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Subject[PATCH 2/2] mm: vmstat: Use a single setter function and callback for adjusting percpu thresholds
Date
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>
---
include/linux/vmstat.h | 10 ++++++----
mm/vmscan.c | 6 ++++--
mm/vmstat.c | 30 ++++++------------------------
3 files changed, 16 insertions(+), 30 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..7966110 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2378,9 +2378,11 @@ static int kswapd(void *p)
*/
if (!sleeping_prematurely(pgdat, order, remaining)) {
trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
- restore_pgdat_percpu_threshold(pgdat);
+ 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 cafcc2d..73661e8 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -81,13 +81,13 @@ EXPORT_SYMBOL(vm_stat);

#ifdef CONFIG_SMP

-static int calculate_pressure_threshold(struct zone *zone)
+int calculate_pressure_threshold(struct zone *zone)
{
return max(1, (int)((high_wmark_pages(zone) - low_wmark_pages(zone) /
num_online_cpus())));
}

-static int calculate_threshold(struct zone *zone)
+int calculate_normal_threshold(struct zone *zone)
{
int threshold;
int mem; /* memory in 128 MB units */
@@ -146,7 +146,7 @@ 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
@@ -165,7 +165,8 @@ 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;
@@ -177,26 +178,7 @@ void reduce_pgdat_percpu_threshold(pg_data_t *pgdat)
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;
- }
-}
-
-void restore_pgdat_percpu_threshold(pg_data_t *pgdat)
-{
- struct zone *zone;
- int cpu;
- int threshold;
- int i;
-
- for (i = 0; i < pgdat->nr_zones; i++) {
- zone = &pgdat->node_zones[i];
- if (!zone->percpu_drift_mark)
- continue;
-
- threshold = calculate_threshold(zone);
+ threshold = calculate_pressure(zone);
for_each_online_cpu(cpu)
per_cpu_ptr(zone->pageset, cpu)->stat_threshold
= threshold;
--
1.7.1


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