xref: /openbmc/linux/mm/vmstat.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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/module.h>
14 #include <linux/cpu.h>
15 
16 #ifdef CONFIG_VM_EVENT_COUNTERS
17 DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
18 EXPORT_PER_CPU_SYMBOL(vm_event_states);
19 
20 static void sum_vm_events(unsigned long *ret, cpumask_t *cpumask)
21 {
22 	int cpu = 0;
23 	int i;
24 
25 	memset(ret, 0, NR_VM_EVENT_ITEMS * sizeof(unsigned long));
26 
27 	cpu = first_cpu(*cpumask);
28 	while (cpu < NR_CPUS) {
29 		struct vm_event_state *this = &per_cpu(vm_event_states, cpu);
30 
31 		cpu = next_cpu(cpu, *cpumask);
32 
33 		if (cpu < NR_CPUS)
34 			prefetch(&per_cpu(vm_event_states, cpu));
35 
36 
37 		for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
38 			ret[i] += this->event[i];
39 	}
40 }
41 
42 /*
43  * Accumulate the vm event counters across all CPUs.
44  * The result is unavoidably approximate - it can change
45  * during and after execution of this function.
46 */
47 void all_vm_events(unsigned long *ret)
48 {
49 	sum_vm_events(ret, &cpu_online_map);
50 }
51 EXPORT_SYMBOL_GPL(all_vm_events);
52 
53 #ifdef CONFIG_HOTPLUG
54 /*
55  * Fold the foreign cpu events into our own.
56  *
57  * This is adding to the events on one processor
58  * but keeps the global counts constant.
59  */
60 void vm_events_fold_cpu(int cpu)
61 {
62 	struct vm_event_state *fold_state = &per_cpu(vm_event_states, cpu);
63 	int i;
64 
65 	for (i = 0; i < NR_VM_EVENT_ITEMS; i++) {
66 		count_vm_events(i, fold_state->event[i]);
67 		fold_state->event[i] = 0;
68 	}
69 }
70 #endif /* CONFIG_HOTPLUG */
71 
72 #endif /* CONFIG_VM_EVENT_COUNTERS */
73 
74 /*
75  * Manage combined zone based / global counters
76  *
77  * vm_stat contains the global counters
78  */
79 atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
80 EXPORT_SYMBOL(vm_stat);
81 
82 #ifdef CONFIG_SMP
83 
84 static int calculate_threshold(struct zone *zone)
85 {
86 	int threshold;
87 	int mem;	/* memory in 128 MB units */
88 
89 	/*
90 	 * The threshold scales with the number of processors and the amount
91 	 * of memory per zone. More memory means that we can defer updates for
92 	 * longer, more processors could lead to more contention.
93  	 * fls() is used to have a cheap way of logarithmic scaling.
94 	 *
95 	 * Some sample thresholds:
96 	 *
97 	 * Threshold	Processors	(fls)	Zonesize	fls(mem+1)
98 	 * ------------------------------------------------------------------
99 	 * 8		1		1	0.9-1 GB	4
100 	 * 16		2		2	0.9-1 GB	4
101 	 * 20 		2		2	1-2 GB		5
102 	 * 24		2		2	2-4 GB		6
103 	 * 28		2		2	4-8 GB		7
104 	 * 32		2		2	8-16 GB		8
105 	 * 4		2		2	<128M		1
106 	 * 30		4		3	2-4 GB		5
107 	 * 48		4		3	8-16 GB		8
108 	 * 32		8		4	1-2 GB		4
109 	 * 32		8		4	0.9-1GB		4
110 	 * 10		16		5	<128M		1
111 	 * 40		16		5	900M		4
112 	 * 70		64		7	2-4 GB		5
113 	 * 84		64		7	4-8 GB		6
114 	 * 108		512		9	4-8 GB		6
115 	 * 125		1024		10	8-16 GB		8
116 	 * 125		1024		10	16-32 GB	9
117 	 */
118 
119 	mem = zone->present_pages >> (27 - PAGE_SHIFT);
120 
121 	threshold = 2 * fls(num_online_cpus()) * (1 + fls(mem));
122 
123 	/*
124 	 * Maximum threshold is 125
125 	 */
126 	threshold = min(125, threshold);
127 
128 	return threshold;
129 }
130 
131 /*
132  * Refresh the thresholds for each zone.
