What is meant by the scalability of an SMP system?

Question

I'm currently learning for my final exam in operating systems and I'm stuck with a (probably very easy) question from earlier exams. The problem is, that we've never had that topic in the lecture and I'm not quite sure what my professor wants to hear ... but he asks this question in almost every exam!

"What is meant by the 'scalability' of an SMP system?" -> I know what an SMP system is but that's it.

On top of that he wants to know what hardware (and software!) factor limits the scalability of an SMP system (one keyword suffices as an answer). My idea:

Hardware -> number of processors, Software -> ?

I hope you can help me with that question.

Thank you in advance!

Kayaba

Answer 1

"What is meant by the 'scalability' of an SMP system?"

This refers to the practicable number of processors the system can support.

On top of that he wants to know what hardware (and software!) factor limits the scalability of an SMP system (one keyword suffices as an answer).

There are are lot of them. The biggest hardware issue is access to the system buses (memory and I/O). The biggest software factor is locking. The more processors you have, the more time they spend waiting on locks.