Add support for reading AnonHugePages from /proc/meminfo

This commit adds support for reading the `AnonHugePages` field from `/proc/meminfo`.

The values in this field allow monitoring the [THP](https://www.kernel.org/doc/Documentation/vm/transhuge.txt) usage by systems that use this type of memory

mem/mem.go

@@ -50,6 +50,7 @@ type VirtualMemoryStat struct {
 	// https://www.centos.org/docs/5/html/5.1/Deployment_Guide/s2-proc-meminfo.html
 	// https://www.kernel.org/doc/Documentation/filesystems/proc.txt
 	// https://www.kernel.org/doc/Documentation/vm/overcommit-accounting
+	// https://www.kernel.org/doc/Documentation/vm/transhuge.txt
 	Buffers        uint64 `json:"buffers"`
 	Cached         uint64 `json:"cached"`
 	WriteBack      uint64 `json:"writeBack"`
@@ -78,6 +79,7 @@ type VirtualMemoryStat struct {
 	HugePagesRsvd  uint64 `json:"hugePagesRsvd"`
 	HugePagesSurp  uint64 `json:"hugePagesSurp"`
 	HugePageSize   uint64 `json:"hugePageSize"`
+	AnonHugePages  uint64 `json:"anonHugePages"`
 }
 
 type SwapMemoryStat struct {

mem/mem_linux.go

@@ -311,6 +311,12 @@ func fillFromMeminfoWithContext(ctx context.Context) (*VirtualMemoryStat, *Virtu
 				return ret, retEx, err
 			}
 			ret.HugePageSize = t * 1024
+		case "AnonHugePages":
+			t, err := strconv.ParseUint(value, 10, 64)
+			if err != nil {
+				return ret, retEx, err
+			}
+			ret.AnonHugePages = t * 1024
 		}
 	}
 

mem/mem_linux_test.go

@@ -108,6 +108,16 @@ var virtualMemoryTests = []struct {
 			HugePageSize:   0,
 		},
 	},
+	{
+		"anonhugepages", &VirtualMemoryStat{
+			Total:         260799420 * 1024,
+			Available:     127880216 * 1024,
+			Free:          119443248 * 1024,
+			AnonHugePages: 50409472 * 1024,
+			Used:          144748720128,
+			UsedPercent:   54.20110673559013,
+		},
+	},
 }
 
 func TestVirtualMemoryLinux(t *testing.T) {

mem/mem_test.go

@@ -89,7 +89,7 @@ func TestVirtualMemoryStat_String(t *testing.T) {
 		Free:        40,
 	}
 	t.Log(v)
-	e := `{"total":10,"available":20,"used":30,"usedPercent":30.1,"free":40,"active":0,"inactive":0,"wired":0,"laundry":0,"buffers":0,"cached":0,"writeBack":0,"dirty":0,"writeBackTmp":0,"shared":0,"slab":0,"sreclaimable":0,"sunreclaim":0,"pageTables":0,"swapCached":0,"commitLimit":0,"committedAS":0,"highTotal":0,"highFree":0,"lowTotal":0,"lowFree":0,"swapTotal":0,"swapFree":0,"mapped":0,"vmallocTotal":0,"vmallocUsed":0,"vmallocChunk":0,"hugePagesTotal":0,"hugePagesFree":0,"hugePagesRsvd":0,"hugePagesSurp":0,"hugePageSize":0}`
+	e := `{"total":10,"available":20,"used":30,"usedPercent":30.1,"free":40,"active":0,"inactive":0,"wired":0,"laundry":0,"buffers":0,"cached":0,"writeBack":0,"dirty":0,"writeBackTmp":0,"shared":0,"slab":0,"sreclaimable":0,"sunreclaim":0,"pageTables":0,"swapCached":0,"commitLimit":0,"committedAS":0,"highTotal":0,"highFree":0,"lowTotal":0,"lowFree":0,"swapTotal":0,"swapFree":0,"mapped":0,"vmallocTotal":0,"vmallocUsed":0,"vmallocChunk":0,"hugePagesTotal":0,"hugePagesFree":0,"hugePagesRsvd":0,"hugePagesSurp":0,"hugePageSize":0,"anonHugePages":0}`
 	if e != fmt.Sprintf("%v", v) {
 		t.Errorf("VirtualMemoryStat string is invalid: %v", v)
 	}

mem/testdata/linux/virtualmemory/anonhugepages/proc/meminfo

@@ -0,0 +1,4 @@
+MemTotal:       260799420 kB
+MemFree:        119443248 kB
+MemAvailable:   127880216 kB
+AnonHugePages:  50409472 kB