package cacheverify

import (
    "sync/atomic"
    "testing"
)

type CountersUnpadded struct {
    requests uint64
    errors   uint64
    latency  uint64
    timeouts uint64
}

type CountersPadded struct {
    requests uint64
    _        [56]byte
    errors   uint64
    _        [56]byte
    latency  uint64
    _        [56]byte
    timeouts uint64
    _        [56]byte
}

func BenchmarkFalseSharing(b *testing.B) {
    b.Run("unpadded", func(b *testing.B) {
        c := &CountersUnpadded{}
        targets := []*uint64{&c.requests, &c.errors, &c.latency, &c.timeouts}
        var workerID uint32
        b.RunParallel(func(pb *testing.PB) {
            id := atomic.AddUint32(&workerID, 1) - 1
            slot := targets[id%uint32(len(targets))]
            for pb.Next() {
                atomic.AddUint64(slot, 1)
            }
        })
    })

    b.Run("padded", func(b *testing.B) {
        c := &CountersPadded{}
        targets := []*uint64{&c.requests, &c.errors, &c.latency, &c.timeouts}
        var workerID uint32
        b.RunParallel(func(pb *testing.PB) {
            id := atomic.AddUint32(&workerID, 1) - 1
            slot := targets[id%uint32(len(targets))]
            for pb.Next() {
                atomic.AddUint64(slot, 1)
            }
        })
    })
}