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[2003:cb:c72f:f700:104b:9184:1b45:1898]) by smtp.gmail.com with ESMTPSA id jg7-20020a05600ca00700b004129a858a7esm8097986wmb.9.2024.02.26.03.48.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 Feb 2024 03:48:13 -0800 (PST) Message-ID: Date: Mon, 26 Feb 2024 12:48:12 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm, thp: display [never] for defrag when THP is set to never To: Liu Song , Yuanhe Shu , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240222115323.4925-1-xiangzao@linux.alibaba.com> <8a723092-347d-443a-82e1-4093f6a1ba0e@redhat.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: 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: rspam08 X-Rspamd-Queue-Id: 57D7B40017 X-Stat-Signature: rrru3smzowzbsjiauwo3r7zbsccrtjhp X-Rspam-User: X-HE-Tag: 1708948097-887773 X-HE-Meta: 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 2KIL7TJi Uspjld8XWygMZvOrz2TSdtKpbJIyaCGTOqqc//AwWiStwS23xe3P9G6tAnl9kzArHrLhEwLmdxETS/3uC8MWMHLwuVuiPuzJiHkvT0jeMESR2/qK6ytNBfM02O0YbZGkVtCTDc1gcP8X9XQFmu1rKZtX0m0RVvZhy01Cj 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 26.02.24 12:22, Liu Song wrote: > > 在 2024/2/26 16:54, David Hildenbrand 写道: >> On 23.02.24 12:01, Liu Song wrote: >>> >>> 在 2024/2/22 20:14, David Hildenbrand 写道: >>>> On 22.02.24 12:53, Yuanhe Shu wrote: >>>>> When transparent_hugepage is set to never by cmdline or echo, defrag >>>>> still show what it used to be and can be modified which makes user >>>>> confusing whether defrag would take effect. >>>>> >>>>> Actually if transparent_hugepage is set to never, defrag will not take >>>>> effect. Just Display never and remain unchangeable to for defrag when >>>>> transparent_hugepage is set to never. >>>>> >>>>> Suggested-by: Liu Song >>>>> Signed-off-by: Yuanhe Shu >>>>> --- >>>> >>>> No, I don't think we want such a dependency between both options. >>>> >>>> You might just end up breaking existing scripts (enable defrag before >>>> enabling THP) for no good reason. >>>> >>> In certain situations where khugepaged_thread is NULL, it would be more >>> reasonable for the value of >>> /sys/kernel/mm/transparent_hugepage/khugepaged/defrag to be 0. The patch >>> should include a fix for this case. >> >> Why? >> >> We have a bunch of THP toggles. They reside in >> "/sys/kernel/mm/transparent_hugepage/", indicating that they are THP >> specific. >> >> Some of them are only in effect if some other toggles are set. >> >> That is very common practice. >> >> If you think something could be confusing, maybe clarify the doc? I >> don't immediately see why any code changes are required, really. > > We should explain this in the documentation, but to be honest, many > people don't read the documentation, and even after we explicitly > disable THP with transparent_hugepage=never, khugepaged/defrag is still > set to 1, and users come asking why it's still defragging. We can't > expect all users to have technical expertise, or to diligently read > through the documentation; it would obviously be best if we could avoid > user confusion altogether. Then tell your users if a feature is enabled, other toggles that affect that feature are ignored. Basic 1on1. If my care engine is off but it's not in neutral, it's not suddenly driving. And most users understand that reasoning. -- Cheers, David / dhildenb