[CST-1b] OS Funcs - 97.4.7

[MARTIN Clive Neale Harper]

On Wed, 31 May 2000, Nathan Dimmock wrote:

> OS Funcs - 97.4.7.  List 5 techniques that can be used in an OS to
> improve the performance of demand paged virtual memory.
> 
> The only one I could think of is pre-paging. :(  Can anyone give me a
> clue about the rest, please?

Page stuff out when it's not being used (in time where the processor would
be idling). That means when you demand page, there's likely to be a free
area to page it into, which saves time.

Go down to your local hardware store, and buy a faster hard disk. Or,
more sensibly, Put the virtual memory section on those parts of the disks
which can be accessed quickly. (that's the outside, if it's
constant-angular momentum). Or where the seek time is minimised. (hmm,
that'd be the middle).

Scheduling other work to happen while the page is being paged in, of
course. Not paging stuff out at random, but with some LRU-style strategy.
You may or may not allow paging of the OS, which may or may not improve
performance.

Oh, and detect thrashing, and move to take out processes when this
happens. (or you could pull a win95, and tell the user that the system is
unstable... ;).

Any others?