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b=Q7q2Q3nGsNvTyv8Vv/aO7WMV5WBRP9gzVxbwrZcs4ayzSXskMzNEZozwOzGNGAcLz gup7R4EMuWdNDDsYUoEaQDeuZu39P+WZvgLnmv6HQfzymHbaANub4skC6zHY+h6JUP EwgneY5LsCpv+u8w4+nonOVGY0wpg8f1BxIXUD0wu3jS5fGUuIRyddFKjTtox2we1H 2PM5zhfZPcAWbGB665+xe5hrX+x1IFMAEM5mZ4mK7ozYUp8foUbLZknMMwEjKOVdSi Bbw6oJzy0siRuFqHaI4ecvcx6En50gaBeb1QQ6swir2EWTD5bq8a5qXOdFQb4eWbBz AGiGv1wjg+9Yg== Message-ID: <28c3ae9f-c974-454c-b8ed-ba0ba0a5706d@kernel.org> Date: Thu, 23 Apr 2026 11:49:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 0/3] mm: process_mrelease: expedited reclaim and auto-kill support To: Michal Hocko , Minchan Kim Cc: akpm@linux-foundation.org, brauner@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, surenb@google.com, timmurray@google.com, Johannes Weiner References: <20260413223948.556351-1-minchan@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 8qjmmubdwwirwi64tfn3a99im33pup4x X-Rspamd-Queue-Id: A4EB24000A X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1776937801-925834 X-HE-Meta: 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 1RZ/XXlN jV2wYD7t/Vw04vN9YRy6ymeADj35QAfDHk0G70s720TkfvkmxzK7YnEoAM2/7nKFuzxBruufJFEiNlRY4Dy0ba6I+WoB6ln7wZa86Wlr8Lt5cPlPeMuXNTq26EPypMisACEHPCxpKag/IivcOFtQOrQWsMDFp1Su8BQGwlS55Ww2y1xj3g+YQ8vWSS3PxvfoA+txZcUTxApQEobtEL2XlQFhg2cn3TrvMAq0NjbNP65b/fZJHSBX6Uaim2/fHNg4mxPzcsoWdPVxCVKzA+w5ccmvenvr8cQvXn1k8ybm0V/cKXN9C2ayq2tlFNA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/23/26 09:50, Michal Hocko wrote: > On Mon 20-04-26 14:53:23, Minchan Kim wrote: >> On Fri, Apr 17, 2026 at 09:11:21AM +0200, Michal Hocko wrote: > [...] >>> Yes. All which make sense, really. I am still not convinced about the >>> clean page cache because that just seems like a hack to workaround wrong >>> userspace oom heuristics. >> >> I see it a bit differently. When paltform decides to kill a process >> to free up memory, they want that memory back right away. >> >> So it doesn't make much sense for the kernel to ignore that and leave the clean >> file pages to be picked up slowly by kswapd later. >> >> In some aspects, you can think of LMKD as a more specialized, userspace version >> of kswapd. It has high-level knowledge of process priorities and knows exactly >> which process is safe to kill to get memory instantly. The kernel's kswapd, >> however, operates globally without this specific process-level awareness, which >> makes it less suited for this kind of targeted reclamation. >> >> If we force LMKD to rely on the slower global kswapd to actually free the clean >> pages, it defeats the whole purpose of targeting a specific process. >> >> So letting process_mrelease speed this up isn't a hack at all. It's just helping >> the kernel do what the admin wanted in the first place: fast, targeted memory. > > This is a very creative/disruptive way to do a memory reclaim. From a > user POV I would much rather see clean page cache reclaimed before my > apps start to disappear. But this is obviously your call and your users > that will care. > > Anyway, I still maintain my position. I do not think it is a good > idea to drop clean page cache as you do not know whether there are other > users. IIRC, Johannes raised in the past the we cannot predict the future. For example, if an app gets OOM-killed, wouldn't we usually try restarting it, re-consuming the clean pagecache pages we would be evicting here? Just a thought. -- Cheers, David