converted freebsd cpu metrics to seconds

collector/cpu_freebsd.go

@@ -28,9 +28,26 @@ import (
 #cgo LDFLAGS: -lkvm
 #include <fcntl.h>
 #include <kvm.h>
+#include <stdlib.h>
 #include <sys/param.h>
 #include <sys/pcpu.h>
 #include <sys/resource.h>
+#include <sys/sysctl.h>
+#include <sys/time.h>
+
+long _clockrate() {
+	struct clockinfo clockrate;
+	size_t size = sizeof(clockrate);
+	int res = sysctlbyname("kern.clockrate", &clockrate, &size, NULL, 0);
+	if (res == -1) {
+		return -1;
+	}
+	if (size != sizeof(clockrate)) {
+		return -2;
+	}
+	return clockrate.stathz > 0 ? clockrate.stathz : clockrate.hz;
+}
+
 */
 import "C"
 
@@ -70,16 +87,37 @@ func (c *statCollector) Update(ch chan<- prometheus.Metric) (err error) {
 	}
 	defer C.kvm_close(kd)
 
+	// The cp_time variable is an array of CPUSTATES long integers -- in
+	// the same format as the kern.cp_time sysctl.  According to the
+	// comments in sys/kern/kern_clock.c, the frequency of this timer will
+	// be stathz (or hz, if stathz is zero).
+	clockrate, err := getClockRate()
+	if err != nil {
+		return err
+	}
+
 	ncpus := C.kvm_getncpus(kd)
 	for i := 0; i < int(ncpus); i++ {
 		pcpu := C.kvm_getpcpu(kd, C.int(i))
 		cp_time := ((*C.struct_pcpu)(unsafe.Pointer(pcpu))).pc_cp_time
-		c.cpu.With(prometheus.Labels{"cpu": strconv.Itoa(i), "mode": "user"}).Set(float64(cp_time[C.CP_USER]))
-		c.cpu.With(prometheus.Labels{"cpu": strconv.Itoa(i), "mode": "nice"}).Set(float64(cp_time[C.CP_NICE]))
-		c.cpu.With(prometheus.Labels{"cpu": strconv.Itoa(i), "mode": "system"}).Set(float64(cp_time[C.CP_SYS]))
-		c.cpu.With(prometheus.Labels{"cpu": strconv.Itoa(i), "mode": "interrupt"}).Set(float64(cp_time[C.CP_INTR]))
-		c.cpu.With(prometheus.Labels{"cpu": strconv.Itoa(i), "mode": "idle"}).Set(float64(cp_time[C.CP_IDLE]))
+		c.cpu.With(prometheus.Labels{"cpu": strconv.Itoa(i), "mode": "user"}).Set(float64(cp_time[C.CP_USER])/clockrate)
+		c.cpu.With(prometheus.Labels{"cpu": strconv.Itoa(i), "mode": "nice"}).Set(float64(cp_time[C.CP_NICE])/clockrate)
+		c.cpu.With(prometheus.Labels{"cpu": strconv.Itoa(i), "mode": "system"}).Set(float64(cp_time[C.CP_SYS])/clockrate)
+		c.cpu.With(prometheus.Labels{"cpu": strconv.Itoa(i), "mode": "interrupt"}).Set(float64(cp_time[C.CP_INTR])/clockrate)
+		c.cpu.With(prometheus.Labels{"cpu": strconv.Itoa(i), "mode": "idle"}).Set(float64(cp_time[C.CP_IDLE])/clockrate)
 	}
 	c.cpu.Collect(ch)
 	return err
 }
+
+func getClockRate() (float64, error) {
+	clockrate := C._clockrate()
+	if clockrate == -1 {
+		return 0, errors.New("sysctl(kern.clockrate) failed")
+	} else if clockrate == -2 {
+		return 0, errors.New("sysctl(kern.clockrate) failed, wrong buffer size")
+	} else if clockrate <= 0 {
+		return 0, errors.New("sysctl(kern.clockrate) bad clocktime")
+	}
+	return float64(clockrate), nil
+}