linux-kernel - Re: [PATCH 4/6] mm: page_alloc: fix move_freepages

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Date:   Mon, 11 Sep 2023 16:23:21 -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 4/6] mm: page_alloc: fix move_freepages_block() range
 error

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

> When a block is partially outside the zone of the cursor page, the
> function cuts the range to the pivot page instead of the zone
> start. This can leave large parts of the block behind, which
> encourages incompatible page mixing down the line (ask for one type,
> get another), and thus long-term fragmentation.
>
> This triggers reliably on the first block in the DMA zone, whose
> start_pfn is 1. The block is stolen, but everything before the pivot
> page (which was often hundreds of pages) is left on the old list.
>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> ---
>  mm/page_alloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

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


--
Best Regards,
Yan, Zi

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