When a process allocates 4GiB or more of ram on a 64 bit system then the memory used is incorrectly reported by conky.
The patch is attached. I did not really test it with git version (it does not accept my old config from 1.3.1 which is still used in archlinux). I ported the patch from 1.3.1 which I still use. Should work. It is rather strait forward.