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[2003:cb:c709:7f00:8a04:4c6f:a761:af60]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-374c07eed5dsm8960138f8f.116.2024.09.03.05.37.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Sep 2024 05:37:31 -0700 (PDT) Message-ID: Date: Tue, 3 Sep 2024 14:37:30 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Potential Regression in futex Performance from v6.9 to v6.10-rc1 and v6.11-rc4 To: Anders Roxell Cc: Arnd Bergmann , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , dvhart@infradead.org, dave@stgolabs.net, andrealmeid@igalia.com, Linux Kernel Mailing List , Linux-MM 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-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: i7399kof5ekz6q49n6ckdr94bu54m9d4 X-Rspam-User: X-Rspamd-Queue-Id: 0653720014 X-Rspamd-Server: rspam02 X-HE-Tag: 1725367056-900525 X-HE-Meta: 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 IK9MomqE a+5hZKFUvNm0S4WMnLVjRdQ9stsmqT5aCKnqPOrWp2PLtZHHHTP0gtVeGkHtNAi86AMxM9bXHp7PSgjBRvs/trEN4cUkKmiFeU31TXyHtmUnYJWwYlhBJYn+7qeXNUr1CSjTVuErjWYUgWirTK8ddLH2DyBRV/2+q9nJy1+daB+DgXN5W6ZGtWkzk0UM0gp7nRrTbUn4J4sYZD23Tgeiixz/Ri2tn/NpD3zuVRiimsQi/i4sN08W0EMd++BSlqsPDorrmO4Gg7ttVJt2qgpA2NocK/tGoLVhRoxB/nsC0/MVqges0hw8PzB4K4I1HDAcQP8/7X8Z3yK/IA6UN3+S+D7oMzqny+lRKSTJN8EdBxHZIxx+h8Zx2znUBiVw5cOvXZS2banKPLHGKPkb0MajRX3tlYUNZSgJyd6whNENI1WoB2sc= 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 03.09.24 14:21, Anders Roxell wrote: > Hi, > > I've noticed that the futex01-thread-* tests in will-it-scale-sys-threads > are running about 2% slower on v6.10-rc1 compared to v6.9, and this > slowdown continues with v6.11-rc4. I am focused on identifying any > performance regressions greater than 2% that occur in automated > testing on arm64 HW. > > Using git bisect, I traced the issue to commit > f002882ca369 ("mm: merge folio_is_secretmem() and > folio_fast_pin_allowed() into gup_fast_folio_allowed()"). Thanks for analyzing the (slight) regression! > > My tests were performed on m7g.large and m7g.metal instances: > > * The slowdown is consistent regardless of the number of threads; > futex1-threads-128 performs similarly to futex1-threads-2, indicating > there is no scalability issue, just a minor performance overhead. > * The test doesn’t involve actual futex operations, just dummy wake/wait > on a variable that isn’t accessed by other threads, so the results might > not be very significant. > > Given that this seems to be a minor increase in code path length rather > than a scalability issue, would this be considered a genuine regression? Likely not, I've seen these kinds of regressions (for example in my fork micro-benchmarks) simply because the compiler slightly changes the code layout, or suddenly decides to not inline a functions. Still it is rather unexpected, so let's find out what's happening. My first intuition would have been that the compiler now decides to not inline gup_fast_folio_allowed() anymore, adding a function call. LLVM seems to inline it for me. GCC not. Would this return the original behavior for you? diff --git a/mm/gup.c b/mm/gup.c index 69c483e2cc32d..6642f09c95881 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2726,7 +2726,8 @@ EXPORT_SYMBOL(get_user_pages_unlocked); * in the fast path, so instead we whitelist known good cases and if in doubt, * fall back to the slow path. */ -static bool gup_fast_folio_allowed(struct folio *folio, unsigned int flags) +static __always_inline bool gup_fast_folio_allowed(struct folio *folio, + unsigned int flags) { bool reject_file_backed = false; struct address_space *mapping; -- Cheers, David / dhildenb