Hello, Michal. On Wed, Jun 27, 2012 at 12:08:09AM +0200, Michal Hocko wrote: > According to my experience, people usually create deeper subtrees > just because they want to have memcg hierarchy together with other > controller(s) and the other controller requires a different topology > but then they do not care about memory.* attributes in parents. > Those cases are not affected by this change because parents are > unlimited by default. > Deeper subtrees without hierarchy and independent limits are usually > mis-configurations, and we would like to hear about those to help to fix > them, or they are unfixable usecases which we want to know about as well > (because then we have a blocker for the unified cgroup hierarchy, don't > we). Yeah, this is something I'm seriously considering doing from cgroup core. ie. generating a warning message if the user nests cgroups w/ controllers which don't support full hierarchy. > > Note that the default should still be flat hierarchy. > > > > 2. Mark flat hierarchy deprecated and produce a warning message if > > memcg is mounted w/o hierarchy option for a year or two. > > I would agree with you on this with many kernel configurables but > this one doesn't fall in. There is a trivial fallback (set root to > use_hierarchy=0) so the mount option seems like an overkill - yet > another API to keep for some time... Just disallow clearing .use_hierarchy if it was mounted with the option? We can later either make the file RO 1 for compatibility's sake or remove it. > So in short, I do think we should go the sanity path and end up > with hierarchical trees and sooner we start the better. I do agree with you in principle, but I still don't think we can switch the default behavior underneath the users. Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>