133  */
134 static void refresh_zone_stat_thresholds(void)
135 {
136 	struct zone *zone;
137 	int cpu;
138 	int threshold;
139 
140 	for_each_zone(zone) {
141 
142 		if (!zone->present_pages)
143 			continue;
144 
145 		threshold = calculate_threshold(zone);
146 
147 		for_each_online_cpu(cpu)
148 			zone_pcp(zone, cpu)->stat_threshold = threshold;
149 	}
150 }
151 
152 /*
153  * For use when we know that interrupts are disabled.
154  */
155 void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
156 				int delta)
157 {
158 	struct per_cpu_pageset *pcp = zone_pcp(zone, smp_processor_id());
159 	s8 *p = pcp->vm_stat_diff + item;
160 	long x;
161 
162 	x = delta + *p;
163 
164 	if (unlikely(x > pcp->stat_threshold || x < -pcp->stat_threshold)) {
165 		zone_page_state_add(x, zone, item);
166 		x = 0;
167 	}
168 	*p = x;
169 }
170 EXPORT_SYMBOL(__mod_zone_page_state);
171 
172 /*
173  * For an unknown interrupt state
174  */
175 void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
176 					int delta)
177 {
178 	unsigned long flags;
179 
180 	local_irq_save(flags);
181 	__mod_zone_page_state(zone, item, delta);
182 	local_irq_restore(flags);
183 }
184 EXPORT_SYMBOL(mod_zone_page_state);
185 
186 /*
187  * Optimized increment and decrement functions.
188  *
189  * These are only for a single page and therefore can take a struct page *
190  * argument instead of struct zone *. This allows the inclusion of the code
191  * generated for page_zone(page) into the optimized functions.
192  *
193  * No overflow check is necessary and therefore the differential can be
194  * incremented or decremented in place which may allow the compilers to
195  * generate better code.
196  * The increment or decrement is known and therefore one boundary check can
197  * be omitted.
198  *
199  * NOTE: These functions are very performance sensitive. Change only
200  * with care.
201  *
202  * Some processors have inc/dec instructions that are atomic vs an interrupt.
203  * However, the code must first determine the differential location in a zone
204  * based on the processor number and then inc/dec the counter. There is no
205  * guarantee without disabling preemption that the processor will not change
206  * in between and therefore the atomicity vs. interrupt cannot be exploited
207  * in a useful way here.
208  */
209 void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
210 {
211 	struct per_cpu_pageset *pcp = zone_pcp(zone, smp_processor_id());
212 	s8 *p = pcp->vm_stat_diff + item;
213 
214 	(*p)++;
215 
216 	if (unlikely(*p > pcp->stat_threshold)) {
217 		int overstep = pcp->stat_threshold / 2;
218 
219 		zone_page_state_add(*p + overstep, zone, item);
220 		*p = -overstep;
221 	}
222 }
223 
224 void __inc_zone_page_state(struct page *page, enum zone_stat_item item)
225 {
226 	__inc_zone_state(page_zone(page), item);
227 }
228 EXPORT_SYMBOL(__inc_zone_page_state);
229 
230 void __dec_zone_state(struct zone *zone, enum zone_stat_item item)
231 {
232 	struct per_cpu_pageset *pcp = zone_pcp(zone, smp_processor_id());
233 	s8 *p = pcp->vm_stat_diff + item;
234 
235 	(*p)--;
236 
237 	if (unlikely(*p < - pcp->stat_threshold)) {
238 		int overstep = pcp->stat_threshold / 2;
239 
240 		zone_page_state_add(*p - overstep, zone, item);
241 		*p = overstep;
242 	}
243 }
244 
245 void __dec_zone_page_state(struct page *page, enum zone_stat_item item)
246 {
247 	__dec_zone_state(page_zone(page), item);
248 }
249 EXPORT_SYMBOL(__dec_zone_page_state);
250 
251 void inc_zone_state(struct zone *zone, enum zone_stat_item item)
252 {
253 	unsigned long flags;
254 
255 	local_irq_save(flags);
256 	__inc_zone_state(zone, item);
257 	local_irq_restore(flags);
258 }
259 
260 void inc_zone_page_state(struct page *page, enum zone_stat_item item)
261 {
262 	unsigned long flags;
263 	struct zone *zone;
264 
265 	zone = page_zone(page);
266 	local_irq_save(flags);
267 	__inc_zone_state(zone, item);
268 	local_irq_restore(flags);
269 }
270 EXPORT_SYMBOL(inc_zone_page_state);
271 
272 void dec_zone_page_state(struct page *page, enum zone_stat_item item)
273 {
274 	unsigned long flags;
275 
276 	local_irq_save(flags);
277 	__dec_zone_page_state(page, item);
278 	local_irq_restore(flags);
279 }
280 EXPORT_SYMBOL(dec_zone_page_state);
281 
282 /*
283  * Update the zone counters for one cpu.
