On 07/17/2017 10:14 AM, Peter Zijlstra wrote: > 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'. I agree with Peter on this. A new cgroup created under a threaded cgroup should always be threaded. I don't see a need for an intermediate invalid domain. Cheers, Longman -- 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
