virtual memory questions!

  • Thread starter Thread starter leza
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leza

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"


<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>
 
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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"



<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.
Click to expand...

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
Click to expand...

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'.
 
Howdy!

leza 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"
Click to expand...

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
 
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