From 340afb8027fab59e88a9993d9418a1ef81d3dc08 Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Wed, 14 Aug 2024 15:00:21 -0700 Subject: [PATCH] memcg: initiate deprecation of pressure_level 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 of scanned and reclaimed pages during a memory 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. Link: https://lkml.kernel.org/r/20240814220021.3208384-5-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Reviewed-by: T.J. Mercier Acked-by: Michal Hocko Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Muchun Song Signed-off-by: Andrew Morton --- 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/Documentation/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 vmscan (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 -=================== +11. Memory Pressure (DEPRECATED) +================================ + +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 3240f930d5f7..b37c0d870816 100644 --- a/mm/memcontrol-v1.c +++ b/mm/memcontrol-v1.c @@ -2000,6 +2000,9 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of, event->register_event = mem_cgroup_oom_register_event; event->unregister_event = mem_cgroup_oom_unregister_event; } else if (!strcmp(name, "memory.pressure_level")) { + pr_warn_once("pressure_level is deprecated and will be removed. " + "Please report your usecase to linux-mm-@kvack.org " + "if you depend on this functionality. \n"); event->register_event = vmpressure_register_event; event->unregister_event = vmpressure_unregister_event; } else if (!strcmp(name, "memory.memsw.usage_in_bytes")) {