Linux clear cache

Linux clear cache

How to clear the cache in Linux, my top command shows like this,
Cpu(s): 0.0%us, 0.2%sy, 0.0%ni, 99.8%id, 0.0%wa, 0.0%hi, 0.0%si,
0.0%st
Mem: 10036256k total, 7364896k used, 2671360k free, 2616k buffers
Swap: 8191992k total, 82752k used, 8109240k free, 104244k cached
and my free -m looks like this,
total used free shared buffers cached
Mem: 9801 7192 2608 0 2 101
-/+ buffers/cache: 7088 2712
Swap: 7999 80 7919
I tried with drop_cache command but still my memory utilization is high.
How to clear this?
Thanks.