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b=Hg4n58kr9CttSBeBe2vfr/Et9VbEL8MqbZpXHJ0iiBzc4hhByg3+16A1POnInnQX8 cJHOIa1g0xiybET9Pia85SthvEICDSRl9C4Zdda37DziAECqHjqCaHArGGnIAkEvOa faZ0d1SEgd5dl33T2wObXW0Oy1bulzKVIEs3gav9zbV4S8vJ36EFduALALooYn+hoS PucgzMknkfWIgwVRs8uYRuCn+/KhnIfZ8S22nrjXbCDtJJGfkBo0B4sXzPcbZyzHSo 0OTJIUlfRNtv51E8vmwaRvxToByyj8dMObojWQzSnCKgp87UE7EwMf9Yepur01Rnkk CiGTvFVGMNtgQ== Message-ID: Date: Thu, 24 Sep 2026 17:32:22 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/7] mm: allow shared folios to be promoted to a fast tier To: Gregory Price Cc: linux-mm@kvack.org, 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> <20260922182928.2199090-3-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-Stat-Signature: 1i7bkoq3xmx9uwcw56c4e47u3ckig59q X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: BA1F04000F X-HE-Tag: 1790263957-554739 X-HE-Meta: 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 wrWJobw8 GVx8RBgAlU/mFRjiX15u95wBqiKpyOo5wBw7ZbGhtUMh0qOqMFpmFgsMHCgcqS1s/BN3D8BeBHZA9ryQAbXZSznoGRV7QhBAFrCQXuCXj1XF04IdplgKMjbki8JUOH7IwjKfridwqdmiiBkBEnkk29WezcKKhcpj+HDdPNGUITGJfyZ9M8mJXMtsVC++wFxWpH7I4ldYXhQsr56xm89UUqFCII2TgsSkmSYClt2XI0h6DFfISaR6I6R5Jhih39c/haZkCLaFtCMdQ6E6TwCViVtlx5Ki9T9mReKt8gWEBMyqgtrnvNQBTfrVcAlHGbIxd/8NH7UKRZkQUtMbnzAzSyZFOgw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/24/26 16:07, Gregory Price wrote: > On Thu, Sep 24, 2026 at 01:59:15PM +0200, David Hildenbrand (Arm) wrote: >> I wonder if a better name would just make the comment above (about memory >> tiering) implicit and make more sense of the sysctl_numa_balancing_mode & >> NUMA_BALANCING_MEMORY_TIERING) check. >> >> folio_promotable() >> >> folio_is_promotable() >> >> folio_numa_promotable() >> >> etc. >> >> because that seems to be what we really test with both things combined. >> > > maybe: folio_numab_promotable() ? Works for me if "numab" means numa balancing :) > >>> - if ((vma->vm_flags & VM_EXEC) && folio_maybe_mapped_shared(folio)) >>> + if ((vma->vm_flags & VM_EXEC) && >>> + folio_maybe_mapped_shared(folio) && >>> + (!folio_in_lowtier(folio) || !node_is_toptier(node))) >>> return -EACCES; >>> >>> /* >> >> Sashiko has some comment about anonymous shared COW folios. I think it has a >> point, but didn't look too closely. >> > > its tl;dr: > > `skipping this check means those folios could end up freely migrating east-west > between slow tiers` > > Which cannot happen (we only migrate to top tier, numab will never > migrate *to* a slow tier). > > basically false-positive False-positive? From Sashiko? I am shocked! -- Cheers, David