Re: [PATCH 1/3] mm,vmscan: Convert lumpy_mode into a bitmask

[KOSAKI Motohiro]

> Currently lumpy_mode is an enum and determines if lumpy reclaim is off,
> syncronous or asyncronous. In preparation for using compaction instead of
> lumpy reclaim, this patch converts the flags into a bitmap.
> 
> Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
> ---
>  include/trace/events/vmscan.h |    6 +++---
>  mm/vmscan.c                   |   37 +++++++++++++++++++------------------
>  2 files changed, 22 insertions(+), 21 deletions(-)
> 
> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
> index c255fcc..be76429 100644
> --- a/include/trace/events/vmscan.h
> +++ b/include/trace/events/vmscan.h
> @@ -25,13 +25,13 @@
>  
>  #define trace_reclaim_flags(page, sync) ( \
>  	(page_is_file_cache(page) ? RECLAIM_WB_FILE : RECLAIM_WB_ANON) | \
> -	(sync == LUMPY_MODE_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC)   \
> +	(sync & LUMPY_MODE_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC)   \
>  	)
>  
>  #define trace_shrink_flags(file, sync) ( \
> -	(sync == LUMPY_MODE_SYNC ? RECLAIM_WB_MIXED : \
> +	(sync & LUMPY_MODE_SYNC ? RECLAIM_WB_MIXED : \
>  			(file ? RECLAIM_WB_FILE : RECLAIM_WB_ANON)) |  \
> -	(sync == LUMPY_MODE_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC) \
> +	(sync & LUMPY_MODE_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC) \
>  	)
>  
>  TRACE_EVENT(mm_vmscan_kswapd_sleep,
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index b8a6fdc..ffa438e 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -51,11 +51,11 @@
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/vmscan.h>
>  
> -enum lumpy_mode {
> -	LUMPY_MODE_NONE,
> -	LUMPY_MODE_ASYNC,
> -	LUMPY_MODE_SYNC,
> -};
> +typedef unsigned __bitwise__ lumpy_mode;
> +#define LUMPY_MODE_SINGLE		((__force lumpy_mode)0x01u)
> +#define LUMPY_MODE_ASYNC		((__force lumpy_mode)0x02u)
> +#define LUMPY_MODE_SYNC			((__force lumpy_mode)0x04u)
> +#define LUMPY_MODE_CONTIGRECLAIM	((__force lumpy_mode)0x08u)

Please write a comment of description of each bit meaning.


>  
>  struct scan_control {
>  	/* Incremented by the number of inactive pages that were scanned */
> @@ -88,7 +88,7 @@ struct scan_control {
>  	 * Intend to reclaim enough continuous memory rather than reclaim
>  	 * enough amount of memory. i.e, mode for high order allocation.
>  	 */
> -	enum lumpy_mode lumpy_reclaim_mode;
> +	lumpy_mode lumpy_reclaim_mode;
>  
>  	/* Which cgroup do we reclaim from */
>  	struct mem_cgroup *mem_cgroup;
> @@ -274,13 +274,13 @@ unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
>  static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc,
>  				   bool sync)
>  {
> -	enum lumpy_mode mode = sync ? LUMPY_MODE_SYNC : LUMPY_MODE_ASYNC;
> +	lumpy_mode mode = sync ? LUMPY_MODE_SYNC : LUMPY_MODE_ASYNC;
>  
>  	/*
>  	 * Some reclaim have alredy been failed. No worth to try synchronous
>  	 * lumpy reclaim.
>  	 */
> -	if (sync && sc->lumpy_reclaim_mode == LUMPY_MODE_NONE)
> +	if (sync && sc->lumpy_reclaim_mode & LUMPY_MODE_SINGLE)
>  		return;

Probaby, we can remove LUMPY_MODE_SINGLE entirely. and this line can be
change to

	if (sync && !(sc->lumpy_reclaim_mode & LUMPY_MODE_CONTIGRECLAIM))


btw, LUMPY_MODE_ASYNC can be removed too.


