Advanced Techniques in Go Programming/

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Benchmarking Code II

Benchmarking Code II

Let’s learn how to benchmark code in Go.

We'll cover the following...

Benchmarking buffered writing and reading

In this lesson, we are going to test whether the size of the buffer plays a key role in the performance of write operations. This also gives us the opportunity to discuss table tests as well as the use of the testdata folder, which is reserved by Go for storing files that are going to be used during benchmarking—both table tests and the testdata folder can also be used in testing functions.

The code of table_test.go is the following:

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package table
import (
	"fmt"
	"os"
	"path"
	"strconv"
	"testing"
)
var ERR error
var countChars int
func benchmarkCreate(b *testing.B, buffer, filesize int) {
	filename := path.Join(os.TempDir(), strconv.Itoa(buffer))
	filename = filename + "-" + strconv.Itoa(filesize)
	var err error
	for i := 0; i < b.N; i++ {
		err = Create(filename, buffer, filesize)
	}
	ERR = err
	
	err = os.Remove(filename)
	if err != nil {
		fmt.Println(err)
	}
	ERR = err
}

And now, some important information regarding benchmarking: each benchmark function is executed for at least one second by default—this duration also includes the execution time of the functions that are called by a benchmark function. If the benchmark function returns in a time that is less than one second, the value of b.N is increased, and the function runs again as many times in total as the value of b.N. The first time the value of b.N is 1, then it becomes 2, then 5, then 10, then 20, then 50, and so on. This happens because the faster the function, the more times Go needs to run it to get accurate results.

The reason for storing the return value of Create() in a variable named err and using another global variable named ERR afterward is tricky. We want to prevent the compiler from doing any optimizations that might exclude the function that we want to measure from being executed because its results are never used.

Neither the signature nor the name of benchmarkCreate() makes it a benchmark function. This is a helper function that allows us to call Create(), which creates a new file on disk and its implementation can be found in table.go, with the proper parameters. Its implementation ...