linux-kernel - Re: [PATCH] mm/pages_alloc.c: Don't create ZONE

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Message-ID: <7b752e06-f345-cbb2-d05c-57e5fc5d8e5a@arm.com>
Date:   Tue, 15 Feb 2022 10:17:09 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Alistair Popple <apopple@...dia.com>, akpm@...ux-foundation.org
Cc:     jhubbard@...dia.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, ziy@...dia.com
Subject: Re: [PATCH] mm/pages_alloc.c: Don't create ZONE_MOVABLE beyond the
 end of a node

Hi Alistair,

On 2/15/22 8:28 AM, Alistair Popple wrote:
> ZONE_MOVABLE uses the remaining memory in each node. It's starting pfn
> is also aligned to MAX_ORDER_NR_PAGES. It is possible for the remaining
> memory in a node to be less than MAX_ORDER_NR_PAGES, meaning there is
> not enough room for ZONE_MOVABLE on that node.

How plausible is this scenario on normal systems ? Should not the node
always contain MAX_ORDER_NR_PAGES aligned pages ? Also all zones which
get created from that node should also be MAX_ORDER_NR_PAGES aligned ?
I am just curious how a node could end up being like this.

- Anshuman