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[2003:cb:c713:2a00:f151:50f1:7164:32e6]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42905971993sm78289725e9.16.2024.08.08.07.14.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 Aug 2024 07:14:52 -0700 (PDT) Message-ID: <052552f4-5a8d-4799-8f02-177585a1c8dd@redhat.com> Date: Thu, 8 Aug 2024 16:14:51 +0200 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 1/2] mm/numa: no task_numa_fault() call if page table is changed To: Zi Yan , Andrew Morton Cc: Baolin Wang , linux-mm@kvack.org, "Huang, Ying" , Kefeng Wang , linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20240807184730.1266736-1-ziy@nvidia.com> <956553dc-587c-4a43-9877-7e8844f27f95@linux.alibaba.com> <1881267a-723d-4ba0-96d0-d863ae9345a4@redhat.com> <09AC6DFA-E50A-478D-A608-6EF08D8137E9@nvidia.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: <09AC6DFA-E50A-478D-A608-6EF08D8137E9@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 08.08.24 16:13, Zi Yan wrote: > On 8 Aug 2024, at 4:22, David Hildenbrand wrote: > >> On 08.08.24 05:19, Baolin Wang wrote: >>> >>> >>> On 2024/8/8 02:47, Zi Yan wrote: >>>> When handling a numa page fault, task_numa_fault() should be called by a >>>> process that restores the page table of the faulted folio to avoid >>>> duplicated stats counting. Commit b99a342d4f11 ("NUMA balancing: reduce >>>> TLB flush via delaying mapping on hint page fault") restructured >>>> do_numa_page() and do_huge_pmd_numa_page() and did not avoid >>>> task_numa_fault() call in the second page table check after a numa >>>> migration failure. Fix it by making all !pte_same()/!pmd_same() return >>>> immediately. >>>> >>>> This issue can cause task_numa_fault() being called more than necessary >>>> and lead to unexpected numa balancing results (It is hard to tell whether >>>> the issue will cause positive or negative performance impact due to >>>> duplicated numa fault counting). >>>> >>>> Reported-by: "Huang, Ying" >>>> Closes: https://lore.kernel.org/linux-mm/87zfqfw0yw.fsf@yhuang6-desk2.ccr.corp.intel.com/ >>>> Fixes: b99a342d4f11 ("NUMA balancing: reduce TLB flush via delaying mapping on hint page fault") >>>> Cc: >>>> Signed-off-by: Zi Yan >>> >>> The fix looks reasonable to me. Feel free to add: >>> Reviewed-by: Baolin Wang >>> >>> (Nit: These goto labels are a bit confusing and might need some cleanup >>> in the future.) >> >> Agreed, maybe we should simply handle that right away and replace the "goto out;" users by "return 0;". >> >> Then, just copy the 3 LOC. >> >> For mm/memory.c that would be: >> >> diff --git a/mm/memory.c b/mm/memory.c >> index 67496dc5064f..410ba50ca746 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -5461,7 +5461,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) >> if (unlikely(!pte_same(old_pte, vmf->orig_pte))) { >> pte_unmap_unlock(vmf->pte, vmf->ptl); >> - goto out; >> + return 0; >> } >> pte = pte_modify(old_pte, vma->vm_page_prot); >> @@ -5528,15 +5528,14 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) >> vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, >> vmf->address, &vmf->ptl); >> if (unlikely(!vmf->pte)) >> - goto out; >> + return 0; >> if (unlikely(!pte_same(ptep_get(vmf->pte), vmf->orig_pte))) { >> pte_unmap_unlock(vmf->pte, vmf->ptl); >> - goto out; >> + return 0; >> } >> goto out_map; >> } >> -out: >> if (nid != NUMA_NO_NODE) >> task_numa_fault(last_cpupid, nid, nr_pages, flags); >> return 0; >> @@ -5552,7 +5551,9 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) >> numa_rebuild_single_mapping(vmf, vma, vmf->address, vmf->pte, >> writable); >> pte_unmap_unlock(vmf->pte, vmf->ptl); >> - goto out; >> + if (nid != NUMA_NO_NODE) >> + task_numa_fault(last_cpupid, nid, nr_pages, flags); >> + return 0; >> } > > Looks good to me. Thanks. > > Hi Andrew, > > Should I resend this for an easy back porting? Or you want to fold David’s > changes in directly? Note that I didn't touch huge_memory.c. So maybe just send a fixup on top? -- Cheers, David / dhildenb