linux-kernel - Re: [PATCH] mm/page_alloc: Make deferred page init free pages in MAX

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Message-ID: <373b22c7-9162-eff0-1f0c-0a8d79a8b372@redhat.com>
Date:   Fri, 17 Mar 2023 18:50:17 +0100
From:   David Hildenbrand <david@...hat.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>
Cc:     linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/page_alloc: Make deferred page init free pages in
 MAX_ORDER blocks

On 17.03.23 16:35, Kirill A. Shutemov wrote:
> Normal page init path frees pages during the boot in MAX_ORDER chunks,
> but deferred page init path does it in pageblock blocks.
> 
> Change deferred page init path to work in MAX_ORDER blocks.
> 
> For cases when pageblock is larger than MAX_ORDER, set migrate type to
> MIGRATE_MOVABLE for all pageblocks covered by the page.

See

commit b3d40a2b6d10c9d0424d2b398bf962fb6adad87e
Author: David Hildenbrand <david@...hat.com>
Date:   Tue Mar 22 14:43:20 2022 -0700

     mm: enforce pageblock_order < MAX_ORDER
     
     Some places in the kernel don't really expect pageblock_order >=
     MAX_ORDER, and it looks like this is only possible in corner cases:
     
     1) CONFIG_DEFERRED_STRUCT_PAGE_INIT we'll end up freeing pageblock_order
        pages via __free_pages_core(), which cannot possibly work.

     ...

How should it still happen?

-- 
Thanks,

David / dhildenb