Titre : Shared memory, an elusive abstraction

Auteur : Francesco Zappa Nardelli (projet Moscova - Inria)

Abstract: 

Multiprocessors provide an abstraction of shared memory, accessible by concurrently executing threads, 
which supports a wide range of software. However, exactly what this key abstraction is 
---what the hardware designers implement, and what programmers can depend on--- 
is surprisingly elusive. The sophisticated optimizations implemented by modern multiprocessors have 
various programmer-visible effects: for some these effects are captured in a well-defined relaxed 
memory model, making it possible (if challenging) to reason with confidence about the behavior 
of concurrent programs; for others, however, it has been very unclear what a reasonable model is, 
despite extensive research over the last three decades. In this talk, I will present 
relaxed memory models and will reflect on the experience of trying to establish usable models for x86, 
Power and ARM multiprocessors.