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[2003:cb:c735:400:2501:5a2e:13c6:88da]) by smtp.gmail.com with ESMTPSA id 25-20020a05600c025900b003fc00702f65sm8323118wmj.46.2023.07.17.09.48.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 Jul 2023 09:48:59 -0700 (PDT) Message-ID: <0250a2d7-c79b-0e0f-8161-bf475daf1c82@redhat.com> Date: Mon, 17 Jul 2023 18:48:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v1 1/3] mm: Allow deferred splitting of arbitrary large anon folios To: Ryan Roberts , Andrew Morton , Matthew Wilcox , Yin Fengwei , Yu Zhao , Yang Shi , "Huang, Ying" , Zi Yan Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20230717143110.260162-1-ryan.roberts@arm.com> <20230717143110.260162-2-ryan.roberts@arm.com> <90b406af-9db4-b668-a7a0-e574e104c84c@redhat.com> <028c5f5b-b67c-9ccc-bc06-468f47362999@arm.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <028c5f5b-b67c-9ccc-bc06-468f47362999@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 908BD18001F X-Rspam-User: X-Stat-Signature: rtcwnhhknfkqbu3tubznobztxff7nd7m X-Rspamd-Server: rspam01 X-HE-Tag: 1689612543-182030 X-HE-Meta: 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 kCmzqalA SX5CZK5OFIF9nvD+QWy8R1t+Dx/t4MihOT3ztzPDGZZglNGkchLBRaIlE66DwcXG5Gn5u5Rb/IGo5tbz1DLJPY1wpLI7hqUtx78x8LctegEX1ICkBMVOTQDPOf/jbhnjKRXBD2qt9FbDcPycHx6+VE3cl2Nysipbu3/b518hWa/5w3NdzqeBlbv8q4w0ytOyJRegY5ENpH/7e9R7wtd89N8tA5dzX9xEZiPiuf0PJxcIRm4+3srqEJrGtCmbGytWTE4nySsBtXuPEbYQTFzBsQWL95Xr0wRdaVKXramKFRV/TU5Dle0jU11UFBW8vrQVGM1eS2K1xU+e6RLG9oJ8HFN4h8rssPUWp2sDL8DQ/6PrYx8JFNkID2eOofGmqoj1gD3CUHWiWo87YqY9PRgSy2noXib/ole5u9eeen8/EYcToxpbKZXiLJrZr1ipnXElM6qWhlzgIZKsbzHjyqd7EbSdJPdDT8IO7TXHmtQUE4MO5TTo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 17.07.23 18:01, Ryan Roberts wrote: > On 17/07/2023 16:42, David Hildenbrand wrote: >> On 17.07.23 16:31, Ryan Roberts wrote: >>> In preparation for the introduction of large folios for anonymous >>> memory, we would like to be able to split them when they have unmapped >>> subpages, in order to free those unused pages under memory pressure. So >>> remove the artificial requirement that the large folio needed to be at >>> least PMD-sized. >>> >>> Signed-off-by: Ryan Roberts >>> Reviewed-by: Yu Zhao >>> Reviewed-by: Yin Fengwei >>> --- >>>   mm/rmap.c | 2 +- >>>   1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/mm/rmap.c b/mm/rmap.c >>> index 0c0d8857dfce..2baf57d65c23 100644 >>> --- a/mm/rmap.c >>> +++ b/mm/rmap.c >>> @@ -1430,7 +1430,7 @@ void page_remove_rmap(struct page *page, struct >>> vm_area_struct *vma, >>>            * page of the folio is unmapped and at least one page >>>            * is still mapped. >>>            */ >>> -        if (folio_test_pmd_mappable(folio) && folio_test_anon(folio)) >>> +        if (folio_test_large(folio) && folio_test_anon(folio)) >>>               if (!compound || nr < nr_pmdmapped) >>>                   deferred_split_folio(folio); >> >> !compound will always be true I guess, so nr_pmdmapped == 0 (which will always >> be the case) will be ignored. > > I don't follow why !compound will always be true. This function is > page_remove_rmap() (not folio_remove_rmap_range() which I add in a later patch). > page_remove_rmap() can work on pmd-mapped pages where compound=true is passed in. I was talking about the folio_test_pmd_mappable() -> folio_test_large() change. For folio_test_large() && !folio_test_pmd_mappable() I expect that we'll never pass in "compound=true". -- Cheers, David / dhildenb