On 10/31/2017 03:34 PM, Michal Hocko wrote: > On Tue 31-10-17 15:17:11, peter enderborg wrote: >> On 10/27/2017 10:05 PM, Johannes Weiner wrote: >>> On Thu, Oct 26, 2017 at 02:03:41PM -0700, David Rientjes wrote: >>>> On Thu, 26 Oct 2017, Johannes Weiner wrote: >>>> >>>>>> The nack is for three reasons: >>>>>> >>>>>> (1) unfair comparison of root mem cgroup usage to bias against that mem >>>>>> cgroup from oom kill in system oom conditions, >>>>>> >>>>>> (2) the ability of users to completely evade the oom killer by attaching >>>>>> all processes to child cgroups either purposefully or unpurposefully, >>>>>> and >>>>>> >>>>>> (3) the inability of userspace to effectively control oom victim >>>>>> selection. >>>>> My apologies if my summary was too reductionist. >>>>> >>>>> That being said, the arguments you repeat here have come up in >>>>> previous threads and been responded to. This doesn't change my >>>>> conclusion that your NAK is bogus. >>>> They actually haven't been responded to, Roman was working through v11 and >>>> made a change on how the root mem cgroup usage was calculated that was >>>> better than previous iterations but still not an apples to apples >>>> comparison with other cgroups. The problem is that it the calculation for >>>> leaf cgroups includes additional memory classes, so it biases against >>>> processes that are moved to non-root mem cgroups. Simply creating mem >>>> cgroups and attaching processes should not independently cause them to >>>> become more preferred: it should be a fair comparison between the root mem >>>> cgroup and the set of leaf mem cgroups as implemented. That is very >>>> trivial to do with hierarchical oom cgroup scoring. >>> There is absolutely no value in your repeating the same stuff over and >>> over again without considering what other people are telling you. >>> >>> Hierarchical oom scoring has other downsides, and most of us agree >>> that they aren't preferable over the differences in scoring the root >>> vs scoring other cgroups - in particular because the root cannot be >>> controlled, doesn't even have local statistics, and so is unlikely to >>> contain important work on a containerized system. Getting the ballpark >>> right for the vast majority of usecases is more than good enough here. >>> >>>> Since the ability of userspace to control oom victim selection is not >>>> addressed whatsoever by this patchset, and the suggested method cannot be >>>> implemented on top of this patchset as you have argued because it requires >>>> a change to the heuristic itself, the patchset needs to become complete >>>> before being mergeable. >>> It is complete. It just isn't a drop-in replacement for what you've >>> been doing out-of-tree for years. Stop making your problem everybody >>> else's problem. >>> >>> You can change the the heuristics later, as you have done before. Or >>> you can add another configuration flag and we can phase out the old >>> mode, like we do all the time. >>> >> I think this problem is related to the removal of the lowmemorykiller, >> where this is the life-line when the user-space for some reason fails. >> >> So I guess quite a few will have this problem. > Could you be more specific please? We are _not_ removing possibility of > the user space influenced oom victim selection. You can still use the > _current_ oom selection heuristic. The patch adds a new selection method > which is opt-in so only those who want to opt-in will not be allowed to > have any influence on the victim selection. And as it has been pointed > out this can be implemented later so it is not like "this won't be > possible anymore in future" I think the idea is to have a implementation that is lowmemorykiller selection heuristic. -- 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
