After the upgrade to 1.9.0 there are lags in game which are very significant and they have high impact on the gameplay. What's interesting that lags were present before already but they were not so serious. Currently it goes to the moment that game is unplayable.

It is hard to say to what it is related, my world size is around 65MB, which does not seems to be a huge number, I did not go further in game than my L4 map.