cmd/trace: add option to output pprof files

The trace tool can generate some interesting profiles, but it was only
exposing them as svg through the web UI.  This adds command line options
to generate the raw pprof file.

Change-Id: I52e4f909fdca6f65c3616add444e3892783640f4
Reviewed-on: https://go-review.googlesource.com/23324
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/trace/main.go

@@ -15,6 +15,14 @@ Generate a trace file with 'go test':
 	go test -trace trace.out pkg
 View the trace in a web browser:
 	go tool trace trace.out
+Generate a pprof-like profile from the trace:
+	go tool trace -pprof=TYPE trace.out > TYPE.pprof
+
+Supported profile types are:
+	- net: network blocking profile
+	- sync: synchronization blocking profile
+	- syscall: syscall blocking profile
+	- sched: scheduler latency profile
 */
 package main
 
@@ -25,6 +33,7 @@ import (
 	"fmt"
 	"html/template"
 	"internal/trace"
+	"io"
 	"log"
 	"net"
 	"net/http"
@@ -39,15 +48,27 @@ Given a trace file produced by 'go test':
 
 Open a web browser displaying trace:
 	go tool trace [flags] [pkg.test] trace.out
+
+Generate a pprof-like profile from the trace:
+    go tool trace -pprof=TYPE [pkg.test] trace.out
+
 [pkg.test] argument is required for traces produced by Go 1.6 and below.
 Go 1.7 does not require the binary argument.
 
+Supported profile types are:
+    - net: network blocking profile
+    - sync: synchronization blocking profile
+    - syscall: syscall blocking profile
+    - sched: scheduler latency profile
+
 Flags:
 	-http=addr: HTTP service address (e.g., ':6060')
+	-pprof=type: print a pprof-like profile instead
 `
 
 var (
 	httpFlag  = flag.String("http", "localhost:0", "HTTP service address (e.g., ':6060')")
+	pprofFlag = flag.String("pprof", "", "print a pprof-like profile instead")
 
 	// The binary file name, left here for serveSVGProfile.
 	programBinary string
@@ -73,6 +94,27 @@ func main() {
 		flag.Usage()
 	}
 
+	var pprofFunc func(io.Writer) error
+	switch *pprofFlag {
+	case "net":
+		pprofFunc = pprofIO
+	case "sync":
+		pprofFunc = pprofBlock
+	case "syscall":
+		pprofFunc = pprofSyscall
+	case "sched":
+		pprofFunc = pprofSched
+	}
+	if pprofFunc != nil {
+		if err := pprofFunc(os.Stdout); err != nil {
+			dief("failed to generate pprof: %v\n", err)
+		}
+		os.Exit(0)
+	}
+	if *pprofFlag != "" {
+		dief("unknown pprof type %s\n", *pprofFlag)
+	}
+
 	ln, err := net.Listen("tcp", *httpFlag)
 	if err != nil {
 		dief("failed to create server socket: %v\n", err)

src/cmd/trace/pprof.go

@@ -11,6 +11,7 @@ import (
 	"cmd/internal/pprof/profile"
 	"fmt"
 	"internal/trace"
+	"io"
 	"io/ioutil"
 	"net/http"
 	"os"
@@ -18,10 +19,10 @@ import (
 )
 
 func init() {
-	http.HandleFunc("/io", httpIO)
-	http.HandleFunc("/block", httpBlock)
-	http.HandleFunc("/syscall", httpSyscall)
-	http.HandleFunc("/sched", httpSched)
+	http.HandleFunc("/io", serveSVGProfile(pprofIO))
+	http.HandleFunc("/block", serveSVGProfile(pprofBlock))
+	http.HandleFunc("/syscall", serveSVGProfile(pprofSyscall))
+	http.HandleFunc("/sched", serveSVGProfile(pprofSched))
 }
 
 // Record represents one entry in pprof-like profiles.
@@ -31,12 +32,11 @@ type Record struct {
 	time int64
 }
 
-// httpIO serves IO pprof-like profile (time spent in IO wait).
-func httpIO(w http.ResponseWriter, r *http.Request) {
+// pprofIO generates IO pprof-like profile (time spent in IO wait).
+func pprofIO(w io.Writer) error {
 	events, err := parseEvents()
 	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
+		return err
 	}
 	prof := make(map[uint64]Record)
 	for _, ev := range events {
@@ -49,15 +49,14 @@ func httpIO(w http.ResponseWriter, r *http.Request) {
 		rec.time += ev.Link.Ts - ev.Ts
 		prof[ev.StkID] = rec
 	}
-	serveSVGProfile(w, r, prof)
+	return buildProfile(prof).Write(w)
 }
 
