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[2003:cb:c749:6600:b73a:466c:e610:686]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38a1c832c45sm1910043f8f.32.2024.12.19.08.40.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Dec 2024 08:40:28 -0800 (PST) Message-ID: <0b41cc6b-5c93-408f-801f-edd9793cb979@redhat.com> Date: Thu, 19 Dec 2024 17:40:27 +0100 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] replace free hugepage folios after migration 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, liuzixing@hygon.cn, Oscar Salvador References: <1734503588-16254-1-git-send-email-yangge1116@126.com> From: David Hildenbrand Content-Language: en-US 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: <1734503588-16254-1-git-send-email-yangge1116@126.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 18.12.24 07:33, yangge1116@126.com wrote: > From: yangge CCing Oscar, who worked on migrating these pages during memory offlining and alloc_contig_range(). > > My machine has 4 NUMA nodes, each equipped with 32GB of memory. I > have configured each NUMA node with 16GB of CMA and 16GB of in-use > hugetlb pages. The allocation of contiguous memory via the > cma_alloc() function can fail probabilistically. > > The cma_alloc() function may fail if it sees an in-use hugetlb page > within the allocation range, even if that page has already been > migrated. When in-use hugetlb pages are migrated, they may simply > be released back into the free hugepage pool instead of being > returned to the buddy system. This can cause the > test_pages_isolated() function check to fail, ultimately leading > to the failure of the cma_alloc() function: > cma_alloc() > __alloc_contig_migrate_range() // migrate in-use hugepage > test_pages_isolated() > __test_page_isolated_in_pageblock() > PageBuddy(page) // check if the page is in buddy I thought this would be working as expected, at least we tested it with alloc_contig_range / virtio-mem a while ago. On the memory_offlining path, we migrate hugetlb folios, but also dissolve any remaining free folios even if it means that we will going below the requested number of hugetlb pages in our pool. During alloc_contig_range(), we only migrate them, to then free them up after migration. Under which circumstances doe sit apply that "they may simply be released back into the free hugepage pool instead of being returned to the buddy system"? > > To address this issue, we will add a function named > replace_free_hugepage_folios(). This function will replace the > hugepage in the free hugepage pool with a new one and release the > old one to the buddy system. After the migration of in-use hugetlb > pages is completed, we will invoke the replace_free_hugepage_folios() > function to ensure that these hugepages are properly released to > the buddy system. Following this step, when the test_pages_isolated() > function is executed for inspection, it will successfully pass. > > Signed-off-by: yangge > --- > include/linux/hugetlb.h | 6 ++++++ > mm/hugetlb.c | 37 +++++++++++++++++++++++++++++++++++++ > mm/page_alloc.c | 13 ++++++++++++- > 3 files changed, 55 insertions(+), 1 deletion(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index ae4fe86..7d36ac8 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -681,6 +681,7 @@ struct huge_bootmem_page { > }; > > int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list); > +int replace_free_hugepage_folios(unsigned long start_pfn, unsigned long end_pfn); > struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, > unsigned long addr, int avoid_reserve); > struct folio *alloc_hugetlb_folio_nodemask(struct hstate *h, int preferred_nid, > @@ -1059,6 +1060,11 @@ static inline int isolate_or_dissolve_huge_page(struct page *page, > return -ENOMEM; > } > > +int replace_free_hugepage_folios(unsigned long start_pfn, unsigned long end_pfn) > +{ > + return 0; > +} > + > static inline struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, > unsigned long addr, > int avoid_reserve) > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 8e1db80..a099c54 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2975,6 +2975,43 @@ int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list) > return ret; > } > > +/* > + * replace_free_hugepage_folios - Replace free hugepage folios in a given pfn > + * range with new folios. > + * @stat_pfn: start pfn of the given pfn range > + * @end_pfn: end pfn of the given pfn range > + * Returns 0 on success, otherwise negated error. > + */ > +int replace_free_hugepage_folios(unsigned long start_pfn, unsigned long end_pfn) > +{ > + struct hstate *h; > + struct folio *folio; > + int ret = 0; > + > + LIST_HEAD(isolate_list); > + > + while (start_pfn < end_pfn) { > + folio = pfn_folio(start_pfn); > + if (folio_test_hugetlb(folio)) { > + h = folio_hstate(folio); > + } else { > + start_pfn++; > + continue; > + } > + > + if (!folio_ref_count(folio)) { > + ret = alloc_and_dissolve_hugetlb_folio(h, folio, &isolate_list); > + if (ret) > + break; > + > + putback_movable_pages(&isolate_list); > + } > + start_pfn++; > + } > + > + return ret; > +} > + > struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, > unsigned long addr, int avoid_reserve) > { > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index dde19db..1dcea28 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6504,7 +6504,18 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end, > ret = __alloc_contig_migrate_range(&cc, start, end, migratetype); > if (ret && ret != -EBUSY) > goto done; > - ret = 0; > + > + /* > + * When in-use hugetlb pages are migrated, they may simply be > + * released back into the free hugepage pool instead of being > + * returned to the buddy system. After the migration of in-use > + * huge pages is completed, we will invoke the > + * replace_free_hugepage_folios() function to ensure that > + * these hugepages are properly released to the buddy system. > + */ > + ret = replace_free_hugepage_folios(start, end); > + if (ret) > + goto done; > > /* > * Pages from [start, end) are within a pageblock_nr_pages -- Cheers, David / dhildenb