[PATCH v2] mm: fix oom_kill event handling

Roman Gushchin
2018-05-08T12:46:37Z

Commit e27be240df53 ("mm: memcg: make sure memory.events is
uptodate when waking pollers") converted most of memcg event
counters to per-memcg atomics, which made them less confusing
for a user. The "oom_kill" counter remained untouched, so now
it behaves differently than other counters (including "oom").
This adds nothing but confusion.

Let's fix this by adding the MEMCG_OOM_KILL event, and follow
the MEMCG_OOM approach. This also removes a hack from
count_memcg_event_mm(), introduced earlier specially for the
OOM_KILL counter.

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: linux-kernel@vger.kernel.org
Cc: cgroups@vger.kernel.org
Cc: linux-mm@kvack.org
---
include/linux/memcontrol.h | 26 ++++++++++++++++++++++----
mm/memcontrol.c | 6 ++++--
mm/oom_kill.c | 2 +-
3 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 6cbea2f25a87..794475db7368 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -54,6 +54,7 @@ enum memcg_memory_event {
MEMCG_HIGH,
MEMCG_MAX,
MEMCG_OOM,
+ MEMCG_OOM_KILL,
MEMCG_SWAP_MAX,
MEMCG_SWAP_FAIL,
MEMCG_NR_MEMORY_EVENTS,
@@ -721,11 +722,8 @@ static inline void count_memcg_event_mm(struct mm_struct *mm,

rcu_read_lock();
memcg = rcu_dereference(mm->memcg);
- if (likely(memcg)) {
+ if (likely(memcg))
count_memcg_events(memcg, idx, 1);
- if (idx == OOM_KILL)
- cgroup_file_notify(&memcg->events_file);
- }
rcu_read_unlock();
}

@@ -736,6 +734,21 @@ static inline void memcg_memory_event(struct mem_cgroup *memcg,
cgroup_file_notify(&memcg->events_file);
}

+static inline void memcg_memory_event_mm(struct mm_struct *mm,
+ enum memcg_memory_event event)
+{
+ struct mem_cgroup *memcg;
+
+ if (mem_cgroup_disabled())
+ return;
+
+ rcu_read_lock();
+ memcg = rcu_dereference(mm->memcg);
+ if (likely(memcg))
+ memcg_memory_event(memcg, event);
+ rcu_read_unlock();
+}
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
void mem_cgroup_split_huge_fixup(struct page *head);
#endif
@@ -757,6 +770,11 @@ static inline void memcg_memory_event(struct mem_cgroup *memcg,
{
}

+static inline void memcg_memory_event_mm(struct mm_struct *mm,
+ enum memcg_memory_event event)
+{
+}
+
static inline bool mem_cgroup_low(struct mem_cgroup *root,
struct mem_cgroup *memcg)
{
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 10973671e562..38717630305d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3772,7 +3772,8 @@ static int mem_cgroup_oom_control_read(struct seq_file *sf, void *v)

seq_printf(sf, "oom_kill_disable %d\n", memcg->oom_kill_disable);
seq_printf(sf, "under_oom %d\n", (bool)memcg->under_oom);
- seq_printf(sf, "oom_kill %lu\n", memcg_sum_events(memcg, OOM_KILL));
+ seq_printf(sf, "oom_kill %lu\n",
+ atomic_long_read(&memcg->memory_events[MEMCG_OOM_KILL]));
return 0;
}

@@ -5529,7 +5530,8 @@ static int memory_events_show(struct seq_file *m, void *v)
atomic_long_read(&memcg->memory_events[MEMCG_MAX]));
seq_printf(m, "oom %lu\n",
atomic_long_read(&memcg->memory_events[MEMCG_OOM]));
- seq_printf(m, "oom_kill %lu\n", memcg_sum_events(memcg, OOM_KILL));
+ seq_printf(m, "oom_kill %lu\n",
+ atomic_long_read(&memcg->memory_events[MEMCG_OOM_KILL]));

return 0;
}
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 8f7d8dd99e5d..6b74142a1259 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -868,7 +868,7 @@ static void __oom_kill_process(struct task_struct *victim)

/* Raise event before sending signal: task reaper must see this */
count_vm_event(OOM_KILL);
- count_memcg_event_mm(mm, OOM_KILL);
+ memcg_memory_event_mm(mm, MEMCG_OOM_KILL);

/*
* We should send SIGKILL before granting access to memory reserves
--
2.14.3