не монтируется swap при загрузке gentoo

To identify which partition is allocated as swap (and what % of that partition is actually being utilized), use "swapon -s".

Regarding "swapon -a", note that the man page states that "devices that are already running as swap are silently skipped", meaning that they shouldn't be displayed in the output. I'm not sure why you got the "device or resource busy message" when you did "swapon -a" though.

cat /proc/meminfo

нутк, решения проблемы-то нет.

посмотри, кто его держит (fuser и т.п.)