[reis3k]

It means that 1.1 GB of your disk is cached to memory and will be served faster

this answers first make a little confused, because I thought that 1.1 Gb data served in my disk and having a potential to use later on is cached.

linux keeps buffers and caches of previously used apps just in case they are needed again and so greatly increases loading and access speed and reduces disk access.

Then I can conclude that for the first time boot of os, the cached size will be zero.

Thanks both of u,but I think you make some math to calculate how much size in mb a apps consumes in the memory after you execute ps -aux (percentages of usage X memory size) instead of directly see the result on the console