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[2003:d8:2f2c:1e00:1e1e:7a32:e798:6457]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a561a3c763sm1530124f8f.62.2025.06.12.03.08.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Jun 2025 03:08:58 -0700 (PDT) Message-ID: Date: Thu, 12 Jun 2025 12:08:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] selftests: khugepaged: fix the shmem collapse failure To: Baolin Wang , akpm@linux-foundation.org Cc: lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, shuah@kernel.org, ziy@nvidia.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: 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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ZIdfwUeuJA_NCSnCtr4j3qmJa3P4AXMDwEmVEwX4d84_1749722940 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 8027320008 X-Stat-Signature: fzs43p97c16ahxkgozpsu73kkinfhbzh X-HE-Tag: 1749722942-877456 X-HE-Meta: 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 RROtN+Ym SroPEm3uBgjSHZjMohJVPdQITus2Dgo1azJSrwuFaHr39P5SjRol9+tVoEnxhPDi+nDPsy8QhxAeX8Ew= 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 12.06.25 05:54, Baolin Wang wrote: > When running the khugepaged selftest for shmem (./khugepaged all:shmem), Hmm, this combination is not run automatically through run_tests.sh, right? IIUC, it only runs "./khugepaged" which tests anon only ... Should we add it there? Then I would probably have noticed that myself earlier :) > I encountered the following test failures: > " > Run test: collapse_full (khugepaged:shmem) > Collapse multiple fully populated PTE table.... Fail > ... > Run test: collapse_single_pte_entry (khugepaged:shmem) > Collapse PTE table with single PTE entry present.... Fail > ... > Run test: collapse_full_of_compound (khugepaged:shmem) > Allocate huge page... OK > Split huge page leaving single PTE page table full of compound pages... OK > Collapse PTE table full of compound pages.... Fail > " > > The reason for the failure is that, it will set MADV_NOHUGEPAGE to prevent > khugepaged from continuing to scan shmem VMA after khugepaged finishes > scanning in the wait_for_scan() function. Moreover, shmem requires a refault > to establish PMD mappings. > > However, after commit 2b0f922323cc, PMD mappings are prevented if the VMA is > set with MADV_NOHUGEPAGE flag, so shmem cannot establish PMD mappings during > refault. Right. It's always problematic when we have some contradicting information in the VMA vs. pagecache. > > To fix this issue, we can set the MADV_NOHUGEPAGE flag after the shmem refault. > With this fix, the shmem test case passes. > > Fixes: 2b0f922323cc ("mm: don't install PMD mappings when THPs are disabled by the hw/process/vma") > Signed-off-by: Baolin Wang > --- > tools/testing/selftests/mm/khugepaged.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c > index 8a4d34cce36b..d462f62d8116 100644 > --- a/tools/testing/selftests/mm/khugepaged.c > +++ b/tools/testing/selftests/mm/khugepaged.c > @@ -561,8 +561,6 @@ static bool wait_for_scan(const char *msg, char *p, int nr_hpages, > usleep(TICK); > } > > - madvise(p, nr_hpages * hpage_pmd_size, MADV_NOHUGEPAGE); > - > return timeout == -1; > } > > @@ -585,6 +583,7 @@ static void khugepaged_collapse(const char *msg, char *p, int nr_hpages, > if (ops != &__anon_ops) > ops->fault(p, 0, nr_hpages * hpage_pmd_size); > > + madvise(p, nr_hpages * hpage_pmd_size, MADV_NOHUGEPAGE); > if (ops->check_huge(p, expect ? nr_hpages : 0)) > success("OK"); > else It's a shame we have this weird interface: there is no way we can clear VM_HUGEPAGE without setting VM_NOHUGEPAGE :( But, do we even care about setting MADV_NOHUGEPAGE at all? IIUC, we'll almost immediately later call cleanup_area() where we munmap(), right? -- Cheers, David / dhildenb