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

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Date:   Sat, 4 Mar 2017 13:51:41 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     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 03/04/2017 04:23 AM, 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.
> 
> Signed-off-by: David Rientjes <rientjes@...gle.com>

Reviewed-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>