Go 1.25 has introduced an innovative feature known as Green Tea, an experimental garbage collector designed to optimize GC performance with a focus on modern hardware capabilities. By reducing garbage collection (GC) overhead by 10-40% across various workloads, Green Tea stands out as a significant advancement over traditional mark-sweep algorithms.
The key innovation of Green Tea lies in its approach to memory scanning. Instead of traversing individual objects like traditional GC methods, Green Tea operates on entire memory pages. This page-based processing enhances CPU cache utilization and harnesses vector instruction acceleration, notably utilizing AVX-512 instructions. Such improvements align well with modern hardware challenges, including non-uniform memory access (NUMA), reduced memory bandwidth, and the rise of increased core counts.
Green Tea’s approach of processing pages sequentially minimizes the microarchitectural inefficiencies commonly associated with unpredictable graph traversal. This method proves especially effective with regular heap structures, yet it also includes optimizations to handle edge cases efficiently.
Already deployed within Google’s production environments, Green Tea demonstrates its reliability and production-readiness. Users eager to explore this feature can activate it via the <code>GOEXPERIMENT=greenteagc</code> flag. Looking ahead, Green Tea is expected to become the default garbage collector starting with Go 1.26, promising further enhancements in Go’s performance and efficiency.

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Go 1.25 introduces Green Tea, an experimental garbage collector that reduces GC overhead by 10-40% through page-based memory scanning instead of object-by-object traversal. It leverages modern hardware features like AVX-512 vector instructions and optimizes for CPU cache utilization, NUMA architectures, and high core counts. Already running in Google's production systems, Green Tea can be enabled with the GOEXPERIMENT=greenteagc flag and is planned to become the default GC in Go 1.26.

Introducing Green Tea: Go's Experimental Garbage Collector