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Message-ID: <df866e1b-a052-4323-8662-cef5d924fa2b@suse.cz>
Date:   Thu, 25 May 2023 11:57:01 +0200
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Subject: Re: [PATCH 1/4] mm: compaction: Ensure rescanning only happens on
 partially scanned pageblocks
To:     Mel Gorman <mgorman@techsingularity.net>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Maxim Levitsky <mlevitsk@redhat.com>,
        Michal Hocko <mhocko@kernel.org>,
        Pedro Falcato <pedro.falcato@gmail.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Chuyi Zhou <zhouchuyi@bytedance.com>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <20230515113344.6869-1-mgorman@techsingularity.net>
 <20230515113344.6869-2-mgorman@techsingularity.net>
Content-Language: en-US
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20230515113344.6869-2-mgorman@techsingularity.net>
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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@suse.cz>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

Acked-by: Vlastimil Babka <vbabka@suse.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;
>  
>  				/*