linux-kernel - Re: [PATCH 2/6] mm: page_alloc: fix up block types when merging compatible blocks

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Message-ID: <FFA8C33F-D613-46CC-AD81-4789AFE4A087@nvidia.com>
Date:   Mon, 11 Sep 2023 16:01:23 -0400
From:   Zi Yan <ziy@...dia.com>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] mm: page_alloc: fix up block types when merging
 compatible blocks

On 11 Sep 2023, at 15:41, Johannes Weiner wrote:

> The buddy allocator coalesces compatible blocks during freeing, but it
> doesn't update the types of the subblocks to match. When an allocation
> later breaks the chunk down again, its pieces will be put on freelists
> of the wrong type. This encourages incompatible page mixing (ask for
> one type, get another), and thus long-term fragmentation.
>
> Update the subblocks when merging a larger chunk, such that a later
> expand() will maintain freelist type hygiene.
>
> v2:
> - remove spurious change_pageblock_range() move (Zi Yan)
>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> ---
>  mm/page_alloc.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>

LGTM. Reviewed-by: Zi Yan <ziy@...dia.com>

--
Best Regards,
Yan, Zi

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