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[2003:d8:2f0c:c200:fa4a:c4ff:1b32:21ce]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4715257d90bsm1082715e9.2.2025.10.17.08.44.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Oct 2025 08:44:34 -0700 (PDT) Message-ID: <05d7832e-7bbc-4c73-b293-f512b4776aeb@redhat.com> Date: Fri, 17 Oct 2025 17:44:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item To: Pedro Demarchi Gomes , Andrew Morton Cc: Xu Xin , craftfever , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20251016012236.4189-1-pedrodemargomes@gmail.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20251016012236.4189-1-pedrodemargomes@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: Tg8sv9boFIheSJ_H2PvBS_E3_E1f8r4_k_iCpuxLNRU_1760715877 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Stat-Signature: nj6d8hiq4ectao68cysityw8gmsammou X-Rspam-User: X-Rspamd-Queue-Id: 6E7D8100002 X-HE-Tag: 1760715887-884142 X-HE-Meta: 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 16LaBNYL 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 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: List-Subscribe: List-Unsubscribe: On 16.10.25 03:22, Pedro Demarchi Gomes wrote: > Currently, scan_get_next_rmap_item() walks every page address in a VMA > to locate mergeable pages. This becomes highly inefficient when scanning > large virtual memory areas that contain mostly unmapped regions. > > This patch replaces the per-address lookup with a range walk using > walk_page_range(). The range walker allows KSM to skip over entire > unmapped holes in a VMA, avoiding unnecessary lookups. > This problem was previously discussed in [1]. > > [1] https://lore.kernel.org/linux-mm/423de7a3-1c62-4e72-8e79-19a6413e420c@redhat.com/ > > --- > > v3: > - Treat THPs in ksm_pmd_entry > - Update ksm_scan.address outside walk_page_range > - Change goto to while loop > > v2: https://lore.kernel.org/all/20251014151126.87589-1-pedrodemargomes@gmail.com/ > - Use pmd_entry to walk page range > - Use cond_resched inside pmd_entry() > - walk_page_range returns page+folio > > v1: https://lore.kernel.org/all/20251014055828.124522-1-pedrodemargomes@gmail.com/ > > Reported-by: craftfever > Closes: https://lkml.kernel.org/r/020cf8de6e773bb78ba7614ef250129f11a63781@murena.io > Suggested-by: David Hildenbrand > Signed-off-by: Pedro Demarchi Gomes > --- This patch will need some more work. @Andrew, please drop it for now. -- Cheers David / dhildenb