fix(meminfo): account for optional unit field so values are accurate

Addresses: #565

Previously, this function was ignoring the optional unit field, leading
to incorrect results on systems that do report the field. This uses the
humanize lib used elsewhere within the Prometheus ecosystem to normalize
the value to bytes, including when a unit is provided.

Signed-off-by: TJ Hoplock <[email protected]>

go.mod

@@ -3,6 +3,7 @@ module github.com/prometheus/procfs
 go 1.19
 
 require (
+	github.com/dustin/go-humanize v1.0.1
 	github.com/google/go-cmp v0.5.9
 	golang.org/x/sync v0.3.0
 	golang.org/x/sys v0.11.0

go.sum

@@ -1,3 +1,5 @@
+github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
+github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+mFykh5fBlto=
 github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 golang.org/x/sync v0.3.0 h1:ftCYgMx6zT/asHUrPw8BLLscYtGznsLAnjq5RH9P66E=

meminfo.go

@@ -21,6 +21,8 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/dustin/go-humanize"
+
 	"github.com/prometheus/procfs/internal/util"
 )
 
@@ -162,15 +164,26 @@ func parseMemInfo(r io.Reader) (*Meminfo, error) {
 	var m Meminfo
 	s := bufio.NewScanner(r)
 	for s.Scan() {
-		// Each line has at least a name and value; we ignore the unit.
 		fields := strings.Fields(s.Text())
-		if len(fields) < 2 {
-			return nil, fmt.Errorf("%w: Malformed line %q", ErrFileParse, s.Text())
-		}
+		var v uint64
 
-		v, err := strconv.ParseUint(fields[1], 0, 64)
-		if err != nil {
-			return nil, err
+		switch len(fields) {
+		case 2:
+			// No unit present, parse the value as bytes directly.
+			val, err := strconv.ParseUint(fields[1], 0, 64)
+			if err != nil {
+				return nil, err
+			}
+			v = val
+		case 3:
+			// Unit present, convert and normalize to bytes.
+			val, err := humanize.ParseBytes(fmt.Sprintf("%s %s", fields[1], fields[2]))
+			if err != nil {
+				return nil, err
+			}
+			v = val
+		default:
+			return nil, fmt.Errorf("%w: Malformed line %q", ErrFileParse, s.Text())
 		}
 
 		switch fields[0] {

meminfo_test.go

@@ -20,48 +20,48 @@ import (
 
 func TestMeminfo(t *testing.T) {
 	expected := Meminfo{
-		MemTotal:          newuint64(15666184),
-		MemFree:           newuint64(440324),
-		Buffers:           newuint64(1020128),
-		Cached:            newuint64(12007640),
+		MemTotal:          newuint64(15666184000),
+		MemFree:           newuint64(440324000),
+		Buffers:           newuint64(1020128000),
+		Cached:            newuint64(12007640000),
 		SwapCached:        newuint64(0),
-		Active:            newuint64(6761276),
-		Inactive:          newuint64(6532708),
-		ActiveAnon:        newuint64(267256),
-		InactiveAnon:      newuint64(268),
-		ActiveFile:        newuint64(6494020),
-		InactiveFile:      newuint64(6532440),
+		Active:            newuint64(6761276000),
+		Inactive:          newuint64(6532708000),
+		ActiveAnon:        newuint64(267256000),
+		InactiveAnon:      newuint64(268000),
+		ActiveFile:        newuint64(6494020000),
+		InactiveFile:      newuint64(6532440000),
 		Unevictable:       newuint64(0),
 		Mlocked:           newuint64(0),
 		SwapTotal:         newuint64(0),
 		SwapFree:          newuint64(0),
-		Dirty:             newuint64(768),
+		Dirty:             newuint64(768000),
 		Writeback:         newuint64(0),
-		AnonPages:         newuint64(266216),
-		Mapped:            newuint64(44204),
-		Shmem:             newuint64(1308),
-		Slab:              newuint64(1807264),
-		SReclaimable:      newuint64(1738124),
-		SUnreclaim:        newuint64(69140),
-		KernelStack:       newuint64(1616),
-		PageTables:        newuint64(5288),
+		AnonPages:         newuint64(266216000),
+		Mapped:            newuint64(44204000),
+		Shmem:             newuint64(1308000),
+		Slab:              newuint64(1807264000),
+		SReclaimable:      newuint64(1738124000),
+		SUnreclaim:        newuint64(69140000),
+		KernelStack:       newuint64(1616000),
+		PageTables:        newuint64(5288000),
 		NFSUnstable:       newuint64(0),
 		Bounce:            newuint64(0),
 		WritebackTmp:      newuint64(0),
-		CommitLimit:       newuint64(7833092),
-		CommittedAS:       newuint64(530844),
-		VmallocTotal:      newuint64(34359738367),
-		VmallocUsed:       newuint64(36596),
-		VmallocChunk:      newuint64(34359637840),
+		CommitLimit:       newuint64(7833092000),
+		CommittedAS:       newuint64(530844000),
+		VmallocTotal:      newuint64(34359738367000),
+		VmallocUsed:       newuint64(36596000),
+		VmallocChunk:      newuint64(34359637840000),
 		HardwareCorrupted: newuint64(0),
-		AnonHugePages:     newuint64(12288),
+		AnonHugePages:     newuint64(12288000),
 		HugePagesTotal:    newuint64(0),
 		HugePagesFree:     newuint64(0),
 		HugePagesRsvd:     newuint64(0),
 		HugePagesSurp:     newuint64(0),
-		Hugepagesize:      newuint64(2048),
-		DirectMap4k:       newuint64(91136),
-		DirectMap2M:       newuint64(16039936),
+		Hugepagesize:      newuint64(2048000),
+		DirectMap4k:       newuint64(91136000),
+		DirectMap2M:       newuint64(16039936000),
 	}
 
 	have, err := getProcFixtures(t).Meminfo()