To check who is using swap space on linux You can use command:
find /proc -maxdepth 2 -path "/proc/[0-9]*/status" \
-readable -exec awk -v FS=":" '{process[$1]=$2;sub(/^[ \t]+/,"",process[$1]);} \
END {if(process["VmSwap"] && process["VmSwap"] != "0 kB") \
printf "%10s %-30s %20s\n",process["Pid"],process["Name"],process["VmSwap"]}' '{}' \;