hahaha yes it is very silly, it turns out I was using 32bit box 

no wonder bitcoind crashes when reach 4gb and ignore the rest of the memory

i already moved it to 64bit and everything seems to work fine.

thanks for the help 

anyway, for anyone have similar issue but with limited RAM, using -dbcache=16 really do the trick. it works even for 100k+ addresses but every command become very slow.