On Fri 15-09-17 08:23:01, Roman Gushchin wrote: > On Fri, Sep 15, 2017 at 12:58:26PM +0200, Michal Hocko wrote: > > On Thu 14-09-17 09:05:48, Roman Gushchin wrote: > > > On Thu, Sep 14, 2017 at 03:40:14PM +0200, Michal Hocko wrote: > > > > On Wed 13-09-17 14:56:07, Roman Gushchin wrote: > > > > > On Wed, Sep 13, 2017 at 02:29:14PM +0200, Michal Hocko wrote: > > > > [...] > > > > > > I strongly believe that comparing only leaf memcgs > > > > > > is more straightforward and it doesn't lead to unexpected results as > > > > > > mentioned before (kill a small memcg which is a part of the larger > > > > > > sub-hierarchy). > > > > > > > > > > One of two main goals of this patchset is to introduce cgroup-level > > > > > fairness: bigger cgroups should be affected more than smaller, > > > > > despite the size of tasks inside. I believe the same principle > > > > > should be used for cgroups. > > > > > > > > Yes bigger cgroups should be preferred but I fail to see why bigger > > > > hierarchies should be considered as well if they are not kill-all. And > > > > whether non-leaf memcgs should allow kill-all is not entirely clear to > > > > me. What would be the usecase? > > > > > > We definitely want to support kill-all for non-leaf cgroups. > > > A workload can consist of several cgroups and we want to clean up > > > the whole thing on OOM. > > > > Could you be more specific about such a workload? E.g. how can be such a > > hierarchy handled consistently when its sub-tree gets killed due to > > internal memory pressure? > > Or just system-wide OOM. > > > Or do you expect that none of the subtree will > > have hard limit configured? > > And this can also be a case: the whole workload may have hard limit > configured, while internal memcgs have only memory.low set for "soft" > prioritization. > > > > > But then you just enforce a structural restriction on your configuration > > because > > root > > / \ > > A D > > /\ > > B C > > > > is a different thing than > > root > > / | \ > > B C D > > > > I actually don't have a strong argument against an approach to select > largest leaf or kill-all-set memcg. I think, in practice there will be > no much difference. Well, I am worried that the difference will come unexpected when a deeper hierarchy is needed because of the structural needs. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
