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Commit 286549dc authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
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sched: add tracepoints related to NUMA task migration 



This patch adds three tracepoints
 o trace_sched_move_numa	when a task is moved to a node
 o trace_sched_swap_numa	when a task is swapped with another task
 o trace_sched_stick_numa	when a numa-related migration fails

The tracepoints allow the NUMA scheduler activity to be monitored and the
following high-level metrics can be calculated

 o NUMA migrated stuck	 nr trace_sched_stick_numa
 o NUMA migrated idle	 nr trace_sched_move_numa
 o NUMA migrated swapped nr trace_sched_swap_numa
 o NUMA local swapped	 trace_sched_swap_numa src_nid == dst_nid (should never happen)
 o NUMA remote swapped	 trace_sched_swap_numa src_nid != dst_nid (should == NUMA migrated swapped)
 o NUMA group swapped	 trace_sched_swap_numa src_ngid == dst_ngid
			 Maybe a small number of these are acceptable
			 but a high number would be a major surprise.
			 It would be even worse if bounces are frequent.
 o NUMA avg task migs.	 Average number of migrations for tasks
 o NUMA stddev task mig	 Self-explanatory
 o NUMA max task migs.	 Maximum number of migrations for a single task

In general the intent of the tracepoints is to help diagnose problems
where automatic NUMA balancing appears to be doing an excessive amount
of useless work.

[akpm@linux-foundation.org: remove semicolon-after-if, repair coding-style]
Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 64a9a34e

include/trace/events/sched.h

+87 −0
Original line number Diff line number Diff line
@@ -443,6 +443,93 @@ TRACE_EVENT(sched_process_hang, 
);

#endif /* CONFIG_DETECT_HUNG_TASK */



DECLARE_EVENT_CLASS(sched_move_task_template,



	TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),



	TP_ARGS(tsk, src_cpu, dst_cpu),



	TP_STRUCT__entry(

		__field( pid_t,	pid			)

		__field( pid_t,	tgid			)

		__field( pid_t,	ngid			)

		__field( int,	src_cpu			)

		__field( int,	src_nid			)

		__field( int,	dst_cpu			)

		__field( int,	dst_nid			)

	),



	TP_fast_assign(

		__entry->pid		= task_pid_nr(tsk);

		__entry->tgid		= task_tgid_nr(tsk);

		__entry->ngid		= task_numa_group_id(tsk);

		__entry->src_cpu	= src_cpu;

		__entry->src_nid	= cpu_to_node(src_cpu);

		__entry->dst_cpu	= dst_cpu;

		__entry->dst_nid	= cpu_to_node(dst_cpu);

	),



	TP_printk("pid=%d tgid=%d ngid=%d src_cpu=%d src_nid=%d dst_cpu=%d dst_nid=%d",

			__entry->pid, __entry->tgid, __entry->ngid,

			__entry->src_cpu, __entry->src_nid,

			__entry->dst_cpu, __entry->dst_nid)

);



/*

 * Tracks migration of tasks from one runqueue to another. Can be used to

 * detect if automatic NUMA balancing is bouncing between nodes

 */

DEFINE_EVENT(sched_move_task_template, sched_move_numa,

	TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),



	TP_ARGS(tsk, src_cpu, dst_cpu)

);



DEFINE_EVENT(sched_move_task_template, sched_stick_numa,

	TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),



	TP_ARGS(tsk, src_cpu, dst_cpu)

);



TRACE_EVENT(sched_swap_numa,



	TP_PROTO(struct task_struct *src_tsk, int src_cpu,

		 struct task_struct *dst_tsk, int dst_cpu),



	TP_ARGS(src_tsk, src_cpu, dst_tsk, dst_cpu),



	TP_STRUCT__entry(

		__field( pid_t,	src_pid			)

		__field( pid_t,	src_tgid		)

		__field( pid_t,	src_ngid		)

		__field( int,	src_cpu			)

		__field( int,	src_nid			)

		__field( pid_t,	dst_pid			)

		__field( pid_t,	dst_tgid		)

		__field( pid_t,	dst_ngid		)

		__field( int,	dst_cpu			)

		__field( int,	dst_nid			)

	),



	TP_fast_assign(

		__entry->src_pid	= task_pid_nr(src_tsk);

		__entry->src_tgid	= task_tgid_nr(src_tsk);

		__entry->src_ngid	= task_numa_group_id(src_tsk);

		__entry->src_cpu	= src_cpu;

		__entry->src_nid	= cpu_to_node(src_cpu);

		__entry->dst_pid	= task_pid_nr(dst_tsk);

		__entry->dst_tgid	= task_tgid_nr(dst_tsk);

		__entry->dst_ngid	= task_numa_group_id(dst_tsk);

		__entry->dst_cpu	= dst_cpu;

		__entry->dst_nid	= cpu_to_node(dst_cpu);

	),



	TP_printk("src_pid=%d src_tgid=%d src_ngid=%d src_cpu=%d src_nid=%d dst_pid=%d dst_tgid=%d dst_ngid=%d dst_cpu=%d dst_nid=%d",

			__entry->src_pid, __entry->src_tgid, __entry->src_ngid,

			__entry->src_cpu, __entry->src_nid,

			__entry->dst_pid, __entry->dst_tgid, __entry->dst_ngid,

			__entry->dst_cpu, __entry->dst_nid)

);

#endif /* _TRACE_SCHED_H */



/* This part must be outside protection */

kernel/sched/core.c

+2 −0
Original line number Diff line number Diff line
@@ -1108,6 +1108,7 @@ int migrate_swap(struct task_struct *cur, struct task_struct *p) 
	if (!cpumask_test_cpu(arg.src_cpu, tsk_cpus_allowed(arg.dst_task)))

		goto out;



	trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);

	ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);



out:
@@ -4603,6 +4604,7 @@ int migrate_task_to(struct task_struct *p, int target_cpu) 


	/* TODO: This is not properly updating schedstats */



	trace_sched_move_numa(p, curr_cpu, target_cpu);

	return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);

}

kernel/sched/fair.c

+5 −1
Original line number Diff line number Diff line
@@ -1250,11 +1250,15 @@ static int task_numa_migrate(struct task_struct *p) 
	p->numa_scan_period = task_scan_min(p);



	if (env.best_task == NULL) {

		int ret = migrate_task_to(p, env.best_cpu);

		ret = migrate_task_to(p, env.best_cpu);

		if (ret != 0)

			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);

		return ret;

	}



	ret = migrate_swap(p, env.best_task);

	if (ret != 0)

		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));

	put_task_struct(env.best_task);

	return ret;

}