On Thu, May 18, 2017 at 07:30:04PM +0200, Michal Hocko wrote: > On Thu 18-05-17 17:28:04, Roman Gushchin wrote: > > Traditionally, the OOM killer is operating on a process level. > > Under oom conditions, it finds a process with the highest oom score > > and kills it. > > > > This behavior doesn't suit well the system with many running > > containers. There are two main issues: > > > > 1) There is no fairness between containers. A small container with > > a few large processes will be chosen over a large one with huge > > number of small processes. > > > > 2) Containers often do not expect that some random process inside > > will be killed. So, in general, a much safer behavior is > > to kill the whole cgroup. Traditionally, this was implemented > > in userspace, but doing it in the kernel has some advantages, > > especially in a case of a system-wide OOM. > > > > To address these issues, cgroup-aware OOM killer is introduced. > > Under OOM conditions, it looks for a memcg with highest oom score, > > and kills all processes inside. > > > > Memcg oom score is calculated as a size of active and inactive > > anon LRU lists, unevictable LRU list and swap size. > > > > For a cgroup-wide OOM, only cgroups belonging to the subtree of > > the OOMing cgroup are considered. > > While this might make sense for some workloads/setups it is not a > generally acceptable policy IMHO. We have discussed that different OOM > policies might be interesting few years back at LSFMM but there was no > real consensus on how to do that. One possibility was to allow bpf like > mechanisms. Could you explore that path? OOM policy is an orthogonal discussion, though. The OOM killer's job is to pick a memory consumer to kill. Per default the unit of the memory consumer is a process, but cgroups allow grouping processes into compound consumers. Extending the OOM killer to respect the new definition of "consumer" is not a new policy. I don't think it's reasonable to ask the person who's trying to make the OOM killer support group-consumers to design a dynamic OOM policy framework instead. All we want is the OOM policy, whatever it is, applied to cgroups. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
