From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2B88325B30E for ; Mon, 20 Oct 2025 10:32:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760956326; cv=none; b=OaGlCT4NzWzM6taKHpps453GSpD0AJLeUU9+YyountNpI3gqZhOjisJxts5NwWNAs6zVaiMw6vRW3nIfBr4fxAq7y69GHDtYJ9EnPVyUEfCm9/gV8H6uHvVfD46xnYKUTU5uhnkj2Aftfqh6403NK5aCsPKyMPkk+EUIXK/L6WI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760956326; c=relaxed/simple; bh=1Tm1FKT+wU9gzbCx6LcGr6GchkpoM6QXziJclbBg6DU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=iUc8f1B5/OgnqWisZrbuYT3c5c5FiV/sl9eWlIpVmLfAcJoIqpJZWZjNG+QCgbP2jmfnQ46xv6vupddvF0unfxJQDWwt2jP0Adt2pzhSX4S91ZY2ptBQ1yUwNFFXYMeUBQLitxIbBmqIvO8B3yrWM+5OJvqnl0R+ipyc8lVvbyY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz; spf=pass smtp.mailfrom=suse.cz; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=WaHmBe7Z; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=aarrovnk; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=JYMcYo1p; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=QHzhkXy5; arc=none smtp.client-ip=195.135.223.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.cz Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="WaHmBe7Z"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="aarrovnk"; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="JYMcYo1p"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="QHzhkXy5" Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 0DD582116D; Mon, 20 Oct 2025 10:31:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1760956318; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=OOdR9pfKqPD0a3Q4nBDVe6mStJO4QAAfwM2KqhG51tQ=; b=WaHmBe7ZE1oJC86MBJcU6qbFI1t6s0YSn+Hvy5Dr6UwidJ621G/9W+vP6cfXoy6/iLzVhV fMqWPjZqprU7o5rNuYvYRAn1yjZ4AN9mHKnTQPD3V0q6Z9Nng2Byn+HmmNyJjC/kX6G4Cq PlKuYg38J9Ut4e4M2uJQSZzs65cnVBw= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1760956318; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=OOdR9pfKqPD0a3Q4nBDVe6mStJO4QAAfwM2KqhG51tQ=; b=aarrovnkqkw5FLzzdsHl2oHIZF/qYCrKhaisXTJqGY9bTW72ZRb/7rsQHXKpO4MFfPeaJa by0irXzlOjq3EjBA== Authentication-Results: smtp-out1.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1760956314; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=OOdR9pfKqPD0a3Q4nBDVe6mStJO4QAAfwM2KqhG51tQ=; b=JYMcYo1pjH+WrBomtcKOa/dnrmp3Lum/8QPJVBri8WA6XC1QlQvslYWlIUYqDepToviVk8 paKTyBlTA1JLo44wXV8S7CyDMSj6g8+Fi9dTYsnO7KJbGCIP8yhtln+uvsP5u4MtSkVXbS Xwp8cfV623eV8S8nhUNj+9ZpV9MUxAU= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1760956314; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=OOdR9pfKqPD0a3Q4nBDVe6mStJO4QAAfwM2KqhG51tQ=; b=QHzhkXy5c1nUyHDTNV5oqoiXtTtzQf0C2dGRNcH38mhJjJ8NJedTpE4Zv62kFVJohLM9wU CoHatHszYU4pzpAQ== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id AE8D113A8E; Mon, 20 Oct 2025 10:31:53 +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 Kqu3KJkP9mg1QgAAD6G6ig (envelope-from ); Mon, 20 Oct 2025 10:31:53 +0000 Message-ID: <48a24efa-a326-4cca-ab28-50c6251bf03a@suse.cz> Date: Mon, 20 Oct 2025 12:31:53 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/3] mm: treewide: make get_free_pages() and return void * Content-Language: en-US To: David Hildenbrand , Jiri Slaby , Matthew Wilcox , Mike Rapoport Cc: Andrew Morton , Brendan Jackman , Greg Kroah-Hartman , Johannes Weiner , Julia Lawall , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Suren Baghdasaryan , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20251018093002.3660549-1-rppt@kernel.org> <3e798b9e-4915-404f-9197-ed3c32587141@kernel.org> <85707316-3f2b-4e29-b821-a32f9097244e@kernel.org> <635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com> <3b97b754-890a-46c6-b892-a0324d529a3d@kernel.org> 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+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[16]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo] X-Spam-Flag: NO X-Spam-Score: -4.30 On 10/20/25 11:13, David Hildenbrand wrote: > On 20.10.25 11:08, Jiri Slaby wrote: >> On 20. 10. 25, 11:02, David Hildenbrand wrote: >>> Regarding the metadata overhead, in 2015 Linus wrote in that thread: >>> >>> "Long ago, allocating a page using kmalloc() was a bad idea, because >>> there was overhead for it in the allocation and the code. >>> >>> These days, kmalloc() not only doesn't have the allocation overhead, >>> but may actually scale better too, thanks to percpu caches etc." >>> >>> What's that status of that 10 years later? >> >> AFAI skimmed through the code, for allocations > 2 pages >> (KMALLOC_MAX_CACHE_SIZE) -- if size is a constant -- slub resorts to >> alloc_pages(). >> >> For smaller ones (1 and 2 pages), there is a very little overhead in >> struct slab -- mm people, please correct me if I am wrong. > > If it's really only "struct slab", then there is currently no overhead. > Once it is decoupled from "struct page", there would be some. Yes, but there's potentially better scalability and more debugging possibilities as benefits. > IIUC, I'm surprised that larger allocations wouldn't currently end up in > PageSlab() pages. Can you elaborate why surprised?