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(p200300cbc744b5003f9d130dea00afc7.dip0.t-ipconnect.de. [2003:cb:c744:b500:3f9d:130d:ea00:afc7]) by smtp.gmail.com with ESMTPSA id p9-20020a05600c1d8900b0041563096e15sm24206317wms.5.2024.05.07.09.43.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 May 2024 09:43:06 -0700 (PDT) Message-ID: <21d88422-7378-4a63-8fbf-f70889f309c1@redhat.com> Date: Tue, 7 May 2024 18:43:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/fault: speed up uffd-unit-test by 10x: rate-limit "MCE: Killing" logs To: John Hubbard , Andy Lutomirski Cc: Dave Hansen , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , LKML , linux-mm@kvack.org, Peter Xu , Axel Rasmussen References: <20240507022939.236896-1-jhubbard@nvidia.com> <016d8cff-efc3-4ef1-9aff-7c21c48f2d69@redhat.com> <302d50ac-45ff-470e-90a0-b349821706a6@nvidia.com> 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: <302d50ac-45ff-470e-90a0-b349821706a6@nvidia.com> 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: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 3C1AE180014 X-Stat-Signature: 8bjfzs74eow644x83gnd5wpcdigfxmfy X-HE-Tag: 1715100191-110405 X-HE-Meta: U2FsdGVkX1/m6+sb68kufHWsFDcvktPFq5uBAjdo2mQf6R0dhCRqRE3VjhnGtw0ztHAdSQh20CDz5/KJGWZPdD5SYNxgAlowL8jTOl9rRiBbI3COaK95qBj1MyubykGh5Z8BemVB4rTYD2omYmyqJXkEpqnx+4IJNWnk8iJjSzPntXprDhhIWonDMDTiVZqwTX+T65UUmkD3srY2dFlGRQXey3q+rVNg4kRjrRoolQzR5kFV5tbuYZUbfTXabfCRDKoU+4OtTwYfoeI4DdUij/+43J2McjUkTzp5HVW3op0jAgTkszomWMoO5S/31ZtXJvM36gAzZVRGoyBtaNiIWlSjCFm+1rTgVH+G+6tT7dkQFjJy05Ru5xn088Bi92rnwuYfZnIVXN2oG1h2BcthFPYojZG6uqv8QopViAuVE0ik56YryLKKpzomak8NrthhYqnJURakhWUK2+7QXs1D6GoLqqMrz7DHWG7nzgtc+swTtjtcmeQU1Y/MdnMBGLEwJ9wJVHVHU+Ckj6k+aGqhh1jZmiaQiVAmKMC+19tv1+Lzn6uZTrubjqlsYwDpMXJehrRXVGfpBeVIFsh9dAIgoScjz27kILky3TmGYv1iARGAn9KDPfuXLo9nJFLMJOsPvypL/lCzo5vCHoHWSlvhp291SQBIsvMfhk4lKFU6pdbg2k1wxafyABJI7firlUT33Z6TTw4atq71Uire9ktaNh9lwg195qs1k2YMvc3jUqOGYnkeRI5vcAk9DSS6F04CBFI9wIUL6LgeyMYk0Kl7tM1tXPsNPIX5srJm8xSbqENQ6kdw3d2AxWwyMafgebs89UY/egqRBkCDf8ncfTlJJ/Y/Y3KvXNUvhfB5tkZuxZJU0jVnVo880tdoZXDJFM9UPlzRlG/8Rh25W9tfrJWsFmfFoBxwIwHFj76KiesVX+Oz7NQu0u2Vj5Sk6c1QRG0xS4gFA6fdetOo9AV3WWB BjAI1Asa 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 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 07.05.24 18:28, John Hubbard wrote: > On 5/7/24 1:13 AM, David Hildenbrand wrote: >> The patch subject is misleading. This should be "don't flood the system > > I went back and forth on that subject line. :) > >> log". Nobody cares about the speed of a unittest ;) > > Yes they do. People should actually run the selftests, which in turn have > enshrined their guidelines in kernel doc. See dev-tools/kselftest.rst, > "Contributing new tests", which says, as you would hope, "Don't take > too long". > > It's important. Tests need to be quick, and having one out of 50 that > blows it up is worth fixing. I'm pretty sure you got my point: it's much more important to not let unprivileged users flood the log (possibly harming the system?) than making a test run faster :) > >> >> On 07.05.24 04:29, John Hubbard wrote: >>> If a system experiences a lot of memory failures, then any associated >>> printk() output really needs to be rate-limited. I noticed this while >>> running selftests/mm/uffd-unit-tests, which logs 12,305 lines of output, >>> adding (on my system) an extra 97 seconds of runtime due to printk time. >> >> Recently discussed: >> >> https://lkml.kernel.org/r/a9e3120d-8b79-4435-b113-ceb20aa45ee2@alu.unizg.hr >> >> See the pros/cons of using ratelimiting, and what an alternative for >> uffd is that Axel is working on. >> >> (CCing Peter and Axel) >> > > That thread seems to have stalled. Yes, there was no follow-up. > I *do* have MCE experience (writing a > handler, > dealing with MCEs and related bugs), and what they wrote so far is exactly > correct: if you were going to flood the log, then no, we don't need to see > every single line printed. The first 10 or so, plus the fact that rate > limiting > kicked in, is sufficient to proceed with debugging and/or hardware > replacement. > > I'd like to just do this patch almost as-is, just with a fixed up subject, > perhaps: > > x86/fault: rate-limit to avoid flooding dmesg with "MCE: Killing" > reports > > Yes? Makes sense to me (and thanks for confirming that we don't need complexity elsewhere). I think we at least need "Fixes:" (not sure if stable is warranted as well, 1b0a151c10a6d823f033023b9fdd9af72a89591b didn't CC stable). Consider adding a link to the report in that thread. Acked-by: David Hildenbrand -- Cheers, David / dhildenb