From f41f2ed43ca5258d70d53290d1951a21621f95c8 Mon Sep 17 00:00:00 2001 From: Muchun Song Date: Wed, 30 Jun 2021 18:47:13 -0700 Subject: mm: hugetlb: free the vmemmap pages associated with each HugeTLB page Every HugeTLB has more than one struct page structure. We __know__ that we only use the first 4 (__NR_USED_SUBPAGE) struct page structures to store metadata associated with each HugeTLB. There are a lot of struct page structures associated with each HugeTLB page. For tail pages, the value of compound_head is the same. So we can reuse first page of tail page structures. We map the virtual addresses of the remaining pages of tail page structures to the first tail page struct, and then free these page frames. Therefore, we need to reserve two pages as vmemmap areas. When we allocate a HugeTLB page from the buddy, we can free some vmemmap pages associated with each HugeTLB page. It is more appropriate to do it in the prep_new_huge_page(). The free_vmemmap_pages_per_hpage(), which indicates how many vmemmap pages associated with a HugeTLB page can be freed, returns zero for now, which means the feature is disabled. We will enable it once all the infrastructure is there. [willy@infradead.org: fix documentation warning] Link: https://lkml.kernel.org/r/20210615200242.1716568-5-willy@infradead.org Link: https://lkml.kernel.org/r/20210510030027.56044-5-songmuchun@bytedance.com Signed-off-by: Muchun Song Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Oscar Salvador Tested-by: Chen Huang Tested-by: Bodeddula Balasubramaniam Acked-by: Michal Hocko Reviewed-by: Mike Kravetz Cc: Alexander Viro Cc: Andy Lutomirski Cc: Anshuman Khandual Cc: Balbir Singh Cc: Barry Song Cc: Borislav Petkov Cc: Dave Hansen Cc: David Hildenbrand Cc: David Rientjes Cc: HORIGUCHI NAOYA Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Joao Martins Cc: Joerg Roedel Cc: Jonathan Corbet Cc: Matthew Wilcox Cc: Miaohe Lin Cc: Mina Almasry Cc: Oliver Neukum Cc: Paul E. McKenney Cc: Pawan Gupta Cc: Peter Zijlstra Cc: Randy Dunlap Cc: Thomas Gleixner Cc: Xiongchun Duan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/hugetlb_vmemmap.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) create mode 100644 mm/hugetlb_vmemmap.h (limited to 'mm/hugetlb_vmemmap.h') diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h new file mode 100644 index 000000000000..6923f03534d5 --- /dev/null +++ b/mm/hugetlb_vmemmap.h @@ -0,0 +1,20 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Free some vmemmap pages of HugeTLB + * + * Copyright (c) 2020, Bytedance. All rights reserved. + * + * Author: Muchun Song + */ +#ifndef _LINUX_HUGETLB_VMEMMAP_H +#define _LINUX_HUGETLB_VMEMMAP_H +#include + +#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP +void free_huge_page_vmemmap(struct hstate *h, struct page *head); +#else +static inline void free_huge_page_vmemmap(struct hstate *h, struct page *head) +{ +} +#endif /* CONFIG_HUGETLB_PAGE_FREE_VMEMMAP */ +#endif /* _LINUX_HUGETLB_VMEMMAP_H */ -- cgit