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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=rQ4i2MP/E8rGhbitmZxBMF/eBICIDl4M9VpN0LVW/s45WpNvdHjMQvfUFGYkVZKLC K6dRT3KTvI9iWA+dVcIejo09e7sjeTMQUeQphJtTliE0mP9yWN86gGssY2NprEypZ+ 7PcsDpK5swHcKJJJXdkFPTHN+fe2i0JNkVH6l2lA= Message-ID: <71e8601c-ce7e-4a4e-aa0e-66c9f2a5c9b5@arm.com> Date: Wed, 15 Jul 2026 09:01:39 +0530 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 v6 2/6] arm64/vmalloc: Allow arch_vmap_pte_range_map_size to batch multiple CONT_PTE To: Wen Jiang Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, linux-mm@kvack.org, urezki@gmail.com, will@kernel.org, Xueyuan.chen21@gmail.com, ajd@linux.ibm.com, david@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, rppt@kernel.org, ryan.roberts@arm.com, dev.jain@arm.com, "Barry Song (Xiaomi)" , Wen Jiang , Leo Yan References: <20260709073823.6643-1-jiangwen6@xiaomi.com> <20260709073823.6643-3-jiangwen6@xiaomi.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 15/07/26 8:19 AM, Wen Jiang wrote: > On Tue, 14 Jul 2026 at 17:24, Wen Jiang wrote: >> >> On Tue, 14 Jul 2026 at 15:13, Anshuman Khandual >> wrote: >>> >>> >>> >>> On 09/07/26 1:08 PM, Wen Jiang wrote: >>>> From: "Barry Song (Xiaomi)" >>>> >>>> Allow arch_vmap_pte_range_map_size to batch across multiple CONT_PTE >>>> blocks, reducing both PTE setup and TLB flush iterations. >>> >>> Too little commit description for the proposed change here. >>>> >>>> Signed-off-by: Barry Song (Xiaomi) >>>> Signed-off-by: Wen Jiang >>>> Tested-by: Xueyuan Chen >>>> Tested-by: Leo Yan >>>> Reviewed-by: Dev Jain >>>> --- >>>> arch/arm64/include/asm/vmalloc.h | 6 +++++- >>>> 1 file changed, 5 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/arch/arm64/include/asm/vmalloc.h b/arch/arm64/include/asm/vmalloc.h >>>> index 4ec1acd3c1b34..7d9c7dc795c42 100644 >>>> --- a/arch/arm64/include/asm/vmalloc.h >>>> +++ b/arch/arm64/include/asm/vmalloc.h >>>> @@ -23,6 +23,8 @@ static inline unsigned long arch_vmap_pte_range_map_size(unsigned long addr, >>>> unsigned long end, u64 pfn, >>>> unsigned int max_page_shift) >>>> { >>>> + unsigned long size; >>>> + >>>> /* >>>> * If the block is at least CONT_PTE_SIZE in size, and is naturally >>>> * aligned in both virtual and physical space, then we can pte-map the >>>> @@ -40,7 +42,9 @@ static inline unsigned long arch_vmap_pte_range_map_size(unsigned long addr, >>>> if (!IS_ALIGNED(PFN_PHYS(pfn), CONT_PTE_SIZE)) >>>> return PAGE_SIZE; >>>> >>>> - return CONT_PTE_SIZE; >>>> + size = min3(end - addr, 1UL << max_page_shift, PMD_SIZE >> 1); >>>> + size = rounddown_pow_of_two(size); >>>> + return size; >>> >>> Please do explain the fact in a comment that huge pte mappings >>> upto PMD_SIZE are being allowed here, if the given block is >>> CONT_PTE_SIZE aligned. >>> > > Hi Anshuman, > > Would the following comment address your concern? > > diff --git a/arch/arm64/include/asm/vmalloc.h b/arch/arm64/include/asm/vmalloc.h > --- a/arch/arm64/include/asm/vmalloc.h > +++ b/arch/arm64/include/asm/vmalloc.h > @@ -29,6 +29,8 @@ static inline unsigned long > arch_vmap_pte_range_map_size(unsigned long addr, > * If the block is at least CONT_PTE_SIZE in size, and is naturally > * aligned in both virtual and physical space, then we can pte-map the > * block using the PTE_CONT bit for more efficient use of the TLB. > + * The returned mapping size may cover multiple CONT_PTE_SIZE blocks, > + * capped below PMD_SIZE. Yes sounds good. > */ > if (max_page_shift < CONT_PTE_SHIFT) > return PAGE_SIZE; > >>> IIUC arch_vmap_pte_range_map_size() gets used only when config >>> CONFIG_HUGETLB_PAGE is enabled. Hence should not these new huge >>> sizes being supported here also be added as valid HugeTLB sizes >>> thus updating __hugetlb_valid_size() and adding corresponding >>> new HugeTLB page sizes with hugetlb_add_hstate() ? >>> >>> OR could arch_vmap_pte_range_map_size() and set_huge_pte_at() >>> can be updated for vmalloc without doing corresponding changes >>> into HugeTLB itself ? >> >> These sizes are not new HugeTLB page sizes. They are only vmalloc mapping >> spans selected for a particular virtually and physically aligned range, so that >> the PTEs can be installed with the contiguous bit in larger batches. >> >> Therefore I do not think they should be added to __hugetlb_valid_size() or >> registered with hugetlb_add_hstate(). Those describe the HugeTLB hstate sizes, >> while this change only affects how vmalloc chooses the PTE-level mapping span. >> >> Thanks, >> Wen >>>> } >>>> >>>> #define arch_vmap_pte_range_unmap_size arch_vmap_pte_range_unmap_size >>>