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

[Shakeel Butt <shakeel.butt@linux.dev>]

On Wed, Aug 14, 2024 at 02:00:03PM GMT, T.J. Mercier wrote:
> 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?

Ah, thanks for catching that. I compile tested the old version before
moving text around. Anyways, will resend.

> 
> >                 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
> >
> >