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(p200300cbc72ee400431d9c085611693c.dip0.t-ipconnect.de. [2003:cb:c72e:e400:431d:9c08:5611:693c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38bf32221e2sm11359993f8f.36.2025.01.20.09.59.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Jan 2025 09:59:40 -0800 (PST) Message-ID: <8f36d3ca-3a31-4fc4-9eaa-c53ee84bf6e7@redhat.com> Date: Mon, 20 Jan 2025 18:59:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: mm: CMA reservations require 32MiB alignment in 16KiB page size kernels instead of 8MiB in 4KiB page size kernel. To: Zi Yan , Barry Song <21cnbao@gmail.com>, Juan Yescas Cc: linux-mm@kvack.org, muchun.song@linux.dev, rppt@kernel.org, osalvador@suse.de, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Jann Horn , Liam.Howlett@oracle.com, minchan@kernel.org, jaewon31.kim@samsung.com, charante@codeaurora.org, Suren Baghdasaryan , Kalesh Singh , "T.J. Mercier" , Isaac Manjarres , iamjoonsoo.kim@lge.com, quic_charante@quicinc.com References: <463eb421-ac16-435c-b0a0-51a6a92168f6@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-MFC-PROC-ID: jg5-vXMXDe9jg5pGyE9bgFkgQiOwkgJRm34Q_b1F7fg_1737395982 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: 42DE2A0003 X-Stat-Signature: rweyt17aaxyaixmsex869xhdn7r1iate X-HE-Tag: 1737395985-320982 X-HE-Meta: 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 H9U2+Pao yq/dkyZAdqe+/xez+WKGTWWuijIJBIJ4ftMmWFLMbl26nNY407uYzu6JjEyPjzg9+hvDtfml6x20ExcTwAp/F/9LPTRKxWGzsKdCocEYLn+zsIgmdoJrmkuQ9mnq9ZuPuJeruIybZZndjbmHyw+iy+/AplrgrG7akYiV7qKJE4nQOFMoDhJxqFhJYAVL4ki5dnp1pUzf1UVo/mn1u8NixqEoNACY0VDhBK+//FRbieLe1QWC2J4zbudxKQ3WWy5vYa88PdXT5YZ7kmiILrfufM88NUKOLAeO2oMYW6TUG5JQB1gYNWkS/e1IAODYCCS1rkq3ckxFilmhye3iM5kx1Kyr42JBwZQ3wbGDBSUiqa7ZVGGVL39pkvdkA/tm00A549TPebgt6p4HU33c= 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 20.01.25 16:29, Zi Yan wrote: > On Mon Jan 20, 2025 at 3:14 AM EST, David Hildenbrand wrote: >> On 20.01.25 01:39, Zi Yan wrote: >>> On Sun Jan 19, 2025 at 6:55 PM EST, Barry Song wrote: >>> >>>>>>>> >>>>>>>> >>>>>>>> However, with this workaround, we can't use transparent huge pages. >>>>>>>> >>>>>>>> Is the CMA_MIN_ALIGNMENT_BYTES requirement alignment only to support huge pages? >>>>> No. CMA_MIN_ALIGNMENT_BYTES is limited by CMA_MIN_ALIGNMENT_PAGES, which >>>>> is equal to pageblock size. Enabling THP just bumps the pageblock size. >>>> >>>> Currently, THP might be mTHP, which can have a significantly smaller >>>> size than 32MB. For >>>> example, on arm64 systems with a 16KiB page size, a 2MB CONT-PTE mTHP >>>> is possible. >>>> Additionally, mTHP relies on the CONFIG_TRANSPARENT_HUGEPAGE configuration. >>>> >>>> I wonder if it's possible to enable CONFIG_TRANSPARENT_HUGEPAGE >>>> without necessarily >>>> using 32MiB THP. If we use other sizes, such as 64KiB, perhaps a large >>>> pageblock size wouldn't >>>> be necessary? >>> >>> I think this should work by reducing MAX_PAGE_ORDER like Juan did for >>> the experiment. But MAX_PAGE_ORDER is a macro right now, Kconfig needs >>> to be changed and kernel needs to be recompiled. Not sure if it is OK >>> for Juan's use case. >> >> >> IIRC, we set pageblock size == THP size because this is the granularity >> we want to optimize defragmentation for. ("try keep pageblock >> granularity of the same memory type: movable vs. unmovable") > > Right. In past, it is optimized for PMD THP. Now we have mTHP. If user > does not care about PMD THP (32MB in ARM64 16KB base page case) and mTHP > (2MB mTHP here) is good enough, reducing pageblock size works. > >> >> However, the buddy already supports having different pagetypes for large >> allocations. > > Right. To be clear, only MIGRATE_UNMOVABLE, MIGRATE_RECLAIMABLE, and > MIGRATE_MOVABLE can be merged. Yes! An a THP cannot span partial MIGRATE_CMA, which would be fine. > >> >> So we could leave MAX_ORDER alone and try adjusting the pageblock size >> in these setups. pageblock size is already variable on some >> architectures IIRC. > > Making pageblock size a boot time variable? We might want to warn > sysadmin/user that >pageblock_order THP/mTHP creation will suffer. Yes, some way to configure it. > >> >> We'd only have to check if all of the THP logic can deal with pageblock >> size < THP size. > > Probably yes, pageblock should be independent of THP logic, although > compaction (used to create THPs) logic is based on pageblock. Right. As raised in the past, we need a higher level mechanism that tries to group pageblocks together during comapction/conversion to limit fragmentation on a higher level. I assume that many use cases would be fine with not using 32MB/512MB THPs at all for now -- and instead using 2 MB ones. Of course, for very large installations it might be different. >> >> This issue is even more severe on arm64 with 64k (pageblock = 512MiB). > > This is also good for virtio-mem, since the offline memory block size > can also be reduced. I remember you complained about it before. Yes, yes, yes! :) -- Cheers, David / dhildenb