Dean Kent (dkent@realworldtech.com) on 5/14/07 wrote:
>
>It seems odd to me that virtually *every* address must
>be mapped, whether actually used or not.

Why would you ever have unused memory?

Why did you buy such memory in the first place?

Any sane OS (and yeah, XP/Vista may not fall under that
heading) will basically always use all your memory, and
you will never have anything unused.

Any unused memory is just wasted (pretty much by
definition).

So Linux will always use all your memory, even if it's
just for caching (of course, "just" is unfair. Caching
is just about the most important thing any OS can do, so
it's definitely not a "just" thing).

We keep a small percentage of memory free for emergency
purposes, and if you've run a big process and exit it
and throw it away we'll obviously temporarily have lots
of free memory that we can't do much about, but in
general you should never see any big amount of unused
memory except just after bootup.

Linus