On Wed, Oct 04, 2017 at 03:27:20PM -0400, Johannes Weiner wrote: > On Wed, Oct 04, 2017 at 04:46:35PM +0100, 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: > > > > 1) There is no fairness between containers. A small container with > > 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. In many cases much safer behavior is to kill > > all tasks in the container. 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, the cgroup-aware OOM killer is introduced. > > > > Under OOM conditions, it looks for the biggest leaf memory cgroup > > and kills the biggest task belonging to it. The following patches > > will extend this functionality to consider non-leaf memory cgroups > > as well, and also provide an ability to kill all tasks belonging > > to the victim cgroup. > > > > The root cgroup is treated as a leaf memory cgroup, so it's score > > is compared with leaf memory cgroups. > > Due to memcg statistics implementation a special algorithm > > is used for estimating it's oom_score: we define it as maximum > > oom_score of the belonging tasks. > > > > Signed-off-by: Roman Gushchin <guro@xxxxxx> > > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > > Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> > > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > > Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> > > Cc: David Rientjes <rientjes@xxxxxxxxxx> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Cc: Tejun Heo <tj@xxxxxxxxxx> > > Cc: kernel-team@xxxxxx > > Cc: cgroups@xxxxxxxxxxxxxxx > > Cc: linux-doc@xxxxxxxxxxxxxxx > > Cc: linux-kernel@xxxxxxxxxxxxxxx > > Cc: linux-mm@xxxxxxxxx > > This looks good to me. > > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > I just have one question: > > > @@ -828,6 +828,12 @@ static void __oom_kill_process(struct task_struct *victim) > > struct mm_struct *mm; > > bool can_oom_reap = true; > > > > + if (is_global_init(victim) || (victim->flags & PF_KTHREAD) || > > + victim->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) { > > + put_task_struct(victim); > > + return; > > + } > > + > > p = find_lock_task_mm(victim); > > if (!p) { > > put_task_struct(victim); > > Is this necessary? The callers of this function use oom_badness() to > find a victim, and that filters init, kthread, OOM_SCORE_ADJ_MIN. It is. __oom_kill_process() is used to kill all processes belonging to the selected memory cgroup, so we should perform these checks to avoid killing unkillable processes. Thanks! -- 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