cpu.Percent (Windows): Use the same implementation as on Unix

WMI is way too slow.

cpu/cpu.go

@@ -2,10 +2,12 @@ package cpu
 
 import (
 	"encoding/json"
+	"fmt"
 	"runtime"
 	"strconv"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/shirou/gopsutil/internal/common"
 )
@@ -91,3 +93,84 @@ func (c InfoStat) String() string {
 	s, _ := json.Marshal(c)
 	return string(s)
 }
+
+func getAllBusy(t TimesStat) (float64, float64) {
+	busy := t.User + t.System + t.Nice + t.Iowait + t.Irq +
+		t.Softirq + t.Steal + t.Guest + t.GuestNice + t.Stolen
+	return busy + t.Idle, busy
+}
+
+func calculateBusy(t1, t2 TimesStat) float64 {
+	t1All, t1Busy := getAllBusy(t1)
+	t2All, t2Busy := getAllBusy(t2)
+
+	if t2Busy <= t1Busy {
+		return 0
+	}
+	if t2All <= t1All {
+		return 1
+	}
+	return (t2Busy - t1Busy) / (t2All - t1All) * 100
+}
+
+func calculateAllBusy(t1, t2 []TimesStat) ([]float64, error) {
+	// Make sure the CPU measurements have the same length.
+	if len(t1) != len(t2) {
+		return nil, fmt.Errorf(
+			"received two CPU counts: %d != %d",
+			len(t1), len(t2),
+		)
+	}
+
+	ret := make([]float64, len(t1))
+	for i, t := range t2 {
+		ret[i] = calculateBusy(t1[i], t)
+	}
+	return ret, nil
+}
+
+//Percent calculates the percentage of cpu used either per CPU or combined.
+//If an interval of 0 is given it will compare the current cpu times against the last call.
+func Percent(interval time.Duration, percpu bool) ([]float64, error) {
+	if interval <= 0 {
+		return percentUsedFromLastCall(percpu)
+	}
+
+	// Get CPU usage at the start of the interval.
+	cpuTimes1, err := Times(percpu)
+	if err != nil {
+		return nil, err
+	}
+
+	time.Sleep(interval)
+
+	// And at the end of the interval.
+	cpuTimes2, err := Times(percpu)
+	if err != nil {
+		return nil, err
+	}
+
+	return calculateAllBusy(cpuTimes1, cpuTimes2)
+}
+
+func percentUsedFromLastCall(percpu bool) ([]float64, error) {
+	cpuTimes, err := Times(percpu)
+	if err != nil {
+		return nil, err
+	}
+	lastCPUPercent.Lock()
+	defer lastCPUPercent.Unlock()
+	var lastTimes []TimesStat
+	if percpu {
+		lastTimes = lastCPUPercent.lastPerCPUTimes
+		lastCPUPercent.lastPerCPUTimes = cpuTimes
+	} else {
+		lastTimes = lastCPUPercent.lastCPUTimes
+		lastCPUPercent.lastCPUTimes = cpuTimes
+	}
+
+	if lastTimes == nil {
+		return nil, fmt.Errorf("Error getting times for cpu percent. LastTimes was nil")
+	}
+	return calculateAllBusy(lastTimes, cpuTimes)
+}

cpu/cpu_windows.go

@@ -5,7 +5,6 @@ package cpu
 import (
 	"fmt"
 	"syscall"
-	"time"
 	"unsafe"
 
 	"github.com/StackExchange/wmi"
@@ -85,21 +84,3 @@ func Info() ([]InfoStat, error) {
 
 	return ret, nil
 }
-
-func Percent(interval time.Duration, percpu bool) ([]float64, error) {
-	var ret []float64
-	var dst []Win32_Processor
-	q := wmi.CreateQuery(&dst, "")
-	err := wmi.Query(q, &dst)
-	if err != nil {
-		return ret, err
-	}
-	for _, l := range dst {
-		// use range but windows can only get one percent.
-		if l.LoadPercentage == nil {
-			continue
-		}
-		ret = append(ret, float64(*l.LoadPercentage))
-	}
-	return ret, nil
-}