[PATCH 1/2] vmscan: separate sc.swap_cluster_max and sc.nr_max_reclaim

[PATCH 1/2] vmscan: separate sc.swap_cluster_max and sc.nr_max_reclaim

[KOSAKI Motohiro]

Rafael, Can you please review this patch series?

I found shrink_all_memory() is not fast at all on my numa system.
I think this patch series fixes it.


==============================================================
Currently, sc.scap_cluster_max has double meanings.

 1) reclaim batch size as isolate_lru_pages()'s argument
 2) reclaim baling out thresolds

The two meanings pretty unrelated. Thus, Let's separate it.
this patch doesn't change any behavior.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
 mm/vmscan.c |   19 ++++++++++++++-----
 1 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ba8228e..80e727d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -55,6 +55,9 @@ struct scan_control {
 	/* Number of pages freed so far during a call to shrink_zones() */
 	unsigned long nr_reclaimed;
 
+	/* How many pages shrink_list() should reclaim */
+	unsigned long nr_to_reclaim;
+
 	/* This context's GFP mask */
 	gfp_t gfp_mask;
 
@@ -1526,6 +1529,7 @@ static void shrink_zone(int priority, struct zone *zone,
 	enum lru_list l;
 	unsigned long nr_reclaimed = sc->nr_reclaimed;
 	unsigned long swap_cluster_max = sc->swap_cluster_max;
+	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
 	int noswap = 0;
 
 	/* If we have no swap space, do not bother scanning anon pages. */
@@ -1572,8 +1576,7 @@ static void shrink_zone(int priority, struct zone *zone,
 		 * with multiple processes reclaiming pages, the total
 		 * freeing target can get unreasonably large.
 		 */
-		if (nr_reclaimed > swap_cluster_max &&
-			priority < DEF_PRIORITY && !current_is_kswapd())
+		if (nr_reclaimed > nr_to_reclaim && priority < DEF_PRIORITY)
 			break;
 	}
 
@@ -1671,6 +1674,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 	struct zoneref *z;
 	struct zone *zone;
 	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
+	unsigned long writeback_threshold;
 
 	delayacct_freepages_start();
 
@@ -1706,7 +1710,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 			}
 		}
 		total_scanned += sc->nr_scanned;
-		if (sc->nr_reclaimed >= sc->swap_cluster_max) {
+		if (sc->nr_reclaimed >= sc->nr_to_reclaim) {
 			ret = sc->nr_reclaimed;
 			goto out;
 		}
@@ -1718,8 +1722,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 		 * that's undesirable in laptop mode, where we *want* lumpy
 		 * writeout.  So in laptop mode, write out the whole world.
 		 */
-		if (total_scanned > sc->swap_cluster_max +
-					sc->swap_cluster_max / 2) {
+		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
+		if (total_scanned > writeback_threshold) {
 			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
 			sc->may_writepage = 1;
 		}
@@ -1765,6 +1769,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 		.gfp_mask = gfp_mask,
 		.may_writepage = !laptop_mode,
 		.swap_cluster_max = SWAP_CLUSTER_MAX,
+		.nr_to_reclaim = SWAP_CLUSTER_MAX,
 		.may_unmap = 1,
 		.may_swap = 1,
 		.swappiness = vm_swappiness,
@@ -1789,6 +1794,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
 		.may_unmap = 1,
 		.may_swap = !noswap,
 		.swap_cluster_max = SWAP_CLUSTER_MAX,
+		.nr_to_reclaim = SWAP_CLUSTER_MAX,
 		.swappiness = swappiness,
 		.order = 0,
 		.mem_cgroup = mem_cont,
@@ -1837,6 +1843,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
 		.may_unmap = 1,
 		.may_swap = 1,
 		.swap_cluster_max = SWAP_CLUSTER_MAX,
+		.nr_to_reclaim = ULONG_MAX,
 		.swappiness = vm_swappiness,
 		.order = order,
 		.mem_cgroup = NULL,
@@ -2413,6 +2420,8 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
 		.may_swap = 1,
 		.swap_cluster_max = max_t(unsigned long, nr_pages,
 					SWAP_CLUSTER_MAX),
+		.nr_to_reclaim = max_t(unsigned long, nr_pages,
+				       SWAP_CLUSTER_MAX),
 		.gfp_mask = gfp_mask,
 		.swappiness = vm_swappiness,
 		.order = order,
-- 
1.6.2.5



