mm: change the call sites of numa statistics items

Patch series "Separate NUMA statistics from zone statistics", v2.

Each page allocation updates a set of per-zone statistics with a call to
zone_statistics().  As discussed in 2017 MM summit, these are a
substantial source of overhead in the page allocator and are very rarely
consumed.  This significant overhead in cache bouncing caused by zone
counters (NUMA associated counters) update in parallel in multi-threaded
page allocation (pointed out by Dave Hansen).

A link to the MM summit slides:
  http://people.netfilter.org/hawk/presentations/MM-summit2017/MM-summit2017-JesperBrouer.pdf

To mitigate this overhead, this patchset separates NUMA statistics from
zone statistics framework, and update NUMA counter threshold to a fixed
size of MAX_U16 - 2, as a small threshold greatly increases the update
frequency of the global counter from local per cpu counter (suggested by
Ying Huang).  The rationality is that these statistics counters don't
need to be read often, unlike other VM counters, so it's not a problem
to use a large threshold and make readers more expensive.

With this patchset, we see 31.3% drop of CPU cycles(537-->369, see
below) for per single page allocation and reclaim on Jesper's
page_bench03 benchmark.  Meanwhile, this patchset keeps the same style
of virtual memory statistics with little end-user-visible effects (only
move the numa stats to show behind zone page stats, see the first patch
for details).

I did an experiment of single page allocation and reclaim concurrently
using Jesper's page_bench03 benchmark on a 2-Socket Broadwell-based
server (88 processors with 126G memory) with different size of threshold
of pcp counter.

Benchmark provided by Jesper D Brouer(increase loop times to 10000000):
  https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/mm/bench

   Threshold   CPU cycles    Throughput(88 threads)
      32        799         241760478
      64        640         301628829
      125       537         358906028 <==> system by default
      256       468         412397590
      512       428         450550704
      4096      399         482520943
      20000     394         489009617
      30000     395         488017817
      65533     369(-31.3%) 521661345(+45.3%) <==> with this patchset
      N/A       342(-36.3%) 562900157(+56.8%) <==> disable zone_statistics

This patch (of 3):

In this patch, NUMA statistics is separated from zone statistics
framework, all the call sites of NUMA stats are changed to use
numa-stats-specific functions, it does not have any functionality change
except that the number of NUMA stats is shown behind zone page stats
when users *read* the zone info.

E.g. cat /proc/zoneinfo
    ***Base***                           ***With this patch***
nr_free_pages 3976                         nr_free_pages 3976
nr_zone_inactive_anon 0                    nr_zone_inactive_anon 0
nr_zone_active_anon 0                      nr_zone_active_anon 0
nr_zone_inactive_file 0                    nr_zone_inactive_file 0
nr_zone_active_file 0                      nr_zone_active_file 0
nr_zone_unevictable 0                      nr_zone_unevictable 0
nr_zone_write_pending 0                    nr_zone_write_pending 0
nr_mlock     0                             nr_mlock     0
nr_page_table_pages 0                      nr_page_table_pages 0
nr_kernel_stack 0                          nr_kernel_stack 0
nr_bounce    0                             nr_bounce    0
nr_zspages   0                             nr_zspages   0
numa_hit 0                                *nr_free_cma  0*
numa_miss 0                                numa_hit     0
numa_foreign 0                             numa_miss    0
numa_interleave 0                          numa_foreign 0
numa_local   0                             numa_interleave 0
numa_other   0                             numa_local   0
*nr_free_cma 0*                            numa_other 0
    ...                                        ...
vm stats threshold: 10                     vm stats threshold: 10
    ...                                        ...

The next patch updates the numa stats counter size and threshold.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1503568801-21305-2-git-send-email-kemi.wang@intel.com
Signed-off-by: Kemi Wang <kemi.wang@intel.com>
Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Ying Huang <ying.huang@intel.com>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 160 insertions, 11 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a9add06fe768..45583cd8dd56 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2741,18 +2741,18 @@ int __isolate_free_page(struct page *page, unsigned int order)
 static inline void zone_statistics(struct zone *preferred_zone, struct zone *z)
 {
 #ifdef CONFIG_NUMA
-	enum zone_stat_item local_stat = NUMA_LOCAL;
+	enum numa_stat_item local_stat = NUMA_LOCAL;
 
