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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 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 X-Rspamd-Server: rspam11 X-Stat-Signature: mxte6cnt9sq8jpmri8gstgcng5fd967w X-Rspam-User: X-Rspamd-Queue-Id: B292A140003 X-HE-Tag: 1770223832-707934 X-HE-Meta: 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 zNTLb9/j 3Yz3yVVrIW9sGyVPyh2afMX7j4OVI2uP+m/bDXtI4DGtbZhHcpJ6MLvZ2uhwLhlCti6kiDZ/MfOJIV+ABFVlOYH58nSLHS4v7Sysu1tJC6PV9JYltnSfcgLbrNs7ziqWGydZXwEnTn/ed5HF7o8xnv93JtzrlKjdTyNhPZiN6BK62EUzFpYcEXrQEFijMDFshEGSdnvtNfU/QzqsBqYfCzYv7M99jKn2UbDYfffcOk5g7k/JHp16LCR3cB7EZk3qIf+GHW2i8Os8fDL+GAI8XoMDrmLeCfkkry+Ff X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 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