[GTALUG] Fedora 33 uses RAM for swap?

[Giles Orr]

On Wed, 25 Nov 2020 at 08:18, Giles Orr <gilesorr at gmail.com> wrote:
> A few days after upgrading the last of my machines from Fedora 32 to
> 33, I noticed my main machine has acquired a new disk:
>
> NAME               SIZE FSTYPE      LABEL    MOUNTPOINT
> zram0                4G                      [SWAP]
>
> I didn't set that up, and I don't think it was there on F32.  So the
> OS has, without asking, co-opted 1/4 of my 16G of RAM to use as swap
> space.  This system has an SSD, so when I initially set it up (Fedora
> 27), I made a conscious decision to go without swap space.  I rarely
> push the limits of 16G.
>
> But now I'm in the situation that I have only 12G of RAM, so the
> system will become memory-starved earlier ... and what will it do?  It
> will go to swap.  Which is RAM anyway.  How does this help?  To me
> this seems like adding complexity without adding utility.
>
> Can someone please explain A) if I'm correct about this behaviour in
> the first place, and B) why it's useful?  Thanks.

Hugh, this machine was an upgrade from Fedora 32.  I guess the
decision was made to go with the new default rather than ask questions
during the upgrade.  Thanks Hugh, Mauro, Dave for the info - and my
apologies, I did zero research before turning to the list.  Not my
usual behaviour, I promise - I guess I was peeved because it was so
unexpected.

I assumed right out the gate that the statement "4G" meant it was
using 4G of RAM.  As has been pointed out, it's not allocated until
it's used, and it's compressed - so even when full it'll usually only
use 2G of RAM.  After having read about it some, it sounds like it's
mostly a win.

-- 
Giles
https://www.gilesorr.com/
gilesorr at gmail.com