284  *
285  * Note that refresh_cpu_vm_stats strives to only access
286  * node local memory. The per cpu pagesets on remote zones are placed
287  * in the memory local to the processor using that pageset. So the
288  * loop over all zones will access a series of cachelines local to
289  * the processor.
290  *
291  * The call to zone_page_state_add updates the cachelines with the
292  * statistics in the remote zone struct as well as the global cachelines
293  * with the global counters. These could cause remote node cache line
294  * bouncing and will have to be only done when necessary.
295  */
296 void refresh_cpu_vm_stats(int cpu)
297 {
298 	struct zone *zone;
299 	int i;
300 	unsigned long flags;
301 
302 	for_each_zone(zone) {
303 		struct per_cpu_pageset *p;
304 
305 		if (!populated_zone(zone))
306 			continue;
307 
308 		p = zone_pcp(zone, cpu);
309 
310 		for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
311 			if (p->vm_stat_diff[i]) {
312 				local_irq_save(flags);
313 				zone_page_state_add(p->vm_stat_diff[i],
314 					zone, i);
315 				p->vm_stat_diff[i] = 0;
316 #ifdef CONFIG_NUMA
317 				/* 3 seconds idle till flush */
318 				p->expire = 3;
319 #endif
320 				local_irq_restore(flags);
321 			}
322 #ifdef CONFIG_NUMA
323 		/*
324 		 * Deal with draining the remote pageset of this
325 		 * processor
326 		 *
327 		 * Check if there are pages remaining in this pageset
328 		 * if not then there is nothing to expire.
329 		 */
330 		if (!p->expire || (!p->pcp[0].count && !p->pcp[1].count))
331 			continue;
332 
333 		/*
334 		 * We never drain zones local to this processor.
335 		 */
336 		if (zone_to_nid(zone) == numa_node_id()) {
337 			p->expire = 0;
338 			continue;
339 		}
340 
341 		p->expire--;
342 		if (p->expire)
343 			continue;
344 
345 		if (p->pcp[0].count)
346 			drain_zone_pages(zone, p->pcp + 0);
347 
348 		if (p->pcp[1].count)
349 			drain_zone_pages(zone, p->pcp + 1);
350 #endif
351 	}
352 }
353 
354 static void __refresh_cpu_vm_stats(void *dummy)
355 {
356 	refresh_cpu_vm_stats(smp_processor_id());
357 }
358 
359 /*
360  * Consolidate all counters.
361  *
362  * Note that the result is less inaccurate but still inaccurate
363  * if concurrent processes are allowed to run.
364  */
365 void refresh_vm_stats(void)
366 {
367 	on_each_cpu(__refresh_cpu_vm_stats, NULL, 0, 1);
368 }
369 EXPORT_SYMBOL(refresh_vm_stats);
370 
371 #endif
372 
373 #ifdef CONFIG_NUMA
374 /*
375  * zonelist = the list of zones passed to the allocator
376  * z 	    = the zone from which the allocation occurred.
377  *
378  * Must be called with interrupts disabled.
