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b=KdwNkU7fC6p0Z59UnOOrZ+WsPDyul3+LLEPMes+3vg5gSqGpqOqfqPPBPE9YzyTuF /018svbY8qU6R1mD4AnHJxcclHWaMtJy+gUt2A76XGdAFY6hkgoWizcuorVSRo9+1D /4f17Se+WFFTeKj9FC98wFEHSscQW9SqAfxrjJwcHWugVTm8IYI/5YYq7AE/5cfWbv 4Z+jRp4DQgh6dFQ5zDVau5e4hmGygo8Iux/hs88ZDKQmRQcE5p44zFcRF7xQQPBg2e GiDlK+bxXiK7eJKPt1Qd2iO8UhOqLlY4NyvKoJcKshBL/sdXRZeDiNgzj2O5K5VimK hPCmiNk3Yawuw== Message-ID: <8699eba1-21cd-420e-a992-51a90ba62b71@kernel.org> Date: Thu, 24 Sep 2026 13:45:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/7] mm: support promotion-only NUMA hinting scans To: Gregory Price , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, jannh@google.com, pfalcato@suse.de, hannes@cmpxchg.org, shy828301@gmail.com, raghavendra.kt@amd.com, stable@vger.kernel.org References: <20260922182928.2199090-1-gourry@gourry.net> <20260922182928.2199090-2-gourry@gourry.net> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 654F2120008 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: abhjzy7cj4jabga6t64a7cc5qkioyoa1 X-HE-Tag: 1790250339-586886 X-HE-Meta: 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 bHM/8nXQ JtW7fXXg7mAcTCbV3KUC5pOXOIfrUE4K7khf/paE3j26+7IV1SXDBJC5j5r9ckUL7BYD7t3K65HbfTJYbXMwk6gnCXFAin5r+3XXwM4GPHm6QB7kQRGjwNri/MJj6KICvsfCvZblMjxtAmSs7j35bynKYP91zE/gFa++CQZ+CQzOZINOcDHcs/ZlfkDE8EBVCy2InUamKJdzTzoWFKFr+mrhwsI713eGM1DAw85SKLBUhGT6z4XaDqjiBgwAeoIWQq1K8Adc5Pn8J9CcDEB/88fvfyDoiiylpoUHLPPmILhBGtmKYmq7cHPVAcLkP5uCcr741zAwbVtyk5LxU2pkDMJJpQw0romW5YrFCKnB9yZUmcJFJpYf8zzLAMwrRFlgfqTjTwCplqshs6wriRoJEkQyt6TEMC1jiQmUY Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/22/26 20:29, Gregory Price wrote: > From: "Gregory Price (Meta)" > > folio_can_map_prot_numa() derives folio eligibility from the global > balancing mode. The mode (normal, tiering, or combined) describes > which balancing mechanisms are enabled (placement vs promotion). > > The global setting itself cannot describe the intent of an individual > protection walk because normal-mode tempers its scanning activity based > on a number of heuristics (read-only VMAs, activeness of VMA, etc). > > In tiering or combined mode, applying these normal-mode optimizations > to an entire VMA is incorrect and breaks tiering. > > - Opting VMAs out of scanning because they became inactive obviously > breaks tiering - because the intent is to identify when a VMA > becomes active. Applying it in tiering modes causes Incomplete sentence. > > - Opting Read-only file VMAs out of scanning is just incorrect for > tiering modes because its intent is to prevent bouncing between > sockets (east-west), while tiering controls tier migration > (north-south). The result is hot read-only files can overload > lower tier bandwidth. > > Add MM_CP_PROT_NUMA_PROMO_ONLY and let task_numa_work() select the type > of walk. Build the change-protection flags there and pass them unchanged > through change_prot_numa() so its PTE/PMD paths use the same decision. > > Have folio_can_map_prot_numa() derive the single-threaded private state at > the point of use instead of adding another precomputed boolean to the > protection-walk interface. This keeps the interface focused on scan intent > and avoids plumbing VMA-derived state beside cp_flags. > > The tradeoff for the cleaner interface is an atomic mm_users read for each > folio, rather than once per PTE range. Check the promotion-only top-tier > exclusion bit first as a mild optimization. > > The scan-intent interface is required by the following memory-tiering > fixes and must accompany them when backported. > > Fixes: c574bbe91703 ("NUMA balancing: optimize page placement for memory tiering system") > Cc: stable@vger.kernel.org > Suggested-by: David Hildenbrand > Link: https://lore.kernel.org/r/4d2853c9-edf4-4685-b186-7214ed6abd84@kernel.org > Assisted-by: LLM > Signed-off-by: Gregory Price (Meta) > --- LGTM Acked-by: David Hildenbrand (Arm) -- Cheers, David