From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 43AEDC55182 for ; Mon, 3 Aug 2026 12:58:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 260916B00B5; Mon, 3 Aug 2026 08:57:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 210B76B00B6; Mon, 3 Aug 2026 08:57:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0D8846B00B7; Mon, 3 Aug 2026 08:57:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id BD1B86B00B5 for ; Mon, 3 Aug 2026 08:57:58 -0400 (EDT) Received: from smtpin07.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 6D2861A065D for ; Mon, 3 Aug 2026 09:19:08 +0000 (UTC) X-FDA: 85059409176.07.074B38F Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf13.hostedemail.com (Postfix) with ESMTP id 987DF20006 for ; Mon, 3 Aug 2026 09:19:06 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=SoVb+i+B; spf=pass (imf13.hostedemail.com: domain of vbabka@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=vbabka@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1785748746; h=from:from:sender:reply-to:subject:subject: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:dkim-signature; bh=5NLzFDn/DIDYnKuFtRjjdVsbfvke595vqQGCR+hV60w=; b=16vRJL0j6JxmDtJ97DMSRhX2tXh/TmhG8gXzHaZJvtSP2Xp2nzzdcLQ2q9+TJa9jJfSWh9 6vqAAJ+RA3+k8NngAdmUd1rHjZhTDXrPW9hNpv+a0QeNoVMtqvtRFPHOYcAPTbahjY6s8/ i51wBCY01G8yTYA+pjvw7LyyWtm25vk= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1785748746; b=45+xRA/erK704xDNwT7NC/auuWJI6NimOD73MgVCINvw8jilENw8QoAEq0ZXFjHISdO2GD jluw7JmU2Y+uDNbp8eM17cE4WKkk4ELSUdZ8XAmoLmO0OlYbi0F4WigxDSZp5Vy37z92ca T+hOKQPZXCFyoXYiRAJXTwlVD/JzXo0= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=SoVb+i+B; spf=pass (imf13.hostedemail.com: domain of vbabka@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=vbabka@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id D2A8043B27; Mon, 3 Aug 2026 09:19:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB2AE1F000E9; Mon, 3 Aug 2026 09:19:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785748745; bh=5NLzFDn/DIDYnKuFtRjjdVsbfvke595vqQGCR+hV60w=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=SoVb+i+BWfxBsK9hIBTWcdEhCUza72DRdfmxdWPqDZaXCntv5d2pXvlMMihf4dJ8C tVuX/WqtRM/X50+M2IyYy9p3p26rzqBS7Nb2IsI56aoiXDbrJ+9N/kfQokcenLrJDX 0YXrahvVbN34EjchyxMxNyuBtu9Ef0qAtmAU7H5OpEbXkxrAfQ4bZ+a/GqN59ScdqF NIdDtypnnVFWMtzJjEAqmN0/9TpnfDjl4WdpZuJD9tS+/R96bO0MOtqa8BJ4dsCwZ1 7oDtMd3y8erfmlm9Xm3IcbQL0Db3nOuiP51EU7fZ6h/IAIO6+H5rI3VHvh29EDmuG4 U7wCXvN1fjr+w== Message-ID: Date: Mon, 3 Aug 2026 11:18:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 21/26] mm/page_alloc: implement FREETYPE_UNMAPPED allocations Content-Language: en-US To: Brendan Jackman , Borislav Petkov , Dave Hansen , Peter Zijlstra , Andrew Morton , David Hildenbrand , Mike Rapoport , Wei Xu , Johannes Weiner , Zi Yan , Lorenzo Stoakes Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, Sumit Garg , Will Deacon , rientjes@google.com, "Kalyazin, Nikita" , patrick.roy@linux.dev, "Itazuri, Takahiro" , Andy Lutomirski , David Kaplan , Thomas Gleixner , Yosry Ahmed , Patrick Bellasi , Reiji Watanabe , Sean Christopherson References: <20260726-page_alloc-unmapped-v3-0-6f5729aa9832@google.com> <20260726-page_alloc-unmapped-v3-21-6f5729aa9832@google.