vmstat.c revision 468fd62ed9090ccbe872489df5d0d099510df4b5 
1/*
2 *  linux/mm/vmstat.c
3 *
4 *  Manages VM statistics
5 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
6 *
7 *  zoned VM statistics
8 *  Copyright (C) 2006 Silicon Graphics, Inc.,
9 *		Christoph Lameter <christoph@lameter.com>
10 */
11
12#include <linux/mm.h>
13#include <linux/err.h>
14#include <linux/module.h>
15#include <linux/cpu.h>
16#include <linux/sched.h>
17
18#ifdef CONFIG_VM_EVENT_COUNTERS
19DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
20EXPORT_PER_CPU_SYMBOL(vm_event_states);
21
22static void sum_vm_events(unsigned long *ret, cpumask_t *cpumask)
23{
24	int cpu;
25	int i;
26
27	memset(ret, 0, NR_VM_EVENT_ITEMS * sizeof(unsigned long));
28
29	for_each_cpu_mask(cpu, *cpumask) {
30		struct vm_event_state *this = &per_cpu(vm_event_states, cpu);
31
32		for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
33			ret[i] += this->event[i];
34	}
35}
36
37/*
38 * Accumulate the vm event counters across all CPUs.
39 * The result is unavoidably approximate - it can change
40 * during and after execution of this function.
41*/
42void all_vm_events(unsigned long *ret)
43{
44	sum_vm_events(ret, &cpu_online_map);
45}
46EXPORT_SYMBOL_GPL(all_vm_events);
47
48#ifdef CONFIG_HOTPLUG
49/*
50 * Fold the foreign cpu events into our own.
51 *
52 * This is adding to the events on one processor
53 * but keeps the global counts constant.
54 */
55void vm_events_fold_cpu(int cpu)
56{
57	struct vm_event_state *fold_state = &per_cpu(vm_event_states, cpu);
58	int i;
59
60	for (i = 0; i < NR_VM_EVENT_ITEMS; i++) {
61		count_vm_events(i, fold_state->event[i]);
62		fold_state->event[i] = 0;
63	}
64}
65#endif /* CONFIG_HOTPLUG */
66
67#endif /* CONFIG_VM_EVENT_COUNTERS */
68
69/*
70 * Manage combined zone based / global counters
71 *
72 * vm_stat contains the global counters
73 */
74atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
75EXPORT_SYMBOL(vm_stat);
76
77#ifdef CONFIG_SMP
78
79static int calculate_threshold(struct zone *zone)
80{
81	int threshold;
82	int mem;	/* memory in 128 MB units */
83
84	/*
85	 * The threshold scales with the number of processors and the amount
86	 * of memory per zone. More memory means that we can defer updates for
87	 * longer, more processors could lead to more contention.
88 	 * fls() is used to have a cheap way of logarithmic scaling.
89	 *
90	 * Some sample thresholds:
91	 *
92	 * Threshold	Processors	(fls)	Zonesize	fls(mem+1)
93	 * ------------------------------------------------------------------
94	 * 8		1		1	0.9-1 GB	4
95	 * 16		2		2	0.9-1 GB	4
96	 * 20 		2		2	1-2 GB		5
97	 * 24		2		2	2-4 GB		6
98	 * 28		2		2	4-8 GB		7
99	 * 32		2		2	8-16 GB		8
100	 * 4		2		2	<128M		1
101	 * 30		4		3	2-4 GB		5
102	 * 48		4		3	8-16 GB		8
103	 * 32		8		4	1-2 GB		4
104	 * 32		8		4	0.9-1GB		4
105	 * 10		16		5	<128M		1
106	 * 40		16		5	900M		4
107	 * 70		64		7	2-4 GB		5
108	 * 84		64		7	4-8 GB		6
109	 * 108		512		9	4-8 GB		6
110	 * 125		1024		10	8-16 GB		8
111	 * 125		1024		10	16-32 GB	9
112	 */
113
114	mem = zone->present_pages >> (27 - PAGE_SHIFT);
115
116	threshold = 2 * fls(num_online_cpus()) * (1 + fls(mem));
117
118	/*
119	 * Maximum threshold is 125
120	 */
121	threshold = min(125, threshold);
122
123	return threshold;
124}
125
126/*
127 * Refresh the thresholds for each zone.
