linux-kernel - Re: [patch v2] mm, vmstat: print non-populated zones in zoneinfo

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170317085737.GE26298@dhcp22.suse.cz>
Date:   Fri, 17 Mar 2017 09:57:37 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Johannes Weiner <hannes@...xchg.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch v2] mm, vmstat: print non-populated zones in zoneinfo

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