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