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imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=oxRUEyPD; spf=pass (imf04.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=1772804977; a=rsa-sha256; cv=none; b=QaC/L4yMHs78atF3wrOSvY0bNXsf+QARQIuRLQo5rpBNgnZxTD8d2r/gS8tzXQ2eeafBF1 xz2lTWEj/UN5Yu2SIBZudOvVcRXVZCLAeuUR29fzEJMSTIdWfzELHve8sSQji7OWHpRV37 F9TK4Q7HOO6RhU/1bj2fBVI9gSNiNa8= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id C63F140234; Fri, 6 Mar 2026 13:49:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B110C4CEF7; Fri, 6 Mar 2026 13:49:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772804975; bh=irOuPnqtfg3b/SaxHjIDOK3emq7XQZuod4JIYQGwsI0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=oxRUEyPDum7HCDI0i9m+D1kN2UUcv7bGDNu06MEpelNeSK0caUq6J8rXGgksSmgj9 QJfRAQ7UULSbl2fn/6qyoLO6VSkYg1jcOMl3oqLnLlFguufUHVdjaQxHByMwCDQaFp /OUWbTzGykXwFIZ5eH5t95j1oB+pMiEiCZcTS/o9hF2PhaXmZpSRP2ldfQVucIklG/ o9U+SiDeEyD8vihv4rjvxPdvUpYrhnpER2Eu8UQ331kd/HUTYgrlsXNIeTmiWLvMQO Ro6cA1l3zdgawtAikWWHNqtBPPlYKTT/g5q53yFc6LO1xVvpO80OgxbgtqWKdf3BqX SDg6nKcbSa6pw== Message-ID: Date: Fri, 6 Mar 2026 14:49:27 +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-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: F13A440006 X-Stat-Signature: qxau7psdy3u5ccm3kthxz4a4yd1zzocf X-Rspam-User: X-HE-Tag: 1772804976-207260 X-HE-Meta: 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 vejEGG5D LdcH2v4g0L3vdTUBTvM2Vbe8qJ1d7KYkF9h1UA+w6p8BWHH0mEMGUksc9Nl3WUkgh+MB8Se4MqhRYDY2bLtaBvQNqaqMNg2WrcWsCXcSxUg7FEM8ZfYCTNkKGeF0SIHuiLr2kRB4KDS0xcwsWfnRCvxmwzkLqcWkhW7uK6ZW+jYHwi49ZuRprKsjZJnUcQXoLhVqdgJEgTHEaqW2anmW5G59A3uc+HQ2PTGU/bf2Wiehd9VKavBI2tZO6KQrGoNy8DTxaNKTvwQ24NXxolU+q0iu7EuEHvKgGsnKYRcjKSwU+Bu1472tkNliHpxLibRZUH8mQB8540gMv9DRGbNwi5/MKPbJXJf9/5GHeXRhkXjDFjhc3c9LmD2EZ8l5+95GsJmx1hL/rfj78ZTc= 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); Doesn't that mean that you will readd any large folios, even if already previously taken off the list after scanning? So I am not sure if your "if the source was a large folio that was on the queue." comment is accurate? -- Cheers, David