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Wed, 30 Sep 2026 05:03:55 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F ([2620:10d:c092:500::6:13b8]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a017468b10sm66347925e9.0.2026.09.30.05.03.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Sep 2026 05:03:54 -0700 (PDT) Date: Wed, 30 Sep 2026 08:03:52 -0400 From: Gregory Price To: "David Hildenbrand (Arm)" Cc: Li Zhe , akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, mhocko@suse.com, corbet@lwn.net, skhan@linuxfoundation.org, ziy@nvidia.com, joshua.hahnjy@gmail.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/numa_balancing: allow migrate on protnone reference with MPOL_WEIGHTED_INTERLEAVE policy Message-ID: References: <20260930072617.64665-1-lizhe.67@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 7520A180014 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: rz15kgjfn15x78zuyzfo1atpnugyfd7g X-HE-Tag: 1790769836-964988 X-HE-Meta: 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 92GVBFX0 V+kSY40ENO1bIBWpAQkWQdStBiZ3SrT8H3PMfGqydeTRO/m4pP+GeQsvFReSQs4igTu2RRrIwhMT2y1ghjQZVAV6P/9hM2Kma4RTMhfmHlVICAkKZQkW7rVzedhs9UZEG9wkqs723bFkJL7rU85e8WDbjN/q4mrkpLbCgaKt9lVW5vsxKjz13ralVoEpVOV7vtDOP9/BIt7vXXmVXEOnqnGURPW3vStQckwRdwkou4QlV4S8x4tBPwHuD5kImV8PmhsBuGXKjOMExgU5o2+Gd97lZ3OqldAdHZgVXxO1DIUctto7YR1U/4nj4l2Kv9ft1igFT+lmWHm9P8VgybD/ZD0HrllbagoQlh6i9dhYkEraU6bYgmmf+rRgEdVhYecP8NqI/BQKjaRhrYGDTDWZRnj4J6kBzKZ2/MbIkRpfaFm9Yg3HCi+TJAkHHbXMwqhLbDh6g/UK89CEI9YXrwJMFQkl9cXP5YcF0wXrjvzZW6whogSA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 30, 2026 at 01:26:17PM +0200, David Hildenbrand (Arm) wrote: > > > > Initial placement is only a starting point. Pages initially allocated on > > fast memory are not necessarily the long-term hot pages, and pages > > initially allocated on slower memory may become hot as the workload's hot > > set changes. The policy therefore needs to be able to combine weighted > > initial placement with memory tiering's NUMA fault based hot-page > > promotion. > > Ok, so memory allocation will respect the weights but balancing will ignore > them? That really sounds rather odd to me. > > And I assume that was the reason why we might have disallowed the combination: > it turns a weighted mechanism into an unweighted mechanism. > > So are we really sure these semantics that you would essentially set in stone > here are the semantics we want? (ignoring weights) > Right, but you're requesting this configuration. If you didn't set F_NUMA_BALANCING then you get the existing semantics. In the existing semantics, if we're INTERLEAVE and WEIGHTED_INTERLEAVE we just always say "no tiering for you". But as an opt-in option? I don't quite see the argument for saying interleaved regions (or tasks) to be opted-out if the user asks for it - that just seems like an arbitrary limitation. ~Gregory