From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E88D130497C; Wed, 4 Feb 2026 16:50:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770223832; cv=none; b=BPpNiXkjsDogomMwC/3k87ZyGFdHaLyWEkVA7FCAmzqOg+171ZcvaMpp6DLw6sBx0YMjvjHqL1yDlFIVOyS1tpuZywnso20Sd9S0lI93G0AR1x1I8lIQoBKis4KN/UxvWVYjARJotffw6Ws0voiEtWv9bukyxrzjh/KM9KnA5DI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770223832; c=relaxed/simple; bh=fd9mB6uxi20UpngRQKWBUIqmPqpBhJ06BLLPzdm+xN8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=fz08PosMp8tEv1f5CqxzBLbYST8CKbxSBuRD7UjcuUoXGTQs1X+lWn6w2sUgLPwcwFxHFA6CFZ/cJvpaIxlV3OAeM/rtffvc+7tSRH75TnUBN54w3pDaSQ+4sSjPP4N5OIaI0Q5Gei8eKdosDjri8RLuG7ry0hBS+9xla9Ym2fA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KvP2Ej0r; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KvP2Ej0r" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81F69C4CEF7; Wed, 4 Feb 2026 16:50:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770223831; bh=fd9mB6uxi20UpngRQKWBUIqmPqpBhJ06BLLPzdm+xN8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=KvP2Ej0r49rqN3zlMVpi7wdZOiGb5ddjkwluNNwr9i65tfI+kq4umf0NzPJuSsz8p P6qg5MuNuC/5M3knmpbfL5L40N42mK4CxEuRfEkEvj5XMAVFGkQ5ALUg/vIDbzsrpn //iCatRb0KhDzkd/uzYZNxOW53aznd3RDzb/Zz2Zl7jilmlNc1PgoPNluqUj5Pdz/2 6b47830F8Tvk2zwwsSlOD9haOzCh25eYY3PiIsZkPeucUqpGe9bEw1u0YDXiUIHiK+ uatWn5zfW2IwFwvhWhhIepkHH5jQtDQ0ES43T91LXVz3v288R1X14ywTluExwNxg70 eVR618or/n1mg== Message-ID: <1b80b189-b549-40ba-800c-8037ce12b081@kernel.org> Date: Wed, 4 Feb 2026 17:50:23 +0100 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv6 05/17] riscv/mm: Align vmemmap to maximal folio size To: Kiryl Shutsemau , Andrew Morton , Muchun Song , Matthew Wilcox , Usama Arif , Frank van der Linden Cc: 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> From: "David Hildenbrand (arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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. Or limit the alignment to the case where HVO is actually active and sizeof(struct page) makes any sense? > > Signed-off-by: Kiryl Shutsemau > --- > arch/riscv/mm/init.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index 21d534824624..c555b9a4fdce 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -63,7 +63,8 @@ phys_addr_t phys_ram_base __ro_after_init; > EXPORT_SYMBOL(phys_ram_base); > > #ifdef CONFIG_SPARSEMEM_VMEMMAP > -#define VMEMMAP_ADDR_ALIGN (1ULL << SECTION_SIZE_BITS) > +#define VMEMMAP_ADDR_ALIGN max(1ULL << SECTION_SIZE_BITS, \ > + MAX_FOLIO_NR_PAGES * sizeof(struct page)) > > unsigned long vmemmap_start_pfn __ro_after_init; > EXPORT_SYMBOL(vmemmap_start_pfn); -- Cheers, David