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[PATCH 2/2] vmscan: kill shrink_all_zones()

[KOSAKI Motohiro]

shrink_all_zone() was introduced by commit d6277db4ab (swsusp: rework
memory shrinker) for hibernate performance improvement. and sc.swap_cluster_max
was introduced by commit a06fe4d307 (Speed freeing memory for suspend).

commit a06fe4d307 said

    Without the patch:
    Freed  14600 pages in  1749 jiffies = 32.61 MB/s (Anomolous!)
    Freed  88563 pages in 14719 jiffies = 23.50 MB/s
    Freed 205734 pages in 32389 jiffies = 24.81 MB/s

    With the patch:
    Freed  68252 pages in   496 jiffies = 537.52 MB/s
    Freed 116464 pages in   569 jiffies = 798.54 MB/s
    Freed 209699 pages in   705 jiffies = 1161.89 MB/s

At that time, their patch was pretty worth. However, Modern Hardware
trend and recent VM improvement broke its worth. From several reason,
I think we should remove shrink_all_zones() at all.

detail:

1) Old days, shrink_zone()'s slowness was mainly caused by stupid congestion_wait()
   at no i/o congestion.
   but current shrink_zone() is sane, not slow.

2) shrink_all_zone() try to shrink all pages at a time. but it doesn't works
   fine on numa system.
   example)
     System has 4GB memory and each node have 2GB. and hibernate need 1GB.

     optimal)
	steal 500MB from each node.
     shrink_all_zones)
	steal 1GB from node-0.

   Oh, Cache balancing was broke ;)
   Unfortunately, Desktop system moved ahead NUMA.
   (Side note, if hibernate require 2GB, shrink_all_zones() never success)

3) if the node has several I/O flighting pages, shrink_all_zones() makes
   pretty bad result.

   schenario) hibernate need 1GB

   1) shrink_all_zones() try to reclaim 1GB from Node-0
   2) but it only reclaimed 990MB
   3) stupidly, shrink_all_zones() try to reclaim 1GB from Node-1
   4) it reclaimed 990MB

   Oh, well. it reclaimed twice much than required.
   In the other hand, current shrink_zone() has sane baling out logic.
   then, it doesn't make overkill reclaim. then, we lost shrink_zones()'s risk.

4) SplitLRU VM always keep active/inactive ratio very carefully. inactive list only
   shrinking break its assumption. it makes unnecessary OOM risk. it obviously suboptimal.

  Throuput comparision
  ==============================================
  old		2192.10 MB/s
  new		2222.22 MB/s

  ok, it's almost same throuput.

Cc: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
 mm/vmscan.c |   75 +++++++++++++---------------------------------------------
 1 files changed, 17 insertions(+), 58 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 80e727d..9f28166 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2130,51 +2130,6 @@ unsigned long global_lru_pages(void)
 
 #ifdef CONFIG_HIBERNATION
 /*
- * Helper function for shrink_all_memory().  Tries to reclaim 'nr_pages' pages
- * from LRU lists system-wide, for given pass and priority.
- *
- * For pass > 3 we also try to shrink the LRU lists that contain a few pages
- */
-static void shrink_all_zones(unsigned long nr_pages, int prio,
-				      int pass, struct scan_control *sc)
-{
-	struct zone *zone;
-	unsigned long nr_reclaimed = 0;
-
-	for_each_populated_zone(zone) {
-		enum lru_list l;
-
-		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
-			continue;
-
-		for_each_evictable_lru(l) {
-			enum zone_stat_item ls = NR_LRU_BASE + l;
-			unsigned long lru_pages = zone_page_state(zone, ls);
-
-			/* For pass = 0, we don't shrink the active list */
-			if (pass == 0 && (l == LRU_ACTIVE_ANON ||
-						l == LRU_ACTIVE_FILE))
-				continue;
-
-			zone->lru[l].nr_saved_scan += (lru_pages >> prio) + 1;
-			if (zone->lru[l].nr_saved_scan >= nr_pages || pass > 3) {
-				unsigned long nr_to_scan;
-
-				zone->lru[l].nr_saved_scan = 0;
-				nr_to_scan = min(nr_pages, lru_pages);
-				nr_reclaimed += shrink_list(l, nr_to_scan, zone,
-								sc, prio);
-				if (nr_reclaimed >= nr_pages) {
-					sc->nr_reclaimed += nr_reclaimed;
-					return;
-				}
-			}
-		}
-	}
-	sc->nr_reclaimed += nr_reclaimed;
-}
-
-/*
  * Try to free `nr_pages' of memory, system-wide, and return the number of
  * freed pages.
  *
@@ -2188,12 +2143,18 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
 	int pass;
 	struct reclaim_state reclaim_state;
 	struct scan_control sc = {
-		.gfp_mask = GFP_KERNEL,
+		.gfp_mask = GFP_HIGHUSER_MOVABLE,
+		.may_swap = 0,
 		.may_unmap = 0,
 		.may_writepage = 1,
+		.swap_cluster_max = SWAP_CLUSTER_MAX,
+		.nr_to_reclaim = nr_pages,
+		.swappiness = vm_swappiness,
+		.order = 0,
 		.isolate_pages = isolate_pages_global,
-		.nr_reclaimed = 0,
 	};
+	struct zonelist * zonelist = node_zonelist(first_online_node,
+						   GFP_HIGHUSER_MOVABLE);
 
