Moved system package inputs out to top level (#4406)

plugins/inputs/mem/memory.go

@@ -0,0 +1,51 @@
+package mem
+
+import (
+	"fmt"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/inputs"
+	"github.com/influxdata/telegraf/plugins/inputs/system"
+)
+
+type MemStats struct {
+	ps system.PS
+}
+
+func (_ *MemStats) Description() string {
+	return "Read metrics about memory usage"
+}
+
+func (_ *MemStats) SampleConfig() string { return "" }
+
+func (s *MemStats) Gather(acc telegraf.Accumulator) error {
+	vm, err := s.ps.VMStat()
+	if err != nil {
+		return fmt.Errorf("error getting virtual memory info: %s", err)
+	}
+
+	fields := map[string]interface{}{
+		"total":             vm.Total,
+		"available":         vm.Available,
+		"used":              vm.Used,
+		"free":              vm.Free,
+		"cached":            vm.Cached,
+		"buffered":          vm.Buffers,
+		"active":            vm.Active,
+		"inactive":          vm.Inactive,
+		"wired":             vm.Wired,
+		"slab":              vm.Slab,
+		"used_percent":      100 * float64(vm.Used) / float64(vm.Total),
+		"available_percent": 100 * float64(vm.Available) / float64(vm.Total),
+	}
+	acc.AddGauge("mem", fields, nil)
+
+	return nil
+}
+
+func init() {
+	ps := system.NewSystemPS()
+	inputs.Add("mem", func() telegraf.Input {
+		return &MemStats{ps: ps}
+	})
+}