[PATCH 0/3] Follow-up fixes to node-lru series v3

[PATCH 0/3] Follow-up fixes to node-lru series v3

[Mel Gorman]

This is another round of fixups to the node-lru series. The most important
patch is the last one which deals with a highmem accounting issue.

 include/linux/mm_inline.h |  8 ++------
 mm/vmscan.c               | 25 +++++++++++--------------
 2 files changed, 13 insertions(+), 20 deletions(-)

-- 
2.6.4

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[PATCH 1/3] mm, vmscan: Remove redundant check in shrink_zones()

[Mel Gorman]

As pointed out by Minchan Kim, shrink_zones() checks for populated
zones in a zonelist but a zonelist can never contain unpopulated
zones. While it's not related to the node-lru series, it can be
cleaned up now.

Suggested-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 mm/vmscan.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3f06a7a0d135..45344acf52ba 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2605,9 +2605,6 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
 
 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
 					sc->reclaim_idx, sc->nodemask) {
-		if (!populated_zone(zone))
-			continue;
-
 		/*
 		 * Take care memory controller reclaiming has small influence
 		 * to global LRU.
-- 
2.6.4

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[PATCH 2/3] mm, vmscan: Release/reacquire lru_lock on pgdat change

[Mel Gorman]

With node-lru, the locking is based on the pgdat. As Minchan pointed
out, there is an opportunity to reduce LRU lock release/acquire in
check_move_unevictable_pages by only changing lock on a pgdat change.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 mm/vmscan.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 45344acf52ba..a6f31617a08c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3775,24 +3775,24 @@ int page_evictable(struct page *page)
 void check_move_unevictable_pages(struct page **pages, int nr_pages)
 {
 	struct lruvec *lruvec;
-	struct zone *zone = NULL;
+	struct pglist_data *pgdat = NULL;
 	int pgscanned = 0;
 	int pgrescued = 0;
 	int i;
 
 	for (i = 0; i < nr_pages; i++) {
 		struct page *page = pages[i];
-		struct zone *pagezone;
+		struct pglist_data *pagepgdat = page_pgdat(page);
 
 		pgscanned++;
-		pagezone = page_zone(page);
-		if (pagezone != zone) {
-			if (zone)
-				spin_unlock_irq(zone_lru_lock(zone));
-			zone = pagezone;
-			spin_lock_irq(zone_lru_lock(zone));
+		pagepgdat = page_pgdat(page);
+		if (pagepgdat != pgdat) {
+			if (pgdat)
+				spin_unlock_irq(&pgdat->lru_lock);
+			pgdat = pagepgdat;
+			spin_lock_irq(&pgdat->lru_lock);
 		}
-		lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat);
+		lruvec = mem_cgroup_page_lruvec(page, pgdat);
 
 		if (!PageLRU(page) || !PageUnevictable(page))
 			continue;
@@ -3808,10 +3808,10 @@ void check_move_unevictable_pages(struct page **pages, int nr_pages)
 		}
 	}
 
-	if (zone) {
+	if (pgdat) {
 		__count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
 		__count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
-		spin_unlock_irq(zone_lru_lock(zone));
+		spin_unlock_irq(&pgdat->lru_lock);
 	}
 }
 #endif /* CONFIG_SHMEM */
-- 
2.6.4

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[PATCH 3/3] mm, vmstat: remove zone and node double accounting by approximating retries -fix

[Mel Gorman]

As pointed out by Vlastimil, the atomic_add() functions are already assumed
to be able to handle negative numbers. The atomic_sub handling was wrong
anyway but this patch fixes it unconditionally.

This is a fix to the mmotm patch
mm-vmstat-remove-zone-and-node-double-accounting-by-approximating-retries.patch

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 include/linux/mm_inline.h | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index d29237428199..bcc4ed07fa90 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -10,12 +10,8 @@ extern atomic_t highmem_file_pages;
 static inline void acct_highmem_file_pages(int zid, enum lru_list lru,
 							int nr_pages)
 {
-	if (is_highmem_idx(zid) && is_file_lru(lru)) {
-		if (nr_pages > 0)
-			atomic_add(nr_pages, &highmem_file_pages);
-		else
-			atomic_sub(nr_pages, &highmem_file_pages);
-	}
+	if (is_highmem_idx(zid) && is_file_lru(lru))
+		atomic_add(nr_pages, &highmem_file_pages);
 }
 #else
 static inline void acct_highmem_file_pages(int zid, enum lru_list lru,
-- 
2.6.4

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Re: [PATCH 1/3] mm, vmscan: Remove redundant check in shrink_zones()

[Johannes Weiner]

On Mon, Jul 18, 2016 at 03:50:24PM +0100, Mel Gorman wrote:
> As pointed out by Minchan Kim, shrink_zones() checks for populated
> zones in a zonelist but a zonelist can never contain unpopulated
> zones. While it's not related to the node-lru series, it can be
> cleaned up now.
> 
> Suggested-by: Minchan Kim <minchan@kernel.org>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

Ha, I didn't know that. But yeah, the zonelist building code excludes
unpopulated zones from the start. Neat.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

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Re: [PATCH 2/3] mm, vmscan: Release/reacquire lru_lock on pgdat change

