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perf sched: Show start of latency as well
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The 'perf sched latency' tool is really useful at showing worst-case
latencies that task encountered since wakeup. However it shows only the
end of the latency. Often times the start of a latency is interesting as
it can show what else was going on at the time to cause the latency. I
certainly myself spending a lot of time backtracking to the start of the
latency in "perf sched script" which wastes a lot of time.

This patch therefore adds a new column "Max delay start". Considering
this, also rename "Maximum delay at" to "Max delay end" as its easier to
understand.

Example of the new output:

  ----------------------------------------------------------------------------------------------------------------------------------
   Task                  | Runtime ms  | Switches | Avg delay ms  | Max delay ms   | Max delay start         | Max delay end       |
  ----------------------------------------------------------------------------------------------------------------------------------
   MediaScannerSer:11936 |  651.296 ms |    67978 | avg: 0.113 ms | max: 77.250 ms | max start: 477.691360 s | max end: 477.768610 s
   [email protected]:(3)   |    0.000 ms |     3440 | avg: 0.034 ms | max: 72.267 ms | max start: 477.697051 s | max end: 477.769318 s
   AudioOut_1D:8112      |    0.000 ms |     2588 | avg: 0.083 ms | max: 64.020 ms | max start: 477.710740 s | max end: 477.774760 s
   Time-limited te:14973 | 7966.090 ms |    24807 | avg: 0.073 ms | max: 15.563 ms | max start: 477.162746 s | max end: 477.178309 s
   surfaceflinger:8049   |    9.680 ms |      603 | avg: 0.063 ms | max: 13.275 ms | max start: 476.931791 s | max end: 476.945067 s
   HeapTaskDaemon:(3)    | 1588.830 ms |     7040 | avg: 0.065 ms | max:  6.880 ms | max start: 473.666043 s | max end: 473.672922 s
   mount-passthrou:(3)   | 1370.809 ms |    68904 | avg: 0.011 ms | max:  6.524 ms | max start: 478.090630 s | max end: 478.097154 s
   ReferenceQueueD:(3)   |   11.794 ms |     1725 | avg: 0.014 ms | max:  6.521 ms | max start: 476.119782 s | max end: 476.126303 s
   writer:14077          |   18.410 ms |     1427 | avg: 0.036 ms | max:  6.131 ms | max start: 474.169675 s | max end: 474.175805 s

Signed-off-by: Joel Fernandes (Google) <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
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@joelagnel @acmel
joelagnel authored and acmel committed Oct 13, 2020
1 parent 70830f9 commit dc000c4
Showing 1 changed file with 14 additions and 10 deletions.
24 changes: 14 additions & 10 deletions tools/perf/builtin-sched.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -130,7 +130,8 @@ struct work_atoms {
struct thread *thread;
struct rb_node node;
u64 max_lat;
u64 max_lat_at;
u64 max_lat_start;
u64 max_lat_end;
u64 total_lat;
u64 nb_atoms;
u64 total_runtime;
Expand Down Expand Up @@ -1096,7 +1097,8 @@ add_sched_in_event(struct work_atoms *atoms, u64 timestamp)
atoms->total_lat += delta;
if (delta > atoms->max_lat) {
atoms->max_lat = delta;
atoms->max_lat_at = timestamp;
atoms->max_lat_start = atom->wake_up_time;
atoms->max_lat_end = timestamp;
}
atoms->nb_atoms++;
}
Expand Down Expand Up @@ -1322,7 +1324,7 @@ static void output_lat_thread(struct perf_sched *sched, struct work_atoms *work_
int i;
int ret;
u64 avg;
char max_lat_at[32];
char max_lat_start[32], max_lat_end[32];

if (!work_list->nb_atoms)
return;
Expand All @@ -1344,13 +1346,14 @@ static void output_lat_thread(struct perf_sched *sched, struct work_atoms *work_
printf(" ");

avg = work_list->total_lat / work_list->nb_atoms;
timestamp__scnprintf_usec(work_list->max_lat_at, max_lat_at, sizeof(max_lat_at));
timestamp__scnprintf_usec(work_list->max_lat_start, max_lat_start, sizeof(max_lat_start));
timestamp__scnprintf_usec(work_list->max_lat_end, max_lat_end, sizeof(max_lat_end));

printf("|%11.3f ms |%9" PRIu64 " | avg:%9.3f ms | max:%9.3f ms | max at: %13s s\n",
printf("|%11.3f ms |%9" PRIu64 " | avg:%8.3f ms | max:%8.3f ms | max start: %12s s | max end: %12s s\n",
(double)work_list->total_runtime / NSEC_PER_MSEC,
work_list->nb_atoms, (double)avg / NSEC_PER_MSEC,
(double)work_list->max_lat / NSEC_PER_MSEC,
max_lat_at);
max_lat_start, max_lat_end);
}

static int pid_cmp(struct work_atoms *l, struct work_atoms *r)
Expand Down Expand Up @@ -3137,7 +3140,8 @@ static void __merge_work_atoms(struct rb_root_cached *root, struct work_atoms *d
list_splice(&data->work_list, &this->work_list);
if (this->max_lat < data->max_lat) {
this->max_lat = data->max_lat;
this->max_lat_at = data->max_lat_at;
this->max_lat_start = data->max_lat_start;
this->max_lat_end = data->max_lat_end;
}
zfree(&data);
return;
Expand Down Expand Up @@ -3176,9 +3180,9 @@ static int perf_sched__lat(struct perf_sched *sched)
perf_sched__merge_lat(sched);
perf_sched__sort_lat(sched);

printf("\n -----------------------------------------------------------------------------------------------------------------\n");
printf(" Task | Runtime ms | Switches | Average delay ms | Maximum delay ms | Maximum delay at |\n");
printf(" -----------------------------------------------------------------------------------------------------------------\n");
printf("\n -------------------------------------------------------------------------------------------------------------------------------------------\n");
printf(" Task | Runtime ms | Switches | Avg delay ms | Max delay ms | Max delay start | Max delay end |\n");
printf(" -------------------------------------------------------------------------------------------------------------------------------------------\n");

next = rb_first_cached(&sched->sorted_atom_root);

Expand Down

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