Re: how to let systemd hibernate start/stop the swap area?

[Michael Chapman <mike@xxxxxxxxxxxxxxxxx>]

On Thu, 30 Mar 2023, Lennart Poettering wrote:
> On Mi, 29.03.23 13:53, Christoph Anton Mitterer (calestyo@xxxxxxxxxxxx) wrote:
> 
> > > > That's a bad idea btw. I'd advise you not to do that: on modern
> > > > systems you want swap, since it makes anonymous memory reclaimable.
> > > > I
> > > > am not sure where you are getting this idea from that swap was
> > > > bad.
> >
> > Well I haven't said it's bad, but I guess it depends on the use case
> > any available RAM.
> 
> In almost all scenarios you want swap, regardless if little RAM or a
> lot. For specialist cases where you run everything from memory, and
> not even programs are backed by disk there might be exceptions. But
> that#s almost never the case.

One specific case where I deliberately chose _not_ to use swap: large 
hypervisors with local storage.

With swap on the host enabled, all that ended up happening was that local 
IO activity caused idle guest memory to be gradually swapped out. 
Eventually all of the swap space filled up, and the system was exactly 
where it would have been had it not had any swap space configured in the 
first place -- except that it was now _a lot_ slower to migrate those 
swapped-out guests to other hypervisors.

- Michael