From: Kirill Tkhai <tkhai@ya.ru>
To: Johannes Weiner <hannes@cmpxchg.org>, Yang Shi <shy828301@gmail.com>
Cc: "guro@fb.com" <guro@fb.com>,
"ktkhai@virtuozzo.com" <ktkhai@virtuozzo.com>,
"shakeelb@google.com" <shakeelb@google.com>,
"david@fromorbit.com" <david@fromorbit.com>,
"mhocko@suse.com" <mhocko@suse.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-kernel@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 15:58:06 +0300 [thread overview]
Message-ID: <1874151608036985@mail.yandex.ru> (raw)
In-Reply-To: <20201215123802.GA379720@cmpxchg.org>
15.12.2020, 15:40, "Johannes Weiner" <hannes@cmpxchg.org>:
> 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.
Can you read my emails from ktkhai@virtuozzo.com? I've already answered
on this question here: https://lkml.org/lkml/2020/12/10/726
Check your spam folder, and add my address to allow-list if so.
next prev parent reply other threads:[~2020-12-15 13:07 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
2020-12-15 12:58 ` Kirill Tkhai [this message]
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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