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Subject[PATCH V14 3/4] powerpc/hotplug: Improve responsiveness of hotplug change
Date
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>
---
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;
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