From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752059AbcBYWR4 (ORCPT ); Thu, 25 Feb 2016 17:17:56 -0500 Received: from gum.cmpxchg.org ([85.214.110.215]:60464 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750850AbcBYWRz (ORCPT ); Thu, 25 Feb 2016 17:17:55 -0500 Date: Thu, 25 Feb 2016 17:17:46 -0500 From: Johannes Weiner To: Mel Gorman Cc: Linux-MM , Rik van Riel , Vlastimil Babka , LKML Subject: Re: [PATCH 07/27] mm, vmscan: Have kswapd only scan based on the highest requested zone Message-ID: <20160225221746.GA12258@cmpxchg.org> References: <1456239890-20737-1-git-send-email-mgorman@techsingularity.net> <1456239890-20737-8-git-send-email-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1456239890-20737-8-git-send-email-mgorman@techsingularity.net> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 23, 2016 at 03:04:30PM +0000, Mel Gorman wrote: > kswapd checks all eligible zones to see if they need balancing even if it was > woken for a lower zone. This made sense when we reclaimed on a per-zone basis > because we wanted to shrink zones fairly so avoid age-inversion problems. > Ideally this is completely unnecessary when reclaiming on a per-node basis. > In theory, there may still be anomalies when all requests are for lower > zones and very old pages are preserved in higher zones but this should be > the exceptional case. > > Signed-off-by: Mel Gorman Acked-by: Johannes Weiner As I mentioned in the other subthread, this should probably be fine, although it would be good, generally, to have some sort of statistics on how much of the age-distorting reclaim is happening, and then maybe mention its existence in the changelog of this patch. Just an idea.