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Thu, 13 Mar 2025 08:39:14 -0700 (PDT) Date: Thu, 13 Mar 2025 11:39:10 -0400 From: Johannes Weiner To: Shakeel Butt Cc: Andrew Morton , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH] memcg: avoid refill_stock for root memcg Message-ID: <20250313153910.GA1252169@cmpxchg.org> References: <20250313054812.2185900-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250313054812.2185900-1-shakeel.butt@linux.dev> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6D5424000D X-Stat-Signature: 577dtzhwh6bj1o1sypoe51gt3du9agpt X-HE-Tag: 1741880356-928292 X-HE-Meta: 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 LLVIm4rT 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 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: List-Subscribe: List-Unsubscribe: On Wed, Mar 12, 2025 at 10:48:12PM -0700, Shakeel Butt wrote: > We never charge the page counters of root memcg, so there is no need to > put root memcg in the memcg stock. At the moment, refill_stock() can be > called from try_charge_memcg(), obj_cgroup_uncharge_pages() and > mem_cgroup_uncharge_skmem(). > > The try_charge_memcg() and mem_cgroup_uncharge_skmem() are never called > with root memcg, so those are fine. However obj_cgroup_uncharge_pages() > can potentially call refill_stock() with root memcg if the objcg object > has been reparented over to the root memcg. Let's just avoid > refill_stock() from obj_cgroup_uncharge_pages() for root memcg. > > Signed-off-by: Shakeel Butt Acked-by: Johannes Weiner