daemon: Use nice/ionice when extracting oscontainer too

We switched rpm-ostree to do this when applying updates, but
it also makes sense to do when extracting the oscontainer.

Part of: openshift#1897
Which is about staging OS updates more nicely when etcd is running.

pkg/daemon/pivot/utils/run.go

@@ -65,3 +65,16 @@ func RunExt(retries int, command string, args ...string) (string, error) {
 	},
 		command, args...)
 }
+
+// RunExtBackground is like RunExt, but queues the command for "nice" CPU and
+// I/O scheduling.
+func RunExtBackground(retries int, command string, args ...string) (string, error) {
+	args = append([]string{"--", "ionice", "-c", "3", command}, args...)
+	command = "nice"
+	return runExtBackoff(wait.Backoff{
+		Steps:    retries + 1,     // times to try
+		Duration: 5 * time.Second, // sleep between tries
+		Factor:   2,               // factor by which to increase sleep
+	},
+		command, args...)
+}

pkg/daemon/pivot/utils/run_test.go

@@ -27,3 +27,9 @@ func TestRunExt(t *testing.T) {
 	assert.Nil(t, err)
 	assert.Equal(t, int64(3), s.Size())
 }
+
+func TestRunExtBackground(t *testing.T) {
+	o, err := RunExtBackground(0, "echo", "echo", "from", "TestRunExtBackground")
+	assert.Nil(t, err)
+	assert.Equal(t, o, "echo from TestRunExtBackground")
+}

pkg/daemon/update.go

@@ -238,7 +238,7 @@ func podmanCopy(imgURL, osImageContentDir string) (err error) {
 	args := []string{"pull", "-q"}
 	args = append(args, authArgs...)
 	args = append(args, imgURL)
-	_, err = pivotutils.RunExt(numRetriesNetCommands, "podman", args...)
+	_, err = pivotutils.RunExtBackground(numRetriesNetCommands, "podman", args...)
 	if err != nil {
 		return
 	}
@@ -257,7 +257,7 @@ func podmanCopy(imgURL, osImageContentDir string) (err error) {
 	// copy the content from create container locally into a temp directory under /run/machine-os-content/
 	cid := strings.TrimSpace(string(cidBuf))
 	args = []string{"cp", fmt.Sprintf("%s:/", cid), osImageContentDir}
-	_, err = pivotutils.RunExt(numRetriesNetCommands, "podman", args...)
+	_, err = pivotutils.RunExtBackground(numRetriesNetCommands, "podman", args...)
 
 	// Set selinux context to var_run_t to avoid selinux denial
 	args = []string{"-R", "-t", "var_run_t", osImageContentDir}
@@ -294,7 +294,7 @@ func ExtractOSImage(imgURL string) (osImageContentDir string, err error) {
 	args := []string{"image", "extract", "--path", "/:" + osImageContentDir}
 	args = append(args, registryConfig...)
 	args = append(args, imgURL)
-	if _, err = pivotutils.RunExt(cmdRetriesCount, "oc", args...); err != nil {
+	if _, err = pivotutils.RunExtBackground(cmdRetriesCount, "oc", args...); err != nil {
 		// Workaround fixes for the environment where oc image extract fails.
 		// See https://bugzilla.redhat.com/show_bug.cgi?id=1862979
 		glog.Infof("Falling back to using podman cp to fetch OS image content")