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Mercier" Date: Wed, 14 Aug 2024 15:58:18 -0700 Message-ID: Subject: Re: [PATCH v2 4/4] memcg: initiate deprecation of pressure_level To: Shakeel Butt Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Meta kernel team , cgroups@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: rbnf3jtf1o1g3u9mjtami8hnq5bjpctm X-Rspam-User: X-Rspamd-Queue-Id: F40F7140017 X-Rspamd-Server: rspam02 X-HE-Tag: 1723676310-280195 X-HE-Meta: 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 G0WeA0lR RB/MZmFL+Au8z6Sx7J3hXGys01BItc/iBbyzwOPFJQSrF1pRrwxDAVHblAU8nKYzEYn1OZIX6Si6uDAxwj7Sccf4Uko1ynHTZ/ryaEbto0qFCmSqqE2v0siDntvKqvQIwevNut5I0JpVEwEk7RpdwKzZBaZ8ZCCfR03z72CrVOrPQu10eW6zz0FLZw5od97Fs8lNm30fqqyUlqv1F6b0oDL8b3HJjHzK2lZbDXT2O3xJaOTTS5Sm/XGDazl+v1iTzJsznphGh5SRSQ647XxoxZ9QOPKhTojNMFWUEWcJ8bH46L4Y= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 14, 2024 at 3:00=E2=80=AFPM Shakeel Butt wrote: > > The pressure_level in memcg v1 provides memory pressure notifications to > the user space. At the moment it provides notifications for three levels > of memory pressure i.e. low, medium and critical, which are defined > based on internal memory reclaim implementation details. More > specifically the ratio or scanned and reclaimed pages during a memory "ratio of" > reclaim. However this is not robust as there are workloads with mostly > unreclaimable user memory or kernel memory. > > For v2, the users can use PSI for memory pressure status of the system > or the cgroup. Let's start the deprecation process for pressure_level > and add warnings to gather the info on how the current users are using > this interface and how they can be used to PSI. > > Signed-off-by: Shakeel Butt Reviewed-by: T.J. Mercier > --- > Changes since v1: > - Fix build (T.J. Mercier) > > Documentation/admin-guide/cgroup-v1/memory.rst | 8 ++++++-- > mm/memcontrol-v1.c | 3 +++ > 2 files changed, 9 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentati= on/admin-guide/cgroup-v1/memory.rst > index 0042206414c8..270501db9f4e 100644 > --- a/Documentation/admin-guide/cgroup-v1/memory.rst > +++ b/Documentation/admin-guide/cgroup-v1/memory.rst > @@ -86,6 +86,8 @@ Brief summary of control files. > used. > memory.force_empty trigger forced page reclaim > memory.pressure_level set memory pressure notifications > + This knob is deprecated and shouldn= 't be > + used. > memory.swappiness set/show swappiness parameter of vms= can > (See sysctl's vm.swappiness) > memory.move_charge_at_immigrate set/show controls of moving charges > @@ -898,8 +900,10 @@ At reading, current status of OOM is shown. > The number of processes belonging to this cgroup killed by any > kind of OOM killer. > > -11. Memory Pressure > -=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > +11. Memory Pressure (DEPRECATED) > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D > + > +THIS IS DEPRECATED! > > The pressure level notifications can be used to monitor the memory > allocation cost; based on the pressure, applications can implement > diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c > index 334a02597d9a..52aecdae2c28 100644 > --- a/mm/memcontrol-v1.c > +++ b/mm/memcontrol-v1.c > @@ -1913,6 +1913,9 @@ static ssize_t memcg_write_event_control(struct ker= nfs_open_file *of, > event->register_event =3D mem_cgroup_oom_register_event; > event->unregister_event =3D mem_cgroup_oom_unregister_eve= nt; > } else if (!strcmp(name, "memory.pressure_level")) { > + pr_warn_once("pressure_level is deprecated and will be re= moved. " > + "Please report your usecase to linux-mm-@kva= ck.org " > + "if you depend on this functionality. \n"); > event->register_event =3D vmpressure_register_event; > event->unregister_event =3D vmpressure_unregister_event; > } else if (!strcmp(name, "memory.memsw.usage_in_bytes")) { > -- > 2.43.5 >