perf sched latency: Add histogram and time interval options

While 'perf sched latency' reports task runtime and delay statistics
(average and maximum delay), it does not provide a visual representation
of how task wait times are distributed across latency ranges between
snapshots (start and finish of the analysis window).

The --histogram option collects CPU wait latencies (time between when
a task becomes runnable and when it gets scheduled onto a CPU) into 22
latency buckets, displaying an ASCII bar chart distribution.

The --hist-mode option configures the bucketing scheme:
  - log (default). Logarithmic latency buckets ranging from
    sub-microsecond (< 1 us) up to >= 1.05 seconds

  - linear. Equal-width linear latency buckets
    (i.e., 100 us steps up to >= 2.1 ms)

The --time option allows filtering trace event processing to a
specific time interval [start,stop].

Example histogram output excerpt:

    ❯ sudo perf sched latency --histogram --CPU 0

     CPU Wait Latency Distribution Histogram (between snapshots) (total samples: 36114)
     -------------------------------------------------------------------
      Latency Range    |      Count |    Pct | Histogram Graph
     -------------------------------------------------------------------
      < 1 us           |         17 |   0.0% | #
      2 - 4 us         |        673 |   1.9% | #
      4 - 8 us         |       6237 |  17.3% | ######
      8 - 16 us        |       3224 |   8.9% | ###
      16 - 32 us       |       1388 |   3.8% | #
      32 - 64 us       |        709 |   2.0% | #
      64 - 128 us      |        690 |   1.9% | #
      128 - 256 us     |        789 |   2.2% | #
      256 - 512 us     |        541 |   1.5% | #
      512 - 1024 us    |       2256 |   6.2% | ##
      1 - 2 ms         |       3577 |   9.9% | ###
      2 - 4 ms         |      13259 |  36.7% | ##############
      4 - 8 ms         |       2523 |   7.0% | ##
      8 - 16 ms        |        222 |   0.6% | #
      16 - 32 ms       |         10 |   0.0% | #
      >= 1.05 s        |          3 |   0.0% | #
     -------------------------------------------------------------------

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/tools/perf/tests/shell/sched.sh b/tools/perf/tests/shell/sched.sh
index b9637069adb1..113df962a51c 100755
--- a/tools/perf/tests/shell/sched.sh
+++ b/tools/perf/tests/shell/sched.sh
@@ -76,6 +76,32 @@ test_sched_latency() {
   fi
 }
 
+test_sched_latency_histogram() {
+  echo "Sched latency histogram"
+
+  if ! perf sched latency -H -i "${perfdata}" | grep -q "Latency Distribution Histogram"
+  then
+    echo "Sched latency histogram [Failed missing log histogram]"
+    err=1
+  fi
+
+  if ! perf sched latency --histogram --hist-mode linear -i "${perfdata}" | grep -q "Latency Distribution Histogram"
+  then
+    echo "Sched latency histogram [Failed missing linear histogram]"
+    err=1
+  fi
+}
+
+test_sched_latency_time() {
+  echo "Sched latency time filter"
+
+  if ! perf sched latency --time 0, -i "${perfdata}" | grep -q perf-noploop
+  then
+    echo "Sched latency time filter [Failed missing output]"
+    err=1
+  fi
+}
+
 test_sched_script() {
   echo "Sched script"
 
@@ -108,9 +134,12 @@ test_sched_timehist() {
 
 test_sched_record
 test_sched_latency
+test_sched_latency_histogram
+test_sched_latency_time
 test_sched_script
 test_sched_map
 test_sched_timehist
 
 cleanup
 exit $err
+