refactor(agent): avoid deprecated CPU time total helper (#2459)

agent/cpu.go

@@ -119,7 +119,8 @@ func calculateBusy(t1, t2 cpu.TimesStat) float64 {
 // On Linux, it excludes guest and guest_nice time from the total to match kernel behavior.
 // Returns total CPU time and busy CPU time (total minus idle and I/O wait time).
 func getAllBusy(t cpu.TimesStat) (float64, float64) {
-	tot := t.Total()
+	tot := t.User + t.System + t.Idle + t.Nice + t.Iowait + t.Irq +
+		t.Softirq + t.Steal + t.Guest + t.GuestNice
 	if runtime.GOOS == "linux" {
 		tot -= t.Guest     // Linux 2.6.24+
 		tot -= t.GuestNice // Linux 3.2.0+

agent/cpu_test.go

@@ -0,0 +1,28 @@
+//go:build testing
+
+package agent
+
+import (
+	"runtime"
+	"testing"
+
+	"github.com/shirou/gopsutil/v4/cpu"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetAllBusy(t *testing.T) {
+	times := cpu.TimesStat{
+		User: 1, System: 2, Idle: 3, Nice: 4, Iowait: 5,
+		Irq: 6, Softirq: 7, Steal: 8, Guest: 9, GuestNice: 10,
+	}
+	wantTotal, wantBusy := 55.0, 47.0
+	if runtime.GOOS == "linux" {
+		wantTotal, wantBusy = 36, 28
+	}
+	total, busy := getAllBusy(times)
+	assert.Equal(t, wantTotal, total)
+	assert.Equal(t, wantBusy, busy)
+	assert.InDelta(t, wantBusy/wantTotal*100, calculateBusy(cpu.TimesStat{}, times), 1e-10)
+	assert.Zero(t, calculateBusy(times, times))
+	assert.Zero(t, calculateBusy(times, cpu.TimesStat{}))
+}