linux-kernel - Re: [PATCH v2 1/2] mm: compaction: consider the number of scanning compound pages in isolate fail path

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Message-ID: <3c77182b-5c41-65ec-afca-42625eadfae4@suse.cz>
Date:   Thu, 16 Mar 2023 13:12:34 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>,
        akpm@...ux-foundation.org
Cc:     mgorman@...hsingularity.net, osalvador@...e.de,
        william.lam@...edance.com, mike.kravetz@...cle.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] mm: compaction: consider the number of scanning
 compound pages in isolate fail path

On 3/16/23 12:06, Baolin Wang wrote:
> The commit b717d6b93b54 ("mm: compaction: include compound page count
> for scanning in pageblock isolation") had added compound page statistics
> for scanning in pageblock isolation, to make sure the number of scanned
> pages are always larger than the number of isolated pages when isolating
> mirgratable or free pageblock.
> 
> However, when failed to isolate the pages when scanning the mirgratable or
> free pageblock, the isolation failure path did not consider the scanning
> statistics of the compound pages, which can show the incorrect number of
> scanned pages in tracepoints or the vmstats to make people confusing about
> the page scanning pressure in memory compaction.
> 
> Thus we should take into account the number of scanning pages when failed
> to isolate the compound pages to make the statistics accurate.
> 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>

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

Thanks!