CPU History, CPU Utilization

util/sys/sys_linux.go

@@ -4,10 +4,14 @@
 package sys
 
 import (
+	"bufio"
 	"bytes"
 	"fmt"
 	"io"
 	"os"
+	"strconv"
+	"strings"
+	"sync"
 )
 
 func getLinesNum(filename string) (int, error) {
@@ -79,3 +83,99 @@ func safeGetLinesNum(path string) (int, error) {
 	}
 	return getLinesNum(path)
 }
+
+// --- CPU Utilization (Linux native) ---
+
+var (
+	cpuMu       sync.Mutex
+	lastTotal   uint64
+	lastIdleAll uint64
+	hasLast     bool
+)
+
+// CPUPercentRaw returns instantaneous total CPU utilization by reading /proc/stat.
+// First call initializes and returns 0; subsequent calls return busy/total * 100.
+func CPUPercentRaw() (float64, error) {
+	f, err := os.Open("/proc/stat")
+	if err != nil {
+		return 0, err
+	}
+	defer f.Close()
+
+	rd := bufio.NewReader(f)
+	line, err := rd.ReadString('\n')
+	if err != nil && err != io.EOF {
+		return 0, err
+	}
+	// Expect line like: cpu  user nice system idle iowait irq softirq steal guest guest_nice
+	fields := strings.Fields(line)
+	if len(fields) < 5 || fields[0] != "cpu" {
+		return 0, fmt.Errorf("unexpected /proc/stat format")
+	}
+
+	var nums []uint64
+	for i := 1; i < len(fields); i++ {
+		v, err := strconv.ParseUint(fields[i], 10, 64)
+		if err != nil {
+			break
+		}
+		nums = append(nums, v)
+	}
+	if len(nums) < 4 { // need at least user,nice,system,idle
+		return 0, fmt.Errorf("insufficient cpu fields")
+	}
+
+	// Conform with standard Linux CPU accounting
+	var user, nice, system, idle, iowait, irq, softirq, steal uint64
+	user = nums[0]
+	if len(nums) > 1 {
+		nice = nums[1]
+	}
+	if len(nums) > 2 {
+		system = nums[2]
+	}
+	if len(nums) > 3 {
+		idle = nums[3]
+	}
+	if len(nums) > 4 {
+		iowait = nums[4]
+	}
+	if len(nums) > 5 {
+		irq = nums[5]
+	}
+	if len(nums) > 6 {
+		softirq = nums[6]
+	}
+	if len(nums) > 7 {
+		steal = nums[7]
+	}
+
+	idleAll := idle + iowait
+	nonIdle := user + nice + system + irq + softirq + steal
+	total := idleAll + nonIdle
+
+	cpuMu.Lock()
+	defer cpuMu.Unlock()
+
+	if !hasLast {
+		lastTotal = total
+		lastIdleAll = idleAll
+		hasLast = true
+		return 0, nil
+	}
+
+	totald := total - lastTotal
+	idled := idleAll - lastIdleAll
+	lastTotal = total
+	lastIdleAll = idleAll
+
+	if totald == 0 {
+		return 0, nil
+	}
+	busy := totald - idled
+	pct := float64(busy) / float64(totald) * 100.0
+	if pct > 100 {
+		pct = 100
+	}
+	return pct, nil
+}