>  
>  	/*
> @@ -288,17 +288,18 @@ static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc,
>  	 * trouble getting a small set of contiguous pages, we
>  	 * will reclaim both active and inactive pages.
>  	 */
> +	sc->lumpy_reclaim_mode = LUMPY_MODE_CONTIGRECLAIM;
>  	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
> -		sc->lumpy_reclaim_mode = mode;
> +		sc->lumpy_reclaim_mode |= mode;
>  	else if (sc->order && priority < DEF_PRIORITY - 2)
> -		sc->lumpy_reclaim_mode = mode;
> +		sc->lumpy_reclaim_mode |= mode;
>  	else
> -		sc->lumpy_reclaim_mode = LUMPY_MODE_NONE;
> +		sc->lumpy_reclaim_mode = LUMPY_MODE_SINGLE | LUMPY_MODE_ASYNC;
>  }
>  
>  static void disable_lumpy_reclaim_mode(struct scan_control *sc)
>  {
> -	sc->lumpy_reclaim_mode = LUMPY_MODE_NONE;
> +	sc->lumpy_reclaim_mode = LUMPY_MODE_SINGLE | LUMPY_MODE_ASYNC;
>  }
>  
>  static inline int is_page_cache_freeable(struct page *page)
> @@ -429,7 +430,7 @@ static pageout_t pageout(struct page *page, struct address_space *mapping,
>  		 * first attempt to free a range of pages fails.
>  		 */
>  		if (PageWriteback(page) &&
> -		    sc->lumpy_reclaim_mode == LUMPY_MODE_SYNC)
> +		    (sc->lumpy_reclaim_mode & LUMPY_MODE_SYNC))
>  			wait_on_page_writeback(page);
>  
>  		if (!PageWriteback(page)) {
> @@ -615,7 +616,7 @@ static enum page_references page_check_references(struct page *page,
>  	referenced_page = TestClearPageReferenced(page);
>  
>  	/* Lumpy reclaim - ignore references */
> -	if (sc->lumpy_reclaim_mode != LUMPY_MODE_NONE)
> +	if (sc->lumpy_reclaim_mode & LUMPY_MODE_CONTIGRECLAIM)
>  		return PAGEREF_RECLAIM;
>  
>  	/*
> @@ -732,7 +733,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>  			 * for any page for which writeback has already
>  			 * started.
>  			 */
> -			if (sc->lumpy_reclaim_mode == LUMPY_MODE_SYNC &&
> +			if ((sc->lumpy_reclaim_mode & LUMPY_MODE_SYNC) &&
>  			    may_enter_fs)
>  				wait_on_page_writeback(page);
>  			else {
> @@ -1317,7 +1318,7 @@ static inline bool should_reclaim_stall(unsigned long nr_taken,
>  		return false;
>  
>  	/* Only stall on lumpy reclaim */
> -	if (sc->lumpy_reclaim_mode == LUMPY_MODE_NONE)
> +	if (sc->lumpy_reclaim_mode & LUMPY_MODE_SINGLE)
>  		return false;
>  
>  	/* If we have relaimed everything on the isolated list, no stall */
> @@ -1368,7 +1369,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>  	if (scanning_global_lru(sc)) {
>  		nr_taken = isolate_pages_global(nr_to_scan,
>  			&page_list, &nr_scanned, sc->order,
> -			sc->lumpy_reclaim_mode == LUMPY_MODE_NONE ?
> +			sc->lumpy_reclaim_mode & LUMPY_MODE_SINGLE ?
>  					ISOLATE_INACTIVE : ISOLATE_BOTH,
>  			zone, 0, file);
>  		zone->pages_scanned += nr_scanned;
> @@ -1381,7 +1382,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>  	} else {
>  		nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
>  			&page_list, &nr_scanned, sc->order,
> -			sc->lumpy_reclaim_mode == LUMPY_MODE_NONE ?
> +			sc->lumpy_reclaim_mode & LUMPY_MODE_SINGLE ?
>  					ISOLATE_INACTIVE : ISOLATE_BOTH,
>  			zone, sc->mem_cgroup,
>  			0, file);
> -- 
> 1.7.1
> 



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