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[2003:cb:c74b:d000:3a9:de5c:9ae6:ccb3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-432da265ca8sm202073895e9.14.2024.11.19.08.49.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 19 Nov 2024 08:49:14 -0800 (PST) Message-ID: <833078e4-3661-451a-bc11-3cb60a302946@redhat.com> Date: Tue, 19 Nov 2024 17:49:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v2 1/3] mm/contig_alloc: support __GFP_COMP To: Zi Yan Cc: Yu Zhao , Andrew Morton , Muchun Song , "Matthew Wilcox (Oracle)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240814035451.773331-1-yuzhao@google.com> <20240814035451.773331-2-yuzhao@google.com> <402ff3e5-4fca-4452-97ba-5b1ec4a6eeb1@redhat.com> <00721702-78FF-4690-8EAA-31C367FA9FC0@nvidia.com> <1a77f16b-d637-40b4-bf47-a8236729a0ca@redhat.com> <57A6BDB9-119B-4C1F-8715-2584046A5EA8@nvidia.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: <57A6BDB9-119B-4C1F-8715-2584046A5EA8@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: rSlKp-uvxjEVWMjwEucd2GXb8O-aa3E0SdCMdjn-N6A_1732034955 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: fu65oy3dry1bcbocu7jt7f45pt1a78rc X-Rspamd-Queue-Id: B3076100009 X-Rspamd-Server: rspam08 X-Rspam-User: X-HE-Tag: 1732034902-941305 X-HE-Meta: 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 nhOm5Dlv ORSM05uxAaqtxSrY85mjfDbWfIYhRsky8FMZfHgUEeVvgMXhOY250gxidRpt03NN3YgKhOPdChk8PTRRUA8SUvYUsOA3jSySMirb0L5exA78IZIgrjOet6pNvaRjC88kQ4tJJkrJ6mpN4kBLkhSTj6lkOGsLj8D1TS2ucLlhAqmPm8Rmk0a1ZRZEIyetkxJ0lC13RkfUChY1zsf9Q3uoK1twehNAUrnji4T2AsvPXiSlFCxgoBlOc34o1YDgoXRk+Tk/N8wtX3sgjNxT8pbb0xyUy/PeRggQvHPOrJS3wDG2I+xB//VGfmG4jbvAPCW3+jaWCYpSZNW7zs3Z/JTHoOvRhprL2Fu58kYJipQV4dPPxUAgywoEAhMkc5eyfX2q2VTJbp3FYweZ9bNXdPVY5K11u7w5Ko+Qj/L9iGE48oo+lekpNctD80ervyFYc8V6KC/eb 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 19.11.24 17:41, Zi Yan wrote: > On 19 Nov 2024, at 11:31, David Hildenbrand wrote: > >> On 19.11.24 17:12, Zi Yan wrote: >>> On 19 Nov 2024, at 10:29, David Hildenbrand wrote: >>> >>>>> +/* Split a multi-block free page into its individual pageblocks. */ >>>>> +static void split_large_buddy(struct zone *zone, struct page *page, >>>>> + unsigned long pfn, int order, fpi_t fpi) >>>>> +{ >>>>> + unsigned long end = pfn + (1 << order); >>>>> + >>>>> + VM_WARN_ON_ONCE(!IS_ALIGNED(pfn, 1 << order)); >>>>> + /* Caller removed page from freelist, buddy info cleared! */ >>>>> + VM_WARN_ON_ONCE(PageBuddy(page)); >>>>> + >>>>> + if (order > pageblock_order) >>>>> + order = pageblock_order; >>>>> + >>>>> + while (pfn != end) { >>>>> + int mt = get_pfnblock_migratetype(page, pfn); >>>>> + >>>>> + __free_one_page(page, pfn, zone, order, mt, fpi); >>>>> + pfn += 1 << order; >>>>> + page = pfn_to_page(pfn); >>>>> + } >>>>> +} >>>> >>>> Hi, >>>> >>>> stumbling over this while digging through the code .... >>>> >>>>> + >>>>> static void free_one_page(struct zone *zone, struct page *page, >>>>> unsigned long pfn, unsigned int order, >>>>> fpi_t fpi_flags) >>>>> { >>>>> unsigned long flags; >>>>> - int migratetype; >>>>> spin_lock_irqsave(&zone->lock, flags); >>>>> - migratetype = get_pfnblock_migratetype(page, pfn); >>>>> - __free_one_page(page, pfn, zone, order, migratetype, fpi_flags); >>>> >>>> This change is rather undesired: >>>> >>>> via __free_pages_core()->__free_pages_ok() we can easily end up here with order=MAX_PAGE_ORDER. >>> >>> Do you have a concrete example? PMD THP on x86_64 is pageblock_order. >>> We do not have PMD level mTHP yet. Any other possible source? >>> >>>> >>>> What your new code will do is split this perfectly reasonable MAX_PAGE_ORDER chunk via split_large_buddy() into pageblock-sized chunks, and let the buddy merging logic undo our unnecessary splitting. >>>> >>>> Is there a way to avoid this and just process the whole MAX_PAGE_ORDER chunk like we used to? >>> >>> Probably split_large_buddy() can check the migratetypes of the to-be-freed >>> page, if order > pageblock_order. If all migratetypes are the same, the page >>> can be freed at MAX_PAGE_ORDER, otherwise pageblock_order. >> >> Thinking about this: why do we care about the migratetype? >> >> We only have to fallback to pageblocks if any pageblock is "MIGRATE_ISOLATE" (and maybe MIGRATE_CMA), but not all. Otherwise, we can just ignore the migratetype (or rather overwrite it) > > There are VM_WARN_ONCEs around *_free_list() operations to make sure > page migratetype matches the migratetype of the list it is on. Ignoring > migratetype would trigger these WARNs. Overwriting it would work but > free page migratetype accounting needs to be taken care of. > > An implicit reason is that __free_one_page() does not support >MAX_PAGE_ORDER > and gigantic hugetlb folios are freed via free_one_page(), where > split_large_buddy() is used to work around the limitation. Yes, I saw that change. But that can be easily identified cased by unlikely(order > MAX_PAGE_ORDER) to handle that rare case in a special way. > > For the two memory init cases you mentioned in the other email, maybe a new > fpi flag to make free_one_page() use __free_one_page() for them, > since migratetypes should be the same across MAX_PAGE_ORDER range there, right? In the context of alloc_frozen_range()/free_frozen_range() I want to free MAX_PAGE_ORDER chunks when possible, and not have some odd logic in the freeing path undo some of that effort. In the common case, the pageblocks will all have the same time when freeing a MAX_PAGE_ORDER page, so we should identify the odd case and only special-case that. -- Cheers, David / dhildenb