From d60fcaf00d752c52fdf566d4184e6d04d9d08879 Mon Sep 17 00:00:00 2001 From: Baolin Wang Date: Mon, 14 Oct 2024 18:24:44 +0800 Subject: [PATCH] mm: khugepaged: fix the incorrect statistics when collapsing large file folios Khugepaged already supports collapsing file large folios (including shmem mTHP) by commit 7de856ffd007 ("mm: khugepaged: support shmem mTHP collapse"), and the control parameters in khugepaged: 'khugepaged_max_ptes_swap' and 'khugepaged_max_ptes_none', still compare based on PTE granularity to determine whether a file collapse is needed. However, the statistics for 'present' and 'swap' in hpage_collapse_scan_file() do not take into account the large folios, which may lead to incorrect judgments regarding the khugepaged_max_ptes_swap/none parameters, resulting in unnecessary file collapses. To fix this issue, take into account the large folios' statistics for 'present' and 'swap' variables in the hpage_collapse_scan_file(). Link: https://lkml.kernel.org/r/c76305d96d12d030a1a346b50503d148364246d2.1728901391.git.baolin.wang@linux.alibaba.com Fixes: 7de856ffd007 ("mm: khugepaged: support shmem mTHP collapse") Signed-off-by: Baolin Wang Acked-by: David Hildenbrand Reviewed-by: Barry Song Reviewed-by: Zi Yan Reviewed-by: Yang Shi Cc: Hugh Dickins Cc: Matthew Wilcox Cc: Ryan Roberts Signed-off-by: Andrew Morton --- mm/khugepaged.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index a420eff92011..b538c3d48386 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2252,7 +2252,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, continue; if (xa_is_value(folio)) { - ++swap; + swap += 1 << xas_get_order(&xas); if (cc->is_khugepaged && swap > khugepaged_max_ptes_swap) { result = SCAN_EXCEED_SWAP_PTE; @@ -2299,7 +2299,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, * is just too costly... */ - present++; + present += folio_nr_pages(folio); if (need_resched()) { xas_pause(&xas);