128 */
129static void refresh_zone_stat_thresholds(void)
130{
131	struct zone *zone;
132	int cpu;
133	int threshold;
134
135	for_each_zone(zone) {
136
137		if (!zone->present_pages)
138			continue;
139
140		threshold = calculate_threshold(zone);
141
142		for_each_online_cpu(cpu)
143			zone_pcp(zone, cpu)->stat_threshold = threshold;
144	}
145}
146
147/*
148 * For use when we know that interrupts are disabled.
149 */
150void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
151				int delta)
152{
153	struct per_cpu_pageset *pcp = zone_pcp(zone, smp_processor_id());
154	s8 *p = pcp->vm_stat_diff + item;
155	long x;
156
157	x = delta + *p;
158
159	if (unlikely(x > pcp->stat_threshold || x < -pcp->stat_threshold)) {
160		zone_page_state_add(x, zone, item);
161		x = 0;
162	}
163	*p = x;
164}
165EXPORT_SYMBOL(__mod_zone_page_state);
166
167/*
168 * For an unknown interrupt state
169 */
170void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
171					int delta)
172{
173	unsigned long flags;
174
175	local_irq_save(flags);
176	__mod_zone_page_state(zone, item, delta);
177	local_irq_restore(flags);
178}
179EXPORT_SYMBOL(mod_zone_page_state);
180
181/*
182 * Optimized increment and decrement functions.
183 *
184 * These are only for a single page and therefore can take a struct page *
185 * argument instead of struct zone *. This allows the inclusion of the code
186 * generated for page_zone(page) into the optimized functions.
187 *
188 * No overflow check is necessary and therefore the differential can be
189 * incremented or decremented in place which may allow the compilers to
190 * generate better code.
191 * The increment or decrement is known and therefore one boundary check can
192 * be omitted.
193 *
194 * NOTE: These functions are very performance sensitive. Change only
195 * with care.
196 *
197 * Some processors have inc/dec instructions that are atomic vs an interrupt.
198 * However, the code must first determine the differential location in a zone
199 * based on the processor number and then inc/dec the counter. There is no
200 * guarantee without disabling preemption that the processor will not change
201 * in between and therefore the atomicity vs. interrupt cannot be exploited
202 * in a useful way here.
203 */
204void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
205{
206	struct per_cpu_pageset *pcp = zone_pcp(zone, smp_processor_id());
207	s8 *p = pcp->vm_stat_diff + item;
208
209	(*p)++;
210
211	if (unlikely(*p > pcp->stat_threshold)) {
212		int overstep = pcp->stat_threshold / 2;
213
214		zone_page_state_add(*p + overstep, zone, item);
215		*p = -overstep;
216	}
217}
218
219void __inc_zone_page_state(struct page *page, enum zone_stat_item item)
220{
221	__inc_zone_state(page_zone(page), item);
222}
223EXPORT_SYMBOL(__inc_zone_page_state);
224
225void __dec_zone_state(struct zone *zone, enum zone_stat_item item)
226{
227	struct per_cpu_pageset *pcp = zone_pcp(zone, smp_processor_id());
228	s8 *p = pcp->vm_stat_diff + item;
229
230	(*p)--;
231
232	if (unlikely(*p < - pcp->stat_threshold)) {
233		int overstep = pcp->stat_threshold / 2;
234
235		zone_page_state_add(*p - overstep, zone, item);
236		*p = overstep;
237	}
238}
239
240void __dec_zone_page_state(struct page *page, enum zone_stat_item item)
241{
242	__dec_zone_state(page_zone(page), item);
243}
244EXPORT_SYMBOL(__dec_zone_page_state);
245
246void inc_zone_state(struct zone *zone, enum zone_stat_item item)
247{
248	unsigned long flags;
249
250	local_irq_save(flags);
251	__inc_zone_state(zone, item);
252	local_irq_restore(flags);
253}
254
255void inc_zone_page_state(struct page *page, enum zone_stat_item item)
256{
257	unsigned long flags;
258	struct zone *zone;
259
260	zone = page_zone(page);
261	local_irq_save(flags);
262	__inc_zone_state(zone, item);
263	local_irq_restore(flags);
264}
265EXPORT_SYMBOL(inc_zone_page_state);
266
267void dec_zone_page_state(struct page *page, enum zone_stat_item item)
268{
269	unsigned long flags;
270
271	local_irq_save(flags);
272	__dec_zone_page_state(page, item);
273	local_irq_restore(flags);
274}
275EXPORT_SYMBOL(dec_zone_page_state);
276
277/*
278 * Update the zone counters for one cpu.
