Using SSDs as swap

[Willem Jan Withagen]

one of the following commits just passed with this in the log, and it
triggered again a question I've been having for some time again already.

----
Log:
  Enable BIO_DELETE passthru in GELI, so TRIM/UNMAP can work as expected
when
  GELI is used on a SSD or inside virtual machine, so that guest can tell
  host that it is no longer using some of the storage.
-----

In ZFS I slice my SSD's into log and caches, but on a a server with
little memory (which can't be grown) I use a partion on each ssd as swap
as well. So swappinging does not have to seek, and has faster loading
time. To allocate a few GB on aan SSD to swap is not really all that
painfull, given current sizes, but the speed difference with regular
spindels is impressive.

But the questions are:
1) Does the swap driver understand that backing-store needs a TRIM?
1a) if not would it be useful, and what would it take to implement?
2) Does the SSD "suffer" unneeded from swapping on it?

Thanx,
--WjW