mm/hugetlb_vmemmap.h

   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 #ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
  14 int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head);
  15 void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head);
  16
  17 /*
  18  * Reserve one vmemmap page, all vmemmap addresses are mapped to it. See
  19  * Documentation/vm/vmemmap_dedup.rst.
  20  */
  21 #define HUGETLB_VMEMMAP_RESERVE_SIZE    PAGE_SIZE
  22
  23 static inline unsigned int hugetlb_vmemmap_size(const struct hstate *h)
  24 {
  25         return pages_per_huge_page(h) * sizeof(struct page);
  26 }
  27
  28 /*
  29  * Return how many vmemmap size associated with a HugeTLB page that can be
  30  * optimized and can be freed to the buddy allocator.
  31  */
  32 static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
  33 {
  34         int size = hugetlb_vmemmap_size(h) - HUGETLB_VMEMMAP_RESERVE_SIZE;
  35
  36         if (!is_power_of_2(sizeof(struct page)))
  37                 return 0;
  38         return size > 0 ? size : 0;
  39 }
  40 #else
  41 static inline int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
  42 {
  43         return 0;
  44 }
  45
  46 static inline void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
  47 {
  48 }
  49
  50 static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
  51 {
  52         return 0;
  53 }
  54 #endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */
  55
  56 static inline bool hugetlb_vmemmap_optimizable(const struct hstate *h)
  57 {
  58         return hugetlb_vmemmap_optimizable_size(h) != 0;
  59 }
  60 #endif /* _LINUX_HUGETLB_VMEMMAP_H */