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SubjectRe: [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks
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On 9/10/21 3:39 PM, Vasily Averin wrote:
> The kernel currently allows dying tasks to exceed the memcg limits.
> The allocation is expected to be the last one and the occupied memory
> will be freed soon.
> This is not always true because it can be part of the huge vmalloc
> allocation. Allowed once, they will repeat over and over again.

> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 389b5766e74f..67195fcfbddf 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2622,15 +2625,6 @@ 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;
> -

Should we keep current behaviour for (current->flags & PF_EXITING) case perhaps?
It is set inside do_exit only and (I hope) cannot trigger huge vmalloc allocations.

Thank you,
Vasily Averin

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