I kept getting alert about low memory. After some digging, it turns out apache eats most of my memory.

I experimented with ab, and monitored memory change with top, sort by memory (by pressed M, also wrote configuration with W to

~/.toprc

). Disabled couple un-used modules seem to lower the level of memory use by apache2, I will need to keep an eye on monitoring them.

To list enabled modules,

apache2 -t -D DUMP_MODULES|more

To disable a module

a2dismod module_name

To enable a module

a2enmod module_name