From 8a966ed746d63c8103d496da85973eeeec01d77f Mon Sep 17 00:00:00 2001 From: Ebru Akagunduz Date: Tue, 26 Jul 2016 15:25:03 -0700 Subject: [PATCH] mm: make swapin readahead to improve thp collapse rate This patch makes swapin readahead to improve thp collapse rate. When khugepaged scanned pages, there can be a few of the pages in swap area. With the patch THP can collapse 4kB pages into a THP when there are up to max_ptes_swap swap ptes in a 2MB range. The patch was tested with a test program that allocates 400B of memory, writes to it, and then sleeps. I force the system to swap out all. Afterwards, the test program touches the area by writing, it skips a page in each 20 pages of the area. Without the patch, system did not swap in readahead. THP rate was %65 of the program of the memory, it did not change over time. With this patch, after 10 minutes of waiting khugepaged had collapsed %99 of the program's memory. [kirill.shutemov@linux.intel.com: trivial cleanup of exit path of the function] [kirill.shutemov@linux.intel.com: __collapse_huge_page_swapin(): drop unused 'pte' parameter] [kirill.shutemov@linux.intel.com: do not hold anon_vma lock during swap in] Signed-off-by: Ebru Akagunduz Acked-by: Rik van Riel Cc: Naoya Horiguchi Cc: Andrea Arcangeli Cc: Joonsoo Kim Cc: Xie XiuQi Cc: Cyrill Gorcunov Cc: Mel Gorman Cc: David Rientjes Cc: Vlastimil Babka Cc: Aneesh Kumar K.V Cc: Hugh Dickins Cc: Johannes Weiner Cc: Michal Hocko Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/trace/events/huge_memory.h | 24 +++++++++++++++++++++ mm/huge_memory.c | 43 +++++++++++++++++++++++++++++++++++--- mm/internal.h | 4 ++++ mm/memory.c | 2 +- 4 files changed, 69 insertions(+), 4 deletions(-) diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h index fad6539..bda2118 100644 --- a/include/trace/events/huge_memory.h +++ b/include/trace/events/huge_memory.h @@ -135,5 +135,29 @@ TRACE_EVENT(mm_collapse_huge_page_isolate, __print_symbolic(__entry->status, SCAN_STATUS)) ); +TRACE_EVENT(mm_collapse_huge_page_swapin, + + TP_PROTO(struct mm_struct *mm, int swapped_in, int ret), + + TP_ARGS(mm, swapped_in, ret), + + TP_STRUCT__entry( + __field(struct mm_struct *, mm) + __field(int, swapped_in) + __field(int, ret) + ), + + TP_fast_assign( + __entry->mm = mm; + __entry->swapped_in = swapped_in; + __entry->ret = ret; + ), + + TP_printk("mm=%p, swapped_in=%d, ret=%d", + __entry->mm, + __entry->swapped_in, + __entry->ret) +); + #endif /* __HUGE_MEMORY_H */ #include diff --git a/mm/huge_memory.c b/mm/huge_memory.c index ed47448..b113515 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2373,6 +2373,44 @@ static bool hugepage_vma_check(struct vm_area_struct *vma) return !(vma->vm_flags & VM_NO_THP); } +/* + * Bring missing pages in from swap, to complete THP collapse. + * Only done if khugepaged_scan_pmd believes it is worthwhile. + * + * Called and returns without pte mapped or spinlocks held, + * but with mmap_sem held to protect against vma changes. + */ + +static void __collapse_huge_page_swapin(struct mm_struct *mm, + struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd) +{ + unsigned long _address; + pte_t *pte, pteval; + int swapped_in = 0, ret = 0; + + pte = pte_offset_map(pmd, address); + for (_address = address; _address < address + HPAGE_PMD_NR*PAGE_SIZE; + pte++, _address += PAGE_SIZE) { + pteval = *pte; + if (!is_swap_pte(pteval)) + continue; + swapped_in++; + ret = do_swap_page(mm, vma, _address, pte, pmd, + FAULT_FLAG_ALLOW_RETRY|FAULT_FLAG_RETRY_NOWAIT, + pteval); + if (ret & VM_FAULT_ERROR) { + trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0); + return; + } + /* pte is unmapped now, we need to map it */ + pte = pte_offset_map(pmd, _address); + } + pte--; + pte_unmap(pte); + trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1); +} + static void collapse_huge_page(struct mm_struct *mm, unsigned long address, struct page **hpage, @@ -2440,6 +2478,8 @@ static void collapse_huge_page(struct mm_struct *mm, goto out; } + __collapse_huge_page_swapin(mm, vma, address, pmd); + anon_vma_lock_write(vma->anon_vma); pte = pte_offset_map(pmd, address); @@ -2516,9 +2556,6 @@ static void collapse_huge_page(struct mm_struct *mm, result = SCAN_SUCCEED; out_up_write: up_write(&mm->mmap_sem); - trace_mm_collapse_huge_page(mm, isolated, result); - return; - out_nolock: trace_mm_collapse_huge_page(mm, isolated, result); return; diff --git a/mm/internal.h b/mm/internal.h index fbfba0c..e153175 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -36,6 +36,10 @@ /* Do not use these with a slab allocator */ #define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK) +extern int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pte_t *page_table, pmd_t *pmd, + unsigned int flags, pte_t orig_pte); + void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma, unsigned long floor, unsigned long ceiling); diff --git a/mm/memory.c b/mm/memory.c index a329149..5e6eadd 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2522,7 +2522,7 @@ EXPORT_SYMBOL(unmap_mapping_range); * We return with the mmap_sem locked or unlocked in the same cases * as does filemap_fault(). */ -static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, +int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pte_t *page_table, pmd_t *pmd, unsigned int flags, pte_t orig_pte) { -- 2.7.4