Lets talk about mechanical sympathy. Martin Thompson has been making this term very popular in software development, so it’s best to read his description of why he used the term.

My recent slow-down in posting is because I’ve been trying to write a post explaining memory barriers and their applicability in the Disruptor. The problem is, no matter how much I read and no matter how many times I ask the ever-patient Martin and Mike questions trying to clarify some point, I just don’t intuitively grasp the subject. I guess I don’t have the deep background knowledge required to fully understand.

So, rather than make an idiot of myself trying to explain something I don’t really get, I’m going to try and cover, at an abstract / massive-simplification level, what I do understand in the area. Martin has written a post going into memory barriers in some detail, so hopefully I can get away with skimming the subject.

We mention the phrase Mechanical Sympathy quite a lot, in fact it’s even Martin’s blog title. It’s about understanding how the underlying hardware operates and programming in a way that works with that, not against it.

We get a number of comments and questions about the mysterious cache line padding in the RingBuffer, and I referred to it in the last post. Since this lends itself to pretty pictures, it’s the next thing I thought I would tackle.