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[2003:cb:c715:d00:e9a5:ae4b:9bdb:d992]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42bb37f7849sm211160325e9.7.2024.09.04.06.47.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Sep 2024 06:47:31 -0700 (PDT) Message-ID: <273ee480-76b4-4b57-a95b-2849fe394bc0@redhat.com> Date: Wed, 4 Sep 2024 15:47:29 +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-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: AC21414000F X-Stat-Signature: e3ua94xz6dwfu6up4779qb9izmuuinud X-Rspam-User: X-HE-Tag: 1725457655-309201 X-HE-Meta: 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 Q5JOp8tS 5Qwi6JEZ8XAIxVz2DArE6Pjgeh4pNpl719Eo4H2qklBuXWzp3AiM3cz6Jj2cy1XCyP/2GlbznV7Yo4tp+uwrh1EIoIbWjXebICUrzJh4yGLL8j0rDhOsskBpXZou7Yoay8tMVOeqvMXzPJrXWJi0pVN9aT69s69W2GdLj9ZxYHu51zJRrRO/DboOXgIsZ51hXtwmc6yLPD+sfJskww36GIcCpzquAMV53MWiLRo7Wlql4c0ZNKDen6QbGLNziKQyorw8NHiiUpkWL7JE4G84yf2mU+1eb3KbrgjkhmV64rYdjMxn5reLU5DqC8EEpJqqQBvz6oP/N4Gnz3w5eIi1NZfFvraF6JyUyzCm5+qD4fqnDPOIGFPH4dZuyD3cILFiLV2hxnJWRTDBBpXQpUCWZDMGpcCAZpuaw2Dl/nDpTxtad59FXevJCHzzOQy4Biqnsxk4t 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 04.09.24 12:05, Anders Roxell wrote: > On Tue, 3 Sept 2024 at 14:37, David Hildenbrand wrote: >> >> 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? > > David thank you for quick patch for me to try. > > This patch helped the original regression on v6.10-rc1, but on current mainline > v6.11-rc6 the patch does nothing and the performance is as expeced. Just so I understand this correctly: It fixed itself after v6.11-rc4, but v6.11-rc4 was fixed with my patch? If that's the case, then it's really the compiler deciding whether to inline or not, and on v6.11-rc6 it decides to inline again. -- Cheers, David / dhildenb