 	if (z->node != numa_node_id())
 		local_stat = NUMA_OTHER;
 
 	if (z->node == preferred_zone->node)
-		__inc_zone_state(z, NUMA_HIT);
+		__inc_numa_state(z, NUMA_HIT);
 	else {
-		__inc_zone_state(z, NUMA_MISS);
-		__inc_zone_state(preferred_zone, NUMA_FOREIGN);
+		__inc_numa_state(z, NUMA_MISS);
+		__inc_numa_state(preferred_zone, NUMA_FOREIGN);
 	}
-	__inc_zone_state(z, local_stat);
+	__inc_numa_state(z, local_stat);
 #endif
 }
 
diff --git a/mm/vmstat.c b/mm/vmstat.c
index c7e4b8458023..daea02833e2e 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -87,8 +87,10 @@ void vm_events_fold_cpu(int cpu)
  * vm_stat contains the global counters
  */
 atomic_long_t vm_zone_stat[NR_VM_ZONE_STAT_ITEMS] __cacheline_aligned_in_smp;
+atomic_long_t vm_numa_stat[NR_VM_NUMA_STAT_ITEMS] __cacheline_aligned_in_smp;
 atomic_long_t vm_node_stat[NR_VM_NODE_STAT_ITEMS] __cacheline_aligned_in_smp;
 EXPORT_SYMBOL(vm_zone_stat);
+EXPORT_SYMBOL(vm_numa_stat);
 EXPORT_SYMBOL(vm_node_stat);
 
 #ifdef CONFIG_SMP
@@ -192,7 +194,10 @@ void refresh_zone_stat_thresholds(void)
 
 			per_cpu_ptr(zone->pageset, cpu)->stat_threshold
 							= threshold;
-
+#ifdef CONFIG_NUMA
+			per_cpu_ptr(zone->pageset, cpu)->numa_stat_threshold
+							= threshold;
+#endif
 			/* Base nodestat threshold on the largest populated zone. */
 			pgdat_threshold = per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold;
 			per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold
@@ -226,9 +231,14 @@ void set_pgdat_percpu_threshold(pg_data_t *pgdat,
 			continue;
 
 		threshold = (*calculate_pressure)(zone);
-		for_each_online_cpu(cpu)
+		for_each_online_cpu(cpu) {
 			per_cpu_ptr(zone->pageset, cpu)->stat_threshold
 							= threshold;
+#ifdef CONFIG_NUMA
+			per_cpu_ptr(zone->pageset, cpu)->numa_stat_threshold
+							= threshold;
+#endif
+		}
 	}
 }
 
@@ -604,6 +614,32 @@ EXPORT_SYMBOL(dec_node_page_state);
  * Fold a differential into the global counters.
  * Returns the number of counters updated.
  */
+#ifdef CONFIG_NUMA
+static int fold_diff(int *zone_diff, int *numa_diff, int *node_diff)
+{
+	int i;
+	int changes = 0;
+
+	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
+		if (zone_diff[i]) {
+			atomic_long_add(zone_diff[i], &vm_zone_stat[i]);
+			changes++;
+	}
+
+	for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++)
+		if (numa_diff[i]) {
+			atomic_long_add(numa_diff[i], &vm_numa_stat[i]);
+			changes++;
+	}
+
+	for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
+		if (node_diff[i]) {
+			atomic_long_add(node_diff[i], &vm_node_stat[i]);
+			changes++;
+	}
+	return changes;
+}
+#else
 static int fold_diff(int *zone_diff, int *node_diff)
 {
 	int i;
@@ -622,6 +658,7 @@ static int fold_diff(int *zone_diff, int *node_diff)
 	}
 	return changes;
 }
+#endif /* CONFIG_NUMA */
 
 /*
  * Update the zone counters for the current cpu.
@@ -645,6 +682,9 @@ static int refresh_cpu_vm_stats(bool do_pagesets)
 	struct zone *zone;
 	int i;
 	int global_zone_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
+#ifdef CONFIG_NUMA
+	int global_numa_diff[NR_VM_NUMA_STAT_ITEMS] = { 0, };
+#endif
 	int global_node_diff[NR_VM_NODE_STAT_ITEMS] = { 0, };
 	int changes = 0;
 
