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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Arnd Bergmann , Kairui Song , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, Luka Bai Subject: Re: [PATCH 5/5] mm: support choosing to do THP COW for anonymous pmd entry. Message-ID: References: <20260501-thp_cow-v1-0-005377483738@tencent.com> <20260501-thp_cow-v1-5-005377483738@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Authority-Info-Out: v=2.4 cv=UfxciaSN c=1 sm=1 tr=0 ts=69f4c047 cx=c_apl:c_pps:t_out a=YrL12D//S6tul8v/L+6tKg==:117 a=YrL12D//S6tul8v/L+6tKg==:17 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=x7bEGLp0ZPQA:10 a=UaoJkeuwEpQA:10 a=VkNPw1HP01LnGYTKEx00:22 a=292iOHRO3ARvOjuV3UUA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=zgiPjhLxNE0A:10 a=zZCYzV9kfG8A:10 X-Proofpoint-ORIG-GUID: sr5x0X2KYkUyqD5j_4TciEAxaooc4_F8 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTAxMDE0NiBTYWx0ZWRfX+WW7lkscOdYB JRF6gAgqna3aLhnH6+mV5AiOZKSeyayBJCl3a1roR/0V0//vba5klvw6uiNf/Zfw+tpdBUrxw8e 3je6nzqNWImfzT8RF7UdRauzSloLIvHHaCaQUpGLwdXdvcnMjO9eO5xf48beeDUMD21/d6fJtap xY2nIR/01GsVU+nE7OhRQqxDNxl/1YbLeUi1to2hN6Wz4WhndQmO4Z4ipHgstQ2C5RJqrr4fpjs RDemQ+/vQxc/0MMWggebofrCF7EKSw9B/OdtJKZaiSDM7BMS/AMNsJ3//K9+h6aQR5oEmp5n2el 0Ck9gGal0ANQzbT2cfIWvXIx37hxs+N5lOsFqM5h8u0X1PL+CSDIS4g21rGgkI= X-Proofpoint-GUID: sr5x0X2KYkUyqD5j_4TciEAxaooc4_F8 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 531A5180021 X-Rspam-User: X-Stat-Signature: 8aqm75xhymy6sam554skkxyprdqyo571 X-HE-Tag: 1777647688-625945 X-HE-Meta: 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 BaB8LsLa 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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