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From: "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org>
To: Sebastian Andrzej Siewior
	<bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
	Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Vladimir Davydov
	<vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
	Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: [RFC PATCH 1/3] mm/memcg: Protect per-CPU counter by disabling preemption on PREEMPT_RT
Date: Wed, 5 Jan 2022 15:16:53 +0100	[thread overview]
Message-ID: <20220105141653.GA6464@blackbody.suse.cz> (raw)
In-Reply-To: <20211222114111.2206248-2-bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>

On Wed, Dec 22, 2021 at 12:41:09PM +0100, Sebastian Andrzej Siewior <bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org> wrote:
> The sections with disabled preemption must exclude
> memcg_check_events() so that spinlock_t locks can still be acquired
> (for instance in eventfd_signal()).

The resulting construct in uncharge_batch() raises eybrows. If you can decouple
per-cpu updates from memcg_check_events() on PREEMPT_RT, why not tackle
it the same way on !PREEMPT_RT too (and have just one variant of the
block)?

(Actually, it doesn't seem to me that memcg_check_events() can be
extracted like this from the preempt disabled block since
mem_cgroup_event_ratelimit() relies on similar RMW pattern.
Things would be simpler if PREEMPT_RT didn't allow the threshold event
handlers (akin to Michal Hocko's suggestion of rejecting soft limit).)

Thanks,
Michal

  parent reply	other threads:[~2022-01-05 14:16 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-22 11:41 [RFC PATCH 0/3] mm/memcg: Address PREEMPT_RT problems instead of disabling it Sebastian Andrzej Siewior
     [not found] ` <20211222114111.2206248-1-bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2021-12-22 11:41   ` [RFC PATCH 1/3] mm/memcg: Protect per-CPU counter by disabling preemption on PREEMPT_RT Sebastian Andrzej Siewior
     [not found]     ` <20211222114111.2206248-2-bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2021-12-23  2:31       ` Waiman Long
     [not found]         ` <bdfc9791-4af2-f4fb-9ef5-dab1e2e3ff89-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2021-12-23  7:34           ` Sebastian Andrzej Siewior
     [not found]             ` <YcQme8BPFl7P9T02-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2021-12-23 16:01               ` Waiman Long
2022-01-05 14:16       ` Michal Koutný [this message]
     [not found]         ` <20220105141653.GA6464-9OudH3eul5jcvrawFnH+a6VXKuFTiq87@public.gmane.org>
2022-01-13 13:08           ` Sebastian Andrzej Siewior
     [not found]             ` <YeAkOm0YsAe5jFRb-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2022-01-13 14:48               ` Michal Koutný
     [not found]                 ` <20220113144803.GB28468-9OudH3eul5jcvrawFnH+a6VXKuFTiq87@public.gmane.org>
2022-01-14  9:09                   ` Sebastian Andrzej Siewior
     [not found]                     ` <YeE9zyUokSY9L2ZI-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2022-01-18 18:26                       ` [PATCH] mm/memcg: Do not check v1 event counter when not needed Michal Koutný
     [not found]                         ` <20220118182600.15007-1-mkoutny-IBi9RG/b67k@public.gmane.org>
2022-01-18 19:57                           ` Sebastian Andrzej Siewior
2021-12-22 11:41   ` [RFC PATCH 2/3] mm/memcg: Add a local_lock_t for IRQ and TASK object Sebastian Andrzej Siewior
     [not found]     ` <20211222114111.2206248-3-bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2021-12-23 21:38       ` Waiman Long
     [not found]         ` <4fe30c89-df34-bbdb-a9a1-5519e0363cc5-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2022-01-03 16:34           ` Sebastian Andrzej Siewior
     [not found]             ` <YdMlrFPvb94rzv8Z-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2022-01-03 17:09               ` Waiman Long
2021-12-22 11:41   ` [RFC PATCH 3/3] mm/memcg: Allow the task_obj optimization only on non-PREEMPTIBLE kernels Sebastian Andrzej Siewior
     [not found]     ` <20211222114111.2206248-4-bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2021-12-23 21:48       ` Waiman Long
     [not found]         ` <f6bb93c8-3940-6141-d0e0-50144549a4f5-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2022-01-03 14:44           ` Sebastian Andrzej Siewior
     [not found]             ` <YdML2zaU17clEZgt-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2022-01-03 15:04               ` Waiman Long
     [not found]                 ` <df637005-6c72-a1c6-c6b9-70f81f74884d-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2022-01-05 20:22                   ` Sebastian Andrzej Siewior
     [not found]                     ` <YdX+INO9gQje6d0S-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2022-01-06  3:28                       ` Waiman Long
     [not found]                         ` <29457251-cf4f-4c7d-b36d-c2a0af4da707-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2022-01-13 15:26                           ` Sebastian Andrzej Siewior
2022-01-05 14:59   ` [RFC PATCH 0/3] mm/memcg: Address PREEMPT_RT problems instead of disabling it Michal Koutný
     [not found]     ` <20220105145956.GB6464-9OudH3eul5jcvrawFnH+a6VXKuFTiq87@public.gmane.org>
2022-01-05 15:06       ` Sebastian Andrzej Siewior

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