From 53e7986bc00d0223b4c240db5f876fa81ff3f050 Mon Sep 17 00:00:00 2001
From: Vishnu kannan <vishnuk@google.com>
Date: Wed, 7 Oct 2015 17:36:19 -0700
Subject: [PATCH] Reduce cpu priority for `du`.

---
 fs/fs.go      |  2 +-
 fs/fs_test.go | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/fs/fs.go b/fs/fs.go
index 00c06456..ebf8273b 100644
--- a/fs/fs.go
+++ b/fs/fs.go
@@ -282,7 +282,7 @@ func (self *RealFsInfo) GetDirFsDevice(dir string) (*DeviceInfo, error) {
 }
 
 func (self *RealFsInfo) GetDirUsage(dir string) (uint64, error) {
-	out, err := exec.Command("du", "-s", dir).CombinedOutput()
+	out, err := exec.Command("nice", "-n", "19", "du", "-s", dir).CombinedOutput()
 	if err != nil {
 		return 0, fmt.Errorf("du command failed on %s with output %s - %s", dir, out, err)
 	}
diff --git a/fs/fs_test.go b/fs/fs_test.go
index 2071f02d..80b39787 100644
--- a/fs/fs_test.go
+++ b/fs/fs_test.go
@@ -15,7 +15,11 @@
 package fs
 
 import (
+	"io/ioutil"
+	"os"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestGetDiskStatsMap(t *testing.T) {
@@ -76,3 +80,23 @@ func TestFileNotExist(t *testing.T) {
 		t.Fatalf("getDiskStatsMap must not error for absent file: %s", err)
 	}
 }
+
+func TestDirUsage(t *testing.T) {
+	as := assert.New(t)
+	fsInfo, err := NewFsInfo(Context{})
+	as.NoError(err)
+	dir, err := ioutil.TempDir(os.TempDir(), "")
+	as.NoError(err)
+	defer os.RemoveAll(dir)
+	dataSize := 1024 * 100 //100 KB
+	b := make([]byte, dataSize)
+	f, err := ioutil.TempFile(dir, "")
+	as.NoError(err)
+	as.NoError(ioutil.WriteFile(f.Name(), b, 0700))
+	fi, err := f.Stat()
+	as.NoError(err)
+	expectedSize := uint64(fi.Size())
+	size, err := fsInfo.GetDirUsage(dir)
+	as.NoError(err)
+	as.True(expectedSize <= size, "expected dir size to be at-least %d; got size: %d", expectedSize, size)
+}