fix container RSS memory calculation with cgroup v2 stats.

cgroup/memory.go

@@ -47,17 +47,13 @@ func (cg *Cgroup) memoryStatV1() (*MemoryStat, error) {
 }
 
 func (cg *Cgroup) memoryStatV2() (*MemoryStat, error) {
-	current, err := readUintFromFile(path.Join(cgRoot, cg.subsystems[""], "memory.current"))
-	if err != nil {
-		return nil, err
-	}
 	vars, err := readVariablesFromFile(path.Join(cgRoot, cg.subsystems[""], "memory.stat"))
 	if err != nil {
 		return nil, err
 	}
 	limit, _ := readUintFromFile(path.Join(cgRoot, cg.subsystems[""], "memory.max"))
 	return &MemoryStat{
-		RSS:   current - vars["file"],
+		RSS:   vars["anon"] + vars["file_mapped"],
 		Cache: vars["file"],
 		Limit: limit,
 	}, nil

cgroup/memory_test.go

@@ -25,14 +25,14 @@ func TestCgroup_MemoryStat(t *testing.T) {
 	cg, _ = NewFromProcessCgroupFile(path.Join("fixtures/proc/400/cgroup"))
 	stat, err = cg.MemoryStat()
 	assert.Nil(t, err)
-	assert.Equal(t, uint64(48648192-1044480), stat.RSS)
+	assert.Equal(t, uint64(44892160+0), stat.RSS)
 	assert.Equal(t, uint64(1044480), stat.Cache)
 	assert.Equal(t, uint64(0), stat.Limit)
 
 	cg, _ = NewFromProcessCgroupFile(path.Join("fixtures/proc/500/cgroup"))
 	stat, err = cg.MemoryStat()
 	assert.Nil(t, err)
-	assert.Equal(t, uint64(131047424-50835456), stat.RSS)
+	assert.Equal(t, uint64(75247616+4038656), stat.RSS)
 	assert.Equal(t, uint64(50835456), stat.Cache)
 	assert.Equal(t, uint64(4294967296), stat.Limit)