Add a flag to set OOMScore

fix #337
Signed-off-by: yanxuean <yan.xuean@zte.com.cn>

pkg/server/service.go

@@ -29,6 +29,7 @@ import (
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/sys"
 	"github.com/cri-o/ocicni/pkg/ocicni"
 	"github.com/golang/glog"
 	runcapparmor "github.com/opencontainers/runc/libcontainer/apparmor"
@@ -121,6 +122,11 @@ func NewCRIContainerdService(config options.Config) (CRIContainerdService, error
 			return nil, fmt.Errorf("failed to load cgroup for cgroup path %v: %v", config.CgroupPath, err)
 		}
 	}
+	if config.OOMScore != 0 {
+		if err := sys.SetOOMScore(os.Getpid(), config.OOMScore); err != nil {
+			return nil, fmt.Errorf("failed to set OOMScore to %v: %v", config.OOMScore, err)
+		}
+	}
 
 	c := &criContainerdService{
 		config:              config,