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[2003:d8:2f25:700:d846:15f3:6ca0:8029]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3cf33fb9cebsm41095491f8f.46.2025.09.08.04.32.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 08 Sep 2025 04:32:06 -0700 (PDT) Message-ID: <9a0c07b9-5bf0-4251-8609-fbaf0ca75bf9@redhat.com> Date: Mon, 8 Sep 2025 13:32:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/1] mm: skip mlocked THPs that are underused early in deferred_split_scan() To: Kiryl Shutsemau , Lance Yang Cc: akpm@linux-foundation.org, Liam.Howlett@oracle.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, dev.jain@arm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, npache@redhat.com, ryan.roberts@arm.com, usamaarif642@gmail.com, ziy@nvidia.com References: <20250908090741.61519-1-lance.yang@linux.dev> 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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: L4l1awbld8jQ-_H7RHXjz1Ubb_-2QHh4bZaAhSF9DHA_1757331128 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: rspam10 X-Rspamd-Queue-Id: C43AE160005 X-Stat-Signature: uabx97bbz45pxzm5h8hdsr6isn355jrk X-Rspam-User: X-HE-Tag: 1757331130-679686 X-HE-Meta: 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 yY5tCNTA kdhTV0MOiBUnrL7CwayRRoYU8k1d/XP9gM8mwNfd78A0BwIv0nNYbUbQdX/xSvLNGY5o4YuuckuW5mxu5q4hk9HoWwudcU6+uZSnUE+DNSaFTPZQR+72ez6H/HG5/3+fuoZUEwB/rRZKVq7Oi6WB86XrZPx6xpb3Vh+hzwBYZ/x3nFjdCGQW6CFpijtAvZ7zznKev2KmQ/AsBpXRYIRONocRlHfrz9rl0KRxRZeUnPpx9VNKEsBa8UH5QZoUWpwPCCBy6x+E6iXmRWx/Q4mCyhjVoL4FzWHWiz/09R18wnGLDv6mdLP52pktcHC2cL5is8tCoUo1OViRIr3HCdoI5V+ZdaY6HyQyLqyVdWYceOzzp2DJKkuAniF/Ed5DOJ43S6TAVxmxiMs/PcNfswT4G7pwUijLU3puhfMq7/JowpTHcztqb5mAPsQI2U6SGqfP+tBqpmpOp81MnFzooRjIUb1wFWuEkXjxDHbjk 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 08.09.25 12:38, Kiryl Shutsemau wrote: > On Mon, Sep 08, 2025 at 05:07:41PM +0800, Lance Yang wrote: >> From: Lance Yang >> >> When we stumble over a fully-mapped mlocked THP in the deferred shrinker, >> it does not make sense to try to detect whether it is underused, because >> try_to_map_unused_to_zeropage(), called while splitting the folio, will not >> actually replace any zeroed pages by the shared zeropage. > > It makes me think, does KSM follows the same logic as > try_to_map_unused_to_zeropage()? > > I cannot immediately find what prevents KSM from replacing zeroed mlocked > folio with ZERO_PAGE(). > > Hm? I assume if you're using mlock and at the same time enable KSM for a process/VMA, you're doing something wrong. In contrast, THP is supposed to be transparent (yeah, I know ...). -- Cheers David / dhildenb