linux-kernel - Re: [PATCH 1/4] mm: compaction: Ensure rescanning only happens on partially scanned pageblocks

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Date:   Thu, 25 May 2023 11:57:01 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Pedro Falcato <pedro.falcato@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Chuyi Zhou <zhouchuyi@...edance.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] mm: compaction: Ensure rescanning only happens on
 partially scanned pageblocks

On 5/15/23 13:33, Mel Gorman wrote:
> compact_zone() intends to rescan pageblocks if there is a failure to
> migrate "within the current order-aligned block". However, the pageblock
> scan may already be complete and moved to the next block causing the
> next pageblock to be "rescanned". Ensure only the most recent pageblock
> is rescanned.
> 
> Reported-by: Vlastimil Babka <vbabka@...e.cz>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

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

> ---
>  mm/compaction.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index c8bcdea15f5f..81791c124bb8 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -2464,8 +2464,9 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
>  			 * fast_find_migrateblock revisiting blocks that were
>  			 * recently partially scanned.
>  			 */
> -			if (cc->direct_compaction && !cc->finish_pageblock &&
> -						(cc->mode < MIGRATE_SYNC)) {
> +			if (!pageblock_aligned(cc->migrate_pfn) &&
> +			    cc->direct_compaction && !cc->finish_pageblock &&
> +			    (cc->mode < MIGRATE_SYNC)) {
>  				cc->finish_pageblock = true;
>  
>  				/*