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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-91c10c0bd4csm51371086d6.30.2026.10.22.07.11.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Oct 2026 07:11:51 -0700 (PDT) Date: Thu, 22 Oct 2026 10:11:49 -0400 From: Gregory Price To: Li Zhe Cc: akpm@linux-foundation.org, david@kernel.org, ziy@nvidia.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, ying.huang@linux.alibaba.com, ljs@kernel.org, mhocko@suse.com, muchun.song@linux.dev, roman.gushchin@linux.dev, shakeel.butt@linux.dev, weixugc@google.com, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC 0/2] mm: add source selectors to memory.reclaim Message-ID: References: <20261019141401.11927-1-lizhe.67@bytedance.com> <30457046-a662-4ff7-a6a8-100398d7a806@bytedance.com> <179264138036.2549665.17429111144570830454.b4-reply@b4> <9b715272-3ed9-42da-a6ae-467e8ae00c0b@bytedance.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9b715272-3ed9-42da-a6ae-467e8ae00c0b@bytedance.com> On Thu, Oct 22, 2026 at 05:43:49PM +0800, Li Zhe wrote: > On 10/22/26 11:56 AM, Gregory Price (Meta) wrote: > > So userspace cannot rely on one write to memory.reclaim to produce a > final per-node distribution. The intended usage is a feedback loop: the > controller observes the memcg's resident distribution, chooses the source > nodes it wants to relieve, applies source-scoped reclaim pressure, > observes the new distribution, and iterates. > I think the critical question is what CAN userspace rely on? We can make a bunch of feedback loop interfaces, but there's no guarantee they'll actually be useful. > > > > At the very least i think you need to add details in your cover that > > demonstrates the process of doing something like per-node resident > > ratios, and show that it works as you intend. > > Agreed. I will update the cover letter to make this model clearer. I > will also make clear that source=nodes is not a final net per-node > footprint guarantee and does not change memory.reclaim completion > accounting. > To be clear, I think not just making it clearer, but if you can show some tests that demonstrate the reliable behavior of the interface extension under different scenarios - that would be compelling. ~Gregory