From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751043AbdCQI6L (ORCPT ); Fri, 17 Mar 2017 04:58:11 -0400 Received: from mx2.suse.de ([195.135.220.15]:51259 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750898AbdCQI6K (ORCPT ); Fri, 17 Mar 2017 04:58:10 -0400 Date: Fri, 17 Mar 2017 09:57:37 +0100 From: Michal Hocko To: David Rientjes Cc: Andrew Morton , Anshuman Khandual , Vlastimil Babka , Mel Gorman , Johannes Weiner , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [patch v2] mm, vmstat: print non-populated zones in zoneinfo Message-ID: <20170317085737.GE26298@dhcp22.suse.cz> References: <4acf16c5-c64b-b4f8-9a41-1926eed23fe1@linux.vnet.ibm.com> <20170308144159.GD11034@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170308144159.GD11034@dhcp22.suse.cz> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 08-03-17 15:41:59, Michal Hocko wrote: > On Fri 03-03-17 14:53:07, David Rientjes wrote: > > Initscripts can use the information (protection levels) from > > /proc/zoneinfo to configure vm.lowmem_reserve_ratio at boot. > > > > vm.lowmem_reserve_ratio is an array of ratios for each configured zone on > > the system. If a zone is not populated on an arch, /proc/zoneinfo > > suppresses its output. > > > > This results in there not being a 1:1 mapping between the set of zones > > emitted by /proc/zoneinfo and the zones configured by > > vm.lowmem_reserve_ratio. > > > > This patch shows statistics for non-populated zones in /proc/zoneinfo. > > The zones exist and hold a spot in the vm.lowmem_reserve_ratio array. > > Without this patch, it is not possible to determine which index in the > > array controls which zone if one or more zones on the system are not > > populated. > > > > Remaining users of walk_zones_in_node() are unchanged. Files such as > > /proc/pagetypeinfo require certain zone data to be initialized properly > > for display, which is not done for unpopulated zones. > > Does it really make sense to print any counters of that zone though? > Your follow up patch just suggests that we don't want some but what > about others? > > I can see how skipping empty zones completely can be clumsy but wouldn't > it be sufficient to just provide > > Node $NUM, zone $NAME > (unpopulated) > > instead? ping -- Michal Hocko SUSE Labs