-// httpBlock serves blocking pprof-like profile (time spent blocked on synchronization primitives).
-func httpBlock(w http.ResponseWriter, r *http.Request) {
+// pprofBlock generates blocking pprof-like profile (time spent blocked on synchronization primitives).
+func pprofBlock(w io.Writer) error {
 	events, err := parseEvents()
 	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
+		return err
 	}
 	prof := make(map[uint64]Record)
 	for _, ev := range events {
@@ -76,15 +75,14 @@ func httpBlock(w http.ResponseWriter, r *http.Request) {
 		rec.time += ev.Link.Ts - ev.Ts
 		prof[ev.StkID] = rec
 	}
-	serveSVGProfile(w, r, prof)
+	return buildProfile(prof).Write(w)
 }
 
-// httpSyscall serves syscall pprof-like profile (time spent blocked in syscalls).
-func httpSyscall(w http.ResponseWriter, r *http.Request) {
+// pprofSyscall generates syscall pprof-like profile (time spent blocked in syscalls).
+func pprofSyscall(w io.Writer) error {
 	events, err := parseEvents()
 	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
+		return err
 	}
 	prof := make(map[uint64]Record)
 	for _, ev := range events {
@@ -97,16 +95,15 @@ func httpSyscall(w http.ResponseWriter, r *http.Request) {
 		rec.time += ev.Link.Ts - ev.Ts
 		prof[ev.StkID] = rec
 	}
-	serveSVGProfile(w, r, prof)
+	return buildProfile(prof).Write(w)
 }
 
-// httpSched serves scheduler latency pprof-like profile
+// pprofSched generates scheduler latency pprof-like profile
 // (time between a goroutine become runnable and actually scheduled for execution).
-func httpSched(w http.ResponseWriter, r *http.Request) {
+func pprofSched(w io.Writer) error {
 	events, err := parseEvents()
 	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
+		return err
 	}
 	prof := make(map[uint64]Record)
 	for _, ev := range events {
@@ -120,15 +117,12 @@ func httpSched(w http.ResponseWriter, r *http.Request) {
 		rec.time += ev.Link.Ts - ev.Ts
 		prof[ev.StkID] = rec
 	}
-	serveSVGProfile(w, r, prof)
+	return buildProfile(prof).Write(w)
 }
 
-// generateSVGProfile generates pprof-like profile stored in prof and writes in to w.
-func serveSVGProfile(w http.ResponseWriter, r *http.Request, prof map[uint64]Record) {
-	if len(prof) == 0 {
-		http.Error(w, "The profile is empty", http.StatusNotFound)
-		return
-	}
+// serveSVGProfile serves pprof-like profile generated by prof as svg.
+func serveSVGProfile(prof func(w io.Writer) error) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
 		blockf, err := ioutil.TempFile("", "block")
 		if err != nil {
 			http.Error(w, fmt.Sprintf("failed to create temp file: %v", err), http.StatusInternalServerError)
@@ -139,8 +133,8 @@ func serveSVGProfile(w http.ResponseWriter, r *http.Request, prof map[uint64]Rec
 			os.Remove(blockf.Name())
 		}()
 		blockb := bufio.NewWriter(blockf)
-	if err := buildProfile(prof).Write(blockb); err != nil {
-		http.Error(w, fmt.Sprintf("failed to write profile: %v", err), http.StatusInternalServerError)
+		if err := prof(blockb); err != nil {
+			http.Error(w, fmt.Sprintf("failed to generate profile: %v", err), http.StatusInternalServerError)
 			return
 		}
 		if err := blockb.Flush(); err != nil {
@@ -159,6 +153,7 @@ func serveSVGProfile(w http.ResponseWriter, r *http.Request, prof map[uint64]Rec
 		defer os.Remove(svgFilename)
 		w.Header().Set("Content-Type", "image/svg+xml")
 		http.ServeFile(w, r, svgFilename)
+	}
 }
 
 func buildProfile(prof map[uint64]Record) *profile.Profile {