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Commit 0eb77e98 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
Browse files

vmstat: make vmstat_updater deferrable again and shut down on idle 



Currently the vmstat updater is not deferrable as a result of commit
ba4877b9 ("vmstat: do not use deferrable delayed work for
vmstat_update").  This in turn can cause multiple interruptions of the
applications because the vmstat updater may run at

Make vmstate_update deferrable again and provide a function that folds
the differentials when the processor is going to idle mode thus
addressing the issue of the above commit in a clean way.

Note that the shepherd thread will continue scanning the differentials
from another processor and will reenable the vmstat workers if it
detects any changes.

Fixes: ba4877b9 ("vmstat: do not use deferrable delayed work for vmstat_update")
Signed-off-by: default avatarChristoph Lameter <cl@linux.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 686739f6

include/linux/vmstat.h

+2 −0
Original line number Diff line number Diff line
@@ -189,6 +189,7 @@ extern void __inc_zone_state(struct zone *, enum zone_stat_item); 
extern void dec_zone_state(struct zone *, enum zone_stat_item);

extern void __dec_zone_state(struct zone *, enum zone_stat_item);



void quiet_vmstat(void);

void cpu_vm_stats_fold(int cpu);

void refresh_zone_stat_thresholds(void);
@@ -249,6 +250,7 @@ static inline void __dec_zone_page_state(struct page *page, 


static inline void refresh_zone_stat_thresholds(void) { }

static inline void cpu_vm_stats_fold(int cpu) { }

static inline void quiet_vmstat(void) { }



static inline void drain_zonestat(struct zone *zone,

			struct per_cpu_pageset *pset) { }

kernel/sched/idle.c

+1 −0
Original line number Diff line number Diff line
@@ -219,6 +219,7 @@ static void cpu_idle_loop(void) 
		 */



		__current_set_polling();

		quiet_vmstat();

		tick_nohz_idle_enter();



		while (!need_resched()) {

mm/vmstat.c

+44 −25
Original line number Diff line number Diff line
@@ -460,7 +460,7 @@ static int fold_diff(int *diff) 
 *

 * The function returns the number of global counters updated.

 */

static int refresh_cpu_vm_stats(void)

static int refresh_cpu_vm_stats(bool do_pagesets)

{

	struct zone *zone;

	int i;
@@ -484,8 +484,9 @@ static int refresh_cpu_vm_stats(void) 
#endif

			}

		}

		cond_resched();

#ifdef CONFIG_NUMA

		if (do_pagesets) {

			cond_resched();

			/*

			 * Deal with draining the remote pageset of this

			 * processor
@@ -512,6 +513,7 @@ static int refresh_cpu_vm_stats(void) 
				drain_zone_pages(zone, this_cpu_ptr(&p->pcp));

				changes++;

			}

		}

#endif

	}

	changes += fold_diff(global_diff);
@@ -1386,7 +1388,7 @@ static cpumask_var_t cpu_stat_off; 


static void vmstat_update(struct work_struct *w)

{

	if (refresh_cpu_vm_stats()) {

	if (refresh_cpu_vm_stats(true)) {

		/*

		 * Counters were updated so we expect more updates

		 * to occur in the future. Keep on running the
@@ -1417,6 +1419,23 @@ static void vmstat_update(struct work_struct *w) 
	}

}



/*

 * Switch off vmstat processing and then fold all the remaining differentials

 * until the diffs stay at zero. The function is used by NOHZ and can only be

 * invoked when tick processing is not active.

 */

void quiet_vmstat(void)

{

	if (system_state != SYSTEM_RUNNING)

		return;



	do {

		if (!cpumask_test_and_set_cpu(smp_processor_id(), cpu_stat_off))

			cancel_delayed_work(this_cpu_ptr(&vmstat_work));



	} while (refresh_cpu_vm_stats(false));

}



/*

 * Check if the diffs for a certain cpu indicate that

 * an update is needed.
@@ -1449,7 +1468,7 @@ static bool need_update(int cpu) 
 */

static void vmstat_shepherd(struct work_struct *w);



static DECLARE_DELAYED_WORK(shepherd, vmstat_shepherd);

static DECLARE_DEFERRABLE_WORK(shepherd, vmstat_shepherd);



static void vmstat_shepherd(struct work_struct *w)

{