ToDo: should we keep task_is_dying() in mem_cgroup_out_of_memory() ?
Signed-off-by: Vasily Averin <[email protected]>
---
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
On Wed 20-10-21 15:13:46, Vasily Averin wrote:
> ToDo: should we keep task_is_dying() in mem_cgroup_out_of_memory() ?
>
> Signed-off-by: Vasily Averin <[email protected]>
> ---
> 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);
Why are you keeping the task_is_dying check here? IIRC I have already
pointed out that out_of_memory already has some means to do a bypass
when needed.
--
Michal Hocko
SUSE Labs
On 20.10.2021 15:41, Michal Hocko wrote:
> On Wed 20-10-21 15:13:46, Vasily Averin wrote:
>> ToDo: should we keep task_is_dying() in mem_cgroup_out_of_memory() ?
>>
>> Signed-off-by: Vasily Averin <[email protected]>
>> ---
>> 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);
>
> Why are you keeping the task_is_dying check here? IIRC I have already
> pointed out that out_of_memory already has some means to do a bypass
> when needed.
It was a misunderstanding.
I've been waiting for your final decision.
I have no good arguments "pro" or strong objection "contra".
However, I prefer to keep task_is_dying() so as not to touch other tasks unnecessarily.
I can't justify why its removal is necessary,
but on the other hand, it shouldn't break anything.
I can drop it if you think it's necessary.
Thank you,
Vasily Averin
On Wed 20-10-21 17:21:33, Vasily Averin wrote:
> On 20.10.2021 15:41, Michal Hocko wrote:
> > On Wed 20-10-21 15:13:46, Vasily Averin wrote:
> >> ToDo: should we keep task_is_dying() in mem_cgroup_out_of_memory() ?
> >>
> >> Signed-off-by: Vasily Averin <[email protected]>
> >> ---
> >> 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);
> >
> > Why are you keeping the task_is_dying check here? IIRC I have already
> > pointed out that out_of_memory already has some means to do a bypass
> > when needed.
>
> It was a misunderstanding.
Sorry if I made you confused.
> I've been waiting for your final decision.
>
> I have no good arguments "pro" or strong objection "contra".
> However, I prefer to keep task_is_dying() so as not to touch other tasks unnecessarily.
One argument for removing it from here is the maintainability. Now you
have a memcg specific check which is not in sync with the oom. E.g.
out_of_memory does task_will_free_mem as the very first thing. You are
also automatically excluding oom killer for cases where that might make
a sense.
--
Michal Hocko
SUSE Labs
On 2021/10/20 23:57, Michal Hocko wrote:
> One argument for removing it from here is the maintainability. Now you
> have a memcg specific check which is not in sync with the oom. E.g.
> out_of_memory does task_will_free_mem as the very first thing. You are
> also automatically excluding oom killer for cases where that might make
> a sense.
What makes it possible to remove this check?
This check was added because task_will_free_mem() in out_of_memory() does NOT work.
See commit 7775face207922ea ("memcg: killed threads should not invoke memcg OOM killer").
On Thu 21-10-21 00:20:02, Tetsuo Handa wrote:
> On 2021/10/20 23:57, Michal Hocko wrote:
> > One argument for removing it from here is the maintainability. Now you
> > have a memcg specific check which is not in sync with the oom. E.g.
> > out_of_memory does task_will_free_mem as the very first thing. You are
> > also automatically excluding oom killer for cases where that might make
> > a sense.
>
> What makes it possible to remove this check?
> This check was added because task_will_free_mem() in out_of_memory() does NOT work.
> See commit 7775face207922ea ("memcg: killed threads should not invoke memcg OOM killer").
You are right. I've forgot about this and should have checked git blame.
Thanks for bringing this up!
--
Michal Hocko
SUSE Labs