Re: [PATCH 1/5] mm: compaction: encapsulate defer reset logic

[Mel Gorman]

On Mon, Nov 25, 2013 at 03:26:06PM +0100, Vlastimil Babka wrote:
> Currently there are several functions to manipulate the deferred compaction
> state variables. The remaining case where the variables are touched directly
> is when a successful allocation occurs in direct compaction, or is expected
> to be successful in the future by kswapd. Here, the lowest order that is
> expected to fail is updated, and in the case of direct compaction, the deferred
> status is reset completely.
> 
> Create a new function compaction_defer_reset() to encapsulate this
> functionality and make it easier to understand the code. No functional change.
> 
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxx>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
>  include/linux/compaction.h | 12 ++++++++++++
>  mm/compaction.c            |  9 ++++-----
>  mm/page_alloc.c            |  5 +----
>  3 files changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> index 091d72e..da39978 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -62,6 +62,18 @@ static inline bool compaction_deferred(struct zone *zone, int order)
>  	return zone->compact_considered < defer_limit;
>  }
>  
> +/* Update defer tracking counters after successful allocation of given order */
> +static inline void compaction_defer_reset(struct zone *zone, int order,
> +		bool reset_shift)
> +{
> +	if (reset_shift) {
> +		zone->compact_considered = 0;
> +		zone->compact_defer_shift = 0;
> +	}
> +	if (order >= zone->compact_order_failed)
> +		zone->compact_order_failed = order + 1;
> +}
> +

Nit pick

The comment says this is called after a successful allocation but that
is only true in one case. s/allocation/compaction/ ?

reset_shift says what it does but not why and exposes an unnecessary. If
this sees a second revision, maybe consider renaming it to something like
alloc_success?

With or without changes;

Acked-by: Mel Gorman <mgorman@xxxxxxx>

-- 
Mel Gorman
SUSE Labs
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