From: Johannes Weiner <hannes@cmpxchg.org>
To: Muchun Song <songmuchun@bytedance.com>
Cc: guro@fb.com, mhocko@kernel.org, akpm@linux-foundation.org,
shakeelb@google.com, vdavydov.dev@gmail.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
duanxiongchun@bytedance.com, fam.zheng@bytedance.com,
bsingharora@gmail.com, shy828301@gmail.com,
alex.shi@linux.alibaba.com
Subject: Re: [RFC PATCH v2 05/18] mm: memcontrol: simplify the logic of objcg pinning memcg
Date: Fri, 9 Apr 2021 12:27:27 -0400 [thread overview]
Message-ID: <YHCAb1cZFuqLiy6r@cmpxchg.org> (raw)
In-Reply-To: <20210409122959.82264-6-songmuchun@bytedance.com>
On Fri, Apr 09, 2021 at 08:29:46PM +0800, Muchun Song wrote:
> The obj_cgroup_release() and memcg_reparent_objcgs() are serialized by
> the css_set_lock. We do not need to care about objcg->memcg being
> released in the process of obj_cgroup_release(). So there is no need
> to pin memcg before releasing objcg. Remove those pinning logic to
> simplfy the code.
Hm yeah, it's not clear to me why inherited objcgs pinned the memcg in
the first place, since they are reparented during memcg deletion and
therefor have no actual impact on the memcg's lifetime.
> There are only two places that modifies the objcg->memcg. One is the
> initialization to objcg->memcg in the memcg_online_kmem(), another
> is objcgs reparenting in the memcg_reparent_objcgs(). It is also
> impossible for the two to run in parallel. So xchg() is unnecessary
> and it is enough to use WRITE_ONCE().
Good catch.
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Looks like a nice cleanup / simplification:
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
next prev parent reply other threads:[~2021-04-09 16:27 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-09 12:29 [RFC PATCH v2 00/18] Use obj_cgroup APIs to charge the LRU pages Muchun Song
2021-04-09 12:29 ` [RFC PATCH v2 01/18] mm: memcontrol: fix page charging in page replacement Muchun Song
2021-04-10 17:44 ` Shakeel Butt
2021-04-09 12:29 ` [RFC PATCH v2 02/18] mm: memcontrol: bail out early when !mm in get_mem_cgroup_from_mm Muchun Song
2021-04-10 17:47 ` Shakeel Butt
2021-04-09 12:29 ` [RFC PATCH v2 05/18] mm: memcontrol: simplify the logic of objcg pinning memcg Muchun Song
2021-04-09 16:27 ` Johannes Weiner [this message]
2021-04-09 12:29 ` [RFC PATCH v2 07/18] mm: memcontrol: introduce compact_lock_page_lruvec_irqsave Muchun Song
2021-04-09 12:29 ` [RFC PATCH v2 09/18] mm: vmscan: remove noinline_for_stack Muchun Song
2021-04-09 18:31 ` Johannes Weiner
2021-04-10 4:33 ` [External] " Muchun Song
2021-04-10 17:48 ` Shakeel Butt
2021-04-10 0:49 ` Roman Gushchin
2021-04-09 12:29 ` [RFC PATCH v2 10/18] mm: vmscan: rework move_pages_to_lru() Muchun Song
2021-04-09 12:29 ` [RFC PATCH v2 12/18] mm: thp: make deferred split queue lock safe when the LRU pages reparented Muchun Song
2021-04-09 12:29 ` [RFC PATCH v2 14/18] mm: memcontrol: introduce memcg_reparent_ops Muchun Song
[not found] ` <20210409122959.82264-5-songmuchun@bytedance.com>
2021-04-09 16:00 ` [RFC PATCH v2 04/18] mm: memcontrol: simplify lruvec_holds_page_lru_lock Johannes Weiner
2021-04-11 5:37 ` [External] " Muchun Song
[not found] ` <20210409122959.82264-7-songmuchun@bytedance.com>
2021-04-09 16:56 ` [RFC PATCH v2 06/18] mm: memcontrol: move the objcg infrastructure out of CONFIG_MEMCG_KMEM Johannes Weiner
2021-04-11 6:24 ` [External] " Muchun Song
2021-04-10 1:29 ` [RFC PATCH v2 00/18] Use obj_cgroup APIs to charge the LRU pages Roman Gushchin
2021-04-12 17:14 ` Johannes Weiner
2021-04-12 17:45 ` Roman Gushchin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YHCAb1cZFuqLiy6r@cmpxchg.org \
--to=hannes@cmpxchg.org \
--cc=akpm@linux-foundation.org \
--cc=alex.shi@linux.alibaba.com \
--cc=bsingharora@gmail.com \
--cc=duanxiongchun@bytedance.com \
--cc=fam.zheng@bytedance.com \
--cc=guro@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=shakeelb@google.com \
--cc=shy828301@gmail.com \
--cc=songmuchun@bytedance.com \
--cc=vdavydov.dev@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).