Add a folded stacks output format

Fixes #658

doc/README.md

@@ -171,6 +171,8 @@ pprof text reports show the location hierarchy in text format.
 * **-peek= _regex_:** Print the location entry with all its predecessors and
   successors, without trimming any entries.
 * **-traces:** Prints each sample with a location per line.
+* **-folded:** Prints each sample in [Brendan Gregg's Folded Stacks
+  format](https://queue.acm.org/detail.cfm?id=2927301#:~:text=The%20folded%20stack%2Dtrace%20format,trace%2C%20followed%20by%20a%20semicolon.).
 
 ## Graphical reports
 

internal/driver/commands.go

@@ -93,6 +93,7 @@ var pprofCommands = commands{
 	"top":      {report.Text, nil, nil, false, "Outputs top entries in text form", reportHelp("top", true, true)},
 	"traces":   {report.Traces, nil, nil, false, "Outputs all profile samples in text form", ""},
 	"tree":     {report.Tree, nil, nil, false, "Outputs a text rendering of call graph", reportHelp("tree", true, true)},
+	"folded":   {report.Folded, nil, nil, false, "Outputs entries in folded stack form", reportHelp("folded", false, true)},
 
 	// Save binary formats to a file
 	"callgrind": {report.Callgrind, nil, awayFromTTY("callgraph.out"), false, "Outputs a graph in callgrind format", reportHelp("callgrind", false, true)},

internal/report/report.go

@@ -48,6 +48,7 @@ const (
 	Traces
 	Tree
 	WebList
+	Folded
 )
 
 // Options are the formatting and filtering options used to generate a
@@ -94,6 +95,8 @@ func Generate(w io.Writer, rpt *Report, obj plugin.ObjTool) error {
 		return printDOT(w, rpt)
 	case Tree:
 		return printTree(w, rpt)
+	case Folded:
+		return printFolded(w, rpt)
 	case Text:
 		return printText(w, rpt)
 	case Traces:
@@ -828,6 +831,55 @@ func printText(w io.Writer, rpt *Report) error {
 	return nil
 }
 
+// printFolded prints a profile in Brendan Gregg's Folded Stacks format.
+func printFolded(w io.Writer, rpt *Report) error {
+	prof := rpt.prof
+	o := rpt.options
+
+	_, locations := graph.CreateNodes(prof, &graph.Options{})
+	for _, sample := range prof.Sample {
+		var stack []*graph.NodeInfo
+		for _, loc := range sample.Location {
+			nodes := locations[loc.ID]
+			for _, n := range nodes {
+				stack = append(stack, &n.Info)
+			}
+		}
+
+		if len(stack) == 0 {
+			continue
+		}
+
+		var d, v int64
+		v = o.SampleValue(sample.Value)
+		if o.SampleMeanDivisor != nil {
+			d = o.SampleMeanDivisor(sample.Value)
+		}
+		if d != 0 {
+			v = v / d
+		}
+		// Print call stack.
+		for i := range stack {
+			// Folded stack convention: start with root frame, end
+			// with leaves.
+			s := stack[len(stack)-i-1]
+			if i > 0 {
+				fmt.Fprint(w, ";")
+			}
+			// TODO: should we print more than just s.Name?
+			// NodeInfo.PrintableName() has a lot more.
+
+			// Remove semicolons and newlines.
+			name := strings.ReplaceAll(s.Name, ";", "")
+			name = strings.ReplaceAll(s.Name, "\n", "")
+			fmt.Fprint(w, name)
+		}
+		// We just want a raw number, so don't use rpt.formatValue().
+		fmt.Fprintf(w, " %d\n", v)
+	}
+	return nil
+}
+
 // printTraces prints all traces from a profile.
 func printTraces(w io.Writer, rpt *Report) error {
 	fmt.Fprintln(w, strings.Join(ProfileLabels(rpt), "\n"))

internal/report/report_test.go

@@ -36,6 +36,9 @@ type testcase struct {
 func TestTextReports(t *testing.T) {
 	const path = "testdata/"
 
+	sampleValue0 := func(v []int64) int64 {
+		return v[0]
+	}
 	sampleValue1 := func(v []int64) int64 {
 		return v[1]
 	}
@@ -70,6 +73,43 @@ func TestTextReports(t *testing.T) {
 			),
 			want: path + "report.dot",
 		},
+		{
+			rpt: New(
+				testProfile.Copy(),
+				&Options{
+					OutputFormat: Folded,
+
+					SampleValue: sampleValue1,
+					SampleUnit:  testProfile.SampleType[1].Unit,
+				},
+			),
+			want: path + "report.folded",
+		},
+		{
+			rpt: New(
+				testProfile.Copy(),
+				&Options{
+					OutputFormat: Folded,
+
+					SampleValue: sampleValue0,
+					SampleUnit:  testProfile.SampleType[0].Unit,
+				},
+			),
+			want: path + "report0.folded",
+		},
+		{
+			rpt: New(
+				testProfile.Copy(),
+				&Options{
+					OutputFormat: Folded,
+
+					SampleValue:       sampleValue1,
+					SampleUnit:        testProfile.SampleType[1].Unit,
+					SampleMeanDivisor: sampleValue0,
+				},
+			),
+			want: path + "report_mean.folded",
+		},
 	} {
 		var b bytes.Buffer
 		if err := Generate(&b, tc.rpt, &binutils.Binutils{}); err != nil {
@@ -259,7 +299,7 @@ var testProfile = &profile.Profile{
 		},
 		{
 			Location: []*profile.Location{testL[4], testL[3], testL[0]},
-			Value:    []int64{1, 10000},
+			Value:    []int64{2, 10000},
 		},
 	},
 	Location: testL,

internal/report/testdata/report.folded

@@ -0,0 +1,5 @@
+main 1
+main;foo;bar 10
+main;bar;tee 100
+main;tee 1000
+main;tee;tee 10000

internal/report/testdata/report0.folded

@@ -0,0 +1,5 @@
+main 1
+main;foo;bar 1
+main;bar;tee 1
+main;tee 1
+main;tee;tee 2

internal/report/testdata/report_mean.folded

@@ -0,0 +1,5 @@
+main 1
+main;foo;bar 10
+main;bar;tee 100
+main;tee 1000
+main;tee;tee 5000