IT’S ABOUT TIME, TOO

Last month was the 30th anniversary of the original announcement of Linux. This month it’s time for another anniversary in the form of 17 years since the first “PREEMPT_ RT” (Real Time) kernel patch was posted upstream by Ingo Molnar. It might not be all that much longer until – finally – all of the pieces needed to run a Linux kernel with bounded deterministic performance for latency sensitive workloads are finally in upstream kernels.

I first encountered the “RT” kernel patch not long after Ingo first posted it. In fact, Ingo wasn’t actually the first to work on Real Time Linux support. A number of others came before, but Ingo’s patches were most influenced by work from Sven-Thorsten Dietrich. Sven had taken a disciplined academic approach to determining the pieces of Linux most impactful upon overall latency, and had created a “real-time” patch series for Montavista Linux that implemented many of the ideas Ingo would refine into what would become PREEMPT_RT later on.

In those early days, I enjoyed gaining experience with Real Time through work on embedded Linux systems (years later, I co-authored a book with one of the RT maintainers on embedded Linux), and then a Real Time product that targeted such users as stock trading platforms. Traders and embedded folks building robots have more in common than you would think, since both care about extremely low-latency response. It was fun being a fly on the wall in those early days, but I didn’t at the time think that it would take almost two decades to upstream.