From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754022AbaBMKmg (ORCPT ); Thu, 13 Feb 2014 05:42:36 -0500 Received: from cantor2.suse.de ([195.135.220.15]:33556 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751970AbaBMKmf (ORCPT ); Thu, 13 Feb 2014 05:42:35 -0500 Date: Thu, 13 Feb 2014 10:42:31 +0000 From: Mel Gorman To: Andrew Morton Cc: Hugh Dickins , Michal Hocko , Linux-MM , LKML Subject: [PATCH] mm: swap: Use swapfiles in priority order Message-ID: <20140213104231.GX6732@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org According to the swapon documentation Swap pages are allocated from areas in priority order, highest priority first. For areas with different priorities, a higher-priority area is exhausted before using a lower-priority area. A user reported that the reality is different. When multiple swap files are enabled and a memory consumer started, the swap files are consumed in pairs after the highest priority file is exhausted. Early in the lifetime of the test, swapfile consumptions looks like Filename Type Size Used Priority /testswap1 file 100004 100004 8 /testswap2 file 100004 23764 7 /testswap3 file 100004 23764 6 /testswap4 file 100004 0 5 /testswap5 file 100004 0 4 /testswap6 file 100004 0 3 /testswap7 file 100004 0 2 /testswap8 file 100004 0 1 This patch fixes the swap_list search in get_swap_page to use the swap files in the correct order. When applied the swap file consumptions looks like Filename Type Size Used Priority /testswap1 file 100004 100004 8 /testswap2 file 100004 100004 7 /testswap3 file 100004 29372 6 /testswap4 file 100004 0 5 /testswap5 file 100004 0 4 /testswap6 file 100004 0 3 /testswap7 file 100004 0 2 /testswap8 file 100004 0 1 Signed-off-by: Mel Gorman --- mm/swapfile.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 4a7f7e6..6d0ac2b 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -651,7 +651,7 @@ swp_entry_t get_swap_page(void) goto noswap; atomic_long_dec(&nr_swap_pages); - for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) { + for (type = swap_list.head; type >= 0 && wrapped < 2; type = next) { hp_index = atomic_xchg(&highest_priority_index, -1); /* * highest_priority_index records current highest priority swap