Re: [PATCH] mm/memcontrol: Disable on PREEMPT_RT
From: Waiman Long <hidden>
Date: 2021-12-07 16:00:43
Also in:
linux-mm
On 12/7/21 10:52, Sebastian Andrzej Siewior wrote:
From: Thomas Gleixner <redacted>
MEMCG has a few constructs which are not compatible with PREEMPT_RT's
requirements. This includes:
- relying on disabled interrupts from spin_lock_irqsave() locking for
something not related to lock itself (like the per-CPU counter).
- explicitly disabling interrupts and acquiring a spinlock_t based lock
like in memcg_check_events() -> eventfd_signal().
- explicitly disabling interrupts and freeing memory like in
drain_obj_stock() -> obj_cgroup_put() -> obj_cgroup_release() ->
percpu_ref_exit().
Commit 559271146efc ("mm/memcg: optimize user context object stock
access") continued to optimize for the CPU local access which
complicates the PREEMPT_RT locking requirements further.
Disable MEMCG on PREEMPT_RT until the whole situation can be evaluated
again.
Disabling MEMCG for PREEMPT_RT may be too drastic a step to take. For
commit 559271146efc ("mm/memcg: optimize user context object stock
access"), I can modify it to disable the optimization for PREEMPT_RT.
Cheers,
Longman
quoted hunk ↗ jump to hunk
[ bigeasy: commit description. ] Signed-off-by: Thomas Gleixner <redacted> Signed-off-by: Sebastian Andrzej Siewior <redacted> --- init/Kconfig | 1 + 1 file changed, 1 insertion(+)--- a/init/Kconfig +++ b/init/Kconfig@@ -943,6 +943,7 @@ config PAGE_COUNTER config MEMCG bool "Memory controller" + depends on !PREEMPT_RT select PAGE_COUNTER select EVENTFD help