Go: How Does the Garbage Collector Watch Your Application?

Illustration created for “A Journey With Go”, made from the original Go Gopher, created by Renee French.

ℹ️ This article is based on Go 1.13.

The Go garbage collector helps developers by automatically freeing the memory of their programs when it is not needed anymore. However, keeping track of the memory and cleaning it could impact the performances of our programs. The Go garbage collector has been designed to achieve those goals, and focus on:

• reducing as much as possible in the two phases when the program is stopped, also called “stop the world.”
• a cycle of the garbage collector that takes less than 10ms.
• the garbage collection cycle should not take more than 25% of the CPU.

These are ambitious objectives, and the garbage collector will be able to achieve them if it learns enough from our programs.

Heap Threshold Reached

The first metric the garbage collector will watch is the growth of the heap. By default, it will run when the heap doubles its size. Here is a simple program that allocates memory in a loop: