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b=AaNPuBUaXfkXKF6L293sg4La152kF9SYon65H25RqbxF4jVF2jFvXi18CcDRwfWhi wv0130+KWysnx0l4YB6VKqwgbMFpsc9UA2OKhPkVYGqxsg8wD8LqHtZgIAVP1Owloc hfY0DHS4zqgTZSomdebsvxMCn5S9l0oD0ciFxm0Y= Date: Wed, 16 Sep 2026 18:35:45 -0700 From: Andrew Morton To: Muchun Song Cc: David Hildenbrand , Oscar Salvador , Madhavan Srinivasan , Michael Ellerman , Jonathan Corbet , 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 Subject: Re: [PATCH v4 00/11] mm: Switch device DAX to section-based vmemmap optimization Message-Id: <20260916183545.b8244db6aa2caf783b1fa5e9@linux-foundation.org> In-Reply-To: <20260916064341.1825793-1-songmuchun@bytedance.com> References: <20260916064341.1825793-1-songmuchun@bytedance.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: 4igr7a7joozwpcbusgiy8txwe6hjaj9x X-Rspam-User: X-Rspamd-Queue-Id: 2D61240009 X-Rspamd-Server: rspam03 X-HE-Tag: 1789608947-203172 X-HE-Meta: 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 snrOPQw6 I7uJlV78EPbCZWvZRU5vVRmU05+LPNi1OVH1q1+Qy8BayEwrMkxSF8Xn7QSSa7rh7mWdPHa3E+PADxsr2sotoTbnj3EemABZ5wfCMdlC9UxrvO94dqYGVVBNng0YpgNFPKw3D6Bn7m6JDNJTR5eYxiQwaWEKdTfAZoTGRFoS3pArZVYyfza/SHPAMXNLT/D+2wB8VxzXvjHMXl0ADxMa/A6x/DtiEIp1pWczsywcEOKBMITKVJbMwnZZgMorlejQhCs8lWA1CXJ/tYMzCUan5v5oNGw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 16 Sep 2026 14:43:30 +0800 Muchun Song wrote: > This series is split out from the earlier, larger series "mm: Generalize > HVO for HugeTLB and device DAX" [1]. While the parent series generalizes > vmemmap optimization across HugeTLB and device DAX, this subset addresses > a single, self-contained step: switching device DAX to the section-based > sparse-vmemmap optimization infrastructure introduced for HugeTLB. > > After the HugeTLB conversion, optimized vmemmap state is described by > the memory section and the sparse-vmemmap population path can allocate or > reuse shared tail vmemmap pages based on that metadata. Device DAX still > uses the older DAX-specific population model, including a separate tail > vmemmap page reservation and architecture-specific logic to locate or > populate reusable tail pages. > > ... > > This is intended to be the third smaller step toward the broader HVO > generalization. The wider HVO consolidation between HugeTLB and device > DAX is left for follow-up series. Thanks, I updated mm-unstable to this version. > v4: > - Rename CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION to > CONFIG_VMEMMAP_OPTIMIZATION (suggested by Mike Rapoport) > - Collect Acked-by tags from Mike Rapoport > Here's how v4 altered mm.git: arch/x86/entry/vdso/vdso32/fake_32bit_build.h | 2 +- drivers/dax/Kconfig | 2 -- fs/Kconfig | 2 +- include/linux/mm.h | 2 +- include/linux/mmzone.h | 6 +++--- include/linux/page-flags.h | 2 +- include/linux/vmemmap-optimization.h | 6 +++--- mm/Kconfig | 3 ++- 8 files changed, 12 insertions(+), 13 deletions(-) --- a/arch/x86/entry/vdso/vdso32/fake_32bit_build.h~b +++ a/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_SPARSEMEM_VMEMMAP_OPTIMIZATION +#undef CONFIG_VMEMMAP_OPTIMIZATION #undef CONFIG_NR_CPUS #undef CONFIG_PARAVIRT_XXL --- a/drivers/dax/Kconfig~b +++ a/drivers/dax/Kconfig @@ -8,8 +8,6 @@ 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 --- a/fs/Kconfig~b +++ a/fs/Kconfig @@ -278,7 +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 + select VMEMMAP_OPTIMIZATION config HUGETLB_PMD_PAGE_TABLE_SHARING def_bool HUGETLB_PAGE --- a/include/linux/mm.h~b +++ a/include/linux/mm.h @@ -5174,7 +5174,7 @@ static inline bool __vmemmap_can_optimiz unsigned long nr_pages; unsigned long nr_vmemmap_pages; - if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION)) + if (!IS_ENABLED(CONFIG_VMEMMAP_OPTIMIZATION)) return false; if (!pgmap || !is_power_of_2(sizeof(struct page))) --- a/include/linux/mmzone.h~b +++ a/include/linux/mmzone.h @@ -103,7 +103,7 @@ * HVO which is only active if the size of struct page is a power of 2. */ #define MAX_FOLIO_VMEMMAP_ALIGN \ - (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION) && \ + (IS_ENABLED(CONFIG_VMEMMAP_OPTIMIZATION) && \ is_power_of_2(sizeof(struct page)) ? \ MAX_FOLIO_NR_PAGES * sizeof(struct page) : 0) @@ -117,7 +117,7 @@ (MAX_FOLIO_ORDER - VMEMMAP_OPTIMIZATION_MIN_ORDER + 1) #define VMEMMAP_OPTIMIZATION_NR_ORDERS \ ((__VMEMMAP_OPTIMIZATION_NR_ORDERS > 0 && \ - IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION)) ? __VMEMMAP_OPTIMIZATION_NR_ORDERS : 0) + IS_ENABLED(CONFIG_VMEMMAP_OPTIMIZATION)) ? __VMEMMAP_OPTIMIZATION_NR_ORDERS : 0) enum migratetype { MIGRATE_UNMOVABLE, @@ -2020,7 +2020,7 @@ struct mem_section { unsigned long section_mem_map; struct mem_section_usage *usage; -#ifdef CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION +#ifdef CONFIG_VMEMMAP_OPTIMIZATION /* * Normally, sections hold regular (order-0) pages. However, for * sections with HVO enabled, this tracks the compound page order --- a/include/linux/page-flags.h~b +++ a/include/linux/page-flags.h @@ -214,7 +214,7 @@ static __always_inline bool compound_inf * 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_SPARSEMEM_VMEMMAP_OPTIMIZATION)) + if (!IS_ENABLED(CONFIG_VMEMMAP_OPTIMIZATION)) return false; return is_power_of_2(sizeof(struct page)); --- a/include/linux/vmemmap-optimization.h~b +++ a/include/linux/vmemmap-optimization.h @@ -14,7 +14,7 @@ #include #include -#ifdef CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION +#ifdef CONFIG_VMEMMAP_OPTIMIZATION static inline unsigned int section_compound_order(const struct mem_section *section) { return section->compound_page_order; @@ -64,7 +64,7 @@ static inline unsigned int pfn_to_sectio { return 0; } -#endif /* CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION */ +#endif /* CONFIG_VMEMMAP_OPTIMIZATION */ static inline bool vmemmap_optimizable_pfn(unsigned long pfn) { @@ -79,7 +79,7 @@ static inline bool vmemmap_optimizable_p static inline bool vmemmap_optimizable_order(unsigned int order) { - if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION)) + if (!IS_ENABLED(CONFIG_VMEMMAP_OPTIMIZATION)) return false; if (!is_power_of_2(sizeof(struct page))) --- a/mm/Kconfig~b +++ a/mm/Kconfig @@ -461,7 +461,7 @@ 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 +config VMEMMAP_OPTIMIZATION bool depends on SPARSEMEM_VMEMMAP @@ -1224,6 +1224,7 @@ config ZONE_DMA32 config ZONE_DEVICE bool "Device memory (pmem, HMM, etc...) hotplug support" depends on MEMORY_HOTREMOVE + select VMEMMAP_OPTIMIZATION if ARCH_WANT_OPTIMIZE_DAX_VMEMMAP select XARRAY_MULTI help _