CPU cache collisions in the context of performance

This article discusses some potential performance issues caused by CPU cache collisions. In normal scenarios cache collisions don’t pose a problem, it usually is only in specific, high speed applications that they may incur noticeable performance penalties, and as such, things described here should be considered “the last mile effort”. As an example, I will…

Why I support the US Government making a cryptography standard weaker

Documents leaked by Edward Snowden last month reveal a $250M program by the NSA known as Operation BULLRUN, to insert vulnerabilities into encryption systems and weaken cryptography standards. It now seems nearly certain that the NIST-certified random number generator Dual_EC_DRBG, adopted as the default in RSA Security's BSAFE toolkit, contains a back door usable only by the NSA which allows them to predict the entire future output of the generator given only 32 bytes. So it's not the easiest time for NIST to suggest they should make a cryptography standard weaker than it was originally proposed. Nevertheless, I support them in this and I hope they go ahead with it.

Programming as a social activity

I realised tonight something that I’d forgotten. We’re usually so busy knocking out code to fulfil our timebox coomitments that it’s perhaps easy to forget something very important: to have fun. I went to the local Smalltalk user group tonight where Jason Ayers gave a talk on simplicity: do our tools help us make simple…

Changing the Primary Key Type in Ruby on Rails Models

Ruby on Rails (RoR) likes to emphasise the concept of convention over configuration. Therefore, it seeks to minimialise the amount of configuration by resorting to some defaults. These defaults are sometimes not desirable, and RoR does not always make it easy to deviate from these defaults.

My little Backpressure: Flow Control is magic

When we’re designing systems that are designed to be robust against failure, it’s important to know how behaviour at your Integration points (a term borrowed from Michael Nygard’s book Relase It!) impacts the rest of the system. For example, if your database or a remote API is running slowly, then in Synchronous systems, because you…

Testing the Reactor pattern

A good while ago I wrote a SIP stack. Like many network things, a SIP stack needs to keep track of multiple tasks – reading or writing from sockets, asking the user to respond to events, and so on. And so I naïvely added a bunch of threads. And then I spent a few weeks…

Precise scheduling with RabbitMQ

On a project recently, we needed to be able to process jobs asynchronously, but we also needed to be able to specify that they should be run at a certain point in the future. We also needed to be able to implement exponential backoff on failure. We initially tried to integrate Sidekiq, but unfortunately it…

Assuming there’s a user is sometimes a bad idea

Squeak has a very strong (historic) assumption that there’s a(n interactive) user interface. I stumbled across another occurrence of this assumption the other day. Let’s take a look at the problem, and how to fix it.

The great GC vs reference counting debate

I read a blog post post recently to the effect that GC is too expensive in mobile devices, Steve Jobs was right, reference counting is the way. It’s titled ‘why mobile web apps are slow’. I’m inclined to take issue with this: It’s a long since resolved dispute, and GC won. I don’t want Steve…

Delimited dynamic variables from call/cc

I’m prepared to own up to my biases. I like delimited continuations. I like zippers. I like getting halfway through my work, shelving my work for a time, and coming back to it later. We’ve seen the relationship between resumable exceptions and delimited dynamic variables before, but what about languages where you don’t have direct…