory. You are
arbitrarily presuming there would be, and indeed sometimes
there is, but that is not the same as a random idea about it
being faster to page out without the specific situation of
having insufficient physical memory to hold it all.





?? i have 2 GB of RAM and have some small page files. i believe it's more
?? optimal, but i can't be sure..

k If the total amount of allocated memory is beyond 2GB, yes
k it is more optimal. If the total amount is below 2GB, it
k may depend on how much of a benefit you would see from
k having a larger filecache (IF you adjust Windows memory
k management to have one, this is not a default installation
k condition), it is quite possible the larger filecache
k reduces rereads from HDD, more than the I/O to HDD from
k slight pagefile use. In the end, the goal is still the
k same- based on the specific uses of the system, to minimize
k access to the HDD.



?? it's very unlinkely for windows to crash. memory allocation just
?? fails, and actually application can handle this gracefully. btw
?? there's one more reason to keep page file size at minimum -- some
?? applications erroneosly allocate tons of RAM, and with large pagefile
?? swapping make system non-responsible. with less or no pagefile, those
?? application will simply honestly report failure..

k If you're going to have a pagefile active, it should be
k large enough to handle the entire memory allocation from
k applications.

why?

Because that's the whole point of a pagefile, to virtually
provide memory that's not there, not to cause the app to not
have enough even WITH it. Allocation that isn't used is not
a bad thing, it was that it used the HDD at all that causes
the significant performance penalty, even worse when the
system has only one HDD in it as many do.

kony wrote
Alex Mizrahi wrote

No, pages allocated but never used will not matter, a small
amount of paging does NOT speedup anything. The system
either has enough (real) memory that it doesn't have to page
out (which is ALWAYS faster "IF" the use allows, if it
doesn't require too much memory),

it might be true if i run a single application cosuming gigabytes of RAM,
but usage patterns on modern desktop computers are not like that.

Wrong. Usage patterns do not change it and multiple apps
merely have additive memory load which is still weighed
against what the physical memory can support, or can't.

If there is enough physical memory, enabling a pagefile
will ALWAYS, no matter what other variable, be slower.

Wrong with an OS that has enough of a clue to not use it
unless its necessary because there isnt enough physical memory.

And even with one that isnt smart enough to always do that,
you havent established that what minimal use of the pagefile
it does do when there is enough physical memory does slow
things down any anyway, most obviously when what minimal
use it does make of the page file is in the background etc.

For the (nonspecific and thus unprovable) "usage patterns
on modern desktop", it could easily be that there is not
enough physical memory - hence why a pagefile is enabled
by default. Only the user can determine that it isn't needed.

Wrong, the OS obviously can.

i have lots of applications running (74 processes for 2 users),
and i don't need all the processes all the time, certainly. i'm
even running two OSes simultaneously -- Linux in vmware,
but i'm working with that Linux from time to time.
so, i think they'll better be swapped out.

IF you don't have enough physical memory to accomdate
all the rest without swapping, yes. That's not same as
having enough and paging it out for no good reason.

Pity about when the pagefile is just used to provide
faster access to the read only files on the hard drive.

as i've said, if some active
process will need more RAM, or if some file operations will need be
cached, Windows will swap out that processes anyway -- but it will
swap out it's DLL and EXE pages if it cannot swap allocated memory
to pagefile.
RAM is just a cache for data -- some data is backed by files
(executable or filemappings), some is backed by pagefiles, and some
will be not backed by anything. OS might optimize better when it has
flexibility to swap out some allocated memory that is not used to
pagefile. certainly, OS might be wrong in it's optimizations, so
it's questionable..
if you disable pagefile, you give priority to data that is explicitly
allocated by applications that is not backed by anything -- so it's
not swapped even if it's not used because there's no place for it.
at same time some data that is more-or-less actively used -- for
example, file cache that caches filesystem structure MFT -- can be
swapped out.

It is true that some data is needed later, or more
frequently, and some isn't. That does not change
the fact that swapping out data is going to be slower
if there was no other use for remaining physical memory.

Not if that is done in the background and its never used from the file.

You are arbitrarily presuming there would be, and indeed
sometimes there is, but that is not the same as a random
idea about it being faster to page out without the specific
situation of having insufficient physical memory to hold it all.

You are arbitrarily presuming that an OS which does minimally
use a page file when there is enough physical ram, that that
minimal use of the page file has any effect on the speed of ops.

You dont know that.

i have 2 GB of RAM and have some small page files.
i believe it's more optimal, but i can't be sure..

If the total amount of allocated memory is beyond 2GB, yes
it is more optimal. If the total amount is below 2GB, it
may depend on how much of a benefit you would see from
having a larger filecache (IF you adjust Windows memory
management to have one, this is not a default installation
condition), it is quite possible the larger filecache
reduces rereads from HDD, more than the I/O to HDD from
slight pagefile use. In the end, the goal is still the
same- based on the specific uses of the system, to minimize
access to the HDD.

it's very unlinkely for windows to crash. memory allocation just
fails, and actually application can handle this gracefully. btw
there's one more reason to keep page file size at minimum -- some
applications erroneosly allocate tons of RAM, and with large
pagefile swapping make system non-responsible. with less or no
pagefile, those application will simply honestly report failure..

If you're going to have a pagefile active, it should be large
enough to handle the entire memory allocation from applications.

Wrong.

why?

Because that's the whole point of a pagefile,

Nope.

to virtually provide memory that's not there,

It isnt the ENTIRE MEMORY ALLOCATION FROM THE APPS
that matters, its the excess over the physical memory that matters.

not to cause the app to not have enough even WITH it.
Allocation that isn't used is not a bad thing,

It can be speed wise if that page file space has to be allocated and is never used.

In spades when you have chosen to run without a page file.

it was that it used the HDD at all that
causes the significant performance penalty,

ONLY if that allocated memory is ever actually used.

even worse when the system has only one HDD in it as many do.

In spades.

(message (Hello 'kony)
(you :wrote n '(Thu, 18 Jan 2007 19:51:03 -0500))
(

k If there is enough physical memory, enabling a pagefile will
k ALWAYS, no matter what other variable, be slower.

how do you measure 'enough' or 'not enough' memory?
i've already said you, that RAM is used as cache for files and filesystem
structures.
thus, it's not possible to say if it's enough or not -- just, with more RAM
it would be faster, with less it would be slower.

if i'm doing some intensive file operations, (for example, compilation of
large C++ project), i'd like as much file cache be used as possible. at same
time, i don't care about other applications being in RAM -- i'd prefer them
to be swapped out, to give more RAM to file cache. compilation can go for 10
minutes, in some cases of extra large project for hours. additional file
cache might significantly improve performance.

yes, IDE, firefox and other stuff will need to be swapped back after that,
but i think i won't mind some three-second delay, if that helped to speed up
thing. (i'd say that this delay is inevitable -- windows can 'forget' about
EXEs and DLLs being loaded in favour of file cache).

yes, certainly getting more RAM would help. but if 1 GB RAM + swap will give
me aprox same performace as 2 GB RAM -- why should i pay more?

)
(With-best-regards '(Alex Mizrahi) :aka 'killer_storm)
"People who lust for the Feel of keys on their fingertips (c) Inity")