Swap Space

[Adam Vande More]

On Wed, Jan 5, 2011 at 5:33 PM, Gary Gatten <Ggatten at waddell.com> wrote:

>
> > Correct me if I'm wrong, but if necessary one could add (and
> > activate) a secondary / additional swap file if necessary without
> > rebooting.  So maybe start with a few gig and add an additional swap
> > file if necessary?
>
> Swapping to a file is really slow and should only be done if absolutely
> necessary since every read/write has to go through the filesystem code
> which it doesn't do if done via a swap slice.
>
> Good point.  It's been several years and back on v5 or 6 when I did
> something like this.  If there's unpartitioned space on the drive, can one
> add a secondary swap partition real-time?  I forget what I did here - I'm
> sure I followed what's in the handbook re swap space.  Probably did a swap
> file...
>

 Yes you can do that with swapon(1)

It's been said though that FreeBSD memory paging algorithms take into
account the system's entire available VM for deciding on when to act in low
memory conditions and these parameters are tuned expect some of that to be
swap space.  That is why one reason there *should* be a least some swap
space even on a system w/ plenty of RAM.



-- 
Adam Vande More