Performance overhead of DOTS systems

SystemBase doesn't automatically synchronize before entering OnUpdate. Synchronization happens when:
a) structural changes occur (AddComponent / Instantiate etc)
b) SystemBase.GetComponent / SystemBase.SetComponent on the main thread
c) Entities.ForEach.Run


When using Entities.ForEach.Schedule happens there is no sync point. This means that it is unnecessary to declare [AlwaysSynchronizeSystem] because it is implied in the used operations. This makes it much easier to switch multithreaded and main thread code. This is very important during debugging & development, sometimes you don't start out writing multithreaded code, but just want to experiment and then slowly build up to multithreaded code.