linux-kernel - Re: [PATCH 11/34] mm, vmscan: remove duplicate logic clearing node congestion and dirty state

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Date:	Tue, 12 Jul 2016 10:22:56 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Minchan Kim <minchan@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 11/34] mm, vmscan: remove duplicate logic clearing node
 congestion and dirty state

On Fri, Jul 08, 2016 at 10:34:47AM +0100, Mel Gorman wrote:
> @@ -3008,7 +3008,17 @@ static bool zone_balanced(struct zone *zone, int order, int classzone_idx)
>  {
>  	unsigned long mark = high_wmark_pages(zone);
>  
> -	return zone_watermark_ok_safe(zone, order, mark, classzone_idx);
> +	if (!zone_watermark_ok_safe(zone, order, mark, classzone_idx))
> +		return false;
> +
> +	/*
> +	 * If any eligible zone is balanced then the node is not considered
> +	 * to be congested or dirty
> +	 */
> +	clear_bit(PGDAT_CONGESTED, &zone->zone_pgdat->flags);
> +	clear_bit(PGDAT_DIRTY, &zone->zone_pgdat->flags);

Predicate functions that secretly modify internal state give me the
willies... The diffstat is flat, too. Is this really an improvement?