From: Valentin Schneider <vschneid@redhat.com>
To: Michal Hocko <mhocko@suse.com>
Cc: "Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
"Andrew Morton" <akpm@linux-foundation.org>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Michal Koutný" <mkoutny@suse.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Vladimir Davydov" <vdavydov.dev@gmail.com>,
"Waiman Long" <longman@redhat.com>,
"Roman Gushchin" <guro@fb.com>,
"Shakeel Butt" <shakeelb@google.com>
Subject: Re: [PATCH v5 2/6] mm/memcg: Disable threshold event handlers on PREEMPT_RT
Date: Thu, 02 Mar 2023 19:52:11 +0000 [thread overview]
Message-ID: <xhsmhmt4vnd78.mognet@vschneid.remote.csb> (raw)
In-Reply-To: <xhsmhv8jjnrwu.mognet@vschneid.remote.csb>
On 02/03/23 14:34, Valentin Schneider wrote:
> On 02/03/23 13:56, Michal Hocko wrote:
>> What I am trying to evaluate here is whether it makes sense to support
>> and maintain a non-trivial code for something that might be working
>> sub-optimally or even not working properly in some corner cases. The
>> price for the maintenance is certainly not free.
>
> That's also what I'm trying to make sense of. Either way this will be
> frankenkernel territory, the cgroupv1 ship has already sailed for upstream
> IMO.
So, if someone ends up in a similar situation and considers kludging those
notifications back in:
Don't.
Have a look at:
memcg_check_events()
`\
mem_cgroup_threshold()
`\
__mem_cgroup_threshold()
`\
eventfd_signal()
Having IRQs off, percpu reads, and the the eventfd signal is a nice recipe
for disaster.
The OOM notification sits outside of that, but any other memcg notification
will cause pain.
next prev parent reply other threads:[~2023-03-02 19:52 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-26 20:41 [PATCH v5 0/6] mm/memcg: Address PREEMPT_RT problems instead of disabling it Sebastian Andrzej Siewior
2022-02-26 20:41 ` [PATCH v5 1/6] mm/memcg: Revert ("mm/memcg: optimize user context object stock access") Sebastian Andrzej Siewior
2022-02-26 20:41 ` [PATCH v5 2/6] mm/memcg: Disable threshold event handlers on PREEMPT_RT Sebastian Andrzej Siewior
2023-03-01 18:23 ` Valentin Schneider
2023-03-02 7:45 ` Michal Hocko
2023-03-02 10:18 ` Valentin Schneider
2023-03-02 11:24 ` Michal Hocko
2023-03-02 12:30 ` Valentin Schneider
2023-03-02 12:56 ` Michal Hocko
2023-03-02 14:34 ` Valentin Schneider
2023-03-02 19:52 ` Valentin Schneider [this message]
2022-02-26 20:41 ` [PATCH v5 3/6] mm/memcg: Protect per-CPU counter by disabling preemption on PREEMPT_RT where needed Sebastian Andrzej Siewior
2022-02-28 8:05 ` Michal Hocko
2022-02-28 11:08 ` Sebastian Andrzej Siewior
2022-02-28 11:23 ` Michal Hocko
2022-02-28 12:35 ` Sebastian Andrzej Siewior
2022-02-26 20:41 ` [PATCH v5 4/6] mm/memcg: Opencode the inner part of obj_cgroup_uncharge_pages() in drain_obj_stock() Sebastian Andrzej Siewior
2022-02-26 20:41 ` [PATCH v5 5/6] mm/memcg: Protect memcg_stock with a local_lock_t Sebastian Andrzej Siewior
2022-02-28 8:06 ` Michal Hocko
2022-02-26 20:41 ` [PATCH v5 6/6] mm/memcg: Disable migration instead of preemption in drain_all_stock() Sebastian Andrzej Siewior
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