1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * HugeTLB Vmemmap Optimization (HVO) 4 * 5 * Copyright (c) 2020, ByteDance. All rights reserved. 6 * 7 * Author: Muchun Song <songmuchun@bytedance.com> 8 */ 9 #ifndef _LINUX_HUGETLB_VMEMMAP_H 10 #define _LINUX_HUGETLB_VMEMMAP_H 11 #include <linux/hugetlb.h> 12 13 /* 14 * Reserve one vmemmap page, all vmemmap addresses are mapped to it. See 15 * Documentation/vm/vmemmap_dedup.rst. 16 */ 17 #define HUGETLB_VMEMMAP_RESERVE_SIZE PAGE_SIZE 18 #define HUGETLB_VMEMMAP_RESERVE_PAGES (HUGETLB_VMEMMAP_RESERVE_SIZE / sizeof(struct page)) 19 20 #ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP 21 int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head); 22 void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head); 23 24 static inline unsigned int hugetlb_vmemmap_size(const struct hstate *h) 25 { 26 return pages_per_huge_page(h) * sizeof(struct page); 27 } 28 29 /* 30 * Return how many vmemmap size associated with a HugeTLB page that can be 31 * optimized and can be freed to the buddy allocator. 32 */ 33 static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h) 34 { 35 int size = hugetlb_vmemmap_size(h) - HUGETLB_VMEMMAP_RESERVE_SIZE; 36 37 if (!is_power_of_2(sizeof(struct page))) 38 return 0; 39 return size > 0 ? size : 0; 40 } 41 #else 42 static inline int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head) 43 { 44 return 0; 45 } 46 47 static inline void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head) 48 { 49 } 50 51 static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h) 52 { 53 return 0; 54 } 55 #endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */ 56 57 static inline bool hugetlb_vmemmap_optimizable(const struct hstate *h) 58 { 59 return hugetlb_vmemmap_optimizable_size(h) != 0; 60 } 61 #endif /* _LINUX_HUGETLB_VMEMMAP_H */ 62