On Mon 17-06-19 16:12:06, Shakeel Butt wrote: > dump_tasks() currently goes through all the processes present on the > system even for memcg OOMs. Change dump_tasks() similar to > select_bad_process() and use mem_cgroup_scan_tasks() to selectively > traverse the processes of the memcgs during memcg OOM.
The changelog is quite modest to be honest. I would go with " dump_tasks() traverses all the existing processes even for the memcg OOM context which is not only unnecessary but also wasteful. This imposes a long RCU critical section even from a contained context which can be quite disruptive. Change dump_tasks() to be aligned with select_bad_process and use mem_cgroup_scan_tasks to selectively traverse only processes of the target memcg hierarchy during memcg OOM. " > Signed-off-by: Shakeel Butt <[email protected]> Acked-by: Michal Hocko <[email protected]> Thanks! > --- > Changelog since v1: > - Divide the patch into two patches. > > mm/oom_kill.c | 68 ++++++++++++++++++++++++++++++--------------------- > 1 file changed, 40 insertions(+), 28 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 05aaa1a5920b..bd80997e0969 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -385,10 +385,38 @@ static void select_bad_process(struct oom_control *oc) > oc->chosen_points = oc->chosen_points * 1000 / oc->totalpages; > } > > +static int dump_task(struct task_struct *p, void *arg) > +{ > + struct oom_control *oc = arg; > + struct task_struct *task; > + > + if (oom_unkillable_task(p, NULL, oc->nodemask)) > + return 0; > + > + task = find_lock_task_mm(p); > + if (!task) { > + /* > + * This is a kthread or all of p's threads have already > + * detached their mm's. There's no need to report > + * them; they can't be oom killed anyway. > + */ > + return 0; > + } > + > + pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n", > + task->pid, from_kuid(&init_user_ns, task_uid(task)), > + task->tgid, task->mm->total_vm, get_mm_rss(task->mm), > + mm_pgtables_bytes(task->mm), > + get_mm_counter(task->mm, MM_SWAPENTS), > + task->signal->oom_score_adj, task->comm); > + task_unlock(task); > + > + return 0; > +} > + > /** > * dump_tasks - dump current memory state of all system tasks > - * @memcg: current's memory controller, if constrained > - * @nodemask: nodemask passed to page allocator for mempolicy ooms > + * @oc: pointer to struct oom_control > * > * Dumps the current memory state of all eligible tasks. Tasks not in the > same > * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy > nodes > @@ -396,37 +424,21 @@ static void select_bad_process(struct oom_control *oc) > * State information includes task's pid, uid, tgid, vm size, rss, > * pgtables_bytes, swapents, oom_score_adj value, and name. > */ > -static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask) > +static void dump_tasks(struct oom_control *oc) > { > - struct task_struct *p; > - struct task_struct *task; > - > pr_info("Tasks state (memory values in pages):\n"); > pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes > swapents oom_score_adj name\n"); > - rcu_read_lock(); > - for_each_process(p) { > - if (oom_unkillable_task(p, memcg, nodemask)) > - continue; > > - task = find_lock_task_mm(p); > - if (!task) { > - /* > - * This is a kthread or all of p's threads have already > - * detached their mm's. There's no need to report > - * them; they can't be oom killed anyway. > - */ > - continue; > - } > + if (is_memcg_oom(oc)) > + mem_cgroup_scan_tasks(oc->memcg, dump_task, oc); > + else { > + struct task_struct *p; > > - pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n", > - task->pid, from_kuid(&init_user_ns, task_uid(task)), > - task->tgid, task->mm->total_vm, get_mm_rss(task->mm), > - mm_pgtables_bytes(task->mm), > - get_mm_counter(task->mm, MM_SWAPENTS), > - task->signal->oom_score_adj, task->comm); > - task_unlock(task); > + rcu_read_lock(); > + for_each_process(p) > + dump_task(p, oc); > + rcu_read_unlock(); > } > - rcu_read_unlock(); > } > > static void dump_oom_summary(struct oom_control *oc, struct task_struct > *victim) > @@ -458,7 +470,7 @@ static void dump_header(struct oom_control *oc, struct > task_struct *p) > dump_unreclaimable_slab(); > } > if (sysctl_oom_dump_tasks) > - dump_tasks(oc->memcg, oc->nodemask); > + dump_tasks(oc); > if (p) > dump_oom_summary(oc, p); > } > -- > 2.22.0.410.gd8fdbe21b5-goog > -- Michal Hocko SUSE Labs
