From: Shakeel Butt <shakeelb@xxxxxxxxxx> Subject: mm, oom: refactor dump_tasks for memcg OOMs 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. Link: http://lkml.kernel.org/r/20190617231207.160865-1-shakeelb@xxxxxxxxxx Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Acked-by: Roman Gushchin <guro@xxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Cc: Paul Jackson <pj@xxxxxxx> Cc: Nick Piggin <npiggin@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/oom_kill.c | 72 ++++++++++++++++++++++++++++-------------------- 1 file changed, 42 insertions(+), 30 deletions(-) --- a/mm/oom_kill.c~mm-oom-refactor-dump_tasks-for-memcg-ooms +++ a/mm/oom_kill.c @@ -382,10 +382,38 @@ static void select_bad_process(struct oo 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 @@ -393,37 +421,21 @@ static void select_bad_process(struct oo * 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; - } - - 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); + + if (is_memcg_oom(oc)) + mem_cgroup_scan_tasks(oc->memcg, dump_task, oc); + else { + struct task_struct *p; + + 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) @@ -455,7 +467,7 @@ static void dump_header(struct oom_contr dump_unreclaimable_slab(); } if (sysctl_oom_dump_tasks) - dump_tasks(oc->memcg, oc->nodemask); + dump_tasks(oc); if (p) dump_oom_summary(oc, p); } _
