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b=kojrPeUxA17rgHtPYsXoyrZJG3a9/hQhygq5TnTfpxEgTYl6FZ6TDmQh1SE7cmgaZ +JJbLl0hePVs4amoZQLuFgekaROkwmF+nBK5VM15NFdfvMWZzcPuZn21hTAqHKiw5m pYJqy400PqsDBUV/2D3JTvbLDcqUvFRAO7BqSU+4qW5T3wCQVInSqoCpLwB03gSHFY cjE10PuULCEUuD0AFdeNQu7AV76ddG9L3E1MxjSao1uPevwuTzpt6LxSjvRofrbenN TuvuxRmIIn/bHJrZJRd4MwAWEFrggaboRPPuuQMNIThCVHPOCKP9RbK+AE4JIIHLnH 5CdmRXqNuzMDA== From: SeongJae Park To: Usama Arif Cc: SeongJae Park , Andrew Morton , npache@redhat.com, david@kernel.org, ziy@nvidia.com, willy@infradead.org, linux-mm@kvack.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, hannes@cmpxchg.org, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-kernel@vger.kernel.org, kernel-team@meta.com, richard.weiyang@gmail.com Subject: Re: [PATCH v3] mm: migrate: requeue destination folio on deferred split queue Date: Thu, 12 Mar 2026 17:16:30 -0700 Message-ID: <20260313001630.80081-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260312104723.1351321-1-usama.arif@linux.dev> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: F227A100015 X-Stat-Signature: r7po4cji548me3pkpknm8ucrfpx94n5p X-Rspam-User: X-HE-Tag: 1773360999-626818 X-HE-Meta: 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 dTSc0NQn W6M2Dn/1M7poVz5vYMGJmL4MAhDnemjanmhSK Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 12 Mar 2026 03:47:23 -0700 Usama Arif wrote: > During folio migration, __folio_migrate_mapping() removes the source > folio from the deferred split queue, but the destination folio is never > re-queued. This causes underutilized THPs to escape the shrinker after > NUMA migration, since they silently drop off the deferred split list. > > Fix this by recording whether the source folio was on the deferred split > queue and its partially mapped state before move_to_new_folio() unqueues > it, and re-queuing the destination folio after a successful migration if > it was. > > By the time migrate_folio_move() runs, partially mapped folios without a > pin have already been split by migrate_pages_batch(). So only two cases > remain on the deferred list at this point: > 1. Partially mapped folios with a pin (split failed). > 2. Fully mapped but potentially underused folios. > The recorded partially_mapped state is forwarded to deferred_split_folio() > so that the destination folio is correctly re-queued in both cases. > > Reported-by: Johannes Weiner > Fixes: dafff3f4c850 ("mm: split underused THPs") Seems the commit is merged in 6.12. And I assume the user impact on THP-shrinker enabled systems is visible. If so, should we Cc stable@ ? > Acked-by: Zi Yan > Acked-by: David Hildenbrand (Arm) > Signed-off-by: Usama Arif Acked-by: SeongJae Park Thanks, SJ [...]