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[80.187.83.189]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-426ce57ccb1sm19843079f8f.8.2025.10.13.12.59.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Oct 2025 12:59:01 -0700 (PDT) Message-ID: <26a8f0aa-8d67-47ba-841c-2daf7010a2aa@redhat.com> Date: Mon, 13 Oct 2025 21:58:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Regerssion] [KSM] KSM CPU overhead in 6.16+ kernel compared to <=6.15 versions ("folio_walk_start" kernel object overhead) To: craftfever@murena.io Cc: akpm@linux-foundation.org, chengming.zhou@linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, regressions@lists.linux.dev, xu.xin16@zte.com.cn References: <80b153cd-8bba-4bcd-9b56-3b2ad3f295e1@redhat.com> <46d26246-5bd5-43f7-b1a4-dc721f717413@airmail.cc> 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: <46d26246-5bd5-43f7-b1a4-dc721f717413@airmail.cc> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: oZ2ULjOgs5FYfHqKo0-VESSnBit4O5fOi4cCEevML5U_1760385542 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: hxrnrsisqxtcd6pnadfs4rpbq49kbw83 X-Rspamd-Queue-Id: 46BEAA0009 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1760385545-153204 X-HE-Meta: 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 S1Qal8K1 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 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 13.10.25 21:54, craftfever wrote: > > Unfortunately, yes I can reproduce it. And I thought that lockups does > not happen anymore, but I was wrong, I booted today with 6.17.2 updated > and KSM enabled and whole situation is back. But, it only happens, when > scanning pages corresponding to a process with huge VM size, like > Chromium with 1TB of virtual memory. The rest is alright. It's look > like, that the folio_walk_start called with much higher frequency, than > in 6.12-6.15 versions. in that version page scanning of huge VM size > processes is pretty fast and flawless) Right now, when Chromium is > running, I expecting constant 42% folio_walk_start and 15% > ksm_scan_thread on 6.17.2 kernel (contrary to 1% folio_walk_start and > even less ksm_scan_thread in 6.12-6.15). I must admin that whole system > is not freezing, just Chromium with high CPU usage from ksmd and kernel. What about 6.16? -- Cheers David / dhildenb