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.

To try and maintain existing behavior, the fixed/unit-scaled values are
stored as new struct fields.

Signed-off-by: TJ Hoplock <t.hoplock@gmail.com>

meminfo.go

@@ -140,6 +140,58 @@ type Meminfo struct {
 	DirectMap4k       *uint64
 	DirectMap2M       *uint64
 	DirectMap1G       *uint64
+
+	// The struct fields below are the byte-normalized counterparts to the
+	// existing struct fields. Values are normalized using the optional
+	// unit field in the meminfo line.
+	MemTotalBytes          *uint64
+	MemFreeBytes           *uint64
+	MemAvailableBytes      *uint64
+	BuffersBytes           *uint64
+	CachedBytes            *uint64
+	SwapCachedBytes        *uint64
+	ActiveBytes            *uint64
+	InactiveBytes          *uint64
+	ActiveAnonBytes        *uint64
+	InactiveAnonBytes      *uint64
+	ActiveFileBytes        *uint64
+	InactiveFileBytes      *uint64
+	UnevictableBytes       *uint64
+	MlockedBytes           *uint64
+	SwapTotalBytes         *uint64
+	SwapFreeBytes          *uint64
+	DirtyBytes             *uint64
+	WritebackBytes         *uint64
+	AnonPagesBytes         *uint64
+	MappedBytes            *uint64
+	ShmemBytes             *uint64
+	SlabBytes              *uint64
+	SReclaimableBytes      *uint64
+	SUnreclaimBytes        *uint64
+	KernelStackBytes       *uint64
+	PageTablesBytes        *uint64
+	NFSUnstableBytes       *uint64
+	BounceBytes            *uint64
+	WritebackTmpBytes      *uint64
+	CommitLimitBytes       *uint64
+	CommittedASBytes       *uint64
+	VmallocTotalBytes      *uint64
+	VmallocUsedBytes       *uint64
+	VmallocChunkBytes      *uint64
+	HardwareCorruptedBytes *uint64
+	AnonHugePagesBytes     *uint64
+	ShmemHugePagesBytes    *uint64
+	ShmemPmdMappedBytes    *uint64
+	CmaTotalBytes          *uint64
+	CmaFreeBytes           *uint64
+	HugePagesTotalBytes    *uint64
+	HugePagesFreeBytes     *uint64
+	HugePagesRsvdBytes     *uint64
+	HugePagesSurpBytes     *uint64
+	HugepagesizeBytes      *uint64
+	DirectMap4kBytes       *uint64
+	DirectMap2MBytes       *uint64
+	DirectMap1GBytes       *uint64
 }
 
 // Meminfo returns an information about current kernel/system memory statistics.
@@ -162,114 +214,179 @@ 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 val, valBytes uint64
 
 		v, err := strconv.ParseUint(fields[1], 0, 64)
 		if err != nil {
 			return nil, err
 		}
 
