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b=V1Qzz8akwmKUrJKZDa3ABXy2/zDM4ePMvZenwIU0WMpcDE3Ch8xofqBUsbsYxkW1s Y2sg/oP94KjlL6HMg1u4LE1RmXL416fCHXvqY7lpDWCYbhYAIL7vwD2cBYg4KEYaZ1 cbRPt+LVcun+IvD4lmPR1oQSMi/oM2NKGU1osgrH/+jMm/HC28tB3MJrVXzgqCQh/P YOkcdjDVrNrq0KB21iVsuN+l2zEcf0Vkp+nLHMFFMLsKl6C/bfnzMOebIYNSgaQJhB jKXI30eZVMXJu62cRwYI2dXU56Vr7RKjsLHziZHvQV4xJB/iasVz3Ji4dsuuf9y91Y XS/CQ4jAWHIzg== Message-ID: <014f3c0a-7c6f-4f64-95cd-b7b69d804880@kernel.org> Date: Tue, 28 Apr 2026 10:12:16 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [LSF/MM/BPF TOPIC] Using BPF in MM To: Roman Gushchin , bpf , linux-mm , Vlastimil Babka Cc: Shakeel Butt , Andrew Morton , lsf-pc , Daniel Borkmann References: <7ia4o6j4c5y1.fsf@castle.c.googlers.com> 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: <7ia4o6j4c5y1.fsf@castle.c.googlers.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 1nc3uu5596uuxpruigg9mk1hb8dx8tda X-Rspamd-Queue-Id: 9A182140002 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1777363942-545118 X-HE-Meta: U2FsdGVkX18yOW8PUwiREqwE6ls04lFCDhnTQIJDZX8MhR2DwuK+krFfPTAegt/MH9NtUEd+4DNzzf4F9Yqcf9npcn+uLo4qNj5lGQ56nMqdJz7bBzv18/As0oWlCL+EoGK+J3gC8k/Q/N5XRjL+M0OlGXSAvO7cJDiCtcxlPCPjN1s0d272UzyVsM//enVRnMQoAdLO+MNiwLF/pdQQ+yM6ADm+QPXsfCwSmR5S/1q1pBHarsvaUZGue03MMwvWvtnIkbBBpidoW2lhPcMp7bvmxMOkUQnGLKuFYBEMIfKse/8eas+cqApUF1F+jDetSt8sRt7pNUlRJmL6MQjq5IIdoGC/QubCWKH+6dA/o+ADpm8n0tf+GrIoPQWXZ2Jq6avO2eka5yGEylyRAcXN4w4r/+7Ne99+3clUizn5ZBR6udBSWm2hxw7ZP/BvpFw0zHfMtS989V/z4+uQJjqD9hfTlAY6jeHOub6o849mG768g4erQ/7+87aWY90TJHEWu4Ql37NGSMia8ER4zCuOD9peFU3iWBz8+Vw73PEaN63nj89dDft+WIoGjlRf3HuwKIwwdLPW5CVB6MtbMiiJPl7TbElLokb+y3XWgPb3EFaRfaO3Ec59e28UIFOIBq3SZy9JfgYH+D2AfarFt+ecjip3F3rODx7mSiIT+uhf1LlzeoLGPd+JntIIDZM4w7g9asaz+fUqhJ1xNUXyfAqHf99Jyn2erwss6mHeF8UQnhJc/EXnNq/IBndA0EOIeZqlqAhwzwk6WeUaYPWcPbi4htWjclxsjPt+VCm/59u6ymTmd8P3Ms3FrOKx345pRGCNwkZtisCgK+X9Bowa67u9+G0BCnlZFcWP/v2XOazx28ZlUFvA64Ft7juWeTa8z+9xCQrC0WmVD7uy099+kZKDJBumuqEou2hq+QAruhTJwnUzK0dp2SiucsmC4PORCgkN0sR88P28H3xg23/yCuP mYn3o+y2 VQj7CLq4NZ0NxMxRTRtGpRWXGqmj9T+k4qUfT6DFaeKcpuSCDhK/7igirlt+OW0GtVz5MIORvsepBgq77kQ3Pia+7RekCZfcqJ2I9tz8oHh6tBM6VezY1E6rX/rytnq74pN763T/uGnTke6OILdlJFS6902Fh9OeyZt3+dbNh1LkmVEGeZ5GJ86o7SCNguJcb5Zk97NfAuEEaWITYN0Ycf1brxQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/28/26 01:57, Roman Gushchin wrote: > [LSF/MM/BPF TOPIC] Using BPF in MM > ---------------------------------- > > Over the last decade, BPF successfully penetrated into multiple kernel > subsystems: started as a feature to filter (out) networking packets, > it captured its place in networking, tracing, security, HID drivers, > and scheduling. Memory management is a logical next step, and recently > we saw a growing number of proposals in this area. > > In (approximately) historical order: > - BPF OOM > - BPF-based memcg stats access (landed) > - BPF-based NUMA balancing > - eBPF-mm > - cache_ext (BPF Page Cache) > - memcg_ext There was also the BPF THP control. > > There are some obvious target which haven't been covered yet: > - BPF-driven readahead control > - BPF-driven KSM > - BPF-driven guest memory control > > Despite a large number of suggestions only a relatively small feature > (query memcg statistics from BPF) made it to upstream. > > It looks like using BPF in the MM subsystem comes with a set of somewhat > unique challenges and questions to be answered. [...] I think you are missing one of the most important points: Unclear ABI stability guarantees. One the one hand, we are told that there are no ABI stability guarantees, and that we can change hooks (add/remove/modify) any time we want. On the other hand, as soon as there is some ebpf program out there that we break, you can rest assured that there will be trouble. In the area of THP, where we don't even know which hooks we will need long term and how they would look like, that was one of the reasons why the BPF THP control was rejected. -- Cheers, David