On Mon 13-09-21 10:51:37, Vasily Averin wrote: > 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? Why? > It is set inside do_exit only and (I hope) cannot trigger huge vmalloc allocations. Allocations in this code path should be rare but it is not like they are non-existent. This is rather hard to review area spread at many places so if we are deciding to make the existing model simpler (no bypassing) then I would rather have no exceptions unless they are reaaly necessary and document them if they are. -- Michal Hocko SUSE Labs