 	current->reclaim_state = &reclaim_state;
 
@@ -2215,9 +2176,9 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
 
 	/*
 	 * We try to shrink LRUs in 5 passes:
-	 * 0 = Reclaim from inactive_list only
-	 * 1 = Reclaim from active list but don't reclaim mapped
-	 * 2 = 2nd pass of type 1
+	 * 0 = Reclaim unmapped pages
+	 * 1 = 2nd pass of type 0
+	 * 2 = 3rd pass of type 0
 	 * 3 = Reclaim mapped (normal reclaim)
 	 * 4 = 2nd pass of type 3
 	 */
@@ -2225,15 +2186,15 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
 		int prio;
 
 		/* Force reclaiming mapped pages in the passes #3 and #4 */
-		if (pass > 2)
+		if (pass > 2) {
 			sc.may_unmap = 1;
+			sc.may_swap = 1;
+		}
 
 		for (prio = DEF_PRIORITY; prio >= 0; prio--) {
-			unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
-
 			sc.nr_scanned = 0;
-			sc.swap_cluster_max = nr_to_scan;
-			shrink_all_zones(nr_to_scan, prio, pass, &sc);
+
+			shrink_zones(prio, zonelist, &sc);
 			if (sc.nr_reclaimed >= nr_pages)
 				goto out;
 
@@ -2243,10 +2204,8 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
 			sc.nr_reclaimed += reclaim_state.reclaimed_slab;
 			if (sc.nr_reclaimed >= nr_pages)
 				goto out;
-
-			if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
-				congestion_wait(BLK_RW_ASYNC, HZ / 10);
 		}
+		congestion_wait(BLK_RW_ASYNC, HZ / 10);
 	}
 
 	/*
-- 
1.6.2.5



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Re: [PATCH 2/2] vmscan: kill shrink_all_zones()

[Rik van Riel]

KOSAKI Motohiro wrote:

> At that time, their patch was pretty worth. However, Modern Hardware
> trend and recent VM improvement broke its worth. From several reason,
> I think we should remove shrink_all_zones() at all.

> Cc: Rafael J. Wysocki <rjw@sisk.pl>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

Reviewed-by: Rik van Riel <riel@redhat.com>

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Re: [PATCH 2/2] vmscan: kill shrink_all_zones()

[Rafael J. Wysocki]

