From: Luka Bai <lukafocus@icloud.com>
To: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: linux-mm@kvack.org, 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 23:01:21 +0800 [thread overview]
Message-ID: <afTAQZn9m165Y41p@LUKABAI-MC1> (raw)
In-Reply-To: <c580340a-48c3-4cfa-92bd-593a95d0090f@kernel.org>
在 Fri, May 01, 2026 at 09:11:42AM +0200，David Hildenbrand (Arm) 写道：
>
> > - /*
> > - * 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
Sorry I didn't notice this thread earlier. That is a great suggestion! I can keep
this branch and do the folio copying instead of fallback, that actually helps
to avoid the extra checking about swapcache when the refs is definitely not
suitable for exclusive use. Thanks! :)
Best,
Luka
next prev parent reply other threads:[~2026-05-01 15:01 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)
2026-05-01 15:01 ` Luka Bai [this message]
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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