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

[Michal Hocko <mhocko@suse.com>]

On Thu 04-09-25 21:44:31, Jinjiang Tu wrote:
> out_of_memory() selects tasks without considering mempolicy. Assuming a
> cpu-less NUMA Node, ordinary process that don't set mempolicy don't
> allocate memory from this cpu-less Node, unless other NUMA Nodes are below
> low watermark. If a task binds to this cpu-less Node and triggers OOM, many
> tasks may be killed wrongly that don't occupy memory from this Node.

I can see how a miconfigured task that binds _only_ to memoryless nodes
should be killed but this is not what the patch does, right?  Could you
tell us more about the specific situation? 

> To fix it, only kill current if oc->nodemask are all nodes without any cpu.
> 
> Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
> ---
>  mm/oom_kill.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 25923cfec9c6..8ae4b2ecfe12 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -1100,6 +1100,20 @@ int unregister_oom_notifier(struct notifier_block *nb)
>  }
>  EXPORT_SYMBOL_GPL(unregister_oom_notifier);
>  
> +static bool should_oom_kill_allocating_task(struct oom_control *oc)
> +{
> +	if (sysctl_oom_kill_allocating_task)
> +		return true;
> +
> +	if (!oc->nodemask)
> +		return false;
> +
> +	if (nodes_intersects(*oc->nodemask, node_states[N_CPU]))
> +		return false;
> +
> +	return true;
> +}
> +
>  /**
>   * out_of_memory - kill the "best" process when we run out of memory
>   * @oc: pointer to struct oom_control
> @@ -1151,7 +1165,7 @@ bool out_of_memory(struct oom_control *oc)
>  		oc->nodemask = NULL;
>  	check_panic_on_oom(oc);
>  
> -	if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
> +	if (!is_memcg_oom(oc) && should_oom_kill_allocating_task(oc) &&
>  	    current->mm && !oom_unkillable_task(current) &&
>  	    oom_cpuset_eligible(current, oc) &&
>  	    current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
> -- 
> 2.43.0

-- 
Michal Hocko
SUSE Labs