Documentation: update cgroup pid and cpuset information
The cgroup documentation does not specify how a process can be removed
from a particular group. This patch adds a note at the end of the
simple example about how this is done. Also, some cgroups (like
cpusets) require user input before a new group can be used. This is
noted in the patch as well.
Signed-off-by: Eric B Munson <emunson@mgebm.net>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index 44b8b7a..cbdfb7d 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -349,6 +349,10 @@
The "xxx" is not interpreted by the cgroup code, but will appear in
/proc/mounts so may be any useful identifying string that you like.
+Note: Some subsystems do not work without some user input first. For instance,
+if cpusets are enabled the user will have to populate the cpus and mems files
+for each new cgroup created before that group can be used.
+
To mount a cgroup hierarchy with just the cpuset and memory
subsystems, type:
# mount -t cgroup -o cpuset,memory hier1 /dev/cgroup
@@ -426,6 +430,14 @@
# echo 0 > tasks
+Note: Since every task is always a member of exactly one cgroup in each
+mounted hierarchy, to remove a task from its current cgroup you must
+move it into a new cgroup (possibly the root cgroup) by writing to the
+new cgroup's tasks file.
+
+Note: If the ns cgroup is active, moving a process to another cgroup can
+fail.
+
2.3 Mounting hierarchies by name
--------------------------------