Golang 中的基准测试如何使用？

func BenchmarkSqrt(b *testing.B) {
    for i := 0; i < b.N; i++ {
        math.Sqrt(float64(i))
    }
}

$ go test -bench=.

import (
    "sort"
    "container/heap"
    "math/rand"
)

func randomIntSlice(n int) []int {
    s := make([]int, n)
    for i := range s {
        s[i] = rand.Intn(n)
    }
    return s
}

func BenchmarkSort(b *testing.B) {
    b.RunParallel(func(pb *testing.PB) {
        for pb.Next() {
            s := randomIntSlice(10000)
            sort.Ints(s)
        }
    })
}

func BenchmarkHeapSort(b *testing.B) {
    b.RunParallel(func(pb *testing.PB) {
        for pb.Next() {
            s := randomIntSlice(10000)
            heap.Sort(s)
        }
    })
}

func BenchmarkQuickSort(b *testing.B) {
    b.RunParallel(func(pb *testing.PB) {
        for pb.Next() {
            s := randomIntSlice(10000)
            quickSort(s)
        }
    })
}

func quickSort(a []int) {
    if len(a) < 2 {
        return
    }
    left, right := 0, len(a)-1
    pivot := a[(left+right)/2]
    for left <= right {
        for a[left] < pivot {
            left++
        }
        for a[right] > pivot {
            right--
        }
        if left <= right {
            a[left], a[right] = a[right], a[left]
            left++
            right--
        }
    }
    quickSort(a[:left])
    quickSort(a[left:])
}

BenchmarkSort               636705 ns/op
BenchmarkHeapSort          645853 ns/op
BenchmarkQuickSort         837199 ns/op