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[2003:d8:2f03:5b00:f549:a879:b2d3:73ee]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-450d7f8f194sm20295615e9.4.2025.05.30.07.39.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 May 2025 07:39:22 -0700 (PDT) Message-ID: <253705b2-a9bb-47a0-94e5-1aeafcca0396@redhat.com> Date: Fri, 30 May 2025 16:39:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC Patch 0/5] Make anon_vma operations testable To: Wei Yang Cc: Lorenzo Stoakes , akpm@linux-foundation.org, riel@surriel.com, vbabka@suse.cz, harry.yoo@oracle.com, jannh@google.com, baohua@kernel.org, linux-mm@kvack.org References: <8c268ece-71a7-470a-bf8b-71d3e4920977@redhat.com> <20250429235608.yvbcxybkfsmp6ow5@master> <20250514012318.2impqotf65p4ihsc@master> <20250527063428.4ykrdtive2hfnqdp@master> <40dc48f9-94d7-46b0-83ed-d3511789c15a@redhat.com> <20250530021112.6b2ldosl3hvhcnvq@master> <20250530140521.tnyjxdsy6qa6dokl@master> 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: <20250530140521.tnyjxdsy6qa6dokl@master> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 1TP-qPFcCOtlyhRU9qnqFWtZWmxOMP9Hg4CshlQiUC8_1748615963 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: q3q8otxpnawq1puptwbifrqbwtpsxnp6 X-Rspamd-Queue-Id: AE8F3100011 X-Rspamd-Server: rspam11 X-HE-Tag: 1748615966-394473 X-HE-Meta: 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 isxZATRW 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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 30.05.25 16:05, Wei Yang wrote: > On Fri, May 30, 2025 at 10:00:18AM +0200, David Hildenbrand wrote: > [...] >>>> >>>> Thanks for reminding me and sorry for the late reply. >>>> >>>>> >>>>>>>> I am trying to understand what scenarios you want. >>>>>>> >>>>>> >>>>>> Sorry for the late reply, I handled other things a while. >>>>>> >>>>>>> That is exactly the task to figure out: how can we actually test our rmap >>>>>>> implementation from a higher level. The example regarding fork and migration >>>>>>> is possibly a low-hanging fruit. >>>>>> >>>>>> If my understanding is correct, you suggested two high level way: >>>>>> >>>>>> 1. fork + migrate (move_pages) >>>> >>>> Yes, that should be one way of testing it. We could even get multiple child >>>> processes into place. >>>> >>>>>> >>>>>>> >>>>>>> We might already have the functionality to achieve it, *maybe* we'd even want >>>>>>> some extensions to make it all even easier to test. >>>>>>> >>>>>>> For example, MADV_PAGEOUT is refused on folios that are mapped into multiple >>>>>>> processes. Maybe we'd want the option to *still* page it out, just like >>>>>>> MPOL_MF_MOVE_ALL allows with CAP_SYS_NICE to *still* migrate a folio that is >>>>>>> mapped into multiple processes. >>>>>>> >>>>>> >>>>>> 2. madvise(MADV_PAGEOUT) >>>>>> >>>>>> Not fully get it here. You mean fork + madvise(MADV_PAGEOUT) + migrate ? >>>> >>>> fork + madvise(MADV_PAGEOUT) only. >>>> >>>> Then verify, that it was actually paged out. >>>> >>>> For example, we could have 10 processes mapping the page, then call >>>> madvise(MADV_PAGEOUT) from one process. We can verify in all processes if the >>>> page is actually no longer mapped using /proc/self/pagemap >>>> >>> >>> Hi, David >> >> Hi! >> >>> >>> I'd like to clarify some detail here. >>> >>>> We could likely do it with anon pages (swap), shmem pages (swap) and >>>> pagecache pages (file backed). >>>> >>> >>> I could understand the three cases here, but for the (swap) case, it is not >>> clear to me. You mean we force the page to be swapped out before migration? I >>> may not have an idea to ensure that. >> >> No need to involve migration for that test. It's sufficient to trigger >> pageout to then check if the page was unmapped in all other processes. >> > > Here you mean for all anon/shmem/pagecache pages, we could have two category > tests: > > * migrate and write different data from on process, verify each process see > new data > * trigger pageout from one process, verify each process has it pageout > (/proc/self/pagemap) > > While one of these category is enough, right? Just like KSM below, migrate or > pageout. Both cases will trigger different code paths: for example, migration will trigger restoring of migration entries, which is a different rmap operation not triggered by pageout/pagein :) Pageout is probably easier to implement: but we couldn't test hugetlb. With migration we probably could also test hugetlb rmap code (yet another case we should probably cover). -- Cheers, David / dhildenb