virtual memory questions!

Q1)
Hi I am reading about virtual memory and I do not understand why the author
said .. "the areas that have NOT been used"
should not he has said "the areas that have been used"

RAM for areas that have not been used recently and copy them onto


quote
For example, if you load the operating system, an e-mail program, a Web
browser and word processor into RAM simultaneously, 32 megabytes is not
enough to hold it all. If there were no such thing as virtual memory, then
once you filled up the available RAM your computer would have to say,
"Sorry, you can not load any more applications. Please close another
application to load a new one." With virtual memory, what the computer can
do is look at RAM for areas that have not been used recently and copy them
onto the hard disk. This frees up space in RAM to load the new application.

/quote



Q2)

why when min and max size of virtual memory file identical we get better
performance?? can you explain that to me easier than this. thanks

quote

One trick that can improve the performance of virtual memory (especially
when large amounts of virtual memory are needed) is to make the minimum and
maximum sizes of the virtual memory file identical. This forces the
operating system to allocate the entire paging file when you start the
machine. That keeps the paging file from having to grow while programs are
running, which improves performance. Many video applications recommend this
technique to avoid pauses while reading or writing video information between
hard disk and tape.

/quote

-
leza stood up, at show-n-tell, and said:

Q1)
Hi I am reading about virtual memory and I do not understand why the
author said .. "the areas that have NOT been used"
should not he has said "the areas that have been used"

RAM for areas that have not been used recently and copy them
onto


quote
For example, if you load the operating system, an e-mail program, a
Web browser and word processor into RAM simultaneously, 32 megabytes
is not enough to hold it all. If there were no such thing as virtual
memory, then once you filled up the available RAM your computer would
have to say, "Sorry, you can not load any more applications. Please
close another application to load a new one." With virtual memory,
what the computer can do is look at RAM for areas that have not been
used recently and copy them onto the hard disk. This frees up space
in RAM to load the new application.

The above, only applies if you have 32MB of physical RAM. Nowadays, it's
almost impossible to use up physical RAM. In fact, Winblows will use the
swap file over physical memory. There are tweaks (NOT disabling the swap
file, BTW), that will force XP/2000 to use physical memory as opposed to
letting it sit there waiting for something that 'might' need it.


/quote



Q2)

why when min and max size of virtual memory file identical we get
better performance?? can you explain that to me easier than this.
thanks

This is because, with one set swap file size, the system is not constantly
resizing the swap file. It does impact performance. However, if you have
not so much memory and you use very memory intensive programs..this would
be ill advised. There is, rarely, any need to disable or limit the swap
file. Max out your memory, and 'fo-get about it'.



quote

One trick that can improve the performance of virtual memory
(especially when large amounts of virtual memory are needed) is to
make the minimum and maximum sizes of the virtual memory file
identical. This forces the operating system to allocate the entire
paging file when you start the machine. That keeps the paging file
from having to grow while programs are running, which improves
performance. Many video applications recommend this technique to
avoid pauses while reading or writing video information between hard
disk and tape.

/quote

--
Strontium

"I thought I'd lost you, somewhere. But you were, never, really
ever there at all. And, I want to get free..."

Howdy!

"leza" wrote in message
ble.rogers.com...
Q1)
Hi I am reading about virtual memory and I do not understand why the
author
said .. "the areas that have NOT been used"
should not he has said "the areas that have been used"

No, if it's been recently used, there's a chance it'll be used again
soon. If, however, it's NOT been recently used, there's a much BETTER
chance it WON'T be used any time soon.

So you copy out what you're not using.

Rather like having too much paperwork on your desk - you don't file
the stuff you're working with NOW, but you DO file last Thursday's expense
report ...

RwP

-
Gareth Church stood up, at show-n-tell, and said:

snip

Someone posted the tweak you refer to above (that is, to force
Windows to use only physical RAM until it runs out) in a newsgroup
the other day. I couldn't find it in my History, in googling for it I
found http://www.tweakxp.com/tweakxp/display.asp?id=1528.

This is not the tweak, that I was referring to. See he
http://kadaitcha.ath.cx/articles/performance.aspx
See the section: Memory Management. Ignore the Processor Scheduling
section, that follows it.



That is the
tweak, with a warning under it stating that it is false. This backs
up my belief that it is ridiculous. Firstly, I know how Windows
handles the swap file and based on that I know that using the swap
file when there is still physical RAM free does not hurt performance.
Secondly, no matter what people think about them, Microsoft isn't
stupid. They aren't going to hurt the performance of their OS by
hitting the swap file unneccesarily.

I left the swap file tweaking/optimization crowd years ago. As I've
already stated, it's best to let Windows manage the swap file (in my
opinion, anyway).


Also, no amount of swap file optimisation is going to give an
increase in performance that is 'awesome'. The hard drive is an order
of magnitude slower than RAM. There doesn't now and won't ever exist
a tweak that can make the swap file (hard disk) perform anything like
as fast as the RAM. So if you are hitting the swap file you are
killing your performace. The only way to fix this is to buy more RAM.