379  */
380 void zone_statistics(struct zonelist *zonelist, struct zone *z)
381 {
382 	if (z->zone_pgdat == zonelist->zones[0]->zone_pgdat) {
383 		__inc_zone_state(z, NUMA_HIT);
384 	} else {
385 		__inc_zone_state(z, NUMA_MISS);
386 		__inc_zone_state(zonelist->zones[0], NUMA_FOREIGN);
387 	}
388 	if (z->node == numa_node_id())
389 		__inc_zone_state(z, NUMA_LOCAL);
390 	else
391 		__inc_zone_state(z, NUMA_OTHER);
392 }
393 #endif
394 
395 #ifdef CONFIG_PROC_FS
396 
397 #include <linux/seq_file.h>
398 
399 static void *frag_start(struct seq_file *m, loff_t *pos)
400 {
401 	pg_data_t *pgdat;
402 	loff_t node = *pos;
403 	for (pgdat = first_online_pgdat();
404 	     pgdat && node;
405 	     pgdat = next_online_pgdat(pgdat))
406 		--node;
407 
408 	return pgdat;
409 }
410 
411 static void *frag_next(struct seq_file *m, void *arg, loff_t *pos)
412 {
413 	pg_data_t *pgdat = (pg_data_t *)arg;
414 
415 	(*pos)++;
416 	return next_online_pgdat(pgdat);
417 }
418 
419 static void frag_stop(struct seq_file *m, void *arg)
420 {
421 }
422 
423 /*
424  * This walks the free areas for each zone.
425  */
426 static int frag_show(struct seq_file *m, void *arg)
427 {
428 	pg_data_t *pgdat = (pg_data_t *)arg;
429 	struct zone *zone;
430 	struct zone *node_zones = pgdat->node_zones;
431 	unsigned long flags;
432 	int order;
433 
434 	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
435 		if (!populated_zone(zone))
436 			continue;
437 
438 		spin_lock_irqsave(&zone->lock, flags);
439 		seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
440 		for (order = 0; order < MAX_ORDER; ++order)
441 			seq_printf(m, "%6lu ", zone->free_area[order].nr_free);
442 		spin_unlock_irqrestore(&zone->lock, flags);
443 		seq_putc(m, '\n');
444 	}
445 	return 0;
446 }
447 
448 const struct seq_operations fragmentation_op = {
449 	.start	= frag_start,
450 	.next	= frag_next,
451 	.stop	= frag_stop,
452 	.show	= frag_show,
453 };
454 
455 #ifdef CONFIG_ZONE_DMA
456 #define TEXT_FOR_DMA(xx) xx "_dma",
457 #else
458 #define TEXT_FOR_DMA(xx)
459 #endif
460 
461 #ifdef CONFIG_ZONE_DMA32
462 #define TEXT_FOR_DMA32(xx) xx "_dma32",
463 #else
464 #define TEXT_FOR_DMA32(xx)
465 #endif
466 
467 #ifdef CONFIG_HIGHMEM
468 #define TEXT_FOR_HIGHMEM(xx) xx "_high",
469 #else
470 #define TEXT_FOR_HIGHMEM(xx)
471 #endif
472 
473 #define TEXTS_FOR_ZONES(xx) TEXT_FOR_DMA(xx) TEXT_FOR_DMA32(xx) xx "_normal", \
474 					TEXT_FOR_HIGHMEM(xx)
475 
476 static const char * const vmstat_text[] = {
477 	/* Zoned VM counters */
478 	"nr_free_pages",
479 	"nr_active",
480 	"nr_inactive",
481 	"nr_anon_pages",
482 	"nr_mapped",
483 	"nr_file_pages",
484 	"nr_dirty",
485 	"nr_writeback",
486 	"nr_slab_reclaimable",
487 	"nr_slab_unreclaimable",
488 	"nr_page_table_pages",
489 	"nr_unstable",
490 	"nr_bounce",
491 	"nr_vmscan_write",
492 
493 #ifdef CONFIG_NUMA
494 	"numa_hit",
495 	"numa_miss",
496 	"numa_foreign",
497 	"numa_interleave",
498 	"numa_local",
499 	"numa_other",
500 #endif
501 
502 #ifdef CONFIG_VM_EVENT_COUNTERS
503 	"pgpgin",
504 	"pgpgout",
505 	"pswpin",
506 	"pswpout",
507 
508 	TEXTS_FOR_ZONES("pgalloc")
509 
510 	"pgfree",
511 	"pgactivate",
512 	"pgdeactivate",
513 
514 	"pgfault",
515 	"pgmajfault",
516 
517 	TEXTS_FOR_ZONES("pgrefill")
518 	TEXTS_FOR_ZONES("pgsteal")
519 	TEXTS_FOR_ZONES("pgscan_kswapd")
520 	TEXTS_FOR_ZONES("pgscan_direct")
521 
522 	"pginodesteal",
523 	"slabs_scanned",
524 	"kswapd_steal",
525 	"kswapd_inodesteal",
526 	"pageoutrun",
527 	"allocstall",
528 
529 	"pgrotated",
530 #endif
531 };
532 
533 /*
534  * Output information about zones in @pgdat.
