swap to a sparse file

[RW]

On Sat, 13 Oct 2018 08:11:18 +0100
Steve O'Hara-Smith wrote:

> On Fri, 12 Oct 2018 19:36:33 +0100
> RW via freebsd-questions <freebsd-questions at freebsd.org> wrote:
> 
> > On Thu, 11 Oct 2018 08:51:14 +0100
> > Steve O'Hara-Smith wrote:
> >   
> > > On Thu, 11 Oct 2018 08:47:05 +0700
> > > Victor Sudakov <vas at mpeks.tomsk.su> wrote:
> > >   
> > > > Is there any good reason I can't just "truncate -s2G /swap0" and
> > > > make the swap a sparse file?     
> > > 
> > > 	Just one - if the space isn't there when the system needs
> > > it there will be a panic.  
> > 
> > Is that really the only reason? I've not paid much attention, but
> > the warnings I've heard about this have made it sound a lot worse.  
> 
> 	There's not much worse the system can do than panic, other
> than deadlock which might happen if memory needs to be allocated in
> order to add blocks to the file. IIRC swap on a zvol can deadlock
> that way.


Yes, but filling up a drive is relatively avoidable - particularly if
there's space reserved for root.