use pprof::bass=true to mark diff base samples

doc/README.md

@@ -216,10 +216,6 @@ search for them in a directory pointed to by the environment variable
 * **-weblist= _regex_:** Generates a source/assembly combined annotated listing for
   functions matching *regex*, and starts a web browser to display it.
 
-Samples in a profile may have tags. These tags have a name and a value; this
-value can be either numeric or a string. pprof can select samples from a
-profile based on these tags using the `-tagfocus` and `-tagignore` options.
-
 # Fetching profiles
 
 pprof can read profiles from a file or directly from a URL over http. Its native
@@ -248,13 +244,13 @@ pprof can subtract a profile from another, provided the profiles are of
 compatible types, in order to compare them. For that, use the 
 **-diff_base= _profile_** option, where *profile* is the filename or URL for the
 profile to be subtracted. This may result in some report entries having negative
-values.  Percentages in the report are relative to the total of 
+values. Percentages in the report are relative to the total of 
 the diff base. 
 
-If the merged profile is output as a protocol buffer, all samples in 
-the diff base profile will have a label with the key "base" and a value of "1".
-If pprof is then used to look at the merged profile, it will behave as if 
-separate source and base profiles were passed in. 
+If the merged profile is output as a protocol buffer, all samples in
+the diff base profile will have a label with the key "pprof::base" and a value
+of "true". If pprof is then used to look at the merged profile, it will behave
+as if separate source and base profiles were passed in.
 
 The **-base** option can be used in the place of the **-diff_base** option, and
 may be preferrable when comparing two cumulative profiles, for example two

internal/driver/cli.go

@@ -142,40 +142,51 @@ func parseFlags(o *plugin.Options) (*source, []string, error) {
 		Comment:      *flagAddComment,
 	}
 
-	var base []string
-	for _, s := range *flagBase {
-		if *s != "" {
-			base = append(base, *s)
-		}
+	if err := source.addBaseProfiles(flagBase, flagDiffBase); err != nil {
+		return nil, nil, err
 	}
 
-	var diffBase []string
-	for _, s := range *flagDiffBase {
-		if *s != "" {
-			diffBase = append(diffBase, *s)
-		}
+	normalize := pprofVariables["normalize"].boolValue()
+	if normalize && len(source.Base) == 0 {
+		return nil, nil, fmt.Errorf("Must have base profile to normalize by")
 	}
+	source.Normalize = normalize
+
+	if bu, ok := o.Obj.(*binutils.Binutils); ok {
+		bu.SetTools(*flagTools)
+	}
+	return source, cmd, nil
+}
+
+// addBaseProfiles adds the list of base profiles or diff base profiles to
+// the source. This function will return an error if both base and diff base
+// profiles are specified.
+func (source *source) addBaseProfiles(flagBase, flagDiffBase *[]*string) error {
+	base := parseStringListFlag(flagBase)
+	diffBase := parseStringListFlag(flagDiffBase)
 
 	if len(base) > 0 && len(diffBase) > 0 {
-		return nil, nil, fmt.Errorf("-base and -diff_base flags cannot both be specified")
+		return fmt.Errorf("-base and -diff_base flags cannot both be specified")
 	}
 
 	source.Base = base
 	if len(diffBase) > 0 {
 		source.Base = diffBase
 		source.DiffBase = true
 	}
+	return nil
+}
 
-	normalize := pprofVariables["normalize"].boolValue()
-	if normalize && len(source.Base) == 0 {
-		return nil, nil, fmt.Errorf("Must have base profile to normalize by")
-	}
-	source.Normalize = normalize
-
-	if bu, ok := o.Obj.(*binutils.Binutils); ok {
-		bu.SetTools(*flagTools)
+// parseStringListFlag list takes a StringList flag, and outputs an array of non-empty
+// strings associated with the flag.
+func parseStringListFlag(list *[]*string) []string {
+	var l []string
+	for _, s := range *list {
+		if *s != "" {
+			l = append(l, *s)
+		}
 	}
-	return source, cmd, nil
+	return l
 }
 
 // installFlags creates command line flags for pprof variables.

