linux-kernel - Re: [PATCH 2/4] mm, compaction: more reliably increase direct compaction priority

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Date:   Wed, 21 Sep 2016 19:13:50 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Arkadiusz Miskiewicz <a.miskiewicz@...il.com>,
        Ralf-Peter Rohbeck <Ralf-Peter.Rohbeck@...ntum.com>,
        Olaf Hering <olaf@...fle.de>, linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-mm@...ck.org, Mel Gorman <mgorman@...hsingularity.net>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        David Rientjes <rientjes@...gle.com>,
        Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 2/4] mm, compaction: more reliably increase direct
 compaction priority

On Tue 06-09-16 15:52:56, Vlastimil Babka wrote:
[...]
> @@ -3204,6 +3199,15 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
>  	if (compaction_retries <= max_retries)
>  		return true;
>  
> +	/*
> +	 * Make sure there is at least one attempt at the highest priority
> +	 * if we exhausted all retries at the lower priorities
> +	 */
> +check_priority:
> +	if (*compact_priority > MIN_COMPACT_PRIORITY) {
> +		(*compact_priority)--;
> +		return true;

Don't we want to reset compaction_retries here? Otherwise we can consume
all retries on the lower priorities.

Other than that it looks good to me. With that you can add
Acked-by: Michal Hocko <mhocko@...e.com>

> +	}
>  	return false;
>  }
>  #else
-- 
Michal Hocko
SUSE Labs