"Context switch" used without being defined

[nickdrozd]

Section 3.7.6 says

But one drawback is that it forces threads to go through sequentially, which may cause more context switching than necessary.

I think it would be a good idea to say a word or two about this, maybe in the introduction.

Similarly, section 3.3.2 has

This solution also works, although it is probably less efficient, since it might have to switch between A and B one time more than necessary.

Is that also about context switching? A little more explanation would be good here too.