perf sched latency 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. Signed-off-by: Joel Fernandes (Google) <[email protected]> --- A sample output can be seen after applying patch: https://hastebin.com/raw/ivinimaler tools/perf/builtin-sched.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c index 459e4229945e..2791da1fe5f7 100644 --- a/tools/perf/builtin-sched.c +++ b/tools/perf/builtin-sched.c @@ -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; @@ -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++; } @@ -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; @@ -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) @@ -3118,7 +3121,8 @@ 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; @@ -3157,9 +3161,9 @@ 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); -- 2.28.0.709.gb0816b6eb0-goog
