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Tue, 2 Jul 2024 21:20:13 +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 ATBDAg1vhGYbCwAAD6G6ig (envelope-from ); Tue, 02 Jul 2024 21:20:13 +0000 Message-ID: <627741f3-dd28-45b3-ada9-1efeac66351e@suse.cz> Date: Tue, 2 Jul 2024 23:20:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm, slab: extend kmalloc() alignment for non power-of-two sizes Content-Language: en-US To: Roman Gushchin Cc: linux-mm@kvack.org, David Rientjes , Christoph Lameter , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Kees Cook , Alice Ryhl , Boqun Feng , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, patches@lists.linux.dev References: <20240702155800.166503-2-vbabka@suse.cz> <1ca7b081-c1f0-45a3-b901-39c503368f43@suse.cz> 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: 7bit X-Stat-Signature: 36gwrghfwxie8abx6pw9h1m5yougncti X-Rspam-User: X-Rspamd-Queue-Id: 01FD040008 X-Rspamd-Server: rspam02 X-HE-Tag: 1719955214-158699 X-HE-Meta: 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 IiK3eUYj WotItXTaHk0jAS7omsEVHpKmG6cOQxfHleZtO6VlSHE+xvGrmialjNioHrfN74PPzgM9nSi+/fbMGOVfnr8GGP7zmib8yuRCgLJw8pnpUTPox/fCseXQ4t2dNXTKNZR3PI/axF1EzqB/+OLv8Q8gIfjlASXH3KozYqztHApi3VLXfrd0JovVXtmXopXMDXX5i92LsjWFuU2IZNshswMDZezPrU7nqGKlnXRlPJ2ETCj3J93Em1RwMR3G0WMuM0ZQ3MQvIm9gMgfpVS5oH7As4myXtUCkJpaNOK+vagl56+7Na3XaChA5niLBgQ9CzOKtm8nuIyQ+scYMCPNViTkc5FTIsGg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000005, 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 7/2/24 11:13 PM, Roman Gushchin wrote: > On Tue, Jul 02, 2024 at 10:25:44PM +0200, Vlastimil Babka wrote: >> On 7/2/24 9:30 PM, Roman Gushchin wrote: >> > On Tue, Jul 02, 2024 at 05:58:01PM +0200, Vlastimil Babka wrote: >> > Hello Vlastimil, >> > >> > the idea and the implementation makes total sense to me. >> > >> > Do you have an estimate for the memory overhead it will typically introduce? >> >> There's no new overhead for the non-debug case as the layout already >> naturally has the same alignment as is now guaranteed. Debug has its own >> overhead so it's enabled only when needed, and this will not add much more. > > Got it, but can you, please, add this note with some explanation why it's true > to the commit message? Because it's not obvious and the commit message makes It's there but later: 1) doesn't change the current slab layout (and thus does not increase internal fragmentation) when slab debugging is not active > almost the opposite impression: > Slab allocators have been guaranteeing natural alignment for > power-of-two sizes <...>, while any other sizes are > aligned only to ARCH_KMALLOC_MINALIGN bytes. > > Should it be "guaranteed to be aligned" vs are actually aligned? Yes that's the case. Will update. >> >> > I don't think it will be too large though and actually can be compensated >> > by potential performance gains due to a better memory alignment. What do you >> > think? >> >> Yeah but again, the difference would be only in the debug case and >> performance gains there are not so interesting :) > > Acked-by: Roman Gushchin Thanks! > Thanks!