[PATCH v3] perf test: Allow tolerance for leader sampling test

[Thomas Richter <tmricht@linux.ibm.com>]

V3: Added check for missing samples as suggested by Chun-Tse.
V2: Changed bc invocation to return 0 on success and 1 on error.

There is a known issue that the leader sampling is inconsistent, since
throttle only affect leader, not the slave. The detail is in [1]. To
maintain test coverage, this patch sets a tolerance rate of 80% to
accommodate the throttled samples and prevent test failures due to
throttling.

[1] lore.kernel.org/20250328182752.769662-1-ctshao@google.com

Signed-off-by: Chun-Tse Shao <ctshao@google.com>
Suggested-by: Ian Rogers <irogers@google.com>
Suggested-by: Thomas Richter <tmricht@linux.ibm.com>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
---
 tools/perf/tests/shell/record.sh | 33 ++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
index ba8d873d3ca7..0075ffe783ad 100755
--- a/tools/perf/tests/shell/record.sh
+++ b/tools/perf/tests/shell/record.sh
@@ -238,22 +238,43 @@ test_leader_sampling() {
     err=1
     return
   fi
+  perf script -i "${perfdata}" | grep brstack > $script_output
+  # Check if the two instruction counts are equal in each record.
+  # However, the throttling code doesn't consider event grouping. During throttling, only the
+  # leader is stopped, causing the slave's counts significantly higher. To temporarily solve this,
+  # let's set the tolerance rate to 80%.
+  # TODO: Revert the code for tolerance once the throttling mechanism is fixed.
   index=0
-  perf script -i "${perfdata}" > $script_output
+  valid_counts=0
+  invalid_counts=0
+  tolerance_rate=0.8
   while IFS= read -r line
   do
-    # Check if the two instruction counts are equal in each record
     cycles=$(echo $line | awk '{for(i=1;i<=NF;i++) if($i=="cycles:") print $(i-1)}')
     if [ $(($index%2)) -ne 0 ] && [ ${cycles}x != ${prev_cycles}x ]
     then
-      echo "Leader sampling [Failed inconsistent cycles count]"
-      err=1
-      return
+      invalid_counts=$(($invalid_counts+1))
+    else
+      valid_counts=$(($valid_counts+1))
     fi
     index=$(($index+1))
     prev_cycles=$cycles
   done < $script_output
-  echo "Basic leader sampling test [Success]"
+  total_counts=$(bc <<< "$invalid_counts+$valid_counts")
+  if (( $(bc <<< "$total_counts <= 0") ))
+  then
+    echo "Leader sampling [No sample generated]"
+    err=1
+    return
+  fi
+  isok=$(bc <<< "scale=2; if (($invalid_counts/$total_counts) < (1-$tolerance_rate)) { 0 } else { 1 };")
+  if [ $isok -eq 1 ]
+  then
+     echo "Leader sampling [Failed inconsistent cycles count]"
+     err=1
+  else
+    echo "Basic leader sampling test [Success]"
+  fi
 }
 
 test_topdown_leader_sampling() {
-- 
2.49.0