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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>
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@ -6085,33 +6085,18 @@ void free_contig_range(unsigned long pfn, unsigned nr_pages)
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#endif
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#ifdef CONFIG_MEMORY_HOTPLUG
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static int __meminit __zone_pcp_update(void *data)
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{
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struct zone *zone = data;
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int cpu;
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unsigned long batch = zone_batchsize(zone), flags;
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for_each_possible_cpu(cpu) {
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struct per_cpu_pageset *pset;
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struct per_cpu_pages *pcp;
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pset = per_cpu_ptr(zone->pageset, cpu);
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pcp = &pset->pcp;
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local_irq_save(flags);
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if (pcp->count > 0)
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free_pcppages_bulk(zone, pcp->count, pcp);
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drain_zonestat(zone, pset);
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setup_pageset(pset, batch);
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local_irq_restore(flags);
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}
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return 0;
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}
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/*
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* The zone indicated has a new number of managed_pages; batch sizes and percpu
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* page high values need to be recalulated.
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*/
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void __meminit zone_pcp_update(struct zone *zone)
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{
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unsigned cpu;
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unsigned long batch;
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mutex_lock(&pcp_batch_high_lock);
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stop_machine(__zone_pcp_update, zone, NULL);
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batch = zone_batchsize(zone);
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for_each_possible_cpu(cpu)
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pageset_set_batch(per_cpu_ptr(zone->pageset, cpu), batch);
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mutex_unlock(&pcp_batch_high_lock);
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}
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#endif
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