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Wed, 01 Jun 2022 21:14:12 -0700 (PDT) Date: Thu, 2 Jun 2022 12:14:06 +0800 From: Muchun Song To: Michal =?iso-8859-1?Q?Koutn=FD?= Cc: hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeelb@google.com, akpm@linux-foundation.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, duanxiongchun@bytedance.com, longman@redhat.com Subject: Re: [PATCH v5 09/11] mm: memcontrol: use obj_cgroup APIs to charge the LRU pages Message-ID: References: <20220530074919.46352-1-songmuchun@bytedance.com> <20220530074919.46352-10-songmuchun@bytedance.com> <20220601173438.GC2434@blackbody.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220601173438.GC2434@blackbody.suse.cz> X-Stat-Signature: qdx6cdydq3b1keeoprkp1w418osdgr8t X-Rspam-User: Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b="DZpIXcD/"; dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf24.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.210.180 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 6FE7018005F X-HE-Tag: 1654143238-946299 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jun 01, 2022 at 07:34:38PM +0200, Michal Koutný wrote: > Hello Muchun. > > On Mon, May 30, 2022 at 03:49:17PM +0800, Muchun Song wrote: > > +static inline bool obj_cgroup_is_root(struct obj_cgroup *objcg) > > +{ > > + return objcg == root_obj_cgroup; > > +} > > Admittedly, this predicate alone caught my eye, why it did not also > check root_mem_cgroup->objcg_list. > However, deeper look reveals it's purpose is to avoid missing uncharges > of pages that were charged in non-root memcg and later re-associated > upwards after reparenting. Right. > So it's like obj_cgroup_root_origin() (I'm not suggesting a rename, just > illustrating the understanding). > > get_obj_cgroup_from_current() gains some complexity but it still holds > that in root memcg neither kernel objects nor LRU pages are charged. > At the same time, reparented kernel objects or LRU pages are properly > uncharged. > > These parts are > Reviewed-by: Michal Koutný > Thanks Michal. > (I did not look into the locking guarantees with the new API though.) > >