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[2003:cb:c709:a00:7d7d:3665:5fe4:7127]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f259fe1efsm3976063f8f.97.2025.02.14.00.08.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 Feb 2025 00:08:19 -0800 (PST) Message-ID: <37363b17-88b0-4ccc-a115-8c9f1d83a1b5@redhat.com> Date: Fri, 14 Feb 2025 09:08:18 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/hugetlb: wait for hugepage folios to be freed To: yangge1116@126.com, 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> 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: <1739514729-21265-1-git-send-email-yangge1116@126.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: IGBgrvgJP32xZ_ZLO_q4eRPGrKJ-_SFj3R-xfI7TAd0_1739520501 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 57E0840009 X-Stat-Signature: ki6xzjf7qti1ckykw3wbmx7gkh3omowe X-Rspam-User: X-HE-Tag: 1739520504-373737 X-HE-Meta: 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 qe7dRXuR xIHvhS2G8g9idHZYomBGFl26rGVSUdVCrbKEZWwMGTLxDQIz0ZKcUXLetB/MTYAPLQWtT8ZH77EgwD4KJsB5D0QO4vYx+qs2kEyuSt9XQLCKnbSQM+OJImdeIng00Sqed72SGYojIqml8pO42H0gzc4ftBlYFwXdtvpYEFxQM7gqLrgiuWvqAaYT+QS+LHe8tPSDxRuXV4hHN5zE0n1njxEz1hbzMDw7IxKKzL+Nbyw9rgKcdy9nh1Cw4ulMRJluj/fk0LwNBigxNbFItgZs/7V777YZaWJyZg9ZdJcZqF/XwG7T+k05Hp5rVYHKcbD7nKjQ26y60e5akYM3ZJCeWLdSjrDgrUEmPUVXGndN7LSdcvoRHVzj2EpmAzgmNjEGF6XPyQdUPTdUXcJImR/S8uMquqmYtexP3s+Tzcqut/604ia6zdUo1JJx117kAlmjjQVxXkZb8vIh30X4= 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 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. I wonder if that waiting should instead be done exactly once after migrating multiple folios? For example, at the beginning of test_pages_isolated(), to "flush" that state from any previous migration? Thanks for all your effort around making CMA allocations / migration more reliable. -- Cheers, David / dhildenb