279 *
280 * The cpu specified must be either the current cpu or a processor that
281 * is not online. If it is the current cpu then the execution thread must
282 * be pinned to the current cpu.
283 *
284 * Note that refresh_cpu_vm_stats strives to only access
285 * node local memory. The per cpu pagesets on remote zones are placed
286 * in the memory local to the processor using that pageset. So the
287 * loop over all zones will access a series of cachelines local to
288 * the processor.
289 *
290 * The call to zone_page_state_add updates the cachelines with the
291 * statistics in the remote zone struct as well as the global cachelines
292 * with the global counters. These could cause remote node cache line
293 * bouncing and will have to be only done when necessary.
294 */
295void refresh_cpu_vm_stats(int cpu)
296{
297	struct zone *zone;
298	int i;
299	int global_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
300
301	for_each_zone(zone) {
302		struct per_cpu_pageset *p;
303
304		if (!populated_zone(zone))
305			continue;
306
307		p = zone_pcp(zone, cpu);
308
309		for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
310			if (p->vm_stat_diff[i]) {
311				unsigned long flags;
312				int v;
313
314				local_irq_save(flags);
315				v = p->vm_stat_diff[i];
316				p->vm_stat_diff[i] = 0;
317				local_irq_restore(flags);
318				atomic_long_add(v, &zone->vm_stat[i]);
319				global_diff[i] += v;
320#ifdef CONFIG_NUMA
321				/* 3 seconds idle till flush */
322				p->expire = 3;
323#endif
324			}
325		cond_resched();
326#ifdef CONFIG_NUMA
327		/*
328		 * Deal with draining the remote pageset of this
329		 * processor
330		 *
331		 * Check if there are pages remaining in this pageset
332		 * if not then there is nothing to expire.
333		 */
334		if (!p->expire || !p->pcp.count)
335			continue;
336
337		/*
338		 * We never drain zones local to this processor.
339		 */
340		if (zone_to_nid(zone) == numa_node_id()) {
341			p->expire = 0;
342			continue;
343		}
344
345		p->expire--;
346		if (p->expire)
347			continue;
348
349		if (p->pcp.count)
350			drain_zone_pages(zone, &p->pcp);
351#endif
352	}
353
354	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
355		if (global_diff[i])
356			atomic_long_add(global_diff[i], &vm_stat[i]);
357}
358
359#endif
360
361#ifdef CONFIG_NUMA
362/*
363 * zonelist = the list of zones passed to the allocator
364 * z 	    = the zone from which the allocation occurred.
365 *
366 * Must be called with interrupts disabled.
