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[2003:cb:c702:b500:3ed7:a1c7:447e:2279]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4264a21d2adsm53334365e9.29.2024.07.05.02.16.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 Jul 2024 02:16:22 -0700 (PDT) Message-ID: Date: Fri, 5 Jul 2024 11:16:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 0/6] add mTHP support for anonymous shmem To: Ryan Roberts , Baolin Wang , Matthew Wilcox Cc: akpm@linux-foundation.org, hughd@google.com, wangkefeng.wang@huawei.com, ying.huang@intel.com, 21cnbao@gmail.com, shy828301@gmail.com, ziy@nvidia.com, ioworker0@gmail.com, da.gomez@samsung.com, p.raghav@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <27beaa0e-697e-4e30-9ac6-5de22228aec1@redhat.com> <6d4c0191-18a9-4c8f-8814-d4775557383e@redhat.com> <32f04739-0cd0-4a9e-9419-c5a13c333c28@redhat.com> <8d3804ad-14c8-4041-8f52-58fd9dd8d4b4@arm.com> 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: <8d3804ad-14c8-4041-8f52-58fd9dd8d4b4@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: wp1h1o33wbqrz6afouwigja9tojjpo8y X-Rspam-User: X-Rspamd-Queue-Id: 9546C4000B X-Rspamd-Server: rspam02 X-HE-Tag: 1720170988-528556 X-HE-Meta: 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 S1t/Hh1l +GsBx5ov2VhrKNzH5HLJ99GiWaJu2hzqUv8uOF9l6oHj0ybHCrahOvveTpUSiJI6Ky944CQNfNsWFBUe+VfOyHNjgZTThCSWVkr0s6+aobv7QfG888m7Y4HpVhC8vQJMjbfDRDpco+9q5enW1x4hACv6CKOeUqjRMzjJOl5hGURCBZ0E3tC9CWNCFnd39+xlfJe9/N1LIv8yShTkdn5+OS1r8FO2mNKAbHvlowJFPWoCA0NL9+wc1OYDq2DXhbOd6T1Cb7EdOIOGteubARFOL/984BftmAajD2ZKIMiIYwaPLFA8hNLHyUdOFlOS4D4w5DjQ36/5mb3x/BsKJL127Yei3tJjNkl94ZBub8tBYUyFB/zVEMy3BMj2PW+vovSleZggkaHzuEHqwvqBVca33dAHOhYSXZqmU5dcFFmLO2hSKeZ/DMGulu1ERTJF3FP5IJ36cg4sa83plH46wPBtCmifdnrYk93sWHnFp 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 05.07.24 11:13, Ryan Roberts wrote: > On 05/07/2024 09:59, David Hildenbrand wrote: >> On 05.07.24 10:45, Ryan Roberts wrote: >>> On 05/07/2024 06:47, Baolin Wang wrote: >>>> >>>> >>>> On 2024/7/5 03:49, Matthew Wilcox wrote: >>>>> On Thu, Jul 04, 2024 at 09:19:10PM +0200, David Hildenbrand wrote: >>>>>> On 04.07.24 21:03, David Hildenbrand wrote: >>>>>>>> shmem has two uses: >>>>>>>> >>>>>>>>      - MAP_ANONYMOUS | MAP_SHARED (this patch set) >>>>>>>>      - tmpfs >>>>>>>> >>>>>>>> For the second use case we don't want controls *at all*, we want the >>>>>>>> same heiristics used for all other filesystems to apply to tmpfs. >>>>>>> >>>>>>> As discussed in the MM meeting, Hugh had a different opinion on that. >>>>>> >>>>>> FWIW, I just recalled that I wrote a quick summary: >>>>>> >>>>>> https://lkml.kernel.org/r/f1783ff0-65bd-4b2b-8952-52b6822a0835@redhat.com >>>>>> >>>>>> I believe the meetings are recorded as well, but never looked at recordings. >>>>> >>>>> That's not what I understood Hugh to mean.  To me, it seemed that Hugh >>>>> was expressing an opinion on using shmem as shmem, not as using it as >>>>> tmpfs. >>>>> >>>>> If I misunderstood Hugh, well, I still disagree.  We should not have >>>>> separate controls for this.  tmpfs is just not that special. >>> >>> I wasn't at the meeting that's being referred to, but I thought we previously >>> agreed that tmpfs *is* special because in some configurations its not backed by >>> swap so is locked in ram? >> >> There are multiple things to that, like: >> >> * Machines only having limited/no swap configured >> * tmpfs can be configured to never go to swap >> * memfd/tmpfs files getting used purely for mmap(): there is no real >>   difference to MAP_ANON|MAP_SHARE besides the processes we share that >>   memory with. >> >> Especially when it comes to memory waste concerns and access behavior in some >> cases, tmpfs behaved much more like anonymous memory. But there are for sure >> other use cases where tmpfs is not that special. >> >> My opinion is that we need to let people configure orders (if you feel like it, >> configure all), but *select* the order to allocate based on readahead >> information -- in contrast to anonymous memory where we start at the highest >> order and don't have readahead information available. > > That approach is exactly what I proposed to start playing with yesterday [1] for > regular pagecache folio allocations too :) In German, there is this saying "zwei Dumme ein Gedanke". The official English alternative is "great minds think alike". ... well, the direct German->English translation definitely has a "German touch" to it: "two stupid ones one thought" -- Cheers, David / dhildenb