linux-kernel - Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions

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Date:   Fri, 30 Jun 2017 13:01:18 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Wei Yang <richard.weiyang@...il.com>
Cc:     Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        Xishi Qiu <qiuxishi@...wei.com>,
        Kani Toshimitsu <toshi.kani@....com>, slaoub@...il.com,
        Joonsoo Kim <js1304@...il.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions

On Fri 30-06-17 11:55:45, Michal Hocko wrote:
> On Fri 30-06-17 17:39:56, Wei Yang wrote:
> > On Fri, Jun 30, 2017 at 4:39 PM, Michal Hocko <mhocko@...nel.org> wrote:
> [...]
> > > yes and to be honest I do not plan to fix it unless somebody has a real
> > > life usecase for it. Now that we allow explicit onlininig type anywhere
> > > it seems like a reasonable behavior and this will allow us to remove
> > > quite some code which is always a good deal wrt longterm maintenance.
> > >
> > 
> > hmm... the statistics displayed in /proc/zoneinfo would be meaningless
> > for zone_normal and zone_movable.
> 
> Why would they be meaningless? Counters will always reflect the actual
> use - if not then it is a bug. And wrt to zone description what is
> meaningless about
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Movable
> memory37/valid_zones:Movable Normal
> memory38/valid_zones:Movable Normal
> memory39/valid_zones:Movable Normal
> memory40/valid_zones:Normal
> memory41/valid_zones:Movable
> 
> And
> Node 1, zone   Normal
>   pages free     65465
>         min      156
>         low      221
>         high     286
>         spanned  229376
>         present  65536
>         managed  65536
> [...]
>   start_pfn:           1114112
> Node 1, zone  Movable
>   pages free     65443
>         min      156
>         low      221
>         high     286
>         spanned  196608
>         present  65536
>         managed  65536
> [...]
>   start_pfn:           1179648
> 
> ranges are clearly defined as [start_pfn, start_pfn+managed] and managed

errr, this should be [start_pfn, start_pfn + spanned] of course.

> matches the number of onlined pages (256MB).

-- 
Michal Hocko
SUSE Labs