From 7ffdb757758c086556e5eba277202d9d8940c2bd Mon Sep 17 00:00:00 2001
From: "Bryan C. Mills" <bcmills@google.com>
Date: Tue, 14 Feb 2017 01:00:49 -0500
Subject: [PATCH] expvar: add benchmarks for steady-state Map Add calls

Add a benchmark for setting a String value, which we may
want to treat differently from Int or Float due to the need to support
Add methods for the latter.

Update tests to use only the exported API instead of making (fragile)
assumptions about unexported fields.

The existing Map benchmarks construct a new Map for each iteration, which
focuses the benchmark results on the initial allocation costs for the
Map and its entries. This change adds variants of the benchmarks which
use a long-lived map in order to measure steady-state performance for
Map updates on existing keys.

Updates #18177

Change-Id: I62c920991d17d5898c592446af382cd5c04c528a
Reviewed-on: https://go-review.googlesource.com/36959
Reviewed-by: Ian Lance Taylor <iant@golang.org>
---
 src/expvar/expvar_test.go | 79 +++++++++++++++++++++++++++++----------
 1 file changed, 59 insertions(+), 20 deletions(-)

diff --git a/src/expvar/expvar_test.go b/src/expvar/expvar_test.go
index 2a4a21ec7b..901d72201a 100644
--- a/src/expvar/expvar_test.go
+++ b/src/expvar/expvar_test.go
@@ -38,8 +38,8 @@ func TestNil(t *testing.T) {
 func TestInt(t *testing.T) {
 	RemoveAll()
 	reqs := NewInt("requests")
-	if reqs.i != 0 {
-		t.Errorf("reqs.i = %v, want 0", reqs.i)
+	if i := reqs.Value(); i != 0 {
+		t.Errorf("reqs.Value() = %v, want 0", i)
 	}
 	if reqs != Get("requests").(*Int) {
 		t.Errorf("Get() failed.")
@@ -47,8 +47,8 @@ func TestInt(t *testing.T) {
 
 	reqs.Add(1)
 	reqs.Add(3)
-	if reqs.i != 4 {
-		t.Errorf("reqs.i = %v, want 4", reqs.i)
+	if i := reqs.Value(); i != 4 {
+		t.Errorf("reqs.Value() = %v, want 4", i)
 	}
 
 	if s := reqs.String(); s != "4" {
@@ -56,12 +56,8 @@ func TestInt(t *testing.T) {
 	}
 
 	reqs.Set(-2)
-	if reqs.i != -2 {
-		t.Errorf("reqs.i = %v, want -2", reqs.i)
-	}
-
-	if v, want := reqs.Value(), int64(-2); v != want {
-		t.Errorf("reqs.Value() = %q, want %q", v, want)
+	if i := reqs.Value(); i != -2 {
+		t.Errorf("reqs.Value() = %v, want -2", i)
 	}
 }
 
@@ -134,19 +130,14 @@ func BenchmarkFloatSet(b *testing.B) {
 func TestString(t *testing.T) {
 	RemoveAll()
 	name := NewString("my-name")
-	if name.s != "" {
-		t.Errorf("name.s = %q, want \"\"", name.s)
+	if name.Value() != "" {
+		t.Errorf("name.Value() = %q, want \"\"", name.s)
 	}
 
 	name.Set("Mike")
-	if name.s != "Mike" {
-		t.Errorf("name.s = %q, want \"Mike\"", name.s)
-	}
-
 	if s, want := name.String(), `"Mike"`; s != want {
 		t.Errorf("from %q, name.String() = %q, want %q", name.s, s, want)
 	}
-
 	if s, want := name.Value(), "Mike"; s != want {
 		t.Errorf("from %q, name.Value() = %q, want %q", name.s, s, want)
 	}
@@ -176,13 +167,13 @@ func TestMapCounter(t *testing.T) {
 	colors.Add("red", 2)
 	colors.Add("blue", 4)
 	colors.AddFloat(`green "midori"`, 4.125)
-	if x := colors.m["red"].(*Int).i; x != 3 {
+	if x := colors.Get("red").(*Int).Value(); x != 3 {
 		t.Errorf("colors.m[\"red\"] = %v, want 3", x)
 	}
-	if x := colors.m["blue"].(*Int).i; x != 4 {
+	if x := colors.Get("blue").(*Int).Value(); x != 4 {
 		t.Errorf("colors.m[\"blue\"] = %v, want 4", x)
 	}
-	if x := colors.m[`green "midori"`].(*Float).Value(); x != 4.125 {
+	if x := colors.Get(`green "midori"`).(*Float).Value(); x != 4.125 {
 		t.Errorf("colors.m[`green \"midori\"] = %v, want 4.125", x)
 	}
 
@@ -220,6 +211,19 @@ func BenchmarkMapSet(b *testing.B) {
 	})
 }
 
+func BenchmarkMapSetString(b *testing.B) {
+	m := new(Map).Init()
+
+	v := new(String)
+	v.Set("Hello, !")
+
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			m.Set("red", v)
+		}
+	})
+}
+
 func BenchmarkMapAddSame(b *testing.B) {
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
@@ -258,6 +262,41 @@ func BenchmarkMapAddDifferent(b *testing.B) {
 	})
 }
 
+func BenchmarkMapAddSameSteadyState(b *testing.B) {
+	m := new(Map).Init()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			m.Add("red", 1)
+		}
+	})
+}
+
+func BenchmarkMapAddDifferentSteadyState(b *testing.B) {
+	procKeys := make([][]string, runtime.GOMAXPROCS(0))
+	for i := range procKeys {
+		keys := make([]string, 4)
+		for j := range keys {
+			keys[j] = fmt.Sprint(i, j)
+		}
+		procKeys[i] = keys
+	}
+
+	m := new(Map).Init()
+	b.ResetTimer()
+
+	var n int32
+	b.RunParallel(func(pb *testing.PB) {
+		i := int(atomic.AddInt32(&n, 1)-1) % len(procKeys)
+		keys := procKeys[i]
+
+		for pb.Next() {
+			for _, k := range keys {
+				m.Add(k, 1)
+			}
+		}
+	})
+}
+
 func TestFunc(t *testing.T) {
 	RemoveAll()
 	var x interface{} = []string{"a", "b"}