I was experimenting with Windows, Ubuntu Server and Ubuntu Desktop booted into the command line only.
So my expectations were that Linux will do better than Windows and because of my strong conviction for Linux I was hoping to get maybe a bit higher and constant H/s.
Also, I did same test on a bit worse machine Acer Aspire One 725 (64bit 4GB RAM and 1GHz CPU C-60).
In this case, Windows worked better.
I was able to get 20 - 40 H/s on Windows and Ubuntu Server.
10 H/s in average, according to minexmr.com stats.
Ubuntu Desktop booted to CLI wasn't able to get even 1H/s (got 0.4 H/s).
Who said that Ubuntu Server is actual Ubuntu Desktop without DE?
Or is it not?
Large pages are supported, but 4GB not 3GB is not enough to use it.
It would be interesting to know the absolute minimum to get working mining.
Essentially to answer my question, I think that the reason for the issue above is just to weak machine!