From: Muchun Song <songmuchun@xxxxxxxxxxxxx> Subject: mm: sparsemem: use huge PMD mapping for vmemmap pages The preparation of splitting huge PMD mapping of vmemmap pages is ready, so switch the mapping from PTE to PMD. Link: https://lkml.kernel.org/r/20210616094915.34432-3-songmuchun@xxxxxxxxxxxxx Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Chen Huang <chenhuang5@xxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxx> Cc: Xiongchun Duan <duanxiongchun@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/admin-guide/kernel-parameters.txt | 7 --- arch/x86/mm/init_64.c | 8 +--- include/linux/hugetlb.h | 25 +++----------- mm/memory_hotplug.c | 2 - 4 files changed, 9 insertions(+), 33 deletions(-) --- a/arch/x86/mm/init_64.c~mm-sparsemem-use-huge-pmd-mapping-for-vmemmap-pages +++ a/arch/x86/mm/init_64.c @@ -34,7 +34,6 @@ #include <linux/gfp.h> #include <linux/kcore.h> #include <linux/bootmem_info.h> -#include <linux/hugetlb.h> #include <asm/processor.h> #include <asm/bios_ebda.h> @@ -1610,8 +1609,7 @@ int __meminit vmemmap_populate(unsigned VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE)); VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE)); - if ((is_hugetlb_free_vmemmap_enabled() && !altmap) || - end - start < PAGES_PER_SECTION * sizeof(struct page)) + if (end - start < PAGES_PER_SECTION * sizeof(struct page)) err = vmemmap_populate_basepages(start, end, node, NULL); else if (boot_cpu_has(X86_FEATURE_PSE)) err = vmemmap_populate_hugepages(start, end, node, altmap); @@ -1639,8 +1637,6 @@ void register_page_bootmem_memmap(unsign pmd_t *pmd; unsigned int nr_pmd_pages; struct page *page; - bool base_mapping = !boot_cpu_has(X86_FEATURE_PSE) || - is_hugetlb_free_vmemmap_enabled(); for (; addr < end; addr = next) { pte_t *pte = NULL; @@ -1666,7 +1662,7 @@ void register_page_bootmem_memmap(unsign } get_page_bootmem(section_nr, pud_page(*pud), MIX_SECTION_INFO); - if (base_mapping) { + if (!boot_cpu_has(X86_FEATURE_PSE)) { next = (addr + PAGE_SIZE) & PAGE_MASK; pmd = pmd_offset(pud, addr); if (pmd_none(*pmd)) --- a/Documentation/admin-guide/kernel-parameters.txt~mm-sparsemem-use-huge-pmd-mapping-for-vmemmap-pages +++ a/Documentation/admin-guide/kernel-parameters.txt @@ -1572,13 +1572,6 @@ enabled. Allows heavy hugetlb users to free up some more memory (6 * PAGE_SIZE for each 2MB hugetlb page). - This feauture is not free though. Large page - tables are not used to back vmemmap pages which - can lead to a performance degradation for some - workloads. Also there will be memory allocation - required when hugetlb pages are freed from the - pool which can lead to corner cases under heavy - memory pressure. Format: { on | off (default) } on: enable the feature --- a/include/linux/hugetlb.h~mm-sparsemem-use-huge-pmd-mapping-for-vmemmap-pages +++ a/include/linux/hugetlb.h @@ -895,20 +895,6 @@ static inline void huge_ptep_modify_prot } #endif -#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP -extern bool hugetlb_free_vmemmap_enabled; - -static inline bool is_hugetlb_free_vmemmap_enabled(void) -{ - return hugetlb_free_vmemmap_enabled; -} -#else -static inline bool is_hugetlb_free_vmemmap_enabled(void) -{ - return false; -} -#endif - #else /* CONFIG_HUGETLB_PAGE */ struct hstate {}; @@ -1063,13 +1049,14 @@ static inline void set_huge_swap_pte_at( pte_t *ptep, pte_t pte, unsigned long sz) { } - -static inline bool is_hugetlb_free_vmemmap_enabled(void) -{ - return false; -} #endif /* CONFIG_HUGETLB_PAGE */ +#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP +extern bool hugetlb_free_vmemmap_enabled; +#else +#define hugetlb_free_vmemmap_enabled false +#endif + static inline spinlock_t *huge_pte_lock(struct hstate *h, struct mm_struct *mm, pte_t *pte) { --- a/mm/memory_hotplug.c~mm-sparsemem-use-huge-pmd-mapping-for-vmemmap-pages +++ a/mm/memory_hotplug.c @@ -1056,7 +1056,7 @@ bool mhp_supports_memmap_on_memory(unsig * populate a single PMD. */ return memmap_on_memory && - !is_hugetlb_free_vmemmap_enabled() && + !hugetlb_free_vmemmap_enabled && IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && size == memory_block_size_bytes() && IS_ALIGNED(vmemmap_size, PMD_SIZE) && _
