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b=Qpi4KKNXGcN58BJXlD58i5Xlxu6vbfqPhXibd9sFp/0BeN1+aY+vOK/C7xbEORQaN FnguCTSycv3dR2Edh4bCbAsdRtGNZfITNUQbrjSg+xBlrbyRwP4HxtX7kMqFG7hnk2 ZCGA8oeP6h4wsfNS7+r/sueekLbwjyiaUMw1Ku6Ko258CF0sH8Hcc54/lMdR41A6e/ qNhiRD0kinDKblm8pQ50/n6nDC+G/dQ7Zd6oK7PEnyWgADOBXlcnV+oI8R7WumXMrY tAcsQI9wexgSOWBDj+Xqo2q7xtfRNEkLmUke5JHFhIdB38YFbGUv5S2axnYAlcXoLV oI5JXgBRH2brg== Message-ID: Date: Tue, 12 May 2026 11:28:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/3] use vma locks for proc/pid/{smaps|numa_maps} reads To: Suren Baghdasaryan , akpm@linux-foundation.org Cc: liam@infradead.org, ljs@kernel.org, vbabka@kernel.org, willy@infradead.org, jannh@google.com, paulmck@kernel.org, pfalcato@suse.de, shuah@kernel.org, hsukrut3@gmail.com, richard.weiyang@gmail.com, reddybalavignesh9979@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20260426062718.1238437-1-surenb@google.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: <20260426062718.1238437-1-surenb@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 65D74180007 X-Stat-Signature: 3y5fq4uou3bjyoiio69y1681ebbe6dhw X-HE-Tag: 1778578106-608361 X-HE-Meta: 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 sSNDg1lK xzsFKmJTX7YDrd7j54dn19GnGuD0rWh2NuUOYyhU3QyniA4RhbOA5PT3plRt13bCALdLgcOzWkhWNIFiXfLaLbaxYlCrP7vOCNgocW1Mb+oml3Epdo/9G6CqviXCKtuzuPP8f/rKPgiIakjwdo+NjOUYEwwwI6znGNIVTRKTyc4gsPP1iNQYRUf/nkHWwvF06XM9dnu3AIk5UKJIxuZsSC2U6jPqngmcq4wpr7xS7psnkbVa0+rvvsGFEaSO0YntTJ5Natw8t45FicmVZyUBwL4soOFpH/3nSVzydtLwDd+J1FY4QMEovQwbF8VGZQv62uXqeaWFAiO9psZW68GB/LuhTMaDDFm65YqMjz/2vLUsmbe+9kPkBEapDHNhnn+j4OkEPbJKUdYbNyJRWfaWI7cfTww== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/26/26 08:27, Suren Baghdasaryan wrote: > Use per-vma locks when reading /proc/pid/smaps and /proc/pid/numa_maps > similar to /proc/pid/maps to reduce contention on central mmap_lock. One > major difference between maps and smaps/numa_maps reading is that the > latter executes page table walk which can't be done under RCU due to a > possibility of sleeping. Therefore we drop RCU read lock before this walk > while keeping the VMA locked. After the walk we retake RCU read lock, > reset VMA iterator and proceed with the next VMA. With many small VMAs, is that overhead noticable? -- Cheers, David