mm: hide per-cpu lists in output of show_mem()

This makes show_mem() much less verbose on huge machines.  Instead of huge
and almost useless dump of counters for each per-zone per-cpu lists this
patch prints the sum of these counters for each zone (free_pcp) and size
of per-cpu list for current cpu (local_pcp).

The filter flag SHOW_MEM_PERCPU_LISTS reverts to the old verbose mode.

[akpm@linux-foundation.org: update show_free_areas comment]
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

@@ -1126,6 +1126,7 @@ extern void pagefault_out_of_memory(void);
  * various contexts.
  */
 #define SHOW_MEM_FILTER_NODES		(0x0001u)	/* disallowed nodes */
+#define SHOW_MEM_PERCPU_LISTS		(0x0002u)	/* per-zone per-cpu */
 
 extern void show_free_areas(unsigned int flags);
 extern bool skip_free_areas_node(unsigned int flags, int nid);

mm/page_alloc.c

@@ -3251,25 +3251,37 @@ static void show_migration_types(unsigned char type)
  * Show free area list (used inside shift_scroll-lock stuff)
  * We also calculate the percentage fragmentation. We do this by counting the
  * memory on each free list with the exception of the first item on the list.
- * Suppresses nodes that are not allowed by current's cpuset if
- * SHOW_MEM_FILTER_NODES is passed.
+ *
+ * Bits in @filter:
+ * SHOW_MEM_FILTER_NODES: suppress nodes that are not allowed by current's
+ *   cpuset.
+ * SHOW_MEM_PERCPU_LISTS: display full per-node per-cpu pcp lists
  */
 void show_free_areas(unsigned int filter)
 {
+	unsigned long free_pcp = 0;
 	int cpu;
 	struct zone *zone;
 
 	for_each_populated_zone(zone) {
 		if (skip_free_areas_node(filter, zone_to_nid(zone)))
 			continue;
+
+		if (filter & SHOW_MEM_PERCPU_LISTS) {
 			show_node(zone);
 			printk("%s per-cpu:\n", zone->name);
+		}
 
 		for_each_online_cpu(cpu) {
 			struct per_cpu_pageset *pageset;
 
 			pageset = per_cpu_ptr(zone->pageset, cpu);
 
+			free_pcp += pageset->pcp.count;
+
+			if (!(filter & SHOW_MEM_PERCPU_LISTS))
+				continue;
+
 			printk("CPU %4d: hi:%5d, btch:%4d usd:%4d\n",
 			       cpu, pageset->pcp.high,
 			       pageset->pcp.batch, pageset->pcp.count);
@@ -3278,11 +3290,10 @@ void show_free_areas(unsigned int filter)
 
 	printk("active_anon:%lu inactive_anon:%lu isolated_anon:%lu\n"
 		" active_file:%lu inactive_file:%lu isolated_file:%lu\n"
-		" unevictable:%lu"
-		" dirty:%lu writeback:%lu unstable:%lu\n"
-		" free:%lu slab_reclaimable:%lu slab_unreclaimable:%lu\n"
+		" unevictable:%lu dirty:%lu writeback:%lu unstable:%lu\n"
+		" slab_reclaimable:%lu slab_unreclaimable:%lu\n"
 		" mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
-		" free_cma:%lu\n",
+		" free:%lu free_pcp:%lu free_cma:%lu\n",
 		global_page_state(NR_ACTIVE_ANON),
 		global_page_state(NR_INACTIVE_ANON),
 		global_page_state(NR_ISOLATED_ANON),
@@ -3293,13 +3304,14 @@ void show_free_areas(unsigned int filter)
 		global_page_state(NR_FILE_DIRTY),
 		global_page_state(NR_WRITEBACK),
 		global_page_state(NR_UNSTABLE_NFS),
-		global_page_state(NR_FREE_PAGES),
 		global_page_state(NR_SLAB_RECLAIMABLE),
 		global_page_state(NR_SLAB_UNRECLAIMABLE),
 		global_page_state(NR_FILE_MAPPED),
 		global_page_state(NR_SHMEM),
 		global_page_state(NR_PAGETABLE),
 		global_page_state(NR_BOUNCE),
+		global_page_state(NR_FREE_PAGES),
+		free_pcp,
 		global_page_state(NR_FREE_CMA_PAGES));
 
 	for_each_populated_zone(zone) {
@@ -3307,6 +3319,11 @@ void show_free_areas(unsigned int filter)
 
 		if (skip_free_areas_node(filter, zone_to_nid(zone)))
 			continue;
+
+		free_pcp = 0;
+		for_each_online_cpu(cpu)
+			free_pcp += per_cpu_ptr(zone->pageset, cpu)->pcp.count;
+
 		show_node(zone);
 		printk("%s"
 			" free:%lukB"
@@ -3333,6 +3350,8 @@ void show_free_areas(unsigned int filter)
 			" pagetables:%lukB"
 			" unstable:%lukB"
 			" bounce:%lukB"
+			" free_pcp:%lukB"
+			" local_pcp:%ukB"
 			" free_cma:%lukB"
 			" writeback_tmp:%lukB"
 			" pages_scanned:%lu"
@@ -3364,6 +3383,8 @@ void show_free_areas(unsigned int filter)
 			K(zone_page_state(zone, NR_PAGETABLE)),
 			K(zone_page_state(zone, NR_UNSTABLE_NFS)),
 			K(zone_page_state(zone, NR_BOUNCE)),
+			K(free_pcp),
+			K(this_cpu_read(zone->pageset->pcp.count)),
 			K(zone_page_state(zone, NR_FREE_CMA_PAGES)),
 			K(zone_page_state(zone, NR_WRITEBACK_TEMP)),
 			K(zone_page_state(zone, NR_PAGES_SCANNED)),