Somehow , a lot of my users complain it gets slower as the wiki is up. And, once i reboot the linux, it got faster. I checked the serving page time, and it reduces from 1.48s to 600ms. (By using the chrome developer tool, under network).
Maybe i have to setup a cron job to reboot the system every evening? Don't think this is a long term viable solution.
This is the bitnami mediawiki VM that i am using, which i run privately. therefore, that webpage doesn't work.