Tracker-extract and Tracker-store processes consuming huge Amount of RAM

I am using Arch Linux, kernel 3.16. From last one week my two processes tracker-extract and tracker-store are taking too much RAM. It results in hangup of system once in every 2 hours. **tracker-extract taking 300 MB and tracker -store taking 2 GB RAM.** I want to know what are these tracker processes and what are their work. If i kill them does this effect in system performance ? What are the ways to kill them permanently so that I can get rid of these two processes? Please help me.