linux-kernel - Re: [PATCH v2 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section

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Message-ID: <20181217133516.GO30879@dhcp22.suse.cz>
Date:   Mon, 17 Dec 2018 14:35:16 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Mikhail Zaslonko <zaslonko@...ux.ibm.com>,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Pavel.Tatashin@...rosoft.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com
Subject: Re: [PATCH v2 1/1] mm, memory_hotplug: Initialize struct pages for
 the full memory section

On Mon 17-12-18 14:29:04, David Hildenbrand wrote:
> On 17.12.18 13:28, Michal Hocko wrote:
> > On Mon 17-12-18 10:38:32, David Hildenbrand wrote:
> > [...]
> >> I am wondering if we should fix this on the memblock level instead than.
> >> Something like, before handing memory over to the page allocator, add
> >> memory as reserved up to the last section boundary. Or even when setting
> >> the physical memory limit (mem= scenario).
> > 
> > Memory initialization is spread over several places and that makes it
> > really hard to grasp and maintain. I do not really see why we should
> > make memblock even more special. We do intialize the section worth of
> > memory here so it sounds like a proper place to quirk for incomplete
> > sections.
> > 
> 
> True as well. The reason I am asking is, that memblock usually takes
> care of physical memory holes.

Yes and no. It only reflects existing memory ranges (so yes it skips
over holes) and then it provides an API that platform/arch code can
abuse to cut holes into existing ranges.
-- 
Michal Hocko
SUSE Labs