Re: [PATCH 3/4] memcg: initiate deprecation of oom_control

["T.J. Mercier" <tjmercier@google.com>]

On Wed, Aug 14, 2024 at 1:29 PM Shakeel Butt <shakeel.butt@linux.dev> wrote:
>
> The oom_control provides functionality to disable memcg oom-killer,
> notifications on oom-kill and reading the stats regarding oom-kills.
> This interface was mainly introduced to provide functionality for
> userspace oom-killers. However it is not robust enough and only supports
> OOM handling in the page fault path.
>
> For v2, the users can use the combination of memory.events notifications
> and memory.high interface to provide userspace OOM-killing functionality.
> Let's start the deprecation process for v1 and gather the info on how
> the current users are using this interface and work on providing a more
> robust functionality in v2.
>
> Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
> ---
>  Documentation/admin-guide/cgroup-v1/memory.rst | 8 ++++++--
>  mm/memcontrol-v1.c                             | 7 +++++++
>  2 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst
> index afe5e95e9f7b..74cea6712d06 100644
> --- a/Documentation/admin-guide/cgroup-v1/memory.rst
> +++ b/Documentation/admin-guide/cgroup-v1/memory.rst
> @@ -92,6 +92,8 @@ Brief summary of control files.
>                                       This knob is deprecated and shouldn't be
>                                       used.
>   memory.oom_control                 set/show oom controls.
> +                                     This knob is deprecated and shouldn't be
> +                                     used.
>   memory.numa_stat                   show the number of memory usage per numa
>                                      node
>   memory.kmem.limit_in_bytes          Deprecated knob to set and read the kernel
> @@ -846,8 +848,10 @@ It's applicable for root and non-root cgroup.
>
>  .. _cgroup-v1-memory-oom-control:
>
> -10. OOM Control
> -===============
> +10. OOM Control (DEPRECATED)
> +============================
> +
> +THIS IS DEPRECATED!
>
>  memory.oom_control file is for OOM notification and other controls.
>
> diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
> index e0bb54e42011..07343e338e4e 100644
> --- a/mm/memcontrol-v1.c
> +++ b/mm/memcontrol-v1.c
> @@ -1907,6 +1907,9 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
>                 event->register_event = mem_cgroup_usage_register_event;
>                 event->unregister_event = mem_cgroup_usage_unregister_event;
>         } else if (!strcmp(name, "memory.oom_control")) {
> +               pr_warn_once("oom_control is deprecated and will be removed. "
> +                            "Please report your usecase to linux-mm-@kvack.org"
> +                            " if you depend on this functionality. \n";

Missing close paren?

>                 event->register_event = mem_cgroup_oom_register_event;
>                 event->unregister_event = mem_cgroup_oom_unregister_event;
>         } else if (!strcmp(name, "memory.pressure_level")) {
> @@ -2754,6 +2757,10 @@ static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css,
>  {
>         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
>
> +       pr_warn_once("oom_control is deprecated and will be removed. "
> +                    "Please report your usecase to linux-mm-@kvack.org if you "
> +                    "depend on this functionality. \n";
> +

Missing close paren?

>         /* cannot set to root cgroup and only 0 and 1 are allowed */
>         if (mem_cgroup_is_root(memcg) || !((val == 0) || (val == 1)))
>                 return -EINVAL;
> --
> 2.43.5
>
>