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[2003:cb:c739:2400:78ac:64bb:a39e:2578]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3675a0e141esm13345649f8f.58.2024.07.02.07.57.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Jul 2024 07:57:45 -0700 (PDT) Message-ID: Date: Tue, 2 Jul 2024 16:57:44 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] mm: Fix khugepaged activation policy To: Ryan Roberts , Andrew Morton , Jonathan Corbet , Barry Song , Baolin Wang , Lance Yang , Yang Shi Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20240702144617.2291480-1-ryan.roberts@arm.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: <20240702144617.2291480-1-ryan.roberts@arm.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-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 0C39840007 X-Stat-Signature: bdfhtjpzb3t4qu8knzuti3ee83sy6x5p X-Rspam-User: X-HE-Tag: 1719932271-792339 X-HE-Meta: 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 6PvJD/2q t33CNphsyuxgH+pKMAbF7P0odWEy14f/IcvB/hQE0IhhbvhWULhHkPfgBHNduN0NOYrNY5//+DaBuU9b4xhnKfBrETTuLmqSoPHyJtQMhx1mhTAwq2oihAUzS66m8bQPEfgElFzXoBFmqKZHEQqWmKxAeL6H8v6JQPl6++BDsKrO5CJRdSw7JzytogzR1YhPKbBJu+IvbFazo402GccPyGfZJpNiDNUAOAsu8IRjwjHSy/i0adyY2H8SokTXgTqtVXnZYrLFW6Qo+vPWiSi1nCVCgWWgDSceYjYJRlcM86hQqQ1yqt6kYydTCK+ETcCyWm0hSrMm8nNo6pJ6fbaK9C96dqTK47IxLgdYQ9noky/2Ayk9gvLRrO22INJag7JZemve+32EGdsbX8yKCKNoIMZ6ThencIhffuTj+WEw5RDMIAmOP0H+DUBX/CzC3reKuz/TgHTq+MNMEHt2CiaaCmCozFw== 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 02.07.24 16:46, Ryan Roberts wrote: > Since the introduction of mTHP, the docuementation has stated that > khugepaged would be enabled when any mTHP size is enabled, and disabled > when all mTHP sizes are disabled. There are 2 problems with this; 1. > this is not what was implemented by the code and 2. this is not the > desirable behavior. > > Desirable behavior is for khugepaged to be enabled when any PMD-sized > THP is enabled, anon or file. (Note that file THP is still controlled by > the top-level control so we must always consider that, as well as the > PMD-size mTHP control for anon). khugepaged only supports collapsing to > PMD-sized THP so there is no value in enabling it when PMD-sized THP is > disabled. So let's change the code and documentation to reflect this > policy. > > Further, per-size enabled control modification events were not > previously forwarded to khugepaged to give it an opportunity to start or > stop. Consequently the following was resulting in khugepaged eroneously > not being activated: > > echo never > /sys/kernel/mm/transparent_hugepage/enabled > echo always > /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled > > Signed-off-by: Ryan Roberts > Fixes: 3485b88390b0 ("mm: thp: introduce multi-size THP sysfs interface") > Closes: https://lore.kernel.org/linux-mm/7a0bbe69-1e3d-4263-b206-da007791a5c4@redhat.com/ > Cc: stable@vger.kernel.org > --- > > Hi All, > > Applies on top of today's mm-unstable (9bb8753acdd8). No regressions observed in > mm selftests. > > When fixing this I also noticed that khugepaged doesn't get (and never has been) > activated/deactivated by `shmem_enabled=`. I'm not sure if khugepaged knows how > to collapse shmem - perhaps it should be activated in this case? > Call me confused. khugepaged_scan_mm_slot() and madvise_collapse() only all hpage_collapse_scan_file() with ... IS_ENABLED(CONFIG_SHMEM) ? collapse_file() is only called by hpage_collapse_scan_file() ... and there we check "shmem_file(file)". So why is the IS_ENABLED(CONFIG_SHMEM) check in there if collapse_file() seems to "collapse filemap/tmpfs/shmem pages into huge one". Anyhow, we certainly can collapse shmem (that's how it all started IIUC). Besides that, khugepaged only seems to collapse !shmem with VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); The thp_vma_allowable_order() check tests if we are allowed to collapse a PMD_ORDER in that VMA. -- Cheers, David / dhildenb