+		val = v
+
+		switch len(fields) {
+		case 2:
+			// No unit present, use the parsed the value as bytes directly.
+			valBytes = val
+		case 3:
+			// Unit present in optional 3rd field, convert it to
+			// bytes. The only unit supported within the Linux
+			// kernel is `kB`.
+			if fields[2] != "kB" {
+				return nil, fmt.Errorf("%w: Unsupported unit in optional 3rd field %q", ErrFileParse, fields[2])
+			}
+
+			valBytes = 1024 * val
+
+		default:
+			return nil, fmt.Errorf("%w: Malformed line %q", ErrFileParse, s.Text())
+		}
+
 		switch fields[0] {
 		case "MemTotal:":
-			m.MemTotal = &v
+			m.MemTotal = &val
+			m.MemTotalBytes = &valBytes
 		case "MemFree:":
-			m.MemFree = &v
+			m.MemFree = &val
+			m.MemFreeBytes = &valBytes
 		case "MemAvailable:":
-			m.MemAvailable = &v
+			m.MemAvailable = &val
+			m.MemAvailableBytes = &valBytes
 		case "Buffers:":
-			m.Buffers = &v
+			m.Buffers = &val
+			m.BuffersBytes = &valBytes
 		case "Cached:":
-			m.Cached = &v
+			m.Cached = &val
+			m.CachedBytes = &valBytes
 		case "SwapCached:":
-			m.SwapCached = &v
+			m.SwapCached = &val
+			m.SwapCachedBytes = &valBytes
 		case "Active:":
-			m.Active = &v
+			m.Active = &val
+			m.ActiveBytes = &valBytes
 		case "Inactive:":
-			m.Inactive = &v
+			m.Inactive = &val
+			m.InactiveBytes = &valBytes
 		case "Active(anon):":
-			m.ActiveAnon = &v
+			m.ActiveAnon = &val
+			m.ActiveAnonBytes = &valBytes
 		case "Inactive(anon):":
-			m.InactiveAnon = &v
+			m.InactiveAnon = &val
+			m.InactiveAnonBytes = &valBytes
 		case "Active(file):":
-			m.ActiveFile = &v
+			m.ActiveFile = &val
+			m.ActiveFileBytes = &valBytes
 		case "Inactive(file):":
-			m.InactiveFile = &v
+			m.InactiveFile = &val
+			m.InactiveFileBytes = &valBytes
 		case "Unevictable:":
-			m.Unevictable = &v
+			m.Unevictable = &val
+			m.UnevictableBytes = &valBytes
 		case "Mlocked:":
-			m.Mlocked = &v
+			m.Mlocked = &val
+			m.MlockedBytes = &valBytes
 		case "SwapTotal:":
-			m.SwapTotal = &v
+			m.SwapTotal = &val
+			m.SwapTotalBytes = &valBytes
 		case "SwapFree:":
-			m.SwapFree = &v
+			m.SwapFree = &val
+			m.SwapFreeBytes = &valBytes
 		case "Dirty:":
-			m.Dirty = &v
+			m.Dirty = &val
+			m.DirtyBytes = &valBytes
 		case "Writeback:":
-			m.Writeback = &v
+			m.Writeback = &val
+			m.WritebackBytes = &valBytes
 		case "AnonPages:":
-			m.AnonPages = &v
+			m.AnonPages = &val
+			m.AnonPagesBytes = &valBytes
 		case "Mapped:":
-			m.Mapped = &v
+			m.Mapped = &val
+			m.MappedBytes = &valBytes
 		case "Shmem:":
-			m.Shmem = &v
+			m.Shmem = &val
+			m.ShmemBytes = &valBytes
 		case "Slab:":
-			m.Slab = &v
+			m.Slab = &val
+			m.SlabBytes = &valBytes
 		case "SReclaimable:":
-			m.SReclaimable = &v
+			m.SReclaimable = &val
+			m.SReclaimableBytes = &valBytes
 		case "SUnreclaim:":
-			m.SUnreclaim = &v
+			m.SUnreclaim = &val
+			m.SUnreclaimBytes = &valBytes
 		case "KernelStack:":
-			m.KernelStack = &v
+			m.KernelStack = &val
+			m.KernelStackBytes = &valBytes
 		case "PageTables:":
-			m.PageTables = &v
+			m.PageTables = &val
+			m.PageTablesBytes = &valBytes
 		case "NFS_Unstable:":
-			m.NFSUnstable = &v
+			m.NFSUnstable = &val
+			m.NFSUnstableBytes = &valBytes
 		case "Bounce:":
-			m.Bounce = &v
+			m.Bounce = &val
+			m.BounceBytes = &valBytes
 		case "WritebackTmp:":
-			m.WritebackTmp = &v
+			m.WritebackTmp = &val
+			m.WritebackTmpBytes = &valBytes
 		case "CommitLimit:":
-			m.CommitLimit = &v
+			m.CommitLimit = &val
+			m.CommitLimitBytes = &valBytes
 		case "Committed_AS:":
-			m.CommittedAS = &v
+			m.CommittedAS = &val
+			m.CommittedASBytes = &valBytes
 		case "VmallocTotal:":
-			m.VmallocTotal = &v
+			m.VmallocTotal = &val
+			m.VmallocTotalBytes = &valBytes
 		case "VmallocUsed:":
-			m.VmallocUsed = &v
+			m.VmallocUsed = &val
+			m.VmallocUsedBytes = &valBytes
 		case "VmallocChunk:":
-			m.VmallocChunk = &v
+			m.VmallocChunk = &val
+			m.VmallocChunkBytes = &valBytes
 		case "HardwareCorrupted:":
-			m.HardwareCorrupted = &v
+			m.HardwareCorrupted = &val
+			m.HardwareCorruptedBytes = &valBytes
 		case "AnonHugePages:":
-			m.AnonHugePages = &v
+			m.AnonHugePages = &val
+			m.AnonHugePagesBytes = &valBytes
 		case "ShmemHugePages:":
-			m.ShmemHugePages = &v
+			m.ShmemHugePages = &val
+			m.ShmemHugePagesBytes = &valBytes
 		case "ShmemPmdMapped:":
-			m.ShmemPmdMapped = &v
+			m.ShmemPmdMapped = &val
+			m.ShmemPmdMappedBytes = &valBytes
 		case "CmaTotal:":
-			m.CmaTotal = &v
+			m.CmaTotal = &val
+			m.CmaTotalBytes = &valBytes
 		case "CmaFree:":
-			m.CmaFree = &v
+			m.CmaFree = &val
+			m.CmaFreeBytes = &valBytes
 		case "HugePages_Total:":
-			m.HugePagesTotal = &v
+			m.HugePagesTotal = &val
+			m.HugePagesTotalBytes = &valBytes
 		case "HugePages_Free:":
-			m.HugePagesFree = &v
+			m.HugePagesFree = &val
+			m.HugePagesFreeBytes = &valBytes
 		case "HugePages_Rsvd:":
-			m.HugePagesRsvd = &v
+			m.HugePagesRsvd = &val
+			m.HugePagesRsvdBytes = &valBytes
 		case "HugePages_Surp:":
-			m.HugePagesSurp = &v
+			m.HugePagesSurp = &val
+			m.HugePagesSurpBytes = &valBytes
 		case "Hugepagesize:":
-			m.Hugepagesize = &v
+			m.Hugepagesize = &val
+			m.HugepagesizeBytes = &valBytes
 		case "DirectMap4k:":
-			m.DirectMap4k = &v
+			m.DirectMap4k = &val
+			m.DirectMap4kBytes = &valBytes
 		case "DirectMap2M:":
-			m.DirectMap2M = &v
+			m.DirectMap2M = &val
+			m.DirectMap2MBytes = &valBytes
 		case "DirectMap1G:":
-			m.DirectMap1G = &v
+			m.DirectMap1G = &val
+			m.DirectMap1GBytes = &valBytes
 		}
 	}
 

