From d0adb706159ea1103dbbea4b38e1974fa3e796bc Mon Sep 17 00:00:00 2001 From: Cody P Schafer Date: Thu, 23 May 2013 10:37:12 +1000 Subject: [PATCH] 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 Cc: Gilad Ben-Yossef Cc: KOSAKI Motohiro Cc: Mel Gorman Cc: Pekka Enberg Signed-off-by: Andrew Morton --- mm/page_alloc.c | 33 +++++++++------------------------ 1 file changed, 9 insertions(+), 24 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 97b8f861e63d..8125263be60f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -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 -- 2.39.5