Add simple block bias example

examples/block-bias/go.mod

@@ -0,0 +1,5 @@
+module github.com/felixge/go-profiler-notes/examples/block-bias
+
+go 1.15
+
+require golang.org/x/sync v0.0.0-20201207232520-09787c993a3a

examples/block-bias/go.sum

@@ -0,0 +1,2 @@
+golang.org/x/sync v0.0.0-20201207232520-09787c993a3a h1:DcqTD9SDLc+1P/r1EmRBwnVsrOwW+kk2vWf9n+1sGhs=
+golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

examples/block-bias/main.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"runtime/pprof"
+	"sync"
+	"time"
+)
+
+func main() {
+	if err := run(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+var (
+	fastEventDuration = 1 * time.Millisecond
+	slowEventDuration = 1 * fastEventDuration
+)
+
+func run() error {
+	runtime.SetBlockProfileRate(int(slowEventDuration.Nanoseconds()))
+
+	var (
+		done = make(chan struct{})
+		wg   = &sync.WaitGroup{}
+	)
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		slowEvent(done)
+	}()
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		fastEvent(done)
+	}()
+	time.Sleep(1 * time.Second)
+	close(done)
+	wg.Wait()
+
+	f, err := os.Create("block.pb.gz")
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if err := pprof.Lookup("block").WriteTo(f, 0); err != nil {
+		return err
+	}
+	return nil
+}
+
+func slowEvent(done chan struct{}) error {
+	return simulateBlockEvents(slowEventDuration, done)
+}
+
+func fastEvent(done chan struct{}) error {
+	return simulateBlockEvents(fastEventDuration, done)
+}
+
+func simulateBlockEvents(duration time.Duration, done chan struct{}) error {
+	ticker := time.NewTicker(duration)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.C:
+			// do nothing
+		case <-done:
+			return nil
+		}
+	}
+}