sched/numa: Modify migrate_swap() to accept additional parameters

There are checks in migrate_swap_stop() that check if the task/CPU combination is as per migrate_swap_arg before migrating. However atleast one of the two tasks to be swapped by migrate_swap() could have migrated to a completely different CPU before updating the migrate_swap_arg. The new CPU where the task is currently running could be a different node too. If the task has migrated, numa balancer might end up placing a task in a wrong node. Instead of achieving node consolidation, it may end up spreading the load across nodes. To avoid that pass the CPUs as additional parameters. While here, place migrate_swap under CONFIG_NUMA_BALANCING. Running SPECjbb2005 on a 4 node machine and comparing bops/JVM JVMS LAST_PATCH WITH_PATCH %CHANGE 16 25377.3 25226.6 -0.59 1 72287 73326 1.437 Signed-off-by: Srikar Dronamraju <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Reviewed-by: Rik van Riel <[email protected]> Acked-by: Mel Gorman <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
devinus · Jul 25, 2018 · 0ad4e3d · 0ad4e3d
1 parent 10864a9
commit 0ad4e3d
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Showing 3 changed files with 10 additions and 5 deletions.
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
@@ -1176,6 +1176,7 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
 	__set_task_cpu(p, new_cpu);
 }
 
+#ifdef CONFIG_NUMA_BALANCING
 static void __migrate_swap_task(struct task_struct *p, int cpu)
 {
 	if (task_on_rq_queued(p)) {
@@ -1257,16 +1258,17 @@ static int migrate_swap_stop(void *data)
 /*
  * Cross migrate two tasks
  */
-int migrate_swap(struct task_struct *cur, struct task_struct *p)
+int migrate_swap(struct task_struct *cur, struct task_struct *p,
+		int target_cpu, int curr_cpu)
 {
 	struct migration_swap_arg arg;
 	int ret = -EINVAL;
 
 	arg = (struct migration_swap_arg){
 		.src_task = cur,
-		.src_cpu = task_cpu(cur),
+		.src_cpu = curr_cpu,
 		.dst_task = p,
-		.dst_cpu = task_cpu(p),
+		.dst_cpu = target_cpu,
 	};
 
 	if (arg.src_cpu == arg.dst_cpu)
@@ -1291,6 +1293,7 @@ int migrate_swap(struct task_struct *cur, struct task_struct *p)
 out:
 	return ret;
 }
+#endif /* CONFIG_NUMA_BALANCING */
 
 /*
  * wait_task_inactive - wait for a thread to unschedule.

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
@@ -1848,7 +1848,8 @@ static int task_numa_migrate(struct task_struct *p)
 		return ret;
 	}
 
-	ret = migrate_swap(p, env.best_task);
+	ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
+
 	if (ret != 0)
 		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
 	put_task_struct(env.best_task);

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
@@ -1099,7 +1099,8 @@ enum numa_faults_stats {
 };
 extern void sched_setnuma(struct task_struct *p, int node);
 extern int migrate_task_to(struct task_struct *p, int cpu);
-extern int migrate_swap(struct task_struct *, struct task_struct *);
+extern int migrate_swap(struct task_struct *p, struct task_struct *t,
+			int cpu, int scpu);
 extern void init_numa_balancing(unsigned long clone_flags, struct task_struct *p);
 #else
 static inline void