+static int zone_highsize(struct zone *zone, int batch, int cpu_online)
+{
+#ifdef CONFIG_MMU
+ int high;
+ int nr_split_cpus;
+ unsigned long total_pages;
+
+ if (!percpu_pagelist_high_fraction) {
+ /*
+ * By default, the high value of the pcp is based on the zone
+ * low watermark so that if they are full then background
+ * reclaim will not be started prematurely.
+ */
+ total_pages = low_wmark_pages(zone);
+ } else {
+ /*
+ * If percpu_pagelist_high_fraction is configured, the high
+ * value is based on a fraction of the managed pages in the
+ * zone.
+ */
+ total_pages = zone_managed_pages(zone) / percpu_pagelist_high_fraction;
+ }
+
+ /*
+ * Split the high value across all online CPUs local to the zone. Note
+ * that early in boot that CPUs may not be online yet and that during
+ * CPU hotplug that the cpumask is not yet updated when a CPU is being
+ * onlined. For memory nodes that have no CPUs, split pcp->high across
+ * all online CPUs to mitigate the risk that reclaim is triggered
+ * prematurely due to pages stored on pcp lists.
+ */
+ nr_split_cpus = cpumask_weight(cpumask_of_node(zone_to_nid(zone))) + cpu_online;
+ if (!nr_split_cpus)
+ nr_split_cpus = num_online_cpus();
+ high = total_pages / nr_split_cpus;
+
+ /*
+ * Ensure high is at least batch*4. The multiple is based on the
+ * historical relationship between high and batch.
+ */
+ high = max(high, batch << 2);
+
+ return high;
+#else
+ return 0;
+#endif
+}
+