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(p200300d82f4d0e00029859cc25140052.dip0.t-ipconnect.de. [2003:d8:2f4d:e00:298:59cc:2514:52]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45dd2304e16sm75072365e9.7.2025.09.05.07.58.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 Sep 2025 07:58:57 -0700 (PDT) Message-ID: Date: Fri, 5 Sep 2025 16:58:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] mm/huge_memory: fix shrinking of all-zero THPs with max_ptes_none default To: Usama Arif , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song References: <20250905141137.3529867-1-david@redhat.com> <06874db5-80f2-41a0-98f1-35177f758670@gmail.com> <1aa5818f-eb75-4aee-a866-9d2f81111056@redhat.com> <8b9ee2fe-91ef-4475-905c-cf0943ada720@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: <8b9ee2fe-91ef-4475-905c-cf0943ada720@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: -LwfnP-1qVa3r_FgOo76wYcZ0vRdcj4bao2s4CNocaU_1757084339 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 8E0BD18000F X-Stat-Signature: cwza1ew83cdoidgdmeyy1w5s6rzm3unc X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1757084341-848074 X-HE-Meta: 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 oPZk5/JL L8y67xSCPPscYaSb1vHQzQA6YmQx98fPuQVdR+tF/babaWmSaHQdlPZA5mNdRvC5PyDb43IjEfHYFqWSVHcP/T8GD3GLVAXH/aLgHo7HedUXa4mSZimJgdDzIwcYeVjsgjbQLAOq5+8nQRMI7OHP+dWTgJ5XAkQ0NQpHk7/PZJ7qX/FPRnGpTWGZQ0q3S6Owz6vsY7OdGJg0r3jpg5yldJD5TAr0VAt/1TvybePGx1diE7DC0R4x+dcxgDudf/slGdtun0IsyfOR4vqMmvhtFEn1LDs92asvk9SdR9/+qnfOjL7V5qtUZ2mz7I5smJN7bgCBqGlLjGQdJwjws5AHz/IVqeXk6Ip8pJdfuZN53VNiwnnqI/HsqBVS1IPBadHHyawxpMEwtQK74wlU8OJpJmQUSJlbNjCQI9WKBm5UKQXbSB5+lDOCCxT/XKg+xCMOgjAi7sZQPj/ZDdIgF1LGUk/0TEqljwn/J0MG3 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 05.09.25 16:53, Usama Arif wrote: > > > On 05/09/2025 15:46, David Hildenbrand wrote: >> [...] >> >>> >>> The reason I did this is for the case if you change max_ptes_none after the THP is added >>> to deferred split list but *before* memory pressure, i.e. before the shrinker runs, >>> so that its considered for splitting. >> >> Yeah, I was assuming that was the reason why the shrinker is enabled as default. >> >> But in any sane system, the admin would enable the shrinker early. If not, we can look into handling it differently. > > Yes, I do this as well, i.e. have a low value from the start. > > Does it make sense to disable shrinker if max_ptes_none is 511? It wont shrink > the usecase you are describing below, but we wont encounter the increased CPU usage.> I don't really see why we should do that. If the shrinker is a problem than the shrinker should be disabled. But if it is enabled, we should be shrinking as documented. Without more magic around our THP toggles (we want less) :) Shrinking happens when we are under memory pressure, so I am not really sure how relevant the scanning bit is, and if it is relevant enought to change the shrinker default. -- Cheers David / dhildenb