[PATCH v1 2/2] perf tests: Add test for stat delay option with duration_time

[Ian Rogers <irogers@google.com>]

Add a new test case `test_stat_delay` to `stat.sh` to verify that
`duration_time` correctly excludes the delay period when using the
delay option (-D).

The test runs `perf stat -D 1000 -e duration_time sleep 2` and
verifies that `duration_time` is ~1s (excluding the 1s delay), not
~2s.

Signed-off-by: Ian Rogers <irogers@google.com>
Assisted-by: Antigravity:gemini-3-flash
---
 tools/perf/tests/shell/stat.sh | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/tools/perf/tests/shell/stat.sh b/tools/perf/tests/shell/stat.sh
index 4edb04039036..e9a9b2c91cae 100755
--- a/tools/perf/tests/shell/stat.sh
+++ b/tools/perf/tests/shell/stat.sh
@@ -483,6 +483,38 @@ test_stat_pid() {
   wait $pid 2>/dev/null || true
 }
 
+test_stat_delay() {
+  echo "stat -D test"
+  if ! perf stat -D 1000 -e duration_time sleep 2 > "${stat_output}" 2>&1
+  then
+    echo "stat -D test [Failed - command failed]"
+    cat "${stat_output}"
+    err=1
+    return
+  fi
+
+  duration=$(grep "duration_time" "${stat_output}" | awk '{print $1}' | tr -d ',')
+  if [ -z "$duration" ]
+  then
+    echo "stat -D test [Failed - failed to find duration_time in output]"
+    cat "${stat_output}"
+    err=1
+    return
+  fi
+
+  # duration is in ns. We expect it to be ~1s (1,000,000,000 ns) because
+  # sleep 2 runs for 2s, and we delay by 1s, so measured window is 1s.
+  # If it includes delay, it will be > 2s (2,000,000,000 ns).
+  if [ "$duration" -gt 1500000000 ]
+  then
+    echo "stat -D test [Failed - duration_time ($duration ns) includes delay]"
+    cat "${stat_output}"
+    err=1
+    return
+  fi
+  echo "stat -D test [Success]"
+}
+
 test_default_stat
 test_null_stat
 test_offline_cpu_stat
@@ -498,6 +530,7 @@ test_stat_no_aggr
 test_stat_detailed
 test_stat_repeat
 test_stat_pid
+test_stat_delay
 
 cleanup
 exit $err
-- 
2.54.0.631.ge1b05301d1-goog