Arm Barriers 101: What Are Barriers And Why Do We Need Them?

Part 1 of our comprehensive deep dive on barriers in the Arm Architecture!

What you'll learn

Discover why Arm defines a weakly-ordered memory model

Explore the rules dictating whether two memory access may be reordered

Learn how to use barriers in software to manually enforce ordering

Learn how to descope barriers to mitigate any potential impacts on system performance

Requirements

Beginner friendly!

Assumes no prior Arm Architecture experience.

Some basic C/C++ programming experience is recommended, but not required.

Description

Welcome to Part 1 of our Barriers 101 training course, a comprehensive deep dive on barriers in the Arm® Architecture.This course is suitable for software engineers working on Arm-based platforms at any level of the software stack, from down at the firmware layer all the way up through the kernel, hypervisor, device drivers, and user-space applications.In these lessons, you'll learn:Why Arm defines a so-called "weakly-ordered" memory model.The rules dictating whether two memory accesses may be reordered.How to use barriers in software to manually enforce ordering.How to descope barriers to minimise any potential impacts on system performance.From beginner to expert: Our courses are suitable for all levels of experience, whether you're already a seasoned veteran of the Arm Architecture or you're seeing Arm Barriers for the very first time.How it really works: Our courses go both broader and deeper on the topic of barriers than anyone else; we show you how things really work, and more importantly, why.Learning is doing: Reinforce your learning with a workshop session tackling various barrier scenarios from first principles, followed by 30 multiple-choice quiz questions with a video walkthrough of each question and answer.Recognised trainer: Our courses are written and produced by Ash Wilding, formerly one of Arm's lead technical trainers and a kernel engineer at both Amazon AWS and Apple.

Overview

Section 1: What are barriers, and why do we need them?

Lecture 1 Why weakly-ordered?

Lecture 2 System-level reordering

Lecture 3 Dependencies and successors

Lecture 4 Idempotence and speculation

Lecture 5 Data Memory Barriers

Lecture 6 Shareability domains

Lecture 7 Conventions and expectations

Lecture 8 Atomics and synchronization

Lecture 9 Workshop

Lecture 10 Quiz

Engineers at all experience levels working on Arm-based platforms.,Firmware Engineers.,Kernel Engineers.,Hypervisor Engineers.,Device Driver Engineers.,Application Developers.