Write a benchmark function starting with Benchmark and taking *testing.B as a parameter. 2. Place the benchmark in a test.go file and ensure the main logic runs inside a loop that iterates b.N times. 3. Run the benchmark using go test -bench=. to measure execution time. 4. Use go test -bench=. -benchmem to also track memory allocations. 5. Perform setup operations outside the benchmark loop and use b.ResetTimer() if needed to exclude setup time. 6. Avoid compiler optimizations by using the result via or b.ReportMetric. 7. Use b.Run to create sub-benchmarks for different inputs, enabling labeled and comparative results. 8. Ensure benchmarks are stable by avoiding external dependencies and running them multiple times with -count to verify consistency. The Go testing framework automatically adjusts b.N for statistically significant results and reports performance metrics per operation, completing the entire benchmarking process efficiently.
Writing a benchmark test in Go is straightforward and built into the testing package. You use it to measure the performance of your code—typically how fast a function runs and how much memory it allocates.
Use the Benchmark Prefix and *testing.B Parameter
To create a benchmark, define a function whose name starts with Benchmark, takes a pointer to testing.B, and lives in a _test.go file.
// math_test.go
package main
import "testing"
func BenchmarkAdd(b *testing.B) {
for i := 0; i < b.N; i {
Add(1, 2)
}
}Here, Add is the function you're testing. The loop runs b.N times, where b.N is automatically adjusted by the go test tool to get statistically significant results.
Run the Benchmark with go test -bench
Run your benchmark using:
go test -bench=.
This runs all benchmarks in the current package. Output looks like:
BenchmarkAdd-8 1000000000 0.300 ns/op
This means the Add function took about 0.3 nanoseconds per operation on average, using 8 CPU threads.
You can also combine it with -benchmem to see memory allocation:
go test -bench=. -benchmem
Output might include:
BenchmarkAdd-8 1000000000 0.300 ns/op 0 B/op 0 allocs/op
This shows no memory was allocated per operation.
Write Meaningful Benchmarks
Make sure your benchmark reflects real usage. For example, if you're benchmarking a function that processes a slice, avoid including setup time in the measured loop.
func BenchmarkFibonacci(b *testing.B) {
for i := 0; i < b.N; i {
Fibonacci(10)
}
}If setup is needed (e.g., large input), do it outside the loop:
func BenchmarkProcessData(b *testing.B) {
data := make([]int, 1000)
for i := range data {
data[i] = i
}
b.ResetTimer() // Optional: ignore setup time
for i := 0; i < b.N; i {
Process(data)
}
}Tips for Effective Benchmarking
- Avoid compiler optimizations that skip unused results. If your function returns a value you don’t use, assign it to
_or useb.ReportMetricif relevant. - Use sub-benchmarks with
b.Runto test multiple inputs:
func BenchmarkAddDifferentInputs(b *testing.B) {
inputs := []int{1, 2, 5, 10}
for _, v := range inputs {
b.Run(fmt.Sprintf("Input_%d", v), func(b *testing.B) {
for i := 0; i < b.N; i {
Add(v, v 1)
}
})
}
}This gives you labeled results:
BenchmarkAddDifferentInputs/Input_1 BenchmarkAddDifferentInputs/Input_2 ...
- Keep benchmarks stable: Avoid network, disk I/O, or external dependencies.
- Run multiple times to check for consistency. Use
-count:
go test -bench=. -count=3
Basically, write a function with the right signature, loop b.N times, and run go test -bench. The tool does the rest.
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