Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757547Ab3HGOQC (ORCPT ); Wed, 7 Aug 2013 10:16:02 -0400 Received: from cantor2.suse.de ([195.135.220.15]:33091 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755663Ab3HGOQA (ORCPT ); Wed, 7 Aug 2013 10:16:00 -0400 Date: Wed, 7 Aug 2013 15:15:55 +0100 From: Mel Gorman To: Johannes Weiner Cc: Andrew Morton , Rik van Riel , Andrea Arcangeli , Zlatko Calusic , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch v2 1/3] mm: vmscan: fix numa reclaim balance problem in kswapd Message-ID: <20130807141555.GO2296@suse.de> References: <1375457846-21521-1-git-send-email-hannes@cmpxchg.org> <1375457846-21521-2-git-send-email-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1375457846-21521-2-git-send-email-hannes@cmpxchg.org> 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 Content-Length: 1442 Lines: 35 On Fri, Aug 02, 2013 at 11:37:24AM -0400, Johannes Weiner wrote: > When the page allocator fails to get a page from all zones in its > given zonelist, it wakes up the per-node kswapds for all zones that > are at their low watermark. > > However, with a system under load the free pages in a zone can > fluctuate enough that the allocation fails but the kswapd wakeup is > also skipped while the zone is still really close to the low > watermark. > > When one node misses a wakeup like this, it won't be aged before all > the other node's zones are down to their low watermarks again. And > skipping a full aging cycle is an obvious fairness problem. > > Kswapd runs until the high watermarks are restored, so it should also > be woken when the high watermarks are not met. This ages nodes more > equally and creates a safety margin for the page counter fluctuation. > > By using zone_balanced(), it will now check, in addition to the > watermark, if compaction requires more order-0 pages to create a > higher order page. > > Signed-off-by: Johannes Weiner > Reviewed-by: Rik van Riel Acked-by: Mel Gorman -- Mel Gorman SUSE Labs -- 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/