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[2003:cb:c70e:d000:4622:73e7:6184:8f0d]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43656b3b207sm110304915e9.32.2024.12.21.06.35.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 21 Dec 2024 06:35:12 -0800 (PST) Message-ID: <0ca35fe5-9799-4518-9fb1-701c88501a8d@redhat.com> Date: Sat, 21 Dec 2024 15:35:10 +0100 Precedence: bulk X-Mailing-List: linux-kernel@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 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 > > 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 > > 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. > + */ As mentioned in my other mail, what I don't like about this is, IIUC, the pages can get reallocated anytime after we successfully migrated them, or is there anything that prevents that? Did you ever try allocating a larger range with a single alloc_contig_range() call, that possibly has to migrate multiple hugetlb folios in one go (and maybe just allocates one of the just-freed hugetlb folios as migration target)? -- Cheers, David / dhildenb