On Wed 17-01-18 14:18:33, David Rientjes wrote: > On Wed, 17 Jan 2018, Michal Hocko wrote: > > > Absolutely agreed! And moreover, there are not all that many ways what > > to do as an action. You just kill a logical entity - be it a process or > > a logical group of processes. But you have way too many policies how > > to select that entity. Do you want to chose the youngest process/group > > because all the older ones have been computing real stuff and you would > > lose days of your cpu time? Or should those who pay more should be > > protected (aka give them static priorities), or you name it... > > > > That's an argument for making the interface extensible, yes. And there is no interface to control the selection yet so we can develop one on top. > > I am sorry, I still didn't grasp the full semantic of the proposed > > soluton but the mere fact it is starting by conflating selection and the > > action is a no go and a wrong API. This is why I've said that what you > > (David) outlined yesterday is probably going to suffer from a much > > longer discussion and most likely to be not acceptable. Your patchset > > proves me correct... > > I'm very happy to change the API if there are better suggestions. That > may end up just being an memory.oom_policy file, as this implements, and > separating out a new memory.oom_action that isn't a boolean value to > either do a full group kill or only a single process. Or it could be what > I suggested in my mail to Tejun, such as "hierarchy killall" written to > memory.oom_policy, which would specify a single policy and then an > optional mechanism. With my proposed patchset, there would then be three > policies: "none", "cgroup", and "tree" and one possible optional > mechanism: "killall". You haven't convinced me at all. This all sounds more like "what if" than a really thought through interface. I've tried to point out that having a real policy driven victim selection is a _hard_ thing to do _right_. On the other hand oom_group makes semantic sense. It controls the killable entity and there are usecases which want to consider the full memcg as a single killable entity. No matter what selection policy we chose on top. It is just a natural API. Now you keep arguing about the victim selection and different strategies to implement it. We will not move forward as long as you keep conflating the two things, I am afraid. -- 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
