linux-kernel - Re: [PATCH -v2 0/9] mm: make movable onlining suck less

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Message-ID: <20170411104710.GF6729@dhcp22.suse.cz>
Date:   Tue, 11 Apr 2017 12:47:10 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Igor Mammedov <imammedo@...hat.com>
Cc:     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>,
        Jerome Glisse <jglisse@...hat.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
        slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...il.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Lai Jiangshan <laijs@...fujitsu.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Tobias Regnery <tobias.regnery@...il.com>
Subject: Re: [PATCH -v2 0/9] mm: make movable onlining suck less

On Tue 11-04-17 11:53:22, Igor Mammedov wrote:
> On Tue, 11 Apr 2017 10:41:42 +0200
> Michal Hocko <mhocko@...nel.org> wrote:
> 
> > On Tue 11-04-17 10:01:52, Igor Mammedov wrote:
> > > On Mon, 10 Apr 2017 16:56:39 +0200
> > > Michal Hocko <mhocko@...nel.org> wrote:  
> > [...]
> > > > > #echo online_kernel > memory32/state
> > > > > write error: Invalid argument
> > > > > // that's not what's expected    
> > > > 
> > > > this is proper behavior with the current implementation. Does anything
> > > > depend on the zone reusing?  
> > > if we didn't have zone imbalance issue in design,
> > > the it wouldn't matter but as it stands it's not
> > > minore issue.
> > > 
> > > Consider following,
> > > one hotplugs some memory and onlines it as movable,
> > > then one needs to hotplug some more but to do so 
> > > one one needs more memory from zone NORMAL and to keep
> > > zone balance some memory in MOVABLE should be reonlined
> > > as NORMAL  
> > 
> > Is this something that we absolutely have to have right _now_? Or are you
> > OK if I address this in follow up series? Because it will make the
> > current code slightly more complex and to be honest I would rather like
> > to see this "core" merge and build more on top.
>
> It's fine by me to do it on top.

OK, I will document this in the changelog of the patch 6.

"
Please note that this patch also changes the original behavior when
offlining a memory block adjacent to another zone (Normal vs. Movable)
used to allow to change its movable type. This will be handled later.
"
-- 
Michal Hocko
SUSE Labs