offcpu: Fix incorrect OffTimes values in offcpu profiling.

reporter/internal/pdata/generate.go

@@ -5,8 +5,8 @@ package pdata // import "go.opentelemetry.io/ebpf-profiler/reporter/internal/pda
 
 import (
 	"fmt"
+	"math"
 	"path/filepath"
-	"slices"
 	"time"
 
 	log "github.com/sirupsen/logrus"
@@ -129,14 +129,15 @@ func (p *Pdata) setProfile(
 	attrMgr := samples.NewAttrTableManager(dic.AttributeTable())
 
 	locationIndex := int32(profile.LocationIndices().Len())
-	var startTS, endTS pcommon.Timestamp
+	startTS, endTS := uint64(math.MaxUint64), uint64(0)
 	for traceKey, traceInfo := range events {
 		sample := profile.Sample().AppendEmpty()
 		sample.SetLocationsStartIndex(locationIndex)
 
-		slices.Sort(traceInfo.Timestamps)
-		startTS = pcommon.Timestamp(traceInfo.Timestamps[0])
-		endTS = pcommon.Timestamp(traceInfo.Timestamps[len(traceInfo.Timestamps)-1])
+		for _, ts := range traceInfo.Timestamps {
+			startTS = min(startTS, ts)
+			endTS = max(endTS, ts)
+		}
 		sample.TimestampsUnixNano().FromRaw(traceInfo.Timestamps)
 
 		switch origin {
@@ -283,8 +284,8 @@ func (p *Pdata) setProfile(
 
 	log.Debugf("Reporting OTLP profile with %d samples", profile.Sample().Len())
 
-	profile.SetDuration(endTS - startTS)
-	profile.SetStartTime(startTS)
+	profile.SetDuration(pcommon.Timestamp(endTS - startTS))
+	profile.SetStartTime(pcommon.Timestamp(startTS))
 
 	return nil
 }

reporter/internal/pdata/generate_test.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pprofile"
 
 	semconv "go.opentelemetry.io/otel/semconv/v1.34.0"
@@ -217,3 +218,38 @@ func TestFunctionTableOrder(t *testing.T) {
 		})
 	}
 }
+
+func TestProfileDuration(t *testing.T) {
+	for _, tt := range []struct {
+		name   string
+		events map[libpf.Origin]samples.KeyToEventMapping
+	}{
+		{
+			name: "profile duration",
+			events: map[libpf.Origin]samples.KeyToEventMapping{
+				support.TraceOriginSampling: map[samples.TraceAndMetaKey]*samples.TraceEvents{
+					{Pid: 1}: {
+						Timestamps: []uint64{2, 1, 3, 4, 7},
+					},
+					{Pid: 2}: {
+						Timestamps: []uint64{8},
+					},
+				},
+			},
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			d, err := New(100, 100, 100, nil)
+			require.NoError(t, err)
+
+			tree := make(samples.TraceEventsTree)
+			tree[""] = tt.events
+			res, err := d.Generate(tree, tt.name, "version")
+			require.NoError(t, err)
+
+			profile := res.ResourceProfiles().At(0).ScopeProfiles().At(0).Profiles().At(0)
+			require.Equal(t, pcommon.Timestamp(7), profile.Duration())
+			require.Equal(t, pcommon.Timestamp(1), profile.StartTime())
+		})
+	}
+}