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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-939e80e4c36sm108896485a.40.2026.09.10.17.18.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Sep 2026 17:18:36 -0700 (PDT) From: Gregory Price To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, david@kernel.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, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, jannh@google.com, pfalcato@suse.de, osalvador@suse.de, hannes@cmpxchg.org, raghavendra.kt@amd.com, stable@vger.kernel.org Subject: [PATCH v2 2/4] mm: allow shared folios to be promoted to a fast tier Date: Thu, 10 Sep 2026 20:18:24 -0400 Message-ID: <20260911001826.2109390-3-gourry@gourry.net> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260911001826.2109390-1-gourry@gourry.net> References: <20260911001826.2109390-1-gourry@gourry.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 27E5420007 X-Stat-Signature: e4786tq38o6kebjchu4sz66w4cn8rnhh X-Rspam-User: X-HE-Tag: 1789085922-443842 X-HE-Meta: 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 Yx6Zcwfa OI7GYwp2uL5JW7jraYDpzX5NrtGVXbrRelSk5ISw455KdTM+9YJC56bvSSheLwtxyXb2jXHeBm2TFxNAhdzvK0o4RTeYV9D/n20HLz/BlvODsQ8ngOZf08CJm/aSjSmXEDZlfpy4fCn4T/L+Vqn7SHcbt4AzQSSvXTP5Fy3KNiZgR9t7JnvIouQB6un+mLvreYil2wArQe1pPd2D/sPkaMtaGcdnB3N+DR2qqZij0ZyojMkZ7sIS9WB/RlLs29cL5F4HUsxp+HzDhuTnlqOqs/1jZfWLy7rKOWkgJLaR33rKB7LI8EF98vu1qsSjCpdjWV56AXpBCtjCtkUhinBwpls3TVFznX8rWuoq6UgHZPCEhiMbrYWNInoGivtjMIfRZ4R4tdYyprSdzHTCJsh6k5/LOTg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "Gregory Price (Meta)" NUMA balancing rejects shared copy-on-write folios and executable file folios mapped by multiple processes to avoid placement bouncing. These checks also block promotion from slow memory. Allow such folios to participate when moving from a slow tier to a fast tier. Keep the existing restrictions for ordinary placement. Fixes: c574bbe91703 ("NUMA balancing: optimize page placement for memory tiering system") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Gregory Price (Meta) --- mm/mempolicy.c | 8 ++++++-- mm/migrate.c | 6 ++++-- 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index a082ccfa09ec..19b599bc2dd1 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -863,8 +863,12 @@ bool folio_can_map_prot_numa(struct folio *folio, struct vm_area_struct *vma, if (!folio || folio_is_zone_device(folio) || folio_test_ksm(folio)) return false; - /* Also skip shared copy-on-write folios */ - if (vma_is_cow_mapping(vma) && folio_maybe_mapped_shared(folio)) + /* + * Shared copy-on-write folios are poor NUMA placement candidates, but + * a hot folio on a slow tier still needs a hint fault for promotion. + */ + if (vma_is_cow_mapping(vma) && folio_maybe_mapped_shared(folio) && + !folio_use_access_time(folio)) return false; /* Folios are pinned and can't be migrated */ diff --git a/mm/migrate.c b/mm/migrate.c index a369d0c95c38..afd9c97d2389 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2697,12 +2697,14 @@ int migrate_misplaced_folio_prepare(struct folio *folio, /* * Do not migrate file folios that are mapped in multiple * processes with execute permissions as they are probably - * shared libraries. + * shared libraries, unless this is a promotion from a slow tier. * * See folio_maybe_mapped_shared() on possible imprecision * when we cannot easily detect if a folio is shared. */ - if ((vma->vm_flags & VM_EXEC) && folio_maybe_mapped_shared(folio)) + if ((vma->vm_flags & VM_EXEC) && + folio_maybe_mapped_shared(folio) && + (!folio_use_access_time(folio) || !node_is_toptier(node))) return -EACCES; /* -- 2.55.0