We recently enabled a really cool feature in ZJIT that makes it feel like a Real Compiler™: the inliner! We’ll write more about it soon. In this post, we’ll talk about one excellent concrete benefit we are already seeing and how it optimize…
If you’ve ever written a test for your code, you’re probably familiar with typical test framework methods: test/it to define test cases, and assert/expect to make assertions about the behavior of your code. However, I want to highlight a le…
2026-05-27 • Aaron Patterson We recently landed a new register allocator in ZJIT and I thought I’d write a post about it! Whenever a compiler generates machine code it needs to decide where to put values. Those values usually take the shape…
One engine, many tools A few years ago, the new Ruby parser Prism was released. One of its primary goals was to unify the community since we had multiple implementations of Ruby parsers, each with their own bugs, differences in implementati…
The story starts with Rust 1.85.0 giving me a surprise SIGTRAP in some test code. For reasons not important here, I had to bump opt-level from 0 to 1 for tests. That made a bunch of tests fail with SIGTRAP, whose default signal handler term…
Look! A trace of slow events in a benchmark! Hover over the image to see it get bigger. A sneak preview of what the trace looks like. Now read on to see what the slow events are and how we got this pretty picture. The rules The first rule o…
The Rails Infrastructure team has been working on making Bundler faster and our work has paid off. A cold bundle install is 3x faster on a Gemfile with 452 gems compared to Bundler 2.7. But “faster” only means something if everyone agrees o…
Intro Since the post at the end of last year, ZJIT has grown and changed in some exciting ways. This is the story of how a new, self-contained optimization pass causes ZJIT performance to surpass YJIT on an interesting microbenchmark. It ha…
At Shopify, we want our development environments to be fast. Installing dependencies is slow, especially in an application as large as Shopify. bun and uv have dramatically improved install times for TypeScript and Python dependencies. What…
2025-12-24 • Max Bernstein ZJIT is a new just-in-time (JIT) Ruby compiler built into the reference Ruby implementation, YARV, by the same compiler group that brought you YJIT. We (Aaron Patterson, Aiden Fox Ivey, Alan Wu, Jacob Denbeaux, Ke…
Ruby has always been a joy to write. But for a long time, reading Ruby documentation on docs.ruby-lang.org hasn’t really matched that experience. Last year, I brought a new look to the Darkfish theme by updating its visuals and improving mo…
2025-12-08 • Adrianna Chang This post explores Rails’s swappable migration backend, a little-known feature that lets applications customize how migrations run. At Shopify, we relied on monkey patches and a brittle SQL parser to make Rails m…