From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752400AbdARR3r (ORCPT ); Wed, 18 Jan 2017 12:29:47 -0500 Received: from gum.cmpxchg.org ([85.214.110.215]:38616 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751852AbdARR3p (ORCPT ); Wed, 18 Jan 2017 12:29:45 -0500 Date: Wed, 18 Jan 2017 11:46:47 -0500 From: Johannes Weiner To: Michal Hocko Cc: Andrew Morton , Mel Gorman , Minchan Kim , Hillf Danton , linux-mm@kvack.org, LKML , Michal Hocko Subject: Re: [PATCH 2/3] mm, vmscan: consider eligible zones in get_scan_count Message-ID: <20170118164647.GB32495@cmpxchg.org> References: <20170117103702.28542-1-mhocko@kernel.org> <20170117103702.28542-3-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170117103702.28542-3-mhocko@kernel.org> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 17, 2017 at 11:37:01AM +0100, Michal Hocko wrote: > From: Michal Hocko > > get_scan_count considers the whole node LRU size when > - doing SCAN_FILE due to many page cache inactive pages > - calculating the number of pages to scan > > in both cases this might lead to unexpected behavior especially on 32b > systems where we can expect lowmem memory pressure very often. > > A large highmem zone can easily distort SCAN_FILE heuristic because > there might be only few file pages from the eligible zones on the node > lru and we would still enforce file lru scanning which can lead to > trashing while we could still scan anonymous pages. > > The later use of lruvec_lru_size can be problematic as well. Especially > when there are not many pages from the eligible zones. We would have to > skip over many pages to find anything to reclaim but shrink_node_memcg > would only reduce the remaining number to scan by SWAP_CLUSTER_MAX > at maximum. Therefore we can end up going over a large LRU many times > without actually having chance to reclaim much if anything at all. The > closer we are out of memory on lowmem zone the worse the problem will > be. > > Fix this by filtering out all the ineligible zones when calculating the > lru size for both paths and consider only sc->reclaim_idx zones. > > Acked-by: Minchan Kim > Acked-by: Hillf Danton > Signed-off-by: Michal Hocko Acked-by: Johannes Weiner