mm: implement page cache reclaim in circles

index 61cedfc..d7f866e 100644
@@ -140,6 +140,7 @@ unsigned long vm_cache_limit_mbytes_max;
 unsigned long vm_cache_reclaim_s __read_mostly;
 unsigned long vm_cache_reclaim_s_min;
 
+static DEFINE_PER_CPU(struct delayed_work, vmscan_work);
 static LIST_HEAD(shrinker_list);
 static DECLARE_RWSEM(shrinker_rwsem);
 

@@ -3384,8 +3385,23 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
 }
 #endif /* CONFIG_HIBERNATION */
 
+static void shrink_page_cache_work(struct work_struct *w)
+{
+	struct delayed_work *work = to_delayed_work(w);
+
+	if (vm_cache_reclaim_s == 0) {
+		schedule_delayed_work(work, round_jiffies_relative(120 * HZ));
+		return;
+	}
+
+	shrink_page_cache(GFP_KERNEL);
+	schedule_delayed_work(work, round_jiffies_relative(vm_cache_reclaim_s * HZ));
+}
+
 static void shrink_page_cache_init(void)
 {
+	int cpu;
+
 	vm_cache_limit_ratio = 0;
 	vm_cache_limit_ratio_min = 0;
 	vm_cache_limit_ratio_max = 100;

@@ -3394,6 +3410,13 @@ static void shrink_page_cache_init(void)
 	vm_cache_limit_mbytes_max = totalram_pages;
 	vm_cache_reclaim_s = 0;
 	vm_cache_reclaim_s_min = 0;
+
+	for_each_online_cpu(cpu) {
+		struct delayed_work *work = &per_cpu(vmscan_work, cpu);
+		INIT_DEFERRABLE_WORK(work, shrink_page_cache_work);
+		schedule_delayed_work_on(cpu, work,
+			__round_jiffies_relative(vm_cache_reclaim_s * HZ, cpu));
+	}
 }
 
 static unsigned long __shrink_page_cache(gfp_t mask)

@@ -3428,6 +3451,8 @@ static int cpu_callback(struct notifier_block *nfb, unsigned long action,
 			void *hcpu)
 {
 	int nid;
+	long cpu = (long)hcpu;
+	struct delayed_work *work = &per_cpu(vmscan_work, cpu);
 
 	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
 		for_each_node_state(nid, N_MEMORY) {

@@ -3441,6 +3466,22 @@ static int cpu_callback(struct notifier_block *nfb, unsigned long action,
 				set_cpus_allowed_ptr(pgdat->kswapd, mask);
 		}
 	}
+
+	switch (action) {
+	case CPU_ONLINE:
+		if (work->work.func == NULL)
+			INIT_DEFERRABLE_WORK(work, shrink_page_cache_work);
+		schedule_delayed_work_on(cpu, work,
+			__round_jiffies_relative(vm_cache_reclaim_s * HZ, cpu));
+		break;
+	case CPU_DOWN_PREPARE:
+		cancel_delayed_work_sync(work);
+		work->work.func = NULL;
+		break;
+	default:
+		break;
+	}
+
 	return NOTIFY_OK;
 }