[Johannes Weiner]

On Mon, Jul 18, 2016 at 03:50:25PM +0100, Mel Gorman wrote:
> With node-lru, the locking is based on the pgdat. As Minchan pointed
> out, there is an opportunity to reduce LRU lock release/acquire in
> check_move_unevictable_pages by only changing lock on a pgdat change.
> 
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

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Re: [PATCH 3/3] mm, vmstat: remove zone and node double accounting by approximating retries -fix

[Johannes Weiner]

On Mon, Jul 18, 2016 at 03:50:26PM +0100, Mel Gorman wrote:
> As pointed out by Vlastimil, the atomic_add() functions are already assumed
> to be able to handle negative numbers. The atomic_sub handling was wrong
> anyway but this patch fixes it unconditionally.
> 
> This is a fix to the mmotm patch
> mm-vmstat-remove-zone-and-node-double-accounting-by-approximating-retries.patch
> 
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

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Re: [PATCH 0/3] Follow-up fixes to node-lru series v3

[Johannes Weiner]

The v3 is a bit misleading. It's on top of, not instead of, the v2
series with the same name sent out previously. We need both series.

On Mon, Jul 18, 2016 at 03:50:23PM +0100, Mel Gorman wrote:
> This is another round of fixups to the node-lru series. The most important
> patch is the last one which deals with a highmem accounting issue.
> 
>  include/linux/mm_inline.h |  8 ++------
>  mm/vmscan.c               | 25 +++++++++++--------------
>  2 files changed, 13 insertions(+), 20 deletions(-)

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Re: [PATCH 1/3] mm, vmscan: Remove redundant check in shrink_zones()

[Minchan Kim]

On Mon, Jul 18, 2016 at 03:50:24PM +0100, Mel Gorman wrote:
> As pointed out by Minchan Kim, shrink_zones() checks for populated
> zones in a zonelist but a zonelist can never contain unpopulated
> zones. While it's not related to the node-lru series, it can be
> cleaned up now.
> 
> Suggested-by: Minchan Kim <minchan@kernel.org>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Minchan Kim <minchan@kernel.org>

Thanks.

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Re: [PATCH 2/3] mm, vmscan: Release/reacquire lru_lock on pgdat change

[Minchan Kim]

On Mon, Jul 18, 2016 at 03:50:25PM +0100, Mel Gorman wrote:
> With node-lru, the locking is based on the pgdat. As Minchan pointed
> out, there is an opportunity to reduce LRU lock release/acquire in
> check_move_unevictable_pages by only changing lock on a pgdat change.
> 
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> ---
>  mm/vmscan.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 45344acf52ba..a6f31617a08c 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3775,24 +3775,24 @@ int page_evictable(struct page *page)
>  void check_move_unevictable_pages(struct page **pages, int nr_pages)
>  {
>  	struct lruvec *lruvec;
> -	struct zone *zone = NULL;
> +	struct pglist_data *pgdat = NULL;
>  	int pgscanned = 0;
>  	int pgrescued = 0;
>  	int i;
>  
>  	for (i = 0; i < nr_pages; i++) {
>  		struct page *page = pages[i];
> -		struct zone *pagezone;
> +		struct pglist_data *pagepgdat = page_pgdat(page);

No need to initialize in here.

>  
>  		pgscanned++;
> -		pagezone = page_zone(page);
> -		if (pagezone != zone) {
> -			if (zone)
> -				spin_unlock_irq(zone_lru_lock(zone));
> -			zone = pagezone;
> -			spin_lock_irq(zone_lru_lock(zone));
> +		pagepgdat = page_pgdat(page);

Double initialize. Please remove either one.

> +		if (pagepgdat != pgdat) {
> +			if (pgdat)
> +				spin_unlock_irq(&pgdat->lru_lock);
> +			pgdat = pagepgdat;
> +			spin_lock_irq(&pgdat->lru_lock);
>  		}
> -		lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat);
> +		lruvec = mem_cgroup_page_lruvec(page, pgdat);
>  
>  		if (!PageLRU(page) || !PageUnevictable(page))
>  			continue;
> @@ -3808,10 +3808,10 @@ void check_move_unevictable_pages(struct page **pages, int nr_pages)
>  		}
>  	}
>  
> -	if (zone) {
> +	if (pgdat) {
>  		__count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
>  		__count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
> -		spin_unlock_irq(zone_lru_lock(zone));
> +		spin_unlock_irq(&pgdat->lru_lock);
>  	}
>  }
>  #endif /* CONFIG_SHMEM */
> -- 
> 2.6.4
> 

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Re: [PATCH 3/3] mm, vmstat: remove zone and node double accounting by approximating retries -fix

[Minchan Kim]

On Mon, Jul 18, 2016 at 03:50:26PM +0100, Mel Gorman wrote:
> As pointed out by Vlastimil, the atomic_add() functions are already assumed
> to be able to handle negative numbers. The atomic_sub handling was wrong
> anyway but this patch fixes it unconditionally.
> 
> This is a fix to the mmotm patch
> mm-vmstat-remove-zone-and-node-double-accounting-by-approximating-retries.patch
> 
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Minchan Kim <minchan@kernel.org>

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