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(p200300d82f4efd008e13e3b590c81159.dip0.t-ipconnect.de. [2003:d8:2f4e:fd00:8e13:e3b5:90c8:1159]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a6d1189977sm9378431f8f.82.2025.06.23.06.49.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Jun 2025 06:49:06 -0700 (PDT) Message-ID: Date: Mon, 23 Jun 2025 15:49:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] selftests/mm: add test for (BATCH_PROCESS)MADV_DONTNEED To: Lorenzo Stoakes , wang lian Cc: Andrew Morton , Shuah Khan , Christian Brauner , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, SeongJae Park , zijing.zhang@proton.me, ryncsn@gmail.com, p1ucky0923@gmail.com, gkwang@linx-info.com, "Liam R. Howlett" , Vlastimil Babka , Jann Horn References: <20250621133003.4733-1-lianux.mm@gmail.com> <8fb737cc-ba83-4949-b4fb-2a2e1af0967a@lucifer.local> 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <8fb737cc-ba83-4949-b4fb-2a2e1af0967a@lucifer.local> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: s_NxU0rtHGekGY_xnkacDW6SD1944jyPAyv-ehFAa-M_1750686548 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: nu4rar4zsg596cqbepd8j14tetfm7qru X-Rspamd-Queue-Id: DAADD40009 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1750686550-714357 X-HE-Meta: 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 OPaxRz29 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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 23.06.25 14:35, Lorenzo Stoakes wrote: > +cc Liam, David, Vlastimil, Jann > > (it might not be obvious from get_maintainers.pl but please cc > maintainers/reviewers of the thing you are adding a test for, thanks!) > > Overall I'm not in favour of us taking this patch. > > There are a number of issues with it (explained inline below), but those aside, > it seems to be: > > - Checking whether a simple anon buffer of arbitrary size is zapped by > MADV_DONTNEED. > > - Printing out a dubious microbenchmark that seems to be mostly asserting that > fewer sycalls are faster when using process_madvise() locally. > > And I'm struggling to see the value of that. We have other tests that should already severely break if MADV_DONTNEED doesn't work ... but sure, we could think about more elaborate functional tests when they provide a clear benefit. (zapping all kinds of memory types, anon/ksm/huge zeropage/pagecache/hugetlb/ ... and using /proc/self/pagemap to see if the page table mappings are already gone) I don't think we have a lot of process_madvise selftests, right? hugtlb handling that was added recently is already tested to some degree in hugetlb-madvise.c. In general, I'm not a fan of selftests that measure syscall performance ... -- Cheers, David / dhildenb