Fix seconds reported by schedstat

As explained further in the code comments, the previous implementation was based on incorrect documentation and reported values 10000000 times too large for the values in seconds. Furthermore the RunningSeconds() and WaitingSeconds() methods are removed, as it's not this library's job to interpret these values. Signed-off-by: Phil Frost <[email protected]>
prometheus · Jul 31, 2019 · 5da962f · 5da962f
1 parent 5b594f4
commit 5da962f
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Showing 2 changed files with 31 additions and 51 deletions.
diff --git a/schedstat.go b/schedstat.go
@@ -31,6 +31,12 @@ var (
 // See
 // https://www.kernel.org/doc/Documentation/scheduler/sched-stats.txt
 // for a detailed description of what these numbers mean.
+//
+// Note the current kernel documentation claims some of the time units are in
+// jiffies when they are actually in nanoseconds since 2.6.23 with the
+// introduction of CFS. A fix to the documentation is pending. See
+// https://lore.kernel.org/patchwork/project/lkml/list/?series=403473
+
 type Schedstat struct {
 	CPUs []*SchedstatCPU
 }
@@ -39,16 +45,16 @@ type Schedstat struct {
 type SchedstatCPU struct {
 	CPUNum string
 
-	RunningJiffies uint64
-	WaitingJiffies uint64
-	RunTimeslices  uint64
+	RunningNanoseconds uint64
+	WaitingNanoseconds uint64
+	RunTimeslices      uint64
 }
 
 // ProcSchedstat contains the values from /proc/<pid>/schedstat
 type ProcSchedstat struct {
-	RunningJiffies uint64
-	WaitingJiffies uint64
-	RunTimeslices  uint64
+	RunningNanoseconds uint64
+	WaitingNanoseconds uint64
+	RunTimeslices      uint64
 }
 
 func (fs FS) Schedstat() (*Schedstat, error) {
@@ -67,12 +73,12 @@ func (fs FS) Schedstat() (*Schedstat, error) {
 			cpu := &SchedstatCPU{}
 			cpu.CPUNum = match[1]
 
-			cpu.RunningJiffies, err = strconv.ParseUint(match[8], 10, 64)
+			cpu.RunningNanoseconds, err = strconv.ParseUint(match[8], 10, 64)
 			if err != nil {
 				continue
 			}
 
-			cpu.WaitingJiffies, err = strconv.ParseUint(match[9], 10, 64)
+			cpu.WaitingNanoseconds, err = strconv.ParseUint(match[9], 10, 64)
 			if err != nil {
 				continue
 			}
@@ -93,12 +99,12 @@ func parseProcSchedstat(contents string) (stats ProcSchedstat, err error) {
 	match := procLineRE.FindStringSubmatch(contents)
 
 	if match != nil {
-		stats.RunningJiffies, err = strconv.ParseUint(match[1], 10, 64)
+		stats.RunningNanoseconds, err = strconv.ParseUint(match[1], 10, 64)
 		if err != nil {
 			return
 		}
 
-		stats.WaitingJiffies, err = strconv.ParseUint(match[2], 10, 64)
+		stats.WaitingNanoseconds, err = strconv.ParseUint(match[2], 10, 64)
 		if err != nil {
 			return
 		}
@@ -110,19 +116,3 @@ func parseProcSchedstat(contents string) (stats ProcSchedstat, err error) {
 	err = errors.New("could not parse schedstat")
 	return
 }
-
-func (stat *SchedstatCPU) RunningSeconds() float64 {
-	return float64(stat.RunningJiffies) / userHZ
-}
-
-func (stat *SchedstatCPU) WaitingSeconds() float64 {
-	return float64(stat.WaitingJiffies) / userHZ
-}
-
-func (stat *ProcSchedstat) RunningSeconds() float64 {
-	return float64(stat.RunningJiffies) / userHZ
-}
-
-func (stat *ProcSchedstat) WaitingSeconds() float64 {
-	return float64(stat.WaitingJiffies) / userHZ
-}
diff --git a/schedstat_test.go b/schedstat_test.go
@@ -13,7 +13,9 @@
 
 package procfs
 
-import "testing"
+import (
+	"testing"
+)
 
 func TestSchedstat(t *testing.T) {
 	stats, err := getProcFixtures(t).Schedstat()
@@ -36,18 +38,12 @@ func TestSchedstat(t *testing.T) {
 		t.Error("could not find cpu0")
 	}
 
-	if want, have := uint64(2045936778163039), cpu.RunningJiffies; want != have {
-		t.Errorf("want RunningJiffies %v, have %v", want, have)
-	}
-	if want, have := float64(2045936778163039)/userHZ, cpu.RunningSeconds(); want != have {
-		t.Errorf("want RunningSeconds() %v, have %v", want, have)
+	if want, have := uint64(2045936778163039), cpu.RunningNanoseconds; want != have {
+		t.Errorf("want RunningNanoseconds %v, have %v", want, have)
 	}
 
-	if want, have := uint64(343796328169361), cpu.WaitingJiffies; want != have {
-		t.Errorf("want WaitingJiffies %v, have %v", want, have)
-	}
-	if want, have := float64(343796328169361)/userHZ, cpu.WaitingSeconds(); want != have {
-		t.Errorf("want WaitingSeconds() %v, have %v", want, have)
+	if want, have := uint64(343796328169361), cpu.WaitingNanoseconds; want != have {
+		t.Errorf("want WaitingNanoseconds %v, have %v", want, have)
 	}
 
 	if want, have := uint64(4767485306), cpu.RunTimeslices; want != have {
@@ -66,18 +62,12 @@ func TestProcSchedstat(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if want, have := uint64(411605849), schedstat.RunningJiffies; want != have {
-		t.Errorf("want RunningJiffies %v, have %v", want, have)
-	}
-	if want, have := float64(411605849)/userHZ, schedstat.RunningSeconds(); want != have {
-		t.Errorf("want RunningSeconds() %v, have %v", want, have)
+	if want, have := uint64(411605849), schedstat.RunningNanoseconds; want != have {
+		t.Errorf("want RunningNanoseconds %v, have %v", want, have)
 	}
 
-	if want, have := uint64(93680043), schedstat.WaitingJiffies; want != have {
-		t.Errorf("want WaitingJiffies %v, have %v", want, have)
-	}
-	if want, have := float64(93680043)/userHZ, schedstat.WaitingSeconds(); want != have {
-		t.Errorf("want WaitingSeconds() %v, have %v", want, have)
+	if want, have := uint64(93680043), schedstat.WaitingNanoseconds; want != have {
+		t.Errorf("want WaitingNanoseconds %v, have %v", want, have)
 	}
 
 	if want, have := uint64(79), schedstat.RunTimeslices; want != have {
@@ -113,11 +103,11 @@ func TestProcSchedstatMultipleLines(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if want, have := uint64(123), schedstat.RunningJiffies; want != have {
-		t.Errorf("want RunningJiffies %v, have %v", want, have)
+	if want, have := uint64(123), schedstat.RunningNanoseconds; want != have {
+		t.Errorf("want RunningNanoseconds %v, have %v", want, have)
 	}
-	if want, have := uint64(456), schedstat.WaitingJiffies; want != have {
-		t.Errorf("want WaitingJiffies %v, have %v", want, have)
+	if want, have := uint64(456), schedstat.WaitingNanoseconds; want != have {
+		t.Errorf("want WaitingNanoseconds %v, have %v", want, have)
 	}
 	if want, have := uint64(789), schedstat.RunTimeslices; want != have {
 		t.Errorf("want RunTimeslices %v, have %v", want, have)