From 0db501f7a34c11d3b964205e5b6d00692a648035 Mon Sep 17 00:00:00 2001 From: Ebru Akagunduz Date: Tue, 26 Jul 2016 15:26:46 -0700 Subject: [PATCH] mm, thp: convert from optimistic swapin collapsing to conservative To detect whether khugepaged swapin is worthwhile, this patch checks the amount of young pages. There should be at least half of HPAGE_PMD_NR to swapin. Link: http://lkml.kernel.org/r/1468109451-1615-1-git-send-email-ebru.akagunduz@gmail.com Signed-off-by: Ebru Akagunduz Suggested-by: Minchan Kim Acked-by: Rik van Riel Cc: Hugh Dickins Cc: Kirill A. Shutemov Cc: Naoya Horiguchi Cc: Andrea Arcangeli Cc: Joonsoo Kim Cc: Cyrill Gorcunov Cc: Mel Gorman Cc: David Rientjes Cc: Vlastimil Babka Cc: Aneesh Kumar K.V Cc: Johannes Weiner Cc: Michal Hocko Cc: Boaz Harrosh Cc: Hillf Danton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/trace/events/huge_memory.h | 19 ++++++++------- mm/khugepaged.c | 38 ++++++++++++++++++------------ 2 files changed, 34 insertions(+), 23 deletions(-) diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h index 830d47d5ca41..04f58acda8e8 100644 --- a/include/trace/events/huge_memory.h +++ b/include/trace/events/huge_memory.h @@ -13,7 +13,7 @@ EM( SCAN_EXCEED_NONE_PTE, "exceed_none_pte") \ EM( SCAN_PTE_NON_PRESENT, "pte_non_present") \ EM( SCAN_PAGE_RO, "no_writable_page") \ - EM( SCAN_NO_REFERENCED_PAGE, "no_referenced_page") \ + EM( SCAN_LACK_REFERENCED_PAGE, "lack_referenced_page") \ EM( SCAN_PAGE_NULL, "page_null") \ EM( SCAN_SCAN_ABORT, "scan_aborted") \ EM( SCAN_PAGE_COUNT, "not_suitable_page_count") \ @@ -47,7 +47,7 @@ SCAN_STATUS TRACE_EVENT(mm_khugepaged_scan_pmd, TP_PROTO(struct mm_struct *mm, struct page *page, bool writable, - bool referenced, int none_or_zero, int status, int unmapped), + int referenced, int none_or_zero, int status, int unmapped), TP_ARGS(mm, page, writable, referenced, none_or_zero, status, unmapped), @@ -55,7 +55,7 @@ TRACE_EVENT(mm_khugepaged_scan_pmd, __field(struct mm_struct *, mm) __field(unsigned long, pfn) __field(bool, writable) - __field(bool, referenced) + __field(int, referenced) __field(int, none_or_zero) __field(int, status) __field(int, unmapped) @@ -108,14 +108,14 @@ TRACE_EVENT(mm_collapse_huge_page, TRACE_EVENT(mm_collapse_huge_page_isolate, TP_PROTO(struct page *page, int none_or_zero, - bool referenced, bool writable, int status), + int referenced, bool writable, int status), TP_ARGS(page, none_or_zero, referenced, writable, status), TP_STRUCT__entry( __field(unsigned long, pfn) __field(int, none_or_zero) - __field(bool, referenced) + __field(int, referenced) __field(bool, writable) __field(int, status) ), @@ -138,25 +138,28 @@ TRACE_EVENT(mm_collapse_huge_page_isolate, TRACE_EVENT(mm_collapse_huge_page_swapin, - TP_PROTO(struct mm_struct *mm, int swapped_in, int ret), + TP_PROTO(struct mm_struct *mm, int swapped_in, int referenced, int ret), - TP_ARGS(mm, swapped_in, ret), + TP_ARGS(mm, swapped_in, referenced, ret), TP_STRUCT__entry( __field(struct mm_struct *, mm) __field(int, swapped_in) + __field(int, referenced) __field(int, ret) ), TP_fast_assign( __entry->mm = mm; __entry->swapped_in = swapped_in; + __entry->referenced = referenced; __entry->ret = ret; ), - TP_printk("mm=%p, swapped_in=%d, ret=%d", + TP_printk("mm=%p, swapped_in=%d, referenced=%d, ret=%d", __entry->mm, __entry->swapped_in, + __entry->referenced, __entry->ret) ); diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 566148489e33..7dbee698d6aa 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -27,7 +27,7 @@ enum scan_result { SCAN_EXCEED_NONE_PTE, SCAN_PTE_NON_PRESENT, SCAN_PAGE_RO, - SCAN_NO_REFERENCED_PAGE, + SCAN_LACK_REFERENCED_PAGE, SCAN_PAGE_NULL, SCAN_SCAN_ABORT, SCAN_PAGE_COUNT, @@ -500,8 +500,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, { struct page *page = NULL; pte_t *_pte; - int none_or_zero = 0, result = 0; - bool referenced = false, writable = false; + int none_or_zero = 0, result = 0, referenced = 0; + bool writable = false; for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++, address += PAGE_SIZE) { @@ -580,11 +580,11 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(PageLRU(page), page); - /* If there is no mapped pte young don't collapse the page */ + /* There should be enough young pte to collapse the page */ if (pte_young(pteval) || page_is_young(page) || PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm, address)) - referenced = true; + referenced++; } if (likely(writable)) { if (likely(referenced)) { @@ -869,7 +869,8 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address) static bool __collapse_huge_page_swapin(struct mm_struct *mm, struct vm_area_struct *vma, - unsigned long address, pmd_t *pmd) + unsigned long address, pmd_t *pmd, + int referenced) { pte_t pteval; int swapped_in = 0, ret = 0; @@ -887,12 +888,19 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, if (!is_swap_pte(pteval)) continue; swapped_in++; + /* we only decide to swapin, if there is enough young ptes */ + if (referenced < HPAGE_PMD_NR/2) { + trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); + return false; + } ret = do_swap_page(&fe, pteval); + /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ if (ret & VM_FAULT_RETRY) { down_read(&mm->mmap_sem); if (hugepage_vma_revalidate(mm, address)) { /* vma is no longer available, don't continue to swapin */ + trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); return false; } /* check if the pmd is still valid */ @@ -900,7 +908,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, return false; } if (ret & VM_FAULT_ERROR) { - trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0); + trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); return false; } /* pte is unmapped now, we need to map it */ @@ -908,7 +916,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, } fe.pte--; pte_unmap(fe.pte); - trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1); + trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); return true; } @@ -916,7 +924,7 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address, struct page **hpage, struct vm_area_struct *vma, - int node) + int node, int referenced) { pmd_t *pmd, _pmd; pte_t *pte; @@ -973,7 +981,7 @@ static void collapse_huge_page(struct mm_struct *mm, * If it fails, we release mmap_sem and jump out_nolock. * Continuing to collapse causes inconsistency. */ - if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) { + if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) { mem_cgroup_cancel_charge(new_page, memcg, true); up_read(&mm->mmap_sem); goto out_nolock; @@ -1084,12 +1092,12 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, { pmd_t *pmd; pte_t *pte, *_pte; - int ret = 0, none_or_zero = 0, result = 0; + int ret = 0, none_or_zero = 0, result = 0, referenced = 0; struct page *page = NULL; unsigned long _address; spinlock_t *ptl; int node = NUMA_NO_NODE, unmapped = 0; - bool writable = false, referenced = false; + bool writable = false; VM_BUG_ON(address & ~HPAGE_PMD_MASK); @@ -1177,14 +1185,14 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, if (pte_young(pteval) || page_is_young(page) || PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm, address)) - referenced = true; + referenced++; } if (writable) { if (referenced) { result = SCAN_SUCCEED; ret = 1; } else { - result = SCAN_NO_REFERENCED_PAGE; + result = SCAN_LACK_REFERENCED_PAGE; } } else { result = SCAN_PAGE_RO; @@ -1194,7 +1202,7 @@ out_unmap: if (ret) { node = khugepaged_find_target_node(); /* collapse_huge_page will return with the mmap_sem released */ - collapse_huge_page(mm, address, hpage, vma, node); + collapse_huge_page(mm, address, hpage, vma, node, referenced); } out: trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,