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Tue, 4 Feb 2025 09:07:31 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id etSdFdPYoWfJeAAAD6G6ig (envelope-from ); Tue, 04 Feb 2025 09:07:31 +0000 Message-ID: Date: Tue, 4 Feb 2025 10:07:31 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [LSF/MM/BPF TOPIC] Guaranteed CMA Content-Language: en-US To: Suren Baghdasaryan , lsf-pc@lists.linux-foundation.org Cc: SeongJae Park , Minchan Kim , m.szyprowski@samsung.com, aneesh.kumar@kernel.org, Joonsoo Kim , mina86@mina86.com, Matthew Wilcox , Lorenzo Stoakes , "Liam R. Howlett" , David Hildenbrand , Michal Hocko , linux-mm , android-kernel-team , David Hildenbrand References: From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspam-User: X-Rspamd-Queue-Id: 0F9674000F X-Rspamd-Server: rspam10 X-Stat-Signature: d3od9isdgr5oforwah9ysmy64yugjjdq X-HE-Tag: 1738660053-16961 X-HE-Meta: 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 5gTxwFsk BS1JGw539MM7fInfb+m4Z7Ic+J7MOu0xYnbkpST3DXddeGIab56y7ioRaK6IUGSbu0AdASdJaeekSe+LsO8e04pDZkxJSrXh30AHFdNnmXKniODGo7TYot/A+X8ZjZw8yoM/JSMUuGxM0hpdsAv7lYzOWkUHm0C4O9DGueArR3rMfkGxZS92m0dOPv0sMkPFzqA5qtL73zStoOuZOpPnESsb5PA6iJZZ+afB0yyeccT8aie/lYWv5fxsFN1HZidzgyvTNG5GVbPmXKc1oPenclfqE60PzXoATXfFQ6Q3C8M66IiLzf+QTfH+bvTF7hXa7hRGuL8anQ7DUeIcN1FS6ZcpI/AWLpXZlQgZzPVCLkEfm+UsQlISBGvoCIDmIi+3y8+0DnZKYPgh5GxN922IzzwUlQKYpPkofPYVcdrcCLe6iXpKcff2h/lskFzUwcCiNJu4xxHdyv7MfYrHpRN3os/g8aw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.008055, 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 2/2/25 01:19, Suren Baghdasaryan wrote: > Hi, > I would like to discuss the Guaranteed Contiguous Memory Allocator > (GCMA) mechanism that is being used by many Android vendors as an > out-of-tree feature, collect input on its possible usefulness for > others, feasibility to upstream and suggestions for possible better > alternatives. > > Problem statement: Some workloads/hardware require physically > contiguous memory and carving out reserved memory areas for such > allocations often lead to inefficient usage of those carveouts. CMA > was designed to solve this inefficiency by allowing movable memory > allocations to use this reserved memory when it’s otherwise unused. > When a contiguous memory allocation is requested, CMA finds the > requested contiguous area, possibly migrating some of the movable > pages out of that area. > In latency-sensitive use cases, like face unlock on phones, we need to > allocate contiguous memory quickly and page migration in CMA takes > enough time to cause user-perceptible lag. Such allocations can also > fail if page migration is not possible. > > GCMA (Guaranteed CMA) is a mechanism previously proposed in [1] which > was not upstreamed but got adopted later by many Android vendors as an > out-of-tree feature. It is similar to CMA but backing memory is > cleancache backend, containing only clean file-backed pages. Most > importantly, the kernel can’t take a reference to pages from the > cleancache, therefore can’t prevent GCMA from quickly dropping them By reference you men a (long-term) pin? Otherwise "no reference" would mean no way to map the pages or read() from them etc. Also there might be speculative references by physical scanners... > when required. This guarantees GCMA low allocation latency and > improves allocation success rate. > > We would like to standardize GCMA implementation and upstream it since > many Android vendors are asking to include it as a generic feature. > > Note: removal of cleancache in 5.17 kernel due to no users (sorry, we > didn’t know at the time about this use case) might complicate > upstreaming. > > Desired participants: > GCMA authors: SeongJae Park , Minchan Kim > CMA authors: Marek Szyprowski , Aneesh Kumar > K.V , Joonsoo Kim , > Michal Nazarewicz > The usual suspects (Willy, Vlastimil, Lorenzo, Liam, Michal, David H), > other mm folks > > [1] https://lore.kernel.org/lkml/1424721263-25314-2-git-send-email-sj38.park@gmail.com/