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[70.44.39.90]) by smtp.gmail.com with ESMTPSA id m21sm8279408qtq.52.2021.01.19.08.58.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Jan 2021 08:58:43 -0800 (PST) Date: Tue, 19 Jan 2021 11:58:42 -0500 From: Johannes Weiner To: Muchun Song Cc: mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: memcontrol: skip propagate percpu vmstat values to current memcg Message-ID: References: <20210119052744.96765-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210119052744.96765-1-songmuchun@bytedance.com> 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 Tue, Jan 19, 2021 at 01:27:44PM +0800, Muchun Song wrote: > The current memcg will be freed soon, so updating it's vmstat and > vmevent values is pointless. Just skip updating it. > > Signed-off-by: Muchun Song Oof, that's pretty subtle! Somebody trying to refactor that code for other purposes may not immediately notice that optimization and add potentially tedious bugs. How much does this save? Cgroup creation and deletion isn't really considered a hot path. It takes global locks and such...