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

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Message-ID: <20230317200849.gjqezmeaiqkfz7so@box.shutemov.name>
Date:   Fri, 17 Mar 2023 23:08:49 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     David Hildenbrand <david@...hat.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        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 Fri, Mar 17, 2023 at 06:50:17PM +0100, David Hildenbrand wrote:
> 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?

I got the sentence backwards. It suppose to be

	For cases when MAX_ORDER is larger than pageblock, set migrate type to
	MIGRATE_MOVABLE for all pageblocks covered by the page.


-- 
  Kiryl Shutsemau / Kirill A. Shutemov