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

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
......@@ -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
......
......@@ -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);
......
......@@ -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();
}
/*
......
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