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

[Mel Gorman <mel@csn.ul.ie>]

On Sun, Nov 14, 2010 at 02:40:21PM +0900, KOSAKI Motohiro wrote:
> > 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@csn.ul.ie>
> > ---
> >  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.
> 

Will do.

> 
> >  
> >  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))
> 

I had this initially but I found myself getting confused during development
because I had to recall each time "if it's not contig reclaim, what is it?" -
It could be either compaction or single. I decided to spell it out
because it was easier to understand but I can switch back if necessary.

> btw, LUMPY_MODE_ASYNC can be removed too.
> 

Similar reasoning - even though I'm not doing anything with the information,
I found it easier to understand if it was spelled out.

> >  	/*
> > @@ -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
> > 
> 
> 
> 

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab