linux-kernel - Re: [PATCH 04/27] mm, vmscan: Begin reclaiming pages on a per-node basis

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Date:	Sun, 12 Jun 2016 15:33:25 +0800
From:	"Hillf Danton" <hillf.zj@...baba-inc.com>
To:	"'Mel Gorman'" <mgorman@...hsingularity.net>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH 04/27] mm, vmscan: Begin reclaiming pages on a per-node basis

> @@ -3207,15 +3228,14 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
>  			sc.may_writepage = 1;
> 
>  		/*
> -		 * Now scan the zone in the dma->highmem direction, stopping
> -		 * at the last zone which needs scanning.
> -		 *
> -		 * We do this because the page allocator works in the opposite
> -		 * direction.  This prevents the page allocator from allocating
> -		 * pages behind kswapd's direction of progress, which would
> -		 * cause too much scanning of the lower zones.
> +		 * Continue scanning in the highmem->dma direction stopping at
> +		 * the last zone which needs scanning. This may reclaim lowmem
> +		 * pages that are not necessary for zone balancing but it
> +		 * preserves LRU ordering. It is assumed that the bulk of
> +		 * allocation requests can use arbitrary zones with the
> +		 * possible exception of big highmem:lowmem configurations.
>  		 */
> -		for (i = 0; i <= end_zone; i++) {
> +		for (i = end_zone; i >= end_zone; i--) {

s/i >= end_zone;/i >= 0;/ ?

>  			struct zone *zone = pgdat->node_zones + i;
> 
>  			if (!populated_zone(zone))