kswapd fixes from mmotm

(queuing them here since it's unclear if they'll go into .37 or wait for
 .38)

1 files changed, 167 insertions, 0 deletions

diff --git a/mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds.patch b/mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds.patch
new file mode 100644
index 000000000..058b1399a
--- /dev/null
+++ b/mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds.patch
@@ -0,0 +1,167 @@
+From 82e3d4969144377d13da97d511e849e8cf3e6dcc Mon Sep 17 00:00:00 2001
+From: Mel Gorman <mel@csn.ul.ie>
+Date: Wed, 24 Nov 2010 22:24:24 -0500
+Subject: [PATCH 2/2] mm: vmstat: Use a single setter function and callback for adjusting percpu thresholds
+
+reduce_pgdat_percpu_threshold() and restore_pgdat_percpu_threshold() exist
+to adjust the per-cpu vmstat thresholds while kswapd is awake to avoid
+errors due to counter drift.  The functions duplicate some code so this
+patch replaces them with a single set_pgdat_percpu_threshold() that takes
+a callback function to calculate the desired threshold as a parameter.
+
+Signed-off-by: Mel Gorman <mel@csn.ul.ie>
+Reviewed-by: Christoph Lameter <cl@linux.com>
+Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+[the various mmotm patches updating this were rolled up. --kyle]
+[[http://userweb.kernel.org/~akpm/mmotm/broken-out/mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-fix-set_pgdat_percpu_threshold-dont-use-for_each_online_cpu.patch]]
+---
+ include/linux/vmstat.h |   10 ++++++----
+ mm/vmscan.c            |   19 +++++++++++++++++--
+ mm/vmstat.c            |   36 +++++++-----------------------------
+ 3 files changed, 30 insertions(+), 35 deletions(-)
+
+diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
+index e4cc21c..833e676 100644
+--- a/include/linux/vmstat.h
++++ b/include/linux/vmstat.h
+@@ -254,8 +254,11 @@ extern void dec_zone_state(struct zone *, enum zone_stat_item);
+ extern void __dec_zone_state(struct zone *, enum zone_stat_item);
+ 
+ void refresh_cpu_vm_stats(int);
+-void reduce_pgdat_percpu_threshold(pg_data_t *pgdat);
+-void restore_pgdat_percpu_threshold(pg_data_t *pgdat);
++
++int calculate_pressure_threshold(struct zone *zone);
++int calculate_normal_threshold(struct zone *zone);
++void set_pgdat_percpu_threshold(pg_data_t *pgdat,
++				int (*calculate_pressure)(struct zone *));
+ #else /* CONFIG_SMP */
+ 
+ /*
+@@ -300,8 +303,7 @@ static inline void __dec_zone_page_state(struct page *page,
+ #define dec_zone_page_state __dec_zone_page_state
+ #define mod_zone_page_state __mod_zone_page_state
+ 
+-static inline void reduce_pgdat_percpu_threshold(pg_data_t *pgdat) { }
+-static inline void restore_pgdat_percpu_threshold(pg_data_t *pgdat) { }
++#define set_pgdat_percpu_threshold(pgdat, callback) { }
+ 
+ static inline void refresh_cpu_vm_stats(int cpu) { }
+ #endif
+diff --git a/mm/vmscan.c b/mm/vmscan.c
+index 3e71cb1..ba39948 100644
+--- a/mm/vmscan.c
++++ b/mm/vmscan.c
+@@ -2378,9 +2378,24 @@ static int kswapd(void *p)
+ 				 */
+ 				if (!sleeping_prematurely(pgdat, order, remaining)) {
+ 					trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
+-					restore_pgdat_percpu_threshold(pgdat);
++
++					/*
++					 * vmstat counters are not perfectly
++					 * accurate and the estimated value
++					 * for counters such as NR_FREE_PAGES
++					 * can deviate from the true value by
++					 * nr_online_cpus * threshold. To
++					 * avoid the zone watermarks being
++					 * breached while under pressure, we
++					 * reduce the per-cpu vmstat threshold
++					 * while kswapd is awake and restore
++					 * them before going back to sleep.
++					 */
++					set_pgdat_percpu_threshold(pgdat,
++						calculate_normal_threshold);
+ 					schedule();
+-					reduce_pgdat_percpu_threshold(pgdat);
++					set_pgdat_percpu_threshold(pgdat,
++						calculate_pressure_threshold);
+ 				} else {
+ 					if (remaining)
+ 						count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
+diff --git a/mm/vmstat.c b/mm/vmstat.c
+index 4d7faeb..511c2c0 100644
+--- a/mm/vmstat.c
++++ b/mm/vmstat.c
+@@ -81,7 +81,7 @@ EXPORT_SYMBOL(vm_stat);
+ 
+ #ifdef CONFIG_SMP
+ 
+-static int calculate_pressure_threshold(struct zone *zone)
++int calculate_pressure_threshold(struct zone *zone)
+ {
+ 	int threshold;
+ 	int watermark_distance;
+@@ -105,7 +105,7 @@ static int calculate_pressure_threshold(struct zone *zone)
+ 	return threshold;
+ }
+ 
+-static int calculate_threshold(struct zone *zone)
++int calculate_normal_threshold(struct zone *zone)
+ {
+ 	int threshold;
+ 	int mem;	/* memory in 128 MB units */
+@@ -164,7 +164,7 @@ static void refresh_zone_stat_thresholds(void)
+ 	for_each_populated_zone(zone) {
+ 		unsigned long max_drift, tolerate_drift;
+ 
+-		threshold = calculate_threshold(zone);
++		threshold = calculate_normal_threshold(zone);
+ 
+ 		for_each_online_cpu(cpu)
+ 			per_cpu_ptr(zone->pageset, cpu)->stat_threshold
+@@ -183,46 +183,24 @@ static void refresh_zone_stat_thresholds(void)
+ 	}
+ }
+ 
+-void reduce_pgdat_percpu_threshold(pg_data_t *pgdat)
++void set_pgdat_percpu_threshold(pg_data_t *pgdat,
++				int (*calculate_pressure)(struct zone *))
+ {
+ 	struct zone *zone;
+ 	int cpu;
+ 	int threshold;
+ 	int i;
+ 
+-	get_online_cpus();
+-	for (i = 0; i < pgdat->nr_zones; i++) {
+-		zone = &pgdat->node_zones[i];
+-		if (!zone->percpu_drift_mark)
+-			continue;
+-
+-		threshold = calculate_pressure_threshold(zone);
+-		for_each_online_cpu(cpu)
+-			per_cpu_ptr(zone->pageset, cpu)->stat_threshold
+-							= threshold;
+-	}
+-	put_online_cpus();
+-}
+-
+-void restore_pgdat_percpu_threshold(pg_data_t *pgdat)
+-{
+-	struct zone *zone;
+-	int cpu;
+-	int threshold;
+-	int i;
+-
+-	get_online_cpus();
+ 	for (i = 0; i < pgdat->nr_zones; i++) {
+ 		zone = &pgdat->node_zones[i];
+ 		if (!zone->percpu_drift_mark)
+ 			continue;
+ 
+-		threshold = calculate_threshold(zone);
+-		for_each_online_cpu(cpu)
++		threshold = (*calculate_pressure)(zone);
++		for_each_possible_cpu(cpu)
+ 			per_cpu_ptr(zone->pageset, cpu)->stat_threshold
+ 							= threshold;
+ 	}
+-	put_online_cpus();
+ }
+ 
+ /*
+-- 
+1.7.3.2
+