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Wed, 30 Oct 2024 07:45:25 -0700 (PDT) Received: from localhost ([93.115.193.42]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-431bd947b2bsm23699315e9.25.2024.10.30.07.45.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Oct 2024 07:45:24 -0700 (PDT) Date: Wed, 30 Oct 2024 14:45:24 +0000 From: Chris Down To: gutierrez.asier@huawei-partners.com Cc: akpm@linux-foundation.org, david@redhat.com, ryan.roberts@arm.com, baohua@kernel.org, willy@infradead.org, peterx@redhat.com, hannes@cmpxchg.org, hocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stepanov.anatoly@huawei.com, alexander.kozhevnikov@huawei-partners.com, guohanjun@huawei.com, weiyongjun1@huawei.com, wangkefeng.wang@huawei.com, judy.chenhui@huawei.com, yusongping@huawei.com, artem.kuzin@huawei.com, kang.sun@huawei.com Subject: Re: [RFC PATCH 0/3] Cgroup-based THP control Message-ID: References: <20241030083311.965933-1-gutierrez.asier@huawei-partners.com> 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; format=flowed Content-Disposition: inline In-Reply-To: <20241030083311.965933-1-gutierrez.asier@huawei-partners.com> User-Agent: Mutt/2.2.13 (00d56288) (2024-03-09) gutierrez.asier@huawei-partners.com writes: >New memcg files are exposed: memory.thp_enabled and memory.thp_defrag, which >have completely the same format as global THP enabled/defrag. cgroup controls exist because there are things we want to do for an entire class of processes (group OOM, resource control, etc). Enabling or disabling some specific setting is generally not one of them, hence why we got rid of things like per-cgroup vm.swappiness. We know that these controls do not compose well and have caused a lot of pain in the past. So my immediate reaction is a nack on the general concept, unless there's some absolutely compelling case here. I talked a little at Kernel Recipes last year about moving away from sysctl and other global interfaces and making things more granular. Don't get me wrong, I think that is a good thing (although, of course, a very large undertaking) -- but it is a mistake to overload the amount of controls we expose as part of the cgroup interface. I am up for thinking overall about how we can improve the state of global tunables to make them more granular overall, but this can't set a precedent as the way to do it.