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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250313054812.2185900-1-shakeel.butt@linux.dev> 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