Measure the costs of context switching for the OS and a Go application

measure_cs.sh

#!/usr/bin/env bash

# Tim Rots - June 2020
#
# This benchmark measures the costs of context switching for the OS and a Go application in usec/op.
#
# Usage:
# $ ./measure_cs.sh
# OS: 2.19416 usec/op
# Go: 0.16 usec/op
# Difference: 86%


# Check dependencies
if [ -z "$(which perf)" ] || [ -z "$(which go)" ] ;
then
	echo "Error - Dependency missing\nEnsure perf and Go are installed correctly."; exit 1
fi

# Ensure Go benchmark
goBenchmark=/tmp/context_switch_test.go
if [ ! -e "${goBenchmark}" ];
then
	cat > "${goBenchmark}"<<EOF
package main

import (
	"sync"
	"testing"
)

func BenchmarkContextSwitch(b *testing.B) {
	var wg sync.WaitGroup
	begin := make(chan struct{})
	c := make(chan struct{})
	var token struct{}

	sender := func() {
		defer wg.Done()
		<-begin
		for i := 0; i < b.N; i++ {
			c <- token
		}
	}
	receiver := func() {
		defer wg.Done()
		<-begin
		for i := 0; i < b.N; i++ {
			<-c
		}
	}
	wg.Add(2)
	go sender()
	go receiver()
	b.StartTimer()
	close(begin)
	wg.Wait()
}
EOF
fi

# Measure context-switch in usec/op
# Print result per test-item, and show difference in %
contextSwitchOs=$(taskset -c 0 perf bench sched pipe -T|awk '/usecs/{print (($1/2))}')
contextSwitchGo=$(go test -bench=. -cpu=1 ${goBenchmark} |awk '/BenchmarkContextSwitch/{print (($3/1000))}')
echo "OS: ${contextSwitchOs} usec/op"
echo "Go: ${contextSwitchGo} usec/op"
echo "${contextSwitchOs}" "${contextSwitchGo}"|awk '{diff = ($1-$2)/($1+$2)*100; print "Difference: "substr(diff,1,2)"%"}'

# Cleanup
rm ${goBenchmark}