@@ -666,6 +706,18 @@ static int refresh_cpu_vm_stats(bool do_pagesets)
 			}
 		}
 #ifdef CONFIG_NUMA
+		for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++) {
+			int v;
+
+			v = this_cpu_xchg(p->vm_numa_stat_diff[i], 0);
+			if (v) {
+
+				atomic_long_add(v, &zone->vm_numa_stat[i]);
+				global_numa_diff[i] += v;
+				__this_cpu_write(p->expire, 3);
+			}
+		}
+
 		if (do_pagesets) {
 			cond_resched();
 			/*
@@ -712,7 +764,12 @@ static int refresh_cpu_vm_stats(bool do_pagesets)
 		}
 	}
 
+#ifdef CONFIG_NUMA
+	changes += fold_diff(global_zone_diff, global_numa_diff,
+			     global_node_diff);
+#else
 	changes += fold_diff(global_zone_diff, global_node_diff);
+#endif
 	return changes;
 }
 
@@ -727,6 +784,9 @@ void cpu_vm_stats_fold(int cpu)
 	struct zone *zone;
 	int i;
 	int global_zone_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
+#ifdef CONFIG_NUMA
+	int global_numa_diff[NR_VM_NUMA_STAT_ITEMS] = { 0, };
+#endif
 	int global_node_diff[NR_VM_NODE_STAT_ITEMS] = { 0, };
 
 	for_each_populated_zone(zone) {
@@ -743,6 +803,18 @@ void cpu_vm_stats_fold(int cpu)
 				atomic_long_add(v, &zone->vm_stat[i]);
 				global_zone_diff[i] += v;
 			}
+
+#ifdef CONFIG_NUMA
+		for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++)
+			if (p->vm_numa_stat_diff[i]) {
+				int v;
+
+				v = p->vm_numa_stat_diff[i];
+				p->vm_numa_stat_diff[i] = 0;
+				atomic_long_add(v, &zone->vm_numa_stat[i]);
+				global_numa_diff[i] += v;
+			}
+#endif
 	}
 
 	for_each_online_pgdat(pgdat) {
@@ -761,7 +833,11 @@ void cpu_vm_stats_fold(int cpu)
 			}
 	}
 
+#ifdef CONFIG_NUMA
+	fold_diff(global_zone_diff, global_numa_diff, global_node_diff);
+#else
 	fold_diff(global_zone_diff, global_node_diff);
+#endif
 }
 
 /*
@@ -779,10 +855,38 @@ void drain_zonestat(struct zone *zone, struct per_cpu_pageset *pset)
 			atomic_long_add(v, &zone->vm_stat[i]);
 			atomic_long_add(v, &vm_zone_stat[i]);
 		}
+
+#ifdef CONFIG_NUMA
+	for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++)
+		if (pset->vm_numa_stat_diff[i]) {
+			int v = pset->vm_numa_stat_diff[i];
+
+			pset->vm_numa_stat_diff[i] = 0;
+			atomic_long_add(v, &zone->vm_numa_stat[i]);
+			atomic_long_add(v, &vm_numa_stat[i]);
+		}
+#endif
 }
 #endif
 
 #ifdef CONFIG_NUMA
+void __inc_numa_state(struct zone *zone,
+				 enum numa_stat_item item)
+{
+	struct per_cpu_pageset __percpu *pcp = zone->pageset;
+	s8 __percpu *p = pcp->vm_numa_stat_diff + item;
+	s8 v, t;
+
+	v = __this_cpu_inc_return(*p);
+	t = __this_cpu_read(pcp->numa_stat_threshold);
+	if (unlikely(v > t)) {
+		s8 overstep = t >> 1;
+
+		zone_numa_state_add(v + overstep, zone, item);
+		__this_cpu_write(*p, -overstep);
+	}
+}
+
 /*
  * Determine the per node value of a stat item. This function
  * is called frequently in a NUMA machine, so try to be as
@@ -801,6 +905,19 @@ unsigned long sum_zone_node_page_state(int node,
 	return count;
 }
 
