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Thu, 12 Mar 2026 07:27:09 -0700 (PDT) Received: from localhost ([2603:7000:c00:3a00:365a:60ff:fe62:ff29]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8cda71834d9sm291561885a.14.2026.03.12.07.27.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Mar 2026 07:27:09 -0700 (PDT) Date: Thu, 12 Mar 2026 10:27:08 -0400 From: Johannes Weiner To: Usama Arif Cc: 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, 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: References: <20260312104723.1351321-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260312104723.1351321-1-usama.arif@linux.dev> X-Rspamd-Queue-Id: 0E0A240005 X-Rspamd-Server: rspam07 X-Stat-Signature: b1mm3rp6j33g3wfifumx87gybrym8gp5 X-Rspam-User: X-HE-Tag: 1773325630-722481 X-HE-Meta: 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 8XRP/P7I 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Mar 12, 2026 at 03:47:23AM -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") > Acked-by: Zi Yan > Acked-by: David Hildenbrand (Arm) > Signed-off-by: Usama Arif Acked-by: Johannes Weiner