On Friday 09 October 2009, KOSAKI Motohiro wrote:
> shrink_all_zone() was introduced by commit d6277db4ab (swsusp: rework
> memory shrinker) for hibernate performance improvement. and sc.swap_cluster_max
> was introduced by commit a06fe4d307 (Speed freeing memory for suspend).
> 
> commit a06fe4d307 said
> 
>     Without the patch:
>     Freed  14600 pages in  1749 jiffies = 32.61 MB/s (Anomolous!)
>     Freed  88563 pages in 14719 jiffies = 23.50 MB/s
>     Freed 205734 pages in 32389 jiffies = 24.81 MB/s
> 
>     With the patch:
>     Freed  68252 pages in   496 jiffies = 537.52 MB/s
>     Freed 116464 pages in   569 jiffies = 798.54 MB/s
>     Freed 209699 pages in   705 jiffies = 1161.89 MB/s
> 
> At that time, their patch was pretty worth. However, Modern Hardware
> trend and recent VM improvement broke its worth. From several reason,
> I think we should remove shrink_all_zones() at all.
> 
> detail:
> 
> 1) Old days, shrink_zone()'s slowness was mainly caused by stupid congestion_wait()
>    at no i/o congestion.
>    but current shrink_zone() is sane, not slow.
> 
> 2) shrink_all_zone() try to shrink all pages at a time. but it doesn't works
>    fine on numa system.
>    example)
>      System has 4GB memory and each node have 2GB. and hibernate need 1GB.
> 
>      optimal)
> 	steal 500MB from each node.
>      shrink_all_zones)
> 	steal 1GB from node-0.
> 
>    Oh, Cache balancing was broke ;)
>    Unfortunately, Desktop system moved ahead NUMA.
>    (Side note, if hibernate require 2GB, shrink_all_zones() never success)
> 
> 3) if the node has several I/O flighting pages, shrink_all_zones() makes
>    pretty bad result.
> 
>    schenario) hibernate need 1GB
> 
>    1) shrink_all_zones() try to reclaim 1GB from Node-0
>    2) but it only reclaimed 990MB
>    3) stupidly, shrink_all_zones() try to reclaim 1GB from Node-1
>    4) it reclaimed 990MB
> 
>    Oh, well. it reclaimed twice much than required.
>    In the other hand, current shrink_zone() has sane baling out logic.
>    then, it doesn't make overkill reclaim. then, we lost shrink_zones()'s risk.
> 
> 4) SplitLRU VM always keep active/inactive ratio very carefully. inactive list only
>    shrinking break its assumption. it makes unnecessary OOM risk. it obviously suboptimal.
> 
>   Throuput comparision
>   ==============================================
>   old		2192.10 MB/s
>   new		2222.22 MB/s
> 
>   ok, it's almost same throuput.
> 
> Cc: Rafael J. Wysocki <rjw@sisk.pl>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

I have no objections to any of the two patches, but I think we may want to drop
shrink_all_memory() altogether.  Everything should work without it and the
reason I didn't remove it was because I saw a performance regression on one
system without it.  It may not be worth keeping it, though.

Have you done any tests with shrink_all_memory() removed?

