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imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=olDGrSHo; spf=pass (imf11.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772805087; a=rsa-sha256; cv=none; b=rw2Jov7JOSIL0bcRWWuJOXXZVerOagwwxv5p0abshm3leNbeAH/+8iTgVDZtQjT4+Dsr/e UQIDRxvm/4rtS+jYdx7oHAKuNkqrU1nckudPHNY6SlX/2aw4tYf1sbKFyV+ZpHPAqXNoSD cDEGvwVJSYoY0XPqnNo7uJEP0NedE+0= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id DCBC540234; Fri, 6 Mar 2026 13:51:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D36EC4CEF7; Fri, 6 Mar 2026 13:51:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772805085; bh=7RBqYcR2ikcPrdrJ3ktRl7uN+Go6X/fHUgtHA/HqlUo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=olDGrSHoZxTa/sqjxUa1qieNAdDrlVRkMgYXIuY7X/1O+Cik9Lje5jim/kM6bxyq8 eXYV43EoaAI+x1hBvbNFSa1YIGEpd5/MhQw5v/BC63BQTgWyhfJH40L/HIpqdMYbI4 dXWHw/OjaXloYQ9ARACOfN8hO+FTWX4StOcfNl7kduWUm4+kA2hPNXKW95sxUvJdIv jiwqEy/yNNgRJLQG5XRW8nRj/AFzf0h0w+jhMLaJ/skjuzjUDhtjz629jh/s+m6wuq mPlBtha9jfTpjS5/ezErsC176oDum/COOGaHtk1kg1PhfYLmbsIDD9pfZPqIEcwt5M iGhFzUeVMmmDA== Message-ID: <3ed67a98-42a6-40fa-a7d8-a1a264f6151d@kernel.org> Date: Fri, 6 Mar 2026 14:51:17 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: migrate: requeue destination folio on deferred split queue To: Usama Arif , Andrew Morton , npache@redhat.com, ziy@nvidia.com, linux-mm@kvack.org Cc: 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 References: <20260306133556.2051251-1-usama.arif@linux.dev> 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: iab5s5uqsf38mqqrmt8iqmozmnk7xf45 X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: CFFE240013 X-HE-Tag: 1772805086-201352 X-HE-Meta: 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 4an3Q9ZU uxrO6O8VDX41JnD5NODuGjDxsREnML8eV+yLkeaR6wWBdkq9ytljoYkRV2fSyAVcm8DoGscvuJgv5CIvomfS2IU3OoiSrvG161wr8ZvVeFhQbW8WVW//n/lJ5S0tf3wUSElM7wWjCQCYiPgVHf5lvGbkvDPn4rVLCj3R/fJYhOKBTNC1xLiYex2lF939RrGjpJBBzeOXR9h65oDhf3eGBJRj8ulywvv+dgpIlgXRWHqnPS7J2yjm5Ms+xim1Ozjvf60fZCRW582sRLylHK3EzsB5Jywnlv/foccnMcIIC4kjuJtVOfC1U0009WT8NnNMcURrUsXR0vNZCIPgWyU6QFZxSCIgopnMsJsod7pDm2dBTWKfb3MAkBeYC2uSfyYZT/MqT Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/6/26 14:35, 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 calling deferred_split_folio() on the destination folio > after a successful migration, for large rmappable folios. > > Reported-by: Johannes Weiner > Fixes: dafff3f4c850 ("mm: split underused THPs") > Signed-off-by: Usama Arif > --- > mm/migrate.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index ece77ccb2ec0..98d0a594f7b7 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1393,6 +1393,17 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private, > if (old_page_state & PAGE_WAS_MAPPED) > remove_migration_ptes(src, dst, 0); > > + /* > + * Requeue the destination folio on the deferred split queue if > + * the source was a large folio that was on the queue. Without > + * this, NUMA migration causes underutilized THPs to escape > + * the shrinker since the source is unqueued in > + * __folio_migrate_mapping() and the destination is never > + * re-queued. > + */ > + if (folio_test_large(dst) && folio_test_large_rmappable(dst)) > + deferred_split_folio(dst, false); Also, should you be checking for anon and non-device folios? -- Cheers, David