linux-kernel - [PATCH v2] perf test: Allow tolerance for leader sampling test

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Message-ID: <20250409231230.1678358-1-ctshao@google.com>
Date: Wed,  9 Apr 2025 16:12:08 -0700
From: Chun-Tse Shao <ctshao@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: Chun-Tse Shao <ctshao@...gle.com>, Ian Rogers <irogers@...gle.com>, 
	Thomas Richter <tmricht@...ux.ibm.com>, peterz@...radead.org, mingo@...hat.com, 
	acme@...nel.org, namhyung@...nel.org, mark.rutland@....com, 
	alexander.shishkin@...ux.intel.com, jolsa@...nel.org, adrian.hunter@...el.com, 
	kan.liang@...ux.intel.com, james.clark@...aro.org, dapeng1.mi@...ux.intel.com, 
	vmolnaro@...hat.com, linux-perf-users@...r.kernel.org
Subject: [PATCH v2] perf test: Allow tolerance for leader sampling test

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@...gle.com

Signed-off-by: Chun-Tse Shao <ctshao@...gle.com>
Suggested-by: Ian Rogers <irogers@...gle.com>
Suggested-by: Thomas Richter <tmricht@...ux.ibm.com>
Tested-by: Thomas Richter <tmricht@...ux.ibm.com>
---
 tools/perf/tests/shell/record.sh | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
index ba8d873d3ca7..06a718e80121 100755
--- a/tools/perf/tests/shell/record.sh
+++ b/tools/perf/tests/shell/record.sh
@@ -240,19 +240,39 @@ test_leader_sampling() {
   fi
   index=0
   perf script -i "${perfdata}" > $script_output
+  # Check if the two instruction counts are equal in each record.
+  # However, the throttling code doesn't consider event grouping. During throttling, only the
+  # leader is stopped, causing the slave's counts significantly higher. To temporarily solve this,
+  # let's set the tolerance rate to 80%.
+  # TODO: Revert the code for tolerance once the throttling mechanism is fixed.
+  valid_counts=0
+  invalid_counts=0
+  tolerance_rate=0.8
   while IFS= read -r line
   do
-    # Check if the two instruction counts are equal in each record
     cycles=$(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 < $script_output
+  total_counts=$(bc <<< "$invalid_counts+$valid_counts")
+  if (( $(bc <<< "$total_counts <= 0") ))
+  then
+      echo "Leader sampling [No sample generated]"
+      err=1
+      return
+  fi
+  if (( $(bc <<< "scale=3; $invalid_counts/$total_counts > 1-$tolerance_rate") ))
+  then
+      echo "Leader sampling [Failed inconsistent cycles count]"
+      err=1
+      return
+  fi
   echo "Basic leader sampling test [Success]"
 }

--
2.49.0.504.g3bcea36a83-goog