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(p200300cbc716c800ed2f91bf8c467078.dip0.t-ipconnect.de. [2003:cb:c716:c800:ed2f:91bf:8c46:7078]) by smtp.gmail.com with ESMTPSA id g21-20020a05600c311500b0040b3645a7c2sm2547551wmo.40.2023.11.23.08.50.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Nov 2023 08:50:53 -0800 (PST) Message-ID: <7d4efbe8-5690-4db0-be06-399353679982@redhat.com> Date: Thu, 23 Nov 2023 17:50:52 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RESEND PATCH v7 00/10] Small-sized THP for anonymous memory To: Matthew Wilcox Cc: Ryan Roberts , Andrew Morton , Yin Fengwei , Yu Zhao , Catalin Marinas , Anshuman Khandual , Yang Shi , "Huang, Ying" , Zi Yan , Luis Chamberlain , Itaru Kitayama , "Kirill A. Shutemov" , John Hubbard , David Rientjes , Vlastimil Babka , Hugh Dickins , Kefeng Wang , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20231122162950.3854897-1-ryan.roberts@arm.com> <7f76ee6c-f0e6-443b-bcff-3637895dec66@redhat.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: 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: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 2692D180020 X-Stat-Signature: 7eaopiotxbbfhxmj9faje1s73m9mfi5e X-HE-Tag: 1700758257-776013 X-HE-Meta: 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 Z/rITlP6 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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 23.11.23 17:18, Matthew Wilcox wrote: > On Thu, Nov 23, 2023 at 05:05:37PM +0100, David Hildenbrand wrote: >> On 23.11.23 16:59, Matthew Wilcox wrote: >>> On Wed, Nov 22, 2023 at 04:29:40PM +0000, Ryan Roberts wrote: >>>> Note: I'm resending this at Andrew's suggestion due to having originally sent >>>> it during LPC. I'm hoping its in a position where the feedback is minor enough >>>> that I can rework in time for v6.8, but so far haven't had any. >>>> >>>> Hi All, >>>> >>>> This is v7 of a series to implement small-sized THP for anonymous memory >>>> (previously called "large anonymous folios"). The objective of this is to >>> >>> I'm still against small-sized THP. We've now got people asking whether >>> the THP counters should be updated when dealing with large folios that >>> are smaller than PMD sized. It's sowing confusion, and we should go >>> back to large anon folios as a name. >>> >> >> I disagree. >> >> https://lore.kernel.org/all/65dbdf2a-9281-a3c3-b7e3-a79c5b60b357@redhat.com/ > > And yet: > https://lore.kernel.org/linux-mm/20231106193315.GB3661273@cmpxchg.org/ > > "This is a small THP so we don't account it as a THP, we only account > normal THPs as THPs" is a bizarre position to take. > > Not to mention that saying a foo is a small huge baz is just bizarre. > Am I a small giant? Or just a large human? I like that analogy. Yet, "small giant" sounds "bigger" in some way IMHO ;) I'll note that "small-sized THP" is just a temporary feature name, it won't be exposed as such to the user in sysfs etc. In a couple of years, it will be forgotten. To me it makes sense: it's a hugepage (not a page) but smaller compared to what we previously had. But again, there won't be a "small_thp" toggle anywhere. Long-term it's simply going to be a THP. Quoting from my writeup: "Nowadays, when somebody says that they are using hugetlb huge pages, the first question frequently is "which huge page size?". The same will happen with transparent huge pages I believe.". Regarding the accounting: as I said a couple of times, "AnonHugePages" should have been called "AnonPmdMapped" or similar; that's what it really is: as soon as a THP is PTE-mapped, it's not accounted there. But we can't fix that I guess, unless we add some "world switch" for any workloads that would care about a different accounting. So we're really only concerned about: * AnonHugePages * ShmemHugePages * FileHugePages The question is if we really want to continue extending/adjusting the old meminfo interfaces and talk about how to perform accounting there. Because, as we learned, we might get a new file-based sysfs based interface, because Greg seems to be against exposing new values in the old single-file-based one. In a new one, we have all freedom to expose what we actually want nowadays, and can just document that the old interface was designed with the assumption that there is only a single THP size. ... like hugetlb, where we also only expose the "default hugetlb size" parameters for legacy reasons: HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB -- Cheers, David / dhildenb