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Locking Review

This lecture covers the implementation of small multiprocessors.

In this course, you will learn to design the computer architecture of complex modern microprocessors. All the features of this course are available for free. It does not offer a certificate upon completion.

Impartido por:

David Wentzlaff
Associate Professor

Transcripción

So, welcome back, today we are going to be talking about how to go

about building cache coherent systems, so, we've

just come off talking about consistency, and

memory consistency and now we're going to start

talking about, memory coherent systems and talk

about, sort of, the beginning protocols when

you go about building memory coherent systems.

Before that.

Let's go back and review what we worked what

we're working on at the end of last lecture.

So at the end of last lecture, we were talking about

mutual exclusion and one of the we talked about having test and

set and specialized operations that can do, that can give you

mutual exclusion but you could also just use basic loads and stores.

And, we talked about using Decker's algorithm

and, one of the key insights into the

Decker's algorithm is that you have this shared

turn variable here which between the 2 processes,

which are trying to communicate, are trying to lock the same, variable.

Then we went on an expanded this to. Multiple process mutual exclusion.

And this is the sort of the moral equivalent of

a, going to the deli and try and take a ticket.

So you go to the deli, you take a little ticket, and

then someone goes and calls your ticket number, and then you are served.

This is how you can implement multiple people trying to access one resource.

but unlike in a deli where you have let's say

a, a number on the, on the wall which ticks up.

Or you have a, a person behind the deli who calls your number.

Or in a bakery where they call your number.

Instead here we need to do that in some sort of distributing manner.

So in the end process mutual exclusion.

The person who actually finishes being served wakes up the next person.

And as I said, this is a little bit more

complex but you can still do the same idea here.

excuse me, totally with loads and stores.

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