From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752218AbaBMP6I (ORCPT ); Thu, 13 Feb 2014 10:58:08 -0500 Received: from mail-ie0-f176.google.com ([209.85.223.176]:62771 "EHLO mail-ie0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751738AbaBMP6G (ORCPT ); Thu, 13 Feb 2014 10:58:06 -0500 MIME-Version: 1.0 In-Reply-To: <20140213104231.GX6732@suse.de> References: <20140213104231.GX6732@suse.de> Date: Thu, 13 Feb 2014 23:58:05 +0800 Message-ID: Subject: Re: [PATCH] mm: swap: Use swapfiles in priority order From: Weijie Yang To: Mel Gorman Cc: Andrew Morton , Hugh Dickins , Michal Hocko , Linux-MM , LKML Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 13, 2014 at 6:42 PM, Mel Gorman wrote: > 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) { Does it lead to a "schlemiel the painter's algorithm"? (please forgive my rude words, but I can't find a precise word to describe it because English is not my native language. My apologize.) How about modify it like this? diff --git a/mm/swapfile.c b/mm/swapfile.c index 4a7f7e6..d64aa55 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -676,7 +676,7 @@ swp_entry_t get_swap_page(void) next = si->next; if (next < 0 || (!wrapped && si->prio != swap_info[next]->prio)) { - next = swap_list.head; + next = type; wrapped++; } > hp_index = atomic_xchg(&highest_priority_index, -1); > /* > * highest_priority_index records current highest priority swap > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/