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Subject[PATCH v3 2/3] mm, oom: remove redundant task_in_mem_cgroup() check
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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. So, just remove the task_in_mem_cgroup() check altogether.

Signed-off-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
Changelog since v2:
- Further divided the patch into two patches.
- Incorporated the task_in_mem_cgroup() from Tetsuo.

Changelog since v1:
- Divide the patch into two patches.

fs/proc/base.c | 2 +-
include/linux/memcontrol.h | 7 -------
include/linux/oom.h | 2 +-
mm/memcontrol.c | 26 --------------------------
mm/oom_kill.c | 19 +++++++------------
5 files changed, 9 insertions(+), 47 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index b8d5d100ed4a..5eacce5e924a 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -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);

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 9abf31bbe53a..2cbce1fe7780 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -407,7 +407,6 @@ static inline struct lruvec *mem_cgroup_lruvec(struct pglist_data *pgdat,

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);
@@ -896,12 +895,6 @@ 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;
diff --git a/include/linux/oom.h b/include/linux/oom.h
index d07992009265..b75104690311 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -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);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index db46a9dc37ab..27c92c2b99be 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -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
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index bd80997e0969..e0cdcbd58b0b 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -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;

@@ -390,7 +385,7 @@ 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);
@@ -1090,7 +1085,7 @@ bool out_of_memory(struct oom_control *oc)
check_panic_on_oom(oc, constraint);

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;
--
2.22.0.410.gd8fdbe21b5-goog
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