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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 BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260726-page_alloc-unmapped-v3-21-6f5729aa9832@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: o7bz9o67banbm5bn1o51fnoqsk3dgfym X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 987DF20006 X-HE-Tag: 1785748746-167127 X-HE-Meta: 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 z1YAMknb KsrS8G0K6dhaVbb7kvhmVIG0JQmd0fAM7joTAkqhR8JlKJX9OuvWATRsFGL6VM+oDuUGWIEjNEq9QV2J8Z3soTm4xwZeVrWL+oeFFvjPnU0fT57Xri+nqlsHzQaewE+5WzDcSlLT1XeFKw2xFlowVTz5Z0Adn1oTiCz0yUFt1QiAVTzd5fnygDKB15k4Gck7qk3W+B/i9RIlBDrYTYT9qHvR4EKhcB1PDHd/jJ+SQPQbLAxbQ2dffN0I4szp9DUFH50lUm/yCyGz6WVLttX47RF37CauTgkdkXb4DbpofLEc+kP9FijTsGpai9sgOt+gZwVTz90IeyQobR3jw7UceMuIilwacBI2tOVhE Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/27/26 00:22, Brendan Jackman wrote: > Currently FREETYPE_UNMAPPED allocs will always fail because, although the > lists exist to hold them, there is no way to actually create an unmapped > page block. This commit adds one, and also the logic to map it back > again when that's needed. > > Doing this at pageblock granularity ensures that the pageblock flags can > be used to infer which freetype a page belongs to. It also provides nice > batching of TLB flushes, and also avoids creating too much unnecessary > TLB fragmentation in the physmap. > > There are some functional requirements for flipping a block: > > - Unmapping requires a TLB shootdown, meaning IRQs must be enabled. > > - Updating the pagetables might require allocating a pagetable to break > down a huge page. This would deadlock if the zone lock was held. > > This makes allocations that need to change sensitivity _somewhat_ > similar to those that need to fallback to a different migratetype. But, > the locking requirements mean that this can't just be squashed into the > existing "fallback" allocator logic, instead a new allocator path just > for this purpose is needed. > > The new path is assumed to be much cheaper than the really heavyweight > stuff like compaction and reclaim. But at present it is treated as less > desirable than the mobility-related "fallback" and "stealing" logic. > This might turn out to need revision (in particular, maybe it's a > problem that __rmqueue_steal(), which causes fragmentation, happens > before __rmqueue_direct_map()), but that should be treated as a subsequent > optimisation project. > > Adding alloc_flags to gfp_freetype() requires moving it to > mm/page_alloc.h so it can refer to ALLOC_UNMAPPED. It was already only > used in internal mm code. > > Now that unmapped pageblocks actually exist, exclude them from > migration. Migrating unmapped pages via the mermap should be possible > but that's something to be added later when needed. > > Signed-off-by: Brendan Jackman Reviewed-by: Vlastimil Babka (SUSE) A nit below: > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -34,6 +34,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -1001,6 +1002,26 @@ static void change_pageblock_range(struct page *pageblock_page, > } > } > > +/* > + * Can pages of these two freetypes be combined into a single higher-order free > + * page? > + */ > +static inline bool can_merge_freetypes(freetype_t a, freetype_t b) > +{ > + if (freetypes_equal(a, b)) > + return true; > + > + if (!migratetype_is_mergeable(free_to_migratetype(a)) || > + !migratetype_is_mergeable(free_to_migratetype(b))) > + return false; > + > + /* > + * Mustn't "just" merge pages with different freetype flags, changing > + * those requires updating pagetables. > + */ > + return freetype_flags(a) == freetype_flags(b); > +} > + > /* > * Freeing function for a buddy system allocator. > * > @@ -1069,9 +1090,7 @@ static inline void __free_one_page(struct page *page, > buddy_ft = get_pfnblock_freetype(buddy, buddy_pfn); > buddy_mt = free_to_migratetype(buddy_ft); There's a comment above this that should probably be moved to can_merge_freetypes() as well?