From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754811AbaEAIpV (ORCPT ); Thu, 1 May 2014 04:45:21 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57756 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754613AbaEAIpG (ORCPT ); Thu, 1 May 2014 04:45:06 -0400 From: Mel Gorman To: Linux-MM , Linux-FSDevel Cc: Johannes Weiner , Vlastimil Babka , Jan Kara , Michal Hocko , Hugh Dickins , Mel Gorman , Linux Kernel Subject: [PATCH 15/17] mm: Do not use unnecessary atomic operations when adding pages to the LRU Date: Thu, 1 May 2014 09:44:46 +0100 Message-Id: <1398933888-4940-16-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.8.4.5 In-Reply-To: <1398933888-4940-1-git-send-email-mgorman@suse.de> References: <1398933888-4940-1-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When adding pages to the LRU we clear the active bit unconditionally. As the page could be reachable from other paths we cannot use unlocked operations without risk of corruption such as a parallel mark_page_accessed. This patch test if is necessary to clear the atomic flag before using an atomic operation. In the unlikely even this races with mark_page_accesssed the consequences are simply that the page may be promoted to the active list that might have been left on the inactive list before the patch. This is a marginal consequence. Signed-off-by: Mel Gorman --- include/linux/swap.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index da8a250..395dcab 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -329,13 +329,15 @@ extern void add_page_to_unevictable_list(struct page *page); */ static inline void lru_cache_add_anon(struct page *page) { - ClearPageActive(page); + if (PageActive(page)) + ClearPageActive(page); __lru_cache_add(page); } static inline void lru_cache_add_file(struct page *page) { - ClearPageActive(page); + if (PageActive(page)) + ClearPageActive(page); __lru_cache_add(page); } -- 1.8.4.5