+unsigned long sum_zone_numa_state(int node,
+				 enum numa_stat_item item)
+{
+	struct zone *zones = NODE_DATA(node)->node_zones;
+	int i;
+	unsigned long count = 0;
+
+	for (i = 0; i < MAX_NR_ZONES; i++)
+		count += zone_numa_state(zones + i, item);
+
+	return count;
+}
+
 /*
  * Determine the per node value of a stat item.
  */
@@ -937,6 +1054,9 @@ const char * const vmstat_text[] = {
 #if IS_ENABLED(CONFIG_ZSMALLOC)
 	"nr_zspages",
 #endif
+	"nr_free_cma",
+
+	/* enum numa_stat_item counters */
 #ifdef CONFIG_NUMA
 	"numa_hit",
 	"numa_miss",
@@ -945,7 +1065,6 @@ const char * const vmstat_text[] = {
 	"numa_local",
 	"numa_other",
 #endif
-	"nr_free_cma",
 
 	/* Node-based counters */
 	"nr_inactive_anon",
@@ -1106,7 +1225,6 @@ const char * const vmstat_text[] = {
 };
 #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA */
 
-
 #if (defined(CONFIG_DEBUG_FS) && defined(CONFIG_COMPACTION)) || \
      defined(CONFIG_PROC_FS)
 static void *frag_start(struct seq_file *m, loff_t *pos)
@@ -1384,7 +1502,8 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 		seq_printf(m, "\n  per-node stats");
 		for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
 			seq_printf(m, "\n      %-12s %lu",
-				vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
+				vmstat_text[i + NR_VM_ZONE_STAT_ITEMS +
+				NR_VM_NUMA_STAT_ITEMS],
 				node_page_state(pgdat, i));
 		}
 	}
@@ -1421,6 +1540,13 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 		seq_printf(m, "\n      %-12s %lu", vmstat_text[i],
 				zone_page_state(zone, i));
 
+#ifdef CONFIG_NUMA
+	for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++)
+		seq_printf(m, "\n      %-12s %lu",
+				vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
+				zone_numa_state(zone, i));
+#endif
+
 	seq_printf(m, "\n  pagesets");
 	for_each_online_cpu(i) {
 		struct per_cpu_pageset *pageset;
@@ -1497,6 +1623,7 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
 	if (*pos >= ARRAY_SIZE(vmstat_text))
 		return NULL;
 	stat_items_size = NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long) +
+			  NR_VM_NUMA_STAT_ITEMS * sizeof(unsigned long) +
 			  NR_VM_NODE_STAT_ITEMS * sizeof(unsigned long) +
 			  NR_VM_WRITEBACK_STAT_ITEMS * sizeof(unsigned long);
 
@@ -1512,6 +1639,12 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
 		v[i] = global_zone_page_state(i);
 	v += NR_VM_ZONE_STAT_ITEMS;
 
+#ifdef CONFIG_NUMA
+	for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++)
+		v[i] = global_numa_state(i);
+	v += NR_VM_NUMA_STAT_ITEMS;
+#endif
+
 	for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
 		v[i] = global_node_page_state(i);
 	v += NR_VM_NODE_STAT_ITEMS;
@@ -1613,6 +1746,16 @@ int vmstat_refresh(struct ctl_table *table, int write,
 			err = -EINVAL;
 		}
 	}
+#ifdef CONFIG_NUMA
+	for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++) {
+		val = atomic_long_read(&vm_numa_stat[i]);
+		if (val < 0) {
+			pr_warn("%s: %s %ld\n",
+				__func__, vmstat_text[i + NR_VM_ZONE_STAT_ITEMS], val);
+			err = -EINVAL;
+		}
+	}
+#endif
 	if (err)
 		return err;
 	if (write)
@@ -1654,13 +1797,19 @@ static bool need_update(int cpu)
 		struct per_cpu_pageset *p = per_cpu_ptr(zone->pageset, cpu);
 
 		BUILD_BUG_ON(sizeof(p->vm_stat_diff[0]) != 1);
+#ifdef CONFIG_NUMA
+		BUILD_BUG_ON(sizeof(p->vm_numa_stat_diff[0]) != 1);
+#endif
 		/*
 		 * The fast way of checking if there are any vmstat diffs.
 		 * This works because the diffs are byte sized items.
 		 */
 		if (memchr_inv(p->vm_stat_diff, 0, NR_VM_ZONE_STAT_ITEMS))
 			return true;
-
+#ifdef CONFIG_NUMA
+		if (memchr_inv(p->vm_numa_stat_diff, 0, NR_VM_NUMA_STAT_ITEMS))
+			return true;
+#endif
 	}
 	return false;
 }