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Commit c8a37751 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

perf sched: Sanity check context switch events 



Use 'perf sched latency' to track the current task based on
context-switch events, and flag the cases where there's some
impossible transition: such as a PID being switched out that
was not switched in.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent dc02bf71

tools/perf/builtin-sched.c

+26 −1
Original line number Original line Diff line number Diff line
@@ -119,6 +119,7 @@ static unsigned long replay_repeat = 10; 
static unsigned long		nr_timestamps;

static unsigned long		nr_timestamps;

static unsigned long		nr_unordered_timestamps;

static unsigned long		nr_unordered_timestamps;

static unsigned long		nr_state_machine_bugs;

static unsigned long		nr_state_machine_bugs;

static unsigned long		nr_context_switch_bugs;

static unsigned long		nr_events;

static unsigned long		nr_events;

static unsigned long		nr_lost_chunks;

static unsigned long		nr_lost_chunks;

static unsigned long		nr_lost_events;

static unsigned long		nr_lost_events;
@@ -1399,6 +1400,14 @@ static void __cmd_lat(void) 
			printf(" (due to lost events?)");

			printf(" (due to lost events?)");

		printf("\n");

		printf("\n");

	}

	}

	if (nr_context_switch_bugs && nr_timestamps) {

		printf("  INFO: %.3f%% context switch bugs (%ld out of %ld)",

			(double)nr_context_switch_bugs/(double)nr_timestamps*100.0,

			nr_context_switch_bugs, nr_timestamps);

		if (nr_lost_events)

			printf(" (due to lost events?)");

		printf("\n");

	}

	printf("\n");

	printf("\n");





}

}
@@ -1425,10 +1434,16 @@ process_sched_wakeup_event(struct raw_event_sample *raw, 
	trace_handler->wakeup_event(&wakeup_event, event, cpu, timestamp, thread);

	trace_handler->wakeup_event(&wakeup_event, event, cpu, timestamp, thread);

}

}





/*

 * Track the current task - that way we can know whether there's any

 * weird events, such as a task being switched away that is not current.

 */

static u32 curr_pid[MAX_CPUS] = { [0 ... MAX_CPUS-1] = -1 };



static void

static void

process_sched_switch_event(struct raw_event_sample *raw,

process_sched_switch_event(struct raw_event_sample *raw,

			   struct event *event,

			   struct event *event,

			   int cpu __used,

			   int cpu,

			   u64 timestamp __used,

			   u64 timestamp __used,

			   struct thread *thread __used)

			   struct thread *thread __used)

{

{
@@ -1444,6 +1459,16 @@ process_sched_switch_event(struct raw_event_sample *raw, 
	FILL_FIELD(switch_event, next_pid, event, raw->data);

	FILL_FIELD(switch_event, next_pid, event, raw->data);

	FILL_FIELD(switch_event, next_prio, event, raw->data);

	FILL_FIELD(switch_event, next_prio, event, raw->data);





	if (curr_pid[cpu] != (u32)-1) {

		/*

		 * Are we trying to switch away a PID that is

		 * not current?

		 */

		if (curr_pid[cpu] != switch_event.prev_pid)

			nr_context_switch_bugs++;

	}

	curr_pid[cpu] = switch_event.next_pid;



	trace_handler->switch_event(&switch_event, event, cpu, timestamp, thread);

	trace_handler->switch_event(&switch_event, event, cpu, timestamp, thread);

}

}