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memcg: initiate deprecation of pressure_level

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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 <shakeel.butt@linux.dev>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Shakeel Butt 2024-08-14 15:00:21 -07:00 committed by Andrew Morton
parent 6df4ad7047
commit 340afb8027
2 changed files with 9 additions and 2 deletions
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8
Documentation/admin-guide/cgroup-v1/memory.rst
View File

@ -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

3
mm/memcontrol-v1.c
View File

@ -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")) {