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Date:   Wed, 18 Jul 2018 17:10:09 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     David Rientjes <rientjes@google.com>
Cc:     Baoquan He <bhe@redhat.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, akpm@linux-foundation.org, corbet@lwn.net,
        linux-doc@vger.kernel.org
Subject: Re: [PATCH] mm/page_alloc: Deprecate kernelcore=nn and movable_core=
Message-ID: <20180718151009.GJ7193@dhcp22.suse.cz>
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On Tue 17-07-18 13:46:43, David Rientjes wrote:
> On Tue, 17 Jul 2018, Baoquan He wrote:
> 
> > We can still use 'kernelcore=mirror' or 'movable_node' for the usage
> > of hotplug and movable zone. If somebody shows up with a valid usecase
> > we can reconsider.
> > 
> 
> We actively use kernelcore=n%, I had recently added support for the option 
> in the first place in 4.17.  It's certainly not deprecated.
> 
> commit a5c6d6509342785bef53bf9508e1842b303f1878
> Author: David Rientjes <rientjes@google.com>
> Date:   Thu Apr 5 16:23:09 2018 -0700
> 
>     mm, page_alloc: extend kernelcore and movablecore for percent

What kind of functionality do you need to not depend on this knob?
I mean it is a gross hack and you are basically working around
fragmentation issues. ZONE_MOVABLE doesn't seem to be a long term
solution here IMHO.
-- 
Michal Hocko
SUSE Labs