How to Trace Garbage Collection in Go

Introduction
Prerequisites
Setup
Tracing Garbage Collection
Example
Conclusion

Introduction

In Go, garbage collection is an essential part of memory management. Being able to trace the garbage collection process can help us understand how memory is allocated and deallocated in our programs. In this tutorial, we will learn how to trace garbage collection in Go and analyze the collected information. By the end, you will be able to monitor and optimize memory usage in your Go applications effectively.

Prerequisites

To follow this tutorial, you should have a basic understanding of the Go programming language and be familiar with concepts related to memory management and performance optimization.

Setup

Before we proceed, let’s make sure we have the necessary setup:

Go installation: Ensure that Go is installed on your system, and the go command is accessible from the command line.
Code editor: Choose a code editor of your preference. Visual Studio Code, GoLand, or Sublime Text are popular choices among Go developers.

Tracing Garbage Collection

Go provides a built-in tracing tool called trace that allows us to capture and analyze garbage collection events. To enable garbage collection tracing in our Go program, we need to import the runtime/trace package and use its API.

The following steps will guide you through the process of tracing garbage collection in Go:

Import the runtime/trace package into your Go code:
```
 import (
     "runtime/trace"
 )
```
At the beginning of the code section where you want to trace garbage collection, start the tracing by calling trace.Start and passing a file name to save the trace events:
```
 f, err := os.Create("trace.out")
 if err != nil {
     log.Fatal(err)
 }
 defer f.Close()
    
 err = trace.Start(f)
 if err != nil {
     log.Fatal(err)
 }
 defer trace.Stop()
```
In the above code, we create a file named “trace.out” to save the trace events. It’s important to ensure the file is closed properly, so we use defer to close it after the program finishes execution.
Run your Go program with tracing enabled. For example:
```
 go run main.go
```
Once the program execution is complete, open the generated trace.out file using the go tool trace command:
```
 go tool trace trace.out
```
This command will start a local web server and open a browser window displaying the trace visualization.
Analyze the trace visualization. The trace visualization provides detailed information about the garbage collection events, memory usage, goroutine activity, and other performance-related metrics. Use the navigation tools provided to explore different sections and zoom in on specific time ranges.

Example

Let’s go through a simple example to demonstrate how to trace garbage collection in Go. Consider the following code:

package main

import (
    "log"
    "os"
    "runtime/trace"
)

func main() {
    f, err := os.Create("trace.out")
    if err != nil {
        log.Fatal(err)
    }
    defer f.Close()

    err = trace.Start(f)
    if err != nil {
        log.Fatal(err)
    }
    defer trace.Stop()

    // Simulating some operations
    for i := 0; i < 1000000; i++ {
        _ = make([]byte, 1024)
    }
}

In the above code, we import the necessary packages and set up tracing as explained earlier. Inside the main function, we simulate some memory-intensive operations by repeatedly allocating one kilobyte slices. This will trigger garbage collection events.

Save the code to a file named main.go, and then run it using the command:

go run main.go

After the program completes, execute the following command to view the trace visualization:

go tool trace trace.out

Explore the trace visualization to observe the garbage collection events and memory usage patterns.

Conclusion

Tracing garbage collection in Go can greatly assist in understanding how memory is managed in your applications. By using the runtime/trace package, we can capture and analyze garbage collection events to identify memory usage patterns and potential optimization opportunities. In this tutorial, you have learned how to enable garbage collection tracing in Go and analyze the collected information using the go tool trace command.

Published: 21 November 2021