Re: [v7 5/5] mm, oom: cgroup v2 mount option to disable cgroup-aware OOM killer

[Michal Hocko]

On Wed 06-09-17 18:40:43, Roman Gushchin wrote:
[...]
> >From f6e2339926a07500834d86548f3f116af7335d71 Mon Sep 17 00:00:00 2001
> From: Roman Gushchin <guro@xxxxxx>
> Date: Wed, 6 Sep 2017 17:43:44 +0100
> Subject: [PATCH] mm, oom: first step towards oom_kill_allocating_task
>  deprecation
> 
> The oom_kill_allocating_task sysctl which causes the OOM killer
> to simple kill the allocating task is useless. Killing the random

useless is quite strong ;) I would say dubious.

> task is not the best idea.
> 
> Nobody likes it, and hopefully nobody uses it.
> We want to completely deprecate it at some point.
> 
> To make a first step towards deprecation, let's warn potential
> users about deprecation plans.
> 
> Signed-off-by: Roman Gushchin <guro@xxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx

Other than that
Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
>  kernel/sysctl.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 655686d546cb..9158f1980584 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -220,6 +220,17 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write,
>  
>  #endif
>  
> +static int proc_oom_kill_allocating_tasks(struct ctl_table *table, int write,
> +				   void __user *buffer, size_t *lenp,
> +				   loff_t *ppos)
> +{
> +	pr_warn_once("The oom_kill_allocating_task sysctl will be deprecated.\n"
> +		     "If you're using it, please, report to "
> +		     "linux-mm@xxxxxxxxxxxxxxxxx\n");
> +
> +	return proc_dointvec(table, write, buffer, lenp, ppos);
> +}
> +
>  static struct ctl_table kern_table[];
>  static struct ctl_table vm_table[];
>  static struct ctl_table fs_table[];
> @@ -1235,7 +1246,7 @@ static struct ctl_table vm_table[] = {
>  		.data		= &sysctl_oom_kill_allocating_task,
>  		.maxlen		= sizeof(sysctl_oom_kill_allocating_task),
>  		.mode		= 0644,
> -		.proc_handler	= proc_dointvec,
> +		.proc_handler	= proc_oom_kill_allocating_tasks,
>  	},
>  	{
>  		.procname	= "oom_dump_tasks",
> -- 
> 2.13.5

-- 
Michal Hocko
SUSE Labs