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Subject: Re: [RFC 12/13] mm, compaction: more reliably increase direct
 compaction priority
References: <1462865763-22084-1-git-send-email-vbabka@suse.cz>
 <1462865763-22084-13-git-send-email-vbabka@suse.cz>
From: Vlastimil Babka <vbabka@suse.cz>
Message-ID: <5731DA32.7090707@suse.cz>
Date: Tue, 10 May 2016 14:55:14 +0200
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Sender: owner-linux-mm@kvack.org
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To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Rik van Riel <riel@redhat.com>, David Rientjes <rientjes@google.com>, Mel Gorman <mgorman@techsingularity.net>, Johannes Weiner <hannes@cmpxchg.org>, Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>, linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@linux-foundation.org>

On 05/10/2016 09:36 AM, Vlastimil Babka wrote:
>   	/*
> -	 * compaction considers all the zone as desperately out of memory
> -	 * so it doesn't really make much sense to retry except when the
> -	 * failure could be caused by insufficient priority
> +	 * Compaction backed off due to watermark checks for order-0
> +	 * so the regular reclaim has to try harder and reclaim something
> +	 * Retry only if it looks like reclaim might have a chance.
>   	 */
> -	if (compaction_failed(compact_result)) {
> -		if (*compact_priority > 0) {
> -			(*compact_priority)--;
> -			return true;
> -		}
> -		return false;
> -	}

Oops, looks like my editing resulted in compaction_failed() check to be
removed completely, which wasn't intentional and can lead to infinite
loops. This should be added on top.

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