Messages in this thread | | | Date | Tue, 11 Sep 2012 11:22:10 -0700 | From | Tejun Heo <> | Subject | Re: [PATCH RFC cgroup/for-3.7] cgroup: mark subsystems with broken hierarchy support and whine if cgroups are nested for them |
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Hello, Vivek.
On Tue, Sep 11, 2012 at 02:16:00PM -0400, Vivek Goyal wrote: > Ok, so whole point of warning seems to be so that we can change the > behavior in future and say to user space they few kernel releases back we > had started printing a warning that creating hierarchy is wrong and > move to a flat setup. So don't complain to us now.?
Yes, pretty much. At the moment, it's simply broken.
> Are you planning to get rid of .user_hierarchy file from memory cgroup > too? If you are planning not to put such a file in blkio controller, > then it will make sense to remove it from mem_cgorup too.
Yes, or at least make it RO 1 eventually.
> The point I am trying to make is that deep hierarchies (5-6 levels) are > /going to be a reality and if accounting overhead is not manageable then > enabling hierarchy by default might not be a practical solution even > if you implement hierarchy support (like memory cgroup), and in that > case retaining .use_hierarchy will make sense.
That doesn't make any sense to me. If you don't want feature and overhead of hierarchy, you just need to not create a hierarchy. If hierarchical behavior isn't needed, why create hierarchy at all?
> IIUC, are you saying that now none of the controller will have flat > hiearchy support because there is no way to be able to create flat > hierarchy. (Any new group is child of root group). So are we moving > towards a model where every controller is hierarhical and there is > no concept of flat hierarchy.
Yeap.
Thanks.
-- tejun
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