code cleanup

app/cpu/drivers/rapl.go

@@ -2,7 +2,6 @@ package drivers
 
 import (
 	"fmt"
-	"math"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -10,6 +9,8 @@ import (
 	"time"
 )
 
+const milliJoulePerJoule = float64(1000000)
+
 type EnergyState struct {
 	lastEnergy uint64
 	lastTime   time.Time
@@ -72,19 +73,9 @@ func getRaplLabel(inputPath string) string {
 }
 
 func (r *RaplDriver) calculateEnergyDelta(inputs []string, out *[]PowerSensor) {
-	now := time.Now()
-
-	if r.energyState == nil {
-		r.energyState = make(map[string]EnergyState)
-	}
-
-	for _, rawPath := range inputs {
-		key, err := filepath.EvalSymlinks(rawPath)
-		if err != nil {
-			key = filepath.Clean(rawPath)
-		}
-
-		valBytes, err := os.ReadFile(key)
+	for _, path := range inputs {
+		now := time.Now()
+		valBytes, err := os.ReadFile(path)
 		if err != nil {
 			continue
 		}
@@ -94,49 +85,38 @@ func (r *RaplDriver) calculateEnergyDelta(inputs []string, out *[]PowerSensor) {
 			continue
 		}
 
-		prevState, exists := r.energyState[key]
+		sensorLabel := getRaplLabel(path)
+
+		prevState, exists := r.energyState[path]
 
 		if !exists {
-			r.energyState[key] = EnergyState{
+
+			r.energyState[path] = EnergyState{
 				lastEnergy: microJoules,
 				lastTime:   now,
 			}
 			*out = append(*out, PowerSensor{
-				Name:  getRaplLabel(key),
+				Name:  sensorLabel,
 				Watts: 0.0,
 			})
 			continue
 		}
 
 		timeDiff := now.Sub(prevState.lastTime).Seconds()
-		if timeDiff < 0.05 {
-			continue
-		}
 
-		maxRange := uint64(math.MaxUint64)
-		rangeBytes, err := os.ReadFile(filepath.Join(filepath.Dir(key), "max_energy_range_uj"))
-		if err == nil {
-			if parsedMax, err := strconv.ParseUint(strings.TrimSpace(string(rangeBytes)), 10, 64); err == nil && parsedMax > 0 {
-				maxRange = parsedMax
-			}
-		}
+		// technically the energy counter could overflow, at ~18 TerraJoules
+		// the value will be off for that one measurement, then become correct again
+		energyDiff := float64(microJoules - prevState.lastEnergy)
 
-		var energyDiff uint64
-		if microJoules >= prevState.lastEnergy {
-			energyDiff = microJoules - prevState.lastEnergy
-		} else {
-			energyDiff = (maxRange - prevState.lastEnergy) + microJoules
-		}
+		watts := (energyDiff / milliJoulePerJoule) / timeDiff
 
-		watts := (float64(energyDiff) / 1_000_000.0) / timeDiff
-
-		r.energyState[key] = EnergyState{
+		r.energyState[path] = EnergyState{
 			lastEnergy: microJoules,
 			lastTime:   now,
 		}
 
 		*out = append(*out, PowerSensor{
-			Name:  getRaplLabel(key),
+			Name:  sensorLabel,
 			Watts: watts,
 		})
 	}