Re: [PATCH v8 7/8] mm: only IPI CPUs to drain local pages if they exist
From: Michal Nazarewicz <hidden>
Date: 2012-02-08 09:33:13
Also in:
linux-fsdevel, lkml
On Sun, 05 Feb 2012 14:48:41 +0100, Gilad Ben-Yossef [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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-- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +----<email/xmpp: mpn@google.com>--------------ooO--(_)--Ooo-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>