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

From: Michal Hocko <mhocko@kernel.org>
To: Wei Yang <richard.weiyang@gmail.com>
Cc: Linux-MM <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Reza Arbab <arbab@linux.vnet.ibm.com>,
	Yasuaki Ishimatsu <yasu.isimatu@gmail.com>,
	Xishi Qiu <qiuxishi@huawei.com>,
	Kani Toshimitsu <toshi.kani@hpe.com>,
	slaoub@gmail.com, Joonsoo Kim <js1304@gmail.com>,
	Daniel Kiper <daniel.kiper@oracle.com>,
	Igor Mammedov <imammedo@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions
Date: Fri, 30 Jun 2017 13:01:18 +0200	[thread overview]
Message-ID: <20170630110118.GG22917@dhcp22.suse.cz> (raw)
In-Reply-To: <20170630095545.GF22917@dhcp22.suse.cz>

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@kernel.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

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