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Mon, 07 Sep 2026 20:04:02 -0700 (PDT) From: Muchun Song To: Andrew Morton , David Hildenbrand , Oscar Salvador , Madhavan Srinivasan , Michael Ellerman , Jonathan Corbet Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org, Muchun Song , Lorenzo Stoakes , Mike Rapoport , Qi Zheng , Nicholas Piggin , Christophe Leroy , Randy Dunlap , Muchun Song Subject: [PATCH v2 01/11] mm/sparse-vmemmap: introduce CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION Date: Tue, 8 Sep 2026 11:03:25 +0800 Message-ID: <20260908030335.96549-2-songmuchun@bytedance.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260908030335.96549-1-songmuchun@bytedance.com> References: <20260908030335.96549-1-songmuchun@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The section-based vmemmap optimization infrastructure is still guarded by CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP, but it also can be used by device DAX. Introduce CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION as a common config for the shared infrastructure. Select the new option from HUGETLB_PAGE_OPTIMIZE_VMEMMAP and from DEV_DAX when the architecture opts in to DAX vmemmap optimization, and use it to guard the generic sparse-vmemmap state and helpers. Signed-off-by: Muchun Song Acked-by: Qi Zheng --- v2: - Fix SPARSEMEM_VMEMMAP_OPTIMIZATION being selected without SPARSEMEM_VMEMMAP reported by Sashiko. - Add an explicit DEV_DAX dependency on ZONE_DEVICE - Collect Acked-by from Qi Zheng --- arch/x86/entry/vdso/vdso32/fake_32bit_build.h | 2 +- drivers/dax/Kconfig | 2 ++ fs/Kconfig | 1 + include/linux/mm.h | 3 +++ include/linux/mmzone.h | 13 +++++++------ include/linux/page-flags.h | 5 ++--- mm/Kconfig | 4 ++++ mm/sparse.h | 4 ++-- 8 files changed, 22 insertions(+), 12 deletions(-) diff --git a/arch/x86/entry/vdso/vdso32/fake_32bit_build.h b/arch/x86/entry/vdso/vdso32/fake_32bit_build.h index bc3e549795c3..5f8424eade2b 100644 --- a/arch/x86/entry/vdso/vdso32/fake_32bit_build.h +++ b/arch/x86/entry/vdso/vdso32/fake_32bit_build.h @@ -11,7 +11,7 @@ #undef CONFIG_PGTABLE_LEVELS #undef CONFIG_ILLEGAL_POINTER_VALUE #undef CONFIG_SPARSEMEM_VMEMMAP -#undef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +#undef CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION #undef CONFIG_NR_CPUS #undef CONFIG_PARAVIRT_XXL diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig index 602f9a0839a9..6250954b0fa7 100644 --- a/drivers/dax/Kconfig +++ b/drivers/dax/Kconfig @@ -8,6 +8,8 @@ if DAX config DEV_DAX tristate "Device DAX: direct access mapping device" depends on TRANSPARENT_HUGEPAGE + depends on ZONE_DEVICE + select SPARSEMEM_VMEMMAP_OPTIMIZATION if ARCH_WANT_OPTIMIZE_DAX_VMEMMAP help Support raw access to differentiated (persistence, bandwidth, latency...) memory via an mmap(2) capable character diff --git a/fs/Kconfig b/fs/Kconfig index d1c210c6508f..9b32ce79cc80 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -278,6 +278,7 @@ config HUGETLB_PAGE_OPTIMIZE_VMEMMAP def_bool HUGETLB_PAGE depends on ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP depends on SPARSEMEM_VMEMMAP + select SPARSEMEM_VMEMMAP_OPTIMIZATION config HUGETLB_PMD_PAGE_TABLE_SHARING def_bool HUGETLB_PAGE diff --git a/include/linux/mm.h b/include/linux/mm.h index c49ef99b4413..a2ebe87e7654 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -5175,6 +5175,9 @@ static inline bool __vmemmap_can_optimize(struct vmem_altmap *altmap, unsigned long nr_pages; unsigned long nr_vmemmap_pages; + if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION)) + return false; + if (!pgmap || !is_power_of_2(sizeof(struct page))) return false; diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index