diff --git a/disk/disk_unix.go b/disk/disk_unix.go
index bc53d40..af4901d 100644
--- a/disk/disk_unix.go
+++ b/disk/disk_unix.go
@@ -16,14 +16,14 @@ func DiskUsage(path string) (*DiskUsageStat, error) {
 	ret := &DiskUsageStat{
 		Path:        path,
 		Total:       (uint64(stat.Blocks) * uint64(bsize)),
-		Free:        (uint64(stat.Bfree) * uint64(bsize)),
+		Free:        (uint64(stat.Bavail) * uint64(bsize)),
 		InodesTotal: (uint64(stat.Files)),
 		InodesFree:  (uint64(stat.Ffree)),
 	}
 
 	ret.InodesUsed = (ret.InodesTotal - ret.InodesFree)
 	ret.InodesUsedPercent = (float64(ret.InodesUsed) / float64(ret.InodesTotal)) * 100.0
-	ret.Used = (ret.Total - ret.Free)
+	ret.Used = (uint64(stat.Blocks) - uint64(stat.Bfree)) * uint64(bsize)
 	ret.UsedPercent = (float64(ret.Used) / float64(ret.Total)) * 100.0
 
 	return ret, nil
diff --git a/mem/mem_darwin.go b/mem/mem_darwin.go
index 6f901d2..bd6d2e0 100644
--- a/mem/mem_darwin.go
+++ b/mem/mem_darwin.go
@@ -53,7 +53,7 @@ func VirtualMemory() (*VirtualMemoryStat, error) {
 	}
 
 	ret := &VirtualMemoryStat{
-		Total: parsed[0] * p,
+		Total: parsed[0],
 		Free:  parsed[1] * p,
 	}
 
diff --git a/process/process_linux.go b/process/process_linux.go
index b7bd4e5..f7127ce 100644
--- a/process/process_linux.go
+++ b/process/process_linux.go
@@ -132,7 +132,8 @@ func (p *Process) NumCtxSwitches() (*NumCtxSwitchesStat, error) {
 	return p.numCtxSwitches, nil
 }
 func (p *Process) NumFDs() (int32, error) {
-	return 0, common.NotImplementedError
+	numFds, _, err := p.fillFromfd()
+	return numFds, err
 }
 func (p *Process) NumThreads() (int32, error) {
 	return p.numThreads, nil