From: Johannes Weiner <hannes@cmpxchg.org>
To: Yang Shi <shy828301@gmail.com>
Cc: guro@fb.com, ktkhai@virtuozzo.com, shakeelb@google.com,
david@fromorbit.com, mhocko@suse.com, akpm@linux-foundation.org,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [v2 PATCH 3/9] mm: vmscan: guarantee shrinker_slab_memcg() sees valid shrinker_maps for online memcg
Date: Tue, 15 Dec 2020 13:38:02 +0100 [thread overview]
Message-ID: <20201215123802.GA379720@cmpxchg.org> (raw)
In-Reply-To: <20201214223722.232537-4-shy828301@gmail.com>
On Mon, Dec 14, 2020 at 02:37:16PM -0800, Yang Shi wrote:
> The shrink_slab_memcg() races with mem_cgroup_css_online(). A visibility of CSS_ONLINE flag
> in shrink_slab_memcg()->mem_cgroup_online() does not guarantee that we will see
> memcg->nodeinfo[nid]->shrinker_maps != NULL. This may occur because of processor reordering
> on !x86.
>
> This seems like the below case:
>
> CPU A CPU B
> store shrinker_map load CSS_ONLINE
> store CSS_ONLINE load shrinker_map
>
> So the memory ordering could be guaranteed by smp_wmb()/smp_rmb() pair.
>
> The memory barriers pair will guarantee the ordering between shrinker_deferred and CSS_ONLINE
> for the following patches as well.
>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
As per previous feedback, please move the misplaced shrinker
allocation callback from .css_online to .css_alloc. This will get you
the necessary ordering guarantees from the cgroup core code.
Thanks
next prev parent reply other threads:[~2020-12-15 12:41 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-14 22:37 [RFC v2 PATCH 0/9] Make shrinker's nr_deferred memcg aware Yang Shi
2020-12-14 22:37 ` [v2 PATCH 1/9] mm: vmscan: use nid from shrink_control for tracepoint Yang Shi
2020-12-14 22:37 ` [v2 PATCH 2/9] mm: memcontrol: use shrinker_rwsem to protect shrinker_maps allocation Yang Shi
2020-12-15 2:09 ` Dave Chinner
2020-12-15 13:53 ` Johannes Weiner
2020-12-15 21:59 ` Dave Chinner
2020-12-16 13:17 ` Kirill Tkhai
2020-12-16 19:12 ` Johannes Weiner
2020-12-16 21:56 ` Yang Shi
2020-12-16 19:39 ` Roman Gushchin
2020-12-15 14:07 ` Johannes Weiner
2020-12-15 20:32 ` Yang Shi
2020-12-14 22:37 ` [v2 PATCH 3/9] mm: vmscan: guarantee shrinker_slab_memcg() sees valid shrinker_maps for online memcg Yang Shi
2020-12-15 2:04 ` Dave Chinner
2020-12-15 12:38 ` Johannes Weiner [this message]
2020-12-15 12:58 ` Kirill Tkhai
2020-12-15 16:45 ` Johannes Weiner
2020-12-15 17:14 ` Johannes Weiner
2020-12-15 20:31 ` Yang Shi
2020-12-28 20:03 ` Yang Shi
2020-12-14 22:37 ` [v2 PATCH 4/9] mm: vmscan: use a new flag to indicate shrinker is registered Yang Shi
2020-12-14 22:37 ` [v2 PATCH 5/9] mm: memcontrol: add per memcg shrinker nr_deferred Yang Shi
2020-12-15 2:22 ` Dave Chinner
2020-12-15 14:45 ` Johannes Weiner
2020-12-15 21:57 ` Yang Shi
2020-12-14 22:37 ` [v2 PATCH 6/9] mm: vmscan: use per memcg nr_deferred of shrinker Yang Shi
2020-12-15 2:46 ` Dave Chinner
2020-12-15 22:27 ` Yang Shi
2020-12-15 23:48 ` Dave Chinner
2020-12-14 22:37 ` [v2 PATCH 7/9] mm: vmscan: don't need allocate shrinker->nr_deferred for memcg aware shrinkers Yang Shi
2020-12-15 3:05 ` Dave Chinner
2020-12-15 23:07 ` Yang Shi
2020-12-18 0:56 ` Yang Shi
2020-12-18 1:09 ` Dave Chinner
2020-12-14 22:37 ` [v2 PATCH 8/9] mm: memcontrol: reparent nr_deferred when memcg offline Yang Shi
2020-12-15 3:07 ` Dave Chinner
2020-12-15 23:10 ` Yang Shi
2020-12-14 22:37 ` [v2 PATCH 9/9] mm: vmscan: shrink deferred objects proportional to priority Yang Shi
2020-12-15 3:23 ` Dave Chinner
2020-12-15 23:59 ` Yang Shi
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