On Wed 13-09-17 13:46:08, David Rientjes wrote: > On Wed, 13 Sep 2017, Michal Hocko wrote: > > > > > This patchset makes the OOM killer cgroup-aware. > > > > > > > > v8: > > > > - Do not kill tasks with OOM_SCORE_ADJ -1000 > > > > - Make the whole thing opt-in with cgroup mount option control > > > > - Drop oom_priority for further discussions > > > > > > Nack, we specifically require oom_priority for this to function > > > correctly, > > > otherwise we cannot prefer to kill from low priority leaf memcgs as > > > required. > > > > While I understand that your usecase might require priorities I do not > > think this part missing is a reason to nack the cgroup based selection > > and kill-all parts. This can be done on top. The only important part > > right now is the current selection semantic - only leaf memcgs vs. size > > of the hierarchy). I strongly believe that comparing only leaf memcgs > > is more straightforward and it doesn't lead to unexpected results as > > mentioned before (kill a small memcg which is a part of the larger > > sub-hierarchy). > > > > The problem is that we cannot enable the cgroup-aware oom killer and > oom_group behavior because, without oom priorities, we have no ability to > influence the cgroup that it chooses. It is doing two things: providing > more fairness amongst cgroups by selecting based on cumulative usage > rather than single large process (good!), and effectively is removing all > userspace control of oom selection (bad). We want the former, but it > needs to be coupled with support so that we can protect vital cgroups, > regardless of their usage.
I understand that your usecase needs a more fine grained control over the selection but that alone is not a reason to nack the implementation which doesn't provide it (yet). > It is certainly possible to add oom priorities on top before it is merged, > but I don't see why it isn't part of the patchset. Because the semantic of the priority for non-leaf memcgs is not fully clear and I would rather have the core of the functionality merged before this is sorted out. > We need it before its > merged to avoid users playing with /proc/pid/oom_score_adj to prevent any > killing in the most preferable memcg when they could have simply changed > the oom priority. I am sorry but I do not really understand your concern. Are you suggesting that users would start oom disable all tasks in a memcg to give it a higher priority? Even if that was the case why should such an abuse be a blocker for generic memcg aware oom killer being merged? -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
