Determine total physical memory from sysfs for linux as primary method

pkg/linuxpath/path_linux.go

@@ -13,36 +13,38 @@ import (
 )
 
 type Paths struct {
-	VarLog               string
-	ProcMeminfo          string
-	ProcCpuinfo          string
-	SysKernelMMHugepages string
-	EtcMtab              string
-	SysBlock             string
-	SysDevicesSystemNode string
-	SysBusPciDevices     string
-	SysClassDRM          string
-	SysClassDMI          string
-	SysClassNet          string
-	RunUdevData          string
+	VarLog                 string
+	ProcMeminfo            string
+	ProcCpuinfo            string
+	SysKernelMMHugepages   string
+	EtcMtab                string
+	SysBlock               string
+	SysDevicesSystemNode   string
+	SysDevicesSystemMemory string
+	SysBusPciDevices       string
+	SysClassDRM            string
+	SysClassDMI            string
+	SysClassNet            string
+	RunUdevData            string
 }
 
 // New returns a new Paths struct containing filepath fields relative to the
 // supplied Context
 func New(ctx *context.Context) *Paths {
 	return &Paths{
-		VarLog:               filepath.Join(ctx.Chroot, "var", "log"),
-		ProcMeminfo:          filepath.Join(ctx.Chroot, "proc", "meminfo"),
-		ProcCpuinfo:          filepath.Join(ctx.Chroot, "proc", "cpuinfo"),
-		SysKernelMMHugepages: filepath.Join(ctx.Chroot, "sys", "kernel", "mm", "hugepages"),
-		EtcMtab:              filepath.Join(ctx.Chroot, "etc", "mtab"),
-		SysBlock:             filepath.Join(ctx.Chroot, "sys", "block"),
-		SysDevicesSystemNode: filepath.Join(ctx.Chroot, "sys", "devices", "system", "node"),
-		SysBusPciDevices:     filepath.Join(ctx.Chroot, "sys", "bus", "pci", "devices"),
-		SysClassDRM:          filepath.Join(ctx.Chroot, "sys", "class", "drm"),
-		SysClassDMI:          filepath.Join(ctx.Chroot, "sys", "class", "dmi"),
-		SysClassNet:          filepath.Join(ctx.Chroot, "sys", "class", "net"),
-		RunUdevData:          filepath.Join(ctx.Chroot, "run", "udev", "data"),
+		VarLog:                 filepath.Join(ctx.Chroot, "var", "log"),
+		ProcMeminfo:            filepath.Join(ctx.Chroot, "proc", "meminfo"),
+		ProcCpuinfo:            filepath.Join(ctx.Chroot, "proc", "cpuinfo"),
+		SysKernelMMHugepages:   filepath.Join(ctx.Chroot, "sys", "kernel", "mm", "hugepages"),
+		EtcMtab:                filepath.Join(ctx.Chroot, "etc", "mtab"),
+		SysBlock:               filepath.Join(ctx.Chroot, "sys", "block"),
+		SysDevicesSystemNode:   filepath.Join(ctx.Chroot, "sys", "devices", "system", "node"),
+		SysDevicesSystemMemory: filepath.Join(ctx.Chroot, "sys", "devices", "system", "memory"),
+		SysBusPciDevices:       filepath.Join(ctx.Chroot, "sys", "bus", "pci", "devices"),
+		SysClassDRM:            filepath.Join(ctx.Chroot, "sys", "class", "drm"),
+		SysClassDMI:            filepath.Join(ctx.Chroot, "sys", "class", "dmi"),
+		SysClassNet:            filepath.Join(ctx.Chroot, "sys", "class", "net"),
+		RunUdevData:            filepath.Join(ctx.Chroot, "run", "udev", "data"),
 	}
 }
 

pkg/memory/memory_linux.go

@@ -26,9 +26,10 @@ const (
 	_WARN_CANNOT_DETERMINE_PHYSICAL_MEMORY = `
 Could not determine total physical bytes of memory. This may
 be due to the host being a virtual machine or container with no
-/var/log/syslog file, or the current user may not have necessary
-privileges to read the syslog. We are falling back to setting the
-total physical amount of memory to the total usable amount of memory
+/var/log/syslog file or /sys/devices/system/memory directory, or
+the current user may not have necessary privileges to read the syslog.
+We are falling back to setting the total physical amount of memory to
+the total usable amount of memory
 `
 )
 
@@ -55,7 +56,55 @@ func (i *Info) load() error {
 	return nil
 }
 
-func memTotalPhysicalBytes(paths *linuxpath.Paths) int64 {
+func memTotalPhysicalBytes(paths *linuxpath.Paths) (total int64) {
+	defer func() {
+		// fallback to the syslog file approach in case of error
+		if total < 0 {
+			total = memTotalPhysicalBytesFromSyslog(paths)
+		}
+	}()
+
+	// detect physical memory from /sys/devices/system/memory
+	dir := paths.SysDevicesSystemMemory
+
+	// get the memory block size in byte in hexadecimal notation
+	blockSize := filepath.Join(dir, "block_size_bytes")
+
+	d, err := ioutil.ReadFile(blockSize)
+	if err != nil {
+		return -1
+	}
+	blockSizeBytes, err := strconv.ParseUint(strings.TrimSpace(string(d)), 16, 64)
+	if err != nil {
+		return -1
+	}
+
+	// iterate over memory's block /sys/devices/system/memory/memory*,
+	// if the memory block state is 'online' we increment the total
+	// with the memory block size to determine the amount of physical
+	// memory available on this system
+	sysMemory, err := filepath.Glob(filepath.Join(dir, "memory*"))
+	if err != nil {
+		return -1
+	} else if sysMemory == nil {
+		return -1
+	}
+
+	for _, path := range sysMemory {
+		s, err := ioutil.ReadFile(filepath.Join(path, "state"))
+		if err != nil {
+			return -1
+		}
+		if strings.TrimSpace(string(s)) != "online" {
+			continue
+		}
+		total += int64(blockSizeBytes)
+	}
+
+	return total
+}
+
+func memTotalPhysicalBytesFromSyslog(paths *linuxpath.Paths) int64 {
 	// In Linux, the total physical memory can be determined by looking at the
 	// output of dmidecode, however dmidecode requires root privileges to run,
 	// so instead we examine the system logs for startup information containing