From 9a9b6cce630d14851ab09534b6462258486048cd Mon Sep 17 00:00:00 2001 From: Yang Shi Date: Wed, 1 Apr 2020 21:06:23 -0700 Subject: [PATCH] mm: swap: use smp_mb__after_atomic() to order LRU bit set Memory barrier is needed after setting LRU bit, but smp_mb() is too strong. Some architectures, i.e. x86, imply memory barrier with atomic operations, so replacing it with smp_mb__after_atomic() sounds better, which is nop on strong ordered machines, and full memory barriers on others. With this change the vm-scalability cases would perform better on x86, I saw total 6% improvement with this patch and previous inline fix. The test data (lru-file-readtwice throughput) against v5.6-rc4: mainline w/ inline fix w/ both (adding this) 150MB 154MB 159MB Fixes: 9c4e6b1a7027 ("mm, mlock, vmscan: no more skipping pagevecs") Signed-off-by: Yang Shi Signed-off-by: Andrew Morton Tested-by: Shakeel Butt Reviewed-by: Shakeel Butt Acked-by: Vlastimil Babka Acked-by: Johannes Weiner Cc: Matthew Wilcox (Oracle) Link: http://lkml.kernel.org/r/1584500541-46817-2-git-send-email-yang.shi@linux.alibaba.com Signed-off-by: Linus Torvalds --- mm/swap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/swap.c b/mm/swap.c index f502a2155e85..a4af8c999963 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -931,7 +931,6 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec, VM_BUG_ON_PAGE(PageLRU(page), page); - SetPageLRU(page); /* * Page becomes evictable in two ways: * 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()]. @@ -958,7 +957,8 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec, * looking at the same page) and the evictable page will be stranded * in an unevictable LRU. */ - smp_mb(); + SetPageLRU(page); + smp_mb__after_atomic(); if (page_evictable(page)) { lru = page_lru(page);