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| author | Ingo Molnar <mingo@elte.hu> | 2009-09-16 14:07:00 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-09-16 12:08:28 +0200 |
| commit | c8a37751043427c6e4397a2cbfd617cb5f215c72 (patch) | |
| tree | b4399844d7064741c4df4098509b7dc3bd7d3493 /tools | |
| parent | dc02bf7178c8e2cb3d442ae19027b736d51c7dd5 (diff) | |
| download | lwn-c8a37751043427c6e4397a2cbfd617cb5f215c72.tar.gz lwn-c8a37751043427c6e4397a2cbfd617cb5f215c72.zip | |
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: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/perf/builtin-sched.c | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c index 1f0f9be34faa..2d542368de3c 100644 --- a/tools/perf/builtin-sched.c +++ b/tools/perf/builtin-sched.c @@ -119,6 +119,7 @@ static unsigned long replay_repeat = 10; static unsigned long nr_timestamps; static unsigned long nr_unordered_timestamps; static unsigned long nr_state_machine_bugs; +static unsigned long nr_context_switch_bugs; static unsigned long nr_events; static unsigned long nr_lost_chunks; static unsigned long nr_lost_events; @@ -1399,6 +1400,14 @@ static void __cmd_lat(void) printf(" (due to lost events?)"); 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"); } @@ -1425,10 +1434,16 @@ process_sched_wakeup_event(struct raw_event_sample *raw, 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 process_sched_switch_event(struct raw_event_sample *raw, struct event *event, - int cpu __used, + int cpu, u64 timestamp __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_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); } |