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[91.12.97.162]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f259f8273sm14184140f8f.89.2025.02.18.01.41.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Feb 2025 01:41:57 -0800 (PST) Message-ID: <048ca765-bf44-46ab-87d4-328dc0979159@redhat.com> Date: Tue, 18 Feb 2025 10:41:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/hugetlb: wait for hugepage folios to be freed To: Ge Yang , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, 21cnbao@gmail.com, baolin.wang@linux.alibaba.com, muchun.song@linux.dev, osalvador@suse.de, liuzixing@hygon.cn References: <1739514729-21265-1-git-send-email-yangge1116@126.com> <37363b17-88b0-4ccc-a115-8c9f1d83a1b5@redhat.com> <2d0b01c5-a736-41d5-a0f7-db0da065d049@redhat.com> <406c6713-356b-4acf-bcd0-e5a6c1e9adcf@126.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: <406c6713-356b-4acf-bcd0-e5a6c1e9adcf@126.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: OPpRmCQeBE0sZVN4H8ToAL3s4VsT8XvmnNehlvFFKK0_1739871719 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: C358740010 X-Rspamd-Server: rspam12 X-Stat-Signature: gfzw5iba15amb4zztjyry7cwngcp9gsu X-HE-Tag: 1739871723-840109 X-HE-Meta: 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 TcX0r/ev 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000035, 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 18.02.25 10:22, Ge Yang wrote: > > > 在 2025/2/18 16:55, David Hildenbrand 写道: >> On 15.02.25 06:50, Ge Yang wrote: >>> >>> >>> 在 2025/2/14 16:08, David Hildenbrand 写道: >>>> On 14.02.25 07:32, yangge1116@126.com wrote: >>>>> From: Ge Yang >>>>> >>>>> Since the introduction of commit b65d4adbc0f0 ("mm: hugetlb: defer >>>>> freeing >>>>> of HugeTLB pages"), which supports deferring the freeing of HugeTLB >>>>> pages, >>>>> the allocation of contiguous memory through cma_alloc() may fail >>>>> probabilistically. >>>>> >>>>> In the CMA allocation process, if it is found that the CMA area is >>>>> occupied >>>>> by in-use hugepage folios, these in-use hugepage folios need to be >>>>> migrated >>>>> to another location. When there are no available hugepage folios in the >>>>> free HugeTLB pool during the migration of in-use HugeTLB pages, new >>>>> folios >>>>> are allocated from the buddy system. A temporary state is set on the >>>>> newly >>>>> allocated folio. Upon completion of the hugepage folio migration, the >>>>> temporary state is transferred from the new folios to the old folios. >>>>> Normally, when the old folios with the temporary state are freed, it is >>>>> directly released back to the buddy system. However, due to the >>>>> deferred >>>>> freeing of HugeTLB pages, the PageBuddy() check fails, ultimately >>>>> leading >>>>> to the failure of cma_alloc(). >>>>> >>>>> Here is a simplified call trace illustrating the process: >>>>> cma_alloc() >>>>>       ->__alloc_contig_migrate_range() // Migrate in-use hugepage >>>>>           ->unmap_and_move_huge_page() >>>>>               ->folio_putback_hugetlb() // Free old folios >>>>>       ->test_pages_isolated() >>>>>           ->__test_page_isolated_in_pageblock() >>>>>                ->PageBuddy(page) // Check if the page is in buddy >>>>> >>>>> To resolve this issue, we have implemented a function named >>>>> wait_for_hugepage_folios_freed(). This function ensures that the >>>>> hugepage >>>>> folios are properly released back to the buddy system after their >>>>> migration >>>>> is completed. By invoking wait_for_hugepage_folios_freed() following >>>>> the >>>>> migration process, we guarantee that when test_pages_isolated() is >>>>> executed, it will successfully pass. >>>> >>>> Okay, so after every successful migration -> put of src, we wait for the >>>> src to actually get freed. >>>> >>>> When migrating multiple hugetlb folios, we'd wait once per folio. >>>> >>>> It reminds me a bit about pcp caches, where folios are !buddy until the >>>> pcp was drained. >>>> >>> It seems that we only track unmovable, reclaimable, and movable pages on >>> the pcp lists. For specific details, please refer to the >>> free_frozen_pages() function. >> >> It reminded me about PCP caches, because we effectively also have to >> wait for some stuck folios to properly get freed to the buddy. >> > It seems that when an isolated page is freed, it won't be placed back > into the PCP caches. I recall there are cases when the page was in the pcp before the isolation started, which is why we drain the pcp at some point (IIRC). -- Cheers, David / dhildenb