367 */
368void zone_statistics(struct zone *preferred_zone, struct zone *z)
369{
370	if (z->zone_pgdat == preferred_zone->zone_pgdat) {
371		__inc_zone_state(z, NUMA_HIT);
372	} else {
373		__inc_zone_state(z, NUMA_MISS);
374		__inc_zone_state(preferred_zone, NUMA_FOREIGN);
375	}
376	if (z->node == numa_node_id())
377		__inc_zone_state(z, NUMA_LOCAL);
378	else
379		__inc_zone_state(z, NUMA_OTHER);
380}
381#endif
382
383#ifdef CONFIG_PROC_FS
384
385#include <linux/seq_file.h>
386
387static char * const migratetype_names[MIGRATE_TYPES] = {
388	"Unmovable",
389	"Reclaimable",
390	"Movable",
391	"Reserve",
392	"Isolate",
393};
394
395static void *frag_start(struct seq_file *m, loff_t *pos)
396{
397	pg_data_t *pgdat;
398	loff_t node = *pos;
399	for (pgdat = first_online_pgdat();
400	     pgdat && node;
401	     pgdat = next_online_pgdat(pgdat))
402		--node;
403
404	return pgdat;
405}
406
407static void *frag_next(struct seq_file *m, void *arg, loff_t *pos)
408{
409	pg_data_t *pgdat = (pg_data_t *)arg;
410
411	(*pos)++;
412	return next_online_pgdat(pgdat);
413}
414
415static void frag_stop(struct seq_file *m, void *arg)
416{
417}
418
419/* Walk all the zones in a node and print using a callback */
420static void walk_zones_in_node(struct seq_file *m, pg_data_t *pgdat,
421		void (*print)(struct seq_file *m, pg_data_t *, struct zone *))
422{
423	struct zone *zone;
424	struct zone *node_zones = pgdat->node_zones;
425	unsigned long flags;
426
427	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
428		if (!populated_zone(zone))
429			continue;
430
431		spin_lock_irqsave(&zone->lock, flags);
432		print(m, pgdat, zone);
433		spin_unlock_irqrestore(&zone->lock, flags);
434	}
435}
436
437static void frag_show_print(struct seq_file *m, pg_data_t *pgdat,
438						struct zone *zone)
439{
440	int order;
441
442	seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
443	for (order = 0; order < MAX_ORDER; ++order)
444		seq_printf(m, "%6lu ", zone->free_area[order].nr_free);
445	seq_putc(m, '\n');
446}
447
448/*
449 * This walks the free areas for each zone.
450 */
451static int frag_show(struct seq_file *m, void *arg)
452{
453	pg_data_t *pgdat = (pg_data_t *)arg;
454	walk_zones_in_node(m, pgdat, frag_show_print);
455	return 0;
456}
457
458static void pagetypeinfo_showfree_print(struct seq_file *m,
459					pg_data_t *pgdat, struct zone *zone)
460{
461	int order, mtype;
462
463	for (mtype = 0; mtype < MIGRATE_TYPES; mtype++) {
464		seq_printf(m, "Node %4d, zone %8s, type %12s ",
465					pgdat->node_id,
466					zone->name,
467					migratetype_names[mtype]);
468		for (order = 0; order < MAX_ORDER; ++order) {
469			unsigned long freecount = 0;
470			struct free_area *area;
471			struct list_head *curr;
472
473			area = &(zone->free_area[order]);
474
475			list_for_each(curr, &area->free_list[mtype])
476				freecount++;
477			seq_printf(m, "%6lu ", freecount);
478		}
479		seq_putc(m, '\n');
480	}
481}
482
483/* Print out the free pages at each order for each migatetype */
