From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f43.google.com (mail-wm0-f43.google.com [74.125.82.43]) by kanga.kvack.org (Postfix) with ESMTP id F1D126B0254 for ; Thu, 25 Feb 2016 17:17:52 -0500 (EST) Received: by mail-wm0-f43.google.com with SMTP id a4so47069438wme.1 for ; Thu, 25 Feb 2016 14:17:52 -0800 (PST) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id rx6si12225659wjb.4.2016.02.25.14.17.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Feb 2016 14:17:51 -0800 (PST) Date: Thu, 25 Feb 2016 17:17:46 -0500 From: Johannes Weiner 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> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Linux-MM , Rik van Riel , Vlastimil Babka , LKML 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org