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[2003:cb:c731:3d00:918f:ce94:4280:80f0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-35dd04c0f1fsm9769182f8f.15.2024.06.03.13.43.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 Jun 2024 13:43:52 -0700 (PDT) Message-ID: <9fa4f1be-790c-4823-aff2-f864807759f1@redhat.com> Date: Mon, 3 Jun 2024 22:43:51 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: increase totalram_pages on freeing to buddy system To: Wei Yang Cc: rppt@kernel.org, akpm@linux-foundation.org, osalvador@suse.de, linux-mm@kvack.org References: <20240601133402.2675-1-richard.weiyang@gmail.com> <0316a276-a0d8-4fc2-ad67-0d4732b6d89b@redhat.com> <20240602005820.2uk23ot4mskfl5sl@master> <8297c4d3-f97b-4923-9b27-19294fa130eb@redhat.com> <20240603200123.bvkttf2yqutecjtv@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: <20240603200123.bvkttf2yqutecjtv@master> 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-Stat-Signature: kgd8wkyec7gepfsh6tha1fmqp7zprtmh X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E687980012 X-HE-Tag: 1717447436-735644 X-HE-Meta: U2FsdGVkX18pnXa5GHwYXg44RbUCIuPqyocW+p0jtPjY6unOW/u8CfDG6hbEWnTSWejVgECN4wt8Y1F8AJPHMVoOFY+bsFnmJ3R8iBcazX+ljHOSkyyl/j3IvtPFYmIgH3mhqE1ZCqgF/W8YZFS0ukJGOz8Y3hvVrL6KUxYSEKGR4/ZWOZ10j312XiZRaAp6/U1C9JjRR6hghf0uKIphajQ8vg4xP+qYABLuW02a5MpTkxid9uFiFfwlkIprGV1mGEHET9QDUhSelG3s0yoUPaA8Z037OzmSoqDG/jnRHSvOPWvPlCNWxJDoDisfCjKiNvYoL8Lsr0FnXKLVtTLy61NpdCpCyGeXkz7iXceNco9YFdepdzivzrYYg6m2gviaGn5snj9Zu7GoLdkW6K5cIRaxbA/ucuI8p/KHwdAoJBF4y4pmXzAPiBqtVFHowEd3ym2LnaJNQY4lY+7Vs4pBr2C2LAJz4aGB1mGtajA1ye8AdR0qahYp3z0N075tV8BEmvg1TOvnOGa936xRCWgQ5XQOKV2XOwOg2pORYViDYLYamJ9ZSN7KylWNCpVzpcpy+MfQjhhDFVJaaCs9+Bl9Ir96xZtUFd6g8UIUNn4cSuI2Ap3AKyZA6P1FPo0atTG9UP0PC7fb5yeXLjNeh9nFw7g0D6rFhd339ucZJILrQDe/DRELR1dJRQwRWFh69LUWqqV8caj6K5EIF4EbwUgb5F4YNIteADoUGjLShlTi4uWfZ6q5SvK0To85nxPqBG8UEvmd5VFibWE8Q3veddW01Y2ibJbRG50Jv4w80aFouQfm/q5DhAawIRduk4sZ4nvr9u7asOhDBrrHNNGiDnKvP0nkYicKRxaqYgYXkcclrnLsqDLpIZqbYY5ss/8ce4y9iDBj3BGHqMn2FbXREnepzKq0Q97WqDkxzBopPBQrklYJsj7ZEfEQ6ajoUPEXi9xXhUgQq0bVvaUltmHZSXq TtdtR1D4 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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 03.06.24 22:01, Wei Yang wrote: > On Mon, Jun 03, 2024 at 10:55:10AM +0200, David Hildenbrand wrote: >> On 02.06.24 02:58, Wei Yang wrote: >>> On Sat, Jun 01, 2024 at 06:15:33PM +0200, David Hildenbrand wrote: >>>> On 01.06.24 17:32, David Hildenbrand wrote: >>>>> On 01.06.24 15:34, Wei Yang wrote: >>>>>> Total memory represents pages managed by buddy system. >>>>> >>>>> No, that's managed pages. >>>>> >>>>>> After the >>>>>> introduction of DEFERRED_STRUCT_PAGE_INIT, it may count the pages before >>>>>> being managed. >>>>>> >>>>> >>>>> I recall one reason that is done, so other subsystem know the total >>>>> memory size even before deferred init is done. >>>>> >>>>>> free_low_memory_core_early() returns number of pages for all free pages, >>>>>> even at this moment only early initialized pages are freed to buddy >>>>>> system. This means the total memory at this moment is not correct. >>>>>> >>>>>> Let's increase it when pages are freed to buddy system. >>>>> >>>>> I'm missing the "why", and the very first sentence of this patch is wrong. >>>> >>>> Correction: your statement was correct :) That's why >>>> adjust_managed_page_count() adjusts that as well. >>>> >>>> __free_pages_core() only adjusts managed page count, because it assumes >>>> totalram has already been adjusted early during boot. >>>> >>>> The reason we have this split for now, I think, is because of subsystems that >>>> call totalram_pages() during init. >>>> >>>> So the "why" question remains, because this change has the potential to break >>>> other stuff. >>>> >>> >>> Thanks, I didn't notice this. >> >> I think having your cleanup would be very nice, as I have patches in the >> works that would benefit from being able to move the totalram update from >> memory hotplug code to __free_pages_core(). >> > > I got the same feeling. > >> We'd have to make sure that no code relies on totalram being sane/fixed >> during boot for the initial memory. I think right now we might have such >> code. >> > > One concern is totalram would change when hotplug is enabled. That sounds > those codes should do some re-calculation after totalram changes? We don't have such code in place -- there were discussions regarding that recently. It would be reasonable to take a look at all totalram_pages() users and determine if they could be affected by deferring updating it. At least page_alloc_init_late()->deferred_init_memmap() happens before do_basic_setup()->do_initcalls(), which is good. So maybe it's not a big concern and this separate totalram pages accounting is much rather some legacy leftover. > >> Further, we currently require only a single atomic RMW instruction to adjust >> totalram during boot, moving it to __free_pages_core() would imply more >> atomics: but usually only one per MAX_ORDER page, so I doubt this would make >> a big difference. >> > > I took a rough calculation on this.One MAX_ORDER page accounts for 2MB, and > with defer_init only low zone's memory is initialized during boot. Per my > understanding, low zone's memory is 4GB for x86. So the extra calculation is > 4GB / 2MB = 2K. Well, for all deferred-initialized memory you would now also require these -- or if deferred-init would be disabled. Sounds like an interesting measurement if that would be measurable at all. -- Cheers, David / dhildenb