From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 058/155] mm: swap: use smp_mb__after_atomic() to order LRU bit set Date: Wed, 01 Apr 2020 21:06:23 -0700 Message-ID: <20200402040623.1OTEIbdDl%akpm@linux-foundation.org> References: <20200401210155.09e3b9742e1c6e732f5a7250@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:56090 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725789AbgDBEGZ (ORCPT ); Thu, 2 Apr 2020 00:06:25 -0400 In-Reply-To: <20200401210155.09e3b9742e1c6e732f5a7250@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, hannes@cmpxchg.org, linux-mm@kvack.org, mm-commits@vger.kernel.org, shakeelb@google.com, torvalds@linux-foundation.org, vbabka@suse.cz, willy@infradead.org, yang.shi@linux.alibaba.com From: Yang Shi Subject: 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 Link: http://lkml.kernel.org/r/1584500541-46817-2-git-send-email-yang.shi@linux.alibaba.com Fixes: 9c4e6b1a7027 ("mm, mlock, vmscan: no more skipping pagevecs") Signed-off-by: Yang Shi Acked-by: Vlastimil Babka Reviewed-by: Shakeel Butt Tested-by: Shakeel Butt Acked-by: Johannes Weiner Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- mm/swap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/swap.c~mm-swap-use-smp_mb__after_atomic-to-order-lru-bit-set +++ a/mm/swap.c @@ -931,7 +931,6 @@ static void __pagevec_lru_add_fn(struct 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 * 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); _