From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1033495AbeBOOp3 (ORCPT ); Thu, 15 Feb 2018 09:45:29 -0500 Received: from mx2.suse.de ([195.135.220.15]:48042 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1033423AbeBOOp1 (ORCPT ); Thu, 15 Feb 2018 09:45:27 -0500 Date: Thu, 15 Feb 2018 15:45:25 +0100 From: Michal Hocko To: David Rientjes Cc: Andrew Morton , Jonathan Corbet , Vlastimil Babka , Mel Gorman , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Subject: Re: [patch 1/2] mm, page_alloc: extend kernelcore and movablecore for percent Message-ID: <20180215144525.GG7275@dhcp22.suse.cz> References: <20180214095911.GB28460@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.3 (2018-01-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 14-02-18 02:28:38, David Rientjes wrote: > On Wed, 14 Feb 2018, Michal Hocko wrote: > > > I do not have any objections regarding the extension. What I am more > > interested in is _why_ people are still using this command line > > parameter at all these days. Why would anybody want to introduce lowmem > > issues from 32b days. I can see the CMA/Hotplug usecases for > > ZONE_MOVABLE but those have their own ways to define zone movable. I was > > tempted to simply remove the kernelcore already. Could you be more > > specific what is your usecase which triggered a need of an easier > > scaling of the size? > > Fragmentation of non-__GFP_MOVABLE pages due to low on memory situations > can pollute most pageblocks on the system, as much as 1GB of slab being > fragmented over 128GB of memory, for example. OK, I was assuming something like that. > When the amount of kernel > memory is well bounded for certain systems, it is better to aggressively > reclaim from existing MIGRATE_UNMOVABLE pageblocks rather than eagerly > fallback to others. > > We have additional patches that help with this fragmentation if you're > interested, specifically kcompactd compaction of MIGRATE_UNMOVABLE > pageblocks triggered by fallback of non-__GFP_MOVABLE allocations and > draining of pcp lists back to the zone free area to prevent stranding. Yes, I think we need a proper fix. (Ab)using zone_movable for this usecase is just sad. -- Michal Hocko SUSE Labs