Почему MYSQL уходит в SWAP на 10ГБ при свободной RAM 20GB?

find /proc -maxdepth 2 -path "/proc/[0-9]*/status" -readable -exec awk -v FS=":" -v TOTSWP="$(cat /proc/swaps | sed 1d | awk 'BEGIN{sum=0} {sum=sum+$(NF-2)} END{print sum}')" '{process[$1]=$2;sub(/^[ \t]+/,"",process[$1]);} END {if(process["VmSwap"] && process["VmSwap"] != "0 kB") {used_swap=process["VmSwap"];sub(/[ a-zA-Z]+/,"",used_swap);percent=(used_swap/TOTSWP*100); printf "%10s %-30s %20s %6.2f%\n",process["Pid"],process["Name"],process["VmSwap"],percent} }' '{}' \;  | awk '{print $(NF-2),$0}' | sort -hr | head | cut -d " " -f2-
     29695 mysqld                                   4207592 kB  12.54%
     15645 Web Content                               183520 kB   0.55%
     22256 Web Content                               179788 kB   0.54%
     27618 VBoxSVC                                   153160 kB   0.46%
     23701 Web Content                               121528 kB   0.36%
      2061 gnome-shell                                99684 kB   0.30%
     22149 Web Content                                85684 kB   0.26%
     22067 firefox                                    76944 kB   0.23%
      7556 xfce4-taskmanag                            63716 kB   0.19%
     26915 nginx                                      29988 kB   0.09%