c9ae7991a8b2..e9b54ea0eff0 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -102,9 +102,9 @@ * * HVO which is only active if the size of struct page is a power of 2. */ -#define MAX_FOLIO_VMEMMAP_ALIGN \ - (IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP) && \ - is_power_of_2(sizeof(struct page)) ? \ +#define MAX_FOLIO_VMEMMAP_ALIGN \ + (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION) && \ + is_power_of_2(sizeof(struct page)) ? \ MAX_FOLIO_NR_PAGES * sizeof(struct page) : 0) /* The number of retained vmemmap pages with HVO enabled. */ @@ -116,7 +116,8 @@ #define __VMEMMAP_OPTIMIZATION_NR_ORDERS \ (MAX_FOLIO_ORDER - VMEMMAP_OPTIMIZATION_MIN_ORDER + 1) #define VMEMMAP_OPTIMIZATION_NR_ORDERS \ - (__VMEMMAP_OPTIMIZATION_NR_ORDERS > 0 ? __VMEMMAP_OPTIMIZATION_NR_ORDERS : 0) + ((__VMEMMAP_OPTIMIZATION_NR_ORDERS > 0 && \ + IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION)) ? __VMEMMAP_OPTIMIZATION_NR_ORDERS : 0) enum migratetype { MIGRATE_UNMOVABLE, @@ -1155,7 +1156,7 @@ struct zone { /* Zone statistics */ atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS]; atomic_long_t vm_numa_event[NR_VM_NUMA_EVENT_ITEMS]; -#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +#ifdef CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION struct page *vmemmap_tails[VMEMMAP_OPTIMIZATION_NR_ORDERS]; #endif } ____cacheline_internodealigned_in_smp; @@ -2019,7 +2020,7 @@ struct mem_section { unsigned long section_mem_map; struct mem_section_usage *usage; -#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +#ifdef CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION /* * Normally, sections hold regular (order-0) pages. However, for * sections with HVO enabled, this tracks the compound page order diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 86dd0470da11..462e89e05548 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -208,14 +208,13 @@ enum pageflags { static __always_inline bool compound_info_has_mask(void) { /* - * Limit mask usage to HugeTLB vmemmap optimization (HVO) where it - * makes a difference. + * Limit mask usage to HVO where it makes a difference. * * The approach with mask would work in the wider set of conditions, * but it requires validating that struct pages are naturally aligned * for all orders up to the MAX_FOLIO_ORDER, which can be tricky. */ - if (!IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP)) + if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION)) return false; return is_power_of_2(sizeof(struct page)); diff --git a/mm/Kconfig b/mm/Kconfig index 79163b7d795a..288b32dcc350 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -461,6 +461,10 @@ config SPARSEMEM_VMEMMAP pfn_to_page and page_to_pfn operations. This is the most efficient option when sufficient kernel resources are available. +config SPARSEMEM_VMEMMAP_OPTIMIZATION + bool + depends on SPARSEMEM_VMEMMAP + # # Select this config option from the architecture Kconfig, if it is preferred # to enable the feature of HugeTLB/dev_dax vmemmap optimization. diff --git a/mm/sparse.h b/mm/sparse.h index 049272aba84e..b408d15baf7b 100644 --- a/mm/sparse.h +++ b/mm/sparse.h @@ -10,7 +10,7 @@ #include -#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +#ifdef CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION static inline unsigned int section_order(const struct mem_section *section) { return section->order; @@ -72,7 +72,7 @@ static inline bool vmemmap_optimizable_pfn(unsigned long pfn) static inline bool vmemmap_optimizable_order(unsigned int order) { - if (!IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP)) + if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION)) return false; if (!is_power_of_2(sizeof(struct page))) -- 2.54.0