From: Huang Ying <[email protected]> Previously, to reclaim MADV_FREE THP, the THP will be split firstly, then reclaim each sub-pages. This wastes cycles to split THP and unmap and free each sub-pages, and split THP even if it has been written since MADV_FREE. We have to do this because MADV_FREE THP reclaiming shares same try_to_unmap() calling with swap, while swap needs to split the PMD page mapping at that time. Now swap can process PMD mapping, this makes it easy to avoid to split THP when MADV_FREE THP is reclaimed.
Signed-off-by: "Huang, Ying" <[email protected]> Cc: "Kirill A. Shutemov" <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Johannes Weiner <[email protected]> Cc: Shaohua Li <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Minchan Kim <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Naoya Horiguchi <[email protected]> Cc: Zi Yan <[email protected]> --- mm/huge_memory.c | 41 ++++++++++++++++++++++++++++++++--------- mm/vmscan.c | 3 ++- 2 files changed, 34 insertions(+), 10 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 8f2a4022d211..9f786f7feb51 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1674,6 +1674,15 @@ int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) return 0; } +static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) +{ + pgtable_t pgtable; + + pgtable = pgtable_trans_huge_withdraw(mm, pmd); + pte_free(mm, pgtable); + mm_dec_nr_ptes(mm); +} + #ifdef CONFIG_THP_SWAP void __split_huge_swap_pmd(struct vm_area_struct *vma, unsigned long haddr, @@ -1889,6 +1898,28 @@ bool set_pmd_swap_entry(struct page_vma_mapped_walk *pvmw, struct page *page, pmd_t swp_pmd; swp_entry_t entry = { .val = page_private(page) }; + if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) { + WARN_ON_ONCE(1); + return false; + } + + /* MADV_FREE page check */ + if (!PageSwapBacked(page)) { + if (!PageDirty(page)) { + zap_deposited_table(mm, pvmw->pmd); + add_mm_counter(mm, MM_ANONPAGES, -HPAGE_PMD_NR); + goto out_remove_rmap; + } + + /* + * If the page was redirtied, it cannot be + * discarded. Remap the page to page table. + */ + set_pmd_at(mm, address, pvmw->pmd, pmdval); + SetPageSwapBacked(page); + return false; + } + if (swap_duplicate(&entry, true) < 0) { set_pmd_at(mm, address, pvmw->pmd, pmdval); return false; @@ -1906,21 +1937,13 @@ bool set_pmd_swap_entry(struct page_vma_mapped_walk *pvmw, struct page *page, swp_pmd = pmd_swp_mksoft_dirty(swp_pmd); set_pmd_at(mm, address, pvmw->pmd, swp_pmd); +out_remove_rmap: page_remove_rmap(page, true); put_page(page); return true; } #endif -static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) -{ - pgtable_t pgtable; - - pgtable = pgtable_trans_huge_withdraw(mm, pmd); - pte_free(mm, pgtable); - mm_dec_nr_ptes(mm); -} - /* * Return true if we do MADV_FREE successfully on entire pmd page. * Otherwise, return false. diff --git a/mm/vmscan.c b/mm/vmscan.c index e4ec579a11a2..9d5151d0abdb 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1118,7 +1118,8 @@ static unsigned long shrink_page_list(struct list_head *page_list, /* Adding to swap updated mapping */ mapping = page_mapping(page); } - } else if (unlikely(PageTransHuge(page))) { + } else if (unlikely(PageTransHuge(page)) && + (!thp_swap_supported() || !PageAnon(page))) { /* Split file THP */ if (split_huge_page_to_list(page, page_list)) goto keep_locked; -- 2.17.0
