Fix oom tests on non Linux

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>

sys/oom_linux.go

@@ -0,0 +1,61 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package sys
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/containerd/containerd/pkg/userns"
+)
+
+const (
+	// OOMScoreMaxKillable is the maximum score keeping the process killable by the oom killer
+	OOMScoreMaxKillable = -999
+	// OOMScoreAdjMax is from OOM_SCORE_ADJ_MAX https://github.com/torvalds/linux/blob/master/include/uapi/linux/oom.h
+	OOMScoreAdjMax = 1000
+)
+
+// SetOOMScore sets the oom score for the provided pid
+func SetOOMScore(pid, score int) error {
+	path := fmt.Sprintf("/proc/%d/oom_score_adj", pid)
+	f, err := os.OpenFile(path, os.O_WRONLY, 0)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if _, err = f.WriteString(strconv.Itoa(score)); err != nil {
+		if os.IsPermission(err) && (userns.RunningInUserNS() || RunningUnprivileged()) {
+			return nil
+		}
+		return err
+	}
+	return nil
+}
+
+// GetOOMScoreAdj gets the oom score for a process
+func GetOOMScoreAdj(pid int) (int, error) {
+	path := fmt.Sprintf("/proc/%d/oom_score_adj", pid)
+	data, err := ioutil.ReadFile(path)
+	if err != nil {
+		return 0, err
+	}
+	return strconv.Atoi(strings.TrimSpace(string(data)))
+}