MySQL High memory issue

RAM usage is getting filled up when I execute a simple query against a federated table.

SELECT * FROM `daily_limit` LIMIT 0, 30

*Before : *
free -g
total used free shared buffers cached
Mem: 125 67 57 0 0 10

During Query execution :
free -g
total used free shared buffers cached
Mem: 125 124 1 0 0 30

Processlist :

Note : I've killed the query since memory usage gone high