It takes a long time to save big worlds

I have a very big world (~1.1GB) and it always Takes nearly 5 minutes to save it. The renderdistance at this world is only at 8 chunks.
How to reproduce:
1. You have to make a world in creative to make it faster to reproduce
2. Load a lot oft chunks. So mich that the world Has size of 700MB
3.Than save it.

Observer results
The world save takes alot oft time. Almost as if it would save the whole world at once

Expected results
It should only take some seconds, because there are only the loadet chunks to save.

This bug is a very along time in the game ( 1.10 or less)

Update:
This happens only if you move alot of in your world(killing mobs or go mining) , so that you load loaded chunks . It doesn´t take long time if you are only at the same chunk during playing and don´t move (maybe during fishing or stand near an AFK-Farm)