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b=OMtAd4XNinTdl0ZHL7hrsbszQfcdUCVDQz6iSJEQFW077NCCWoGFNnn5EyfGSCgef 0IUMIjbGQpUS6Iw14HaV6M0arD2+BV0E9ZC22WmRgBw2mxL05ilrv4EgV4iO9KK7gS x0PvEJj4dsyHkTCZESkJNOBrOWb+XwxGRTRmMRlswxcvPQjiCvLzJMOY3/ocx0oJa9 ejGzo0+zsG47oIYbCyV7a/wr09t1f1nUws4BnQlFN1iqkugPxMwOqQ+zEXuUnQq5ly pJw8pdefr0UNpcjOtWE7R27NkrYxJ2YnIUclTviqktLYYv/JwVVoyackpSGmFofWW2 L1owvXGehD+Ag== Message-ID: <639f20f3-9e65-4117-af9b-e37af0829847@kernel.org> Date: Wed, 8 Apr 2026 10:09:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC] mm: stress-ng --mremap triggers severe lruvec lock contention in populate/unmap paths To: Pedro Falcato , Joseph Salisbury Cc: Andrew Morton , Chris Li , Kairui Song , Jason Gunthorpe , John Hubbard , Peter Xu , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , linux-mm@kvack.org, LKML References: 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-Rspamd-Queue-Id: 8C80D180003 X-Stat-Signature: imsosthkao77yc9sb6931wn5q6nkamdb X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1775635768-902355 X-HE-Meta: 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 yw9M96g5 3tOLzkDjP/qMuQoSfRs8CNA4EJYk7gfrhKBm8BM2h39BZ6/rUymTXOagAx5O2PdWR+9ec7GEPPn4uYUlKhITxp1oZt6Vx1ITXChfbR3bGAgx48HKfSf0DDsCARuFMaUO70l3KPlvxiDW7nnNOi2npQjXeptR9lw7cBFhMt1mqm5mmwww8jzMKrgk+F2CG7lFDard5W/DDnS0PrOvTXR/u5hZLNgHNlMjGFBpc6B6iiNpuMD19qDQT0MPi/QvlqQBZKn1c Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >> >> It was also found that adding '--mremap-numa' changes the behavior >> substantially: > > "assign memory mapped pages to randomly selected NUMA nodes. This is > disabled for systems that do not support NUMA." > > so this is just sharding your lock contention across your NUMA nodes (you > have an lruvec per node). > >> >> stress-ng --mremap 8192 --mremap-bytes 4K --timeout 30 --mremap-numa >> --metrics-brief >> >> mremap 2570798 29.39 8.06 106.23 87466.50 22494.74 >> >> So it's possible that either actual swapping, or the mbind(..., >> MPOL_MF_MOVE) path used by '--mremap-numa', removes most of the excessive >> system time. >> >> Does this look like a known MM scalability issue around short-lived >> MAP_POPULATE / munmap churn? > > Yes. Is this an actual issue on some workload? Same thought, it's unclear to me why we should care here. In particular, when talking about excessive use of zero-filled pages. -- Cheers, David