On Tue, Aug 15, 2017 at 01:56:24PM -0700, David Rientjes wrote: > On Tue, 15 Aug 2017, Roman Gushchin wrote: > > > > > diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt > > > > index dec5afdaa36d..22108f31e09d 100644 > > > > --- a/Documentation/cgroup-v2.txt > > > > +++ b/Documentation/cgroup-v2.txt > > > > @@ -48,6 +48,7 @@ v1 is available under Documentation/cgroup-v1/. > > > > 5-2-1. Memory Interface Files > > > > 5-2-2. Usage Guidelines > > > > 5-2-3. Memory Ownership > > > > + 5-2-4. Cgroup-aware OOM Killer > > > > > > Random curiousness, why cgroup-aware oom killer and not memcg-aware oom > > > killer? > > > > I don't think we use the term "memcg" somewhere in v2 docs. > > Do you think that "Memory cgroup-aware OOM killer" is better? > > > > I think it would be better to not describe it as its own entity, but > rather a part of how the memory cgroup works, so simply describing it in > section 5-2, perhaps as its own subsection, as how the oom killer works > when using the memory cgroup is sufficient. I wouldn't separate it out as > a distinct cgroup feature in the documentation. Ok I've got the idea, let me look, what I can do. I'll post an updated version soon. > > > > > + cgroups. The default is "0". > > > > + > > > > + Defines whether the OOM killer should treat the cgroup > > > > + as a single entity during the victim selection. > > > > > > Isn't this true independent of the memory.oom_kill_all_tasks setting? > > > The cgroup aware oom killer will consider memcg's as logical units when > > > deciding what to kill with or without memory.oom_kill_all_tasks, right? > > > > > > I think you cover this fact in the cgroup aware oom killer section below > > > so this might result in confusion if described alongside a setting of > > > memory.oom_kill_all_tasks. > > > > > I assume this is fixed so that it's documented that memory cgroups are > considered logical units by the oom killer and that > memory.oom_kill_all_tasks is separate? The former defines the policy on > how a memory cgroup is targeted and the latter defines the mechanism it > uses to free memory. Yes, I've fixed this. Thanks! > > > > +Cgroup-aware OOM Killer > > > > +~~~~~~~~~~~~~~~~~~~~~~~ > > > > + > > > > +Cgroup v2 memory controller implements a cgroup-aware OOM killer. > > > > +It means that it treats memory cgroups as first class OOM entities. > > > > + > > > > +Under OOM conditions the memory controller tries to make the best > > > > +choise of a victim, hierarchically looking for the largest memory > > > > +consumer. By default, it will look for the biggest task in the > > > > +biggest leaf cgroup. > > > > + > > > > +Be default, all cgroups have oom_priority 0, and OOM killer will > > > > +chose the largest cgroup recursively on each level. For non-root > > > > +cgroups it's possible to change the oom_priority, and it will cause > > > > +the OOM killer to look athe the priority value first, and compare > > > > +sizes only of cgroups with equal priority. > > > > > > Maybe some description of "largest" would be helpful here? I think you > > > could briefly describe what is accounted for in the decisionmaking. > > > > I'm afraid that it's too implementation-defined to be described. > > Do you have an idea, how to describe it without going too much into details? > > > > The point is that "largest cgroup" is ambiguous here: largest in what > sense? The cgroup with the largest number of processes attached? Using > the largest amount of memory? > > I think the documentation should clearly define that the oom killer > selects the memory cgroup that has the most memory managed at each level. No problems, I'll add a clarification. Thank you! -- 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
