From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Subject: khugepaged: drain all LRU caches before scanning pages Having a page in LRU add cache offsets page refcount and gives false-negative on PageLRU(). It reduces collapse success rate. Drain all LRU add caches before scanning. It happens relatively rare and should not disturb the system too much. Link: http://lkml.kernel.org/r/20200416160026.16538-4-kirill.shutemov@xxxxxxxxxxxxxxx Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx> Tested-by: Zi Yan <ziy@xxxxxxxxxx> Acked-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: John Hubbard <jhubbard@xxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Ralph Campbell <rcampbell@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/khugepaged.c | 2 ++ 1 file changed, 2 insertions(+) --- a/mm/khugepaged.c~khugepaged-drain-all-lru-caches-before-scanning-pages +++ a/mm/khugepaged.c @@ -2079,6 +2079,8 @@ static void khugepaged_do_scan(void) barrier(); /* write khugepaged_pages_to_scan to local stack */ + lru_add_drain_all(); + while (progress < pages) { if (!khugepaged_prealloc_page(&hpage, &wait)) break; _