Rafael


> ---
>  mm/vmscan.c |   75 +++++++++++++---------------------------------------------
>  1 files changed, 17 insertions(+), 58 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 80e727d..9f28166 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2130,51 +2130,6 @@ unsigned long global_lru_pages(void)
>  
>  #ifdef CONFIG_HIBERNATION
>  /*
> - * Helper function for shrink_all_memory().  Tries to reclaim 'nr_pages' pages
> - * from LRU lists system-wide, for given pass and priority.
> - *
> - * For pass > 3 we also try to shrink the LRU lists that contain a few pages
> - */
> -static void shrink_all_zones(unsigned long nr_pages, int prio,
> -				      int pass, struct scan_control *sc)
> -{
> -	struct zone *zone;
> -	unsigned long nr_reclaimed = 0;
> -
> -	for_each_populated_zone(zone) {
> -		enum lru_list l;
> -
> -		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
> -			continue;
> -
> -		for_each_evictable_lru(l) {
> -			enum zone_stat_item ls = NR_LRU_BASE + l;
> -			unsigned long lru_pages = zone_page_state(zone, ls);
> -
> -			/* For pass = 0, we don't shrink the active list */
> -			if (pass == 0 && (l == LRU_ACTIVE_ANON ||
> -						l == LRU_ACTIVE_FILE))
> -				continue;
> -
> -			zone->lru[l].nr_saved_scan += (lru_pages >> prio) + 1;
> -			if (zone->lru[l].nr_saved_scan >= nr_pages || pass > 3) {
> -				unsigned long nr_to_scan;
> -
> -				zone->lru[l].nr_saved_scan = 0;
> -				nr_to_scan = min(nr_pages, lru_pages);
> -				nr_reclaimed += shrink_list(l, nr_to_scan, zone,
> -								sc, prio);
> -				if (nr_reclaimed >= nr_pages) {
> -					sc->nr_reclaimed += nr_reclaimed;
> -					return;
> -				}
> -			}
> -		}
> -	}
> -	sc->nr_reclaimed += nr_reclaimed;
> -}
> -
> -/*
>   * Try to free `nr_pages' of memory, system-wide, and return the number of
>   * freed pages.
>   *
> @@ -2188,12 +2143,18 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
>  	int pass;
>  	struct reclaim_state reclaim_state;
>  	struct scan_control sc = {
> -		.gfp_mask = GFP_KERNEL,
> +		.gfp_mask = GFP_HIGHUSER_MOVABLE,
> +		.may_swap = 0,
>  		.may_unmap = 0,
>  		.may_writepage = 1,
> +		.swap_cluster_max = SWAP_CLUSTER_MAX,
> +		.nr_to_reclaim = nr_pages,
> +		.swappiness = vm_swappiness,
> +		.order = 0,
>  		.isolate_pages = isolate_pages_global,
> -		.nr_reclaimed = 0,
>  	};
> +	struct zonelist * zonelist = node_zonelist(first_online_node,
> +						   GFP_HIGHUSER_MOVABLE);
>  
>  	current->reclaim_state = &reclaim_state;
>  
> @@ -2215,9 +2176,9 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
>  
>  	/*
>  	 * We try to shrink LRUs in 5 passes:
> -	 * 0 = Reclaim from inactive_list only
> -	 * 1 = Reclaim from active list but don't reclaim mapped
> -	 * 2 = 2nd pass of type 1
> +	 * 0 = Reclaim unmapped pages
> +	 * 1 = 2nd pass of type 0
> +	 * 2 = 3rd pass of type 0
>  	 * 3 = Reclaim mapped (normal reclaim)
>  	 * 4 = 2nd pass of type 3
>  	 */
> @@ -2225,15 +2186,15 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
>  		int prio;
>  
>  		/* Force reclaiming mapped pages in the passes #3 and #4 */
> -		if (pass > 2)
> +		if (pass > 2) {
>  			sc.may_unmap = 1;
> +			sc.may_swap = 1;
> +		}
>  
>  		for (prio = DEF_PRIORITY; prio >= 0; prio--) {
> -			unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
> -
>  			sc.nr_scanned = 0;
> -			sc.swap_cluster_max = nr_to_scan;
> -			shrink_all_zones(nr_to_scan, prio, pass, &sc);
> +
> +			shrink_zones(prio, zonelist, &sc);
>  			if (sc.nr_reclaimed >= nr_pages)
>  				goto out;
>  
> @@ -2243,10 +2204,8 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
>  			sc.nr_reclaimed += reclaim_state.reclaimed_slab;
>  			if (sc.nr_reclaimed >= nr_pages)
>  				goto out;
> -
> -			if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
> -				congestion_wait(BLK_RW_ASYNC, HZ / 10);
>  		}
> +		congestion_wait(BLK_RW_ASYNC, HZ / 10);
>  	}
>  
>  	/*
> 

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Re: [PATCH 2/2] vmscan: kill shrink_all_zones()

[KOSAKI Motohiro]

> >   Throuput comparision
> >   ==============================================
> >   old		2192.10 MB/s
> >   new		2222.22 MB/s
> > 
> >   ok, it's almost same throuput.
> > 
> > Cc: Rafael J. Wysocki <rjw@sisk.pl>
> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> 
> I have no objections to any of the two patches, but I think we may want to drop
> shrink_all_memory() altogether.  Everything should work without it and the
> reason I didn't remove it was because I saw a performance regression on one
> system without it.  It may not be worth keeping it, though.
> 
> Have you done any tests with shrink_all_memory() removed?

Honestly, I haven't try to remvoe shrink_all_memory() at all. then, I don't have any
mesurement data of shrink_all_memory.
Yes, your opinion seems reasonable. I plan to mesure it awhile after. (sorry, I haven't
enough development time in this month)



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Re: [PATCH 1/2] vmscan: separate sc.swap_cluster_max and sc.nr_max_reclaim

[Rik van Riel]

KOSAKI Motohiro wrote:
> Rafael, Can you please review this patch series?
> 
> I found shrink_all_memory() is not fast at all on my numa system.
> I think this patch series fixes it.
> 
> 
> ==============================================================
> Currently, sc.scap_cluster_max has double meanings.
> 
>  1) reclaim batch size as isolate_lru_pages()'s argument
>  2) reclaim baling out thresolds
> 
> The two meanings pretty unrelated. Thus, Let's separate it.
> this patch doesn't change any behavior.
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

Reviewed-by: Rik van Riel <riel@redhat.com>

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