internal/driver/fetch.go

@@ -136,7 +136,7 @@ func grabSourcesAndBases(sources, bases []profileSource, isDiffBase bool, fetch
 		defer wg.Done()
 		pbase, mbase, savebase, countbase, errbase = chunkedGrab(bases, fetch, obj, ui)
 		if pbase != nil && isDiffBase {
-			pbase.SetTag("base", []string{"1"})
+			pbase.SetTag("pprof::base", []string{"true"})
 		}
 	}()
 	wg.Wait()

internal/driver/fetch_test.go

@@ -398,27 +398,27 @@ func TestFetchWithBase(t *testing.T) {
 				},
 				{
 					values: []int64{-2700, -608881724},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 				{
 					values: []int64{-100, -23992},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 				{
 					values: []int64{-200, -179943},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 				{
 					values: []int64{-100, -17778444},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 				{
 					values: []int64{-100, -75976},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 				{
 					values: []int64{-300, -63568134},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 			},
 			"",

internal/report/report.go

@@ -266,7 +266,7 @@ func (rpt *Report) newGraph(nodes graph.NodeSet) *graph.Graph {
 
 	// Remove tag marking samples from the base profiles, so it does not appear
 	// as a nodelet in the graph view.
-	prof.SetTag("base", []string{})
+	prof.SetTag("pprof::base", []string{})
 
 	formatTag := func(v int64, key string) string {
 		return measurement.ScaledLabel(v, key, o.OutputUnit)
@@ -1217,7 +1217,7 @@ func NewDefault(prof *profile.Profile, options Options) *Report {
 }
 
 // computeTotal computes the sum of the absolute value of all sample values.
-// If any samples have the tag "base" with value "1", then the total
+// If any samples have the tag "pprof::base" with value "true", then the total
 // will only include samples with that tag.
 func computeTotal(prof *profile.Profile, value, meanDiv func(v []int64) int64) int64 {
 	var div, total, diffDiv, diffTotal int64
@@ -1231,11 +1231,11 @@ func computeTotal(prof *profile.Profile, value, meanDiv func(v []int64) int64) i
 			v = -v
 		}
 		total += v
-		if sample.HasTag("base", "1") {
+		div += d
+		if sample.HasTag("pprof::base", "true") {
 			diffTotal += v
 			diffDiv += d
 		}
-		div += d
 	}
 	if diffTotal > 0 {
 		total = diffTotal

internal/report/report_test.go

@@ -330,7 +330,7 @@ func TestComputeTotal(t *testing.T) {
 		{
 			Location: []*profile.Location{testL[2], testL[1], testL[0]},
 			Value:    []int64{-10, 3},
-			Label:    map[string][]string{"base": {"1"}},
+			Label:    map[string][]string{"pprof::base": {"true"}},
 		},
 		{
 			Location: []*profile.Location{testL[2], testL[1], testL[0]},
@@ -339,12 +339,12 @@ func TestComputeTotal(t *testing.T) {
 		{
 			Location: []*profile.Location{testL[2], testL[1], testL[0]},
 			Value:    []int64{-9000, 3},
-			Label:    map[string][]string{"base": {"1"}},
+			Label:    map[string][]string{"pprof::base": {"true"}},
 		},
 		{
 			Location: []*profile.Location{testL[2], testL[1], testL[0]},
 			Value:    []int64{-1, 3},
-			Label:    map[string][]string{"base": {"1"}},
+			Label:    map[string][]string{"pprof::base": {"true"}},
 		},
 		{
 			Location: []*profile.Location{testL[4], testL[2], testL[0]},
@@ -353,7 +353,7 @@ func TestComputeTotal(t *testing.T) {
 		{
 			Location: []*profile.Location{testL[2], testL[1], testL[0]},
 			Value:    []int64{100, 3},
-			Label:    map[string][]string{"base": {"1"}},
+			Label:    map[string][]string{"pprof::base": {"true"}},
 		},
 	}
 

profile/profile.go

@@ -679,7 +679,7 @@ func numLabelsToString(numLabels map[string][]int64, numUnits map[string][]strin
 func (p *Profile) SetTag(key string, value []string) {
 	for _, sample := range p.Sample {
 		if sample.Label == nil {
-			sample.Label = make(map[string][]string)
+			sample.Label = map[string][]string{}
 		}
 		sample.Label[key] = value
 	}