Hello, On Fri, Sep 22, 2017 at 01:39:55PM -0700, David Rientjes wrote: > Current heuristic based on processes is coupled with per-process > /proc/pid/oom_score_adj. The proposed > heuristic has no ability to be influenced by userspace, and it needs one. > The proposed heuristic based on memory cgroups coupled with Roman's > per-memcg memory.oom_priority is appropriate and needed. It is not So, this is where we disagree. I don't think it's a good design. > "sophisticated intelligence," it merely allows userspace to protect vital > memory cgroups when opting into the new features (cgroups compared based > on size and memory.oom_group) that we very much want. which can't achieve that goal very well for wide variety of users. > > We even change the whole scheduling behaviors and try really hard to > > not get locked into specific implementation details which exclude > > future improvements. Guaranteeing OOM killing selection would be > > crazy. Why would we prevent ourselves from doing things better in the > > future? We aren't talking about the semantics of read(2) here. This > > is a kernel emergency mechanism to avoid deadlock at the last moment. > > We merely want to prefer other memory cgroups are oom killed on system oom > conditions before important ones, regardless if the important one is using > more memory than the others because of the new heuristic this patchset > introduces. This is exactly the same as /proc/pid/oom_score_adj for the > current heuristic. You were arguing that we should lock into a specific heuristics and guarantee the same behavior. We shouldn't. When we introduce a user visible interface, we're making a lot of promises. My point is that we need to be really careful when making those promises. > If you have this low priority maintenance job charging memory to the high > priority hierarchy, you're already misconfigured unless you adjust > /proc/pid/oom_score_adj because it will oom kill any larger process than > itself in today's kernels anyway. > > A better configuration would be attach this hypothetical low priority > maintenance job to its own sibling cgroup with its own memory limit to > avoid exactly that problem: it going berserk and charging too much memory > to the high priority container that results in one of its processes > getting oom killed. And how do you guarantee that across delegation boundaries? The points you raise on why the priority should be applied level-by-level are exactly the same points why this doesn't really work. OOM killing priority isn't something which can be distributed across cgroup hierarchy level-by-level. The resulting decision tree doesn't make any sense. I'm not against adding something which works but strict level-by-level comparison isn't the solution. Thanks. -- tejun -- 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
