[PATCH memcg 2/3] memcg: remove charge forcinig for dying tasks

Vasily Averin
2021-10-20T12:13:46Z

ToDo: should we keep task_is_dying() in mem_cgroup_out_of_memory() ?

Signed-off-by: Vasily Averin <vvs-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
---
mm/memcontrol.c | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6da5020a8656..74a7379dbac1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -239,7 +239,7 @@ enum res_type {
iter != NULL; \
iter = mem_cgroup_iter(NULL, iter, NULL))

-static inline bool should_force_charge(void)
+static inline bool task_is_dying(void)
{
return tsk_is_oom_victim(current) || fatal_signal_pending(current) ||
(current->flags & PF_EXITING);
@@ -1575,7 +1575,7 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
* A few threads which were not waiting at mutex_lock_killable() can
* fail to bail out. Therefore, check again after holding oom_lock.
*/
- ret = should_force_charge() || out_of_memory(&oc);
+ ret = task_is_dying() || out_of_memory(&oc);

unlock:
mutex_unlock(&oom_lock);
@@ -2530,6 +2530,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
struct page_counter *counter;
enum oom_status oom_status;
unsigned long nr_reclaimed;
+ bool passed_oom = false;
bool may_swap = true;
bool drained = false;
unsigned long pflags;
@@ -2564,15 +2565,6 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
if (gfp_mask & __GFP_ATOMIC)
goto force;

- /*
- * Unlike in global OOM situations, memcg is not in a physical
- * memory shortage. Allow dying and OOM-killed tasks to
- * bypass the last charges so that they can exit quickly and
- * free their memory.
- */
- if (unlikely(should_force_charge()))
- goto force;
-
/*
* Prevent unbounded recursion when reclaim operations need to
* allocate memory. This might exceed the limits temporarily,
@@ -2630,8 +2622,9 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
if (gfp_mask & __GFP_RETRY_MAYFAIL)
goto nomem;

- if (fatal_signal_pending(current))
- goto force;
+ /* Avoid endless loop for tasks bypassed by the oom killer */
+ if (passed_oom && task_is_dying())
+ goto nomem;

/*
* keep retrying as long as the memcg oom killer is able to make
@@ -2642,6 +2635,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
get_order(nr_pages * PAGE_SIZE));
switch (oom_status) {
case OOM_SUCCESS:
+ passed_oom = true;
nr_retries = MAX_RECLAIM_RETRIES;
goto retry;
case OOM_FAILED:
--
2.32.0