initial commit

.gitignore

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+.idea
+data
+plot.html

README.md

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+# fat contexts
+
+This repo holds code for [On context-induced performance bottleneck in Go](https://gabnotes.org/fat-contexts/).
+
+Reproduce my results:
+
+```console
+$ go test -bench=.
+goos: darwin
+goarch: arm64
+pkg: trash
+BenchmarkContext/shadow_1000-8         	   19352	     61271 ns/op
+BenchmarkContext/fat_1000-8            	     532	   2187010 ns/op
+BenchmarkContext/shadow_10000-8        	    1903	    639371 ns/op
+BenchmarkContext/fat_10000-8           	       5	 219400100 ns/op
+BenchmarkContext/shadow_100000-8       	     194	   6374344 ns/op
+BenchmarkContext/fat_100000-8          	       1	21851940167 ns/op
+PASS
+ok  	trash	30.801s
+$ go run ./generate/main.go > data
+$ go run ./plot/main.go
+$ open plot.html
+```
+
+Sorry there are a lot of hardcoded file names in here, but since I don't intend on reusing this code I won't fix it.

bench_test.go

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+package main_test
+
+import (
+	"context"
+	"fmt"
+	"math/rand/v2"
+	"testing"
+)
+
+const key = "key"
+
+func BenchmarkContext(b *testing.B) {
+	benchmarks := []struct {
+		times uint64
+	}{
+		{1_000},
+		{10_000},
+		{100_000},
+	}
+	for _, bm := range benchmarks {
+		ctx := context.WithValue(context.Background(), key, "some value")
+		b.Run(fmt.Sprintf("shadow %v", bm.times), func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				shadow(ctx, bm.times)
+			}
+		})
+		b.Run(fmt.Sprintf("fat %v", bm.times), func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				fat(ctx, bm.times)
+			}
+		})
+	}
+}
+
+func shadow(ctx context.Context, times uint64) {
+	for range times {
+		ctx := contextWithRandom(ctx)
+		_ = ctx.Value(key)
+	}
+}
+
+func fat(ctx context.Context, times uint64) {
+	for range times {
+		ctx = contextWithRandom(ctx)
+		_ = ctx.Value(key)
+	}
+}
+
+func contextWithRandom(ctx context.Context) context.Context {
+	return context.WithValue(ctx, "other_key", rand.Int64())
+}

generate/main.go

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+package main
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/gofrs/uuid"
+)
+
+const key = "key"
+
+func main() {
+	const times = 10_000
+
+	// Setup the value we want to retrieve in each iteration
+	ctx := context.WithValue(context.Background(), key, "some-val")
+
+	fat(ctx, times)
+	shadow(ctx, times)
+}
+
+func fat(ctx context.Context, times uint64) {
+	for range times {
+		// wrap the context, each iteration makes it bigger
+		ctx = contextWithRandom(ctx)
+
+		start := time.Now()
+		// simulate the logging lib which retrieves context values
+		_ = ctx.Value(key)
+
+		fmt.Printf("fat,%v\n", time.Since(start).Nanoseconds())
+	}
+}
+
+func shadow(ctx context.Context, times uint64) {
+	for range times {
+		// shadow the context, each iteration creates a new one and it doesn't grow
+		ctx := contextWithRandom(ctx)
+
+		start := time.Now()
+		_ = ctx.Value(key)
+
+		fmt.Printf("shadow,%v\n", time.Since(start).Nanoseconds())
+	}
+}
+
+func contextWithRandom(ctx context.Context) context.Context {
+	return context.WithValue(ctx, "other_key", uuid.Must(uuid.NewV4()))
+}

go.mod

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+module trash
+
+go 1.22.0
+
+require (
+	github.com/go-echarts/go-echarts/v2 v2.3.3
+	github.com/gofrs/uuid v4.4.0+incompatible
+)

go.sum

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+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-echarts/go-echarts/v2 v2.3.3 h1:uImZAk6qLkC6F9ju6mZ5SPBqTyK8xjZKwSmwnCg4bxg=
+github.com/go-echarts/go-echarts/v2 v2.3.3/go.mod h1:56YlvzhW/a+du15f3S2qUGNDfKnFOeJSThBIrVFHDtI=
+github.com/gofrs/uuid v4.4.0+incompatible h1:3qXRTX8/NbyulANqlc0lchS1gqAVxRgsuW1YrTJupqA=
+github.com/gofrs/uuid v4.4.0+incompatible/go.mod h1:b2aQJv3Z4Fp6yNu3cdSllBxTCLRxnplIgP/c0N/04lM=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.6.0 h1:jlIyCplCJFULU/01vCkhKuTyc3OorI3bJFuw6obfgho=
+github.com/stretchr/testify v1.6.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/yaml.v3 v3.0.0 h1:hjy8E9ON/egN1tAYqKb61G10WtihqetD4sz2H+8nIeA=
+gopkg.in/yaml.v3 v3.0.0/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

plot/main.go

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+package main
+
+import (
+	"encoding/csv"
+	"github.com/go-echarts/go-echarts/v2/charts"
+	"github.com/go-echarts/go-echarts/v2/opts"
+	"io"
+	"log"
+	"os"
+	"strconv"
+)
+
+func main() {
+	shadow, fat := getData()
+	plot := charts.NewLine()
+	xAxis := make([]int, len(shadow))
+	for i := range xAxis {
+		xAxis[i] = i
+	}
+
+	plot.SetGlobalOptions(
+		charts.WithXAxisOpts(opts.XAxis{Name: "loop count"}),
+		charts.WithYAxisOpts(opts.YAxis{Name: "Nanosecond"}),
+	)
+
+	plot.
+		SetXAxis(xAxis).
+		AddSeries("Shadow", shadow).
+		AddSeries("Fat", fat)
+
+	f, err := os.Create("plot.html")
+	if err != nil {
+		panic(err)
+	}
+	err = plot.Render(f)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func getData() ([]opts.LineData, []opts.LineData) {
+	var shadow []opts.LineData
+	var fat []opts.LineData
+
+	f, err := os.Open("data")
+	if err != nil {
+		panic(err)
+	}
+
+	r := csv.NewReader(f)
+	for {
+		record, err := r.Read()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		series := record[0]
+		val, err := strconv.ParseUint(record[1], 10, 64)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		point := opts.LineData{Value: val, Name: "ns"}
+
+		switch series {
+		case "shadow":
+			shadow = append(shadow, point)
+		case "fat":
+			fat = append(fat, point)
+		}
+	}
+
+	return shadow, fat
+}