Re: An idea for prefetching swapped memory...

["Jörn Engel" <joern@wohnheim.fh-wedel.de>]

On Mon, 7 April 2003 14:32:26 +0200, David Zaffiro wrote:
> 
> >The idea was about prefetching swapped out pages when some memory is free, 
> >the CPU is idle and the I/O load is low.
> >
> >So this should not 'cost' much but behave better on following situation:
> >(I think there are even more such situations, this one should just be an 
> >example)
> 
> Wouldn't it cost almost twice as much when the user requests a different 
> task, instead of the just swaped-in "last swaped-out task(s)"?!
> 
> Instead of loading this directly into a free portion of phys. memory, the 
> just-swapped-in-ex-swapped-out task(s) would need to be swapped-out *again* 
> in favour of the to-be-swaped-in task...
> 
> Or am I wrong here?

Partially. If done right, the swapout would simply free those pages.
The information is already on the disk and unchanged, after all.

Jörn

-- 
If you're willing to restrict the flexibility of your approach,
you can almost always do something better.
-- John Carmack