Re: [PATCH 6/6] mm: compaction: skip fast freepages isolation if enough freepages are isolated

[Vlastimil Babka]

On 5/25/23 14:54, Baolin Wang wrote:
> I've observed that fast isolation often isolates more pages than
> cc->migratepages, and the excess freepages will be released back to the
> buddy system. So skip fast freepages isolation if enough freepages are
> isolated to save some CPU cycles.
> 
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>  mm/compaction.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index eccec84dae82..3ade4c095ed2 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1550,6 +1550,10 @@ static void fast_isolate_freepages(struct compact_control *cc)
>  
>  		spin_unlock_irqrestore(&cc->zone->lock, flags);
>  
> +		/* Skip fast search if enough freepages isolated */
> +		if (cc->nr_freepages >= cc->nr_migratepages)
> +			break;
> +
>  		/*
>  		 * Smaller scan on next order so the total scan is related
>  		 * to freelist_scan_limit.