With each of the past 3 Ruby releases, YJIT has delivered higher and higher performance. However, we are seeing diminishing returns, because as JIT-compiled code becomes faster, it makes up less and less of the total execution time, which is now becoming dominated by C function calls. As such, it may appear like there is a fundamental limit to Ruby’s performance.

In the first half of the 20th century, some early airplane designers thought that the speed of sound was a fundamental limit on the speed reachable by airplanes, thus coining the term “sound barrier”. This limit was eventually overcome, as it became understood that airflow behaves differently at supersonic speeds.

In order to break the Ruby performance barrier, it will be necessary to reduce the dependency on C extensions, and start writing more gems in pure Ruby code. In this talk, I want to look at this problem more in depth, and explore how YJIT can help enable writing pure-Ruby software that delivers high performance levels.