I am continually amazed at how much emphasis people place on swap file
optimisation (I'm not suggesting you are in this category). As an
analogy (since people don't seem to understand this), if your car
runs out of petrol, the solution is to get more petrol, not to
optimise how fast you run.

Gareth

--
Strontium

"I thought I'd lost you, somewhere. But you were, never, really
ever there at all. And, I want to get free..."

"Strontium" wrote in message
...
Someone posted the tweak you refer to above (that is, to force
Windows to use only physical RAM until it runs out) in a newsgroup
the other day. I couldn't find it in my History, in googling for it I
found http://www.tweakxp.com/tweakxp/display.asp?id=1528.

This is not the tweak, that I was referring to. See he
http://kadaitcha.ath.cx/articles/performance.aspx
See the section: Memory Management. Ignore the Processor Scheduling
section, that follows it.

Ok. I have seen one other swap file tweak before (but couldn't find it
again), but neither of those.

The wording of the first one (DisablePagingExecutive) is a bit misleading -
it suggests the kernel can be paged. Drivers and kernel code can be either
pageable or non-pageable, so the essentials can never be paged anyway. Since
the tweak only works with large amounts of RAM it seems of pretty limited
use to me. The more RAM you have, the less likely it is that any drivers or
kernel code will need to be paged out. It can also cause the system to hang
(http://support.microsoft.com/?kbid=323608).

The second tweak, as described, seemed pointless to me. When you close an
application it remains in memory. The writer of the article claims that
applications load faster after they were recently opened because of this
tweak. It, of course, happens because it is still in memory, and has nothing
to do with the tweak. Googling for LargeSystemCache revealed what changing
the setting really does
(http://support.microsoft.com/support.../q232/2/71.ASP). The
setting is used for servers, and only has an affect on network transfers.

I applied the two tweak and restarted anyway. I have 512MB RAM, so Windows
didn't hang. I opened half a dozen or so apps before applying the tweak,
then closed them and started them again. I then applied the tweak and did
the same thing. It was only a subjective test (which is the only one that
matters), but there was no difference in speed.

I left the swap file tweaking/optimization crowd years ago. As I've
already stated, it's best to let Windows manage the swap file (in my
opinion, anyway).

I agree. Microsoft know their OS better than anyone writing the tweak sites.
If they have a certain setting it's because either it makes no speed
difference or because it causes instability.

Gareth

-
Gareth Church stood up, at show-n-tell, and said:

"Strontium" wrote in message
...
Someone posted the tweak you refer to above (that is, to force
Windows to use only physical RAM until it runs out) in a newsgroup
the other day. I couldn't find it in my History, in googling for it
I found http://www.tweakxp.com/tweakxp/display.asp?id=1528.

This is not the tweak, that I was referring to. See he
http://kadaitcha.ath.cx/articles/performance.aspx
See the section: Memory Management. Ignore the Processor Scheduling
section, that follows it.

Ok. I have seen one other swap file tweak before (but couldn't find it
again), but neither of those.

The wording of the first one (DisablePagingExecutive) is a bit
misleading - it suggests the kernel can be paged. Drivers and kernel
code can be either pageable or non-pageable, so the essentials can
never be paged anyway. Since the tweak only works with large amounts
of RAM it seems of pretty limited use to me. The more RAM you have,
the less likely it is that any drivers or kernel code will need to be
paged out. It can also cause the system to hang
(http://support.microsoft.com/?kbid=323608).

The second tweak, as described, seemed pointless to me. When you
close an application it remains in memory. The writer of the article
claims that applications load faster after they were recently opened
because of this tweak. It, of course, happens because it is still in
memory, and has nothing to do with the tweak. Googling for
LargeSystemCache revealed what changing the setting really does
(http://support.microsoft.com/support.../q232/2/71.ASP). The
setting is used for servers, and only has an affect on network
transfers.

I applied the two tweak and restarted anyway. I have 512MB RAM, so
Windows didn't hang. I opened half a dozen or so apps before applying
the tweak, then closed them and started them again. I then applied
the tweak and did the same thing. It was only a subjective test
(which is the only one that matters), but there was no difference in
speed.

I was thinking the same thing, when I read the article. It made no sense,
to me. Once a program is loaded, into memory, it's there. I'm not really
an OS guru. I suppose I was a little naive about the implications of
first tweak. As for the first tweak, I'm just waiting to see if there is
any benefit. So far, I've not noticed any. But, my memory bandwidth is
pretty wide (400MHz). So, I doubt very seriously that I need to 'tweak'
anything in the first place. This box is pretty damned fast, as it is.
Now, if I can just slap some 7200 ATA100 drives in...wooooooooooo!



I left the swap file tweaking/optimization crowd years ago. As I've
already stated, it's best to let Windows manage the swap file (in my
opinion, anyway).

I agree. Microsoft know their OS better than anyone writing the tweak
sites. If they have a certain setting it's because either it makes no
speed difference or because it causes instability.

Gareth

--
Strontium

"I thought I'd lost you, somewhere. But you were, never, really
ever there at all. And, I want to get free..."