484static int pagetypeinfo_showfree(struct seq_file *m, void *arg)
485{
486	int order;
487	pg_data_t *pgdat = (pg_data_t *)arg;
488
489	/* Print header */
490	seq_printf(m, "%-43s ", "Free pages count per migrate type at order");
491	for (order = 0; order < MAX_ORDER; ++order)
492		seq_printf(m, "%6d ", order);
493	seq_putc(m, '\n');
494
495	walk_zones_in_node(m, pgdat, pagetypeinfo_showfree_print);
496
497	return 0;
498}
499
500static void pagetypeinfo_showblockcount_print(struct seq_file *m,
501					pg_data_t *pgdat, struct zone *zone)
502{
503	int mtype;
504	unsigned long pfn;
505	unsigned long start_pfn = zone->zone_start_pfn;
506	unsigned long end_pfn = start_pfn + zone->spanned_pages;
507	unsigned long count[MIGRATE_TYPES] = { 0, };
508
509	for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
510		struct page *page;
511
512		if (!pfn_valid(pfn))
513			continue;
514
515		page = pfn_to_page(pfn);
516		mtype = get_pageblock_migratetype(page);
517
518		count[mtype]++;
519	}
520
521	/* Print counts */
522	seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
523	for (mtype = 0; mtype < MIGRATE_TYPES; mtype++)
524		seq_printf(m, "%12lu ", count[mtype]);
525	seq_putc(m, '\n');
526}
527
528/* Print out the free pages at each order for each migratetype */
529static int pagetypeinfo_showblockcount(struct seq_file *m, void *arg)
530{
531	int mtype;
532	pg_data_t *pgdat = (pg_data_t *)arg;
533
534	seq_printf(m, "\n%-23s", "Number of blocks type ");
535	for (mtype = 0; mtype < MIGRATE_TYPES; mtype++)
536		seq_printf(m, "%12s ", migratetype_names[mtype]);
537	seq_putc(m, '\n');
538	walk_zones_in_node(m, pgdat, pagetypeinfo_showblockcount_print);
539
540	return 0;
541}
542
543/*
544 * This prints out statistics in relation to grouping pages by mobility.
545 * It is expensive to collect so do not constantly read the file.
546 */
547static int pagetypeinfo_show(struct seq_file *m, void *arg)
548{
549	pg_data_t *pgdat = (pg_data_t *)arg;
550
551	seq_printf(m, "Page block order: %d\n", pageblock_order);
552	seq_printf(m, "Pages per block:  %lu\n", pageblock_nr_pages);
553	seq_putc(m, '\n');
554	pagetypeinfo_showfree(m, pgdat);
555	pagetypeinfo_showblockcount(m, pgdat);
556
557	return 0;
558}
559
560const struct seq_operations fragmentation_op = {
561	.start	= frag_start,
562	.next	= frag_next,
563	.stop	= frag_stop,
564	.show	= frag_show,
565};
566
567const struct seq_operations pagetypeinfo_op = {
568	.start	= frag_start,
569	.next	= frag_next,
570	.stop	= frag_stop,
571	.show	= pagetypeinfo_show,
572};
573
574#ifdef CONFIG_ZONE_DMA
575#define TEXT_FOR_DMA(xx) xx "_dma",
576#else
577#define TEXT_FOR_DMA(xx)
578#endif
579
580#ifdef CONFIG_ZONE_DMA32
581#define TEXT_FOR_DMA32(xx) xx "_dma32",
582#else
583#define TEXT_FOR_DMA32(xx)
584#endif
585
586#ifdef CONFIG_HIGHMEM
587#define TEXT_FOR_HIGHMEM(xx) xx "_high",
588#else
589#define TEXT_FOR_HIGHMEM(xx)
590#endif
591
592#define TEXTS_FOR_ZONES(xx) TEXT_FOR_DMA(xx) TEXT_FOR_DMA32(xx) xx "_normal", \
593					TEXT_FOR_HIGHMEM(xx) xx "_movable",
594
595static const char * const vmstat_text[] = {
