Commit 6ba749ee authored by Shakeel Butt's avatar Shakeel Butt Committed by Linus Torvalds
Browse files

mm, oom: remove redundant task_in_mem_cgroup() check 

oom_unkillable_task() can be called from three different contexts i.e.
global OOM, memcg OOM and oom_score procfs interface.  At the moment
oom_unkillable_task() does a task_in_mem_cgroup() check on the given
process.  Since there is no reason to perform task_in_mem_cgroup()
check for global OOM and oom_score procfs interface, those contexts
provide NULL memcg and skips the task_in_mem_cgroup() check.  However
for memcg OOM context, the oom_unkillable_task() is always called from
mem_cgroup_scan_tasks() and thus task_in_mem_cgroup() check becomes
redundant and effectively dead code.  So, just remove the
task_in_mem_cgroup() check altogether.

Link: http://lkml.kernel.org/r/20190624212631.87212-2-shakeelb@google.com


Signed-off-by: default avatarShakeel Butt <shakeelb@google.com>
Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: default avatarRoman Gushchin <guro@fb.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Paul Jackson <pj@sgi.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5eee7e1c

fs/proc/base.c

+1 −1
Original line number Diff line number Diff line
@@ -532,7 +532,7 @@ static int proc_oom_score(struct seq_file *m, struct pid_namespace *ns, 
	unsigned long totalpages = totalram_pages() + total_swap_pages;

	unsigned long points = 0;



	points = oom_badness(task, NULL, NULL, totalpages) *

	points = oom_badness(task, NULL, totalpages) *

					1000 / totalpages;

	seq_printf(m, "%lu\n", points);

include/linux/memcontrol.h

+0 −7
Original line number Diff line number Diff line
@@ -394,7 +394,6 @@ out: 


struct lruvec *mem_cgroup_page_lruvec(struct page *, struct pglist_data *);



bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg);

struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);



struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm);
@@ -875,12 +874,6 @@ static inline bool mm_match_cgroup(struct mm_struct *mm, 
	return true;

}



static inline bool task_in_mem_cgroup(struct task_struct *task,

				      const struct mem_cgroup *memcg)

{

	return true;

}



static inline struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)

{

	return NULL;

include/linux/oom.h

+1 −1
Original line number Diff line number Diff line
@@ -108,7 +108,7 @@ static inline vm_fault_t check_stable_address_space(struct mm_struct *mm) 
bool __oom_reap_task_mm(struct mm_struct *mm);



extern unsigned long oom_badness(struct task_struct *p,

		struct mem_cgroup *memcg, const nodemask_t *nodemask,

		const nodemask_t *nodemask,

		unsigned long totalpages);



extern bool out_of_memory(struct oom_control *oc);

mm/memcontrol.c

+0 −26
Original line number Diff line number Diff line
@@ -1259,32 +1259,6 @@ void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru, 
		*lru_size += nr_pages;

}



bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg)

{

	struct mem_cgroup *task_memcg;

	struct task_struct *p;

	bool ret;



	p = find_lock_task_mm(task);

	if (p) {

		task_memcg = get_mem_cgroup_from_mm(p->mm);

		task_unlock(p);

	} else {

		/*

		 * All threads may have already detached their mm's, but the oom

		 * killer still needs to detect if they have already been oom

		 * killed to prevent needlessly killing additional tasks.

		 */

		rcu_read_lock();

		task_memcg = mem_cgroup_from_task(task);

		css_get(&task_memcg->css);

		rcu_read_unlock();

	}

	ret = mem_cgroup_is_descendant(task_memcg, memcg);

	css_put(&task_memcg->css);

	return ret;

}



/**

 * mem_cgroup_margin - calculate chargeable space of a memory cgroup

 * @memcg: the memory cgroup

mm/oom_kill.c

+7 −12
Original line number Diff line number Diff line
@@ -153,17 +153,13 @@ static inline bool is_memcg_oom(struct oom_control *oc) 


/* return true if the task is not adequate as candidate victim task. */

static bool oom_unkillable_task(struct task_struct *p,

		struct mem_cgroup *memcg, const nodemask_t *nodemask)

				const nodemask_t *nodemask)

{

	if (is_global_init(p))

		return true;

	if (p->flags & PF_KTHREAD)

		return true;



	/* When mem_cgroup_out_of_memory() and p is not member of the group */

	if (memcg && !task_in_mem_cgroup(p, memcg))

		return true;



	/* p may not have freeable memory in nodemask */

	if (!has_intersects_mems_allowed(p, nodemask))

		return true;
@@ -194,20 +190,19 @@ static bool is_dump_unreclaim_slabs(void) 
 * oom_badness - heuristic function to determine which candidate task to kill

 * @p: task struct of which task we should calculate

 * @totalpages: total present RAM allowed for page allocation

 * @memcg: task's memory controller, if constrained

 * @nodemask: nodemask passed to page allocator for mempolicy ooms

 *

 * The heuristic for determining which task to kill is made to be as simple and

 * predictable as possible.  The goal is to return the highest value for the

 * task consuming the most memory to avoid subsequent oom failures.

 */

unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,

unsigned long oom_badness(struct task_struct *p,

			  const nodemask_t *nodemask, unsigned long totalpages)

{

	long points;

	long adj;



	if (oom_unkillable_task(p, memcg, nodemask))

	if (oom_unkillable_task(p, nodemask))

		return 0;



	p = find_lock_task_mm(p);
@@ -318,7 +313,7 @@ static int oom_evaluate_task(struct task_struct *task, void *arg) 
	struct oom_control *oc = arg;

	unsigned long points;



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

	if (oom_unkillable_task(task, oc->nodemask))

		goto next;



	/*
@@ -342,7 +337,7 @@ static int oom_evaluate_task(struct task_struct *task, void *arg) 
		goto select;

	}



	points = oom_badness(task, NULL, oc->nodemask, oc->totalpages);

	points = oom_badness(task, oc->nodemask, oc->totalpages);

	if (!points || points < oc->chosen_points)

		goto next;
@@ -387,7 +382,7 @@ 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))

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

		return 0;



	task = find_lock_task_mm(p);
@@ -1084,7 +1079,7 @@ bool out_of_memory(struct oom_control *oc) 
	check_panic_on_oom(oc);



	if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&

	    current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&

	    current->mm && !oom_unkillable_task(current, oc->nodemask) &&

	    current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {

		get_task_struct(current);

		oc->chosen = current;

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