buffer: add tests and benchmarks.
In preparation for considering a switch away from the evil use of runtime's internal memclr function.geesefs-0-30-9
commit
2bb2916cf4
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@ -0,0 +1,118 @@
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package buffer
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import (
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"crypto/rand"
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"fmt"
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"io"
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"testing"
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"unsafe"
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)
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func randBytes(n int) (b []byte, err error) {
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b = make([]byte, n)
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_, err = io.ReadFull(rand.Reader, b)
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return
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}
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func TestMemclr(t *testing.T) {
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// All sizes up to 32 bytes.
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var sizes []int
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for i := 0; i <= 32; i++ {
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sizes = append(sizes, i)
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}
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// And a few hand-chosen sizes.
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sizes = append(sizes, []int{
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39, 41, 64, 127, 128, 129,
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1<<20 - 1,
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1 << 20,
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1<<20 + 1,
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}...)
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// For each size, fill a buffer with random bytes and then zero it.
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for _, size := range sizes {
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size := size
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t.Run(fmt.Sprintf("size=%d", size), func(t *testing.T) {
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// Generate
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b, err := randBytes(size)
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if err != nil {
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t.Fatalf("randBytes: %v", err)
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}
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// Clear
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var p unsafe.Pointer
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if len(b) != 0 {
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p = unsafe.Pointer(&b[0])
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}
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memclr(p, uintptr(len(b)))
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// Check
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for i, x := range b {
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if x != 0 {
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t.Fatalf("non-zero byte %d at offset %d", x, i)
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}
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}
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})
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}
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}
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func BenchmarkOutMessageReset(b *testing.B) {
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// A single buffer, which should fit in some level of CPU cache.
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b.Run("Single buffer", func(b *testing.B) {
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var om OutMessage
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for i := 0; i < b.N; i++ {
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om.Reset()
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}
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b.SetBytes(int64(om.offset))
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})
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// Many megabytes worth of buffers, which should defeat the CPU cache.
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b.Run("Many buffers", func(b *testing.B) {
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// The number of messages; intentionally a power of two.
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const numMessages = 128
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var oms [numMessages]OutMessage
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if s := unsafe.Sizeof(oms); s < 128<<20 {
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panic(fmt.Sprintf("Array is too small; total size: %d", s))
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}
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for i := 0; i < b.N; i++ {
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oms[i%numMessages].Reset()
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}
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b.SetBytes(int64(oms[0].offset))
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})
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}
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func BenchmarkOutMessageGrowShrink(b *testing.B) {
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// A single buffer, which should fit in some level of CPU cache.
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b.Run("Single buffer", func(b *testing.B) {
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var om OutMessage
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for i := 0; i < b.N; i++ {
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om.Grow(MaxReadSize)
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om.ShrinkTo(OutMessageInitialSize)
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}
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b.SetBytes(int64(MaxReadSize))
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})
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// Many megabytes worth of buffers, which should defeat the CPU cache.
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b.Run("Many buffers", func(b *testing.B) {
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// The number of messages; intentionally a power of two.
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const numMessages = 128
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var oms [numMessages]OutMessage
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if s := unsafe.Sizeof(oms); s < 128<<20 {
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panic(fmt.Sprintf("Array is too small; total size: %d", s))
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}
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for i := 0; i < b.N; i++ {
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oms[i%numMessages].Grow(MaxReadSize)
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oms[i%numMessages].ShrinkTo(OutMessageInitialSize)
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}
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b.SetBytes(int64(MaxReadSize))
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})
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}
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