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mm/page_alloc: convert zone_pcp_update() to rely on memory barriers instead of stop_machine() 

zone_pcp_update()'s goal is to adjust the ->high and ->mark members of a
percpu pageset based on a zone's ->managed_pages.  We don't need to drain
the entire percpu pageset just to modify these fields.

This lets us avoid calling setup_pageset() (and the draining required to
call it) and instead allows simply setting the fields' values (with some
attention paid to memory barriers to prevent the relationship between
->batch and ->high from being thrown off).

This does change the behavior of zone_pcp_update() as the percpu pagesets
will not be drained when zone_pcp_update() is called (they will end up
being shrunk, not completely drained, later when a 0-order page is freed
in free_hot_cold_page()).

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Cody P Schafer 2013-07-03 15:01:33 -07:00 committed by Linus Torvalds
parent 998d39cb23
commit 0a647f3811
1 changed files with 9 additions and 24 deletions
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33
mm/page_alloc.c
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@ -6085,33 +6085,18 @@ void free_contig_range(unsigned long pfn, unsigned nr_pages)
#endif
#ifdef CONFIG_MEMORY_HOTPLUG
static int __meminit __zone_pcp_update(void *data)
{
struct zone *zone = data;
int cpu;
unsigned long batch = zone_batchsize(zone), flags;
for_each_possible_cpu(cpu) {
struct per_cpu_pageset *pset;
struct per_cpu_pages *pcp;
pset = per_cpu_ptr(zone->pageset, cpu);
pcp = &pset->pcp;
local_irq_save(flags);
if (pcp->count > 0)
free_pcppages_bulk(zone, pcp->count, pcp);
drain_zonestat(zone, pset);
setup_pageset(pset, batch);
local_irq_restore(flags);
}
return 0;
}
/*
* The zone indicated has a new number of managed_pages; batch sizes and percpu
* page high values need to be recalulated.
*/
void __meminit zone_pcp_update(struct zone *zone)
{
unsigned cpu;
unsigned long batch;
mutex_lock(&pcp_batch_high_lock);
stop_machine(__zone_pcp_update, zone, NULL);
batch = zone_batchsize(zone);
for_each_possible_cpu(cpu)
pageset_set_batch(per_cpu_ptr(zone->pageset, cpu), batch);
mutex_unlock(&pcp_batch_high_lock);
}
#endif