linux-kernel - Re: [PATCH 3/3] mm/compaction: add an is_via_compact

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Message-ID: <20150921161949.GG19811@dhcp22.suse.cz>
Date:	Mon, 21 Sep 2015 18:19:49 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Yaowei Bai <bywxiaobai@....com>
Cc:	akpm@...ux-foundation.org, mgorman@...e.de, rientjes@...gle.com,
	hannes@...xchg.org, vdavydov@...allels.com, oleg@...hat.com,
	vbabka@...e.cz, iamjoonsoo.kim@....com, zhangyanfei@...fujitsu.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] mm/compaction: add an is_via_compact_memory helper
 function

On Wed 16-09-15 20:00:00, Yaowei Bai wrote:
> Introduce is_via_compact_memory helper function indicating compacting
> via /proc/sys/vm/compact_memory to improve readability.
> 
> To catch this situation in __compaction_suitable, use order as parameter
> directly instead of using struct compact_control.
> 
> This patch has no functional changes.

This is a similar case as for the sysrq_oom. I do not like the name that
much though. I am not familiar with the compaction too much to help you
with a better name, unfortunatelly. Maybe is_global_compaction()...

> 
> Signed-off-by: Yaowei Bai <bywxiaobai@....com>
> ---
>  mm/compaction.c | 26 ++++++++++++++------------
>  1 file changed, 14 insertions(+), 12 deletions(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index c5c627a..a8e6593 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1197,6 +1197,15 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
>  	return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
>  }
>  
> +/*
> + * order == -1 is expected when compacting via
> + * /proc/sys/vm/compact_memory
> + */
> +static inline bool is_via_compact_memory(int order)
> +{
> +	return order == -1;
> +}
> +
>  static int __compact_finished(struct zone *zone, struct compact_control *cc,
>  			    const int migratetype)
>  {
> @@ -1223,11 +1232,7 @@ static int __compact_finished(struct zone *zone, struct compact_control *cc,
>  		return COMPACT_COMPLETE;
>  	}
>  
> -	/*
> -	 * order == -1 is expected when compacting via
> -	 * /proc/sys/vm/compact_memory
> -	 */
> -	if (cc->order == -1)
> +	if (is_via_compact_memory(cc->order))
>  		return COMPACT_CONTINUE;
>  
>  	/* Compaction run is not finished if the watermark is not met */
> @@ -1290,11 +1295,7 @@ static unsigned long __compaction_suitable(struct zone *zone, int order,
>  	int fragindex;
>  	unsigned long watermark;
>  
> -	/*
> -	 * order == -1 is expected when compacting via
> -	 * /proc/sys/vm/compact_memory
> -	 */
> -	if (order == -1)
> +	if (is_via_compact_memory(order))
>  		return COMPACT_CONTINUE;
>  
>  	watermark = low_wmark_pages(zone);
> @@ -1658,10 +1659,11 @@ static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
>  		 * this makes sure we compact the whole zone regardless of
>  		 * cached scanner positions.
>  		 */
> -		if (cc->order == -1)
> +		if (is_via_compact_memory(cc->order))
>  			__reset_isolation_suitable(zone);
>  
> -		if (cc->order == -1 || !compaction_deferred(zone, cc->order))
> +		if (is_via_compact_memory(cc->order) ||
> +				!compaction_deferred(zone, cc->order))
>  			compact_zone(zone, cc);
>  
>  		if (cc->order > 0) {
> -- 
> 1.9.1
> 
> 
> --
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-- 
Michal Hocko
SUSE Labs
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