From: Juan-Carlos Lerman (jclerman_at_netzero.net)
Date: Thu Aug 05 1999 - 14:29:17 EDT
This whole *real* experimenting was not about what you correctly
discuss, but about what's missing there: the loss of performance
(greater execution time of programs) when the physical memory is
larger than the swappable memory for a given chipset and OS.
Michael Geary wrote:
>
> For anyone who is experimenting with putting a Windows swapfile on a RAMdisk, don't bother. There is no benefit at all in doing
> this, only a loss of performance and available memory.
>
> The swapfile is not a special thing that Windows needs to have and enjoys using. It is merely a slower substitute for memory,
> nothing more or less. If your Windows applications are using more memory than is physically available, Windows can use part of the
> disk as if it were memory. To do this, it swaps pages in and out between physical memory and the disk. By doing this swapping, the
> operating system lets programs run as if there were more memory available than is physically in the machine.
>
> Suppose you manage to create a 32Mb RAMdisk in which you'll place your swapfile. By doing that, you've reduced the available
> physical memory in your machine by 32Mb. Therefore, Windows will need to start swapping 32Mb sooner than it would have otherwise.
> You've gained absolutely nothing, you've lost some performance, and you won't even get back the whole 32Mb in swap space because of
> file system overhead.
>
> If you have enough memory in your machine that you'd like to eliminate swapping to disk, simply use the system control panel to turn
> off virtual memory completely. This will eliminate disk swapping, at the cost of limiting your memory use to what's physically
> available in the machine. This is the exact same benefit you'd hope to gain by putting the swapfile in a RAMdisk, except you
> eliminate all the software overhead. You just use memory as memory.
>
> If your machine currently does swap to disk with the set of applications you use, that means you're using more memory than the
> machine actually has. If you eliminate swapping, you'll also reduce the number and size of applications you can load.
>
> But if you'd loaded that smaller number of applications in the first place, you wouldn't be swapping anyway. Turning off swapping
> just prevents you from loading more apps than fit in memory.
>
> -Mike
>
> ThinkPads in the Open Directory: http://geary.com/thinkpad/
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