On Sun, 05 Feb 2012 14:48:41 +0100, Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx> wrote:
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d2186ec..3ff5aff 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1161,11 +1161,46 @@ void drain_local_pages(void *arg)
}
/*
- * Spill all the per-cpu pages from all CPUs back into the buddy allocator
+ * Spill all the per-cpu pages from all CPUs back into the buddy allocator.
+ *
+ * Note that this code is protected against sending an IPI to an offline
+ * CPU but does not guarantee sending an IPI to newly hotplugged CPUs:
+ * on_each_cpu_mask() blocks hotplug and won't talk to offlined CPUs but
+ * nothing keeps CPUs from showing up after we populated the cpumask and
+ * before the call to on_each_cpu_mask().
*/
void drain_all_pages(void)
{
- on_each_cpu(drain_local_pages, NULL, 1);
+ int cpu;
+ struct per_cpu_pageset *pcp;
+ struct zone *zone;
+
+ /* Allocate in the BSS so we wont require allocation in
+ * direct reclaim path for CONFIG_CPUMASK_OFFSTACK=y
+ */
If you are going to send next iteration, this comment should have
“/*” on its own line just like comment below.
+ static cpumask_t cpus_with_pcps;
+
+ /*
+ * We don't care about racing with CPU hotplug event
+ * as offline notification will cause the notified
+ * cpu to drain that CPU pcps and on_each_cpu_mask
+ * disables preemption as part of its processing
+ */
+ for_each_online_cpu(cpu) {
+ bool has_pcps = false;
+ for_each_populated_zone(zone) {
+ pcp = per_cpu_ptr(zone->pageset, cpu);
+ if (pcp->pcp.count) {
+ has_pcps = true;
+ break;
+ }
+ }
+ if (has_pcps)
+ cpumask_set_cpu(cpu, &cpus_with_pcps);
+ else
+ cpumask_clear_cpu(cpu, &cpus_with_pcps);
+ }
+ on_each_cpu_mask(&cpus_with_pcps, drain_local_pages, NULL, 1);
}
#ifdef CONFIG_HIBERNATION
--
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.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
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