On Sun, Jul 16, 2017 at 10:07:20PM -0400, Tejun Heo wrote: > > v4: - Updated to marking each cgroup threaded as suggested by PeterZ. > > +On creation, a cgroup is always a domain cgroup and can be made > +threaded by writing "threaded" to the "cgroup.type" file. The > +operation is single direction:: > + > + # echo threaded > cgroup.type > + > +Once threaded, the cgroup can't be made a domain again. To enable the > +thread mode, the following conditions must be met. > + > +- As the cgroup will join the parent's resource domain. The parent > + must either be a valid (threaded) domain or a threaded cgroup. > + > +- The cgroup must be empty. No enabled controllers, child cgroups or > + processes. > + > +Topology-wise, a cgroup can be in an invalid state. Please consider > +the following toplogy:: > + > + A (threaded domain) - B (threaded) - C (domain, just created) > + > +C is created as a domain but isn't connected to a parent which can > +host child domains. C can't be used until it is turned into a > +threaded cgroup. "cgroup.type" file will report "domain (invalid)" in > +these cases. Operations which fail due to invalid topology use > +EOPNOTSUPP as the errno. > + > +A domain cgroup is turned into a threaded domain when one of its child > +cgroup becomes threaded or threaded controllers are enabled in the > +"cgroup.subtree_control" file while there are processes in the cgroup. > +A threaded domain reverts to a normal domain when the conditions > +clear. AFAICT this is not in fact what I suggested... :/ My proposal did not have that invalid state. It would simply refuse to change the type from thread to domain in the case where the parent is not a domain. Also, my proposal maintained the normal property inheritance rules. A child cgroup's creation 'type' would be that of its parent and not always be 'domain'. Let me read more (and more careful) to see if there's other things. -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
