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Commit b44129b3 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
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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.

[akpm@linux-foundation.org: readability tweak]
[kosaki.motohiro@jp.fujitsu.com: set_pgdat_percpu_threshold(): don't use for_each_online_cpu]
Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
Reviewed-by: default avatarChristoph Lameter <cl@linux.com>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 88f5acf8

include/linux/vmstat.h

+6 −4
Original line number Diff line number Diff line
@@ -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

mm/vmscan.c

+17 −2
Original line number Diff line number Diff line
@@ -2448,9 +2448,24 @@ 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);

mm/vmstat.c

+7 −29
Original line number Diff line number Diff line
@@ -83,7 +83,7 @@ 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;
@@ -107,7 +107,7 @@ 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 */
@@ -166,7 +166,7 @@ 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
@@ -185,46 +185,24 @@ 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();

}



/*