linux-kernel - [PATCH V14 3/4] powerpc/hotplug: Improve responsiveness of hotplug change

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Message-Id: <b09a89f6-325d-c1ef-07da-427e60e641cf@linux.vnet.ibm.com>
Date:   Fri, 8 Sep 2017 15:47:47 -0500
From:   Michael Bringmann <mwb@...ux.vnet.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:     Michael Bringmann <mwb@...ux.vnet.ibm.com>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        John Allen <jallen@...ux.vnet.ibm.com>
Subject: [PATCH V14 3/4] 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@...ux.vnet.ibm.com>
---
Changes in V14:
  -- Restore accidentally deleted reset of topology timer.
---
 arch/powerpc/include/asm/topology.h          |    8 ++++++++
 arch/powerpc/mm/numa.c                       |   23 ++++++++++++++++++++++-
 arch/powerpc/platforms/pseries/hotplug-cpu.c |    2 ++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h
index dc4e159..beb9bca 100644
--- a/arch/powerpc/include/asm/topology.h
+++ b/arch/powerpc/include/asm/topology.h
@@ -98,6 +98,14 @@ 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
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 5f5ff46..32f5f8d 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -1148,15 +1148,35 @@ 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 void topology_timer_fn(unsigned long ignored)
 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);
 }
 
diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index 6afd1ef..5a7fb1e 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -356,6 +356,7 @@ 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;
@@ -522,6 +523,7 @@ 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;