Memory Consistency Models

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Table of Contents

Memory Consistency Models

Administrivia

Review: Large Scale Shared Memory Multiprocessors

Review: Directory Example

Review: Distributed Directory

Directory Nomenclature

Limited Pointer Directory

Software Assistance

Coherence vs. Consistency

Why Coherence != Consistency

The Sequential Consistency Memory Model

Sufficient Conditions for Sequential Consistency

Relaxed Memory Models

Write Buffers w/ Read Bypass

Overlapping Reads or Writes

SC with Caches

Compilers and Sequential Consistency

Relaxed Memory Models

Weak Ordering

Weak Ordering Example

Release Consistency

Release Consistency Example

Review: Directory Example Sequential Consistency

Directory Example Release Consistency

The Programming Interface

Entry Consistency

Compiler Directed Coherence

Compiler Directed Coherence (Continued)

Author: Alvin R. Lebeck

Email: alvy@cs.duke.edu

Home Page: http://www.cs.duke.edu/~alvy