1 files changed, 21 insertions, 0 deletions

diff --git a/Documentation/scheduler/sched-design-CFS.txt b/Documentation/scheduler/sched-design-CFS.txt
index eb471c7a905e..8398ca4ff4ed 100644
--- a/Documentation/scheduler/sched-design-CFS.txt
+++ b/Documentation/scheduler/sched-design-CFS.txt
@@ -273,3 +273,24 @@ task groups and modify their CPU share using the "cgroups" pseudo filesystem.
 
         # #Launch gmplayer (or your favourite movie player)
         # echo <movie_player_pid> > multimedia/tasks
+
+8. Implementation note: user namespaces
+
+User namespaces are intended to be hierarchical.  But they are currently
+only partially implemented.  Each of those has ramifications for CFS.
+
+First, since user namespaces are hierarchical, the /sys/kernel/uids
+presentation is inadequate.  Eventually we will likely want to use sysfs
+tagging to provide private views of /sys/kernel/uids within each user
+namespace.
+
+Second, the hierarchical nature is intended to support completely
+unprivileged use of user namespaces.  So if using user groups, then
+we want the users in a user namespace to be children of the user
+who created it.
+
+That is currently unimplemented.  So instead, every user in a new
+user namespace will receive 1024 shares just like any user in the
+initial user namespace.  Note that at the moment creation of a new
+user namespace requires each of CAP_SYS_ADMIN, CAP_SETUID, and
+CAP_SETGID.