linux-kernel - Re: [PATCH 3/6] mm: page_alloc: move free pages when converting block during isolation

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Date:   Thu, 14 Sep 2023 11:03:04 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Zi Yan <ziy@...dia.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] mm: page_alloc: move free pages when converting
 block during isolation

On Mon, Sep 11, 2023 at 03:41:44PM -0400, Johannes Weiner wrote:
> When claiming a block during compaction isolation, move any remaining
> free pages to the correct freelists as well, instead of stranding them
> on the wrong list. Otherwise, this encourages incompatible page mixing
> down the line, and thus long-term fragmentation.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Hmm, this is potentially expensive in some cases but it's also correct.
Given how expensive the whole path is, I doubt it's noticable and some of
this activity will be !direct_compaction anyway and relatively invisible
even if I'm not a fan of hiding overhead in kthreads. Either way;

Acked-by: Mel Gorman <mgorman@...hsingularity.net>

-- 
Mel Gorman
SUSE Labs