535  */
536 static int zoneinfo_show(struct seq_file *m, void *arg)
537 {
538 	pg_data_t *pgdat = arg;
539 	struct zone *zone;
540 	struct zone *node_zones = pgdat->node_zones;
541 	unsigned long flags;
542 
543 	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; zone++) {
544 		int i;
545 
546 		if (!populated_zone(zone))
547 			continue;
548 
549 		spin_lock_irqsave(&zone->lock, flags);
550 		seq_printf(m, "Node %d, zone %8s", pgdat->node_id, zone->name);
551 		seq_printf(m,
552 			   "\n  pages free     %lu"
553 			   "\n        min      %lu"
554 			   "\n        low      %lu"
555 			   "\n        high     %lu"
556 			   "\n        scanned  %lu (a: %lu i: %lu)"
557 			   "\n        spanned  %lu"
558 			   "\n        present  %lu",
559 			   zone_page_state(zone, NR_FREE_PAGES),
560 			   zone->pages_min,
561 			   zone->pages_low,
562 			   zone->pages_high,
563 			   zone->pages_scanned,
564 			   zone->nr_scan_active, zone->nr_scan_inactive,
565 			   zone->spanned_pages,
566 			   zone->present_pages);
567 
568 		for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
569 			seq_printf(m, "\n    %-12s %lu", vmstat_text[i],
570 					zone_page_state(zone, i));
571 
572 		seq_printf(m,
573 			   "\n        protection: (%lu",
574 			   zone->lowmem_reserve[0]);
575 		for (i = 1; i < ARRAY_SIZE(zone->lowmem_reserve); i++)
576 			seq_printf(m, ", %lu", zone->lowmem_reserve[i]);
577 		seq_printf(m,
578 			   ")"
579 			   "\n  pagesets");
580 		for_each_online_cpu(i) {
581 			struct per_cpu_pageset *pageset;
582 			int j;
583 
584 			pageset = zone_pcp(zone, i);
585 			for (j = 0; j < ARRAY_SIZE(pageset->pcp); j++) {
586 				seq_printf(m,
587 					   "\n    cpu: %i pcp: %i"
588 					   "\n              count: %i"
589 					   "\n              high:  %i"
590 					   "\n              batch: %i",
591 					   i, j,
592 					   pageset->pcp[j].count,
593 					   pageset->pcp[j].high,
594 					   pageset->pcp[j].batch);
595 			}
596 #ifdef CONFIG_SMP
597 			seq_printf(m, "\n  vm stats threshold: %d",
598 					pageset->stat_threshold);
599 #endif
600 		}
601 		seq_printf(m,
602 			   "\n  all_unreclaimable: %u"
603 			   "\n  prev_priority:     %i"
604 			   "\n  start_pfn:         %lu",
605 			   zone->all_unreclaimable,
606 			   zone->prev_priority,
607 			   zone->zone_start_pfn);
608 		spin_unlock_irqrestore(&zone->lock, flags);
609 		seq_putc(m, '\n');
610 	}
611 	return 0;
612 }
613 
614 const struct seq_operations zoneinfo_op = {
615 	.start	= frag_start, /* iterate over all zones. The same as in
616 			       * fragmentation. */
617 	.next	= frag_next,
618 	.stop	= frag_stop,
619 	.show	= zoneinfo_show,
620 };
621 
622 static void *vmstat_start(struct seq_file *m, loff_t *pos)
623 {
624 	unsigned long *v;
625 #ifdef CONFIG_VM_EVENT_COUNTERS
626 	unsigned long *e;
627 #endif
628 	int i;
629 
630 	if (*pos >= ARRAY_SIZE(vmstat_text))
631 		return NULL;
632 
633 #ifdef CONFIG_VM_EVENT_COUNTERS
634 	v = kmalloc(NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long)
635 			+ sizeof(struct vm_event_state), GFP_KERNEL);
