Re: [PATCH 04/10] mm: vmscan: Decide whether to compact the pgdatbased on reclaim progress

[Johannes Weiner]

On Thu, Apr 11, 2013 at 08:57:52PM +0100, Mel Gorman wrote:
> @@ -2763,7 +2769,21 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
>  		for (i = 0; i <= end_zone; i++) {
>  			struct zone *zone = pgdat->node_zones + i;
>  
> +			if (!populated_zone(zone))
> +				continue;
> +
>  			lru_pages += zone_reclaimable_pages(zone);
> +
> +			/*
> +			 * If any zone is currently balanced then kswapd will
> +			 * not call compaction as it is expected that the
> +			 * necessary pages are already available.
> +			 */
> +			if (pgdat_needs_compaction &&
> +					zone_watermark_ok(zone, order,
> +						low_wmark_pages(zone),
> +						*classzone_idx, 0))
> +				pgdat_needs_compaction = false;
>  		}
>  
>  		/*
> @@ -2832,7 +2852,8 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
>  				 * already being scanned that high
>  				 * watermark would be met at 100% efficiency.
>  				 */
> -				if (kswapd_shrink_zone(zone, &sc, lru_pages))
> +				if (kswapd_shrink_zone(zone, &sc, lru_pages,
> +						       &nr_attempted))
>  					raise_priority = false;
>  			}

There is the odd chance that the watermark is met after reclaim, would
it make sense to defer the pgdat_needs_compaction check?  Not really a
big deal, though, so:

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
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