596	/* Zoned VM counters */
597	"nr_free_pages",
598	"nr_inactive",
599	"nr_active",
600	"nr_anon_pages",
601	"nr_mapped",
602	"nr_file_pages",
603	"nr_dirty",
604	"nr_writeback",
605	"nr_slab_reclaimable",
606	"nr_slab_unreclaimable",
607	"nr_page_table_pages",
608	"nr_unstable",
609	"nr_bounce",
610	"nr_vmscan_write",
611
612#ifdef CONFIG_NUMA
613	"numa_hit",
614	"numa_miss",
615	"numa_foreign",
616	"numa_interleave",
617	"numa_local",
618	"numa_other",
619#endif
620
621#ifdef CONFIG_VM_EVENT_COUNTERS
622	"pgpgin",
623	"pgpgout",
624	"pswpin",
625	"pswpout",
626
627	TEXTS_FOR_ZONES("pgalloc")
628
629	"pgfree",
630	"pgactivate",
631	"pgdeactivate",
632
633	"pgfault",
634	"pgmajfault",
635
636	TEXTS_FOR_ZONES("pgrefill")
637	TEXTS_FOR_ZONES("pgsteal")
638	TEXTS_FOR_ZONES("pgscan_kswapd")
639	TEXTS_FOR_ZONES("pgscan_direct")
640
641	"pginodesteal",
642	"slabs_scanned",
643	"kswapd_steal",
644	"kswapd_inodesteal",
645	"pageoutrun",
646	"allocstall",
647
648	"pgrotated",
649#ifdef CONFIG_HUGETLB_PAGE
650	"htlb_buddy_alloc_success",
651	"htlb_buddy_alloc_fail",
652#endif
653#endif
654};
655
656static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
657							struct zone *zone)
658{
659	int i;
660	seq_printf(m, "Node %d, zone %8s", pgdat->node_id, zone->name);
661	seq_printf(m,
662		   "\n  pages free     %lu"
663		   "\n        min      %lu"
664		   "\n        low      %lu"
665		   "\n        high     %lu"
666		   "\n        scanned  %lu (a: %lu i: %lu)"
667		   "\n        spanned  %lu"
668		   "\n        present  %lu",
669		   zone_page_state(zone, NR_FREE_PAGES),
670		   zone->pages_min,
671		   zone->pages_low,
672		   zone->pages_high,
673		   zone->pages_scanned,
674		   zone->nr_scan_active, zone->nr_scan_inactive,
675		   zone->spanned_pages,
676		   zone->present_pages);
677
678	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
679		seq_printf(m, "\n    %-12s %lu", vmstat_text[i],
680				zone_page_state(zone, i));
681
682	seq_printf(m,
683		   "\n        protection: (%lu",
684		   zone->lowmem_reserve[0]);
685	for (i = 1; i < ARRAY_SIZE(zone->lowmem_reserve); i++)
686		seq_printf(m, ", %lu", zone->lowmem_reserve[i]);
687	seq_printf(m,
688		   ")"
689		   "\n  pagesets");
690	for_each_online_cpu(i) {
691		struct per_cpu_pageset *pageset;
692
693		pageset = zone_pcp(zone, i);
694		seq_printf(m,
695			   "\n    cpu: %i"
696			   "\n              count: %i"
697			   "\n              high:  %i"
698			   "\n              batch: %i",
699			   i,
700			   pageset->pcp.count,
701			   pageset->pcp.high,
702			   pageset->pcp.batch);
703#ifdef CONFIG_SMP
704		seq_printf(m, "\n  vm stats threshold: %d",
705				pageset->stat_threshold);
706#endif
707	}
708	seq_printf(m,
709		   "\n  all_unreclaimable: %u"
710		   "\n  prev_priority:     %i"
711		   "\n  start_pfn:         %lu",
712			   zone_is_all_unreclaimable(zone),
713		   zone->prev_priority,
714		   zone->zone_start_pfn);
715	seq_putc(m, '\n');
716}
717
718/*
719 * Output information about zones in @pgdat.
