whatcanGOwrong

go/pkg/mod/github.com/cilium/ebpf@v0.11.0/asm/metadata_test.go

@@ -0,0 +1,109 @@
+package asm
+
+import (
+	"testing"
+	"unsafe"
+
+	qt "github.com/frankban/quicktest"
+)
+
+func TestMetadata(t *testing.T) {
+	var m Metadata
+
+	// Metadata should be the size of a pointer.
+	qt.Assert(t, unsafe.Sizeof(m), qt.Equals, unsafe.Sizeof(uintptr(0)))
+
+	// A lookup in a nil meta should return nil.
+	qt.Assert(t, m.Get(bool(false)), qt.IsNil)
+
+	// We can look up anything we inserted.
+	m.Set(bool(false), int(0))
+	m.Set(int(1), int(1))
+	qt.Assert(t, m.Get(bool(false)), qt.Equals, int(0))
+	qt.Assert(t, m.Get(int(1)), qt.Equals, int(1))
+
+	// We have copy on write semantics
+	old := m
+	m.Set(bool(false), int(1))
+	qt.Assert(t, m.Get(bool(false)), qt.Equals, int(1))
+	qt.Assert(t, m.Get(int(1)), qt.Equals, int(1))
+	qt.Assert(t, old.Get(bool(false)), qt.Equals, int(0))
+	qt.Assert(t, old.Get(int(1)), qt.Equals, int(1))
+
+	// Newtypes are handled distinctly.
+	type b bool
+	m.Set(b(false), int(42))
+	qt.Assert(t, m.Get(bool(false)), qt.Equals, int(1))
+	qt.Assert(t, m.Get(int(1)), qt.Equals, int(1))
+	qt.Assert(t, m.Get(b(false)), qt.Equals, int(42))
+
+	// Setting nil removes a key.
+	m.Set(bool(false), nil)
+	qt.Assert(t, m.Get(bool(false)), qt.IsNil)
+	qt.Assert(t, m.Get(int(1)), qt.Equals, int(1))
+	qt.Assert(t, m.Get(b(false)), qt.Equals, int(42))
+}
+
+func BenchmarkMetadata(b *testing.B) {
+	// Assume that three bits of metadata on a single instruction is
+	// our worst case.
+	const worstCaseItems = 3
+
+	type t struct{}
+
+	b.Run("add first", func(b *testing.B) {
+		b.ReportAllocs()
+
+		for i := 0; i < b.N; i++ {
+			var v Metadata
+			v.Set(t{}, 0)
+		}
+	})
+
+	b.Run("add last", func(b *testing.B) {
+		var m Metadata
+		for i := 0; i < worstCaseItems-1; i++ {
+			m.Set(i, i)
+		}
+
+		b.ReportAllocs()
+		b.ResetTimer()
+
+		for i := 0; i < b.N; i++ {
+			v := m
+			v.Set(t{}, 0)
+		}
+	})
+
+	b.Run("add existing", func(b *testing.B) {
+		var m Metadata
+		for i := 0; i < worstCaseItems-1; i++ {
+			m.Set(i, i)
+		}
+		m.Set(t{}, 0)
+
+		b.ReportAllocs()
+		b.ResetTimer()
+
+		for i := 0; i < b.N; i++ {
+			v := m
+			v.Set(t{}, 0)
+		}
+	})
+
+	b.Run("get miss", func(b *testing.B) {
+		var m Metadata
+		for i := 0; i < worstCaseItems; i++ {
+			m.Set(i, i)
+		}
+
+		b.ReportAllocs()
+		b.ResetTimer()
+
+		for i := 0; i < b.N; i++ {
+			if m.Get(t{}) != nil {
+				b.Fatal("got result from miss")
+			}
+		}
+	})
+}