[POWERPC] spufs: try to route SPU interrupts to local node

Currently, we re-route SPU interrupts to the current cpu, which may be
on a remote node. In the case of time slicing, all spu interrupts will
end up routed to the same cpu, where the spusched_tick occurs.

This change routes mfc interrupts to the cpu where the controlling
thread last ran, provided that cpu is on the same node as the spu
(otherwise don't reroute interrupts).

This should improve performance and provide a more predictable
environment for processing spu exceptions. In the past we have seen
concurrent delivery of spu exceptions to two cpus. This eliminates that
concern.

Signed-off-by: Luke Browning <lukebr@linux.vnet.ibm.com>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

arch/powerpc/platforms/cell/spu_priv1_mmio.c

@@ -28,6 +28,7 @@
 #include <linux/io.h>
 #include <linux/mutex.h>
 #include <linux/device.h>
+#include <linux/sched.h>
 
 #include <asm/spu.h>
 #include <asm/spu_priv1.h>
@@ -75,8 +76,19 @@ static u64 int_stat_get(struct spu *spu, int class)
 
 static void cpu_affinity_set(struct spu *spu, int cpu)
 {
-	u64 target = iic_get_target_id(cpu);
-	u64 route = target << 48 | target << 32 | target << 16;
+	u64 target;
+	u64 route;
+
+	if (nr_cpus_node(spu->node)) {
+		cpumask_t spumask = node_to_cpumask(spu->node);
+		cpumask_t cpumask = node_to_cpumask(cpu_to_node(cpu));
+
+		if (!cpus_intersects(spumask, cpumask))
+			return;
+	}
+
+	target = iic_get_target_id(cpu);
+	route = target << 48 | target << 32 | target << 16;
 	out_be64(&spu->priv1->int_route_RW, route);
 }
 

arch/powerpc/platforms/cell/spufs/sched.c

@@ -140,6 +140,9 @@ void __spu_update_sched_info(struct spu_context *ctx)
 	 * if it is timesliced or preempted.
 	 */
 	ctx->cpus_allowed = current->cpus_allowed;
+
+	/* Save the current cpu id for spu interrupt routing. */
+	ctx->last_ran = raw_smp_processor_id();
 }
 
 void spu_update_sched_info(struct spu_context *ctx)
@@ -243,7 +246,6 @@ static void spu_bind_context(struct spu *spu, struct spu_context *ctx)
 	spu_switch_log_notify(spu, ctx, SWITCH_LOG_START, 0);
 	spu_restore(&ctx->csa, spu);
 	spu->timestamp = jiffies;
-	spu_cpu_affinity_set(spu, raw_smp_processor_id());
 	spu_switch_notify(spu, ctx);
 	ctx->state = SPU_STATE_RUNNABLE;
 

arch/powerpc/platforms/cell/spufs/spufs.h

@@ -121,6 +121,7 @@ struct spu_context {
 	cpumask_t cpus_allowed;
 	int policy;
 	int prio;
+	int last_ran;
 
 	/* statistics */
 	struct {

arch/powerpc/platforms/cell/spufs/switch.c

@@ -1704,6 +1704,13 @@ static inline void restore_mfc_sr1(struct spu_state *csa, struct spu *spu)
 	eieio();
 }
 
+static inline void set_int_route(struct spu_state *csa, struct spu *spu)
+{
+	struct spu_context *ctx = spu->ctx;
+
+	spu_cpu_affinity_set(spu, ctx->last_ran);
+}
+
 static inline void restore_other_spu_access(struct spu_state *csa,
 					    struct spu *spu)
 {
@@ -2014,6 +2021,7 @@ static void restore_csa(struct spu_state *next, struct spu *spu)
 	check_ppuint_mb_stat(next, spu);	/* Step 67. */
 	spu_invalidate_slbs(spu);		/* Modified Step 68. */
 	restore_mfc_sr1(next, spu);	        /* Step 69. */
+	set_int_route(next, spu);		/* NEW      */
 	restore_other_spu_access(next, spu);	/* Step 70. */
 	restore_spu_runcntl(next, spu);	        /* Step 71. */
 	restore_mfc_cntl(next, spu);	        /* Step 72. */