720 */
721static int zoneinfo_show(struct seq_file *m, void *arg)
722{
723	pg_data_t *pgdat = (pg_data_t *)arg;
724	walk_zones_in_node(m, pgdat, zoneinfo_show_print);
725	return 0;
726}
727
728const struct seq_operations zoneinfo_op = {
729	.start	= frag_start, /* iterate over all zones. The same as in
730			       * fragmentation. */
731	.next	= frag_next,
732	.stop	= frag_stop,
733	.show	= zoneinfo_show,
734};
735
736static void *vmstat_start(struct seq_file *m, loff_t *pos)
737{
738	unsigned long *v;
739#ifdef CONFIG_VM_EVENT_COUNTERS
740	unsigned long *e;
741#endif
742	int i;
743
744	if (*pos >= ARRAY_SIZE(vmstat_text))
745		return NULL;
746
747#ifdef CONFIG_VM_EVENT_COUNTERS
748	v = kmalloc(NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long)
749			+ sizeof(struct vm_event_state), GFP_KERNEL);
750#else
751	v = kmalloc(NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long),
752			GFP_KERNEL);
753#endif
754	m->private = v;
755	if (!v)
756		return ERR_PTR(-ENOMEM);
757	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
758		v[i] = global_page_state(i);
759#ifdef CONFIG_VM_EVENT_COUNTERS
760	e = v + NR_VM_ZONE_STAT_ITEMS;
761	all_vm_events(e);
762	e[PGPGIN] /= 2;		/* sectors -> kbytes */
763	e[PGPGOUT] /= 2;
764#endif
765	return v + *pos;
766}
767
768static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)
769{
770	(*pos)++;
771	if (*pos >= ARRAY_SIZE(vmstat_text))
772		return NULL;
773	return (unsigned long *)m->private + *pos;
774}
775
776static int vmstat_show(struct seq_file *m, void *arg)
777{
778	unsigned long *l = arg;
779	unsigned long off = l - (unsigned long *)m->private;
780
781	seq_printf(m, "%s %lu\n", vmstat_text[off], *l);
782	return 0;
783}
784
785static void vmstat_stop(struct seq_file *m, void *arg)
786{
787	kfree(m->private);
788	m->private = NULL;
789}
790
791const struct seq_operations vmstat_op = {
792	.start	= vmstat_start,
793	.next	= vmstat_next,
794	.stop	= vmstat_stop,
795	.show	= vmstat_show,
796};
797
798#endif /* CONFIG_PROC_FS */
799
800#ifdef CONFIG_SMP
801static DEFINE_PER_CPU(struct delayed_work, vmstat_work);
802int sysctl_stat_interval __read_mostly = HZ;
803
804static void vmstat_update(struct work_struct *w)
805{
806	refresh_cpu_vm_stats(smp_processor_id());
807	schedule_delayed_work(&__get_cpu_var(vmstat_work),
808		sysctl_stat_interval);
809}
810
811static void __cpuinit start_cpu_timer(int cpu)
812{
813	struct delayed_work *vmstat_work = &per_cpu(vmstat_work, cpu);
814
815	INIT_DELAYED_WORK_DEFERRABLE(vmstat_work, vmstat_update);
816	schedule_delayed_work_on(cpu, vmstat_work, HZ + cpu);
817}
818
819/*
820 * Use the cpu notifier to insure that the thresholds are recalculated
821 * when necessary.
822 */
823static int __cpuinit vmstat_cpuup_callback(struct notifier_block *nfb,
824		unsigned long action,
825		void *hcpu)
826{
827	long cpu = (long)hcpu;
828
829	switch (action) {
830	case CPU_ONLINE:
831	case CPU_ONLINE_FROZEN:
832		start_cpu_timer(cpu);
833		break;
834	case CPU_DOWN_PREPARE:
835	case CPU_DOWN_PREPARE_FROZEN:
836		cancel_rearming_delayed_work(&per_cpu(vmstat_work, cpu));
837		per_cpu(vmstat_work, cpu).work.func = NULL;
838		break;
839	case CPU_DOWN_FAILED:
840	case CPU_DOWN_FAILED_FROZEN:
841		start_cpu_timer(cpu);
842		break;
843	case CPU_DEAD:
844	case CPU_DEAD_FROZEN:
845		refresh_zone_stat_thresholds();
846		break;
847	default:
848		break;
849	}
850	return NOTIFY_OK;
851}
852
853static struct notifier_block __cpuinitdata vmstat_notifier =
854	{ &vmstat_cpuup_callback, NULL, 0 };
855
856static int __init setup_vmstat(void)
857{
858	int cpu;
859
860	refresh_zone_stat_thresholds();
861	register_cpu_notifier(&vmstat_notifier);
862
863	for_each_online_cpu(cpu)
864		start_cpu_timer(cpu);
865	return 0;
866}
867module_init(setup_vmstat)
868#endif
869