meminfo_test.go

@@ -62,6 +62,49 @@ func TestMeminfo(t *testing.T) {
 		Hugepagesize:      newuint64(2048),
 		DirectMap4k:       newuint64(91136),
 		DirectMap2M:       newuint64(16039936),
+
+		MemTotalBytes:          newuint64(16042172416),
+		MemFreeBytes:           newuint64(450891776),
+		BuffersBytes:           newuint64(1044611072),
+		CachedBytes:            newuint64(12295823360),
+		SwapCachedBytes:        newuint64(0),
+		ActiveBytes:            newuint64(6923546624),
+		InactiveBytes:          newuint64(6689492992),
+		ActiveAnonBytes:        newuint64(273670144),
+		InactiveAnonBytes:      newuint64(274432),
+		ActiveFileBytes:        newuint64(6649876480),
+		InactiveFileBytes:      newuint64(6689218560),
+		UnevictableBytes:       newuint64(0),
+		MlockedBytes:           newuint64(0),
+		SwapTotalBytes:         newuint64(0),
+		SwapFreeBytes:          newuint64(0),
+		DirtyBytes:             newuint64(786432),
+		WritebackBytes:         newuint64(0),
+		AnonPagesBytes:         newuint64(272605184),
+		MappedBytes:            newuint64(45264896),
+		ShmemBytes:             newuint64(1339392),
+		SlabBytes:              newuint64(1850638336),
+		SReclaimableBytes:      newuint64(1779838976),
+		SUnreclaimBytes:        newuint64(70799360),
+		KernelStackBytes:       newuint64(1654784),
+		PageTablesBytes:        newuint64(5414912),
+		NFSUnstableBytes:       newuint64(0),
+		BounceBytes:            newuint64(0),
+		WritebackTmpBytes:      newuint64(0),
+		CommitLimitBytes:       newuint64(8021086208),
+		CommittedASBytes:       newuint64(543584256),
+		VmallocTotalBytes:      newuint64(35184372087808),
+		VmallocUsedBytes:       newuint64(37474304),
+		VmallocChunkBytes:      newuint64(35184269148160),
+		HardwareCorruptedBytes: newuint64(0),
+		AnonHugePagesBytes:     newuint64(12582912),
+		HugePagesTotalBytes:    newuint64(0),
+		HugePagesFreeBytes:     newuint64(0),
+		HugePagesRsvdBytes:     newuint64(0),
+		HugePagesSurpBytes:     newuint64(0),
+		HugepagesizeBytes:      newuint64(2097152),
+		DirectMap4kBytes:       newuint64(93323264),
+		DirectMap2MBytes:       newuint64(16424894464),
 	}
 
 	have, err := getProcFixtures(t).Meminfo()