diff options
| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2020-06-03 16:00:09 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-03 20:09:46 -0700 |
| commit | ffe945e633b527d5a4577b42cbadec3c7cbcf096 (patch) | |
| tree | ea7bb830b6d625cf4981465639ca3a1fc2269773 /mm/khugepaged.c | |
| parent | e0c13f9761df8f97cf5e81495d12ecbc4075684a (diff) | |
khugepaged: do not stop collapse if less than half PTEs are referenced
__collapse_huge_page_swapin() checks the number of referenced PTE to
decide if the memory range is hot enough to justify swapin.
We have few problems with the approach:
- It is way too late: we can do the check much earlier and safe time.
khugepaged_scan_pmd() already knows if we have any pages to swap in
and number of referenced page.
- It stops collapse altogether if there's not enough referenced pages,
not only swappingin.
Fix it by making the right check early. We also can avoid additional
page table scanning if khugepaged_scan_pmd() haven't found any swap
entries.
Fixes: 0db501f7a34c ("mm, thp: convert from optimistic swapin collapsing to conservative")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Link: http://lkml.kernel.org/r/20200416160026.16538-3-kirill.shutemov@linux.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/khugepaged.c')
| -rw-r--r-- | mm/khugepaged.c | 27 |
1 files changed, 11 insertions, 16 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index cd280afb246e..c436fd390296 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -899,11 +899,6 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, .pgoff = linear_page_index(vma, address), }; - /* 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; - } vmf.pte = pte_offset_map(pmd, address); for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; vmf.pte++, vmf.address += PAGE_SIZE) { @@ -943,7 +938,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, static void collapse_huge_page(struct mm_struct *mm, unsigned long address, struct page **hpage, - int node, int referenced) + int node, int referenced, int unmapped) { pmd_t *pmd, _pmd; pte_t *pte; @@ -1000,7 +995,8 @@ 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, referenced)) { + if (unmapped && !__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; @@ -1233,22 +1229,21 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, mmu_notifier_test_young(vma->vm_mm, address)) referenced++; } - if (writable) { - if (referenced) { - result = SCAN_SUCCEED; - ret = 1; - } else { - result = SCAN_LACK_REFERENCED_PAGE; - } - } else { + if (!writable) { result = SCAN_PAGE_RO; + } else if (!referenced || (unmapped && referenced < HPAGE_PMD_NR/2)) { + result = SCAN_LACK_REFERENCED_PAGE; + } else { + result = SCAN_SUCCEED; + ret = 1; } out_unmap: pte_unmap_unlock(pte, ptl); if (ret) { node = khugepaged_find_target_node(); /* collapse_huge_page will return with the mmap_sem released */ - collapse_huge_page(mm, address, hpage, node, referenced); + collapse_huge_page(mm, address, hpage, node, + referenced, unmapped); } out: trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, |