linux/Documentation/admin-guide/cgroup-v1
Sebastian Andrzej Siewior 2343e88d23 mm/memcg: disable threshold event handlers on PREEMPT_RT
During the integration of PREEMPT_RT support, the code flow around
memcg_check_events() resulted in `twisted code'.  Moving the code around
and avoiding then would then lead to an additional local-irq-save
section within memcg_check_events().  While looking better, it adds a
local-irq-save section to code flow which is usually within an
local-irq-off block on non-PREEMPT_RT configurations.

The threshold event handler is a deprecated memcg v1 feature.  Instead
of trying to get it to work under PREEMPT_RT just disable it.  There
should be no users on PREEMPT_RT.  From that perspective it makes even
less sense to get it to work under PREEMPT_RT while having zero users.

Make memory.soft_limit_in_bytes and cgroup.event_control return
-EOPNOTSUPP on PREEMPT_RT.  Make an empty memcg_check_events() and
memcg_write_event_control() which return only -EOPNOTSUPP on PREEMPT_RT.
Document that the two knobs are disabled on PREEMPT_RT.

Link: https://lkml.kernel.org/r/20220226204144.1008339-3-bigeasy@linutronix.de
Suggested-by: Michal Hocko <mhocko@kernel.org>
Suggested-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-03-22 15:57:02 -07:00
..
blkio-controller.rst docs/cgroup-v1/blkio: update for 5.x kernels 2021-06-16 11:32:03 -06:00
cgroups.rst
cpuacct.rst
cpusets.rst mm/doc: editorial pass on page migration 2020-09-09 11:39:46 -06:00
devices.rst
freezer-subsystem.rst
hugetlb.rst hugetlb: add hugetlb.*.numa_stat file 2022-01-15 16:30:29 +02:00
index.rst cgroup: Miscellaneous cgroup documentation. 2021-04-04 13:34:46 -04:00
memcg_test.rst mm/lru: revise the comments of lru_lock 2020-12-15 14:48:04 -08:00
memory.rst mm/memcg: disable threshold event handlers on PREEMPT_RT 2022-03-22 15:57:02 -07:00
misc.rst cgroup: Miscellaneous cgroup documentation. 2021-04-04 13:34:46 -04:00
net_cls.rst
net_prio.rst
pids.rst
rdma.rst Documentation/admin-guide: cgroup-v1/rdma: drop doubled word 2020-07-05 14:01:48 -06:00