From 9cb28da54643ad464c47585cd5866c30b0218e67 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Wed, 27 Mar 2024 11:23:32 -0400 Subject: mm/gup: handle hugetlb in the generic follow_page_mask code Now follow_page() is ready to handle hugetlb pages in whatever form, and over all architectures. Switch to the generic code path. Time to retire hugetlb_follow_page_mask(), following the previous retirement of follow_hugetlb_page() in 4849807114b8. There may be a slight difference of how the loops run when processing slow GUP over a large hugetlb range on cont_pte/cont_pmd supported archs: each loop of __get_user_pages() will resolve one pgtable entry with the patch applied, rather than relying on the size of hugetlb hstate, the latter may cover multiple entries in one loop. A quick performance test on an aarch64 VM on M1 chip shows 15% degrade over a tight loop of slow gup after the path switched. That shouldn't be a problem because slow-gup should not be a hot path for GUP in general: when page is commonly present, fast-gup will already succeed, while when the page is indeed missing and require a follow up page fault, the slow gup degrade will probably buried in the fault paths anyway. It also explains why slow gup for THP used to be very slow before 57edfcfd3419 ("mm/gup: accelerate thp gup even for "pages != NULL"") lands, the latter not part of a performance analysis but a side benefit. If the performance will be a concern, we can consider handle CONT_PTE in follow_page(). Before that is justified to be necessary, keep everything clean and simple. Link: https://lkml.kernel.org/r/20240327152332.950956-14-peterx@redhat.com Signed-off-by: Peter Xu Reviewed-by: Jason Gunthorpe Tested-by: Ryan Roberts Cc: Andrea Arcangeli Cc: Andrew Jones Cc: Aneesh Kumar K.V (IBM) Cc: Axel Rasmussen Cc: Christophe Leroy Cc: Christoph Hellwig Cc: David Hildenbrand Cc: James Houghton Cc: John Hubbard Cc: Kirill A. Shutemov Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michael Ellerman Cc: "Mike Rapoport (IBM)" Cc: Muchun Song Cc: Rik van Riel Cc: Vlastimil Babka Cc: Yang Shi Signed-off-by: Andrew Morton --- include/linux/hugetlb.h | 7 ------- 1 file changed, 7 deletions(-) (limited to 'include/linux/hugetlb.h') diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index a7988c78d69f..3f3e62880279 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -328,13 +328,6 @@ static inline void hugetlb_zap_end( { } -static inline struct page *hugetlb_follow_page_mask( - struct vm_area_struct *vma, unsigned long address, unsigned int flags, - unsigned int *page_mask) -{ - BUILD_BUG(); /* should never be compiled in if !CONFIG_HUGETLB_PAGE*/ -} - static inline int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, struct vm_area_struct *dst_vma, -- cgit v1.2.3-59-g8ed1b