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Fri, 8 Nov 2024 10:08:40 +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 aKsZMyjjLWeNLwAAD6G6ig (envelope-from ); Fri, 08 Nov 2024 10:08:40 +0000 Message-ID: Date: Fri, 8 Nov 2024 11:08:40 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: slab warning: kmem_cache of name 'dm_bufio_buffer' already exists Content-Language: en-US To: Mikulas Patocka , Dave Chinner , "Darrick J. Wong" , linux-xfs@vger.kernel.org, Christoph Hellwig Cc: Pedro Falcato , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , zkabelac@redhat.com, Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org References: <9c3fecc3-19dc-42d4-6c89-4a48e9ad19cc@redhat.com> <5a1e67c3-481e-4c6e-8507-5a8ea0bd9f28@suse.cz> <27ba7473-9255-2407-8e4e-e5c3cafc25c4@redhat.com> <58fce0d4-9074-3d98-5a1b-970371f0c23c@redhat.com> 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: <58fce0d4-9074-3d98-5a1b-970371f0c23c@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 2AAAB18000A X-Rspamd-Server: rspam11 X-Stat-Signature: q1aojkb79m5uexkzdmnqcupg879dxao6 X-HE-Tag: 1731060485-887995 X-HE-Meta: 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 lJ5H2LFZ kYO+vexVZhGys53BUD54jnCay+66Ks1VfyknRE3lby1R79eC0TRijlVAvSU3X6YrDLYkYmdIVbytjUxzxt6YhFq30y3aDTtVTdOhFxl6re2fMqE8WczatAvdYG186sEFRheH5h+XPt743LkXxWWvnQyk3HEtAM2hZR9KQraMRsj/5pnNC8s7OKYuvKCjfsPx+rN6OKmH0aMGf1x4mx/NDVeTK4t8uepyMEx1IykQ4JycujCZEWHbtPv5+iTZHrPJ3gikZC/pHZKE1hM7CloUIfUfjyN37rEGSTHm4Qhrg5XGshZt9MfVjJ7yQoRyNhId77iJw5RbdYB/UrdZ7TUtwNl4HpdvHwUh+KXnqT++vYlmT7hjq9HlYTvcBW2vFBvqDjz6bQIVNgENNiWixrNF8vap4bg== 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 11/6/24 22:22, Mikulas Patocka wrote: > >> BTW, what benefits do you get from creating own kmem caches instead of using >> kmalloc()? If it's just alignment, if you round up the intended size to >> power of two, there's implicit kmalloc alignment guarantee. > > See the function xfs_buf_alloc_kmem - it allocates a buffer using kmalloc, > tests if the buffer crosses a page boundary, and if it does, the code > falls back to xfs_buf_alloc_pages. > > Do you think that it can be simplified to just allocate a buffer and NOT > check for page crossing? Right, IIRC xfs was one of the usecases that prompted us towards defining the kmalloc alignment guarantees, which was around 2019. So today, kmalloc() allocations will not cross a page boundary if the requested size is lower than page size, and it's a power-of-two value. Even if SLUB debugging is enabled (before the alignment became guaranteed, it would happen naturally, and only be violated by either using SLOB, or enabling SLUB debugging). xfs_buf_alloc_kmem() could be thus simplified. >> AFAICS there's some alignment for c->slab_cache in >> dm_bufio_client_create() > > There are two slab caches - one for the dm_buffer structure and one for > the buffer data (if the buffer size is less than a page). > >> In case the allocations have odd sizes without any such alignment >> (the case of c->slab_buffer?) separate size-specific caches can result in >> better packing, but that should only matter if you expect many/long-lived >> objects to be allocated. > > The cache for the dm_buffer structure is there so that it utilizes memory > better. Yes - there may be a lot of long-lived dm_buffers in memory. OK. > Mikulas >