Re: [PATCH] mm/oom_kill: kill current in OOM when binding to cpu-less nodes

[Michal Hocko <mhocko@suse.com>]

On Mon 08-09-25 16:16:38, Jinjiang Tu wrote:
> 
> 在 2025/9/8 15:46, Michal Hocko 写道:
> > On Sat 06-09-25 09:56:16, Jinjiang Tu wrote:
> > > In our use case, movable nodes are in all cpusets, so that movable nodes can be
> > > used by all tasks. Even though we move tasks into cpusets that only allow to allocate
> > > from movable nodes, oom_cpuset_eligible()->cpuset_mems_allowed_intersects() returns true for
> > > all tasks.
> > Right but this is because you allowed _all_ tasks to allocate from those
> > movable nodes so why would that be an unexpected behavior?
> > 
> > > Maybe when oc->nodemask == movable nodes, only select tasks whose mempolicy intersects with oc->nodemask.
> > > Like the following:
> > > 
> > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > > index eb83cff7db8c..e56b6de836a6 100644
> > > --- a/mm/mempolicy.c
> > > +++ b/mm/mempolicy.c
> > > @@ -2328,6 +2328,9 @@ bool mempolicy_in_oom_domain(struct task_struct *tsk,
> > >          if (!mask)
> > >                  return ret;
> > > +       if (!nodes_intersects(*oc->nodemask, node_states[N_CPU]))
> > > +               ret = false;
> > > +
> > Nope, this doesn't really make much sense TBH. I believe you should stop
> > special casing cpuless nodes and look into the actual configuration and
> > check how to make cpuset based OOM tasks selection. Your underlying
> > problem is not about no CPUs assigned to a numa node but an allocation
> > constrain based on movability of allocations so you need to find a
> > solution that is dealing with that constrain.
> 
> Many tasks are in the root cpuset, systemd for example. The root cpuset
> contains all nodes, we couldn't exclude cpu-less nodes.
> 
> If we reply on cpuset based OOM tasks selection, tasks in root cpuset may
> still be selected.

If you start by killing tasks from the cpuset of the currently
allocating task then this shouldn't really happen, right?
-- 
Michal Hocko
SUSE Labs