At 11:32 AM 10/16/1998 David Gillett wrote:
>On 16 Oct 98 I wrote:
>> The best solution is:  Bring your RAM up to at least 64MB and let
>> Windows 98 handle your Swap File. This amount of RAM will
>> substantially reduce the Windows need for virtual memory and avoid
>> the attendant, time wasting Swap File management.
>
>  I beg to respectfully disagree.  While installing more RAM will
>reduce Windows' USE of the swap file, it won't affect Windows'
>MANAGEMENT of the swap file at all. . . .
>
>  Specifically, swap file space is allocated because a program uses
>RAM, not because there's not enough real RAM for it.  Adding RAM will
>reduce the number of reads and writes of the swap file, but it won't
>affect its growth and shrinkage.  A swap file managed by Windows WILL
>become fragmented, if there is any other activity on that volume.


David:

Let's reason this out.

Programs make calls for memory at an address mapped to a location
on the page table. That location on the page table then maps to either
physical RAM or to a swap file. Memory in Windows 95 programs is
broken down into 4K pages. These data pages are what is being
mapped between the virtual addresses and virtual memory. When a
program makes a call for a data page that is not in RAM, a page fault
occurs. The page fault tells the VMM to load that page from the swap file
into memory. When a system has a page fault, it reading information
from the hard disk rather than memory.

Thrashing occurs when you experience excessive page faults, and this
is manifested by high CPU utilization and large amounts of hard disk
activity. Page faulting is alleviated by adding more RAM or running
fewer applications.

Moreover, demand paging occurs when RAM becomes full and swaps
to disk. It is demand paging that mostly makes Windows adjust the
swap file (to grow and shrink) as needed.

Fragmentation is avoided when where are fewer writes to the swap file,
and with fewer additions and deletions (because we have installed lots
of RAM), there is less need for Windows to compress and resize, and
therefore there is less management.

With 128MB of RAM, one could conceivably DISABLE virtual memory
(if one did not use Internet Explorer, Photoshop, Office and Pagemaker
simultaneously). However, that is still fairly risky. So I prefer to leave
a swap file. I still have a permanent swap file on G: drive but it appears
hardly used because of all the RAM. So I let Windows handle it.

Finally, if you delete the swap file at every shut down (exit to DOS) or at
every boot up (F8 -- Command Prompt), it will be reconstructed at
Windows Startup, and will be nice and clean and unfragmented. Of
course, some people run their systems 24 hours and hardly ever reboot,
unless the memory holes get too large. These people should delete the
swap file at the Command Prompt occasionally, or run Norton which
can defrag a swap file (Windows 95 Defrag cannot).

Regards,

John Chin

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