Re: [PATCH 3/6] mm: kswapd: Continue reclaiming for reclaim/compaction if the minimum number of pages have not been reclaimed

[Minchan Kim <minchan@kernel.org>]

On Tue, Aug 07, 2012 at 01:31:14PM +0100, Mel Gorman wrote:
> When direct reclaim is running reclaim/compaction, there is a minimum
> number of pages it reclaims. As it must be under the low watermark to be
> in direct reclaim it has also woken kswapd to do some work. This patch
> has kswapd use the same logic as direct reclaim to reclaim a minimum
> number of pages so compaction can run later.

-ENOPARSE by my stupid brain.
Could you elaborate a bit more?

> 
> Signed-off-by: Mel Gorman <mgorman@suse.de>
> ---
>  mm/vmscan.c |   19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 0cb2593..afdec93 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1701,7 +1701,7 @@ static bool in_reclaim_compaction(struct scan_control *sc)
>   * calls try_to_compact_zone() that it will have enough free pages to succeed.
>   * It will give up earlier than that if there is difficulty reclaiming pages.
>   */
> -static inline bool should_continue_reclaim(struct lruvec *lruvec,
> +static bool should_continue_reclaim(struct lruvec *lruvec,
>  					unsigned long nr_reclaimed,
>  					unsigned long nr_scanned,
>  					struct scan_control *sc)
> @@ -1768,6 +1768,17 @@ static inline bool should_continue_reclaim(struct lruvec *lruvec,
>  	}
>  }
>  
> +static inline bool should_continue_reclaim_zone(struct zone *zone,
> +					unsigned long nr_reclaimed,
> +					unsigned long nr_scanned,
> +					struct scan_control *sc)
> +{
> +	struct mem_cgroup *memcg = mem_cgroup_iter(NULL, NULL, NULL);
> +	struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
> +
> +	return should_continue_reclaim(lruvec, nr_reclaimed, nr_scanned, sc);
> +}
> +
>  /*
>   * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
>   */
> @@ -2496,8 +2507,10 @@ loop_again:
>  			 */
>  			testorder = order;
>  			if (COMPACTION_BUILD && order &&
> -					compaction_suitable(zone, order) !=
> -						COMPACT_SKIPPED)
> +					!should_continue_reclaim_zone(zone,
> +						nr_soft_reclaimed,

nr_soft_reclaimed is always zero with !CONFIG_MEMCG.
So should_continue_reclaim_zone would return normally true in case of
non-__GFP_REPEAT allocation. Is it intentional?


> +						sc.nr_scanned - nr_soft_scanned,
> +						&sc))
>  				testorder = 0;
>  
>  			if ((buffer_heads_over_limit && is_highmem_idx(i)) ||
> -- 
> 1.7.9.2
> 
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-- 
Kind regards,
Minchan Kim