It's odd you have such bad performance on a 64bits OS, i have an older OS on 32 bits only and have no problem with Minetest that is apparently supposed to use the CPU much more than the GPU
Some tips :
The minimap can be intensive, don't display it, but even when not displayed apparently still gather data, so you may then want to add
enable_minimap = false
to your minetest.conf file
The view distance auto tuner eat lots of ressources too, you can't disable it but it's possible to limit it by setting the same value to those
viewing_range_nodes_min =
viewing_range_nodes_max =
in your minetest.conf file to have it fixed , probably set the value to your desired viewrange
Set
fps_max = 30
wanted_fps = 30
to your minetest.conf, it should be enough
Additionally, use the latest minetest version, it had got some better performance.
And even better, use the latest build (I use Krock's one myself), there was
an additional performance increase that was done after the latest minetest stable 0.4.15 release.
You can reach the build board :
viewforum.php?f=42And while on your 64bit OS you may want to use the 64bits Minetest, there are report the 64bits version generate a lot of those "out of memory" error, so you may still want to use the 32bits version