1. the gentoo handbook says :"Some distributions make /dev/shm a symbolic link to /run/shm which, after the chroot, becomes invalid. " This is the case here - buit the handbook doesn't told how to circumvent it :-( so something like rm /mnt/gentoo/dev/shm mkdir /mnt/gentoo/dev/shm mount --rbind /dev/shm /mnt/gentoo/dev/shm should be added 2. the make of the kernel van be speed up via "make -jX" or so
Thanks, I've updated both parts accordingly.