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b=DuWzI4UBSebrvs52L3URsESaYwY6E249CplCTg89RqcP6gHXSWzexwipGvO1ZK7jM j6xn07MpLCY+SpLhFy/kWbOtD7gA3myI9x8NbYqkCJS7LZ0LFf4o10uBCm3fjUKDON cPGcAx3lkMHOAFiEkX2455t7Y26J5F51hDQUBlSM= Date: Thu, 12 Mar 2026 17:52:41 -0700 From: Andrew Morton To: SeongJae Park Cc: Usama Arif , 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 Message-Id: <20260312175241.01b876f3b325264f43312d79@linux-foundation.org> In-Reply-To: <20260313001630.80081-1-sj@kernel.org> References: <20260312104723.1351321-1-usama.arif@linux.dev> <20260313001630.80081-1-sj@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 1CDCCA0005 X-Stat-Signature: gj63ka8i913atc3ykoyyikn13nzces41 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1773363163-8669 X-HE-Meta: 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 GYP67AS2 hFJdnAHpy1urK0ZRSE+XDZTssyJg+FLPTrnx++Sc/C0/UpA4QQ3qlzjhBibWujMp9ql/1e8ewm1F7ldkVkBtkuUP/WQ4vWGAMo41mkca+mF+SU+S12EE12LWYb/leOuN7ajuiJEp06daw8ENaaRKesQ/fKexntxvdxuVR+DgeGnEUdcvC+SQ5flqa8xxFhClP8HMIRnlbFULtzyp2tjeSlQuw2HsA795HM8oBFEfwjosuzfXftNHepyoFsVjbcKLzI4Oc5IL4BLPgj2Ke9XX6OIreeN0qwcruu+vTYgt8f3Rxd+9zgClBdrqtYJHEvqzOmlmuIOUoN3mzCR8u7tO39Yad0+O+pAX56Ik7atXuri3DZ1bdoT/t//BuCiO1211mjMQi9IS80GKdQROB7qbW0XHCag== 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 17:16:30 -0700 SeongJae Park wrote: > > 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@ ? I think the user impact should be visible to backport, but the changelog is elusive on details?