--- mm/mmzone.c

+++ mm/mmzone.c

@@ -87,3 +87,24 @@ int memmap_valid_within(unsigned long pf

return 1;

}

#endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */

+

+#ifdef CONFIG_SMP

+/* Called when a more accurate view of NR_FREE_PAGES is needed */

+unsigned long zone_nr_free_pages(struct zone *zone)

+{

+ unsigned long nr_free_pages = zone_page_state(zone, NR_FREE_PAGES);

+

+ /*

+ * While kswapd is awake, it is considered the zone is under some

+ * memory pressure. Under pressure, there is a risk that

+ * per-cpu-counter-drift will allow the min watermark to be breached

+ * potentially causing a live-lock. While kswapd is awake and

+ * free pages are low, get a better estimate for free pages

+ */

+ if (nr_free_pages < zone->percpu_drift_mark &&

+ !waitqueue_active(&zone->zone_pgdat->kswapd_wait))

+ return zone_page_state_snapshot(zone, NR_FREE_PAGES);

+

+ return nr_free_pages;

+}

+#endif /* CONFIG_SMP */