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mm, memcg: don't take task_lock in task_in_mem_cgroup 

For processes that have detached their mm's, task_in_mem_cgroup()
unnecessarily takes task_lock() when rcu_read_lock() is all that is
necessary to call mem_cgroup_from_task().

While we're here, switch task_in_mem_cgroup() to return bool.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
David Rientjes 2013-07-03 15:01:23 -07:00 committed by Linus Torvalds
parent 541c237c09
commit ffbdccf5e1
2 changed files with 11 additions and 9 deletions
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9
include/linux/memcontrol.h
View File

@ -77,7 +77,8 @@ extern void mem_cgroup_uncharge_cache_page(struct page *page);
bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
struct mem_cgroup *memcg);
int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg);
bool task_in_mem_cgroup(struct task_struct *task,
const struct mem_cgroup *memcg);
extern struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);
extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
@ -273,10 +274,10 @@ static inline bool mm_match_cgroup(struct mm_struct *mm,
return true;
}
static inline int task_in_mem_cgroup(struct task_struct *task,
const struct mem_cgroup *memcg)
static inline bool task_in_mem_cgroup(struct task_struct *task,
const struct mem_cgroup *memcg)
{
return 1;
return true;
}
static inline struct cgroup_subsys_state

11
mm/memcontrol.c
View File

@ -1448,11 +1448,12 @@ static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
return ret;
}
int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg)
bool task_in_mem_cgroup(struct task_struct *task,
const struct mem_cgroup *memcg)
{
int ret;
struct mem_cgroup *curr = NULL;
struct task_struct *p;
bool ret;
p = find_lock_task_mm(task);
if (p) {
@ -1464,14 +1465,14 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg)
* killer still needs to detect if they have already been oom
* killed to prevent needlessly killing additional tasks.
*/
task_lock(task);
rcu_read_lock();
curr = mem_cgroup_from_task(task);
if (curr)
css_get(&curr->css);
task_unlock(task);
rcu_read_unlock();
}
if (!curr)
return 0;
return false;
/*
* We should check use_hierarchy of "memcg" not "curr". Because checking
* use_hierarchy of "curr" here make this function true if hierarchy is