Comment 37 for bug 1392176

------- Comment From <email address hidden> 2015-04-09 02:55 EDT-------
(In reply to comment #36)
> > But I'm a bit worried, doesn't not mounting cpuset mean that containers,
> > for instance, wouldn't work so well?
>
> You just won't be able to lock containers to cpusets.
>
> > That is, even if cgmanager doesn't mount the cpuset cgroup, if
> > *anything* mounts it, processes in that cgroup tree will experience the
> > underlying issue, no?
>
> Yes.
>
> And I still think that systemd is currently mounting it regardless
> of cgmanager.
>
> So ideally the effective_cpus thing would be fixed to work for
> non-unified hierarchies.

Ok, so given the situation, I suggest the following:

Fixing this in the kernel will be an ugly hack. Moreover,
userspace must take care of updating cpusets after hotplug
operations. Therefore I see two ways forward:

1. Can systemd/cgmanager (whoever is mounting cgroups) mount
cpuset controllers under the unified hierarchy, while mounting the
rest under the legacy hierarchy? Here is the suggestion from the
community: https://lkml.org/lkml/2015/4/6/196.

2. Systemd/cgmanager must have a daemon listening to hotplug
events. On hotplug, the parent cgroups cpuset must be percolated
down to the children. This is a better solution because the situation
where cpus are hotplugged in for the first time (i.e from the
cpu_possible_mask to cpu_online_mask), will be handled too.

Can either of the above be done in systemd/cgmanager ?

Regards
Preeti U Murthy