FreeBSD Install config

AMAKAWA Shuhei sa264 at cam.ac.uk
Thu Dec 20 23:55:11 GMT 2001


At Thu, 20 Dec 2001 21:21:34 -0000,
Paul Richards wrote:
> > Then comes swap.  The 2 * (amount of ram) rule has been around for years
> > and is still pretty spot-on.  If you're like me and also have /tmp
> > mounted on swap you can make it slightly bigger.  Also can't hurt to
> > increase size anyway, diskspace is cheap and running out of swap isn't
> > something you want to run into.
> 
> I think the 2 * rule is overkill these days. If I remember correctly it
> started with Sun but my memories hazy.
> 
> Anyway, it's not relevant at all to FreeBSD or the current situation with
> memory being one of the cheapest components of the system.
> 
> You don't really need swap at all, it's only there to provide support for
> swapping out programs from "expensive" memory to "cheaper" disk so you can
> run more programs than you otherwise could. If you're box is swapping these
> days then just put more memory in it :-)

Doesn't too small a swap adversely affect the FreeBSD swap
performance?  I'm not exceedingly familiar with FreeBSD VM/swap
subsystem though..

Anyway, it's always a good idea to have a decent amount of swap
space.  If your program is continuously swapping in and out, then
you probably need more memory.  But if your program requires nearly
(but less than) all your memory and if you have big enough swap,
then idle processes will be swapped out and your busy program will
run happily without continuously swapping.  If you don't have enough
or any swap, you'll be in trouble.
Actually, even if your system has abundant memory, some idle pages
will be swapped out, thereby making some small number of pages
available to other processes.

--
Shuhei




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