linux-kernel - Re: [PATCH 1/2] mm: use is_migrate_highatomic() to simplify the code

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Date:   Fri, 3 Mar 2017 14:18:08 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Xishi Qiu <qiuxishi@...wei.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Minchan Kim <minchan@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Yisheng Xie <xieyisheng1@...wei.com>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mm: use is_migrate_highatomic() to simplify the code

On Fri 03-03-17 19:10:13, Xishi Qiu wrote:
> Introduce two helpers, is_migrate_highatomic() and is_migrate_highatomic_page().
> Simplify the code, no functional changes.

static inline helpers would be nicer than macros

> Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>

OK this fits with other MIGRATE_$FOO types

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  include/linux/mmzone.h |  5 +++++
>  mm/page_alloc.c        | 14 ++++++--------
>  2 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 8e02b37..8124440 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -66,6 +66,11 @@ enum {
>  /* In mm/page_alloc.c; keep in sync also with show_migration_types() there */
>  extern char * const migratetype_names[MIGRATE_TYPES];
>  
> +#define is_migrate_highatomic(migratetype)				\
> +	(migratetype == MIGRATE_HIGHATOMIC)
> +#define is_migrate_highatomic_page(_page)				\
> +	(get_pageblock_migratetype(_page) == MIGRATE_HIGHATOMIC)
> +
>  #ifdef CONFIG_CMA
>  #  define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
>  #  define is_migrate_cma_page(_page) (get_pageblock_migratetype(_page) == MIGRATE_CMA)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9f9623d..40d79a6 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2040,8 +2040,8 @@ static void reserve_highatomic_pageblock(struct page *page, struct zone *zone,
>  
>  	/* Yoink! */
>  	mt = get_pageblock_migratetype(page);
> -	if (mt != MIGRATE_HIGHATOMIC &&
> -			!is_migrate_isolate(mt) && !is_migrate_cma(mt)) {
> +	if (!is_migrate_highatomic(mt) && !is_migrate_isolate(mt)
> +	    && !is_migrate_cma(mt)) {
>  		zone->nr_reserved_highatomic += pageblock_nr_pages;
>  		set_pageblock_migratetype(page, MIGRATE_HIGHATOMIC);
>  		move_freepages_block(zone, page, MIGRATE_HIGHATOMIC);
> @@ -2098,8 +2098,7 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
>  			 * from highatomic to ac->migratetype. So we should
>  			 * adjust the count once.
>  			 */
> -			if (get_pageblock_migratetype(page) ==
> -							MIGRATE_HIGHATOMIC) {
> +			if (is_migrate_highatomic_page(page)) {
>  				/*
>  				 * It should never happen but changes to
>  				 * locking could inadvertently allow a per-cpu
> @@ -2156,8 +2155,7 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
>  
>  		page = list_first_entry(&area->free_list[fallback_mt],
>  						struct page, lru);
> -		if (can_steal &&
> -			get_pageblock_migratetype(page) != MIGRATE_HIGHATOMIC)
> +		if (can_steal && !is_migrate_highatomic_page(page))
>  			steal_suitable_fallback(zone, page, start_migratetype);
>  
>  		/* Remove the page from the freelists */
> @@ -2494,7 +2492,7 @@ void free_hot_cold_page(struct page *page, bool cold)
>  	/*
>  	 * We only track unmovable, reclaimable and movable on pcp lists.
>  	 * Free ISOLATE pages back to the allocator because they are being
> -	 * offlined but treat RESERVE as movable pages so we can get those
> +	 * offlined but treat HIGHATOMIC as movable pages so we can get those
>  	 * areas back if necessary. Otherwise, we may have to free
>  	 * excessively into the page allocator
>  	 */
> @@ -2605,7 +2603,7 @@ int __isolate_free_page(struct page *page, unsigned int order)
>  		for (; page < endpage; page += pageblock_nr_pages) {
>  			int mt = get_pageblock_migratetype(page);
>  			if (!is_migrate_isolate(mt) && !is_migrate_cma(mt)
> -				&& mt != MIGRATE_HIGHATOMIC)
> +			    && !is_migrate_highatomic(mt))
>  				set_pageblock_migratetype(page,
>  							  MIGRATE_MOVABLE);
>  		}
> -- 
> 1.8.3.1
> 

-- 
Michal Hocko
SUSE Labs