The jemalloc fix really does seem to reduce memory usage. Details here: https://x0r.be/@szbalint/99128946006465749
On the toot.cafe server, after letting Mastodon run for a day the system is using 2.4GB whereas before it was using 4.3GB.
Switching to jemalloc means we never have to go to swap on a 4GB machine, which is a huge win. Thanks @szbalint! #MastoAdmins