I doubt every last bit of their data needs to be hot (i.e. in memory) at any given time, but without specialized paging along the lines of what antirez has disc

I doubt every last bit of their data needs to be hot (i.e. in memory) at any given time, but without specialized paging along the lines of what antirez has discussed for redis, enough of their data probably needs to be hot that, from a paging perspective, all of the vm pages of their data need to be hot.