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From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Luka Bai <lukafocus@icloud.com>, linux-mm@kvack.org
Cc: Jonathan Corbet <corbet@lwn.net>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Lorenzo Stoakes <ljs@kernel.org>, Zi Yan <ziy@nvidia.com>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	"Liam R. Howlett" <liam@infradead.org>,
	Nico Pache <npache@redhat.com>,
	Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
	Barry Song <baohua@kernel.org>, Lance Yang <lance.yang@linux.dev>,
	Vlastimil Babka <vbabka@kernel.org>,
	Mike Rapoport <rppt@kernel.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Michal Hocko <mhocko@suse.com>, Jann Horn <jannh@google.com>,
	Arnd Bergmann <arnd@arndb.de>, Kairui Song <kasong@tencent.com>,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	linux-doc@vger.kernel.org, Luka Bai <lukabai@tencent.com>
Subject: Re: [PATCH 5/5] mm: support choosing to do THP COW for anonymous pmd entry.
Date: Fri, 1 May 2026 09:11:42 +0200	[thread overview]
Message-ID: <c580340a-48c3-4cfa-92bd-593a95d0090f@kernel.org> (raw)
In-Reply-To: <20260501-thp_cow-v1-5-005377483738@tencent.com>


> -	/*
> -	 * See do_wp_page(): we can only reuse the folio exclusively if
> -	 * there are no additional references. Note that we always drain
> -	 * the LRU cache immediately after adding a THP.
> -	 */
> -	if (folio_ref_count(folio) >
> -			1 + folio_test_swapcache(folio) * folio_nr_pages(folio))
> -		goto unlock_fallback;
>  	if (folio_test_swapcache(folio))

I don't see why you would want to remove this check, really. Instead of
"fallback", you might want to try copying the PMD.

-- 
Cheers,

David

  reply	other threads:[~2026-05-01  7:11 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-05-01  5:55 [PATCH 0/5] mm: Support selecting doing direct COW for anonymous pmd entry Luka Bai
2026-05-01  5:55 ` [PATCH 1/5] mm: add basic madvise helpers and branch for THP setup Luka Bai
2026-05-01  5:55 ` [PATCH 2/5] mm: add pmd level THP COW parameter in sysfs Luka Bai
2026-05-01  5:55 ` [PATCH 3/5] mm: add pmd level THP COW judgement helpers Luka Bai
2026-05-01  5:55 ` [PATCH 4/5] mm: enable map_anon_folio_pmd_nopf to handle unshare Luka Bai
2026-05-01  5:55 ` [PATCH 5/5] mm: support choosing to do THP COW for anonymous pmd entry Luka Bai
2026-05-01  7:11   ` David Hildenbrand (Arm) [this message]
2026-05-01 15:01     ` Luka Bai
2026-05-01  7:07 ` [PATCH 0/5] mm: Support selecting doing direct " David Hildenbrand (Arm)
2026-05-01 16:16   ` Luka Bai
2026-05-01 18:30     ` David Hildenbrand (Arm)
2026-05-02  5:06       ` Luka Bai
2026-05-03  7:03 ` [syzbot ci] " syzbot ci

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