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Commit 5eee7e1c authored by Shakeel Butt's avatar Shakeel Butt Committed by Linus Torvalds
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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@google.com


Signed-off-by: default avatarShakeel Butt <shakeelb@google.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Acked-by: default avatarRoman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f168a9a5

mm/oom_kill.c

+40 −28
Original line number Diff line number Diff line
@@ -382,28 +382,13 @@ static void select_bad_process(struct oom_control *oc) 
	oc->chosen_points = oc->chosen_points * 1000 / oc->totalpages;

}



/**

 * 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

 *

 * 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

 * are not shown.

 * 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 int dump_task(struct task_struct *p, void *arg)

{

	struct task_struct *p;

	struct oom_control *oc = arg;

	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;

	if (oom_unkillable_task(p, NULL, oc->nodemask))

		return 0;



	task = find_lock_task_mm(p);

	if (!task) {
@@ -412,7 +397,7 @@ static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask) 
		 * detached their mm's.  There's no need to report

		 * them; they can't be oom killed anyway.

		 */

			continue;

		return 0;

	}



	pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu         %5hd %s\n",
@@ -422,9 +407,36 @@ static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask) 
		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

 * @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

 * are not shown.

 * 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 oom_control *oc)

{

	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");



	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();

	}

}



static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)

{
@@ -455,7 +467,7 @@ 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);

}