636 #else
637 	v = kmalloc(NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long),
638 			GFP_KERNEL);
639 #endif
640 	m->private = v;
641 	if (!v)
642 		return ERR_PTR(-ENOMEM);
643 	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
644 		v[i] = global_page_state(i);
645 #ifdef CONFIG_VM_EVENT_COUNTERS
646 	e = v + NR_VM_ZONE_STAT_ITEMS;
647 	all_vm_events(e);
648 	e[PGPGIN] /= 2;		/* sectors -> kbytes */
649 	e[PGPGOUT] /= 2;
650 #endif
651 	return v + *pos;
652 }
653 
654 static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)
655 {
656 	(*pos)++;
657 	if (*pos >= ARRAY_SIZE(vmstat_text))
658 		return NULL;
659 	return (unsigned long *)m->private + *pos;
660 }
661 
662 static int vmstat_show(struct seq_file *m, void *arg)
663 {
664 	unsigned long *l = arg;
665 	unsigned long off = l - (unsigned long *)m->private;
666 
667 	seq_printf(m, "%s %lu\n", vmstat_text[off], *l);
668 	return 0;
669 }
670 
671 static void vmstat_stop(struct seq_file *m, void *arg)
672 {
673 	kfree(m->private);
674 	m->private = NULL;
675 }
676 
677 const struct seq_operations vmstat_op = {
678 	.start	= vmstat_start,
679 	.next	= vmstat_next,
680 	.stop	= vmstat_stop,
681 	.show	= vmstat_show,
682 };
683 
684 #endif /* CONFIG_PROC_FS */
685 
686 #ifdef CONFIG_SMP
687 static DEFINE_PER_CPU(struct delayed_work, vmstat_work);
688 int sysctl_stat_interval __read_mostly = HZ;
689 
690 static void vmstat_update(struct work_struct *w)
691 {
692 	refresh_cpu_vm_stats(smp_processor_id());
693 	schedule_delayed_work(&__get_cpu_var(vmstat_work),
694 		sysctl_stat_interval);
695 }
696 
697 static void __devinit start_cpu_timer(int cpu)
698 {
699 	struct delayed_work *vmstat_work = &per_cpu(vmstat_work, cpu);
700 
701 	INIT_DELAYED_WORK_DEFERRABLE(vmstat_work, vmstat_update);
702 	schedule_delayed_work_on(cpu, vmstat_work, HZ + cpu);
703 }
704 
705 /*
706  * Use the cpu notifier to insure that the thresholds are recalculated
707  * when necessary.
708  */
709 static int __cpuinit vmstat_cpuup_callback(struct notifier_block *nfb,
710 		unsigned long action,
711 		void *hcpu)
712 {
713 	long cpu = (long)hcpu;
714 
715 	switch (action) {
716 	case CPU_ONLINE:
717 	case CPU_ONLINE_FROZEN:
718 		start_cpu_timer(cpu);
719 		break;
720 	case CPU_DOWN_PREPARE:
721 	case CPU_DOWN_PREPARE_FROZEN:
722 		cancel_rearming_delayed_work(&per_cpu(vmstat_work, cpu));
723 		per_cpu(vmstat_work, cpu).work.func = NULL;
724 		break;
725 	case CPU_DOWN_FAILED:
726 	case CPU_DOWN_FAILED_FROZEN:
727 		start_cpu_timer(cpu);
728 		break;
729 	case CPU_DEAD:
730 	case CPU_DEAD_FROZEN:
731 		refresh_zone_stat_thresholds();
732 		break;
733 	default:
734 		break;
735 	}
736 	return NOTIFY_OK;
737 }
738 
739 static struct notifier_block __cpuinitdata vmstat_notifier =
740 	{ &vmstat_cpuup_callback, NULL, 0 };
741 
742 int __init setup_vmstat(void)
743 {
744 	int cpu;
745 
746 	refresh_zone_stat_thresholds();
747 	register_cpu_notifier(&vmstat_notifier);
748 
749 	for_each_online_cpu(cpu)
750 		start_cpu_timer(cpu);
751 	return 0;
752 }
753 module_init(setup_vmstat)
754 #endif
755