runtime/pprof: add tests for tracer

Change-Id: I832a433f0f2fc10b0a2fea0bfb003a988fc2c81b
Reviewed-on: https://go-review.googlesource.com/2039Reviewed-by: Russ Cox <rsc@golang.org>

src/runtime/pprof/trace_test.go

+// Copyright 2014 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package pprof_test
+
+import (
+	"bytes"
+	"net"
+	"os"
+	"runtime"
+	. "runtime/pprof"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestTraceStartStop(t *testing.T) {
+	buf := new(bytes.Buffer)
+	if err := StartTrace(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+	StopTrace()
+	size := buf.Len()
+	if size == 0 {
+		t.Fatalf("trace is empty")
+	}
+	time.Sleep(100 * time.Millisecond)
+	if size != buf.Len() {
+		t.Fatalf("trace writes after stop: %v -> %v", size, buf.Len())
+	}
+}
+
+func TestTraceDoubleStart(t *testing.T) {
+	StopTrace()
+	buf := new(bytes.Buffer)
+	if err := StartTrace(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+	if err := StartTrace(buf); err == nil {
+		t.Fatalf("succeed to start tracing second time")
+	}
+	StopTrace()
+	StopTrace()
+}
+
+func TestTrace(t *testing.T) {
+	buf := new(bytes.Buffer)
+	if err := StartTrace(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+	StopTrace()
+	_, err := parseTrace(buf)
+	if err != nil {
+		t.Fatalf("failed to parse trace: %v", err)
+	}
+}
+
+func TestTraceStress(t *testing.T) {
+	var wg sync.WaitGroup
+	done := make(chan bool)
+
+	// Create a goroutine blocked before tracing.
+	wg.Add(1)
+	go func() {
+		<-done
+		wg.Done()
+	}()
+
+	// Create a goroutine blocked in syscall before tracing.
+	rp, wp, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("failed to create pipe: %v", err)
+	}
+	defer func() {
+		rp.Close()
+		wp.Close()
+	}()
+	wg.Add(1)
+	go func() {
+		var tmp [1]byte
+		rp.Read(tmp[:])
+		<-done
+		wg.Done()
+	}()
+	time.Sleep(time.Millisecond)
+
+	buf := new(bytes.Buffer)
+	if err := StartTrace(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+
+	procs := runtime.GOMAXPROCS(10)
+
+	go func() {
+		runtime.LockOSThread()
+		for {
+			select {
+			case <-done:
+				return
+			default:
+				runtime.Gosched()
+			}
+		}
+	}()
+
+	runtime.GC()
+	// Trigger GC from malloc.
+	for i := 0; i < 1e3; i++ {
+		_ = make([]byte, 1<<20)
+	}
+
+	// Create a bunch of busy goroutines to load all Ps.
+	for p := 0; p < 10; p++ {
+		wg.Add(1)
+		go func() {
+			// Do something useful.
+			tmp := make([]byte, 1<<16)
+			for i := range tmp {
+				tmp[i]++
+			}
+			_ = tmp
+			<-done
+			wg.Done()
+		}()
+	}
+
+	// Block in syscall.
+	wg.Add(1)
+	go func() {
+		var tmp [1]byte
+		rp.Read(tmp[:])
+		<-done
+		wg.Done()
+	}()
+
+	// Test timers.
+	timerDone := make(chan bool)
+	go func() {
+		time.Sleep(time.Millisecond)
+		timerDone <- true
+	}()
+	<-timerDone
+
+	// A bit of network.
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen failed: %v", err)
+	}
+	defer ln.Close()
+	go func() {
+		c, err := ln.Accept()
+		if err != nil {
+			return
+		}
+		time.Sleep(time.Millisecond)
+		var buf [1]byte
+		c.Write(buf[:])
+		c.Close()
+	}()
+	c, err := net.Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("dial failed: %v", err)
+	}
+	var tmp [1]byte
+	c.Read(tmp[:])
+	c.Close()
+
+	go func() {
+		runtime.Gosched()
+		select {}
+	}()
+
+	// Unblock helper goroutines and wait them to finish.
+	wp.Write(tmp[:])
+	wp.Write(tmp[:])
+	close(done)
+	wg.Wait()
+
+	runtime.GOMAXPROCS(procs)
+
+	StopTrace()
+	_, err = parseTrace(buf)
+	if err != nil {
+		t.Fatalf("failed to parse trace: %v", err)
+	}
+}
+
+func TestTraceSymbolize(t *testing.T) {
+	buf := new(bytes.Buffer)
+	if err := StartTrace(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+	runtime.GC()
+	StopTrace()
+	events, err := parseTrace(buf)
+	if err != nil {
+		t.Fatalf("failed to parse trace: %v", err)
+	}
+	err = symbolizeTrace(events, os.Args[0])
+	if err != nil {
+		t.Fatalf("failed to symbolize trace: %v", err)
+	}
+	found := false
+eventLoop:
+	for _, ev := range events {
+		if ev.typ != traceEvGCStart {
+			continue
+		}
+		for _, f := range ev.stk {
+			if strings.HasSuffix(f.file, "trace_test.go") &&
+				strings.HasSuffix(f.fn, "pprof_test.TestTraceSymbolize") &&
+				f.line == 195 {
+				found = true
+				break eventLoop
+			}
+		}
+	}
+	if !found {
+		t.Fatalf("the trace does not contain GC event")
+	}
+}