Re: [patch 02/11] mm: vmscan: distinguish global reclaim from globalLRU scanning

[Michal Hocko]

On Mon 12-09-11 12:57:19, Johannes Weiner wrote:
> The traditional zone reclaim code is scanning the per-zone LRU lists
> during direct reclaim and kswapd, and the per-zone per-memory cgroup
> LRU lists when reclaiming on behalf of a memory cgroup limit.
> 
> Subsequent patches will convert the traditional reclaim code to
> reclaim exclusively from the per-memory cgroup LRU lists.  As a
> result, using the predicate for which LRU list is scanned will no
> longer be appropriate to tell global reclaim from limit reclaim.
> 
> This patch adds a global_reclaim() predicate to tell direct/kswapd
> reclaim from memory cgroup limit reclaim and substitutes it in all
> places where currently scanning_global_lru() is used for that.

I am wondering about vmscan_swappiness. Shouldn't it use global_reclaim
instead?

Other than that it looks good to me.

Reviewed-by: Michal Hocko <mhocko@xxxxxxx>

> 
> Signed-off-by: Johannes Weiner <jweiner@xxxxxxxxxx>
> ---
>  mm/vmscan.c |   60 +++++++++++++++++++++++++++++++++++-----------------------
>  1 files changed, 36 insertions(+), 24 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 7502726..354f125 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -153,9 +153,25 @@ static LIST_HEAD(shrinker_list);
>  static DECLARE_RWSEM(shrinker_rwsem);
>  
>  #ifdef CONFIG_CGROUP_MEM_RES_CTLR
> -#define scanning_global_lru(sc)	(!(sc)->mem_cgroup)
> +static bool global_reclaim(struct scan_control *sc)
> +{
> +	return !sc->mem_cgroup;
> +}
> +
> +static bool scanning_global_lru(struct scan_control *sc)
> +{
> +	return !sc->mem_cgroup;
> +}
>  #else
> -#define scanning_global_lru(sc)	(1)
> +static bool global_reclaim(struct scan_control *sc)
> +{
> +	return true;
> +}
> +
> +static bool scanning_global_lru(struct scan_control *sc)
> +{
> +	return true;
> +}
>  #endif
>  
>  static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
> @@ -1011,7 +1027,7 @@ keep_lumpy:
>  	 * back off and wait for congestion to clear because further reclaim
>  	 * will encounter the same problem
>  	 */
> -	if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
> +	if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc))
>  		zone_set_flag(zone, ZONE_CONGESTED);
>  
>  	free_page_list(&free_pages);
> @@ -1330,7 +1346,7 @@ static int too_many_isolated(struct zone *zone, int file,
>  	if (current_is_kswapd())
>  		return 0;
>  
> -	if (!scanning_global_lru(sc))
> +	if (!global_reclaim(sc))
>  		return 0;
>  
>  	if (file) {
> @@ -1508,6 +1524,12 @@ 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, reclaim_mode, zone, 0, file);
> +	} else {
> +		nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list,
> +			&nr_scanned, sc->order, reclaim_mode, zone,
> +			sc->mem_cgroup, 0, file);
> +	}
> +	if (global_reclaim(sc)) {
>  		zone->pages_scanned += nr_scanned;
>  		if (current_is_kswapd())
>  			__count_zone_vm_events(PGSCAN_KSWAPD, zone,
> @@ -1515,14 +1537,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>  		else
>  			__count_zone_vm_events(PGSCAN_DIRECT, zone,
>  					       nr_scanned);
> -	} else {
> -		nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list,
> -			&nr_scanned, sc->order, reclaim_mode, zone,
> -			sc->mem_cgroup, 0, file);
> -		/*
> -		 * mem_cgroup_isolate_pages() keeps track of
> -		 * scanned pages on its own.
> -		 */
>  	}
>  
>  	if (nr_taken == 0) {
> @@ -1647,18 +1661,16 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
>  						&pgscanned, sc->order,
>  						reclaim_mode, zone,
>  						1, file);
> -		zone->pages_scanned += pgscanned;
>  	} else {
>  		nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
>  						&pgscanned, sc->order,
>  						reclaim_mode, zone,
>  						sc->mem_cgroup, 1, file);
> -		/*
> -		 * mem_cgroup_isolate_pages() keeps track of
> -		 * scanned pages on its own.
> -		 */
>  	}
>  
> +	if (global_reclaim(sc))
> +		zone->pages_scanned += pgscanned;
> +
>  	reclaim_stat->recent_scanned[file] += nr_taken;
>  
>  	__count_zone_vm_events(PGREFILL, zone, pgscanned);
> @@ -1863,9 +1875,9 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
>  	 * latencies, so it's better to scan a minimum amount there as
>  	 * well.
>  	 */
> -	if (scanning_global_lru(sc) && current_is_kswapd())
> +	if (current_is_kswapd())
>  		force_scan = true;
> -	if (!scanning_global_lru(sc))
> +	if (!global_reclaim(sc))
>  		force_scan = true;
>  
>  	/* If we have no swap space, do not bother scanning anon pages. */
> @@ -1882,7 +1894,7 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
>  	file  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
>  		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
>  
> -	if (scanning_global_lru(sc)) {
> +	if (global_reclaim(sc)) {
>  		free  = zone_page_state(zone, NR_FREE_PAGES);
>  		/* If we have very few page cache pages,
>  		   force-scan anon pages. */
> @@ -2109,7 +2121,7 @@ static void shrink_zones(int priority, struct zonelist *zonelist,
>  		 * Take care memory controller reclaiming has small influence
>  		 * to global LRU.
>  		 */
> -		if (scanning_global_lru(sc)) {
> +		if (global_reclaim(sc)) {
>  			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
>  				continue;
>  			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
> @@ -2188,7 +2200,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
>  	get_mems_allowed();
>  	delayacct_freepages_start();
>  
> -	if (scanning_global_lru(sc))
> +	if (global_reclaim(sc))
>  		count_vm_event(ALLOCSTALL);
>  
>  	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
> @@ -2200,7 +2212,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
>  		 * Don't shrink slabs when reclaiming memory from
>  		 * over limit cgroups
>  		 */
> -		if (scanning_global_lru(sc)) {
> +		if (global_reclaim(sc)) {
>  			unsigned long lru_pages = 0;
>  			for_each_zone_zonelist(zone, z, zonelist,
>  					gfp_zone(sc->gfp_mask)) {
> @@ -2261,7 +2273,7 @@ out:
>  		return 0;
>  
>  	/* top priority shrink_zones still had more to do? don't OOM, then */
> -	if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
> +	if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
>  		return 1;
>  
>  	return 0;
> -- 
> 1.7.6
> 

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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