Re: 1GB of RAM, isnt it enough?
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Date: 02/01/05
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Date: Mon, 31 Jan 2005 19:13:03 -0500
On Mon, 31 Jan 2005 13:29:05 -0600, perris
<perris.1jqn82@no-mx.forum.osnn.net> wrote:
>
>Najm Wrote:
>>
>> Is one obliged to use virtual memory even if the Ram is more than
>> enough?
>> Thanks
>
>xp is a virtual memory operating system and there is nothing you could
>do about that except crack the os and recompile the kernel
Oh really, then why is it that control
panel/system/Advanced/Advanced/virtual memory/change allows you to set all
drives to "no paging file". There will be consequences if more address
space is needed than is available in RAM but the system will work. If
virtual memory is not needed, there will be no consequences.
>
>All memory seen under the NT family of OS's is virtual memory,
>(Processes access memory through their virtual memory address space)
>there is no way to address RAM directly!!
This is true but you can effectively reference RAM directly by creating an
appropriate set of page table entries which happens if there is no paging
file.
>open taskmanager, and count all the memory your processes are
>calling...this adds up to more then your gig of memory
Perhaps - shows how extremely inefficient modern code has become. A
properly written O/S could do what Windows XP does with less than 1% of the
CPU and RAM resources used by XP and its applications.
Before you jump all over me, I have written supercomputer operating systems
(including virtual memory systems - and their pagers) that researchers have
used to substantially advance the US aeronautics and space program and I
know what can be done. And yes, supercomputers these days run UNIX and No,
I didn't write Unix but this has not always been so (I'm a long retired
guy.) Unix is used, not because it is better, but because it is MUCH
cheaper than writing new systems. Also, even with Unix, new kernels have
to be written for different system architectures.
>for the most part, evreyone on this thread who's told you to let xp
>manage your virutal memory is giving you the best advice
Generally true but if you have enough disk space you will be better off to
create a large contiguous pagefile and not allow windows to change its
size. Just make sure it is as large as Windows will ever want to make it
and then let Windows use it how it will.
If you are writing an app that heavily utilizes uses a VERY large amount of
address space (virtual memory) then you MIGHT need to know how the XP
paging algorithm works. (The rules it uses to decide which pages to move
into and out of real memory.) Given any paging algorithm, I can write an
application for which that algorithm will be the worst possible algorithm
and the machine's computational speed will slow to much less than 1/1000th
its "normal" speed because each reference to memory will be for an address
that is in the pagefile and not in RAM. Thus an interrupt will occur, the
execution mode will change to ring 0, kernel will begin executing and will
have to, on average, move at least two pages between physical RAM and the
pagefile, do all of the associated book keeping, update the page table
(used by the hardware to map physical addresses to virtual addresses) and
switch back to the application.
>..anyone
>elsewhere or anywhere who's told you to remove or cripple you pagefile
>in any fasion is giving you advice that can't help, and can hurt.
Bottom line - Yep - you're right
>
>enjoy all that memory!
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