A walk through Go's new Green Tea collector as it moves across the heap

Sources: The Consensus, Go blog on Green Tea, HN 49045474
Summary: A post dated 2026-07-19 observes the old and the new Go garbage collector at work and measures where the new one differs. Green Tea shipped in Go 1.25 and is the default in Go 1.26. The post uses perf to locate where the cache-friendliness shows up, visualizes size-class span allocation against C#, and names the case that does not improve: a non-moving collector cannot reclaim sparse pages. The author is Phil Eaton, bylined on the publisher's own domain. The post reached the Hacker News front page on 2026-07-25 at 237 points with 30 comments. It is carried nine days after publication as measured analysis of a collector that every Go 1.26 service runs by default, not as news of a release.
Why it matters: Every Go service on 1.26 runs Green Tea whether or not the team read the release note, so a measured account of what changes and what does not is what a team checks before it attributes a latency shift to the collector.