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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-53607e1b801sm9569991cf.21.2026.10.14.06.30.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Oct 2026 06:30:59 -0700 (PDT) Date: Wed, 14 Oct 2026 09:30:57 -0400 From: Gregory Price To: Li Zhe Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, joshua.hahnjy@gmail.com, ziy@nvidia.com, mingo@redhat.com, peterz@infradead.org, mgorman@suse.de, riel@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, vschneid@redhat.com, kprateek.nayak@amd.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 6/6] sched/numa: ignore preferred nodes without normal balancing Message-ID: References: <20261014094347.99157-1-lizhe.67@bytedance.com> <20261014094347.99157-7-lizhe.67@bytedance.com> Precedence: bulk X-Mailing-List: linux-doc@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: <20261014094347.99157-7-lizhe.67@bytedance.com> On Wed, Oct 14, 2026 at 05:43:47PM +0800, Li Zhe wrote: > numa_preferred_nid is normal AutoNUMA task-placement state. > Memory-tiering-only mode uses NUMA hint faults to drive page promotion, > not CPU placement. > > Even after tiering-only faults stop updating normal placement statistics, > a task can still have a preferred NUMA node from earlier normal balancing > or from previously polluted state. Several scheduler paths consume that > stale state when the NUMA balancing static key is enabled, including > explicit NUMA task migration, sched-cache preferred LLC and scan CPU mask > selection, load-balance locality checks, fbq classification, and wakeup > group selection. > > Add a small helper for normal NUMA placement being enabled and use it to > ignore numa_preferred_nid when NUMA_BALANCING_NORMAL is disabled. Keep > the preferred-node migration retry timestamp update before the normal-mode > check so accepted non-normal sysctl states do not leave stale retry state > behind. > > Keep the rq nr_numa_running and nr_preferred_running accounting unchanged > so runtime mode changes do not make enqueue/dequeue accounting asymmetric; > the load balancer simply stops consuming those counters while normal > balancing is off. > > This does not clear numa_preferred_nid and does not change memory-tiering > promotion decisions. > Same feedback - need to present user-facing performance changes to show the impact of this change. Sashiko also has some correctness feedback. ~Gregory