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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2FA0EEC1EB9 for ; Thu, 5 Feb 2026 13:55:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=1vMqICJDWuCxQ/M5hVRJI2BPVsEyEKjlk3wI2fh1zDM=; b=qL1kROqRAwqOki P/3uDFZZtZGLPk6m0WU/I2PhrUukagJddkWAiVVunsjE0pVSaksSvPCa5Ui+DmOY5i4cDu4zrH8Qn KT4hQMsGrXCAlKpfvyJ9RBGMEJrXs7TmRKRycN6Ro4WHWL0D6C/mkC2njIdf4l1I2dBwUNn+c/q9v 0Pf9e0UEQzbpPSEPOzIPGAmWcx9eGFW6vv2wT9AFJEA8UiH4isRTj3hCijvWwiPjVIB3jFSlM9nse WEA/Rj+WFkndji4C6bC4KQl/7K3qFxdFYXW/J6Nn/5SVi39QKL87BMA7HzeZlazPmXTOFpvHtw/CE xlAyFheCqrj0wRExOPYA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vnzp0-00000009zrC-3Ust; Thu, 05 Feb 2026 13:55:02 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vnzoy-00000009zqO-1NPd for linux-riscv@lists.infradead.org; Thu, 05 Feb 2026 13:55:01 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 310E343C74; Thu, 5 Feb 2026 13:54:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 00BBDC4CEF7; Thu, 5 Feb 2026 13:54:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770299699; bh=sFil3yu86GERvqyxBASqk6D+b92nzCIAxVRDzXFk5IE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=VVxV98426Dh4XEprkhO91xKxeVP1Npp1yUwzn3nwz3RVGemzysZC6GWZIpGvjw9jj QmSyc6sxsBqFRjV4mF8OH8LOYc675cgH1vSsOOGBsEvavV8rsZfEdh08n3Z9ny1swQ QIrrQJBoL3WAgulMHMBcV8GaAtZvYTC1wnWKl/Q2N7b1eBQpA+qqvTv5K87WGlWbfA lTFLgWuRrYh1ejR45a70HRnbd+9Sofv5aszwiUMTOB30+16EhwvH4vYVFA+6ES/1QU 7VSVmcUn+x1bqVi9f9woMoqXOdgGfGUOTgO90Wsrpw4q6gfowvKjxTh5WSmGQoWPr0 VXfHz2EgbE6AA== Message-ID: Date: Thu, 5 Feb 2026 14:54:51 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv6 05/17] riscv/mm: Align vmemmap to maximal folio size To: Kiryl Shutsemau Cc: Andrew Morton , Muchun Song , Matthew Wilcox , Usama Arif , Frank van der Linden , Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , Huacai Chen , WANG Xuerui , Palmer Dabbelt , Paul Walmsley , Albert Ou , Alexandre Ghiti , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org References: <20260202155634.650837-1-kas@kernel.org> <20260202155634.650837-6-kas@kernel.org> <1b80b189-b549-40ba-800c-8037ce12b081@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset="us-ascii"; Format="flowed" Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On 2/5/26 14:50, Kiryl Shutsemau wrote: > On Wed, Feb 04, 2026 at 05:50:23PM +0100, David Hildenbrand (arm) wrote: >> On 2/2/26 16:56, Kiryl Shutsemau wrote: >>> The upcoming change to the HugeTLB vmemmap optimization (HVO) requires >>> struct pages of the head page to be naturally aligned with regard to the >>> folio size. >>> >>> Align vmemmap to MAX_FOLIO_NR_PAGES. >> >> I think neither that statement nor the one in the patch description is >> correct? >> >> "MAX_FOLIO_NR_PAGES * sizeof(struct page)" is neither the maximum folio size >> nor MAX_FOLIO_NR_PAGES. >> >> It's the size of the memmap that a large folio could span at maximum. >> >> >> Assuming we have a 16 GiB folio, the calculation would give us >> >> 4194304 * sizeof(struct page) >> >> Which could be something like (assuming 80 bytes) >> >> 335544320 >> >> -> not even a power of 2, weird? (for HVO you wouldn't care as HVO would be >> disabled, but that aliment is super weird?) >> >> >> Assuming 64 bytes, it would be a power of two (as 64 is a power of two). >> >> 268435456 (1<< 28) >> >> >> Which makes me wonder whether there is a way to avoid sizeof(struct page) >> here completely. > > I don't think we can. See the other thread. Agreed. You could only go for something larger (like PAGE_SIZE). > > What about using roundup_pow_of_two(sizeof(struct page)) here. Better I think. > >> Or limit the alignment to the case where HVO is actually active and >> sizeof(struct page) makes any sense? > > The annoying part of HVO is that it is unknown at compile-time if it > will be used. You can compile kernel with HVO that will no be activated > due to non-power-of-2 sizeof(struct page) because of a debug config option. Ah, and now I remember that sizeof cannot be used in macros, damnit. -- Cheers, David _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv