On Tue 03-10-17 07:35:59, Tejun Heo wrote: > Hello, Michal. > > On Tue, Oct 03, 2017 at 04:22:46PM +0200, Michal Hocko wrote: > > On Tue 03-10-17 15:08:41, Roman Gushchin wrote: > > > On Tue, Oct 03, 2017 at 03:36:23PM +0200, Michal Hocko wrote: > > [...] > > > > I guess we want to inherit the value on the memcg creation but I agree > > > > that enforcing parent setting is weird. I will think about it some more > > > > but I agree that it is saner to only enforce per memcg value. > > > > > > I'm not against, but we should come up with a good explanation, why we're > > > inheriting it; or not inherit. > > > > Inheriting sounds like a less surprising behavior. Once you opt in for > > oom_group you can expect that descendants are going to assume the same > > unless they explicitly state otherwise. > > Here's a counter example. > > Let's say there's a container which hosts one main application, and > the container shares its host with other containers. > > * Let's say the container is a regular containerized OS instance and > can't really guarantee system integrity if one its processes gets > randomly killed. > > * However, the application that it's running inside an isolated cgroup > is more intelligent and composed of multiple interchangeable > processes and can treat killing of a random process as partial > capacity loss. > > When the host is setting up the outer container, it doesn't > necessarily know whether the containerized environment would be able > to handle partial OOM kills or not. It's akin to panic_on_oom setting > at system level - it's the containerized instance itself which knows > whether it can handle partial OOM kills or not. This is why this knob > should be delegatable. > > Now, the container itself has group OOM set and the isolated main > application is starting up. It obviously wants partial OOM kills > rather than group killing. This is the same principle. The > application which is being contained in the cgroup is the one which > knows how it can handle OOM conditions, not the outer environment, so > it obviously needs to be able to set the configuration it wants. Yes this makes a lot of sense. On the other hand we used to copy other reclaim specific atributes like swappiness and oom_kill_disable. I guess we should be OK with "non-hierarchical" behavior when it is documented properly so that there are surpasses. -- Michal Hocko SUSE Labs -- 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
