powerpc/hotplug: Improve responsiveness of hotplug change

powerpc/hotplug: On Power systems with shared configurations of CPUs
and memory, there are some issues with the association of additional
CPUs and memory to nodes when hot-adding resources.  During hotplug
CPU operations, this patch resets the timer on topology update work
function to a small value to better ensure that the CPU topology is
detected and configured sooner.
Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/topology.h

@@ -96,6 +96,14 @@ static inline int prrn_is_enabled(void)
 }
 #endif /* CONFIG_NUMA && CONFIG_PPC_SPLPAR */
 
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_NEED_MULTIPLE_NODES)
+#if defined(CONFIG_PPC_SPLPAR)
+extern int timed_topology_update(int nsecs);
+#else
+#define	timed_topology_update(nsecs)
+#endif /* CONFIG_PPC_SPLPAR */
+#endif /* CONFIG_HOTPLUG_CPU || CONFIG_NEED_MULTIPLE_NODES */
+
 #include <asm-generic/topology.h>
 
 #ifdef CONFIG_SMP

arch/powerpc/mm/numa.c

@@ -1148,14 +1148,34 @@ struct topology_update_data {
 	int new_nid;
 };
 
+#define TOPOLOGY_DEF_TIMER_SECS	60
+
 static u8 vphn_cpu_change_counts[NR_CPUS][MAX_DISTANCE_REF_POINTS];
 static cpumask_t cpu_associativity_changes_mask;
 static int vphn_enabled;
 static int prrn_enabled;
 static void reset_topology_timer(void);
+static int topology_timer_secs = 1;
 static int topology_inited;
 static int topology_update_needed;
 
+/*
+ * Change polling interval for associativity changes.
+ */
+int timed_topology_update(int nsecs)
+{
+	if (vphn_enabled) {
+		if (nsecs > 0)
+			topology_timer_secs = nsecs;
+		else
+			topology_timer_secs = TOPOLOGY_DEF_TIMER_SECS;
+
+		reset_topology_timer();
+	}
+
+	return 0;
+}
+
 /*
  * Store the current values of the associativity change counters in the
  * hypervisor.
@@ -1251,6 +1271,7 @@ static long vphn_get_associativity(unsigned long cpu,
 		break;
 	case H_SUCCESS:
 		dbg("VPHN hcall succeeded. Reset polling...\n");
+		timed_topology_update(0);
 		break;
 	}
 
@@ -1481,7 +1502,7 @@ static struct timer_list topology_timer =
 static void reset_topology_timer(void)
 {
 	topology_timer.data = 0;
-	topology_timer.expires = jiffies + 60 * HZ;
+	topology_timer.expires = jiffies + topology_timer_secs * HZ;
 	mod_timer(&topology_timer, topology_timer.expires);
 }
 

arch/powerpc/platforms/pseries/hotplug-cpu.c

@@ -363,6 +363,7 @@ static int dlpar_online_cpu(struct device_node *dn)
 			BUG_ON(get_cpu_current_state(cpu)
 					!= CPU_STATE_OFFLINE);
 			cpu_maps_update_done();
+			timed_topology_update(1);
 			rc = device_online(get_cpu_device(cpu));
 			if (rc)
 				goto out;
@@ -533,6 +534,7 @@ static int dlpar_offline_cpu(struct device_node *dn)
 				set_preferred_offline_state(cpu,
 							    CPU_STATE_OFFLINE);
 				cpu_maps_update_done();
+				timed_topology_update(1);
 				rc = device_offline(get_cpu_device(cpu));
 				if (rc)
 					goto out;