linux-kernel - Re: [PATCH 07/14] mm, compaction: Always finish scanning of a full pageblock

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Message-ID: <d0b6cb2d-a5cd-b415-e56f-2ad145f86cbc@suse.cz>
Date:   Tue, 18 Dec 2018 10:23:54 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Mel Gorman <mgorman@...hsingularity.net>,
        Linux-MM <linux-mm@...ck.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>, ying.huang@...el.com,
        kirill@...temov.name, Andrew Morton <akpm@...ux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/14] mm, compaction: Always finish scanning of a full
 pageblock

On 12/15/18 12:03 AM, Mel Gorman wrote:
> When compaction is finishing, it uses a flag to ensure the pageblock is
> complete.  However, in general it makes sense to always complete migration
> of a pageblock. Minimally, skip information is based on a pageblock and
> partially scanned pageblocks may incur more scanning in the future. The
> pageblock skip handling also becomes more strict later in the series and
> the hint is more useful if a complete pageblock was always scanned.
> 
> The impact here is potentially on latencies as more scanning is done
> but it's not a consistent win or loss as the scanning is not always a
> high percentage of the pageblock and sometimes it is offset by future
> reductions in scanning. Hence, the results are not presented this time as
> it's a mix of gains/losses without any clear pattern. However, completing
> scanning of the pageblock is important for later patches.
> 
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

Acked-by: Vlastimil Babka <vbabka@...e.cz>